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Jarzynski Awarded a 2020 Guggenheim Fellowship

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Category: Department News
Published: Monday, April 20 2020 05:56
The John Simon Guggenheim Memorial Foundation awarded a 2020 Guggenheim Fellowship to Distinguished University Professor Christopher Jarzynski.

Christopher JarzynskiChristopher Jarzynski. Photo credit: Faye Levine

Each year, 175 Guggenheim Fellowships are awarded to a diverse group of writers, scholars, artists and scientists. Chosen from nearly 3,000 applicants representing 53 scholarly disciplines and artistic fields, Jarzynski is one of only two winners selected in the physics category this year.

"The Guggenheim Foundation has been awarding these fellowships for scholarship and the creative arts for nearly a century, and quite a few have been awarded to UMD faculty over the years,” Jarzynski said. “I'm honored to have been selected as one of this year's Fellows. I plan to use the award for the sabbatical that I will take during the 2020-21 academic year."

Jarzynski is a statistical physicist and theoretical chemist who models the random motions of atoms and molecules using mathematics and statistics. Working at the boundary between chemistry and physics, Jarzynski studies how the laws of thermodynamics—originally developed to describe the operation of steam engines—apply to complex microscopic systems such as living cells and artificial nanoscale machines.

Jarzynski is well known for developing an equation to express the second law of thermodynamics for systems at the molecular scale. The equation is known as the Jarzynski equality. Published in the journal Physical Review Letters in 1997, the paper that introduced his equation has been cited in scientific literature more than 4,000 times.

When the 2018 Nobel Prize in physics was awarded for inventions in laser physics, the Nobel Committee cited testing the Jarzynski equality as an application of one of the winning inventions—optical tweezers. Optical tweezers use laser beams to manipulate extremely small objects such as biological molecules.

More recently, Jarzynski’s research has led to a new method for measuring “free energy”—the energy available to any system to perform useful work—in extremely small systems. This research is fundamental to new technologies and may lay the foundation for development of molecular- and quantum-scale machines.

A Fellow of the American Physical Society (APS) and a member of the American Academy of Arts and Sciences, Jarzynski received a 2020 Simons Fellowship and the APS’ 2019 Lars Onsager Prize, which recognizes outstanding research in theoretical statistical physics. He was also awarded a Fulbright Scholarship and the Raymond and Beverly Sackler Prize in the Physical Sciences. He serves on the editorial board for the Journal of Statistical Mechanics: Theory and Experiment and is an associate editor for the Journal of Statistical Physics.

Jarzynski earned his B.A. in physics from Princeton University and his Ph.D. in physics from the University of California, Berkeley. After a postdoctoral appointment at the Institute for Nuclear Theory in Seattle, he spent 10 years at Los Alamos National Laboratory. He has been on the faculty of the University of Maryland since 2006.

Original story here.

 

 

Peeking into a World of Spin-3/2 Materials

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Category: Research News
Published: Thursday, April 16 2020 10:32
Researchers have been pushing the frontiers of the quantum world for over a century. And time after time, spin has been a rich source of new physics.

Spin, like mass and electrical charge, is an intrinsic property of quantum particles. It is central to understanding how quantum objects will respond to a magnetic field, and it divides all quantum objects into two types. The half-integer ones, like the spin-1/2 electron, refuse to share the same quantum state, whereas the integer ones, like the spin-1 photon, don’t have a problem cozying up together. So, spin is essential when delving into virtually any topic governed by quantum mechanics, from the Higgs Boson to superconductors.  In a material, the momentum and energy of an electron are tied together by a “dispersion relation” (pictured above). This relationship influences the electrons’ behavior, sometimes making them behave as particles with different quantum properties. (Credit: Igor Boettcher/University of Maryland)In a material, the momentum and energy of an electron are tied together by a “dispersion relation” (pictured above). This relationship influences the electrons’ behavior, sometimes making them behave as particles with different quantum properties. (Credit: Igor Boettcher/University of Maryland)

Yet after almost a century of playing a central role in quantum research, questions about spin remain. For example, why do all the elementary particles that we know about only have spin values of 0, 1/2, or 1? And what new behaviors might exist for particles with spin values greater than 1?

The first question may remain a cosmic mystery, but there are opportunities to explore the second. Inside of a material, a particle’s surroundings can cause it to behave like it has a new spin value. In the past couple years, researchers have discovered materials in which electrons behave like their spin has been bumped up, from 1/2 to 3/2. UMD postdoctoral researcher Igor Boettcher of the Joint Quantum Institute explored the new behaviors these spins might produce in a recent paper featured on the cover of Physical Review Letters.

Instead of looking at a particular material, Boettcher focused on the math that describes interactions between spin-3/2 electrons at low temperatures. These electrons can interact in more ways than their mundane spin-1/2 counterparts, which unlocks new phases—or collective behaviors—that researchers can look for in experiments. Boettcher sifted through the possible phases, searching for the ones that are likely to be stable at low temperatures. He looked at which phases tie up the least energy in the interactions, since as the temperature drops a material becomes most stable in the form containing the least energy (like steam condensing into liquid water and eventually freezing into ice).

He found three promising phases to hunt for in experiments. Which of these phases, if any, arise in a particular material will depend on its unique properties. Still, Boettcher’s predictions provide researchers with signals to keep an eye out for during experiments. If one of the phases forms, he predicts that common measurement techniques will reveal a signature shift in the electrical properties.

Boettcher’s work is an early step in the exploration of spin-3/2 materials. He hopes that one day the field might be comparable to that of graphene, with researchers constantly racing to explore new physics, produce better quality materials, and identify new transport properties.

“I really hope that this will develop into a big field, which will require both experimentalists and the theorists to do their part so that we can really learn something about the spin-3/2 particles and how they interact.” says Boettcher. “This is really just the beginning right now, because these materials just popped up.”

Story by Bailey Bedford

 
Reference Publication
"Interplay of Topology and Electron-Electron Interactions in Rarita-Schwinger-Weyl semimetals," Igor Boettcher, Phys. Rev. Lett., 124, 127602 (2020)
Research Contact: Igor Boettcher  This email address is being protected from spambots. You need JavaScript enabled to view it.
 
Media Contact: Bailey Bedford This email address is being protected from spambots. You need JavaScript enabled to view it.
Originally published here:  https://jqi.umd.edu/news/peeking-into-world-spin-32-materials
 

New Protocol Helps Classify Topological Matter

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Category: Research News
Published: Wednesday, April 15 2020 10:32

Topological materials have captured the interest of many scientists and may provide the basis for a new era in materials development. On April 10, 2020 in the journal Science Advances, physicists working with Andreas Elben, Jinlong Yu, Peter Zoller and Benoit Vermersch, including Associate Professor Mohammad Hafezi and former Joint Quantum Institute (JQI) postdoctoral researcher Guanyu Zhu (currently a research staff member at IBM T. J. Watson Research Center), presented a new method for identifying and characterizing topological invariants on various experimental platforms, testing their protocol in a quantum simulator made of neutral atoms.

Quantum simulators are an emerging tool for preparing and investigating complex quantum states. They can be realized in a variety of different physical systems—such as ultracold atoms in optical lattices, Rydberg atoms, trapped ions or superconducting quantum bits—and they promise to enhanceTopological phases of matter are a particularly fascinating class of quantum states. (Credit: Harald Ritsch/IQOQI Innsbruck)Topological phases of matter are a particularly fascinating class of quantum states. (Credit: Harald Ritsch/IQOQI Innsbruck) the study of exotic states of matter.

In particular, this new breed of simulator may be able to prepare topological states of matter, which researchers find particularly fascinating. In 2016, David Thouless, Duncan Haldane and Michael Kosterlitz were awarded the Nobel Prize in Physics for their theoretical discoveries about topological states. Scientists now know that these states of matter are characterized by nonlocal quantum correlations, making them particularly robust against local distortions that inevitably occur in experiments.

But it’s often hard to know if a material sample in the lab is in a topological phase. "Identifying and characterizing such topological phases in experiments is a great challenge," say Vermersch, Yu and Elben from the Center for Quantum Physics at the University of Innsbruck and the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences. "Topological phases cannot be identified by local measurements because of their special properties. We are therefore developing new measurement protocols that will enable experimental physicists to characterize these states in the laboratory".

In recent years this identification has been achieved for systems without any interactions. However, for interacting systems, which in the future could also be used as topological quantum computers, this has not been possible so far.

In the new work, the research team proposed and experimentally tested protocols that might enable other experimenters to measure topological invariants. These mathematical expressions distinguish different topological phases, making it possible to classify interacting topological states in a wide variety of systems.

"The idea of our method is to first prepare such a topological state in a quantum simulator,” explains Elben. “Now so-called random measurements are performed, and topological invariants are extracted from statistical correlations of these random measurements.”

The key to the method is that although the topological invariants are highly complex, non-local correlation functions, they can still be extracted from statistical correlations of simple and local random measurements. “The many-body invariants characterizing different types of topological orders are path-integrals in topological quantum field theory, corresponding to various types of space-time manifolds, such as the real-projective plane,” says Zhu. “It is kind of a miracle that we eventually realized that these highly abstract quantities in theory can actually be measured in relatively simple experiments.”

And as some members of the research group have recently shown, such random measurements are possible in experiments today. "Our protocols for measuring the topological invariants can therefore be directly applied in the existing experimental platforms," says Vermersch.

In addition to Elben, Yu, Zoller, Vermersch, Zhu and Hafezi, the co-authors included Frank Pollmann from the Technical University of Munich. The research was financially supported by the European Research Council and the EU flagship for quantum technologies, as well as the Army Research Office MURI program and the NSF Physics Frontier Center at JQI.

This story was originally published by the Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences in Innsbruck. It was adapted with permission by the JQI: https://jqi.umd.edu/news/new-protocol-helps-classify-topological-matter

Reference Publication
"Many-body topological invariants from randomized measurements in synthetic quantum matter," Andreas Elben, Jinlong Yu, Guanyu Zhu, Mohammad Hafezi, Frank Pollmann, Peter Zoller, Beno\^ıt Vermersch, Science Advances, 6, (2020)
Research Contact: Mohammad Hafezi, This email address is being protected from spambots. You need JavaScript enabled to view it.
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Understanding and Exploring Network Epidemiology in the Time of Coronavirus

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Category: Department News
Published: Wednesday, April 15 2020 05:56

In response to the COVID-19 pandemic, Michelle Girvan, Daniel Serrano, Juniper Lovato, Anshuman Swain, and Nick Mennona launched Understanding and Exploring Network Epidemiology in the Time of Coronavirus (#Net_COVID), an online workshop series in network biology developed and presented by the University of Maryland’s COMBINE program in partnership with Vermont’s Complex Systems Center.

The series includes tutorials and seminars to contextualize and understand the current COVID-19 global pandemic using network science. Activities include introduction to network epidemiology, review of recent research on coronavirus, and exploration of various modeling and data analysis approaches. 

The intended audience for the series includes STEM graduate students, postdocs, faculty, and other researchers who are interested in network epidemiology. A prior background in network science is not necessary, but may be helpful for some optional discussion group activities.

The tutorials and seminars can be viewed on the COMBINE YouTube Channel.

The response to the series has been considerable with approximately 250 participating in the seminars and 150 actively engaging in small working groups. Participants are drawn from around the world, with many from UMD taking part in research projects. 

For more information, visit the website or contact the organizers at This email address is being protected from spambots. You need JavaScript enabled to view it.. 

 

This story was originally published here: https://research.umd.edu/news/news_story.php?id=12993

More Articles ...

  1. Donuts, Donut Holes and Topological Superconductors
  2. Charting a Course Toward Quantum Simulations of Nuclear Physics
  3. New Measurements Reveal Evidence of Elusive Particles in a Newly Discovered Superconductor
  4. To Tune Up Your Quantum Computer, Better Call an AI Mechanic

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