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  • richardmitnick 1:12 pm on April 9, 2019 Permalink | Reply
    Tags: "In quantum breakthrough scientists demonstrate ‘one-way street’ for energy flow", , , Classical physics, , ,   

    From University of Chicago: “In quantum breakthrough, scientists demonstrate ‘one-way street’ for energy flow” 

    U Chicago bloc

    From University of Chicago

    Apr 4, 2019
    A. A. Clerk

    1
    Copyright shutterstock.com

    In a new study, scientists found a method to create a controllable one-way channel for the flow of vibrational energy and heat.

    A basic rule in our lives is that if energy can flow in one direction, then it can also flow in the reverse direction. For example, if you open a window and yell at someone outside, you also can hear if they yell back. But what if there was a way to create a “one-way street” for mechanical energy that only allows heat and sound to flow in one direction?

    Finding new ways to break this basic symmetry has sparked the interest of scientists and engineers in recent years; such one-way streets could be extremely useful in applications ranging from quantum computing to cooling in electronics and devices.

    A breakthrough experiment involving researchers with the Institute for Molecular Engineering at the University of Chicago and Yale University demonstrated that by using light to mediate the interaction between mechanical systems, they can create a controllable, one-way channel for the flow of vibrational energy and heat.

    The study, published April 3 in Nature, was based on an idea developed earlier by the University of Chicago team [Physical Review X] and proves that the basic theory works. It also shows that the ideas can be implemented in a simple, compact system that could be incorporated in new devices.

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    Schematic image of the experimental device. Credit: Jack Sankey

    “This is a really exciting resource that can be used in both classical and quantum contexts,” said study co-author Aashish Clerk, a professor in molecular engineering at the University of Chicago who developed the theory. “This research could open the door for many new studies.”

    Breaking symmetry by using light

    The principle that says energy and information exchange between two systems via a two-way street is known as “reciprocity,” and it is a fundamental rule in most physical systems. Breaking this symmetry is crucial in a number of different applications. For example, by preventing a backward flow of energy, one could protect a delicate signal source from corruption, or cool a system by preventing unwanted heating.

    It’s especially important in quantum computation, in which scientists harness quantum phenomena to enable powerful new kinds of information processing. Breaking this symmetry ensures delicate quantum processors are not destroyed during the readout process.

    In their experiment, researchers used a tiny vibrating membrane as the mechanical system. Much like a drumhead, this membrane could vibrate in several distinct ways, each with a distinct resonant frequency.

    The researchers’ goal was to engineer a one-way flow of energy between two of these vibrational modes. To do this, the membrane was placed in a structure called an optical cavity, with two parallel mirrors designed to trap light. By shining light on the cavity using lasers, the researchers were able to use light as a medium for transferring mechanical energy between two vibrational modes. When the lasers were tuned carefully (in a way predicted by Clerk’s theory), this transfer mechanism was completely directional.

    From theory to lab to the quantum level

    The experiment was based on basic theoretical concepts developed by Clerk and his former postdoc Anja Metelmann (now at the Freie University in Berlin).

    “You can come up with a lot of ideas that are exciting in terms of the basic theory and concepts, but often there is a gap between these abstract ideas and what you can actually build and realize in the lab,” Clerk said. “To me, it is exciting that our proposal was realized, and that the experimentalists had enough control over their system to make it work.”

    The approach used in the experiment to achieve a one-way interaction—mechanical vibrations interacting with light—could pave the way for designing new devices targeting a variety of applications, ranging from mitigating heat flow to new kinds of communication systems. These unusual one-way interactions also have interesting fundamental implications.

    As a theoretical physicist who focuses on quantum systems, Clerk is particularly interested in studying arrays where many quantum systems interact with one another in a unidirectional manner. This could be a powerful way to generate the unusual kinds of quantum states that are needed for quantum communication and quantum computation.

    Other authors on the paper include Jack Harris, Haitan Xu and Luyao Jiang of Yale University.

    Clerk is working with the Polsky Center for Entrepreneurship and Innovation at the University of Chicago to advance his discoveries.

    See the full article here .

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    U Chicago Campus

    An intellectual destination

    One of the world’s premier academic and research institutions, the University of Chicago has driven new ways of thinking since our 1890 founding. Today, UChicago is an intellectual destination that draws inspired scholars to our Hyde Park and international campuses, keeping UChicago at the nexus of ideas that challenge and change the world.

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

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

    UChicago research has led to such breakthroughs as discovering the link between cancer and genetics, establishing revolutionary theories of economics, and developing tools to produce reliably excellent urban schooling. We generate new insights for the benefit of present and future generations with our national and affiliated laboratories: Argonne National Laboratory, Fermi National Accelerator Laboratory, and the Marine Biological Laboratory in Woods Hole, Massachusetts.

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

    In all we do, we are driven to dig deeper, push further, and ask bigger questions—and to leverage our knowledge to enrich all human life. Our diverse and creative students and alumni drive innovation, lead international conversations, and make masterpieces. Alumni and faculty, lecturers and postdocs go on to become Nobel laureates, CEOs, university presidents, attorneys general, literary giants, and astronauts.

     
  • richardmitnick 8:02 am on July 24, 2018 Permalink | Reply
    Tags: , Classical physics, , , ,   

    From JHU HUB: “Evidence revealed for a new property of quantum matter” 

    Johns Hopkins

    From JHU HUB

    June 12, 2018 [Where has this been? Just popped into JHU email.]

    A theorized but never-before detected property of quantum matter has now been spotted in the lab, a team led by a Johns Hopkins scientist reports.

    The study findings, published online in the journal Science, show that a particular quantum material first synthesized 20 years ago, called k-(BEDT-TTF)2Hg(SCN)2 Br, behaves like a metal but is derived from organic compounds. The material can demonstrate electrical dipole fluctuations—irregular oscillations of tiny charged poles on the material—even in extremely cold conditions, in the neighborhood of minus 450 degrees Fahrenheit.

    “What we found with this particular quantum material is that, even at super-cold temperatures, electrical dipoles are still present and fluctuate according to the laws of quantum mechanics,” said Natalia Drichko, associate research professor in physics at Johns Hopkins University and the study’s senior author.

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    Natalia Drichko in her lab. Image credit: Jon Schroeder

    “Usually we think of quantum mechanics as a theory of small things, like atoms, but here we observe that the whole crystal is behaving quantum-mechanically.”

    Classical physics describes most of the behavior of physical objects we see and experience in everyday life. In classical physics, objects freeze at extremely low temperatures, Drichko said. In quantum physics—science that primarily describes the behavior of matter and energy at the atomic level and smaller—there is motion even at those frigid temperatures, Drichko said.

    “That’s one of the major differences between classical and quantum physics that condensed matter physicists are exploring,” she said.

    An electrical dipole is a pair of equal but oppositely charged poles separated by some distance. Such dipoles can, for instance, allow a hair to “stick” to a comb through the exchange of static electricity: Tiny dipoles form on the edge of the comb and the edge of the hair.

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    The structure of the crystal that was studied in the research; an individual molecule is highlighted in red. Image credit: Institute for Quantum Matter/JHU

    Drichko’s research team observed the new extreme-low-temperature electrical state of the quantum matter in Drichko’s Raman spectroscopy lab, where the key work was done by graduate student Nora Hassan. Team members focused light on a small crystal of the material. Employing techniques from other disciplines, including chemistry and biology, they found proof of the dipole fluctuations.

    The study was possible because of the team’s home-built, custom-engineered spectrometer, which increased the sensitivity of the measurements 100 times.

    The unique quantum effect the team found could potentially be used in quantum computing, a type of computing in which information is captured and stored in ways that take advantage of the quantum states of matter.

    See the full article here .


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    About the Hub

    We’ve been doing some thinking — quite a bit, actually — about all the things that go on at Johns Hopkins. Discovering the glue that holds the universe together, for example. Or unraveling the mysteries of Alzheimer’s disease. Or studying butterflies in flight to fine-tune the construction of aerial surveillance robots. Heady stuff, and a lot of it.

    In fact, Johns Hopkins does so much, in so many places, that it’s hard to wrap your brain around it all. It’s too big, too disparate, too far-flung.

    We created the Hub to be the news center for all this diverse, decentralized activity, a place where you can see what’s new, what’s important, what Johns Hopkins is up to that’s worth sharing. It’s where smart people (like you) can learn about all the smart stuff going on here.

    At the Hub, you might read about cutting-edge cancer research or deep-trench diving vehicles or bionic arms. About the psychology of hoarders or the delicate work of restoring ancient manuscripts or the mad motor-skills brilliance of a guy who can solve a Rubik’s Cube in under eight seconds.

    There’s no telling what you’ll find here because there’s no way of knowing what Johns Hopkins will do next. But when it happens, this is where you’ll find it.

    Johns Hopkins Campus

    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
  • richardmitnick 4:50 pm on June 28, 2017 Permalink | Reply
    Tags: Classical physics, Transferring New Energy to an Old Rule: Pushing the Boundaries of Classical Physics,   

    From Yale: “Transferring New Energy to an Old Rule: Pushing the Boundaries of Classical Physics” 

    Yale University bloc

    Yale University

    January 16, 2017
    Chunyang Ding

    1
    Cover image: A synchrotron, similar to the one pictured above, was used to determine the composition of fossils, an analysis key to understanding the preservational features of the Tully Monster. Image courtesy of John O’Neill

    Time after time, brilliant scientists make claims about science’s future that prove completely wrong. In a quote often misattributed to Lord Kelvin, Albert Michelson famously declared that “there is nothing new to be discovered in physics now; all that remains is more and more precise measurement.” Classical mechanics, the tradition of physics that originated with Newton, Kepler, and Galileo, is often seen as something we already understand, and something we have understood for a long time. This is simply not true. Even today, new discoveries made with classical mechanics are transforming the world of science as we know it.

    In a recent breakthrough, a Yale physics lab shows new behaviors in a phenomenon that some had considered fully understood. Associate professor of physics Jack Harris and post-doctoral researcher Haitan Xu report in Nature their use of ultra-precise lasers and tiny vibrating sheets that appear to violate classical predictions. Their experiment, transferring energy by very slowly tuning the vibrations, has major implications for a decades-old theorem in mechanics: the adiabatic theorem. This newly discovered phenomenon occurs in all systems with friction, and may fundamentally shift the way physicists view systems.

    A dance for the ages

    Although Xu’s research focuses on how energy can be transferred between two different regions, the core of this new research deals with systems, a very general way of describing things that interact. Most things in the world are systems: the traffic through a busy city, the movement of the planets, or even a large ballroom dance.

    In a ballroom dance, each person on the dance floor obeys the rules of the dance, and as they move, they interact with other people harmoniously. There might be a set number of dance moves that eventually bring them back to the starting point. Essentially, Xu’s research found that there are certain moves that when danced “clockwise,” return you to the same position, but when danced “counter-clockwise,” present you with a new partner. This non-symmetrical form has serious implications for any system, and offers a new way that scientists could control these systems.

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    Any system, even our solar system, can be represented in a parameter space, where different parameters are plotted against each other. Through careful control, the Harris lab was able to navigate the parameters of their vibrating membrane around an exceptional point, showing an extension to the adiabatic theorem. Image courtesy of Sida Tang

    The research provides an extension of the adiabatic theorem, a theorem that governs how systems change as the parameters of the systems change. These parameters can be any controlled quality of the system — the dance moves performed, the tension in a wire, or the controls in a computer. The adiabatic theorem says that if the parameters are slowly restored to their original state, the system will appear to have not changed at all. This is very powerful in physics, because for a certain experiment on a system, scientists can restore previous states without being concerned exactly in what way the parameters changed. Yet, it is not very exciting. After all, you only end up where you begin.

    Imagine for a moment that we had a small dial allowing us to change the masses of Jupiter and the Sun. Through our understanding of the laws of gravity, we could predict how the orbits of the planet change if Jupiter became more massive and if the Sun became less massive. The paths of the planets may become chaotic, but the adiabatic theorem provides a simple solution: when all of the parameters are back to where they began, the system would appear to have never changed.

    However, there is one caveat to the above examples. The only way that the adiabatic theorem has been proven is through assuming systems that do not have any friction, or energy loss. Only in those cases does the adiabatic theorem work as expected. Still, physicists applied this theorem to systems with friction by assuming such systems would behave very similarly to those without friction. What physicists did not expect, however, was that the system could change completely. Although mathematicians predicted anomalies using what they called “exceptional points,” physicists were unable to see these anomalies in actual systems — until now.

    Tiny vibrating membranes

    While the previous systems may be simple to imagine, they would be nearly impossible to actually control and measure. In order to actually see the effects of the adiabatic theorem, Xu’s research involved vibrating a tiny membrane between two mirrors while using lasers both to control and to measure the vibrations of the membrane. The reason this is considered a system is because the membrane has two vibrational modes, or methods of vibration, and the frequency of each vibration can be controlled by the laser. Vibrational modes are like vertical waves and a horizontal waves that pass by each other, and can be thought of as two separate strings, each vibrating independently.

    Vibrating strings are familiar to anyone who has played a string instrument, whether it be a guitar, a violin, or an erhu. When you pluck a single string, the other strings do not react, as each string has a different resonating frequency. However, if you tune two strings to have the same resonating frequency, the vibrating energy can transfer from one string to the other. In this experiment, the resonating frequencies are being changed so that the two different strings are first tuned together, and then returned to their original resonating frequencies. If we then apply the adiabatic theorem, we would predict that whatever vibrations are in the strings now are the same as the vibrations in the strings that we started with.

    3
    The lab group, (Luyao Jiang, Haitan Xu, David Mason and Professor Jack Harris in 8, Professor Jack Harris, Haitan Xu, David Mason and Luyao Jiang in 9) pose before their experimental apparatus. Along with the Doppler group from the Vienna University of Technology, this lab was the first to discover experimental proof for the exceptional points. Image courtesy of George Iskander

    However, Xu’s research group discovered that this is not always the case in a system that has some amount of friction. In rare situations that involve the “exceptional point” in parameter space, the energy can end up transferring from the first string to the second string. Every time the parameters were changed counter-clockwise around the exceptional point, they found drastic changes to the final systems. They found that whenever the parameters created a path that encircled the exceptional point, this change happened, regardless of the actual shape of the path.

    Teleporting between different sheets

    Exceptional points are fairly difficult to imagine for a good reason: They are the result of two 2D sheets intersecting each other in a 4D space. One way to picture these exceptional points is a fire pole connecting two floors of a fire station. While each floor is distinct, they “meet” at the fire pole. However, oddly, when you walk counter-clockwise around the pole on the first floor, you would find yourself on the second floor, without having climbed the pole at all! The phenomenon here is due to the bizarre spatial geometry, similar to shapes like a Mobius strip or a Klein bottle. The exceptional points are mathematically similar, connecting surfaces that appear to be separated.

    The example with the fire station may be hard to visualize, but the actual experiment is even more abstract, as there is no actual movement around anything. Instead, when the parameters of the vibrations travel in this loop, the energy of the system shifts. The experimental group was able to quantitatively measure the energy differences in this single membrane by spying on the vibrations with a low-powered laser even as a high-powered laser changed the parameters. This research, the first of its type, provides solid evidence that the mathematicians were right: Exceptional points exist in parameter space, and physicists can utilize them to control the system.

    In the same issue of Nature, a separate group also published on this topic, but the group used a completely different method. While the Yale group was able to dynamically change the vibrations using the laser, a group from the Vienna University of Technology led by Jorg Doppler found similar effects through pre-fabricated waveguides, which are equally impressive in the ability to control waves. Together with the Xu research, these experiments provide the first empirical proof of exceptional points.

    Taking control of our world

    4
    Like a Klein bottle, the geometries of parameter space may seem to be non-orientable, allowing for this phenomenon to occur. This bizarre discovery shows experimentally what was previously hypothesized mathematically. Image courtesy of Wikimedia

    The most powerful implication of this new research may be in its application for controlling systems. The adiabatic theorem, as well as this extension of the theorem, are particularly robust. They do not seem to care what path you take, as long as you return to the same position. This property is analogous to blindly driving through a dark two-lane icy tunnel, but finding that you always end up on the right side of the road at the end. These robust theorems are extremely helpful for experiments, especially in preventing disruptions to the system. “It’s a new type of control over really pristine systems,” Harris said.

    Even the classical adiabatic theorem and its offshoots are being used to predict magnetic effects and provide a deeper understanding for many quantum phenomena. This new extension of the adiabatic theorem will provide insight for physicists as they apply it to other systems, like NMRs and MRIs. In fact, this extended adiabatic theorem, as a fundamental physical theorem, could be more broadly applied to any system — so this research could theoretically be applied to anything that can be modeled as a system. However, this isn’t the end of the line on this research for the Harris lab; they have a paper forthcoming regarding the application of this technique to very different kinds of vibrations.

    Our understanding of every branch of science is constantly evolving and changing. Just when we think we understand everything about a field, we realize that particles can interact with themselves, that the fabric of space and time can stretch, and that the universe is expanding. Classical mechanics is no different; the extended adiabatic theorem from this study shows just that. At a certain point, we might as well expect to be surprised. If you find yourself walking around a fire pole on the first floor and ending up on the second, don’t be alarmed. Bizarre Twilight Zone scenarios like that are what can help physicist control, bend, and structure our world — no matter how strange those truths may be.

    See the full article here .

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    Yale University Campus

    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 12:19 pm on December 12, 2016 Permalink | Reply
    Tags: , Classical physics, , , ,   

    From Hopkins and Rutgers: “Between two worlds: Exotic insulator may hold clue to key mystery of modern physics” 

    Johns Hopkins
    Johns Hopkins University

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    Rutgers University

    Dec 6, 2016
    Arthur Hirsch

    Scientists experiment with material that straddles world of classical physics and hidden quantum realm

    Experiments using laser light and pieces of gray material the size of fingernail clippings may offer clues to a fundamental scientific riddle: what is the relationship between the everyday world of classical physics and the hidden quantum realm that obeys entirely different rules?

    1
    N. Peter Armitage

    “We found a particular material that is straddling these two regimes,” said N. Peter Armitage, an associate professor of physics at Johns Hopkins University who led the research for the paper just published in the journal Science. Six scientists from Johns Hopkins and Rutgers University were involved in the work on materials called topological insulators, which can conduct electricity on their atoms-thin surface, but not in their insides.

    Topological insulators were predicted in the 1980s, first observed in 2007, and have been studied intensively since. Made from any number of hundreds of elements, these materials have the capacity to show quantum properties that usually appear only at the microscopic level, but here appear in a material visible to the naked eye.

    The experiments reported in Science establish these materials as a distinct state of matter “that exhibits macroscopic quantum mechanical effects,” Armitage said. “Usually we think of quantum mechanics as a theory of small things, but in this system quantum mechanics is appearing on macroscopic length scales. The experiments are made possible by unique instrumentation developed in my laboratory.”

    In the experiments reported in Science, the elements bismuth and selenium make up dark gray material samples—each a few millimeters long and of different thicknesses—that were hit with “THz” light beams that are invisible to the unaided eye. Researchers measured the reflected light as it moved through the material samples and found indicators of a quantum state of matter.

    Specifically, they found that as the light was transmitted through the material, the wave rotated a specific amount, which is related to physical constants that are usually only measurable in atomic scale experiments. The amount matched predictions of what would be possible in this quantum state.

    The results add to scientists’ understanding of topological insulators, but also may contribute to the larger subject that Armitage says is the central question of modern physics: what is the relationship between the macroscopic classical world, and the microscopic quantum world from which it arises?

    Scientists since the early 20th century have struggled with the question of how one set of physical laws governing objects above a certain size can co-exist alongside a different set of laws governing the atomic and subatomic scale. How does classical mechanics emerge from quantum mechanics, and where is the threshold that divides the realms?

    Those questions remain to be answered, but topological insulators could be part of the solution.

    “It’s a piece of the puzzle,” said Armitage, who worked on the experiments along with Liang Wu, who was a graduate student at Johns Hopkins when the work was done; Maryam Salehi of the Rutgers University Department of Material Science and Engineering; and Nikesh Koirala, Jisoo Moon, and Sean Oh of the Rutgers University Department of Physics and Astronomy.

    See the full article here .

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    rutgers-campus

    Rutgers, The State University of New Jersey, is a leading national research university and the state’s preeminent, comprehensive public institution of higher education. Rutgers is dedicated to teaching that meets the highest standards of excellence; to conducting research that breaks new ground; and to providing services, solutions, and clinical care that help individuals and the local, national, and global communities where they live.

    Johns Hopkins Campus

    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
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