From The University of Texas-Dallas : “Physicists Shine Light on Solid Way To Extend Excitons’ Life”

From The University of Texas-Dallas

June 17, 2022
Stephen Fontenot,
UT Dallas,
972-883-4405
stephen.fontenot@utdallas.edu,

Dr. Anton Malko’s Optics and Ultrafast Spectroscopy Laboratory focuses on the science and engineering of excitonic processes in various novel nanomaterials and hybrid structures. Malko and fellow researchers tested ultrathin semiconductors made with a method called laser-assisted synthesis technique in a recent study.

Optics researchers at The University of Texas at Dallas have shown for the first time that a new method for manufacturing ultrathin semiconductors yields material in which excitons survive up to 100 times longer than in materials created with previous methods.

The findings show that excitons, quasiparticles that transport energy, last long enough for a broad range of potential applications, including as bits in quantum computing devices.

Dr. Anton Malko, professor of physics in the School of Natural Sciences and Mathematics, is corresponding author of a paper published online March 30 in Advanced Materials that describes tests on ultrathin semiconductors made with a recently developed method called laser-assisted synthesis technique (LAST). The findings show novel quantum physics at work.

Semiconductors are a class of crystalline solids whose electrical conductivity is between that of a conductor and an insulator. This conductivity can be externally controlled, either by doping or electrical gating, making them key elements for the diodes and transistors that underpin all modern electronic technology.

Two-dimensional transition metal dichalcogenides (TMDs) are a novel type of ultrathin semiconductor consisting of a transition metal and a chalcogen element arranged in one atomic layer. While TMDs have been explored for a decade or so, the 2D form that Malko examined has advantages in scalability and optoelectronic properties.

“LAST is a very pure method. You take pure molybdenum or tungsten, and pure selenium or sulfur, and evaporate them under intense laser light,” Malko said. “Those atoms are distributed onto a substrate and make the two-dimensional TMD layer less than 1 nanometer thick.”

A material’s optical properties are partially determined by the behavior of excitons, which are quasiparticles that can transport energy while remaining electrically neutral.

“When a semiconductor absorbs a photon, it creates in the semiconductor a negatively charged electron paired with a positive hole, to maintain neutral charge. This pair is the exciton. The two parts are not completely free from each other — they still have a Coulomb interaction between them,” Malko said.

Malko and his team were surprised to discover that excitons in LAST-produced TMDs lasted up to 100 times longer than those in other TMD materials.

“We quickly found that, optically speaking, these 2D samples behave totally differently from any we’ve seen in 10 years working with TMDs,” he said. “When we started to look deeper at it, we realized it’s not a fluke; it’s repeatable and dependent on growth conditions.”

These longer lifetimes, Malko believes, are caused by indirect excitons, which are optically inactive.

“These excitons are used as a kind of reservoir to slowly feed the optically active excitons,” he said.

Lead study author Dr. Navendu Mondal, a former UT Dallas postdoctoral researcher who is now a Marie Skłodowska-Curie Individual Fellow at Imperial College London, said he believes the indirect excitons exist due to the abnormal amount of strain between the monolayer TMD material and the substrate on which it grows.

“Strain-controlling in atomically thin monolayer of TMDs is an important tool to tailor their optoelectronic properties,” Mondal said. “Their electronic band-structure is highly sensitive to structural deformations. Under enough strain, band-gap modifications cause formation of various indirect ‘dark’ excitons that are optically inactive. Through this finding, we reveal how the presence of these hidden dark excitons influences those excitons created directly by photons.”

Malko said the built-in strain in 2D TMDs is comparable to what would be induced by pressing on the material with externally placed micro- or nanosize pillars, although it is not a viable technological option for such thin layers.

“That strain is crucial for creating these optically inactive, indirect excitons,” he said. “If you remove the substrate, the strain is released, and this wonderful optical response is gone.”

Malko said the indirect excitons can be both electronically controlled and converted into photons opening a path to the development of new optoelectronic devices.

“This increased lifespan has very interesting potential applications,” he said. “When an exciton has a lifespan of only about 100 picoseconds or less, there is no time to use it. But in this material, we can create a reservoir of inactive excitons that live much longer — a few nanoseconds instead of hundreds of picoseconds. You can do a lot with this.”

Malko said the results of the research are an important proof-of-concept for future quantum-scale devices.

“It’s the first time we know of that anyone has made this fundamental observation of such long-living excitations in TMD materials — long enough to be usable as a quantum bit — just like an electron in a transistor or even just for light harvesting in a solar cell,” he said. “Nothing in the literature can explain these superlong exciton lifetimes, but we now understand why they have these characteristics.”

The researchers next will try to manipulate excitons with an electric field, which is a key step toward creating quantum-level logic elements.

“Classical semiconductors have already been miniaturized down to the doorstep before quantum effects change the game entirely,” Malko said. “If you can apply gate voltage and show that 2D TMD materials will work for future electronic devices, it’s a huge step. The atomic monolayer in 2D TMD material is 10 times smaller than the size limit with silicon. But can you create logic elements at that size? That’s what we need to find out.”

Other key contributors to this research are Dr. Yuri Gartstein, associate professor of physics at UT Dallas who did computational modeling that explained the reservoir behavior and coupling between different exciton species; and Dr. Masoud Mahjouri-Samani and graduate student Nurul Azam from Auburn University, who developed and used the LAST method to create the semiconductor material.

Funding for the research came from the U.S. Department of Energy, Basic Energy Sciences program (BES award #DE-SC0010697).

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

The University of Texas at Dallas is a Carnegie R1 classification (Doctoral Universities – Highest research activity) institution, located in a suburban setting 20 miles north of downtown Dallas. The University enrolls more than 27,600 students — 18,380 undergraduate and 9,250 graduate —and offers a broad array of bachelor’s, master’s, and doctoral degree programs.

Established by Eugene McDermott, J. Erik Jonsson and Cecil Green, the founders of Texas Instruments, UT Dallas is a young institution driven by the entrepreneurial spirit of its founders and their commitment to academic excellence. In 1969, the public research institution joined The University of Texas System and became The University of Texas at Dallas.

A high-energy, nimble, innovative institution, UT Dallas offers top-ranked science, engineering and business programs and has gained prominence for a breadth of educational paths from audiology to arts and technology. UT Dallas’ faculty includes a Nobel laureate, six members of the National Academies and more than 560 tenured and tenure-track professors.

From The Pritzker School of Molecular Engineering at UChicago: “Chicago expands and activates quantum network taking steps toward a secure quantum internet”

From The Pritzker School of Molecular Engineering at UChicago

At

The University of Chicago

Jun 16, 2022
Meredith Fore

A new 35-mile extension has built upon The DOE’s Argonne National Laboratory’s already 89-mile (144-kilometer) quantum loop, launched in 2020. The total network now connects to the South Side of Chicago, putting the city at the heart of one of the largest quantum networks in the country and further solidifying the region as a leading global hub for quantum research. Image courtesy of Chicago Quantum Exchange.

Quantum security trials with Toshiba have begun on 124-mile quantum network; open soon to industry and academics for testing.

Scientists with The Chicago Quantum Exchange (CQE) at the University of Chicago’s Pritzker School of Molecular Engineering announced today that for the first time they’ve connected the city of Chicago and suburban labs with a quantum network—nearly doubling the length of what was already one of the longest in the country. The Chicago network, which will soon be opened to academia and industry, will become one of the nation’s first publicly-available testbeds for quantum security technology.

The network is now actively running quantum security protocols using technology provided by Toshiba, distributing quantum keys over optic cable at a speed of over 80,000 quantum bits per second between Chicago and the western suburbs. Toshiba’s participation in the project makes the Chicago network a unique collaboration between academia, government and industry.

Researchers will use the Chicago network to test new communication devices, security protocols, and algorithms that will eventually connect distant quantum computers around the nation and the world. The work represents the next step towards a national quantum internet, which will have a profound impact on communications, computing, and national security.

A new 35-mile (56-kilometer) extension has built upon Argonne National Laboratory’s already 89-mile quantum loop launched in 2020. The total network is now composed of six nodes and 124 miles of optical fiber—transmitting particles carrying quantum-encoded information between the DOE’s Argonne National Laboratory in suburban Lemont and two buildings on the South Side of Chicago, one on the UChicago campus and the other at the CQE headquarters in the Hyde Park neighborhood. It puts Chicago at the heart of one of the largest quantum networks in the country and further solidifies the region as a leading global hub for quantum research.

Researchers work at The Pritzker Nanofabrication Facility at the University of Chicago. The special facility allows scientists to make and test new quantum technology. Photo by Robert Kozloff.

“The Chicago quantum network presents researchers with unprecedented opportunities to transmit quantum information in a real-world environment and push the boundaries of what is currently possible with quantum security protocols,” said David Awschalom, the Liew Family Professor in Molecular Engineering and Physics at the University of Chicago, director of the Chicago Quantum Exchange, and director of “Q-NEXT”, a Department of Energy National Quantum Information Science Research Center at Argonne. “This extension enables scientists from academia, industry, and government labs to collaborate on advancing our fundamental understanding of quantum communication and develop a secure quantum internet.”

“While this network is impressive in its scope, it is even more important as a testbed of experimentation into how quantum networks can be used. We look forward to working with CQE to explore the development of quantum network architectures that connect quantum sensors and computers together in new, exciting and useful ways,” said Jay Lowell, chief scientist for Boeing’s Disruptive Computing and Networks team

The rise of quantum computers represents both an enormous opportunity and a fundamental threat. Once operational, they are expected to be able to solve the kinds of problems that are nearly impossible for ordinary computers and thus easily break current encryption. In April, lawmakers in Congress introduced the “Quantum Cybersecurity Preparedness Act”, which prioritizes timely quantum-proof encrypting of sensitive information so that bad actors cannot steal the data now and decrypt it when stronger quantum computers become reality.

Scientists believe that quantum networks can draw upon the laws of quantum mechanics to be made virtually “unhackable.” Experts around the world have agreed that the implementation of quantum-secure communication networks is one of the most important technological frontiers of the 21st century.

Hack-proof encrypting can be done using quantum key distribution, which is the quantum security technology that was activated on the Chicago area quantum network on June 6, 2022, in a collaboration with Toshiba. Key distribution is a routine part of most internet security, but quantum technology can make it virtually impervious to hacking. In quantum key distribution, secret digital keys are distributed using quantum security protocols among parties communicating sensitive data. The quantum keys are sent through a network of optical fiber via particles of light, called photons, using the photons’ quantum properties to encode the bits that make up the keys. Any attempt to intercept the photons destroys the information they hold.

This kind of unhackable communication has applications anywhere secure communication is particularly vital, including industries such as finance, defense, voting and others.

“We’re thrilled to continue our partnership with the Chicago Quantum Exchange as trials begin on the network,” said Yasushi Kawakura, vice president of digital solutions at Toshiba. “It’s paramount that we develop quantum-proof technology to proactively defend against threats from the quantum future.”

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

The Pritzker School of Molecular Engineering is the first school of engineering at the University of Chicago. It was founded as the Institute for Molecular Engineering in 2011 by the university in partnership with Argonne National Laboratory. When the program was raised to the status of a school in 2019, it became the first school dedicated to molecular engineering in the United States. It is named for a major benefactor, the Pritzker Foundation.

The scientists, engineers, and students at PME use scientific research to pursue engineering solutions. The school does not have departments. Instead, it organizes its research around interdisciplinary “themes”: immuno-engineering, quantum engineering, autonomous materials, and water and energy. PME works toward technological advancements in areas of global importance, including sustainable energy and natural resources, immunotherapy-based approaches to cancer, “unhackable” communications networks, and a clean global water supply. The school plans to expand its research areas to address more issues of global importance.

IME was established in 2011, after three years of discussion and review. It was the largest academic program founded by the University of Chicago since 1988, when the Harris School of Public Policy Studies was established.

Matthew Tirrell was appointed founding Pritzker Director of IME in July 2011. The Pritzker Directorship honors the Pritzker Foundation, which donated a large gift in support of the institute. Tirrell is a researcher in biomolecular engineering and nanotechnology. His honors include election to The National Academy of Engineering, The American Academy of Arts and Sciences, and The National Academy of Sciences. He became dean of PME in 2019.

The William Eckhardt Research Center (WERC), which houses the school and part of the Physical Sciences Division, was constructed between 2011 and 2015. The WERC was named for alumnus William Eckhardt, in recognition of his donation to support scientific research at the university.

In 2019, the school received more than $23.1 million in research funding. From 2011 to 2019, faculty at the school have filed 69 invention disclosures and have created six companies.

On May 28, 2019, the University of Chicago announced a $100 million commitment from the Pritzker Foundation to support the institute’s transition to a school—the first school of molecular engineering in the U.S. The Pritzker Foundation helped establish the school with a new donation of $75 million, adding to an earlier $25 million donation that supported the institute and the construction of the Pritzker Nanofabrication Facility. In 2019, PME became the university’s first new school in three decades.

PME offers a graduate program in molecular engineering for both Master and Ph.D. students, as well as an undergraduate major and minor in molecular engineering offered with the College of the University of Chicago.

The institute began accepting applications to its doctoral program in fall 2013. The first class of graduate students was matriculated the following fall. In 2019, the school had 28 faculty members, 91 undergraduate students, 134 graduate students, and 75 postdoctoral fellows.

The graduate program curriculum includes various science and engineering disciplines, product design, entrepreneurship, and communication. The program is interdisciplinary, featuring a connected art program called STAGE Lab. STAGE Lab creates plays and films in the context of scientific research at PME.

The undergraduate major was added in spring 2015. It was the first engineering major offered at the University of Chicago. In 2018, the first undergraduate class received degrees in molecular engineering. When the school was established in 2019, it announced plans to expand its undergraduate offerings.

David Awschalom, a professor at PME, said the school has contributed to Chicago becoming a hub for quantum education and research. PME offers an advanced degree in quantum science and engineering. It also partnered with Harvard University to launch the Quantum Information Science and Engineering Network, a graduate student training program in quantum science and engineering. Participating students are paired with two mentors—one from academia and one from industry. The program was funded by a $1.6 million award from the National Science Foundation.

The school’s partnership with Argonne National Laboratory provides additional opportunities for research and innovation. Argonne’s facilities include the Advanced Photon Source, the Argonne Leadership Computing Facility, and the Center for Nanoscale Materials. The lab also has experience licensing new technology for industrial and commercial applications.

PME’s educational outreach initiatives include K-12 programs with events and internships throughout the year. In 2019, with the establishment of PME, the school also launched a partnership with City Colleges of Chicago. The multi-year program connects City College students interested in STEM fields with PME faculty and labs, with the goal of enabling these students to transfer into four-year STEM degree programs.

The University of Chicago is an urban research university that has driven new ways of thinking since 1890. Our commitment to free and open inquiry draws inspired scholars to our global campuses, where ideas are born that challenge and change the world.

We empower individuals to challenge conventional thinking in pursuit of original ideas. Students in the College develop critical, analytic, and writing skills in our rigorous, interdisciplinary core curriculum. Through graduate programs, students test their ideas with University of Chicago scholars, and become the next generation of leaders in academia, industry, nonprofits, and government.

University of Chicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: DOE’s Argonne National Laboratory, DOE’s Fermi National Accelerator Laboratory , and the Marine Biological Laboratory in Woods Hole, Massachusetts.
The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts. The University of Chicago is a private research university in Chicago, Illinois. Founded in 1890, its main campus is located in Chicago’s Hyde Park neighborhood. It enrolled 16,445 students in Fall 2019, including 6,286 undergraduates and 10,159 graduate students. The University of Chicago is ranked among the top universities in the world by major education publications, and it is among the most selective in the United States.

The university is composed of one undergraduate college and five graduate research divisions, which contain all of the university’s graduate programs and interdisciplinary committees. Chicago has eight professional schools: the Law School, the Booth School of Business, the Pritzker School of Medicine, the School of Social Service Administration, the Harris School of Public Policy, the Divinity School, the Graham School of Continuing Liberal and Professional Studies, and the Pritzker School of Molecular Engineering. The university has additional campuses and centers in London, Paris, Beijing, Delhi, and Hong Kong, as well as in downtown Chicago.

University of Chicago scholars have played a major role in the development of many academic disciplines, including economics, law, literary criticism, mathematics, religion, sociology, and the behavioralism school of political science, establishing the Chicago schools in various fields. Chicago’s Metallurgical Laboratory produced the world’s first man-made, self-sustaining nuclear reaction in Chicago Pile-1 beneath the viewing stands of the university’s Stagg Field. Advances in chemistry led to the “radiocarbon revolution” in the carbon-14 dating of ancient life and objects. The university research efforts include administration of DOE’s Fermi National Accelerator Laboratory and DOE’s Argonne National Laboratory, as well as the U Chicago Marine Biological Laboratory in Woods Hole, Massachusetts (MBL). The university is also home to the University of Chicago Press, the largest university press in the United States. The Barack Obama Presidential Center is expected to be housed at the university and will include both the Obama presidential library and offices of the Obama Foundation.

The University of Chicago’s students, faculty, and staff have included 100 Nobel laureates as of 2020, giving it the fourth-most affiliated Nobel laureates of any university in the world. The university’s faculty members and alumni also include 10 Fields Medalists, 4 Turing Award winners, 52 MacArthur Fellows, 26 Marshall Scholars, 27 Pulitzer Prize winners, 20 National Humanities Medalists, 29 living billionaire graduates, and have won eight Olympic medals.

The University of Chicago is enriched by the city we call home. In partnership with our neighbors, we invest in Chicago’s mid-South Side across such areas as health, education, economic growth, and the arts. Together with our medical center, we are the largest private employer on the South Side.

Research

According to the National Science Foundation, University of Chicago spent $423.9 million on research and development in 2018, ranking it 60th in the nation. It is classified among “R1: Doctoral Universities – Very high research activity” and is a founding member of the Association of American Universities and was a member of the Committee on Institutional Cooperation from 1946 through June 29, 2016, when the group’s name was changed to the Big Ten Academic Alliance. The University of Chicago is not a member of the rebranded consortium, but will continue to be a collaborator.

The university operates more than 140 research centers and institutes on campus. Among these are the Oriental Institute—a museum and research center for Near Eastern studies owned and operated by the university—and a number of National Resource Centers, including the Center for Middle Eastern Studies. Chicago also operates or is affiliated with several research institutions apart from the university proper. The university manages DOE’s Argonne National Laboratory, part of the United States Department of Energy’s national laboratory system, and co-manages DOE’s Fermi National Accelerator Laboratory, a nearby particle physics laboratory, as well as a stake in the Apache Point Observatory in Sunspot, New Mexico.
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SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft).

Apache Point Observatory, near Sunspot, New Mexico Altitude 2,788 meters (9,147 ft).
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Faculty and students at the adjacent Toyota Technological Institute at Chicago collaborate with the university. In 2013, the university formed an affiliation with the formerly independent Marine Biological Laboratory in Woods Hole, Mass. Although formally unrelated, the National Opinion Research Center is located on Chicago’s campus.

From The University of Colorado-Boulder: “What quantum information and snowflakes have in common and what we can do about it”

From The University of Colorado-Boulder

June 15, 2022
Daniel Strain

Qubits are a basic building block for quantum computers, but they’re also notoriously fragile—tricky to observe without erasing their information in the process. Now, new research from CU Boulder and the National Institute of Standards and Technology may be a leap forward for handling qubits with a light touch.

In the study, a team of physicists demonstrated that it could read out the signals from a type of qubit called a superconducting qubit using laser light—and without destroying the qubit at the same time.

Artist’s depiction of an electro-optic transducer, an ultra-thin device that can capture and transform the signals coming from a superconducting qubit. (Credit: Steven Burrows/JILA)

The group’s results could be a major step toward building a quantum internet, the researchers say. Such a network would link up dozens or even hundreds of quantum chips, allowing engineers to solve problems that are beyond the reach of even the fastest supercomputers around today. They could also, theoretically, use a similar set of tools to send unbreakable codes over long distances.

The study, published June 15 in the journal Nature, was led by JILA [Joint Institute for Laboratory Astrophysics], a joint research institute between CU Boulder and NIST.

“Currently, there’s no way to send quantum signals between distant superconducting processors like we send signals between two classical computers,” said Robert Delaney, lead author of the study and a former graduate student at JILA.

Quantum computers, which run on qubits, get their power by tapping into the properties of quantum physics, or the physics governing very small things. Delaney explained the traditional bits that run your laptop are pretty limited: They can only take on a value of zero or one, the numbers that underly most computer programming to date. Qubits, in contrast, can be zeros, ones or, through a property called “superposition,” exist as zeros and ones at the same time.

But working with qubits is also a bit like trying to catch a snowflake in your warm hand. Even the tiniest disturbance can collapse that superposition, causing them to look like normal bits.

In the new study, Delaney and his colleagues showed they could get around that fragility. The team uses a wafer-thin piece of silicon and nitrogen to transform the signal coming out of a superconducting qubit into visible light—the same sort of light that already carries digital signals from city to city through fiberoptic cables.

“Researchers have done experiments to extract optical light from a qubit, but not disrupting the qubit in the process is a challenge,” said study co-author Cindy Regal, JILA fellow and associate professor of physics at CU Boulder.

Fragile qubits

There are a lot of different ways to make a qubit, she added.

Some scientists have assembled qubits by trapping an atom in laser light. Others have experimented with embedding qubits into diamonds and other crystals. Companies like IBM and Google have begun designing quantum computer chips using qubits made from superconductors.

A quantum computer chip designed by IBM that includes four superconducting qubits. (Credit: npj Quantum Information, 2017)

Superconductors are materials that electrons can speed around without resistance. Under the right circumstances, superconductors will emit quantum signals in the form of tiny particles of light, or “photons,” that oscillate at microwave frequencies.

And that’s where the problem starts, Delaney said.

To send those kinds of quantum signals over long distances, researchers would first need to convert microwave photons into visible light, or optical, photons—which can whiz in relative safety through networks fiberoptic cables across town or even between cities. But when it comes to quantum computers, achieving that transformation is tricky, said study co-author Konrad Lehnert.

In part, that’s because one of the main tools you need to turn microwave photons into optical photons is laser light, and lasers are the nemesis of superconducting qubits. If even one stray photon from a laser beam hits your qubit, it will erase completely.

“The fragility of qubits and the essential incompatibility between superconductors and laser light makes usually prevents this kind of readout,” said Lehnert, a NIST and JILA fellow.

Secret codes

To get around that obstacle, the team turned to a go-between: a thin piece of material called an electro-optic transducer.

Delaney explained the team begins by zapping that wafer, which is too small to see without a microscope, with laser light. When microwave photons from a qubit bump into the device, it wobbles and spits out more photons—but these ones now oscillate at a completely different frequency. Microwave light goes in, and visible light comes out

In the latest study, the researchers tested their transducer using a real superconducting qubit. They discovered the thin material could achieve this switcheroo while also effectively keeping those mortal enemies, qubits and lasers, isolated from each other. In other words, none of the photons from the laser light leaked back to disrupt the superconductor.

“Our electro-optic transducer does not have much effect on the qubit,” Delaney said.

The team hasn’t gotten to the point where it can transmit actual quantum information through its microscopic telephone booth. Among other issues, the device isn’t particularly efficient yet. It takes about 500 microwave photons, on average, to produce a single visible light photon.

The researchers are currently working to improve that rate. Once they do, new possibilities may emerge in the quantum realm. Scientists could, theoretically, use a similar set of tools to send quantum signals over cables that would automatically erase their information when someone was trying to listen in. Mission Impossible made real, in other words, and all thanks to the sensitive qubit.

See the full article here .

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Please help promote STEM in your local schools.

Stem Education Coalition

As the flagship university of the state of Colorado The University of Colorado-Boulder , founded in 1876, five months before Colorado became a state. It is a dynamic community of scholars and learners situated on one of the most spectacular college campuses in the country, and is classified as an R1 University, meaning that it engages in a very high level of research activity. As one of 34 U.S. public institutions belonging to the prestigious Association of American Universities ), a selective group of major research universities in North America, – and the only member in the Rocky Mountain region – we have a proud tradition of academic excellence, with five Nobel laureates and more than 50 members of prestigious academic academies.

University of Colorado-Boulder has blossomed in size and quality since we opened our doors in 1877 – attracting superb faculty, staff, and students and building strong programs in the sciences, engineering, business, law, arts, humanities, education, music, and many other disciplines.

Today, with our sights set on becoming the standard for the great comprehensive public research universities of the new century, we strive to serve the people of Colorado and to engage with the world through excellence in our teaching, research, creative work, and service.

In 2015, the university comprised nine colleges and schools and offered over 150 academic programs and enrolled almost 17,000 students. Five Nobel Laureates, nine MacArthur Fellows, and 20 astronauts have been affiliated with CU Boulder as students; researchers; or faculty members in its history. In 2010, the university received nearly $454 million in sponsored research to fund programs like the Laboratory for Atmospheric and Space Physics and JILA. CU Boulder has been called a Public Ivy, a group of publicly funded universities considered as providing a quality of education comparable to those of the Ivy League.

The Colorado Buffaloes compete in 17 varsity sports and are members of the NCAA Division I Pac-12 Conference. The Buffaloes have won 28 national championships: 20 in skiing, seven total in men’s and women’s cross country, and one in football. The university has produced a total of ten Olympic medalists. Approximately 900 students participate in 34 intercollegiate club sports annually as well.

On March 14, 1876, the Colorado territorial legislature passed an amendment to the state constitution that provided money for the establishment of the University of Colorado in Boulder, the Colorado School of Mines in Golden, and the Colorado State University – College of Agricultural Sciences in Fort Collins.

Two cities competed for the site of the University of Colorado: Boulder and Cañon City. The consolation prize for the losing city was to be home of the new Colorado State Prison. Cañon City was at a disadvantage as it was already the home of the Colorado Territorial Prison. (There are now six prisons in the Cañon City area.)

The cornerstone of the building that became Old Main was laid on September 20, 1875. The doors of the university opened on September 5, 1877. At the time, there were few high schools in the state that could adequately prepare students for university work, so in addition to the University, a preparatory school was formed on campus. In the fall of 1877, the student body consisted of 15 students in the college proper and 50 students in the preparatory school. There were 38 men and 27 women, and their ages ranged from 12–23 years.

During World War II, Colorado was one of 131 colleges and universities nationally that took part in the V-12 Navy College Training Program which offered students a path to a navy commission.

University of Colorado-Boulder hired its first female professor, Mary Rippon, in 1878. It hired its first African-American professor, Charles H. Nilon, in 1956, and its first African-American librarian, Mildred Nilon, in 1962. Its first African American female graduate, Lucile Berkeley Buchanan, received her degree in 1918.

Research institutes

University of Colorado-Boulder’s research mission is supported by eleven research institutes within the university. Each research institute supports faculty from multiple academic departments, allowing institutes to conduct truly multidisciplinary research.

The Institute for Behavioral Genetics (IBG) is a research institute within the Graduate School dedicated to conducting and facilitating research on the genetic and environmental bases of individual differences in behavior. After its founding in 1967 IBG led the resurging interest in genetic influences on behavior. IBG was the first post-World War II research institute dedicated to research in behavioral genetics. IBG remains one of the top research facilities for research in behavioral genetics, including human behavioral genetics, psychiatric genetics, quantitative genetics, statistical genetics, and animal behavioral genetics.

The Institute of Cognitive Science (ICS) at CU Boulder promotes interdisciplinary research and training in cognitive science. ICS is highly interdisciplinary; its research focuses on education, language processing, emotion, and higher level cognition using experimental methods. It is home to a state-of-the-art fMRI system used to collect neuroimaging data.

ATLAS Institute is a center for interdisciplinary research and academic study, where engineering, computer science and robotics are blended with design-oriented topics. Part of CU Boulder’s College of Engineering and Applied Science, the institute offers academic programs at the undergraduate, master’s and doctoral levels, and administers research labs, hacker and makerspaces, and a black box experimental performance studio. At the beginning of the 2018–2019 academic year, approximately 1,200 students were enrolled in ATLAS academic programs and the institute sponsored six research labs.[64]

In addition to IBG, ICS and ATLAS, the university’s other institutes include Biofrontiers Institute, Cooperative Institute for Research in Environmental Sciences, Institute of Arctic & Alpine Research (INSTAAR), Institute of Behavioral Science (IBS), JILA, Laboratory for Atmospheric & Space Physics (LASP), Renewable & Sustainable Energy Institute (RASEI), and the University of Colorado Museum of Natural History.

From The Cornell Chronicle: “Harnessing machine learning to analyze quantum material”

From The Cornell Chronicle

June 14, 2022
Kate Blackwood
cunews@cornell.edu

Electrons and their behavior pose fascinating questions for quantum physicists, and recent innovations in sources, instruments and facilities allow researchers to potentially access even more of the information encoded in quantum materials.

However, these research innovations are producing unprecedented – and until now, indecipherable – volumes of data.

“The information content in a piece of material can quickly exceed the total information content in the Library of Congress, which is about 20 terabytes,” said Eun-Ah Kim, professor of physics in the College of Arts and Sciences, who is at the forefront of both quantum materials research and harnessing the power of machine learning to analyze data from quantum material experiments.

“The limited capacity of the traditional mode of analysis – largely manual – is quickly becoming the critical bottleneck,” Kim said.

A group led by Kim has successfully used a machine learning technique developed with Cornell computer scientists to analyze massive amounts of data from the quantum metal Cd2Re2O7, settling a debate about this particular material and setting the stage for future machine learning aided insight into new phases of matter.

An example of 3D X-ray diffraction data going through a phase transition upon cooling. The magenta plot shows special points associated with charge density wave formation as they were revealed by the machine learning algorithm X-TEC.
Krishna Mallayya/Provided.

The paper was published June 9 in PNAS .

Cornell physicists and computer scientists collaborated to build an unsupervised and interpretable machine learning algorithm, XRD Temperature Clustering (X-TEC). The researchers then applied X-TEC to investigate key elements of the pyrochlore oxide metal, Cd2Re2O7.

X-TEC analyzed eight terabytes of X-ray data, spanning 15,000 Brillouin zones (uniquely defined cells), in minutes.

“We used unsupervised machine learning algorithms, which are a perfect fit to translate high dimensional data into clusters that make sense to humans,” said Kilian Weinberger, professor of computer science in the Cornell Ann. S Bowers College of Computing and Information Science.

Thanks to this analysis, the researchers discovered important insights into electron behavior in the material, detecting what is known as the pseudo-Goldstone mode. They were trying to understand how atoms and electrons position themselves in an orderly fashion to optimize the interaction within the astronomically large “community” of electrons and atoms.

“In complex crystalline materials, a specific structure of multiple atoms, the unit cell, repeats itself in a regular arrangement like in a high-rise apartment complex,” Kim said. “The repositioning we discovered happens at a scale of each apartment unit, across the entire complex.”

Because the arrangement of the units stays the same, she said, it is difficult to detect this repositioning by watching from the outside. However, the repositioning almost spontaneously breaks a continuous symmetry, which results in a pseudo-Goldstone mode.

“The existence of pseudo-Goldstone mode can reveal the secret symmetries in the system that can be hard to see otherwise,” Kim said. “Our discovery was enabled by X-TEC.”

This discovery is significant for three reasons, Kim said. First, it shows that machine learning can be used to analyze voluminous X-ray powder diffraction (XRD) data, serving as a prototype for applications of X-TEC as it scales up. X-TEC, available to researchers as a software package, will be integrated into the synchrotron as an analysis tool at the Advanced Photon Source and at the Cornell High Energy Synchrotron Source.

Second, the discovery settles a debate concerning the physics of Cd2Re2O7.

“To the best of our knowledge, this is the first instance of the detection of a Goldstone mode using XRD,” Kim said. “This atomic scale insight into fluctuations in a complex quantum material will be only the first example of answering key scientific questions accompanying any discovery of new phases of matter … using information-rich voluminous diffraction data.”

Third, the discovery showcases what collaboration between physicists and computer scientists can accomplish.

“The mathematical inner workings of machine-learning algorithms are often not unlike models in physics but applied to high dimensional data,” Weinberger said. “Working with physicists is a lot of fun, because they are so good at modeling the natural world. When it comes to data modeling, they truly hit the ground running.”

Co-authors include Geoff Pleiss, M.S. ’18, Ph.D. ’20; Jordan Venderley, M.S. ’17, Ph.D. ’19; Krishnanand Mallayya, postdoctoral researcher in the Lab of Atomic and Solid State Physics; and Michael Matty, a doctoral candidate in the field of physics. The research was done in collaboration with colleagues at Argonne National Lab.

This research was supported by a grant from the National Science Foundation and a grant from the Department of Energy.

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Once called “the first American university” by educational historian Frederick Rudolph, Cornell University represents a distinctive mix of eminent scholarship and democratic ideals. Adding practical subjects to the classics and admitting qualified students regardless of nationality, race, social circumstance, gender, or religion was quite a departure when Cornell was founded in 1865.

Today’s Cornell reflects this heritage of egalitarian excellence. It is home to the nation’s first colleges devoted to hotel administration, industrial and labor relations, and veterinary medicine. Both a private university and the land-grant institution of New York State, Cornell University is the most educationally diverse member of the Ivy League.

On the Ithaca campus alone nearly 20,000 students representing every state and 120 countries choose from among 4,000 courses in 11 undergraduate, graduate, and professional schools. Many undergraduates participate in a wide range of interdisciplinary programs, play meaningful roles in original research, and study in Cornell programs in Washington, New York City, and the world over.

Cornell University is a private, statutory, Ivy League and land-grant research university in Ithaca, New York. Founded in 1865 by Ezra Cornell and Andrew Dickson White, the university was intended to teach and make contributions in all fields of knowledge—from the classics to the sciences, and from the theoretical to the applied. These ideals, unconventional for the time, are captured in Cornell’s founding principle, a popular 1868 quotation from founder Ezra Cornell: “I would found an institution where any person can find instruction in any study.”

The university is broadly organized into seven undergraduate colleges and seven graduate divisions at its main Ithaca campus, with each college and division defining its specific admission standards and academic programs in near autonomy. The university also administers two satellite medical campuses, one in New York City and one in Education City, Qatar, and Jacobs Technion-Cornell Institute in New York City, a graduate program that incorporates technology, business, and creative thinking. The program moved from Google’s Chelsea Building in New York City to its permanent campus on Roosevelt Island in September 2017.

Cornell is one of the few private land grant universities in the United States. Of its seven undergraduate colleges, three are state-supported statutory or contract colleges through the SUNY – The State University of New York system, including its Agricultural and Human Ecology colleges as well as its Industrial Labor Relations school. Of Cornell’s graduate schools, only the veterinary college is state-supported. As a land grant college, Cornell operates a cooperative extension outreach program in every county of New York and receives annual funding from the State of New York for certain educational missions. The Cornell University Ithaca Campus comprises 745 acres, but is much larger when the Cornell Botanic Gardens (more than 4,300 acres) and the numerous university-owned lands in New York City are considered.

Alumni and affiliates of Cornell have reached many notable and influential positions in politics, media, and science. As of January 2021, 61 Nobel laureates, four Turing Award winners and one Fields Medalist have been affiliated with Cornell. Cornell counts more than 250,000 living alumni, and its former and present faculty and alumni include 34 Marshall Scholars, 33 Rhodes Scholars, 29 Truman Scholars, 7 Gates Scholars, 55 Olympic Medalists, 10 current Fortune 500 CEOs, and 35 billionaire alumni. Since its founding, Cornell has been a co-educational, non-sectarian institution where admission has not been restricted by religion or race. The student body consists of more than 15,000 undergraduate and 9,000 graduate students from all 50 American states and 119 countries.

History

Cornell University was founded on April 27, 1865; the New York State (NYS) Senate authorized the university as the state’s land grant institution. Senator Ezra Cornell offered his farm in Ithaca, New York, as a site and $500,000 of his personal fortune as an initial endowment. Fellow senator and educator Andrew Dickson White agreed to be the first president. During the next three years, White oversaw the construction of the first two buildings and traveled to attract students and faculty. The university was inaugurated on October 7, 1868, and 412 men were enrolled the next day.

Cornell developed as a technologically innovative institution, applying its research to its own campus and to outreach efforts. For example, in 1883 it was one of the first university campuses to use electricity from a water-powered dynamo to light the grounds. Since 1894, Cornell has included colleges that are state funded and fulfill statutory requirements; it has also administered research and extension activities that have been jointly funded by state and federal matching programs.

Cornell has had active alumni since its earliest classes. It was one of the first universities to include alumni-elected representatives on its Board of Trustees. Cornell was also among the Ivies that had heightened student activism during the 1960s related to cultural issues; civil rights; and opposition to the Vietnam War, with protests and occupations resulting in the resignation of Cornell’s president and the restructuring of university governance. Today the university has more than 4,000 courses. Cornell is also known for the Residential Club Fire of 1967, a fire in the Residential Club building that killed eight students and one professor.

Since 2000, Cornell has been expanding its international programs. In 2004, the university opened the Weill Cornell Medical College in Qatar. It has partnerships with institutions in India, Singapore, and the People’s Republic of China. Former president Jeffrey S. Lehman described the university, with its high international profile, a “transnational university”. On March 9, 2004, Cornell and Stanford University laid the cornerstone for a new ‘Bridging the Rift Center’ to be built and jointly operated for education on the Israel–Jordan border.

Research

Cornell, a research university, is ranked fourth in the world in producing the largest number of graduates who go on to pursue PhDs in engineering or the natural sciences at American institutions, and fifth in the world in producing graduates who pursue PhDs at American institutions in any field. Research is a central element of the university’s mission; in 2009 Cornell spent $671 million on science and engineering research and development, the 16th highest in the United States. Cornell is classified among “R1: Doctoral Universities – Very high research activity”.

For the 2016–17 fiscal year, the university spent $984.5 million on research. Federal sources constitute the largest source of research funding, with total federal investment of $438.2 million. The agencies contributing the largest share of that investment are The Department of Health and Human Services and the National Science Foundation, accounting for 49.6% and 24.4% of all federal investment, respectively. Cornell was on the top-ten list of U.S. universities receiving the most patents in 2003, and was one of the nation’s top five institutions in forming start-up companies. In 2004–05, Cornell received 200 invention disclosures; filed 203 U.S. patent applications; completed 77 commercial license agreements; and distributed royalties of more than $4.1 million to Cornell units and inventors.

Since 1962, Cornell has been involved in unmanned missions to Mars. In the 21st century, Cornell had a hand in the Mars Exploration Rover Mission. Cornell’s Steve Squyres, Principal Investigator for the Athena Science Payload, led the selection of the landing zones and requested data collection features for the Spirit and Opportunity rovers. NASA-JPL/Caltech engineers took those requests and designed the rovers to meet them. The rovers, both of which have operated long past their original life expectancies, are responsible for the discoveries that were awarded 2004 Breakthrough of the Year honors by Science. Control of the Mars rovers has shifted between National Aeronautics and Space Administration’s JPL-Caltech and Cornell’s Space Sciences Building.

Further, Cornell researchers discovered the rings around the planet Uranus, and Cornell built and operated the telescope at Arecibo Observatory located in Arecibo, Puerto Rico until 2011, when they transferred the operations to SRI International, the Universities Space Research Association and the Metropolitan University of Puerto Rico [Universidad Metropolitana de Puerto Rico].

The Automotive Crash Injury Research Project was begun in 1952. It pioneered the use of crash testing, originally using corpses rather than dummies. The project discovered that improved door locks; energy-absorbing steering wheels; padded dashboards; and seat belts could prevent an extraordinary percentage of injuries.

In the early 1980s, Cornell deployed the first IBM 3090-400VF and coupled two IBM 3090-600E systems to investigate coarse-grained parallel computing. In 1984, the National Science Foundation began work on establishing five new supercomputer centers, including the Cornell Center for Advanced Computing, to provide high-speed computing resources for research within the United States. As a National Science Foundation center, Cornell deployed the first IBM Scalable Parallel supercomputer.

In the 1990s, Cornell developed scheduling software and deployed the first supercomputer built by Dell. Most recently, Cornell deployed Red Cloud, one of the first cloud computing services designed specifically for research. Today, the center is a partner on the National Science Foundation XSEDE-Extreme Science Engineering Discovery Environment supercomputing program, providing coordination for XSEDE architecture and design, systems reliability testing, and online training using the Cornell Virtual Workshop learning platform.

Cornell scientists have researched the fundamental particles of nature for more than 70 years. Cornell physicists, such as Hans Bethe, contributed not only to the foundations of nuclear physics but also participated in the Manhattan Project. In the 1930s, Cornell built the second cyclotron in the United States. In the 1950s, Cornell physicists became the first to study synchrotron radiation.

During the 1990s, the Cornell Electron Storage Ring, located beneath Alumni Field, was the world’s highest-luminosity electron-positron collider. After building the synchrotron at Cornell, Robert R. Wilson took a leave of absence to become the founding director of DOE’s Fermi National Accelerator Laboratory, which involved designing and building the largest accelerator in the United States.

Cornell’s accelerator and high-energy physics groups are involved in the design of the proposed ILC-International Linear Collider(JP) and plan to participate in its construction and operation. The International Linear Collider(JP), to be completed in the late 2010s, will complement the CERN Large Hadron Collider(CH) and shed light on questions such as the identity of dark matter and the existence of extra dimensions.

As part of its research work, Cornell has established several research collaborations with universities around the globe. For example, a partnership with the University of Sussex(UK) (including the Institute of Development Studies at Sussex) allows research and teaching collaboration between the two institutions.

From “physicsworld.com” : “Adapting a Surface Microscopy Tool for Quantum Studies”

From “physicsworld.com”

Tyler Harvey | Lawrence Berkeley National Laboratory

Scanning electron microscopes using laser-engineered electron quantum states enter the quantum optics ring.

Custom-designed scanning transmission electron microscope at Cornell University by David Muller/Cornell University

An ultraviolet laser pulse (purple) triggers photoemission of an electron pulse (green) from the scanning electron microscope’s electron source. These electrons are focused onto the specimen—for this instrument, possibilities include just-fabricated metamaterials, in situ retinal implants, or two-level quantum systems such as a quantum dot—where they interact with the optical field of a second infrared laser pulse (red). This interaction can prepare electrons into a superposition of energy states separated exactly by the infrared photon energy, as recorded by a spectrometer. The lower right inset shows electron energy spectra with increasing interaction strength along the vertical axis.

Often, the best way to understand the structure and behavior of a material is to examine it under a microscope. To reveal features on a scale smaller than the wavelength of visible light—about 1/100th the width of human hair—electrons are often the right tool for the job. Researchers have used transmission electron microscopes (TEMs) to image the motion of single atoms and the structure of SARS-CoV-2, the virus that causes COVID-19. Scanning electron microscopes (SEMs) are smaller and less expensive instruments that operate at lower energies and can image the surface of a material in its original form. SEMs can map the elemental composition of rocks right out of the ground, identify single nanoscale defects in hundreds of thousands of computer chips, and even print 3D microscale prototypes. In addition to their day jobs as imaging tools, TEMs have recently taken up a side hustle as a workbench for quantum-mechanics experiments. Now, researchers from the University of Erlangen-Nuremberg in Germany have built an SEM with quantum credentials [1*].

One avenue for quantum experiments in an electron microscope involves simultaneously shooting electrons and a laser beam at a material so that electrons inelastically scatter with the laser photons[2]. Electrons cannot absorb or emit a photon in free space as doing so would violate conservation of energy and momentum. However, a material offers just the kick needed to conserve both energy and momentum so an electron can exchange photons with the laser field [3]. An electron energy spectrum recorded after many electrons have participated in this inelastic electron-light interaction shows a range of evenly spaced peaks separated by the photon energy of the laser (Fig. 1). Because the laser field essentially behaves in a classical way, electrons emerge from the interaction in a controllable, nearly pure quantum state—in other words, the laser can be used to shape the electron state. And the electron state is special: a train of attosecond electron pulses forms with a period equal to the optical cycle of the laser [4]. These pulses could probe the fastest dynamics in materials [4]. A second interaction can then reverse the first one—and restore the original electron state—through destructive interference [5]. Inelastic electron-light scattering (IELS) can prepare electrons into an engineered quantum state for the purposes of imaging or studying quantum interactions.

Between the potential to directly image the fastest material dynamics at atomic scales and the ability to engineer electron states using a laser, excitement has grown recently about IELS. For example, on the basic quantum side, researchers have used IELS to swirl electrons into a vortex state [6]. On the applied side, imaging with IELS is called photon-induced near-field electron microscopy (PINEM). PINEM has imaged the optical properties of systems such as surface plasmons and nanoparticles [2], proteins and cells [7], and even chiral nanostructures [8]. The SEM built by the University of Erlangen-Nuremberg team is capable of both performing quantum-mechanics experiments with electrons and imaging challenging specimens with PINEM.

PINEM was first developed in a TEM, an area where electron spectrometers are commercially available. Measuring the quantized change in electron energy that occurs when electrons interact with the laser field is relatively easy. The tricky part is achieving a high laser field: femtosecond or picosecond electron and laser pulses are typically used for the combination of high peak fields and low average power [3]. For multiple IELS interactions, which are necessary for more elaborate engineering of the electron state, the millimeter-scale gap where specimens sit in a TEM limits the tool’s versatility, whereas SEMs have a large specimen chamber that the operator can reach into with both hands, making experiments with multiple IELS interactions easier. The lower available electron energies of an SEM may also prove useful for a range of specimens; there may be resonances or other maxima in the electron-light scattering depending on geometry [7, 8], or the PINEM signal may be too weak at TEM energies to effectively image the specimen but sufficiently strong at lower energies [3, 8]. Additionally, the lower cost of SEMs makes them more accessible to new groups wanting to do IELS or PINEM experiments.

The instrument that the team developed makes PINEM possible in an SEM. They modified an electron source to produce picosecond electron pulses when struck by a laser pulse, added a path for a femtosecond pulsed laser to excite the specimen, and built an electron spectrometer for their SEM. Each of these steps is a significant project, but the group really triumphed by tying all the elements together: they characterized the instrument and probed a tungsten needle with PINEM. The measured electron spectra matched their simulations remarkably well, which suggests that they have an excellent understanding of the instrument they designed.

It will be exciting to see what experiments follow with this instrument. The ample space in an SEM chamber allowed this group to place a lens with a short focal length very close to the specimen. Doing so may allow them to produce a high laser field on the specimen. The tightly focused laser spot leads to a higher PINEM signal without increasing the average temperature of the specimen, making specimens with a weaker optical response more practical to image. PINEM in an SEM could also shed new light on larger specimens, such as a 3D metamaterial device, that do not fit into a TEM. This new microscope may help motivate the increasing availability of commercial SEM electron spectrometers, which would make building future PINEM-SEMs far easier. The wide-open specimen chamber and the uniquely low energy range give this instrument the ability to push the limits of PINEM imaging and of quantum experiments with electrons.

*References

R. Shiloh et al., “Quantum-coherent light-electron interaction in a scanning electron microscope,” Phys. Rev. Lett. 128, 235301 (2022).
B. Barwick et al., “Photon-induced near-field electron microscopy,” Nature 462, 902 (2009).
S. T. Park et al., “Photon-induced near-field electron microscopy (PINEM): theoretical and experimental,” New J. Phys. 12, 123028 (2010).
K. E. Priebe et al., “Attosecond electron pulse trains and quantum state reconstruction in ultrafast transmission electron microscopy,” Nat. Photon. 11, 793 (2017).
K. E. Echternkamp et al., “Ramsey-type phase control of free-electron beams,” Nat. Phys. 12, 1000 (2016).
G. M. Vanacore et al., “Ultrafast generation and control of an electron vortex beam via chiral plasmonic near fields,” Nat. Mater. 18, 573 (2019).
T. R. Harvey et al., “Probing chirality with inelastic electron-light scattering,” Nano Lett. 20, 4377 (2020).
N. Talebi, “Strong interaction of slow electrons with near-field light visited from first principles,” Phys. Rev. Lett. 125, 080401 (2020).

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physicsworld is a publication of the Institute of Physics. The Institute of Physics is a leading scientific society. We are a charitable organisation with a worldwide membership of more than 50,000, working together to advance physics education, research and application.

We engage with policymakers and the general public to develop awareness and understanding of the value of physics and, through IOP Publishing, we are world leaders in professional scientific communications.

From MPG Institute for Quantum Optics [MPG Institut für Quantenoptik] (DE) : “Topological phase detected in spin chains”

Max Planck Institut für Quantenoptik (DE)

From MPG Institute for Quantum Optics [MPG Institut für Quantenoptik] (DE)

June 03, 2022

Dr. Timon Hilker
Research Group Leader
+49 89 32905-215
timon.hilker@mpq.mpg.de
Max Planck Institute of Quantum Optics

Katharina Jarrah
PR and Communications
+49 89 32905-213
katharina.jarrah@mpq.mpg.de
Max Planck Institute of Quantum Optics

In a special arrangement of atomic spins, Max Planck physicists have measured the properties of the so-called “Haldane phase” in an experiment. To do so, they used a quantum mechanical trick.

In some materials, there are phases between which a transition is not possible because they are protected by a certain form of symmetry. Physicists refer to these as topological phases. One example of this is the Haldane phase, named after the 2016 Nobel Prize winner in physics Duncan Haldane, which occurs in antiferromagnetic spin-1 chains. A team of researchers at MPQ has now succeeded in realising this exotic state of matter in a simple system of ultracold atoms. Using a quantum gas microscope, they brought the atomic spins into the desired shape, measured the properties of the system and thus found the hidden internal order typical of the Haldane phase.

Dr Pimonpan Sompet (first author of the paper) aligning the second-harmonic generation cavity. The researchers use the UV light produced in here to cool the lithium atoms in the experiment. Credit: MPQ.

Any matter occurs in different phases, which can merge into one another. An example of this is water, which exists in liquid form, as ice or steam – depending on the external conditions. The different physical phases have the same chemical composition, but a different degree of internal order. If the temperature or pressure changes, for example, the water changes into a different phase at a certain point. However: In some materials, there are phases between which a transition is not possible because they are protected by a certain form of symmetry – a property of the system that thus remains unchanged, for example, during a reflection or rotation. Only by breaking the symmetry is a phase transition possible. Physicists refer to this as topological phases, whose investigation in recent years has led to a deeper understanding of the structure of quantum systems.

Measuring the “Haldane phase”

To date, such properties have almost only been accessible in theoretical models and calculations or through indirect measurements on solids. But now a team of researchers at the Max Planck Institute of Quantum Optics (MPQ) in Garching has succeeded in generating a special, exemplary type of topological phase in the laboratory and analysing it experimentally. The scientists in the MPQ Department of Quantum Many-Body Systems, led by Prof Dr Immanuel Bloch and Dr Timon Hilker, created a so-called “Haldane phase”. It is named after the British physicist Duncan Haldane, who described topological phases of quantum systems for the first time and received the Nobel Prize in Physics for it in 2016 together with two other researchers.

Haldane focused his attention, among other things, on the possible existence of a topological phase in a chain of antiferromagnetic spin-1 particles. A spin is a quantum mechanical property of a particle such as electrons or atoms, which can be interpreted in a simple way as the angular momentum of the particle when it rotates around its own axis. In an antiferromagnetic material, the the spins prefer other spins to have a different direction of rotation in their immediate vicinity.

This can lead to a periodic ordering of the spins, which, however, is invisible in spin-1 systems in classical measurements. The theoretical prediction said that there nevertheless is an order, but that it is “hidden”. To detect it, all spins would have to be measured individually and simultaneously – which is not possible in solids. But the researchers at MPQ used artificial materials in which the spins are much further apart. Therein, they produced a spin-1 chain with the characteristics described by Haldane.

The trick with the spin pairs

“Until now, this was difficult to realize,” says Sarah Hirthe. That’s why the PhD candidate at the MPQ, together with her colleague Dominik Bourgund and other members of the Garching team, resorted to a trick: “We created a spin-1 chain in an indirect way by building it up from spins with the value ½, of which we added two each,” explains Bourgund. In this way, cells with integer spin were created that were lined up in a chain.

To realise this special structure, the team used a so-called quantum gas microscope. Such a device can be used, for example, to study the magnetic properties of individual atoms that have previously been arranged in a certain way. The scientists therefore also speak of a quantum simulator, with which matter is artificially constructed from its elementary building blocks. “To do this, we use standing waves of laser light that form a kind of lattice for atoms,” explains Sarah Hirthe. This lattice is then shaped into the desired form with the help of further lasers and countless tiny, movable mirrors.

“For the experiments on the topological Haldane phase, we placed atoms in such a two-dimensional optical lattice,” the physicist reports. “In a vacuum and at a temperature close to absolute zero, the atoms then arranged themselves exactly in the way dictated by light.” The researchers chose a lattice structure that gave the atoms, along with their spins, the shape of a ladder — with two “legs” and “rungs” in between. “The rungs of these so-called Fermi-Hubbard ladders each connected two atomic spins to form unit cells with spin 1,” explains Dominik Bourgund. “In this arrangement, we were using a concept known in theoretical physics as the “AKLT model”.”

An atomic ladder with “dangling” edge spins

Illustration of the main concepts in the paper: on the left an illustration of the lattice potential used, on the right an exemplary snapshot of a single ladder with 14 individual atoms visible in green. Below that, a schematic explanation of how the ladder geometry is mapped onto a spin-1 chain. The dangling edge spins are shown in grey.

“The highlight of the experiment was that we specially tailored the edges of the system,” says Hirthe: the two legs of the quantum ladder were offset from each other by one atom. In this way, the half-integer spins of the atoms could be combined in a diagonal offset to form unit cells. The consequence of this shape: individual spins without a direct partner “dangled” at both ends of the system – called edge states in technical jargon. “Such spins and their magnetic moments can assume different orientations without any additional energy input,” explains Dominik Bourgund. In this way, they give the system characteristic properties based on the special symmetry – the typical hallmarks of the Haldane phase. For comparison, the Max Planck researchers also created a “trivial” topological phase without edge states.

To analyze the characteristics of the two phases, the scientists measured the magnetization of both the individual spins and the entire system of all atoms along a mental string under the quantum gas microscope. Only in this way it was possible to find the predicted “hidden” internal order. “Our results confirm the expected topological properties of both the overall system and the edge states,” notes Timon Hilker, who leads the project. “This shows: We have made the complex structure accessible for measurements through a simple system.”

Solid basis for quantum computing?

With their results, the Max Planck researchers have not only laid the foundation for experimentally verifying theoretical predictions about topological phases. Their new findings could also find practical application in the future – in quantum computers. Their function is based on “qubits”, fundamental computing units in the form of quantum states. The shortcoming in the technical realisation so far is their low stability: if the qubits lose their value, the data is also lost. If they could be represented by topological phases, which are quite robust against external interference due to their close connection to a fundamental symmetry, this could significantly simplify computing with a quantum computer.

Science paper
Nature

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Research at the MPG Institute for Quantum Optics [MPG Institut für Quantenoptik ] (DE)

Light can behave as an electromagnetic wave or a shower of particles that have no mass, called photons, depending on the conditions under which it is studied or used. Matter, on the other hand, is composed of particles, but it can actually exhibit wave-like properties, giving rise to many astonishing phenomena in the microcosm.

At our institute we explore the interaction of light and quantum systems, exploiting the two extreme regimes of the wave-particle duality of light and matter. On the one hand we handle light at the single photon level where wave-interference phenomena differ from those of intense light beams. On the other hand, when cooling ensembles of massive particles down to extremely low temperatures we suddenly observe phenomena that go back to their wave-like nature. Furthermore, when dealing with ultrashort and highly intense light pulses comprising trillions of photons we can completely neglect the particle properties of light. We take advantage of the large force that the rapidly oscillating electromagnetic field exerts on electrons to steer their motion within molecules or accelerate them to relativistic energies.

From Purdue University: “A new duality discovered at Purdue University solves a physics mystery”

From Purdue University

5.23.22
Cheryl Pierce
Communications
pierce81@purdue.edu

A Poincaré half-plane can be viewed in the background which demonstrates a curved surface. The white geodesics of the curved surface are shown as an analog of straight lines on a flat space. White balls moving in the right direction demonstrate the geometric origin of an extraordinary skin effect in non-Hermitian physics. Graphic provided by Chenwei Lv and Ren Zhang.

In conventional wisdom, producing a curved space requires distortions, such as bending or stretching a flat space. A team of researchers at Purdue University have discovered a new method to create curved spaces that also solves a mystery in physics. Without any physical distortions of physical systems, the team has designed a scheme using non-Hermiticity**, which exists in any systems coupled to environments, to create a hyperbolic surface and a variety of other prototypical curved spaces.

“Our work may revolutionize the general public’s understanding of curvatures and distance,” says Qi Zhou, Professor of Physics and Astronomy. “It has also answered long-standing questions in non-Hermitian quantum mechanics by bridging non-Hermitian physics and curved spaces. These two subjects were assumed to be completely disconnected. The extraordinary behaviors of non-Hermitian systems, which have puzzled physicists for decades, become no longer mysterious if we recognize that the space has been curved. In other words, non-Hermiticity and curved spaces are dual to each other, being the two sides of the same coin.”

The Team recently published their findings in Nature Communications. Of the members of the team, most work at Purdue University’s West Lafayette campus. Chenwei Lv, graduate student, is the lead author, and other members of the Purdue team include Prof. Qi Zhou, and Zhengzheng Zhai, postdoctoral fellow. The co-first author, Prof. Ren Zhang from Xi’an Jiaotong University, was a visiting scholar at Purdue when the project was initiated.

In order to understand how this discovery works, first one must understand the difference between Hermitian and non-Hermitian systems in physics. Zhou explains it using an example in which a quantum particle can “hop” between different sites on a lattice. If the probability for a quantum particle to hop in the right direction is the same as the probability to hop in the left direction, then the Hamiltonian is Hermitian. If these two probabilities are different, the Hamiltonian is non-Hermitian. This is the reason that Chenwei and Ren Zhang have used arrows with different sizes and thicknesses to denote the hopping probabilities in opposite directions in their plot.

“Typical textbooks of quantum mechanics mainly focus on systems governed by Hamiltonians* that are Hermitian,” says Lv. “A quantum particle moving in a lattice needs to have an equal probability to tunnel along the left and right directions. Whereas Hermitian Hamiltonians are well-established frameworks for studying isolated systems, the couplings with the environment inevitably lead to dissipations in open systems, which may give rise to Hamiltonians that are no longer Hermitian. For instance, the tunneling amplitudes in a lattice are no longer equal in opposite directions, a phenomenon called nonreciprocal tunneling. In such non-Hermitian systems, familiar textbook results no longer apply and some may even look completely opposite to that of Hermitian systems. For instance, eigenstates of non-Hermitian systems are no longer orthogonal, in sharp contrast to what we learned in the first class of an undergraduate quantum mechanics course. These extraordinary behaviors of non-Hermitian systems have been intriguing physicists for decades, but many outstanding questions remain open.”

He further explains that their work provides an unprecedented explanation of fundamental non-Hermitian quantum phenomena. They found that a non-Hermitian Hamiltonian has curved the space where a quantum particle resides. For instance, a quantum particle in a lattice with nonreciprocal tunneling is in fact moving on a curved surface. The ratio of the tunneling amplitudes along one direction to that in the opposite direction controls how large the surface is curved. In such curved spaces, all the strange non-Hermitian phenomena, some of which may even appear unphysical, immediately become natural. It is the finite curvature that requires orthonormal conditions distinct from their counterparts in flat spaces. As such, eigenstates would not appear orthogonal if we used the theoretical formula derived for flat spaces. It is also the finite curvature that gives rise to the extraordinary non-Hermitian skin effect that all eigenstates concentrate near one edge of the system.

“This research is of fundamental importance and its implications are two-fold”, says Zhang. “On the one hand, it establishes non-Hermiticity as a unique tool to simulate intriguing quantum systems in curved spaces,” he explains. “Most quantum systems available in laboratories are flat and it often requires significant efforts to access quantum systems in curved spaces. Our results show that non-Hermiticity offers experimentalists an extra knob to access and manipulate curved spaces. An example is that a hyperbolic surface could be created and further be threaded by a magnetic field. This could allow experimentalists to explore the responses of quantum Hall states to finite curvatures, an outstanding question in condensed matter physics. On the other hand, the duality allows experimentalists to use curved spaces to explore non-Hermitian physics. For instance, our results provide experimentalists a new approach to access exceptional points using curved spaces and improve the precision of quantum sensors without resorting to dissipations.”

Now that the team has published their findings, they anticipate it spinning off into multiple directions for further study. Physicists studying curved spaces could implement their apparatuses to address challenging questions in non-Hermitian physics. Also, physicists working on non-Hermitian systems could tailor dissipations to access non-trivial curved spaces that cannot be easily obtained by conventional means. The Zhou research group will continue to theoretically explore more connections between non-Hermitian physics and curved spaces. They also hope to help bridge the gap between these two physics subjects and bring these two different communities together with future research.

According to the team, Purdue University is uniquely qualified to foster this type of quantum research. Purdue has been growing strong in quantum information science at a fast pace over the past few years. The Purdue Quantum Science and Engineering Institute paired with the Department of Physics and Astronomy, allow the team to collaborate with many colleagues with diverse expertise and foster interdepartmental and collegiate growth on a variety of platforms that exhibit dissipations and nonreciprocal tunneling.

*”Hamiltonian simulation”: (also referred to as quantum simulation) is a problem in quantum information science that attempts to find the computational complexity and quantum algorithms needed for simulating quantum systems.

**”Non-Hermiticity”: a subject in Quantum Mechanics which is too complex for consideration here. Not reducible to a sentence and only a subject for a professional quantum physicist.

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Purdue University is a public land-grant research university in West Lafayette, Indiana, and the flagship campus of the Purdue University system. The university was founded in 1869 after Lafayette businessman John Purdue donated land and money to establish a college of science, technology, and agriculture in his name. The first classes were held on September 16, 1874, with six instructors and 39 students.

The main campus in West Lafayette offers more than 200 majors for undergraduates, over 69 masters and doctoral programs, and professional degrees in pharmacy and veterinary medicine. In addition, Purdue has 18 intercollegiate sports teams and more than 900 student organizations. Purdue is a member of the Big Ten Conference and enrolls the second largest student body of any university in Indiana, as well as the fourth largest foreign student population of any university in the United States.

Purdue University is a member of the Association of American Universitiesand is classified among “R1: Doctoral Universities – Very high research activity”. Purdue has 25 American astronauts as alumni and as of April 2019, the university has been associated with 13 Nobel Prizes.

In 1865, the Indiana General Assembly voted to take advantage of the Morrill Land-Grant Colleges Act of 1862 and began plans to establish an institution with a focus on agriculture and engineering. Communities throughout the state offered facilities and funding in bids for the location of the new college. Popular proposals included the addition of an agriculture department at Indiana State University, at what is now Butler University. By 1869, Tippecanoe County’s offer included $150,000 (equivalent to $2.9 million in 2019) from Lafayette business leader and philanthropist John Purdue; $50,000 from the county; and 100 acres (0.4 km^2) of land from local residents.

On May 6, 1869, the General Assembly established the institution in Tippecanoe County as Purdue University, in the name of the principal benefactor. Classes began at Purdue on September 16, 1874, with six instructors and 39 students. Professor John S. Hougham was Purdue’s first faculty member and served as acting president between the administrations of presidents Shortridge and White. A campus of five buildings was completed by the end of 1874. In 1875, Sarah A. Oren, the State Librarian of Indiana, was appointed Professor of Botany.

Purdue issued its first degree, a Bachelor of Science in chemistry, in 1875, and admitted its first female students that autumn.

Emerson E. White, the university’s president, from 1876 to 1883, followed a strict interpretation of the Morrill Act. Rather than emulate the classical universities, White believed Purdue should be an “industrial college” and devote its resources toward providing a broad, liberal education with an emphasis on science, technology, and agriculture. He intended not only to prepare students for industrial work, but also to prepare them to be good citizens and family members.

Part of White’s plan to distinguish Purdue from classical universities included a controversial attempt to ban fraternities, which was ultimately overturned by the Indiana Supreme Court, leading to White’s resignation. The next president, James H. Smart, is remembered for his call in 1894 to rebuild the original Heavilon Hall “one brick higher” after it had been destroyed by a fire.

By the end of the nineteenth century, the university was organized into schools of agriculture, engineering (mechanical, civil, and electrical), and pharmacy; former U.S. President Benjamin Harrison served on the board of trustees. Purdue’s engineering laboratories included testing facilities for a locomotive, and for a Corliss steam engine—one of the most efficient engines of the time. The School of Agriculture shared its research with farmers throughout the state, with its cooperative extension services, and would undergo a period of growth over the following two decades. Programs in education and home economics were soon established, as well as a short-lived school of medicine. By 1925, Purdue had the largest undergraduate engineering enrollment in the country, a status it would keep for half a century.

President Edward C. Elliott oversaw a campus building program between the world wars. Inventor, alumnus, and trustee David E. Ross coordinated several fundraisers, donated lands to the university, and was instrumental in establishing the Purdue Research Foundation. Ross’s gifts and fundraisers supported such projects as Ross–Ade Stadium, the Memorial Union, a civil engineering surveying camp, and Purdue University Airport. Purdue Airport was the country’s first university-owned airport and the site of the country’s first college-credit flight training courses.

Amelia Earhart joined the Purdue faculty in 1935 as a consultant for these flight courses and as a counselor on women’s careers. In 1937, the Purdue Research Foundation provided the funds for the Lockheed Electra 10-E Earhart flew on her attempted round-the-world flight.

Every school and department at the university was involved in some type of military research or training during World War II. During a project on radar receivers, Purdue physicists discovered properties of germanium that led to the making of the first transistor. The Army and the Navy conducted training programs at Purdue and more than 17,500 students, staff, and alumni served in the armed forces. Purdue set up about a hundred centers throughout Indiana to train skilled workers for defense industries. As veterans returned to the university under the G.I. Bill, first-year classes were taught at some of these sites to alleviate the demand for campus space. Four of these sites are now degree-granting regional campuses of the Purdue University system. On-campus housing became racially desegregated in 1947, following pressure from Purdue President Frederick L. Hovde and Indiana Governor Ralph F. Gates.

After the war, Hovde worked to expand the academic opportunities at the university. A decade-long construction program emphasized science and research. In the late 1950s and early 1960s the university established programs in veterinary medicine, industrial management, and nursing, as well as the first computer science department in the United States. Undergraduate humanities courses were strengthened, although Hovde only reluctantly approved of graduate-level study in these areas. Purdue awarded its first Bachelor of Arts degrees in 1960. The programs in liberal arts and education, formerly administered by the School of Science, were soon split into an independent school.

The official seal of Purdue was officially inaugurated during the university’s centennial in 1969.

Consisting of elements from emblems that had been used unofficially for 73 years, the current seal depicts a griffin, symbolizing strength, and a three-part shield, representing education, research, and service.

In recent years, Purdue’s leaders have continued to support high-tech research and international programs. In 1987, U.S. President Ronald Reagan visited the West Lafayette campus to give a speech about the influence of technological progress on job creation.

In the 1990s, the university added more opportunities to study abroad and expanded its course offerings in world languages and cultures. The first buildings of the Discovery Park interdisciplinary research center were dedicated in 2004.

Purdue launched a Global Policy Research Institute in 2010 to explore the potential impact of technical knowledge on public policy decisions.

On April 27, 2017, Purdue University announced plans to acquire for-profit college Kaplan University and convert it to a public university in the state of Indiana, subject to multiple levels of approval. That school now operates as Purdue University Global, and aims to serve adult learners.

Campuses

Purdue’s campus is situated in the small city of West Lafayette, near the western bank of the Wabash River, across which sits the larger city of Lafayette. State Street, which is concurrent with State Road 26, divides the northern and southern portions of campus. Academic buildings are mostly concentrated on the eastern and southern parts of campus, with residence halls and intramural fields to the west, and athletic facilities to the north. The Greater Lafayette Public Transportation Corporation (CityBus) operates eight campus loop bus routes on which students, faculty, and staff can ride free of charge with Purdue Identification.

Organization and administration

The university president, appointed by the board of trustees, is the chief administrative officer of the university. The office of the president oversees admission and registration, student conduct and counseling, the administration and scheduling of classes and space, the administration of student athletics and organized extracurricular activities, the libraries, the appointment of the faculty and conditions of their employment, the appointment of all non-faculty employees and the conditions of employment, the general organization of the university, and the planning and administration of the university budget.

The Board of Trustees directly appoints other major officers of the university including a provost who serves as the chief academic officer for the university, several vice presidents with oversight over specific university operations, and the regional campus chancellors.

Academic divisions

Purdue is organized into thirteen major academic divisions.

College of Agriculture

The university’s College of Agriculture supports the university’s agricultural, food, life, and natural resource science programs. The college also supports the university’s charge as a land-grant university to support agriculture throughout the state; its agricultural extension program plays a key role in this.

College of Education

The College of Education offers undergraduate degrees in elementary education, social studies education, and special education, and graduate degrees in these and many other specialty areas of education. It has two departments: (a) Curriculum and Instruction and (b) Educational Studies.

College of Engineering

The Purdue University College of Engineering was established in 1874 with programs in Civil and Mechanical Engineering. The college now offers B.S., M.S., and Ph.D. degrees in more than a dozen disciplines. Purdue’s engineering program has also educated 24 of America’s astronauts, including Neil Armstrong and Eugene Cernan who were the first and last astronauts to have walked on the Moon, respectively. Many of Purdue’s engineering disciplines are recognized as top-ten programs in the U.S. The college as a whole is currently ranked 7th in the U.S. of all doctorate-granting engineering schools by U.S. News & World Report.

Exploratory Studies

The university’s Exploratory Studies program supports undergraduate students who enter the university without having a declared major. It was founded as a pilot program in 1995 and made a permanent program in 1999.

College of Health and Human Sciences

The College of Health and Human Sciences was established in 2010 and is the newest college. It offers B.S., M.S. and Ph.D. degrees in all 10 of its academic units.

College of Liberal Arts

Purdue’s College of Liberal Arts contains the arts, social sciences and humanities programs at the university. Liberal arts courses have been taught at Purdue since its founding in 1874. The School of Science, Education, and Humanities was formed in 1953. In 1963, the School of Humanities, Social Sciences, and Education was established, although Bachelor of Arts degrees had begun to be conferred as early as 1959. In 1989, the School of Liberal Arts was created to encompass Purdue’s arts, humanities, and social sciences programs, while education programs were split off into the newly formed School of Education. The School of Liberal Arts was renamed the College of Liberal Arts in 2005.

Krannert School of Management

The Krannert School of Management offers management courses and programs at the undergraduate, master’s, and doctoral levels.

College of Pharmacy

The university’s College of Pharmacy was established in 1884 and is the 3rd oldest state-funded school of pharmacy in the United States. The school offers two undergraduate programs leading to the B.S. in Pharmaceutical Sciences (BSPS) and the Doctor of Pharmacy (Pharm.D.) professional degree. Graduate programs leading to M.S. and Ph.D. degrees are offered in three departments (Industrial and Physical Pharmacy, Medicinal Chemistry and Molecular Pharmacology, and Pharmacy Practice). Additionally, the school offers several non-degree certificate programs and post-graduate continuing education activities.

Purdue Polytechnic Institute

The Purdue Polytechnic Institute offers bachelor’s, master’s and Ph.D. degrees in a wide range of technology-related disciplines. With over 30,000 living alumni, it is one of the largest technology schools in the United States.

College of Science

The university’s College of Science houses the university’s science departments: Biological Sciences; Chemistry; Computer Science; Earth, Atmospheric, & Planetary Sciences; Mathematics; Physics & Astronomy; and Statistics. The science courses offered by the college account for about one-fourth of Purdue’s one million student credit hours.

College of Veterinary Medicine

The College of Veterinary Medicine is accredited by the AVMA to offer the Doctor of Veterinary Medicine degree, associate’s and bachelor’s degrees in veterinary technology, master’s and Ph.D. degrees, and residency programs leading to specialty board certification. Within the state of Indiana, the Purdue University College of Veterinary Medicine is the only veterinary school, while the Indiana University School of Medicine is one of only two medical schools (the other being Marian University College of Osteopathic Medicine). The two schools frequently collaborate on medical research projects.

Honors College

Purdue’s Honors College supports an honors program for undergraduate students at the university.

The Graduate School

The university’s Graduate School supports graduate students at the university.

Research

The university expended $622.814 million in support of research system-wide in 2017, using funds received from the state and federal governments, industry, foundations, and individual donors. The faculty and more than 400 research laboratories put Purdue University among the leading research institutions. Purdue University is considered by the Carnegie Classification of Institutions of Higher Education to have “very high research activity”. Purdue also was rated the nation’s fourth best place to work in academia, according to rankings released in November 2007 by The Scientist magazine. Purdue’s researchers provide insight, knowledge, assistance, and solutions in many crucial areas. These include, but are not limited to Agriculture; Business and Economy; Education; Engineering; Environment; Healthcare; Individuals, Society, Culture; Manufacturing; Science; Technology; Veterinary Medicine. The Global Trade Analysis Project (GTAP), a global research consortium focused on global economic governance challenges (trade, climate, resource use) is also coordinated by the University. Purdue University generated a record $438 million in sponsored research funding during the 2009–10 fiscal year with participation from National Science Foundation, National Aeronautics and Space Administration, and the Department of Agriculture, Department of Defense, Department of Energy, and Department of Health and Human Services. Purdue University was ranked fourth in Engineering research expenditures amongst all the colleges in the United States in 2017, with a research expenditure budget of 244.8 million. Purdue University established the Discovery Park to bring innovation through multidisciplinary action. In all of the eleven centers of Discovery Park, ranging from entrepreneurship to energy and advanced manufacturing, research projects reflect a large economic impact and address global challenges. Purdue University’s nanotechnology research program, built around the new Birck Nanotechnology Center in Discovery Park, ranks among the best in the nation.

The Purdue Research Park which opened in 1961 was developed by Purdue Research Foundation which is a private, nonprofit foundation created to assist Purdue. The park is focused on companies operating in the arenas of life sciences, homeland security, engineering, advanced manufacturing and information technology. It provides an interactive environment for experienced Purdue researchers and for private business and high-tech industry. It currently employs more than 3,000 people in 155 companies, including 90 technology-based firms. The Purdue Research Park was ranked first by the Association of University Research Parks in 2004.

Purdue’s library system consists of fifteen locations throughout the campus, including an archives and special collections research center, an undergraduate library, and several subject-specific libraries. More than three million volumes, including one million electronic books, are held at these locations. The Library houses the Amelia Earhart Collection, a collection of notes and letters belonging to Earhart and her husband George Putnam along with records related to her disappearance and subsequent search efforts. An administrative unit of Purdue University Libraries, Purdue University Press has its roots in the 1960 founding of Purdue University Studies by President Frederick Hovde on a $12,000 grant from the Purdue Research Foundation. This was the result of a committee appointed by President Hovde after the Department of English lamented the lack of publishing venues in the humanities. Since the 1990s, the range of books published by the Press has grown to reflect the work from other colleges at Purdue University especially in the areas of agriculture, health, and engineering. Purdue University Press publishes print and ebook monograph series in a range of subject areas from literary and cultural studies to the study of the human-animal bond. In 1993 Purdue University Press was admitted to membership of the Association of American University Presses. Purdue University Press publishes around 25 books a year and 20 learned journals in print, in print & online, and online-only formats in collaboration with Purdue University Libraries.

Sustainability

Purdue’s Sustainability Council, composed of University administrators and professors, meets monthly to discuss environmental issues and sustainability initiatives at Purdue. The University’s first LEED Certified building was an addition to the Mechanical Engineering Building, which was completed in Fall 2011. The school is also in the process of developing an arboretum on campus. In addition, a system has been set up to display live data detailing current energy production at the campus utility plant. The school holds an annual “Green Week” each fall, an effort to engage the Purdue community with issues relating to environmental sustainability.

Rankings

In its 2021 edition, U.S. News & World Report ranked Purdue University the 5th most innovative national university, tied for the 17th best public university in the United States, tied for 53rd overall, and 114th best globally. U.S. News & World Report also rated Purdue tied for 36th in “Best Undergraduate Teaching, 83rd in “Best Value Schools”, tied for 284th in “Top Performers on Social Mobility”, and the undergraduate engineering program tied for 9th at schools whose highest degree is a doctorate.

From The Massachusetts Institute of Technology Department of Nuclear Science & Engineering (NSE): “Mining valuable insights from diamonds”

From The Massachusetts Institute of Technology Department of Nuclear Science & Engineering (NSE)

May 31, 2022
Poornima Apte | Department of Nuclear Science and Engineering

“I’m focusing on the tiniest of things and there’s something really wonderful there,” says Changhao Li. “It’s about nature too, right? If you learn about how this tiny thing works, you can maybe also learn how the bigger things work.”
Photo: Gretchen Ertl.

If Changhao Li were to trace the origins of his love of nature, he would point to the time when he was 9, observing the night sky from his childhood home in the small town of Jinan, China. “At that moment I felt that nature is so beautiful, I just wanted to go outside the Earth, to go to the moon or even Mars,” Li remembers.

That childhood dream seeded his love of physics, which he pursued through middle and high school, and eventually at Xi’an Jiaotong University in China.

Li’s passion for the skies has since taken a more earthbound and microscopic form: It has translated into a love of quantum physics. Li is a fifth-year doctoral candidate in the Department of Nuclear Science and Engineering (NSE) and researches quantum information science, including quantum sensing and computation, with Professor Paola Cappellaro.

Quantum leaps

The primary thesis driving quantum information science is that altering the state of a material at a subatomic level can make a significant impact at much larger scales. Quantum computing, for example, depends on the most minute changes in material properties to store and process more information than a simple classical binary mode could.

The basic unit of information in quantum computing, equivalent to a bit in classical computers, is called a qubit. Exploiting defects in material structures is one way to manufacture these qubits.

An aspect of Li’s research focuses on defects in very small diamonds, some of which are on the nanometer scale. Experiments involve introducing an atomic-scale defect, known as nitrogen vacancy centers, in these diamonds, and subjecting the defects to extremely minute perturbations, using microwaves or lasers, to create and control quantum states.

One of Li’s projects measures the fluorescence emitted by a disturbed diamond to give us more information about the external stimulus. Just like you would measure an oven’s temperature to gauge how hot it is, measuring the fluorescence emitted by such a defective diamond can tell us what it is sensing and by how much. For example, a sensor that could detect even a few hundreds of strands of the SARS-CoV-2 virus that causes Covid-19 is one of the applications that Li is exploring with his colleagues.

In Physical Review Letters, Li has published findings from another research project which evaluates the symmetry of quantum systems. To explore the properties of quantum systems, we need to understand how the quantum states behave over time, and their symmetries are important. “Engineering a system with desired symmetry is a nontrivial task,” Li says. “Quantum properties are very unstable because they can interact with the environment. We need a very good lifetime for our qubits, and here we developed a method to control and characterize such a system.” Yet another research focus, the findings from which are soon to be published, focuses on simulation of a tensor gauge field using defects in diamonds, which is related with fundamental science.

Li says understanding quantum information is primarily about studying basic science. “The basic principles of this world are beautiful and can explain many interesting phenomena,” he points out. “This allows me to explore the universe, to understand how nature works,” Li adds.

The man who travels far knows more

A passion to understand how nature works, whether at the scale of stars or a small quantum unit, has galvanized Li’s interest in physics ever since he was a boy.

His parents encouraged his love of physics and a middle school teacher taught him to think critically, to spot errors in his textbooks and not swallow information as truths. “You need to run simple experiments to find the truth for yourself,” was the lesson that Li took away from middle school.

With that lesson safely tucked away, Li found high school to be a little more challenging and initially placed toward the middle of the nearly 1,000 students. But hard work and learning from others steered him toward the top.

Placing top of his class in both middle and high school, Li went on to pursue physics at Xi’an Jiaotong University, about 600 miles west of Beijing. It was his first time away from home, and he found his schooling needed a boost in topics like linear algebra. Again, hard work paid off and Li graduated top of his class.

University gave Li the ability to study in the United States for parts of his sophomore and junior years of college. Through exchange programs, Li attended University of Notre Dame for two months of summer research in 2015 and attended the University of California at Berkeley, during 2016, his junior year. The trips reinforced one of Li’s favorite quotes: “The man who travels far, knows more.”

Notre Dame was Li’s first time abroad — he remembers trying to get used to hamburgers and fries, a radical departure from the traditional Chinese food he loves.

It was research at Berkeley — he remembers the university library and dining halls fondly — that cemented his love of quantum physics. By the time he returned to China he knew he wanted to attend graduate school and pursue research in the field. MIT’s NSE beckoned as a chance to “work with the most brilliant people in the world,” Li says. Cappellaro is his inspiration — “she taught me how to think about research, I am very grateful,” he says.

Spare time finds Li relearning Chinese cooking — his parents do help with tips — and playing mobile games such as “Arena of Valor” with friends. Learning to play the guitar has been his pandemic hobby.

His fundamental love of nature, and in learning how things work, continues to inspire Li. “I’m focusing on the tiniest of things and there’s something really wonderful there. It’s about nature too, right? If you learn about how this tiny thing works, you can maybe also learn how the bigger things work,” Li says.

See the full article here .

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Please help promote STEM in your local schools.

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USPS “Forever” postage stamps celebrating Innovation at MIT.

The Massachusetts Institute of Technology is a private land-grant research university in Cambridge, Massachusetts. The institute has an urban campus that extends more than a mile (1.6 km) alongside the Charles River. The institute also encompasses a number of major off-campus facilities such as the MIT Lincoln Laboratory , the MIT Bates Research and Engineering Center , and the Haystack Observatory , as well as affiliated laboratories such as the Broad Institute of MIT and Harvard and Whitehead Institute.

Massachusettes Institute of Technology-Haystack Observatory Westford, Massachusetts, USA, Altitude 131 m (430 ft).

Founded in 1861 in response to the increasing industrialization of the United States, Massachusetts Institute of Technology adopted a European polytechnic university model and stressed laboratory instruction in applied science and engineering. It has since played a key role in the development of many aspects of modern science, engineering, mathematics, and technology, and is widely known for its innovation and academic strength. It is frequently regarded as one of the most prestigious universities in the world.

As of December 2020, 97 Nobel laureates, 26 Turing Award winners, and 8 Fields Medalists have been affiliated with MIT as alumni, faculty members, or researchers. In addition, 58 National Medal of Science recipients, 29 National Medals of Technology and Innovation recipients, 50 MacArthur Fellows, 80 Marshall Scholars, 3 Mitchell Scholars, 22 Schwarzman Scholars, 41 astronauts, and 16 Chief Scientists of the U.S. Air Force have been affiliated with The Massachusetts Institute of Technology . The university also has a strong entrepreneurial culture and MIT alumni have founded or co-founded many notable companies. Massachusetts Institute of Technology is a member of the Association of American Universities (AAU).

Foundation and vision

In 1859, a proposal was submitted to the Massachusetts General Court to use newly filled lands in Back Bay, Boston for a “Conservatory of Art and Science”, but the proposal failed. A charter for the incorporation of the Massachusetts Institute of Technology, proposed by William Barton Rogers, was signed by John Albion Andrew, the governor of Massachusetts, on April 10, 1861.

Rogers, a professor from the University of Virginia , wanted to establish an institution to address rapid scientific and technological advances. He did not wish to found a professional school, but a combination with elements of both professional and liberal education, proposing that:

“The true and only practicable object of a polytechnic school is, as I conceive, the teaching, not of the minute details and manipulations of the arts, which can be done only in the workshop, but the inculcation of those scientific principles which form the basis and explanation of them, and along with this, a full and methodical review of all their leading processes and operations in connection with physical laws.”

The Rogers Plan reflected the German research university model, emphasizing an independent faculty engaged in research, as well as instruction oriented around seminars and laboratories.

Early developments

Two days after The Massachusetts Institute of Technology was chartered, the first battle of the Civil War broke out. After a long delay through the war years, MIT’s first classes were held in the Mercantile Building in Boston in 1865. The new institute was founded as part of the Morrill Land-Grant Colleges Act to fund institutions “to promote the liberal and practical education of the industrial classes” and was a land-grant school. In 1863 under the same act, the Commonwealth of Massachusetts founded the Massachusetts Agricultural College, which developed as the University of Massachusetts Amherst ). In 1866, the proceeds from land sales went toward new buildings in the Back Bay.

The Massachusetts Institute of Technology was informally called “Boston Tech”. The institute adopted the European polytechnic university model and emphasized laboratory instruction from an early date. Despite chronic financial problems, the institute saw growth in the last two decades of the 19th century under President Francis Amasa Walker. Programs in electrical, chemical, marine, and sanitary engineering were introduced, new buildings were built, and the size of the student body increased to more than one thousand.

The curriculum drifted to a vocational emphasis, with less focus on theoretical science. The fledgling school still suffered from chronic financial shortages which diverted the attention of the MIT leadership. During these “Boston Tech” years, Massachusetts Institute of Technology faculty and alumni rebuffed Harvard University president (and former MIT faculty) Charles W. Eliot’s repeated attempts to merge MIT with Harvard College’s Lawrence Scientific School. There would be at least six attempts to absorb MIT into Harvard. In its cramped Back Bay location, MIT could not afford to expand its overcrowded facilities, driving a desperate search for a new campus and funding. Eventually, the MIT Corporation approved a formal agreement to merge with Harvard, over the vehement objections of MIT faculty, students, and alumni. However, a 1917 decision by the Massachusetts Supreme Judicial Court effectively put an end to the merger scheme.

In 1916, The Massachusetts Institute of Technology administration and the MIT charter crossed the Charles River on the ceremonial barge Bucentaur built for the occasion, to signify MIT’s move to a spacious new campus largely consisting of filled land on a one-mile-long (1.6 km) tract along the Cambridge side of the Charles River. The neoclassical “New Technology” campus was designed by William W. Bosworth and had been funded largely by anonymous donations from a mysterious “Mr. Smith”, starting in 1912. In January 1920, the donor was revealed to be the industrialist George Eastman of Rochester, New York, who had invented methods of film production and processing, and founded Eastman Kodak. Between 1912 and 1920, Eastman donated $20 million ($236.6 million in 2015 dollars) in cash and Kodak stock to MIT.

Curricular reforms

In the 1930s, President Karl Taylor Compton and Vice-President (effectively Provost) Vannevar Bush emphasized the importance of pure sciences like physics and chemistry and reduced the vocational practice required in shops and drafting studios. The Compton reforms “renewed confidence in the ability of the Institute to develop leadership in science as well as in engineering”. Unlike Ivy League schools, Massachusetts Institute of Technology catered more to middle-class families, and depended more on tuition than on endowments or grants for its funding. The school was elected to the Association of American Universities in 1934.

Still, as late as 1949, the Lewis Committee lamented in its report on the state of education at The Massachusetts Institute of Technology that “the Institute is widely conceived as basically a vocational school”, a “partly unjustified” perception the committee sought to change. The report comprehensively reviewed the undergraduate curriculum, recommended offering a broader education, and warned against letting engineering and government-sponsored research detract from the sciences and humanities. The School of Humanities, Arts, and Social Sciences and the MIT Sloan School of Management were formed in 1950 to compete with the powerful Schools of Science and Engineering. Previously marginalized faculties in the areas of economics, management, political science, and linguistics emerged into cohesive and assertive departments by attracting respected professors and launching competitive graduate programs. The School of Humanities, Arts, and Social Sciences continued to develop under the successive terms of the more humanistically oriented presidents Howard W. Johnson and Jerome Wiesner between 1966 and 1980.

The Massachusetts Institute of Technology‘s involvement in military science surged during World War II. In 1941, Vannevar Bush was appointed head of the federal Office of Scientific Research and Development and directed funding to only a select group of universities, including MIT. Engineers and scientists from across the country gathered at Massachusetts Institute of Technology ‘s Radiation Laboratory, established in 1940 to assist the British military in developing microwave radar. The work done there significantly affected both the war and subsequent research in the area. Other defense projects included gyroscope-based and other complex control systems for gunsight, bombsight, and inertial navigation under Charles Stark Draper’s Instrumentation Laboratory; the development of a digital computer for flight simulations under Project Whirlwind; and high-speed and high-altitude photography under Harold Edgerton. By the end of the war, The Massachusetts Institute of Technology became the nation’s largest wartime R&D contractor (attracting some criticism of Bush), employing nearly 4000 in the Radiation Laboratory alone and receiving in excess of $100 million ($1.2 billion in 2015 dollars) before 1946. Work on defense projects continued even after then. Post-war government-sponsored research at MIT included SAGE and guidance systems for ballistic missiles and Project Apollo.

These activities affected The Massachusetts Institute of Technology profoundly. A 1949 report noted the lack of “any great slackening in the pace of life at the Institute” to match the return to peacetime, remembering the “academic tranquility of the prewar years”, though acknowledging the significant contributions of military research to the increased emphasis on graduate education and rapid growth of personnel and facilities. The faculty doubled and the graduate student body quintupled during the terms of Karl Taylor Compton, president of The Massachusetts Institute of Technology between 1930 and 1948; James Rhyne Killian, president from 1948 to 1957; and Julius Adams Stratton, chancellor from 1952 to 1957, whose institution-building strategies shaped the expanding university. By the 1950s, The Massachusetts Institute of Technology no longer simply benefited the industries with which it had worked for three decades, and it had developed closer working relationships with new patrons, philanthropic foundations and the federal government.

In late 1960s and early 1970s, student and faculty activists protested against the Vietnam War and The Massachusetts Institute of Technology ‘s defense research. In this period Massachusetts Institute of Technology’s various departments were researching helicopters, smart bombs and counterinsurgency techniques for the war in Vietnam as well as guidance systems for nuclear missiles. The Union of Concerned Scientists was founded on March 4, 1969 during a meeting of faculty members and students seeking to shift the emphasis on military research toward environmental and social problems. The Massachusetts Institute of Technology ultimately divested itself from the Instrumentation Laboratory and moved all classified research off-campus to the MIT Lincoln Laboratory facility in 1973 in response to the protests. The student body, faculty, and administration remained comparatively unpolarized during what was a tumultuous time for many other universities. Johnson was seen to be highly successful in leading his institution to “greater strength and unity” after these times of turmoil. However six Massachusetts Institute of Technology students were sentenced to prison terms at this time and some former student leaders, such as Michael Albert and George Katsiaficas, are still indignant about MIT’s role in military research and its suppression of these protests. (Richard Leacock’s film, November Actions, records some of these tumultuous events.)

In the 1980s, there was more controversy at The Massachusetts Institute of Technology over its involvement in SDI (space weaponry) and CBW (chemical and biological warfare) research. More recently, The Massachusetts Institute of Technology’s research for the military has included work on robots, drones and ‘battle suits’.

Recent history

The Massachusetts Institute of Technology has kept pace with and helped to advance the digital age. In addition to developing the predecessors to modern computing and networking technologies, students, staff, and faculty members at Project MAC, the Artificial Intelligence Laboratory, and the Tech Model Railroad Club wrote some of the earliest interactive computer video games like Spacewar! and created much of modern hacker slang and culture. Several major computer-related organizations have originated at MIT since the 1980s: Richard Stallman’s GNU Project and the subsequent Free Software Foundation were founded in the mid-1980s at the AI Lab; the MIT Media Lab was founded in 1985 by Nicholas Negroponte and Jerome Wiesner to promote research into novel uses of computer technology; the World Wide Web Consortium standards organization was founded at the Laboratory for Computer Science in 1994 by Tim Berners-Lee; the MIT OpenCourseWare project has made course materials for over 2,000 Massachusetts Institute of Technology classes available online free of charge since 2002; and the One Laptop per Child initiative to expand computer education and connectivity to children worldwide was launched in 2005.

The Massachusetts Institute of Technology was named a sea-grant college in 1976 to support its programs in oceanography and marine sciences and was named a space-grant college in 1989 to support its aeronautics and astronautics programs. Despite diminishing government financial support over the past quarter century, MIT launched several successful development campaigns to significantly expand the campus: new dormitories and athletics buildings on west campus; the Tang Center for Management Education; several buildings in the northeast corner of campus supporting research into biology, brain and cognitive sciences, genomics, biotechnology, and cancer research; and a number of new “backlot” buildings on Vassar Street including the Stata Center. Construction on campus in the 2000s included expansions of the Media Lab, the Sloan School’s eastern campus, and graduate residences in the northwest. In 2006, President Hockfield launched the MIT Energy Research Council to investigate the interdisciplinary challenges posed by increasing global energy consumption.

In 2001, inspired by the open source and open access movements, The Massachusetts Institute of Technology launched OpenCourseWare to make the lecture notes, problem sets, syllabi, exams, and lectures from the great majority of its courses available online for no charge, though without any formal accreditation for coursework completed. While the cost of supporting and hosting the project is high, OCW expanded in 2005 to include other universities as a part of the OpenCourseWare Consortium, which currently includes more than 250 academic institutions with content available in at least six languages. In 2011, The Massachusetts Institute of Technology announced it would offer formal certification (but not credits or degrees) to online participants completing coursework in its “MITx” program, for a modest fee. The “edX” online platform supporting MITx was initially developed in partnership with Harvard and its analogous “Harvardx” initiative. The courseware platform is open source, and other universities have already joined and added their own course content. In March 2009 the Massachusetts Institute of Technology faculty adopted an open-access policy to make its scholarship publicly accessible online.

The Massachusetts Institute of Technology has its own police force. Three days after the Boston Marathon bombing of April 2013, MIT Police patrol officer Sean Collier was fatally shot by the suspects Dzhokhar and Tamerlan Tsarnaev, setting off a violent manhunt that shut down the campus and much of the Boston metropolitan area for a day. One week later, Collier’s memorial service was attended by more than 10,000 people, in a ceremony hosted by the Massachusetts Institute of Technology community with thousands of police officers from the New England region and Canada. On November 25, 2013, The Massachusetts Institute of Technology announced the creation of the Collier Medal, to be awarded annually to “an individual or group that embodies the character and qualities that Officer Collier exhibited as a member of The Massachusetts Institute of Technology community and in all aspects of his life”. The announcement further stated that “Future recipients of the award will include those whose contributions exceed the boundaries of their profession, those who have contributed to building bridges across the community, and those who consistently and selflessly perform acts of kindness”.

In September 2017, the school announced the creation of an artificial intelligence research lab called the MIT-IBM Watson AI Lab. IBM will spend $240 million over the next decade, and the lab will be staffed by MIT and IBM scientists. In October 2018 MIT announced that it would open a new Schwarzman College of Computing dedicated to the study of artificial intelligence, named after lead donor and The Blackstone Group CEO Stephen Schwarzman. The focus of the new college is to study not just AI, but interdisciplinary AI education, and how AI can be used in fields as diverse as history and biology. The cost of buildings and new faculty for the new college is expected to be $1 billion upon completion.

The Caltech/MIT Advanced aLIGO was designed and constructed by a team of scientists from California Institute of Technology , Massachusetts Institute of Technology, and industrial contractors, and funded by the National Science Foundation .

Caltech /MIT Advanced aLigo

It was designed to open the field of gravitational-wave astronomy through the detection of gravitational waves predicted by general relativity. Gravitational waves were detected for the first time by the LIGO detector in 2015. For contributions to the LIGO detector and the observation of gravitational waves, two Caltech physicists, Kip Thorne and Barry Barish, and Massachusetts Institute of Technology physicist Rainer Weiss won the Nobel Prize in physics in 2017. Weiss, who is also a Massachusetts Institute of Technology graduate, designed the laser interferometric technique, which served as the essential blueprint for the LIGO.

The mission of The Massachusetts Institute of Technology is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of The Massachusetts Institute of Technology community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

From The University of Cambridge (UK) Cavendish Laboratory – Department of Physics (UK): “One step closer to making terahertz technology usable in the real world”

From The University of Cambridge (UK) Cavendish Laboratory – Department of Physics

23/05/2022
Pooja Pandey

Wladislaw Michailow showing device in the cleanroom and A terahertz detector after fabrication. Credit: Wladislaw Michailow.

Researchers have discovered a new effect in two-dimensional conductive systems that promises improved performance of terahertz detectors.

A team of scientists at the Cavendish Laboratory together with colleagues at the Universities of Augsburg (Germany) and Lancaster has found a new physical effect when two-dimensional electron systems are exposed to terahertz waves.

First of all, what are terahertz waves? “We communicate using mobile phones that transmit microwave radiation and use infrared cameras for night vision. Terahertz is the type of electromagnetic radiation that lies in-between microwave and infrared radiation,” explains Prof David Ritchie, Head of the Semiconductor Physics Group at the Cavendish Laboratory of the University of Cambridge, “but at the moment, there is a lack of sources and detectors of this type of radiation, that would be cheap, efficient, and easy to use. This hinders the widespread use of terahertz technology.”

Researchers from the Semiconductor Physics group, together with researchers from Pisa and Torino in Italy, were the first to demonstrate, in 2002, the operation of a laser at terahertz frequencies, a quantum cascade laser. Since then the group has continued to research terahertz physics and technology and currently investigates and develops functional terahertz devices incorporating metamaterials to form modulators, as well as new types of detectors.

If the lack of usable devices were solved, terahertz radiation could have many useful applications in security, materials science, communications, and medicine. For example, terahertz waves allow the imaging of cancerous tissue that couldn’t be seen with the naked eye. They can be employed in new generations of safe and fast airport scanners that make it possible to distinguish medicines from illegal drugs and explosives, and they could be used to enable even faster wireless communications beyond the state-of-the-art.

So, what is the recent discovery about? “We were developing a new type of terahertz detector,” says Dr Wladislaw Michailow, Junior Research Fellow at Trinity College Cambridge, “but when measuring its performance, it turned out that it showed a much stronger signal than should be theoretically expected. So we came up with a new explanation.”

This explanation, as the scientists say, lies in the way how light interacts with matter. At high frequencies matter absorbs light in the form of single particles – photons. This interpretation, first proposed by Einstein, formed the foundation of quantum mechanics and was able to explain the photoelectric effect. This quantum photoexcitation is how light is detected by cameras in our smartphones; it is also what generates electricity from light in solar cells.

The well-known photoelectric effect consists of the release of electrons from a conductive material – a metal or a semiconductor – by incident photons. In the three-dimensional case, electrons can be expelled into vacuum by photons in the ultraviolet or x-ray range, or released into a dielectric in the mid-infrared to visible range. The novelty is in the discovery of a quantum photoexcitation process in the terahertz range, similar to the photoelectric effect. “The fact that such effects can exist within highly conductive, two-dimensional electron gases at much lower frequencies has not been understood so far,” explains Wladislaw, first author of the study, “but we have been able to prove this experimentally.” The quantitative theory of the effect was developed by a colleague from the University of Augsburg, Germany, and the international team of researchers published their findings in the reputable journal Science Advances.

The researchers called the phenomenon accordingly, as an “in-plane photoelectric effect”. In the corresponding paper, the scientists describe several benefits of exploiting this effect for terahertz detection. In particular, the magnitude of photoresponse that is generated by incident terahertz radiation by the “in-plane photoelectric effect” is much higher than expected from other mechanisms that have been heretofore known to give rise to a terahertz photoresponse. Thus, the scientists expect that this effect will enable fabrication of terahertz detectors with substantially higher sensitivity.

“This brings us one step closer to making terahertz technology usable in the real world.” concludes Prof Ritchie.

The work was supported by the EPSRC projects HyperTerahertz (no. EP/P021859/1) and grant no. EP/S019383/1, the Schiff Foundation of the University of Cambridge, Trinity College Cambridge, as well as the European Union’s Horizon 2020 research and innovation program Graphene Core 3 (grant no. 881603).

See the full article here .

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The Cavendish Laboratory is the Department of Physics at the University of Cambridge, and is part of the School of Physical Sciences. The laboratory was opened in 1874 on the New Museums Site as a laboratory for experimental physics and is named after the British chemist and physicist Henry Cavendish. The laboratory has had a huge influence on research in the disciplines of physics and biology.

As of 2019, 30 Cavendish researchers have won Nobel Prizes. Notable discoveries to have occurred at the Cavendish Laboratory include the discovery of the electron, neutron, and structure of DNA.

The Cavendish Laboratory was initially located on the New Museums Site, Free School Lane, in the centre of Cambridge. It is named after British chemist and physicist Henry Cavendish for contributions to science and his relative William Cavendish, 7th Duke of Devonshire, who served as chancellor of the university and donated funds for the construction of the laboratory.

Professor James Clerk Maxwell, the developer of electromagnetic theory, was a founder of the laboratory and the first Cavendish Professor of Physics. The Duke of Devonshire had given to Maxwell, as head of the laboratory, the manuscripts of Henry Cavendish’s unpublished Electrical Works. The editing and publishing of these was Maxwell’s main scientific work while he was at the laboratory. Cavendish’s work aroused Maxwell’s intense admiration and he decided to call the Laboratory (formerly known as the Devonshire Laboratory) the Cavendish Laboratory and thus to commemorate both the Duke and Henry Cavendish.

Physics

Several important early physics discoveries were made here, including the discovery of the electron by J.J. Thomson (1897); the Townsend discharge by John Sealy Townsend and the development of the cloud chamber by C.T.R. Wilson.

Ernest Rutherford became Director of the Cavendish Laboratory in 1919. Under his leadership the neutron was discovered by James Chadwick in 1932, and in the same year the first experiment to split the nucleus in a fully controlled manner was performed by students working under his direction; John Cockcroft and Ernest Walton.

Physical chemistry

Physical Chemistry (originally the department of Colloid Science led by Eric Rideal) had left the old Cavendish site, subsequently locating as the Department of Physical Chemistry (under RG Norrish) in the then new chemistry building with the Department of Chemistry (led by Lord Todd) in Lensfield Road: both chemistry departments merged in the 1980s.

Nuclear physics

In World War II the laboratory carried out research for the MAUD Committee, part of the British Tube Alloys project of research into the atomic bomb. Researchers included Nicholas Kemmer, Alan Nunn May, Anthony French, Samuel Curran and the French scientists including Lew Kowarski and Hans von Halban. Several transferred to Canada in 1943; the Montreal Laboratory and some later to the Chalk River Laboratories. The production of plutonium and neptunium by bombarding uranium-238 with neutrons was predicted in 1940 by two teams working independently: Egon Bretscher and Norman Feather at the Cavendish and Edwin M. McMillan and Philip Abelson at Berkeley Radiation Laboratory at The University of California-Berkeley (US).

Biology

The Cavendish Laboratory has had an important influence on biology, mainly through the application of X-ray crystallography to the study of structures of biological molecules. Francis Crick already worked in the Medical Research Council Unit, headed by Max Perutz and housed in the Cavendish Laboratory, when James Watson came from the United States and they made a breakthrough in discovering the structure of DNA. For their work while in the Cavendish Laboratory, they were jointly awarded the Nobel Prize in Physiology or Medicine in 1962, together with Maurice Wilkins of King’s College London (UK), himself a graduate of St. John’s College, Cambridge.

The discovery was made on 28 February 1953; the first Watson/Crick paper appeared in Nature on 25 April 1953. Sir Lawrence Bragg, the director of the Cavendish Laboratory, where Watson and Crick worked, gave a talk at Guy’s Hospital Medical School in London on Thursday 14 May 1953 which resulted in an article by Ritchie Calder in The News Chronicle of London, on Friday 15 May 1953, entitled Why You Are You. Nearer Secret of Life. The news reached readers of The New York Times the next day; Victor K. McElheny, in researching his biography, Watson and DNA: Making a Scientific Revolution, found a clipping of a six-paragraph New York Times article written from London and dated 16 May 1953 with the headline Form of `Life Unit’ in Cell Is Scanned. The article ran in an early edition and was then pulled to make space for news deemed more important. (The New York Times subsequently ran a longer article on 12 June 1953). The Cambridge University undergraduate newspaper Varsity also ran its own short article on the discovery on Saturday 30 May 1953. Bragg’s original announcement of the discovery at a Solvay Conference on proteins in Belgium on 8 April 1953 went unreported by the British press.

Sydney Brenner, Jack Dunitz, Dorothy Hodgkin, Leslie Orgel, and Beryl M. Oughton, were some of the first people in April 1953 to see the model of the structure of DNA, constructed by Crick and Watson; at the time they were working at The University of Oxford (UK)’s Chemistry Department. All were impressed by the new DNA model, especially Brenner who subsequently worked with Crick at Cambridge in the Cavendish Laboratory and the new Laboratory of Molecular Biology. According to the late Dr. Beryl Oughton, later Rimmer, they all travelled together in two cars once Dorothy Hodgkin announced to them that they were off to Cambridge to see the model of the structure of DNA. Orgel also later worked with Crick at The Salk Institute for Biological Studies (US).

The University of Cambridge (UK) [legally The Chancellor, Masters, and Scholars of the University of Cambridge] is a collegiate public research university in Cambridge, England. Founded in 1209 Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford(UK) after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

Cambridge is formed from a variety of institutions which include 31 semi-autonomous constituent colleges and over 150 academic departments, faculties and other institutions organised into six schools. All the colleges are self-governing institutions within the university, each controlling its own membership and with its own internal structure and activities. All students are members of a college. Cambridge does not have a main campus and its colleges and central facilities are scattered throughout the city. Undergraduate teaching at Cambridge is organised around weekly small-group supervisions in the colleges – a feature unique to the Oxbridge system. These are complemented by classes, lectures, seminars, laboratory work and occasionally further supervisions provided by the central university faculties and departments. Postgraduate teaching is provided predominantly centrally.

Cambridge University Press a department of the university is the oldest university press in the world and currently the second largest university press in the world. Cambridge Assessment also a department of the university is one of the world’s leading examining bodies and provides assessment to over eight million learners globally every year. The university also operates eight cultural and scientific museums, including the Fitzwilliam Museum, as well as a botanic garden. Cambridge’s libraries – of which there are 116 – hold a total of around 16 million books, around nine million of which are in Cambridge University Library, a legal deposit library. The university is home to – but independent of – the Cambridge Union – the world’s oldest debating society. The university is closely linked to the development of the high-tech business cluster known as “Silicon Fe”. It is the central member of Cambridge University Health Partners, an academic health science centre based around the Cambridge Biomedical Campus.

By both endowment size and consolidated assets Cambridge is the wealthiest university in the United Kingdom. In the fiscal year ending 31 July 2019, the central university – excluding colleges – had a total income of £2.192 billion of which £592.4 million was from research grants and contracts. At the end of the same financial year the central university and colleges together possessed a combined endowment of over £7.1 billion and overall consolidated net assets (excluding “immaterial” historical assets) of over £12.5 billion. It is a member of numerous associations and forms part of the ‘golden triangle’ of English universities.

Cambridge has educated many notable alumni including eminent mathematicians; scientists; politicians; lawyers; philosophers; writers; actors; monarchs and other heads of state. As of October 2020 121 Nobel laureates; 11 Fields Medalists; 7 Turing Award winners; and 14 British prime ministers have been affiliated with Cambridge as students; alumni; faculty or research staff. University alumni have won 194 Olympic medals.

History

By the late 12th century the Cambridge area already had a scholarly and ecclesiastical reputation due to monks from the nearby bishopric church of Ely. However it was an incident at Oxford which is most likely to have led to the establishment of the university: three Oxford scholars were hanged by the town authorities for the death of a woman without consulting the ecclesiastical authorities who would normally take precedence (and pardon the scholars) in such a case; but were at that time in conflict with King John. Fearing more violence from the townsfolk scholars from the University of Oxford started to move away to cities such as Paris; Reading; and Cambridge. Subsequently enough scholars remained in Cambridge to form the nucleus of a new university when it had become safe enough for academia to resume at Oxford. In order to claim precedence it is common for Cambridge to trace its founding to the 1231 charter from Henry III granting it the right to discipline its own members (ius non-trahi extra) and an exemption from some taxes; Oxford was not granted similar rights until 1248.

A bull in 1233 from Pope Gregory IX gave graduates from Cambridge the right to teach “everywhere in Christendom”. After Cambridge was described as a studium generale in a letter from Pope Nicholas IV in 1290 and confirmed as such in a bull by Pope John XXII in 1318 it became common for researchers from other European medieval universities to visit Cambridge to study or to give lecture courses.

Foundation of the colleges

The colleges at the University of Cambridge were originally an incidental feature of the system. No college is as old as the university itself. The colleges were endowed fellowships of scholars. There were also institutions without endowments called hostels. The hostels were gradually absorbed by the colleges over the centuries; but they have left some traces, such as the name of Garret Hostel Lane.

Hugh Balsham, Bishop of Ely, founded Peterhouse – Cambridge’s first college in 1284. Many colleges were founded during the 14th and 15th centuries but colleges continued to be established until modern times. There was a gap of 204 years between the founding of Sidney Sussex in 1596 and that of Downing in 1800. The most recently established college is Robinson built in the late 1970s. However Homerton College only achieved full university college status in March 2010 making it the newest full college (it was previously an “Approved Society” affiliated with the university).

In medieval times many colleges were founded so that their members would pray for the souls of the founders and were often associated with chapels or abbeys. The colleges’ focus changed in 1536 with the Dissolution of the Monasteries. Henry VIII ordered the university to disband its Faculty of Canon Law and to stop teaching “scholastic philosophy”. In response, colleges changed their curricula away from canon law and towards the classics; the Bible; and mathematics.

Nearly a century later the university was at the centre of a Protestant schism. Many nobles, intellectuals and even commoners saw the ways of the Church of England as too similar to the Catholic Church and felt that it was used by the Crown to usurp the rightful powers of the counties. East Anglia was the centre of what became the Puritan movement. In Cambridge the movement was particularly strong at Emmanuel; St Catharine’s Hall; Sidney Sussex; and Christ’s College. They produced many “non-conformist” graduates who, greatly influenced by social position or preaching left for New England and especially the Massachusetts Bay Colony during the Great Migration decade of the 1630s. Oliver Cromwell, Parliamentary commander during the English Civil War and head of the English Commonwealth (1649–1660), attended Sidney Sussex.

Modern period

After the Cambridge University Act formalised the organisational structure of the university the study of many new subjects was introduced e.g. theology, history and modern languages. Resources necessary for new courses in the arts architecture and archaeology were donated by Viscount Fitzwilliam of Trinity College who also founded the Fitzwilliam Museum. In 1847 Prince Albert was elected Chancellor of the University of Cambridge after a close contest with the Earl of Powis. Albert used his position as Chancellor to campaign successfully for reformed and more modern university curricula, expanding the subjects taught beyond the traditional mathematics and classics to include modern history and the natural sciences. Between 1896 and 1902 Downing College sold part of its land to build the Downing Site with new scientific laboratories for anatomy, genetics, and Earth sciences. During the same period the New Museums Site was erected including the Cavendish Laboratory which has since moved to the West Cambridge Site and other departments for chemistry and medicine.

The University of Cambridge began to award PhD degrees in the first third of the 20th century. The first Cambridge PhD in mathematics was awarded in 1924.

In the First World War 13,878 members of the university served and 2,470 were killed. Teaching and the fees it earned came almost to a stop and severe financial difficulties followed. As a consequence the university first received systematic state support in 1919 and a Royal Commission appointed in 1920 recommended that the university (but not the colleges) should receive an annual grant. Following the Second World War the university saw a rapid expansion of student numbers and available places; this was partly due to the success and popularity gained by many Cambridge scientists.

From “Quanta Magazine”: “Physicists Rewrite the Fundamental Law That Leads to Disorder”

From “Quanta Magazine”

May 26, 2022
Philip Ball

Is the rise of entropy merely probabilistic, or can it be straightened out by use of clear quantum axioms? Maggie Chiang for Quanta Magazine

The Second Law of Thermodynamics is among the most sacred in all of science, but it has always rested on 19th century arguments about probability. New arguments trace its true source to the flows of quantum information.

In all of physical law, there’s arguably no principle more sacrosanct than the Second Law of Thermodynamics — the notion that entropy, a measure of disorder, will always stay the same or increase. “If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations,” wrote the British astrophysicist Arthur Eddington in his 1928 book The Nature of the Physical World. “If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” No violation of this law has ever been observed, nor is any expected.

But something about the second law troubles physicists. Some are not convinced that we understand it properly or that its foundations are firm. Although it’s called a law, it’s usually regarded as merely probabilistic: It stipulates that the outcome of any process will be the most probable one (which effectively means the outcome is inevitable given the numbers involved).

Yet physicists don’t just want descriptions of what will probably happen. “We like laws of physics to be exact,” said the physicist Chiara Marletto of the University of Oxford. Can the second law be tightened up into more than just a statement of likelihoods?

A number of independent groups appear to have done just that. They may have woven the second law out of the fundamental principles of quantum mechanics — which, some suspect, have directionality and irreversibility built into them at the deepest level. According to this view, the second law comes about not because of classical probabilities but because of quantum effects such as entanglement. It arises from the ways in which quantum systems share information, and from cornerstone quantum principles that decree what is allowed to happen and what is not. In this telling, an increase in entropy is not just the most likely outcome of change. It is a logical consequence of the most fundamental resource that we know of — the quantum resource of information.

Quantum Inevitability

Thermodynamics was conceived in the early 19th century to describe the flow of heat and the production of work. The need for such a theory was urgently felt as steam power drove the Industrial Revolution, and engineers wanted to make their devices as efficient as possible.

In the end, thermodynamics wasn’t much help in making better engines and machinery. Instead, it became one of the central pillars of modern physics, providing criteria that govern all processes of change.

Classical thermodynamics has only a handful of laws, of which the most fundamental are the first and second. The first says that energy is always conserved; the second law says that heat always flows from hot to cold. More commonly this is expressed in terms of entropy, which must increase overall in any process of change. Entropy is loosely equated with disorder, but the Austrian physicist Ludwig Boltzmann formulated it more rigorously as a quantity related to the total number of microstates a system has: how many equivalent ways its particles can be arranged.

The second law appears to show why change happens in the first place. At the level of individual particles, the classical laws of motion can be reversed in time. But the second law implies that change must happen in a way that increases entropy. This directionality is widely considered to impose an arrow of time. In this view, time seems to flow from past to future because the universe began — for reasons not fully understood or agreed on — in a low-entropy state and is heading toward one of ever higher entropy. The implication is that eventually heat will be spread completely uniformly and there will be no driving force for further change — a depressing prospect that scientists of the mid-19th century called the heat death of the universe.

Boltzmann’s microscopic description of entropy seems to explain this directionality. Many-particle systems that are more disordered and have higher entropy vastly outnumber ordered, lower-entropy states, so molecular interactions are much more likely to end up producing them. The second law seems then to be just about statistics: It’s a law of large numbers. In this view, there’s no fundamental reason why entropy can’t decrease — why, for example, all the air molecules in your room can’t congregate by chance in one corner. It’s just extremely unlikely.

Yet this probabilistic statistical physics leaves some questions hanging. It directs us toward the most probable microstates in a whole ensemble of possible states and forces us to be content with taking averages across that ensemble.

But the laws of classical physics are deterministic — they allow only a single outcome for any starting point. Where, then, can that hypothetical ensemble of states enter the picture at all, if only one outcome is ever possible?

David Deutsch, a physicist at Oxford, has for several years been seeking to avoid this dilemma by developing a theory of (as he puts it) “a world in which probability and randomness are totally absent from physical processes.” His project, on which Marletto is now collaborating, is called “Constructor theory”. It aims to establish not just which processes probably can and can’t happen, but which are possible and which are forbidden outright.

Constructor theory aims to express all of physics in terms of statements about possible and impossible transformations. It echoes the way thermodynamics itself began, in that it considers change in the world as something produced by “machines” (constructors) that work in a cyclic fashion, following a pattern like that of the famous Carnot cycle, proposed in the 19th century to describe how engines perform work. The constructor is rather like a catalyst, facilitating a process and being returned to its original state at the end.

“Say you have a transformation like building a house out of bricks,” said Marletto. “You can think of a number of different machines that can achieve this, to different accuracies. All of these machines are constructors, working in a cycle” — they return to their original state when the house is built.

But just because a machine for conducting a certain task might exist, that doesn’t mean it can also undo the task. A machine for building a house might not be capable of dismantling it. This makes the operation of the constructor different from the operation of the dynamical laws of motion describing the movements of the bricks, which are reversible.

The reason for the irreversibility, said Marletto, is that for most complex tasks, a constructor is geared to a given environment. It requires some specific information from the environment relevant to completing that task. But the reverse task will begin with a different environment, so the same constructor won’t necessarily work. “The machine is specific to the environment it is working on,” she said.

Recently, Marletto, working with the quantum theorist Vlatko Vedral at Oxford and colleagues in Italy, showed that constructor theory does identify processes that are irreversible in this sense — even though everything happens according to quantum mechanical laws that are themselves perfectly reversible. “We show that there are some transformations for which you can find a constructor for one direction but not the other,” she said.

The researchers considered a transformation involving the states of quantum bits (qubits), which can exist in one of two states or in a combination, or superposition, of both. In their model, a single qubit B may be transformed from some initial, perfectly known state B1 to a target state B2 when it interacts with other qubits by moving past a row of them one qubit at a time. This interaction entangles the qubits: Their properties become interdependent, so that you can’t fully characterize one of the qubits unless you look at all the others too.

As the number of qubits in the row gets very large, it becomes possible to bring B into state B2 as accurately as you like, said Marletto. The process of sequential interactions of B with the row of qubits constitutes a constructor-like machine that transforms B1 to B2. In principle you can also undo the process, turning B2 back to B1, by sending B back along the row.

But what if, having done the transformation once, you try to reuse the array of qubits for the same process with a fresh B? Marletto and colleagues showed that if the number of qubits in the row is not very large and you use the same row repeatedly, the array becomes less and less able to produce the transformation from B1 to B2. But crucially, the theory also predicts that the row becomes even less able to do the reverse transformation from B2 to B1. The researchers have confirmed this prediction experimentally using photons for B and a fiber optic circuit to simulate a row of three qubits.

“You can approximate the constructor arbitrarily well in one direction but not the other,” Marletto said. There’s an asymmetry to the transformation, just like the one imposed by the second law. This is because the transformation takes the system from a so-called pure quantum state (B1) to a mixed one (B2, which is entangled with the row). A pure state is one for which we know all there is to be known about it. But when two objects are entangled, you can’t fully specify one of them without knowing everything about the other too. The fact is that it’s easier to go from a pure quantum state to a mixed state than vice versa — because the information in the pure state gets spread out by entanglement and is hard to recover. It’s comparable to trying to re-form a droplet of ink once it has dispersed in water, a process in which the irreversibility is imposed by the second law.

So here the irreversibility is “just a consequence of the way the system dynamically evolves,” said Marletto. There’s no statistical aspect to it. Irreversibility is not just the most probable outcome but the inevitable one, governed by the quantum interactions of the components. “Our conjecture,” said Marletto, “is that thermodynamic irreversibility might stem from this.”

Demon in the Machine

There’s another way of thinking about the second law, though, that was first devised by James Clerk Maxwell, the Scottish scientist who pioneered the statistical view of thermodynamics along with Boltzmann. Without quite realizing it, Maxwell connected the thermodynamic law to the issue of information.

Maxwell was troubled by the theological implications of a cosmic heat death and of an inexorable rule of change that seemed to undermine free will. So in 1867 he sought a way to “pick a hole” in the second law. In his hypothetical scenario, a microscopic being (later, to his annoyance, called a demon) turns “useless” heat back into a resource for doing work. Maxwell had previously shown that in a gas at thermal equilibrium there is a distribution of molecular energies. Some molecules are “hotter” than others — they are moving faster and have more energy. But they are all mixed at random so there appears to be no way to make use of those differences.

Enter Maxwell’s demon. It divides the compartment of gas in two, then installs a frictionless trapdoor between them. The demon lets the hot molecules moving about the compartments pass through the trapdoor in one direction but not the other. Eventually the demon has a hot gas on one side and a cooler one on the other, and it can exploit the temperature gradient to drive some machine.

The demon has used information about the motions of molecules to apparently undermine the second law. Information is thus a resource that, just like a barrel of oil, can be used to do work. But as this information is hidden from us at the macroscopic scale, we can’t exploit it. It’s this ignorance of the microstates that compels classical thermodynamics to speak of averages and ensembles.

Almost a century later, physicists proved that Maxwell’s demon doesn’t subvert the second law in the long term, because the information it gathers must be stored somewhere, and any finite memory must eventually be wiped to make room for more. In 1961 the physicist Rolf Landauer showed that this erasure of information can never be accomplished without dissipating some minimal amount of heat, thus raising the entropy of the surroundings. So the second law is only postponed, not broken.

The informational perspective on the second law is now being recast as a quantum problem. That’s partly because of the perception that quantum mechanics is a more fundamental description — Maxwell’s demon treats the gas particles as classical billiard balls, essentially. But it also reflects the burgeoning interest in quantum information theory itself. We can do things with information using quantum principles that we can’t do classically. In particular, entanglement of particles enables information about them to be spread around and manipulated in nonclassical ways.

Crucially, the quantum informational approach suggests a way of getting rid of the troublesome statistical picture that bedevils the classical view of thermodynamics, where you have to take averages over ensembles of many different microstates. “The true novelty with quantum information came with the understanding that one can replace ensembles with entanglement with the environment,” said Carlo Maria Scandolo of the University of Calgary.

Taking recourse in an ensemble, he said, reflects the fact that we have only partial information about the state — it could be this microstate or that one, with different probabilities, and so we have to average over a probability distribution. But quantum theory offers another way to generate states of partial information: through entanglement. When a quantum system gets entangled with its environment, about which we can’t know everything, some information about the system itself is inevitably lost: It ends up in a mixed state, where you can’t know everything about it even in principle by focusing on just the system.

Then you are forced to speak in terms of probabilities not because there are things about the system you don’t know, but because some of that information is fundamentally unknowable. In this way, “probabilities arise naturally from entanglement,” said Scandolo. “The whole idea of getting thermodynamic behavior by considering the role of the environment works only as long as there is entanglement.”

Those ideas have now been made precise. Working with Giulio Chiribella of the University of Hong Kong, Scandolo has proposed four axioms about quantum information that are required to obtain a “sensible thermodynamics” — that is, one not based on probabilities. The axioms describe constraints on the information in a quantum system that becomes entangled with its environment. In particular, everything that happens to the system plus environment is in principle reversible, just as is implied by the standard mathematical formulation of how a quantum system evolves in time.

As a consequence of these axioms, Scandolo and Chiribella show, uncorrelated systems always grow more correlated through reversible interactions. Correlations are what connect entangled objects: The properties of one are correlated with those of the other. They are measured by “mutual information,” a quantity that’s related to entropy. So a constraint on how correlations can change is also a constraint on entropy. If the entropy of the system decreases, the entropy of the environment must increase such that the sum of the two entropies can only increase or stay the same, but never decrease. In this way, Scandolo said, their approach derives the existence of entropy from the underlying axioms, rather than postulating it at the outset.

Redefining Thermodynamics

One of the most versatile ways to understand this new quantum version of thermodynamics invokes so-called resource theories — which again speak about which transformations are possible and which are not. “A resource theory is a simple model for any situation in which the actions you can perform and the systems you can access are restricted for some reason,” said the physicist Nicole Yunger Halpern of the National Institutes of Standards and Technology. (Scandolo has incorporated resource theories into his work too.)

Quantum resource theories adopt the picture of the physical world suggested by quantum information theory, in which there are fundamental limitations on which physical processes are possible. In quantum information theory these limitations are typically expressed as “no-go theorems”: statements that say “You can’t do that!” For example, it is fundamentally impossible to make a copy of an unknown quantum state, an idea called quantum no-cloning.

Resource theories have a few main ingredients. The operations that are allowed are called free operations. “Once you specify the free operations, you have defined the theory — and then you can start reasoning about which transformations are possible or not, and ask what are the optimal efficiencies with which we can perform these tasks,” said Yunger Halpern. A resource, meanwhile, is something that an agent can access to do something useful — it could be a pile of coal to fire up a furnace and power a steam engine. Or it could be extra memory that will allow a Maxwellian demon to subvert the second law for a little longer.

Quantum resource theories allow a kind of zooming in on the fine-grained details of the classical second law. We don’t need to think about huge numbers of particles; we can make statements about what is allowed among just a few of them. When we do this, said Yunger Halpern, it becomes clear that the classical second law (final entropy must be equal to or greater than initial entropy) is just a kind of coarse-grained sum of a whole family of inequality relationships. For instance, classically the second law says that you can transform a nonequilibrium state into one that is closer to thermal equilibrium. But “asking which of these states is closer to thermal is not a simple question,” said Yunger Halpern. To answer it, “we have to check a whole bunch of inequalities.”

In other words, in resource theories there seem to be a whole bunch of mini-second laws. “So there could be some transformations allowed by the conventional second law but forbidden by this more detailed family of inequalities,” said Yunger Halpern. For that reason, she adds, “sometimes I feel like everyone [in this field] has their own second law.”

The resource-theory approach, said physicist Markus Müller of the University of Vienna, “admits a fully mathematically rigorous derivation, without any conceptual or mathematical loose ends, of the thermodynamic laws and more.” He said that this approach involves “a reconsideration of what one really means by thermodynamics” — it is not so much about the average properties of large ensembles of moving particles, but about a game that an agent plays against nature to conduct a task efficiently with the available resources. In the end, though, it is still about information. The discarding of information — or the inability to keep track of it — is really the reason why the second law holds, Yunger Halpern said.

Hilbert’s Problem

All these efforts to rebuild thermodynamics and the second law recall a challenge laid down by the German mathematician David Hilbert. In 1900 he posed 23 outstanding problems in mathematics that he wanted to see solved. Item six in that list was “to treat, by means of axioms, those physical sciences in which already today mathematics plays an important part.” Hilbert was concerned that the physics of his day seemed to rest on rather arbitrary assumptions, and he wanted to see them made rigorous in the same way that mathematicians were attempting to derive fundamental axioms for their own discipline.

Some physicists today are still working on Hilbert’s sixth problem, attempting in particular to reformulate quantum mechanics and its more abstract version, quantum field theory, using axioms that are simpler and more physically transparent than the traditional ones. But Hilbert evidently had thermodynamics in mind too, referring to aspects of physics that use “the theory of probabilities” as among those ripe for reinvention.

Whether Hilbert’s sixth problem has yet been cracked for the second law seems to be a matter of taste. “I think Hilbert’s sixth problem is far from being completely solved, and I personally find it a very intriguing and important research direction in the foundations of physics,” said Scandolo. “There are still open problems, but I think they will be solved in the foreseeable future, provided enough time and energy are devoted to them.”

Maybe, though, the real value of re-deriving the second law lies not in satisfying Hilbert’s ghost but just in deepening our understanding of the law itself. As Einstein said, “A theory is the more impressive the greater the simplicity of its premises.” Yunger Halpern compares the motivation for working on the law to the reason literary scholars still reanalyze the plays and poems of Shakespeare: not because such new analysis is “more correct,” but because works this profound are an endless source of inspiration and insight.

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Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.