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Rolston Reappointed Department Chair

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Category: Department News
Published: Thursday, June 24 2021 05:33

Professor Steve Rolston will begin a second five-year term as chair of the Department of Physics on July 1, 2021.

Rolston, who joined UMD in 2003, will continue to lead the physics department, which ranks No. 14 in the latest U.S. News & World Report Graduate Rankings and has 150 faculty members, nearly 600 students and annual research funding over $30 million.

“I’m grateful to have Steve's continued leadership, guidance and experience as we move forward from this challenging pandemic,” said Amitabh Varshney, dean of UMD’s College of Computer, Mathematical, and Natural Sciences. “I have seen first-hand how Steve selflessly dedicates his time and energy to our physics faculty, staff and students.”

During Rolston’s first term as chair, the department hired eight new faculty members, hosted the Conference for Undergraduate Underrepresented Minorities in Physics three times, and launched a Climate Committee to ensure the department provides a welcoming and supportive environment for all members. In addition, eight physics majors received Goldwater Scholarships and 21 physics students received National Science Foundation Graduate Research Fellowships over that five-year period.

Following the historic detection of gravitational waves in 2015, Rolston spearheaded ways for the department to honor the pioneer of gravitational wave research, Professor Joseph Weber (1919-2000). In 2018, the department created the Weber Memorial Garden on the south side of the Physical Sciences Complex. The garden features an installation of solid aluminum cylinders that were the cores of gravitational wave detectors that were invented, built and operated by Weber. In 2019, Professor Emeritus Charles Misner and his wife, Susanne, established the Weber Endowment for Gravitational Physics to support research related to gravitational waves. Steve RolstonSteve Rolston

While department chair, Rolston also founded the Mid-Atlantic Quantum Alliance, which aims to build a vibrant and diverse local ecosystem to support quantum innovation, and co-founded the Quantum Technology Center, which aims to translate quantum physics research into innovative technologies.

During the COVID-19 pandemic, Rolston led the department in running in-person lab courses and research labs without a single case of community transmission. 

“It has been a privilege to be chair of physics for the last five years with our powerhouse faculty who have continued to make UMD Physics a leader,” Rolston said. “I am particularly impressed at how well we weathered the pandemic, a testament to the strength of our staff, students and faculty, and expect great things in the future as we exit from this difficult time.”

Rolston served as associate chair of the department from 2006 to 2009 and as co-director of the Joint Quantum Institute (JQI)—a research partnership between UMD, the National Institute of Standards and Technology (NIST), and the Laboratory for Physical Sciences—from 2008 to 2017. 

In his personal research, Rolston uses ultracold atoms created through laser cooling to study a variety of quantum phenomena. He develops simulators of disordered solid-state systems, works to understand how dissipation can be useful in quantum systems, creates strong quantum connections between atoms and photons, and generates the building blocks for a network of quantum devices.

He is a fellow of the American Association for the Advancement of Science, the American Physical Society and The Optical Society. In addition, Rolston received the university’s Kirwan Undergraduate Education Award in 2014 in recognition of his outstanding achievement in engaging undergraduates in science education.

Rolston earned his bachelor’s degree from Wesleyan University and Ph.D. in nuclear physics from the State University of New York at Stony Brook. After completing postdoctoral fellowships in atomic physics at the University of Washington and Harvard University, he spent 15 years as a staff scientist in the lab of Nobel laureate Wiilliam Phillips at NIST. 

 

Kollár Receives CAREER Award

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Category: Department News
Published: Thursday, June 17 2021 05:33

Assistant Professor Alicia Kollár has received a prestigious Faculty Early Career Development (CAREER) award from the National Science Foundation (NSF) for a proposal aimed at developing a new window into the physics of particles interacting inside of materials and performing educational outreach. The award will provide $675,000 of funding over five years for her proposal titled “Engineering Interacting Photons in Superconducting-Circuit Lattices.”

Kollár, who is a Fellow of the Joint Quantum Institute and the Quantum Technology Center, will use the funds to investigate new physics that might be revealed by making particles of light (called photons) behave more like particles of matter (like electrons). Her plan is to tailor environments for photons by combining superconducting components into specialized circuits. This project builds on Kollár’s previous research that showed that these types of superconducting circuits can simulate material properties and even abstract mathematical spaces that can’t fit into normal space.

“I am thrilled to receive this award and the opportunities that it brings,” Kollár says. “Previously we showed that superconducting circuits have the ability to take photons into regimes where no other laboratory particles had gone before. The support of the NSF will enable us to truly dig into harnessing these unique circuits.”Alicia Kollár standing next to a dilution refrigerator in her lab. (Credit: Alicia Kollár)Alicia Kollár standing next to a dilution refrigerator in her lab. (Credit: Alicia Kollár)

The superconducting circuits allow Kollár and colleagues to artificially create and investigate material properties and particle interactions that are difficult or impossible to access in a material. With this window into the lives of sub-atomic particles, Kollár hopes to gain insights into the fundamental building blocks of the materials that make up the world, particularly the influence of a material environment on how multiple particles interact with each other.

The new research will study how qubits—quantum bits that are the elemental foundation of quantum computer information storage—can be incorporated to mediate the interactions between photons and give researchers more adaptability when performing experiments.

As part of the award, Kollár will also work to make seminars about atomic, molecular and optical physics and quantum physics more accessible to undergraduate students and other audiences that lack expertise on the topics. She plans to build on the accessibility of the online Virtual AMO seminars(link is external) by incorporating online, small-group discussions that can provide background information, context and clarification and can promote follow-up conversations. These discussions are intended as an opportunity for physicists to develop interdisciplinary communication skills and for a non-physicist audience to have easy access to more context and thorough explanations than are generally provided in a large seminar setting.

 “The online seminars that sprung up in response to COVID have shown that presentations about cutting edge research can be made available to a much broader group of people than traditionally had access,” Kollár says. “We are very excited to develop new ways to augment this content and allow people to engage with it, learning the language and context of modern quantum research.”

The CAREER award is the NSF’s most prestigious reward for early-career faculty. Recipients’ activities are intended to establish a foundation for them to be leaders in integrating education and research.

Original story by Bailey Bedford: https://jqi.umd.edu/news/kollar-receives-national-science-foundation-career-award

Shawhan Named a Distinguished Scholar-Teacher

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Category: Department News
Published: Monday, May 24 2021 11:07

Peter Shawhan has been named a University of Maryland Distinguished Scholar-Teacher. The award honors faculty of outstanding scholarly accomplishment and excellence in teaching. He will give his DST lecture, The Simple (and Not-So-Simple) Physics of Detecting Gravitational Waves, on Tuesday, December 7, 2021 at 4 p.m. in lecture hall 1412 of the John S. Toll Physics Building. Refreshments precede the event, starting at 3:30 p.m.

"Peter clearly deserves this recognition," said physics chair Steve Rolston. "He has been a key contributor to LIGO's celebrated successes, and we are just beginning to reap the rewards of his great contributions to multi-messenger astronomy," which integrates data from previously-disconnected satellites and observatories. "Peter is equally dedicated to our education mission. He was an excellent graduate director for five years, and has been a great teacher across the range of our course offerings. Last fall, he designed and launched PHYS 172, Succeeding in Physics, to help students who might otherwise struggle with the major's requirements to build better understanding."

Shawhan is also chair of the department's newly-established Climate Committee, which is working to ensure a welcoming and supportive environment for all.Peter ShawhanPeter Shawhan

“I’m fortunate to have an amazing group of colleagues who made LIGO a reality, after decades of careful preparations,” said Shawhan.  “It really works!  And now we are routinely detecting gravitational wave events from galaxies far, far away and getting important astrophysics insights from them.  But one of the great things about being a professor is that I can also talk about current research in my classes, connecting it with the course material and sharing some of the excitement of actually using physics to do revolutionary things.”

Shawhan received his Ph.D. in physics from the University of Chicago, and was appointed a Millikan Prize Postdoctoral Fellow at the California Institute of Technology. He continued at Caltech as a Senior Scientist before accepting a faculty appointment with UMD Physics in 2006.  Shawhan’s primary research for the past 20 years has been direct detection of gravitational waves with the LIGO and Virgo detectors, and he has held numerous leadership positions within the LIGO Scientific Collaboration, including Burst Analysis Working Group Co-Chair (2004-11) and LSC Data Analysis Coordinator (2017-present).  He was instrumental in establishing and nurturing a program of sharing prompt information about gravitational-wave event candidates with astronomers to allow them to look for corresponding signals in their instruments.  That groundwork enabled a remarkably rich campaign of astronomical follow-up observations and study, spanning the whole electromagnetic spectrum, when LIGO and Virgo detected the first binary neutron merger event, in August 2017.  That first event has provided scientific breakthroughs in fundamental physics, neutron star properties, high-energy astrophysics, and cosmology.  LIGO and Virgo are currently being upgraded and preparing to report more event candidates as they are identified.

Shawhan served as the Physics Associate Chair for Graduate Education from 2014-19 and is a member of the UMD-Goddard Joint Space-Science Institute and its Executive Committee. In addition, he is a past Chair of the Division of Gravitational Physics of the American Physical Society and was elected an APS fellow in 2019. Shawhan received the Richard A. Ferrell Distinguished Faculty Fellowship from the UMD Department of Physics in 2016. He was the recipient in 2018 of the Kirwan Faculty Research and Scholarship Prize and the USM Board of Regents Faculty Award for Excellence in Research.

Time Delay Acquires a New Dimension

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Category: Research News
Published: Wednesday, May 19 2021 12:33

Physicists love to do scattering experiments.  When they are trying to figure out a new force of nature, or discover a new particle, they fire up the accelerator and shoot tiny particles at their target, and measure what comes out.  Usually they carefully measure the energy and momentum of the incident and exiting particles, and try to learn about what took place in the target from that.  All of this information is summarized in an elegant quantity known as the Scattering Matrix. 

Schematic of time delay for scattering of a wave packet from a real-life ray-chaotic billiard.  The symmetric and smooth wave packet goes in to the scattering region through one scattering channel and emerges later from another channel as a delayed and strongly distorted pulse.  The complex time delay accounts for these changes.Schematic of time delay for scattering of a wave packet from a real-life ray-chaotic billiard. The symmetric and smooth wave packet goes in to the scattering region through one scattering channel and emerges later from another channel as a delayed and strongly distorted pulse. The complex time delay accounts for these changes.

Less studied is the question of how long the particle lingers in the interaction region before coming out.  This quantity is called time delay, and it has been studied since the early days of nuclear physics.  However, time delay never graduated from the confines of its original home, namely relatively simple quantum mechanical settings where the corrupting influences of “dissipation,” “de-coherence” and “dephasing” do not come into play.  Because of the rather restrictive conditions under which time delay was originally defined, it has always been taken to be a real, and generally positive, number.  In a paper published on May 18, 2021 in Physical Review E, Lei Chen, Steve Anlage,Illustration of complex time delay associated with a single resonant mode of a complex scattering system known as a quantum graph.  Shown is the evolution of the complex time delay as a function of frequency near the resonance, illustrating how the real and imaginary parts of the time delay form a closed figure in the complex time-delay plane.  The cases of two resonances, one with small loss and another with large loss, are shown for illustration.  These results are from a simulation of the quantum graph.Illustration of complex time delay associated with a single resonant mode of a complex scattering system known as a quantum graph. Shown is the evolution of the complex time delay as a function of frequency near the resonance, illustrating how the real and imaginary parts of the time delay form a closed figure in the complex time-delay plane. The cases of two resonances, one with small loss and another with large loss, are shown for illustration. These results are from a simulation of the quantum graph. and Yan V. Fyodorov describe having generalized this time delay to real-world situations where there is dissipation and de-phasing, and created a very useful complex version of time delay.  This generalized time delay has a real part that can be positive or negative, and an imaginary part, which can also have either sign. 

The real part still tells something about the lingering time of the particle, but the imaginary part conveys how much the waves that describe the particle quantum mechanically are distorted by the lossy and disruptive scattering system.  This new quantity gives tremendous insights into the microscopic physics of the scattering system by cleverly encoding information about locations of the poles (infinities) and zeros of the scattering matrix.  Knowing all of those locations is equivalent to knowing essentially everything there is to know about the scattering process.  The exciting thing is that now complex time delay can be used to uncover fundamental properties of scattering systems that arise not just in quantum physics, but also in electromagnetic and acoustic reverberant systems, and the world of the small, but not too small, called mesoscopic physics.

More recently, in a paper published on November 12, 2021 in Physical Review Letters, the same authors have applied their generalized time delay concept to complex scattering systems with many overlapping resonances and zeros.  By looking at the statistical properties of the time delays, they utilized concepts from random matrix theory to reveal information about the distribution of poles in the complex frequency plane.  This deepens the understanding of a broad variety of complicated wave scattering systems, and provides a quantitative tool to characterize and classify them.

To read more, see the paper  "Generalization of Wigner time delay to subunitary scattering systems", in the 1 May 2021 issue of Physical Review E (Vol. 103, No. 5): https://link.aps.org/doi/10.1103/PhysRevE.103.L050203
DOI: 10.1103/PhysRevE.103.L050203

And the follow-up paper “Statistics of Complex Wigner Time Delays as a counter of S-matrix poles: Theory and Experiment,” in the 12 November 2021 issue of Physical Review Letters (Vol. 127, No. 20): https://doi.org/10.1103/PhysRevLett.127.204101
DOI: 10.1103/PhysRevLett.127.204101

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  4. Research Team Describes "Somersaulting" Photons

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