From The California Institute of Technology: “Randomness in Quantum Machines Helps Verify Their Accuracy”

From The California Institute of Technology

1.24.23
Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

New error-detection method takes advantage of the way quantum information is scrambled.

Researchers have discovered that complex random behaviors naturally emerge from even the simplest, chaotic dynamics in a quantum simulator. This illustration zooms into one such complex set of states within an apparently smooth quantum system. Credit: Adam Shaw.

In quantum computers and other experimental quantum systems, information spreads around the devices and quickly becomes scrambled like dice in a game of Boggle. This scrambling process happens as the basic units of the system, called qubits (like computer bits only quantum) become entangled with one another; entanglement is a phenomenon in quantum physics where particles link up with each other and remain connected even though they are not in direct contact.

These quantum devices mimic what happens in nature and allow scientists to develop new, exotic materials that are potentially useful in medicine, computer electronics, and other fields. While full-scale quantum computers are still years away, researchers are already performing experiments on so-called “quantum simulators”: quantum devices tailored to solve specific problems, such as efficiently simulating high-temperature superconductors and other quantum materials. The machines could also solve complex optimization problems, such as planning routes for autonomous vehicles to ensure they don’t collide.

One challenge in using these quantum machines is that they are very prone to errors, much more so than classical computers. It is also much harder to identify errors in these newer systems. “For the most part, quantum computers make a lot of mistakes,” says Adam Shaw, a Caltech graduate student in physics and one of two lead authors of a study in the journal Nature about a new method to verify the accuracy of quantum devices. “You cannot open the machine and look inside, and there is a huge amount of information being stored—too much for a classical computer to account for and verify.”

In the Nature study [below], Shaw and co-lead author Joonhee Choi, a former postdoctoral scholar at Caltech who is now a professor at Stanford University, demonstrate a novel way to measure a quantum device’s accuracy, also known as fidelity. Both researchers work in the laboratory of Manuel Endres, a professor of physics at Caltech and a Rosenberg scholar. The key to their new strategy is randomness. The scientists have discovered and characterized a newfound type of randomness pertaining to the way information is scrambled in the quantum systems. But even though the quantum behavior is random, universal statistical patterns can be identified in the noise.

“We are interested in better understanding what happens when the information is scrambled,” Choi says. “And by analyzing this behavior with statistics, we can look for deviations in the patterns that indicate errors have been made.”

“We don’t want just a result from our quantum machines; we want a verified result,” Endres says. “Because of quantum chaos, a single microscopic error leads to a completely different macroscopic outcome, quite similar to the butterfly effect. This enables us to detect the error efficiently.”

The researchers demonstrated their protocol on a quantum simulator with as many as 25 qubits. To find whether errors have occurred, they measured the behavior of the system down to the single qubit level thousands of times. By looking at how qubits evolved over time, the researchers could identify patterns in the seemingly random behavior and then look for deviations from what they expected. Ultimately, by finding errors, researchers will know how and when to fix them.

“We can trace how information moves across a system with single qubit resolution,” Choi says. “The reason we can do this is that we also discovered that this randomness, which just happens naturally, is represented at the level of just one qubit. You can see the universal random pattern in the subparts of the system.”

Shaw compares their work to measuring the choppiness of waves on a lake. “If a wind comes, you’ll get peaks and troughs on the lake, and while it may look random, one could identify a pattern to the randomness and track how the wind affects the water. We would be able to tell if the wind changes by analyzing how the pattern changes. Our new method similarly allows us to look for changes in the quantum system that would indicate errors.”

The Nature study is funded by the National Science Foundation via the Institute for Quantum Information and Matter, or IQIM; the Defense Advanced Research Projects Agency (DARPA); the Army Research Office, the Eddleman Quantum Institute graduate fellowship; the Troesh postdoctoral fellowship; the Gordon and Betty Moore Foundation; the J. Yang & Family Foundation; the Harvard Quantum Initiative (HQI) graduate fellowship; the Junior Fellowship from the Harvard Society of Fellows; the Department of Energy; and the Miller Institute for Basic Research in Science at UC-Berkeley. Other authors include Ran Finkelstein, Hsin-Yuan Huang, and Fernando Brandão of Caltech; Ivaylo Madjarov, Xin Xie, and Jacob Covey, who performed the research while previously at Caltech; Jordan Cotler and Anant Kale of Harvard University; Daniel Mark and Soonwon Choi of MIT; and Hannes Pichler of University of Innsbruck in Austria.

Nature
See the science paper for instructive material with images.

See the full article here .

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Caltech campus

The California Institute of Technology is a private research university in Pasadena, California. The university is known for its strength in science and engineering, and is one among a small group of institutes of technology in the United States which is primarily devoted to the instruction of pure and applied sciences.

The California Institute of Technology was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910 and the college assumed its present name in 1920. In 1934, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology has six academic divisions with strong emphasis on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. First-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at The California Institute of Technology. Although The California Institute of Technology has a strong tradition of practical jokes and pranks, student life is governed by an honor code which allows faculty to assign take-home examinations. The The California Institute of Technology Beavers compete in 13 intercollegiate sports in the NCAA Division III’s Southern California Intercollegiate Athletic Conference (SCIAC).

As of October 2020, there are 76 Nobel laureates who have been affiliated with The California Institute of Technology, including 40 alumni and faculty members (41 prizes, with chemist Linus Pauling being the only individual in history to win two unshared prizes). In addition, 4 Fields Medalists and 6 Turing Award winners have been affiliated with The California Institute of Technology. There are 8 Crafoord Laureates and 56 non-emeritus faculty members (as well as many emeritus faculty members) who have been elected to one of the United States National Academies. Four Chief Scientists of the U.S. Air Force and 71 have won the United States National Medal of Science or Technology. Numerous faculty members are associated with the Howard Hughes Medical Institute as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology is classified among “R1: Doctoral Universities – Very High Research Activity”. Caltech was elected to The Association of American Universities in 1934 and remains a research university with “very high” research activity, primarily in STEM fields. The largest federal agencies contributing to research are National Aeronautics and Space Administration; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology had 739,000 square feet (68,700 m^2) dedicated to research: 330,000 square feet (30,700 m^2) to physical sciences, 163,000 square feet (15,100 m^2) to engineering, and 160,000 square feet (14,900 m^2) to biological sciences.

In addition to managing NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; The Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology in 2006; the Keck Institute for Space Studies in 2008; and is also the current home for the Einstein Papers Project. The Spitzer Science Center, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

Caltech Palomar Observatory. Credit:The California Institute of Technology, Altitude 1,713 m (5,620 ft), located in San Diego County, California.

California Institute of Technology The Owens Valley Radio Observatory, Owens Valley, California, Altitude 1,222 m (4,009 ft). Credit: Caltech.

W.M. Keck Observatory two ten meter telescopes operated by California Institute of Technology and The University of California, at Mauna Kea Observatory, Hawai’i, altitude 4,207 m (13,802 ft). Credit: Caltech.

Caltech /MIT Advanced aLigo. Credit: Caltech.

Caltech/MIT Advanced aLigo Hanford, WA installation. Credit: Caltech.

Caltech/MIT Advanced aLigo detector installation Livingston, LA. Credit: Caltech.

The California Institute of Technology partnered with University of California at Los Angeles to establish a Joint Center for Translational Medicine (UCLA-Caltech JCTM), which conducts experimental research into clinical applications, including the diagnosis and treatment of diseases such as cancer.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

From The Australian National University (AU): “New techniques for accurate measurements of tiny objects”

From The Australian National University (AU)

1.13.23

New research led by a team of scientists at The Australian National University (ANU) has outlined a way to achieve more accurate measurements of microscopic objects using quantum computers – a step that could prove useful in a huge range of next-generation technologies, including biomedical sensing.

Experimental implementation of optimal collective measurements using quantum computers. a,b, Probe states are sent to the quantum computers (QC) individually for the single-copy measurement (a) and in pairs for the two-copy measurement (b). c,d, The qubit probes experience rotations, θx and θy, about the x and y axes of the Bloch sphere (c) before undergoing decoherence that has the effect of shrinking the Bloch vector (d). This rotation can be thought of as being caused by an external magnetic field that we wish to sense. e,f, The QCs then implement quantum circuits corresponding to the optimal single-copy (e) and two-copy (f) measurements. Two optimal single-copy circuits are shown, one for estimating θx and one for θy. g, Finally, error mitigation is used to improve the accuracy of the estimated angle. We create a model (green line) for how the noisy estimate of θ, θ^noisy (black dots), is related to the true value (red line). The model is then used to correct θ^noisy to produce the final estimate θ^θ^. Sample data from the F-IBM QS1 device downsampled by a factor of three are shown in g. Error bars are smaller than the markers. Credit: Nature Physics (2023).

Lead author and ANU PhD researcher Lorcán Conlon and co-author Dr Syed Assad.

Examining the various individual properties of a large everyday object like a car is fairly simple: a car has a well-defined position, colour and speed. However, this becomes much trickier when trying to examine microscopic quantum objects like photons – tiny little particles of light.

That’s because certain properties of quantum objects are connected and measuring one property can disturb another property. For example, measuring the position of an electron will affect its speed and vice versa.

Such properties are called conjugate properties. This is a direct manifestation of Heisenberg’s famous uncertainty principle- it is not possible to simultaneously measure two conjugate properties of a quantum object with arbitrary accuracy.

According to lead author and ANU PhD researcher Lorcán Conlon, this is one of the defining challenges of quantum mechanics.

“We were able to design a measurement to determine conjugate properties of quantum objects more accurately. Remarkably, our collaborators were able to implement this measurement in various labs around the world,” Mr Conlon said.

“More accurate measurements are crucial, and can in turn open up new possibilities for all sorts of technologies, including biomedical sensing, laser ranging, and quantum communications.”

The new technique revolves around a strange quirk of quantum systems, known as entanglement. According to the researchers, by entangling two identical quantum objects and measuring them together, scientists can determine their properties more precisely than if they were measured individually.

“By entangling two identical quantum systems, we can acquire more information,” co-author Dr Syed Assad said. “There is some unavoidable noise associated with measuring any property of a quantum system. By entangling the two, we’re able to reduce this noise and get a more accurate measurement.”

In theory it is possible to entangle and measure three or more quantum systems to achieve even better precision, but in this case the experiments failed to agree with the theory. Nevertheless, the authors are confident that future quantum computers will be able to overcome these limitations.

“Quantum computers with error-corrected qubits will be able to gainfully measure with more and more copies in the future,” Mr Lorcan Conlon said.

According to Professor Ping Koy Lam, A*STAR chief quantum scientist at Institute of Materials Research and Engineering (IMRE), one of the key strengths of this work is that a quantum-enhancement can still be observed in noisy scenarios.

“For practical applications, such as in biomedical measurements, it is important that we can see an advantage even when the signal is inevitably embedded in a noisy real-world environment,” he said.

The study was conducted by experts at the ARC Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), in collaboration with researchers from A*STAR’s Institute of Materials Research and Engineering (IMRE), the University of Jena, the University of Innsbruck, and Macquarie University. Amazon Web Services collaborated by providing research and architectural support, and by making available the Rigetti Aspen-9 device using Amazon Braket.

The researchers tested their theory on 19 different quantum computers, across three different platforms: superconducting, trapped ion and photonic quantum computers. These world leading devices are located across Europe and America and are cloud-accessible, allowing researchers from across the globe to connect and carry out important research.

The research has been published in Nature Physics [ https://www.nature.com/articles/s41567-022-01875-7 ] .

See the full article here .

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The Australian National University (AU) is a world-leading university in Australia’s capital city, Canberra. Our location points to our unique history, ties to the Australian Government and special standing as a resource for the Australian people.

Our focus on research as an asset, and an approach to education, ensures our graduates are in demand the world-over for their abilities to understand, and apply vision and creativity to addressing complex contemporary challenges.

Australian National University (AU) is regarded as one of the world’s leading research universities, and is ranked as the number one university in Australia and the Southern Hemisphere by the 2021 QS World University Rankings. It is ranked 31st in the world by the 2021 QS World University Rankings, and 59th in the world (third in Australia) by the 2021 Times Higher Education.

In the 2020 Times Higher Education Global Employability University Ranking, an annual ranking of university graduates’ employability, Australian National University (AU) was ranked 15th in the world (first in Australia). According to the 2020 QS World University by Subject, the university was also ranked among the top 10 in the world for Anthropology, Earth and Marine Sciences, Geography, Geology, Philosophy, Politics, and Sociology.

Established in 1946, ANU is the only university to have been created by the Parliament of Australia. It traces its origins to Canberra University College, which was established in 1929 and was integrated into Australian National University (AU) in 1960. Australian National University (AU) enrolls 10,052 undergraduate and 10,840 postgraduate students and employs 3,753 staff. The university’s endowment stood at A$1.8 billion as of 2018.

Australian National University (AU) counts six Nobel laureates and 49 Rhodes scholars among its faculty and alumni. The university has educated two prime ministers, 30 current Australian ambassadors and more than a dozen current heads of government departments of Australia. The latest releases of ANU’s scholarly publications are held through ANU Press online.

From The Massachusetts Institute of Technology: “New quantum computing architecture could be used to connect large-scale devices”

From The Massachusetts Institute of Technology

1.5.23
Adam Zewe

This image shows a module composed of superconducting qubits that can be used to directionally emit microwave photons.
Image: Krantz NanoArt.

Researchers have demonstrated directional photon emission-the first step toward extensible quantum interconnects.

Quantum computers hold the promise of performing certain tasks that are intractable even on the world’s most powerful supercomputers. In the future, scientists anticipate using quantum computing to emulate materials systems, simulate quantum chemistry, and optimize hard tasks, with impacts potentially spanning finance to pharmaceuticals.

However, realizing this promise requires resilient and extensible hardware. One challenge in building a large-scale quantum computer is that researchers must find an effective way to interconnect quantum information nodes — smaller-scale processing nodes separated across a computer chip. Because quantum computers are fundamentally different from classical computers, conventional techniques used to communicate electronic information do not directly translate to quantum devices. However, one requirement is certain: Whether via a classical or a quantum interconnect, the carried information must be transmitted and received.

To this end, MIT researchers have developed a quantum computing architecture that will enable extensible and high-fidelity communication between superconducting quantum processors. In work published today in Nature Physics [below], MIT researchers demonstrate step one, the deterministic emission of single photons — information carriers — in a user-specified direction. Their method ensures quantum information flows in the correct direction more than 96 percent of the time.

Linking several of these modules enables a larger network of quantum processors that are interconnected with one another no matter their physical separation on a computer chip.

“Quantum interconnects are a crucial step toward modular implementations of larger-scale machines built from smaller individual components,” says Bharath Kannan PhD ’22, co-lead author of a research paper describing this technique.

“The ability to communicate between smaller subsystems will enable a modular architecture for quantum processors, and this may be a simpler way of scaling to larger system sizes compared to the brute-force approach of using a single large and complicated chip,” Kannan adds.

Kannan wrote the paper with co-lead author Aziza Almanakly, an Electrical Engineering and Computer Science graduate student in the Engineering Quantum Systems group of the Research Laboratory of Electronics (RLE) at MIT. The senior author is William D. Oliver, an MIT professor of Electrical Engineering and Computer Science and of Physics, an MIT Lincoln Laboratory Fellow, director of the Center for Quantum Engineering, and associate director of RLE.

Moving quantum information

In a conventional classical computer, various components perform different functions, such as memory, computation, etc. Electronic information, encoded and stored as bits (which take the value of 1s or 0s), is shuttled between these components using interconnects, which are wires that move electrons around on a computer processor.

But quantum information is more complex. Instead of only holding a value of 0 or 1, quantum information can also be both 0 and 1 simultaneously (a phenomenon known as superposition). Also, quantum information can be carried by particles of light, called photons. These added complexities make quantum information fragile, and it can’t be transported simply using conventional protocols.

A quantum network links processing nodes using photons that travel through special interconnects known as “waveguides”. A waveguide can either be unidirectional, and move a photon only to the left or to the right, or it can be bidirectional.

Most existing architectures use unidirectional waveguides, which are easier to implement since the direction in which photons travel is easily established. But since each waveguide only moves photons in one direction more waveguides become necessary as the quantum network expands, which makes this approach difficult to scale. In addition, unidirectional waveguides usually incorporate additional components to enforce the directionality, which introduces communication errors.

“We can get rid of these lossy components if we have a waveguide that can support propagation in both the left and right directions, and a means to choose the direction at will. This ‘directional transmission’ is what we demonstrated, and it is the first step toward bidirectional communication with much higher fidelities,” says Kannan.

Using their architecture, multiple processing modules can be strung along one waveguide. A remarkable feature the architecture design is that the same module can be used as both a transmitter and a receiver, he says. And photons can be sent and captured by any two modules along a common waveguide.

“We have just one physical connection that can have any number of modules along the way. This is what makes it scalable. Having demonstrated directional photon emission from one module, we are now working on capturing that photon downstream at a second module,” Almanakly adds.

Leveraging quantum properties

To accomplish this, the researchers built a module comprising four qubits.

Qubits are the building blocks of quantum computers, and are used to store and process quantum information. But qubits can also be used as photon emitters. Adding energy to a qubit causes the qubit to become excited, and then when it de-excites, the qubit will emit the energy in the form of a photon.

However, simply connecting one qubit to a waveguide does not ensure directionality. A single qubit emits a photon, but whether it travels to the left or to the right is completely random. To circumvent this problem, the researchers utilize two qubits and a property known as quantum interference to ensure the emitted photon travels in the correct direction.

The technique involves preparing the two qubits in an entangled state of single excitation called a “Bell state”. This quantum-mechanical state comprises two aspects: the left qubit being excited and the right qubit being excited. Both aspects exist simultaneously, but which qubit is excited at a given time is unknown.

When qubits are in this entangled “Bell state” a photon is effectively emitted to the waveguide at the two qubit locations simultaneously, and these two “emission paths” interfere with each other. Depending on the relative phase within the Bell state, the resulting photon emission must travel to the left or to the right. By preparing the Bell state with the correct phase, the researchers choose the direction in which the photon travels through the waveguide.

They can use this same technique, but in reverse, to receive the photon at another module.

“The photon has a certain frequency, a certain energy, and you can prepare a module to receive it by tuning it to the same frequency. If they are not at the same frequency, then the photon will just pass by. It’s analogous to tuning a radio to a particular station. If we choose the right radio frequency, we’ll pick up the music transmitted at that frequency,” Almanakly says.

The researchers found that their technique achieved more than 96 percent fidelity — this means that if they intended to emit a photon to the right, 96 percent of the time it went to the right.

Now that they have used this technique to effectively emit photons in a specific direction, the researchers want to connect multiple modules and use the process to emit and absorb photons. This would be a major step toward the development of a modular architecture that combines many smaller-scale processors into one larger-scale, and more powerful, quantum processor.

“The work demonstrates an on-demand quantum emitter, in which the interference of the emitted photon from an entangled state defines the direction, beautifully manifesting the power of waveguide quantum electrodynamics,” says Yasunobu Nakamura, director of the RIKEN Center for Quantum Computing, who was not involved with this research. “It can be used as a fully programmable quantum node that can emit/absorb/pass/store quantum information on a quantum network and as an interface for a bus connecting multiple quantum computer chips.”

The research is funded, in part, by the AWS Center for Quantum Computing, the U.S. Army Research Office, the U.S. Department of Energy Office of Science National Quantum Information Science Research Centers, the Co-design Center for Quantum Advantage, and the U.S. Department of Defense.

Science paper:
Nature Physics

See the full article here .

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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.

MIT Lincoln Laboratory campus

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

The Computer Science and Artificial Intelligence Laboratory (CSAIL)

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.

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 California Institute of Technology: “Physicists observe wormhole dynamics using a quantum computer”

From The California Institute of Technology

11.30.22
Whitney Clavin
(626) 395‑1944
wclavin@caltech.edu

Artwork depicting a quantum experiment that studies traversable wormholes. Credit: inqnet/A. Mueller (Caltech)

The research is a step toward studying “quantum gravity” in the lab.

Scientists have, for the first time, developed a quantum experiment that allows them to study the dynamics, or behavior, of a special kind of theoretical wormhole. The experiment has not created an actual wormhole (a rupture in space and time), rather it allows researchers to probe connections between theoretical wormholes and quantum physics, a prediction of so-called quantum gravity. Quantum gravity refers to a set of theories that seek to connect gravity with quantum physics, two fundamental and well-studied descriptions of nature that appear inherently incompatible with each other.

“We found a quantum system that exhibits key properties of a gravitational wormhole yet is sufficiently small to implement on today’s quantum hardware,” says Maria Spiropulu, the principal investigator of the U.S. Department of Energy Office of Science research program Quantum Communication Channels for Fundamental Physics (QCCFP) and the Shang-Yi Ch’en Professor of Physics at Caltech. “This work constitutes a step toward a larger program of testing quantum gravity physics using a quantum computer. It does not substitute for direct probes of quantum gravity in the same way as other planned experiments that might probe quantum gravity effects in the future using quantum sensing, but it does offer a powerful testbed to exercise ideas of quantum gravity.”

The research will be published December 1 in the journal Nature [below]. The study’s first authors are Daniel Jafferis of Harvard University and Alexander Zlokapa (BS ’21), a former undergraduate student at Caltech who started on this project for his bachelor’s thesis with Spiropulu and has since moved on to graduate school at MIT.

Wormholes are bridges between two remote regions in spacetime. They have not been observed experimentally, but scientists have theorized about their existence and properties for close to 100 years. In 1935, Albert Einstein and Nathan Rosen described wormholes as tunnels through the fabric of spacetime in accordance with Einstein’s General Theory of Relativity, which describes gravity as a curvature of spacetime. Researchers call wormholes “Einstein–Rosen bridges” after the two physicists who invoked them, while the term “wormhole” itself was coined by physicist John Wheeler in the 1950s.

The notion that wormholes and quantum physics, specifically entanglement (a phenomenon in which two particles can remain connected across vast distances), may have a connection was first proposed in theoretical research by Juan Maldacena and Leonard Susskind in 2013. The physicists speculated that wormholes (or “ER”) were equivalent to entanglement (also known as “EPR” after Albert Einstein, Boris Podolsky [PhD ’28], and Nathan Rosen, who first proposed the concept). In essence, this work established a new kind of theoretical link between the worlds of gravity and quantum physics. “It was a very daring and poetic idea,” says Spiropulu of the “ER = EPR” work.

Later, in 2017, Jafferis, along with his colleagues Ping Gao and Aron Wall, extended the “ER = EPR” idea to not just wormholes but traversable wormholes. The scientists concocted a scenario in which negative repulsive energy holds a wormhole open long enough for something to pass through from one end to the other. The researchers showed that this gravitational description of a traversable wormhole is equivalent to a process known as quantum teleportation. In quantum teleportation, a protocol that has been experimentally demonstrated over long distances via optical fiber and over the air, information is transported across space using the principles of quantum entanglement.

The present work explores the equivalence of wormholes with quantum teleportation. The Caltech-led team performed the first experiments that probe the idea that information traveling from one point in space to another can be described in either the language of gravity (the wormholes) or the language of quantum physics (quantum entanglement).

A key finding that inspired possible experiments occurred in 2015, when Caltech’s Alexei Kitaev, the Ronald and Maxine Linde Professor of Theoretical Physics and Mathematics, showed that a simple quantum system could exhibit the same duality later described by Gao, Jafferis, and Wall, such that the model’s quantum dynamics are equivalent to quantum gravity effects. This Sachdev–Ye–Kitaev, or SYK model (named after Kitaev, and Subir Sachdev and Jinwu Ye, two other researchers who worked on its development previously) led researchers to suggest that some theoretical wormhole ideas could be studied more deeply by doing experiments on quantum processors.

Furthering these ideas, in 2019, Jafferis and Gao showed that by entangling two “SYK” models, researchers should be able to perform wormhole teleportation and thus produce and measure the dynamical properties expected of traversable wormholes.

In the new study, the team of physicists performed this type of experiment for the first time. They used a “baby” “SYK”-like model prepared to preserve gravitational properties, and they observed the wormhole dynamics on a quantum device at Google, namely the Sycamore quantum processor.

Google 53-qubit “Sycamore” superconducting processor quantum computer.

To accomplish this, the team had to first reduce the “SYK” model to a simplified form, a feat they achieved using machine learning tools on conventional computers.

“We employed learning techniques to find and prepare a simple “SYK”-like quantum system that could be encoded in the current quantum architectures and that would preserve the gravitational properties,” says Spiropulu. “In other words, we simplified the microscopic description of the “SYK’ quantum system and studied the resulting effective model that we found on the quantum processor. It is curious and surprising how the optimization on one characteristic of the model preserved the other metrics! We have plans for more tests to get better insights on the model itself.”

In the experiment, the researchers inserted a qubit—the quantum equivalent of a bit in conventional silicon-based computers—into one of their “SYK”-like systems and observed the information emerge from the other system. The information traveled from one quantum system to the other via quantum teleportation—or, speaking in the complementary language of gravity, the quantum information passed through the traversable wormhole.

“We performed a kind of quantum teleportation equivalent to a traversable wormhole in the gravity picture. To do this, we had to simplify the quantum system to the smallest example that preserves gravitational characteristics so we could implement it on the Sycamore quantum processor at Google,” says Zlokapa.

Co-author Samantha Davis, a graduate student at Caltech, adds, “It took a really long time to arrive at the results, and we surprised ourselves with the outcome.”

“The near-term significance of this type of experiment is that the gravitational perspective provides a simple way to understand an otherwise mysterious many-particle quantum phenomenon,” says John Preskill, the Richard P. Feynman Professor of Theoretical Physics at Caltech and director of the Institute for Quantum Information and Matter (IQIM). “What I found interesting about this new Google experiment is that, via machine learning, they were able to make the system simple enough to simulate on an existing quantum machine while retaining a reasonable caricature of what the gravitation picture predicts.”

In the study, the physicists report wormhole behavior expected both from the perspectives of gravity and from quantum physics. For example, while quantum information can be transmitted across the device, or teleported, in a variety of ways, the experimental process was shown to be equivalent, at least in some ways, to what might happen if information traveled through a wormhole. To do this, the team attempted to “prop open the wormhole” using pulses of either negative repulsive energy pulse or the opposite, positive energy. They observed key signatures of a traversable wormhole only when the equivalent of negative energy was applied, which is consistent with how wormholes are expected to behave.

“The high fidelity of the quantum processor we used was essential,” says Spiropulu. “If the error rates were higher by 50 percent, the signal would have been entirely obscured. If they were half we would have 10 times the signal!”

In the future, the researchers hope to extend this work to more complex quantum circuits. Though bona fide quantum computers may still be years away, the team plans to continue to perform experiments of this nature on existing quantum computing platforms.

“The relationship between quantum entanglement, spacetime, and quantum gravity is one of the most important questions in fundamental physics and an active area of theoretical research,” says Spiropulu. “We are excited to take this small step toward testing these ideas on quantum hardware and will keep going.”

More information can be found at the Alliance for Quantum Technologies website: https://inqnet.caltech.edu/wormhole2022.

Science paper:
Nature

See the full article here .

Comments are invited and will be appreciated, especially if the reader finds any errors which I can correct. Use “Reply”

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Caltech campus

The California Institute of Technology is a private research university in Pasadena, California. The university is known for its strength in science and engineering, and is one among a small group of institutes of technology in the United States which is primarily devoted to the instruction of pure and applied sciences.

The California Institute of Technology was founded as a preparatory and vocational school by Amos G. Throop in 1891 and began attracting influential scientists such as George Ellery Hale, Arthur Amos Noyes, and Robert Andrews Millikan in the early 20th century. The vocational and preparatory schools were disbanded and spun off in 1910 and the college assumed its present name in 1920. In 1934, The California Institute of Technology was elected to the Association of American Universities, and the antecedents of National Aeronautics and Space Administration ‘s Jet Propulsion Laboratory, which The California Institute of Technology continues to manage and operate, were established between 1936 and 1943 under Theodore von Kármán.

The California Institute of Technology has six academic divisions with strong emphasis on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. First-year students are required to live on campus, and 95% of undergraduates remain in the on-campus House System at The California Institute of Technology. Although The California Institute of Technology has a strong tradition of practical jokes and pranks, student life is governed by an honor code which allows faculty to assign take-home examinations. The The California Institute of Technology Beavers compete in 13 intercollegiate sports in the NCAA Division III’s Southern California Intercollegiate Athletic Conference (SCIAC).

As of October 2020, there are 76 Nobel laureates who have been affiliated with The California Institute of Technology, including 40 alumni and faculty members (41 prizes, with chemist Linus Pauling being the only individual in history to win two unshared prizes). In addition, 4 Fields Medalists and 6 Turing Award winners have been affiliated with The California Institute of Technology. There are 8 Crafoord Laureates and 56 non-emeritus faculty members (as well as many emeritus faculty members) who have been elected to one of the United States National Academies. Four Chief Scientists of the U.S. Air Force and 71 have won the United States National Medal of Science or Technology. Numerous faculty members are associated with the Howard Hughes Medical Institute as well as National Aeronautics and Space Administration. According to a 2015 Pomona College study, The California Institute of Technology ranked number one in the U.S. for the percentage of its graduates who go on to earn a PhD.

Research

The California Institute of Technology is classified among “R1: Doctoral Universities – Very High Research Activity”. Caltech was elected to The Association of American Universities in 1934 and remains a research university with “very high” research activity, primarily in STEM fields. The largest federal agencies contributing to research are National Aeronautics and Space Administration; National Science Foundation; Department of Health and Human Services; Department of Defense, and Department of Energy.

In 2005, The California Institute of Technology had 739,000 square feet (68,700 m^2) dedicated to research: 330,000 square feet (30,700 m^2) to physical sciences, 163,000 square feet (15,100 m^2) to engineering, and 160,000 square feet (14,900 m^2) to biological sciences.

In addition to managing NASA-JPL/Caltech , The California Institute of Technology also operates the Caltech Palomar Observatory; the Owens Valley Radio Observatory;the Caltech Submillimeter Observatory; the W. M. Keck Observatory at the Mauna Kea Observatory; the Laser Interferometer Gravitational-Wave Observatory at Livingston, Louisiana and Hanford, Washington; and Kerckhoff Marine Laboratory in Corona del Mar, California. The Institute launched the Kavli Nanoscience Institute at The California Institute of Technology in 2006; the Keck Institute for Space Studies in 2008; and is also the current home for the Einstein Papers Project. The Spitzer Science Center, part of the Infrared Processing and Analysis Center located on The California Institute of Technology campus, is the data analysis and community support center for NASA’s Spitzer Infrared Space Telescope [no longer in service].

The California Institute of Technology partnered with University of California at Los Angeles to establish a Joint Center for Translational Medicine (UCLA-Caltech JCTM), which conducts experimental research into clinical applications, including the diagnosis and treatment of diseases such as cancer.

The California Institute of Technology operates several Total Carbon Column Observing Network stations as part of an international collaborative effort of measuring greenhouse gases globally. One station is on campus.

From “Quanta Magazine” : “New Entanglement Results Hint at Better Quantum Codes”

From “Quanta Magazine”

10.24.22 [Just found this.]
Allison Parshall

Three-way entanglement represents one small step toward a global quantum internet. Credit: Kristina Armitage/Quanta Magazine.

This month, three scientists won the Nobel Prize in Physics for their work proving one of the most counterintuitive yet consequential realities of the quantum world. They showed that two entangled quantum particles must be considered a single system — their states inexorably intertwined with each other — even if the particles are separated by great distances. In practice, this phenomenon of “nonlocality” means that the system you have in front of you can be instantaneously affected by something that’s thousands of miles away.

Entanglement and nonlocality enable computer scientists to create uncrackable codes. In a technique known as device-independent quantum key distribution, a pair of particles is entangled and then distributed to two people. The particles’ shared properties can now serve as a code, one that will keep communications safe even from quantum computers — machines capable of breaking through classical encryption techniques.

But why stop at two particles? In theory, there’s no upper limit on how many particles can share an entangled state. For decades, theoretical physicists have imagined three-way, four-way, even 100-way quantum connections — the sort of thing that would allow a fully distributed quantum-protected internet. Now, a lab in China has achieved what appears to be nonlocal entanglement between three particles at once, potentially boosting the strength of quantum cryptography and the possibilities for quantum networks generally.

“Two-party nonlocality is crazy enough as it is,” said Peter Bierhorst, a quantum information theorist at the University of New Orleans. “But it turns out quantum mechanics can do stuff that even goes beyond that when you have three parties.”

Physicists have entangled more than two particles before. The record is somewhere between 14 particles and 15 trillion, depending on whom you ask. But these were only across short distances, just inches apart at the most. To make multiparty entanglement useful for cryptography, scientists need to go beyond simple entanglement and demonstrate nonlocality — “a high bar to achieve,” said Elie Wolfe, a quantum theorist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.

The key to proving nonlocality is to test whether the properties of one particle match up with the properties of the other — the hallmark of entanglement — once they’re far enough apart that nothing else could cause the effects. For example, a particle that’s still physically close to its entangled twin might emit radiation that affects the other. But if they’re a mile apart and measured practically instantaneously, then they are likely linked only by entanglement. The experimenters use a set of equations called Bell inequalities to rule out all other explanations for the particles’ linked properties.

With three particles, the process of proving nonlocality is similar, but there are more possibilities to rule out. This balloons the complexity of both the measurements and the mathematical hoops that the scientists must jump through to prove the nonlocal relationship of the three particles. “You have to come up with a creative way to approach it,” Bierhorst said — and have the technology to create just the right conditions in the lab.

In results published in August [Physical Review Letters (below)], a team in Hefei, China, made a crucial leap forward. First, by shooting lasers through a special type of crystal, they entangled three photons and placed them in different areas of the research facility, hundreds of meters apart. Then they simultaneously measured a random property of each photon. The researchers analyzed the measurements and found that the relationship between the three particles was best explained by three-way quantum nonlocality. It was the most comprehensive demonstration of three-way nonlocality to date.

Technically, there remains a small chance that something else caused the results. “We still have some open loopholes,” said Xuemei Gu, one of the lead authors of the study. But by separating the particles, they were able to rule out the most glaring alternative explanation for their data: physical proximity.

The authors also based their experiment on a new, stricter definition [Physical Review Letters (below)] of three-way nonlocality that has been gaining traction in the past few years. Whereas past experiments allowed for cooperation between the devices that measured the photons, Gu’s three devices could not communicate. Instead, they made random measurements of the particles — a restriction that would be useful in cryptographic scenarios where any communication can be compromised, said Renato Renner, a quantum physicist at the Swiss Federal Institute of Technology Zurich. (Using the older paradigm, a Canadian team demonstrated three-way nonlocality at a distance in 2014 [Nature Photonics] (below).)

Now that researchers following the new definition have successfully entangled particles this far apart, they can focus on expanding the distance even further.

“It’s an important steppingstone toward doing longer-distance, bigger-scale experiments,” said Saikat Guha, a quantum information theorist at the University of Arizona.

Most directly, this technology can power more expansive quantum key distribution, Renner said. If you use entangled particles as the key to encryption, the same Bell inequalities that physicists use to test for nonlocality can ensure that your secret is completely secure. Then even if the device you use to send or receive a message gets maliciously manipulated by your worst enemy, they won’t be able to determine your quantum key. Those secrets stay between you and whoever has the other entangled particle.

Researchers in China entangled three particles and placed them hundreds of meters apart in facilities labeled Alice, Bob and Charlie.

Quantum key distribution is “the thing people are excited about,” Renner said. Last year, three separate groups demonstrated the protocol in the lab, though still on a small scale. That’s why three-way nonlocality will be so important. “You have in principle much more cryptographic power,” because these three-way connections cannot be simulated by cobbling together a few two-way links.

“It’s a fundamentally new level of phenomena,” Bierhorst said, one that could expand device-independent cryptography from basic, two-way communication to an entire network of secret-sharers.

Besides cryptography, multiparty entanglement also opens up possibilities for other types of quantum networks. Researchers like Guha are working on a quantum internet, which could link up quantum computers the way the regular internet connects ordinary devices. This system would bring together the computing power of many quantum devices by connecting millions of particles with varying levels of entanglement across varying distances. We have all the individual building blocks for such a system, Guha said, but assembling it “is a huge, huge engineering challenge.” With this goal in mind, scientists in the Netherlands have succeeded [Nature (below)] in entangling three particles in a network spanning two separate labs — though unlike Gu’s team, they weren’t focused on demonstrating nonlocality.

This work on three-way entanglement started as “just an interesting phenomenon,” said Bierhorst. But “when you have something that quantum mechanics can do that it’s impossible to do otherwise, that’s going to open up all sorts of new technological possibilities that can be exploited in unforeseen ways.”

For now, a few labs have demonstrated four-way nonlocality between particles that are very close together. “These experiments are pretty speculative at this point. You have to make a lot of assumptions,” said Bierhorst.

The three-way experiments still rely on some assumptions as well. The Nobel laureates spent half a century ruling out those loopholes in their two-way experiments, finally succeeding in 2017. But we’ve come a long way since then technologically, said Renner.

“What [took] decades before will now happen in a year or so,” he said.

Science papers:
Physical Review Letters
Physical Review Letters 2021
Nature Photonics 2014
Nature
See this science paper for instructive material with images.

See the full article here .

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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.

From JILA – [The Joint Institute for Laboratory Astrophysics] Exploring the Frontiers of Physics (University of Colorado-Boulder and NIST): “An Entangled Matter-wave Interferometer – Now with Double the Spookiness!”

From JILA – [The Joint Institute for Laboratory Astrophysics] Exploring the Frontiers of Physics (University of Colorado-Boulder and NIST)

10.20.22
Kenna Hughes-Castleberry

A rendering of the entangled atoms within the interferometer. Image Credit: Steven Burrows/Thompson Group.

JILA and NIST Fellow James K. Thompson’s team of researchers have for the first time successfully combined two of the “spookiest” features of quantum mechanics to make a better quantum sensor: entanglement between atoms and “delocalization” of atoms. Einstein originally referred to entanglement as creating spooky action at a distance—the strange effect of quantum mechanics in which what happens to one atom somehow influences another atom somewhere else. Entanglement is at the heart of hoped-for quantum computers, quantum simulators and quantum sensors. A second rather spooky aspect of quantum mechanics is “delocalization”: the fact that a single atom can be in more than one place at the same time. As described in their paper recently published in Nature [below], the Thompson group has combined the spookiness of both entanglement and delocalization to realize a “matter-wave interferometer” that can sense accelerations with a precision that surpasses the standard quantum limit (a limit on the accuracy of an experimental measurement at a quantum level) for the first time. By doubling down on the spookiness, future quantum sensors will be able to provide more precise navigation, explore for needed natural resources, more precisely determine fundamental constants such as the fine structure and gravitational constants, look more precisely for dark matter, or maybe even one day detect gravitational waves.

Generating Entanglement

To entangle two objects, one must typically bring them very, very close to each other so they can interact. The Thompson group has learned how to entangle thousands to millions of atoms even when they are millimeters or more apart. They do this by using light bouncing between mirrors, called an optical cavity to allow information to jump between the atoms and knit them into an entangled state. Using this unique light-based approach, they have created and observed some of the most highly entangled states ever generated in any system be it atomic, photonic, or solid state. Using this technique, the group designed two distinct experimental approaches, both of which they utilized in their recent work. In the first approach, called a “quantum nondemolition measurement”, they make a premeasurement of the quantum noise associated with their atoms and simply subtract the quantum noise from their final measurement. In a second approach, light injected into the cavity causes the atoms to undergo one-axis twisting, a process in which the quantum noise of each atom becomes correlated with the quantum noise of all the other atoms so that they can conspire together to become quieter. “The atoms are kind of like kids shushing each other to be quiet so they can hear about the party the teacher has promised them, but here it’s the entanglement that does the shushing,” says Thompson.

“Matter-wave Interferometer”

One of the most precise and accurate quantum sensors today is the “matter-wave interferometer”. The idea is that one uses pulses of light to cause atoms to simultaneously move and not move by having both absorbed and not absorbed laser light. This causes the atoms over time to simultaneously be in two different places at once. As graduate student Chengyi Luo explained, “We shine laser beams on the atoms so we actually split each atom’s quantum wave packet in two, in other words, the particle actually exists in two separate spaces at the same time.” Later pulses of laser light then reverse the process bringing the quantum wave packets back together so that any changes in the environment such as accelerations or rotations can be sensed by a measurable amount of interference happening to the two parts of the atomic wave packet, much like is done with light fields in normal interferometers, but here with “de’Broglie waves”, or waves made of matter. The team of JILA graduate students figured out how to make all of this work inside of an optical cavity with highly-reflective mirrors. They could measure how far the atoms fell along the vertically-oriented cavity due to gravity in a quantum version of Galileo’s gravity experiment dropping items from the Leaning Tower of Pisa, but with all the benefits of precision and accuracy that comes along from quantum mechanics.

Doubling the Spookiness

By learning how to operate a matter-wave interferometer inside of an optical cavity, the team of graduate students lead by Chengyi Luo and Graham Greve were then able to take advantage of the light-matter interactions to create entanglement between the different atoms to make a quieter and more precise measurement of the acceleration due to gravity. This is the first time that anyone has been able to observe a matter-wave interferometer with a precision that surpasses the standard quantum limit on precision set by the quantum noise of unentangled atoms.

Thanks to the enhanced precision, researchers like Luo and Thompson see many future benefits for utilizing entanglement as a resource in quantum sensors. Thompson says, “I think that one day we will be able to introduce entanglement into matter-wave interferometers for detecting gravitational waves in space, or for dark matter searches—things that probe fundamental physics, as well as devices that can be used for every day applications such as navigation or geodesy.” With this momentous experimental advance, Thompson and his team hope that others will use this new entangled interferometer approach to lead to other advances in the field of physics. With optimism, Thompson says, “By learning to harness and control all of the spookiness we already know about, maybe we can discover new spooky things about the universe that we haven’t even thought of yet!”

Science paper:
Nature
See the science paper for detailed material with images.

See the full article here.

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JILA at University of Colorado-Boulder

JILA, formerly known as the Joint Institute for Laboratory Astrophysics, is a physical science research institute in the United States. JILA is located on The University of Colorado-Boulder campus. JILA was founded in 1962 as a joint institute of The University of Colorado Boulder and the National Institute of Standards & Technology.

JILA is one of the nation’s leading research institutes in the physical sciences. The world’s first Bose-Einstein Condensate was created at JILA by Eric Cornell and Carl Wieman in 1995. The first frequency comb demonstration was led by John L. Hall at JILA. The first demonstrations of a Fermionic condensate and BEC-BCS crossover physics were done by Deborah S. Jin.

JILA’s members hold faculty appointments in the Departments of Physics; Astrophysical and Planetary Science; Chemistry and Biochemistry; and Molecular, Cellular, and Developmental Biology as well as Engineering. JILA’s Quantum Physics Division of NIST members hold joint faculty appointments at CU in the same departments.

Research at JILA addresses fundamental scientific questions about the limits of quantum measurements and technologies, the design of precision optical and X-ray lasers, the fundamental principles underlying the interaction of light and matter, the role of quantum physics in chemistry and biology, and the processes that have governed the evolution of the Universe for nearly 14 billion years.

From “The New York Times” : “Black Holes May Hide a Mind-Bending Secret About Our Universe”

From “The New York Times”

10.10.22
Dennis Overbye

Credit: Leonardo Santamaria

For the last century the biggest bar fight in science has been between Albert Einstein and himself.

On one side is the Einstein who in 1915 conceived General Relativity, which describes gravity as the warping of space-time by matter and energy. That theory predicted that space-time could bend, expand, rip, quiver like a bowl of Jell-O and disappear into those bottomless pits of nothingness known as black holes.

On the other side is the Einstein who, starting in 1905, laid the foundation for quantum mechanics, the nonintuitive rules that inject randomness into the world — rules that Einstein never accepted. According to quantum mechanics, a subatomic particle like an electron can be anywhere and everywhere at once, and a cat can be both alive and dead until it is observed. God doesn’t play dice, Einstein often complained.

Gravity rules outer space, shaping galaxies and indeed the whole universe, whereas quantum mechanics rules inner space, the arena of atoms and elementary particles. The two realms long seemed to have nothing to do with each other; this left scientists ill-equipped to understand what happens in an extreme situation like a black hole or the beginning of the universe.

But a blizzard of research in the last decade on the inner lives of black holes has revealed unexpected connections between the two views of the cosmos. The implications are mind-bending, including the possibility that our three-dimensional universe — and we ourselves — may be holograms, like the ghostly anti-counterfeiting images that appear on some credit cards and drivers licenses. In this version of the cosmos, there is no difference between here and there, cause and effect, inside and outside or perhaps even then and now; household cats can be conjured in empty space. We can all be Dr. Strange.

“It may be too strong to say that gravity and quantum mechanics are exactly the same thing,” Leonard Susskind of Stanford University wrote in a paper in 2017. “But those of us who are paying attention may already sense that the two are inseparable, and that neither makes sense without the other.”

That insight, Dr. Susskind and his colleagues hope, could lead to a theory that combines gravity and quantum mechanics — quantum gravity — and perhaps explains how the universe began.

Einstein vs. Einstein

The schism between the two Einsteins entered the spotlight in 1935, when the physicist faced off against himself in a pair of scholarly papers.

In one paper, Einstein and Nathan Rosen showed that general relativity predicted that black holes (which were not yet known by that name) could form in pairs connected by shortcuts through space-time, called Einstein-Rosen bridges — “wormholes.” In the imaginations of science fiction writers, you could jump into one black hole and pop out of the other.

In the other paper, Einstein, Rosen and another physicist, Boris Podolsky, tried to pull the rug out from quantum mechanics by exposing a seeming logical inconsistency. They pointed out that, according to the uncertainty principle of quantum physics, a pair of particles once associated would be eternally connected, even if they were light-years apart. Measuring a property of one particle — its direction of spin, say — would instantaneously affect the measurement of its mate. If these photons were flipped coins and one came up heads, the other invariably would be found out to be tails.

To Einstein this proposition was obviously ludicrous, and he dismissed it as “spooky action at a distance.” But today physicists call it “entanglement,” and lab experiments confirm its reality every day. Last week the Nobel Prize in Physics was awarded to a trio of physicists whose experiments over the years had demonstrated the reality of this “spooky action.”

The physicist N. David Mermin of Cornell University once called such quantum weirdness “the closest thing we have to magic.”

As Daniel Kabat, a physics professor at Lehman College in New York, explained it, “We’re used to thinking that information about an object — say, that a glass is half-full — is somehow contained within the object. Entanglement means this isn’t correct. Entangled objects don’t have an independent existence with definite properties of their own. Instead they only exist in relation to other objects.”

Einstein probably never dreamed that the two 1935 papers had anything in common, Dr. Susskind said recently. But Dr. Susskind and other physicists now speculate that wormholes and spooky action are two aspects of the same magic and, as such, are the key to resolving an array of cosmic paradoxes.

Throwing Dice in the Dark

To astronomers, black holes are dark monsters with gravity so strong that they can consume stars, wreck galaxies and imprison even light. At the edge of a black hole, time seems to stop. At a black hole’s center, matter shrinks to infinite density and the known laws of physics break down. But to physicists bent on explicating those fundamental laws, black holes are a Coney Island of mysteries and imagination.

In 1974 the cosmologist Stephen Hawking astonished the scientific world with a heroic calculation showing that, to his own surprise, black holes were neither truly black nor eternal, when quantum effects were added to the picture. Over eons, a black hole would leak energy and subatomic particles, shrink, grow increasingly hot and finally explode. In the process, all the mass that had fallen into the black hole over the ages would be returned to the outer universe as a random fizz of particles and radiation.

This might sound like good news, a kind of cosmic resurrection. But it was a potential catastrophe for physics. A core tenet of science holds that information is never lost; billiard balls might scatter every which way on a pool table, but in principle it is always possible to rewind the tape to determine where they were in the past or predict their positions in the future, even if they drop into a black hole.

But if Hawking were correct, the particles radiating from a black hole were random, a meaningless thermal noise stripped of the details of whatever has fallen in. If a cat fell in, most of its information — name, color, temperament — would be unrecoverable, effectively lost from history. It would be as if you opened your safe deposit box and found that your birth certificate and your passport had disappeared. As Hawking phrased it in 1976: “God not only plays dice, he sometimes throws them where they can’t be seen.”

His declaration triggered a 40-year war of ideas. “This can’t be right,” Dr. Susskind, who became Hawking’s biggest adversary in the subsequent debate, thought to himself when first hearing about Hawking’s claim. “I didn’t know what to make out of it.”

Encoding Reality

A potential solution came to Dr. Susskind one day in 1993 as he was walking through a physics building on campus. There in the hallway he saw a display of a hologram of a young woman.

A hologram is basically a three-dimensional image — a teapot, a cat, Princess Leia — made entirely of light. It is created by illuminating the original (real) object with a laser and recording the patterns of reflected light on a photographic plate. When the plate is later illuminated, a three-dimensional image of the object springs into view at the center.

“‘Hey, here’s a situation where it looks as if information is kind of reproduced in two different ways,’” Dr. Susskind recalled thinking. On the one hand, there is a visible object that “looked real,” he said. “And on the other hand, there’s the same information coded on the film surrounding the hologram. Up close, it just looks like a little bunch of scratches and a highly complex encoding.”

The right combinations of scratches on that film, Dr. Susskind realized, could make anything emerge into three dimensions. Then he thought: What if a black hole was actually a hologram, with the event horizon serving as the “film,” encoding what was inside? It was “a nutty idea, a cool idea,” he recalled.

Across the Atlantic, the same nutty idea had occurred to the Dutch physicist, Gerardus ’t Hooft, a Nobel laureate at Utrecht University in the Netherlands.

According to Einstein’s general relativity, the information content of a black hole or any three-dimensional space — your living room, say, or the whole universe — was limited to the number of bits that could be encoded on an imaginary surface surrounding it. That space was measured in pixels 10⁻³³ centimeters on a side — the smallest unit of space, known as the Planck length.

With data pixels so small, this amounted to quadrillions of megabytes per square centimeter — a stupendous amount of information, but not an infinite amount. Trying to cram too much information into any region would cause it to exceed a limit decreed by Jacob Bekenstein, then a Princeton graduate student and Hawking’s rival, and cause it to collapse into a black hole.

“This is what we found out about Nature’s bookkeeping system,” Dr. ’t Hooft wrote in 1993. “The data can be written onto a surface, and the pen with which the data are written has a finite size.”

The Soup-Can Universe

The cosmos-as-holograph idea found its fullest expression a few years later, in 1997. Juan Maldacena, a theorist at the Institute for Advanced Study in Princeton, N.J., used new ideas from string theory — the speculative “theory of everything” that portrays subatomic particles as vibrating strings — to create a mathematical model of the entire universe as a hologram.

In his formulation, all the information about what happens inside some volume of space is encoded as quantum fields on the surface of the region’s boundary.

Dr. Maldacena’s universe is often portrayed as a can of soup: Galaxies, black holes, gravity, stars and the rest, including us, are the soup inside, and the information describing them resides on the outside, like a label. Think of it as gravity in a can. The inside and outside of the can — the “bulk” and the “boundary” — are complementary descriptions of the same phenomena.

Since the fields on the surface of the soup can obey quantum rules about preserving information, the gravitational fields inside the can must also preserve information. In such a picture, “there is no room for information loss,” Dr. Maldacena said at a conference in 2004.

Hawking conceded: Gravity was not the great eraser after all.

“In other words, the universe makes sense,” Dr. Susskind said in an interview.

“It’s completely crazy,” he added, in reference to the holographic universe. “You could imagine in a laboratory, in a sufficiently advanced laboratory, a large sphere — let’s say, a hollow sphere of a specially tailored material — to be made of silicon and other things, with some kind of appropriate quantum fields inscribed on it.” Then you could conduct experiments, he said: Tap on the sphere, interact with it, then wait for answers from the entities inside.

“On the other hand, you could open up that shell and you would find nothing in it,” he added. As for us entities inside: “We don’t read the hologram, we are the hologram.”

Wormholes, wormholes everywhere

Our actual universe, unlike Dr. Maldacena’s mathematical model, has no boundary, no outer limit. Nonetheless, for physicists, his universe became a proof of principle that gravity and quantum mechanics were compatible and offered a font of clues to how our actual universe works.

But, Dr. Maldacena noted recently, his model did not explain how information manages to escape a black hole intact or how Hawking’s calculation in 1974 went wrong.

Don Page, a former student of Hawking now at the University of Alberta, took a different approach in the 1990s. Suppose, he said, that information is conserved when a black hole evaporates. If so, then a black hole does not spit out particles as randomly as Hawking had thought. The radiation would start out as random, but as time went on, the particles being emitted would become more and more correlated with those that had come out earlier, essentially filling the gaps in the missing information. After billions and billions of years all the hidden information would have emerged.

In quantum terms, this explanation required any particles now escaping the black hole to be entangled with the particles that had leaked out earlier. But this presented a problem. Those newly emitted particles were already entangled with their mates that had already fallen into the black hole, running afoul of quantum rules mandating that particles be entangled only in pairs. Dr. Page’s information-transmission scheme could only work if the particles inside the black hole were somehow the same as the particles that were now outside.

How could that be? The inside and outside of the black hole were connected by wormholes, the shortcuts through space and time proposed by Einstein and Rosen in 1935.

In 2012 Drs. Maldacena and Susskind proposed a formal truce between the two warring Einsteins. They proposed that spooky entanglement and wormholes were two faces of the same phenomenon. As they put it, employing the initials of the authors of those two 1935 papers, Einstein and Rosen in one and Einstein, Podolsky and Rosen in the other: “ER = EPR.”

The implication is that, in some strange sense, the outside of a black hole was the same as the inside, like a Klein bottle that has only one side.

How could information be in two places at once? Like much of quantum physics, the question boggles the mind, like the notion that light can be a wave or a particle depending on how the measurement is made.

What matters is that, if the interior and exterior of a black hole were connected by wormholes, information could flow through them in either direction, in or out, according to John Preskill, a Caltech physicist and quantum computing expert.

“We ought to be able to influence the interior of one of these black holes by ‘tickling’ its radiation, and thereby sending a message to the inside of the black hole,” he said in a 2017 interview with Quanta. He added, “It sounds crazy.”

Ahmed Almheiri, a physicist at N.Y.U. Abu Dhabi, noted recently that by manipulating radiation that had escaped a black hole, he could create a cat inside that black hole. “I can do something with the particles radiating from the black hole, and suddenly a cat is going to appear in the black hole,” he said.

He added, “We all have to get used to this.”

The metaphysical turmoil came to a head in 2019. That year two groups of theorists made detailed calculations showing that information leaking through wormholes would match the pattern predicted by Dr. Page. One paper was by Geoff Penington, now at the University of California, Berkeley. And the other was by Netta Engelhardt of M.I.T.; Don Marolf of the University of California, Santa Cruz; Henry Maxfield, now at Stanford University; and Dr. Almheiri. The two groups published their papers on the same day.

“And so the final moral of the story is, if your theory of gravity includes wormholes, then you get information coming out,” Dr. Penington said. “If it doesn’t include wormholes, then presumably you don’t get information coming out.”

He added, “Hawking didn’t include wormholes, and we are including wormholes,”

Not everybody has signed on to this theory. And testing it is a challenge, since particle accelerators will probably never be powerful enough to produce black holes in the lab for study, although several groups of experimenters hope to simulate black holes and wormholes in quantum computers.

And even if this physics turns out to be accurate, Dr. Mermin’s magic does have an important limit: Neither wormholes nor entanglement can transmit a message, much less a human, faster than the speed of light. So much for time travel. The weirdness only becomes apparent after the fact, when two scientists compare their observations and discover that they match — a process that involves classical physics, which obeys the speed limit set by Einstein.

As Dr. Susskind likes to say, “You can’t make that cat hop out of a black hole faster than the speed of light.”

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From The Paderborn University [Universität Paderborn] (DE) Via “phys.org” : “Achieving greater entanglement – Milestones on the path to useful quantum technologies”

From The Paderborn University [Universität Paderborn] (DE)

Via

“phys.org”

10.6.22

a) Operating principle of our approach. Bell pairs are generated sequentially. The detection of one photon triggers the feed-forward including a field programmable gate array (FPGA), which in turn controls the operation mode of an all-optical storage loop. Possible operation modes are “read in and read out” (orange), “Storage” (green), or “PBS interference” (purple) selected by an appropriate switching of the electro-optic modulator (EOM). 2N-fold coincidences confirm the buildup of 2N-photon GHZ states. (b) Sketch of the experimental setup. A Ti:sapphire laser with a wavelength of 775 nm pumps a polarization Bell-state source based on parametric down-conversion in a Sagnac configuration (blue area). One photon of each emitted Bell pair is detected and triggers the feed-forward (red arrows), and the other photon is sent to our all-optical storage loop (green area), where it is stored until it is brought to interference with the subsequent qubit. Credit: Physical Review Letters (2022).

Tiny particles are interconnected despite sometimes being thousands of kilometers apart—Albert Einstein called this “spooky action at a distance.” Something that would be inexplicable by the laws of classical physics is a fundamental part of quantum physics. Entanglement like this can occur between multiple quantum particles, meaning that certain properties of the particles are intimately linked with each other.

Entangled systems containing multiple quantum particles offer significant benefits in implementing quantum algorithms, which have the potential to be used in communications, data security or quantum computing. Researchers from Paderborn University have been working with colleagues from Ulm University to develop the first programmable optical quantum memory. The study was published as an “Editor’s suggestion” in the Physical Review Letters journal [below].

Entangled light particles

The Integrated Quantum Optics group led by Prof. Christine Silberhorn from the Department of Physics and Institute for Photonic Quantum Systems (PhoQS) at Paderborn University is using minuscule light particles, or photons, as quantum systems. The researchers are seeking to entangle as many as possible in large states. Working together with researchers from the Institute of Theoretical Physics at Ulm University, they have now presented a new approach.

Previously, attempts to entangle more than two particles only resulted in very inefficient entanglement generation. In some cases, if researchers wanted to link two particles with others, it involved a long wait, as the interconnections that promote this entanglement only operate with limited probability rather than at the touch of a button. This meant that the photons were no longer a part of the experiment once the next suitable particle arrived—as storing qubit states represents a major experimental challenge.

Gradually achieving greater entanglement

“We have now developed a programmable, optical, buffer quantum memory that can switch dynamically back and forth between different modes—storage mode, interference mode and the final release,” Silberhorn explains.

In the experimental setup, a small quantum state can be stored until another state is generated, and then the two can be entangled. This enables a large, entangled quantum state to grow particle by particle. Silberhorn’s team has already used this method to entangle six particles, making it much more efficient than any previous experiments. By comparison, the largest ever entanglement of photon pairs, performed by Chinese researchers, consisted of twelve individual particles. However, creating this state took significantly more time, by orders of magnitude.

The quantum physicist explains: “Our system allows entangled states of increasing size to be gradually built up—which is much more reliable, faster, and more efficient than any previous method. For us, this represents a milestone that puts us in striking distance of practical applications of large, entangled states for useful quantum technologies.” The new approach can be combined with all common photon-pair sources, meaning that other scientists will also be able to use the method.

Science paper:
Physical Review Letters

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The Paderborn University [Universität Paderborn] (DE) is one of the fourteen public research universities in the state of North Rhine-Westphalia in Germany. It was founded in 1972 and 20,308 students were enrolled at the university in the wintersemester 2016/2017. It offers 62 different degree programs.

The university has several winners of the Gottfried Wilhelm Leibniz Prize awarded by the German Research Foundation (DFG) and ERC grant recipients of the European Research Council. In 2002, the Romanian mathematician Preda Mihăilescu proved the Catalan conjecture, a number-theoretical conjecture, formulated by the French and Belgian mathematician Eugène Charles Catalan, which had stood unresolved for 158 years. The University Closely Collaborates with the Heinz Nixdorf Institute, Paderborn Center for Parallel Computing and two Fraunhofer Institutes for research in Computer Science, Mathematics, Electrical Engineering and Quantum Photonics.

In 2018, world record for “optical data transmission at 128 gigabits per second” was achieved at the Heinz Nixdorf Institute of the University of Paderborn. The academic ranking of world universities 2018, popularly known as Shanghai Rankings placed the university in the ranking bracket 50-75 among mathematics departments worldwide.

From “The New York Times” : “Nobel Prize in Physics Is Awarded to 3 Scientists for Work in Quantum Technology”

From “The New York Times”

10.4.22
Isabella Kwai
Cora Engelbrecht
Dennis Overbye

Awarding the prize on Tuesday, the committee said that the scientists’ work had “opened doors to another world.” Credit: Jonas Ekstromer/TT News Agency, via Associated Press

The Nobel Prize in Physics was awarded to Alain Aspect, John F. Clauser and Anton Zeilinger on Tuesday for work that has “laid the foundation for a new era of quantum technology,” the Nobel Committee for Physics said.

Alain Aspect.

John F. Clauser

Anton Zeilinger

The scientists have each conducted “groundbreaking experiments using entangled quantum states, where two particles behave like a single unit even when they are separated,” the committee said in a briefing. Their results, it said, cleared the way for “new technology based upon quantum information.”

The laureates’ research builds on the work of John Stewart Bell, a physicist who strove in the 1960s to understand whether particles, having flown too far apart for there to be normal communication between them, can still function in concert, also known as quantum entanglement.

According to quantum mechanics, particles can exist simultaneously in two or more places. They do not take on formal properties until they are measured or observed in some way. By taking measurements of one particle, like its position or “spin,” a change is observed in its partner, no matter how far away it has traveled from its pair.

Working independently, the three laureates did experiments that helped clarify a fundamental claim about quantum entanglement, which concerns the behavior of tiny particles, like electrons, that interacted in the past and then moved apart.

Dr. Clauser, an American, was the first in 1972. Using duct tape and spare parts at The DOE’s Lawrence Berkeley National Laboratory in Berkeley, Calif., he endeavored to measure quantum entanglement by firing thousands of photons in opposite directions to investigate a property known as polarization. When he measured the polarizations of photon pairs, they showed a correlation, proving that a principle called Bell’s inequality had been violated and that the photon pairs were entangled, or acting in concert.

The research was taken up 10 years later by Dr. Aspect, a French scientist, and his team at the University of Paris. And in 1998, Dr. Zeilinger, an Austrian physicist, led another experiment that considered entanglement among three or more particles.

Eva Olsson, a member of the Nobel Committee for Physics, noted that quantum information science had broad implications in areas like secure information transfer and quantum computing.

Quantum information science is a “vibrant and rapidly developing field,” she said. “Its predictions have opened doors to another world, and it has also shaken the very foundation of how we interpret measurements.”

The Nobel committee said the three scientists were being honored for their experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.

“Being able to manipulate and manage quantum states and all their layers of properties gives us access to tools with unexpected potential,” the committee said in a statement on Twitter.

Dr. Zeilinger described the award as “an encouragement to young people.”

“The prize would not be possible without more than 100 young people who worked with me over the years and made all this possible,” he said.

Though he acknowledged that the award was recognizing the future applications of his work, he said, “My advice would be: Do what you find interesting, and don’t care too much about possible applications.”

It was the second of several such prizes to be awarded over the coming week. The Nobels, among the highest honors in science, recognize groundbreaking contributions in a variety of fields.

“I’m still kind of shocked, but it’s a very positive shock,” Dr. Zeilinger said of receiving the phone call informing him of the news.

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From The University of Oxford (UK): “A quantum network of entangled atomic clocks”

From The University of Oxford (UK)

For the first time, scientists at the University of Oxford have been able to demonstrate a network of two entangled optical atomic clocks and show how the entanglement between the remote clocks can be used to improve their measurement precision, according to research published this week by Nature [below].

Improving the precision of frequency comparisons between multiple atomic clocks offers the potential to unlock our understanding of all sorts of natural phenomena. It is essential, for example, in measuring the space-time variation of fundamental constants, for geodesy where the frequency of the atomic clocks is used to measure the heights of two locations, and even in the search for dark matter.

Fundamental limit of precision

Entanglement – a quantum phenomenon in which two or more particles become linked together so that they can no longer be described independently, even at vast distances – is the key to reaching the fundamental limit of precision that’s determined by quantum theory. While previous experiments have demonstrated that entanglement between clocks in the same system can be used to improve the quality of measurements, this is the first time researchers have been able to achieve this between clocks in two separate remotely entangled systems. This development paves the way for applications like those mentioned above, where comparing the frequencies of atoms in separate locations to the highest possible precision is vital.

Bethan Nichol, one of the authors of the paper published in Nature, said ‘Thanks to years of hard work from the whole team at Oxford, our network apparatus can produce entangled pairs of ions with high fidelity and high rate at the push of a button. Without this capability this demonstration would not have been possible.’

State-of-the-art quantum network

The Oxford team used a state-of-the-art quantum network to achieve their results. Developed by the UK’s Quantum Computing and Simulation (QCS) Hub, a consortium of 17 universities led by the University of Oxford, this network was designed for quantum computing and for communication rather than for quantum-enhanced metrology, but the researchers’ work demonstrates the versatility of such systems. The two clocks used for the experiment were only 2 metres apart, but in principle such networks can be scaled up to cover much larger distances.

‘While our result is very much a proof-of-principle, and the absolute precision we achieve is a few orders of magnitude below the state of the art, we hope that the techniques shown here might someday improve state-of the art systems,’ explains Dr Raghavendra Srinivas, another of the paper’s authors. ‘At some point, entanglement will be required as it provides a path to the ultimate precision allowed by quantum theory.’

Professor David Lucas, whose team at Oxford were responsible for the experiment, said, ‘Our experiment shows the importance of quantum networks for metrology, with applications to fundamental physics, as well as to the more well-known areas of quantum cryptography and quantum computing.’

Science paper:
Nature

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The University of Oxford

Universitas Oxoniensis

The University of Oxford [a.k.a. The Chancellor, Masters and Scholars of the University of Oxford] is a collegiate research university in Oxford, England. There is evidence of teaching as early as 1096, making it the oldest university in the English-speaking world and the world’s second-oldest university in continuous operation. It grew rapidly from 1167 when Henry II banned English students from attending the University of Paris [Université de Paris](FR). After disputes between students and Oxford townsfolk in 1209, some academics fled north-east to Cambridge where they established what became the The University of Cambridge (UK). The two English ancient universities share many common features and are jointly referred to as Oxbridge.

The university is made up of thirty-nine semi-autonomous constituent colleges, six permanent private halls, and a range of academic departments which are organised into four divisions. 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. It does not have a main campus, and its buildings and facilities are scattered throughout the city centre. Undergraduate teaching at Oxford consists of lectures, small-group tutorials at the colleges and halls, seminars, laboratory work and occasionally further tutorials provided by the central university faculties and departments. Postgraduate teaching is provided predominantly centrally.

Oxford operates the world’s oldest university museum, as well as the largest university press in the world and the largest academic library system nationwide. In the fiscal year ending 31 July 2019, the university had a total income of £2.45 billion, of which £624.8 million was from research grants and contracts.

Oxford has educated a wide range of notable alumni, including 28 prime ministers of the United Kingdom and many heads of state and government around the world. As of October 2020, 72 Nobel Prize laureates, 3 Fields Medalists, and 6 Turing Award winners have studied, worked, or held visiting fellowships at the University of Oxford, while its alumni have won 160 Olympic medals. Oxford is the home of numerous scholarships, including the Rhodes Scholarship, one of the oldest international graduate scholarship programmes.

The University of Oxford’s foundation date is unknown. It is known that teaching at Oxford existed in some form as early as 1096, but it is unclear when a university came into being.

It grew quickly from 1167 when English students returned from The University of Paris-Sorbonne [Université de Paris-Sorbonne](FR). The historian Gerald of Wales lectured to such scholars in 1188, and the first known foreign scholar, Emo of Friesland, arrived in 1190. The head of the university had the title of chancellor from at least 1201, and the masters were recognised as a universitas or corporation in 1231. The university was granted a royal charter in 1248 during the reign of King Henry III.

The students associated together on the basis of geographical origins, into two ‘nations’, representing the North (northerners or Boreales, who included the English people from north of the River Trent and the Scots) and the South (southerners or Australes, who included English people from south of the Trent, the Irish and the Welsh). In later centuries, geographical origins continued to influence many students’ affiliations when membership of a college or hall became customary in Oxford. In addition, members of many religious orders, including Dominicans, Franciscans, Carmelites and Augustinians, settled in Oxford in the mid-13th century, gained influence and maintained houses or halls for students. At about the same time, private benefactors established colleges as self-contained scholarly communities. Among the earliest such founders were William of Durham, who in 1249 endowed University College, and John Balliol, father of a future King of Scots; Balliol College bears his name. Another founder, Walter de Merton, a Lord Chancellor of England and afterwards Bishop of Rochester, devised a series of regulations for college life. Merton College thereby became the model for such establishments at Oxford, as well as at the University of Cambridge. Thereafter, an increasing number of students lived in colleges rather than in halls and religious houses.

In 1333–1334, an attempt by some dissatisfied Oxford scholars to found a new university at Stamford, Lincolnshire, was blocked by the universities of Oxford and Cambridge petitioning King Edward III. Thereafter, until the 1820s, no new universities were allowed to be founded in England, even in London; thus, Oxford and Cambridge had a duopoly, which was unusual in large western European countries.

The new learning of the Renaissance greatly influenced Oxford from the late 15th century onwards. Among university scholars of the period were William Grocyn, who contributed to the revival of Greek language studies, and John Colet, the noted biblical scholar.

With the English Reformation and the breaking of communion with the Roman Catholic Church, recusant scholars from Oxford fled to continental Europe, settling especially at the University of Douai. The method of teaching at Oxford was transformed from the medieval scholastic method to Renaissance education, although institutions associated with the university suffered losses of land and revenues. As a centre of learning and scholarship, Oxford’s reputation declined in the Age of Enlightenment; enrollments fell and teaching was neglected.

In 1636, William Laud, the chancellor and Archbishop of Canterbury, codified the university’s statutes. These, to a large extent, remained its governing regulations until the mid-19th century. Laud was also responsible for the granting of a charter securing privileges for The University Press, and he made significant contributions to the Bodleian Library, the main library of the university. From the beginnings of the Church of England as the established church until 1866, membership of the church was a requirement to receive the BA degree from the university and “dissenters” were only permitted to receive the MA in 1871.

The university was a centre of the Royalist party during the English Civil War (1642–1649), while the town favoured the opposing Parliamentarian cause. From the mid-18th century onwards, however, the university took little part in political conflicts.

Wadham College, founded in 1610, was the undergraduate college of Sir Christopher Wren. Wren was part of a brilliant group of experimental scientists at Oxford in the 1650s, the Oxford Philosophical Club, which included Robert Boyle and Robert Hooke. This group held regular meetings at Wadham under the guidance of the college’s Warden, John Wilkins, and the group formed the nucleus that went on to found the Royal Society.

Before reforms in the early 19th century, the curriculum at Oxford was notoriously narrow and impractical. Sir Spencer Walpole, a historian of contemporary Britain and a senior government official, had not attended any university. He said, “Few medical men, few solicitors, few persons intended for commerce or trade, ever dreamed of passing through a university career.” He quoted the Oxford University Commissioners in 1852 stating: “The education imparted at Oxford was not such as to conduce to the advancement in life of many persons, except those intended for the ministry.” Nevertheless, Walpole argued:

“Among the many deficiencies attending a university education there was, however, one good thing about it, and that was the education which the undergraduates gave themselves. It was impossible to collect some thousand or twelve hundred of the best young men in England, to give them the opportunity of making acquaintance with one another, and full liberty to live their lives in their own way, without evolving in the best among them, some admirable qualities of loyalty, independence, and self-control. If the average undergraduate carried from university little or no learning, which was of any service to him, he carried from it a knowledge of men and respect for his fellows and himself, a reverence for the past, a code of honour for the present, which could not but be serviceable. He had enjoyed opportunities… of intercourse with men, some of whom were certain to rise to the highest places in the Senate, in the Church, or at the Bar. He might have mixed with them in his sports, in his studies, and perhaps in his debating society; and any associations which he had this formed had been useful to him at the time, and might be a source of satisfaction to him in after life.”

Out of the students who matriculated in 1840, 65% were sons of professionals (34% were Anglican ministers). After graduation, 87% became professionals (59% as Anglican clergy). Out of the students who matriculated in 1870, 59% were sons of professionals (25% were Anglican ministers). After graduation, 87% became professionals (42% as Anglican clergy).

M. C. Curthoys and H. S. Jones argue that the rise of organised sport was one of the most remarkable and distinctive features of the history of the universities of Oxford and Cambridge in the late 19th and early 20th centuries. It was carried over from the athleticism prevalent at the public schools such as Eton, Winchester, Shrewsbury, and Harrow.

All students, regardless of their chosen area of study, were required to spend (at least) their first year preparing for a first-year examination that was heavily focused on classical languages. Science students found this particularly burdensome and supported a separate science degree with Greek language study removed from their required courses. This concept of a Bachelor of Science had been adopted at other European universities (The University of London (UK) had implemented it in 1860) but an 1880 proposal at Oxford to replace the classical requirement with a modern language (like German or French) was unsuccessful. After considerable internal wrangling over the structure of the arts curriculum, in 1886 the “natural science preliminary” was recognized as a qualifying part of the first-year examination.

At the start of 1914, the university housed about 3,000 undergraduates and about 100 postgraduate students. During the First World War, many undergraduates and fellows joined the armed forces. By 1918 virtually all fellows were in uniform, and the student population in residence was reduced to 12 per cent of the pre-war total. The University Roll of Service records that, in total, 14,792 members of the university served in the war, with 2,716 (18.36%) killed. Not all the members of the university who served in the Great War were on the Allied side; there is a remarkable memorial to members of New College who served in the German armed forces, bearing the inscription, ‘In memory of the men of this college who coming from a foreign land entered into the inheritance of this place and returning fought and died for their country in the war 1914–1918’. During the war years the university buildings became hospitals, cadet schools and military training camps.

Reforms

Two parliamentary commissions in 1852 issued recommendations for Oxford and Cambridge. Archibald Campbell Tait, former headmaster of Rugby School, was a key member of the Oxford Commission; he wanted Oxford to follow the German and Scottish model in which the professorship was paramount. The commission’s report envisioned a centralised university run predominantly by professors and faculties, with a much stronger emphasis on research. The professional staff should be strengthened and better paid. For students, restrictions on entry should be dropped, and more opportunities given to poorer families. It called for an enlargement of the curriculum, with honours to be awarded in many new fields. Undergraduate scholarships should be open to all Britons. Graduate fellowships should be opened up to all members of the university. It recommended that fellows be released from an obligation for ordination. Students were to be allowed to save money by boarding in the city, instead of in a college.

The system of separate honour schools for different subjects began in 1802, with Mathematics and Literae Humaniores. Schools of “Natural Sciences” and “Law, and Modern History” were added in 1853. By 1872, the last of these had split into “Jurisprudence” and “Modern History”. Theology became the sixth honour school. In addition to these B.A. Honours degrees, the postgraduate Bachelor of Civil Law (B.C.L.) was, and still is, offered.

The mid-19th century saw the impact of the Oxford Movement (1833–1845), led among others by the future Cardinal John Henry Newman. The influence of the reformed model of German universities reached Oxford via key scholars such as Edward Bouverie Pusey, Benjamin Jowett and Max Müller.

Administrative reforms during the 19th century included the replacement of oral examinations with written entrance tests, greater tolerance for religious dissent, and the establishment of four women’s colleges. Privy Council decisions in the 20th century (e.g. the abolition of compulsory daily worship, dissociation of the Regius Professorship of Hebrew from clerical status, diversion of colleges’ theological bequests to other purposes) loosened the link with traditional belief and practice. Furthermore, although the university’s emphasis had historically been on classical knowledge, its curriculum expanded during the 19th century to include scientific and medical studies. Knowledge of Ancient Greek was required for admission until 1920, and Latin until 1960.

The University of Oxford began to award doctorates for research in the first third of the 20th century. The first Oxford D.Phil. in mathematics was awarded in 1921.

The mid-20th century saw many distinguished continental scholars, displaced by Nazism and communism, relocating to Oxford.

The list of distinguished scholars at the University of Oxford is long and includes many who have made major contributions to politics, the sciences, medicine, and literature. As of October 2020, 72 Nobel laureates and more than 50 world leaders have been affiliated with the University of Oxford.

To be a member of the university, all students, and most academic staff, must also be a member of a college or hall. There are thirty-nine colleges of the University of Oxford (including Reuben College, planned to admit students in 2021) and six permanent private halls (PPHs), each controlling its membership and with its own internal structure and activities. Not all colleges offer all courses, but they generally cover a broad range of subjects.

The colleges are:

All-Souls College
Balliol College
Brasenose College
Christ Church College
Corpus-Christi College
Exeter College
Green-Templeton College
Harris-Manchester College
Hertford College
Jesus College
Keble College
Kellogg College
Lady-Margaret-Hall
Linacre College
Lincoln College
Magdalen College
Mansfield College
Merton College
New College
Nuffield College
Oriel College
Pembroke College
Queens College
Reuben College
St-Anne’s College
St-Antony’s College
St-Catherines College
St-Cross College
St-Edmund-Hall College
St-Hilda’s College
St-Hughs College
St-John’s College
St-Peters College
Somerville College
Trinity College
University College
Wadham College
Wolfson College
Worcester College

The permanent private halls were founded by different Christian denominations. One difference between a college and a PPH is that whereas colleges are governed by the fellows of the college, the governance of a PPH resides, at least in part, with the corresponding Christian denomination. The six current PPHs are:

Blackfriars
Campion Hall
Regent’s Park College
St Benet’s Hall
St-Stephen’s Hall
Wycliffe Hall

The PPHs and colleges join as the Conference of Colleges, which represents the common concerns of the several colleges of the university, to discuss matters of shared interest and to act collectively when necessary, such as in dealings with the central university. The Conference of Colleges was established as a recommendation of the Franks Commission in 1965.

Teaching members of the colleges (i.e. fellows and tutors) are collectively and familiarly known as dons, although the term is rarely used by the university itself. In addition to residential and dining facilities, the colleges provide social, cultural, and recreational activities for their members. Colleges have responsibility for admitting undergraduates and organizing their tuition; for graduates, this responsibility falls upon the departments. There is no common title for the heads of colleges: the titles used include Warden, Provost, Principal, President, Rector, Master and Dean.

Oxford is regularly ranked within the top 5 universities in the world and is currently ranked first in the world in the Times Higher Education World University Rankings, as well as the Forbes’s World University Rankings. It held the number one position in The Times Good University Guide for eleven consecutive years, and the medical school has also maintained first place in the “Clinical, Pre-Clinical & Health” table of The Times Higher Education World University Rankings for the past seven consecutive years. In 2021, it ranked sixth among the universities around the world by SCImago Institutions Rankings. The Times Higher Education has also recognised Oxford as one of the world’s “six super brands” on its World Reputation Rankings, along with The University of California-Berkeley, The University of Cambridge (UK), Harvard University, The Massachusetts Institute of Technology, and Stanford University. The university is fifth worldwide on the US News ranking. Its Saïd Business School came 13th in the world in The Financial Times Global MBA Ranking.
Oxford was ranked ninth in the world in 2015 by The Nature Index, which measures the largest contributors to papers published in 82 leading journals. It is ranked fifth best university worldwide and first in Britain for forming CEOs according to The Professional Ranking World Universities, and first in the UK for the quality of its graduates as chosen by the recruiters of the UK’s major companies.

In the 2018 Complete University Guide, all 38 subjects offered by Oxford rank within the top 10 nationally meaning Oxford was one of only two multi-faculty universities (along with Cambridge) in the UK to have 100% of their subjects in the top 10. Computer Science, Medicine, Philosophy, Politics and Psychology were ranked first in the UK by the guide.

According to The QS World University Rankings by Subject, the University of Oxford also ranks as number one in the world for four Humanities disciplines: English Language and Literature, Modern Languages, Geography, and History. It also ranks second globally for Anthropology, Archaeology, Law, Medicine, Politics & International Studies, and Psychology.