Fall 2021

October 22, 2021 (Friday) 4:00-5:00p.m.
Speaker: Jens Boos, William & Mary Physics
Host: M. Sher
Title: So black holes exist. Now what?
Abstract: The 2020 Nobel prize was awarded for the theoretical prediction of black holes and the discovery of a supermassive compact object at the center of our galaxy. Three years prior, in 2017, it was awarded for the discovery of gravitational waves caused by the collision of two astrophysical black holes. We even have a photo of a black hole. So, while we still cannot poke a black hole with a stick to see what it does, there is ever-increasing evidence that these fascinating objects really exist in our Universe.

But what does that mean? Where can we go from here?

After a brief introduction to the basic principles of General Relativity and black hole physics, I will explore current and future research directions in black hole physics. On the experimental side this includes testing Einstein’s theory of gravity with black hole shadows, the search for new ultralight particles from gravitational wave signals, the search for hypothetical microstructures close to black hole horizons, and more. On the theoretical side, black holes are expected to radiate and eventually decay, once quantum aspects are considered, with fascinating implications for the interplay of black holes and quantum information.

We are probably just at the beginning of a new era of black hole research, now that these enigmatic objects have been observed in our Universe, and it will be exciting to see what new insights the next decades will bring, both experimental and theoretical.

October 29, 2021 (Friday) 4:00-5:00p.m.
Speaker: Laurie McNeil, University of North Carolina at Chapel Hill
Host: M. Sher
Title: LEARNING BY DOING RATHER THAN TEACHING BY TELLING
Abstract: All of us were once science and engineering students before we became professors. We know that the core of our learning took place when we figured out how to apply technical concepts as we wrestled with solving problems, not when our instructors lectured at us. The studio mode of instruction reflects this reality. In traditional lecture-based teaching the instructor transfers information in the classroom and the students struggle on their own to apply that information to specific situations (in homework). Studio-based instruction reverses this—the information transfer takes place outside of class, and class time is used for the students to work collaboratively as they engage in structured hands-on, minds-on application of that information while the instructor provides support. At UNC-CH we have transformed all of our introductory physics courses to use studio-based pedagogy, and as a result we have seen impressive gains in student understanding. This has led us to begin to transform the way we teach upper-division courses as well. I will describe how my department teaches now, and how we accomplished this large-scale transformation.

November 5, 2021 (Friday) 4:00-5:00p.m.
Speaker: Mumtaz Qazilbash, William & Mary Physics
Host: M. Sher
Title: Recent insights into the metal-insulator transition of vanadium dioxide (VO₂)
Abstract: Metal-insulator transitions are among the most fascinating and least understood phenomena in condensed matter physics. Metal-insulator transitions lead to significant changes in the electronic conductivity and optical properties, and are generally accompanied by structural and magnetic transformations due to a complex interplay between charge, spin, orbital, and lattice degrees of freedom. The thermally-driven metal-insulator transition (MIT) in bulk vanadium dioxide (VO₂) is accompanied by a structural distortion that leads to pairing of all the vanadium atoms in the insulating phase. This V-V pairing has long been thought critical to the emergence of insulating behavior. We shall present our latest experiments on ultrathin VO₂ films grown on TiO₂ substrates. We demonstrate that the MIT in ultrathin VO₂ films occurs without the V-V structural distortion. Our results establish a route to a purely electronic MIT that is driven by electron-electron interactions. We shall also present our recent experiments and results on infrared nano-imaging and nano-spectroscopy of VO₂ films. The development of table-top, broadband infrared light sources in my lab has enabled nano-spectroscopy experiments on VO₂ and other materials.

December 3, 2021 (Friday) 4:00-5:00p.m.
Speaker: Olivier Pfister, UVA
Host: J. Stevens
Title: Toward quantum simulation of particle physics with quantum optics
Abstract: As envisioned by Feynman in 1981, an N-qubit quantum processor could be used to simulate quantum systems over the corresponding 2^N-dimensional Hilbert space and therefore provide such quantum simulation with an exponential increase in computational power. (For example, one can think of simply measuring the energy of a quenched, specifically designed quantum system whose ground level is too hard to calculate.) An interesting avenue for quantum simulation was formulated by Jordan, Lee, and Preskill [1] who proposed _efficient_ quantum sampling for accessing scattering amplitudes in quantum field theory. This original proposal was subsequently translated from the discrete qubit encoding to the continuous-variable qumode encoding [2], which can use quantum optical fields and is better suited to quantum optics [3]. In this talk, I will present these ideas and a current collaborative effort led by Jefferson Laboratory and involving William and Mary, Old Dominion University, and the University of Virginia, and I will elaborate on how my group's experimental advances on scalable quantum computing can be put to use in that context.

This work is supported by NSF grants PHY-1820882 and PHY-2112867 and by the Jefferson Lab LDRD project No. LDRD21-17 under which Jefferson Science Associates, LLC, manages and operates Jefferson Lab.

[1] S.L. Jordan, K.S. Lee, and J. Preskill, Quantum Algorithms for Quantum Field Theories, Science 336, 1130 (2012).

[2] K. Marshall, R. Pooser, G. Siopsis, and Ch. Weedbrook, Quantum simulation of quantum field theory using continuous variables, Phys. Rev. A 92, 063825 (2015).

[3] O. Pfister, Continuous-variable quantum computing in the quantum optical frequency comb, J. Phys. B, Atomic, Molecular and Optical Physics 53, 012001 (2019).

BIO:
Olivier Pfister received the B.S. in Physics from Université de Nice, France, in 1987, and the M.S. and the Ph.D. in Physics from Université Paris-Nord, France, in 1989 and 1993. In 1994, he was a lecturer at INM, Conservatoire National des Arts et Métiers, in Paris. He was then a research associate with John L. Hall at JILA, University of Colorado (1994-97) and with Daniel J. Gauthier at Duke University (1997-99). In 1999, he joined the faculty of the University of Virginia, where he is now a professor of physics. Olivier Pfister is a fellow of the American Physical Society and a member of Optica, IEEE, and SPIE. His general research area is atomic, molecular, and optical (AMO) physics, with past interests in quantum measurements at the ultimate precision, ultrahigh resolution laser spectroscopy, symmetry effects in small molecules, nonlinear optics for optical frequency chains, and two-photon lasers. His current research interest is quantum computing with light.

December 10, 2021 (Friday) 4:00-5:00p.m.
Speaker: Xiangdong Ji, University of Maryland
Host: K. Orginos
Title: Exposing the hidden glue of the mundane world
Abstract: Gluons in the low-energy strong-interaction world are like Mafias in Sicily, allegedly control everything but there is no hard evidence. The potentially-detectable glues are confined to a small region of space of order one fermi, and are completely blind to electromagnetism and weak interactions. However, they contribute significantly to the momentum, mass, spin and other properties of the protons and neutrons---the dominant matter component in our visible universe. In this talk, I will discuss how to expose them through special processes in electron scattering on nucleons and nuclei at JLab and future EIC. I will also describe theoretical efforts to compute their effects through large-scale lattice QCD simulations.