Colloquia

Colloquium
Friday, January 28, 2022
3:30 PM
Physics Building, Room 204

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"TBA"


Professor Lloyd Knox , UC Davis
[Host: Prof. Genya Kolomeisky]
ABSTRACT:

TBA

Colloquium
Friday, January 21, 2022
3:30 PM
Physics Building, Room 204

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"TBA"


David Nichols , University of Virginia - Department of Physics
[Host: Professor Despina Louca]
ABSTRACT:

TBA

Attend virtually via Zoom: 
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, December 3, 2021
3:30 PM
Physics Building, Room TBA
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"TBA"


Ian Spielman , Joint Quantum Institute
[Host: Prof. Dima Pesin]
ABSTRACT:

TBA

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https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp
 

Friday, November 19, 2021
3:30 PM
Physics Building, Room 204

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"Analogue gravity in cold atom and condensed matter systems "


Dan Sheehy , Louisiana State University
[Host: Cass Sackett]
ABSTRACT:

In recent years there has been much interest in the field of "analogue gravity", in which cosmological or astrophysical phenomena like Hawking radiation are mimicked in a laboratory experiment.  At LSU, my research group in cold atom/condensed matter theory became interested in this field, motivated by the recent experiment of Eckel and collaborators, [Phys. Rev. X 8, 021021 (2018)] who used a rapidly expanding Bose-Einstein condensate (BEC) to reproduce the inflationary regime of the early universe.  I will present our work on the physics of inflation in expanding BEC's, and discuss other setups to detect analogue gravity phenomena like the Unruh effect.  

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https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, November 12, 2021
3:30 PM
Physics Building, Room 204

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"Physics motivations for future colliders"


Tao Han , University of Pittsburg
[Host: Professor P.Q. Hung]
ABSTRACT:

With the milestone discovery of the Higgs boson at the CERN Large Hadron Collider (LHC), high energy physics has entered a new era. The completion of the “Standard Model” (SM) implies, for the first time ever, that we have a relativistic, quantum-mechanical, self-consistent theoretical framework, conceivably valid up to exponentially high energies, even to the Planck scale. Yet, the SM leaves many unanswered questions both from the theoretical and observational perspectives, including the nature of the electroweak superconductivity and its phase transition, the hierarchy between the particle masses and between the observed scales, the nature of dark matter etc. There are thus compelling reasons to believe that new physics beyond the SM exists. We argue that the collective efforts of future high energy physics programs, in particular the future colliders, hold great promise to uncover the laws of nature to a deeper level. 

Attend virtually via Zoom: 
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Friday, November 5, 2021
3:30 PM
Physics Building, Room 204

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"Atomtronics for Quantum Sensing"


Malcolm Boshier , Los Alamos National Lab
[Host: Professor Cass Sackett]
ABSTRACT:

TBA

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Friday, October 29, 2021
3:30 PM
Physics Building, Room 204

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"Exploring Gravitational Wave and Dark Matter Physics with the 100-meter-tall MAGIS-100 Atom Interferometer"


Professor Tim Kovachy , Northwestern University
[Host: Prof. Bob Hirosky]
ABSTRACT:

Atom interferometers exploit spatially delocalized quantum states to make a wide variety of highly precise measurements.  Recent technological advances have opened a path for atom interferometers to contribute to multiple areas at the forefront of modern physics, including searches for wave-like dark matter, gravitational wave detection, and fundamental quantum science.  In this colloquium, I will describe MAGIS-100, a 100-meter-tall atom interferometer being built at Fermilab to pursue these directions.  MAGIS-100 will serve as a prototype gravitational wave detector in a new frequency range, between the peak sensitivities of LIGO and LISA, that is promising for pursuing cosmological signals from the early universe and for studying a broad range of astrophysical sources.  In addition, MAGIS-100 will search for wave-like dark matter, probe quantum mechanics in a new regime in which massive particles are delocalized over macroscopic scales in distance and time, and act as a testbed for advanced quantum sensing techniques.  Finally, I will discuss the potential and motivation for follow-on atomic detectors with even longer baselines.

 

Attend virtually via Zoom: 
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Friday, October 22, 2021
3:30 PM
Physics Building, Room 204

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"Quantum Many-Body Physics of Superconducting Qubits"


Professor Leonid Glazman , Yale University
[Host: Dima Pesin]
ABSTRACT:

The ongoing development of superconducting qubits has brought some basic questions of many-body physics to the research forefront, and helped solve several of them. I will address two effects in quantum condensed matter highlighted by the development of a fluxonium qubit. The first one is the so-called cosine-phi problem stemming from the seminal paper of Brian Josephson. It predicted the phase dependence of the dissipative current across the Josephson junction. A fluxonium qubit enabled the observation of the effect, after nearly 50 years of unsuccessful attempts by other techniques. The second one is inelastic scattering ("splitting") of a microwave photon by quantum fluctuations of phase across a Josephson junction. This effect is the elementary mechanism driving the Schmid transition, which predicts a collapse of the Josephson current in a junction influenced by a dissipative environment.

Attend virtually via Zoom: 
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, October 8, 2021
3:30 PM
Physics Building, Room 204

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" Muon magnetic anomaly: probing the innermost nature of vacuum"


Professor Dinko Počanić , University of Virginia - Department of Physics
[Host: Prof. Gordon Cates]
ABSTRACT:

Marking the semi-anniversary of the Fermilab Muon g−2 experiment (E989) Run 1 result, this colloquium will review the current status of the muon magnetic anomaly, the inferred evidence of possible particles outside the Standard Model (SM), and future prospects in this active research field.

The intrinsic magnetic field of a simple object, such as a compass needle, is expressed in terms of its magnetic moment.  The magnetic moment of a point particle, such as the electron, is predicted by relativistic quantum mechanics to be g = 2, in convenient dimensionless units.  For the electron, this prediction fails at the part-per-thousand level; the resulting magnetic anomaly, ae = (g − 2)/2, is due to the electron’s couplings to virtual particles excited in the vacuum.

Muon, the electron’s 200 times heavier cousin, experiences far stronger couplings to massive virtual particles, including possible non-SM exotics. The SM provides a prediction for the muon magnetic anomaly aµ with sub-ppm precision. Hence, a comparably precise measurement of aµ offers a uniquely sensitive test for the presence of non-SM particles in nature. For almost 20 years a tantalizing discrepancy of ∼ 3 – 4σ has persisted between the measurements of aµ, and the SM calculations. The Fermilab Muon g−2 Run 1 result brings a much awaited update to this test, with much more to come.


Attend virtually via Zoom: 
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Friday, October 1, 2021
3:30 PM
Physics Building, Room 204

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"Rotation sensing with an atom-interferometer gyroscope"


Professor Cass Sackett , University of Virginia - Department of Physics
[Host: Gordon Cates]
ABSTRACT:

Precision rotation sensing is useful for navigation, geophysics, and tests of fundamental physics. Atom interferometers provide, by some measures, the most sensitive method for rotation sensing achieved to date. However, the best performance requires freely falling atoms in a large experimental apparatus. Many applications, such as navigating a vehicle, will benefit from a more compact geometry. One method to achieve this is by using trapped atoms that are suspended against gravity. We have implemented such an interferometer and used it to measure a rotation rate comparable to that of the Earth. The most recent iteration of the interferometer has demonstrated improvements by a factor of ten in rotation sensitivity and trap stability. A second new apparatus reduces the scale of the vacuum chamber and optical system to roughly the size of a microwave oven.

VIDEO:

Attend virtually via Zoom: 
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Friday, September 17, 2021
3:30 PM
Physics Building, Room 204

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"Inside the Proton: science fact, speculation, and the stuff of science fiction"


Professor Gordon Cates , University of Virginia - Department of Physics
[Host: Kent Paschke]
ABSTRACT:

Whereas the structure of the atom has been  understood for many years, the internal structure of the proton (and neutron) is the subject of active research.  Understanding the nucleon is difficult because its structure is governed by quantum chromodynamics, or QCD, which has not been solved exactly in the non-perturbative or low-energy regime.  The proton's structure is intriguing, however, for many reasons.  For example, we think of the proton as being made of three quarks, but the mass of those quarks only accounts for about 1% of the proton's mass.  The remaining 99%, and hence 99% of the known mass in the universe, is due to exotic effects associated with the QCD vacuum.  While a great deal of work remains to be done, the way in which we visualize the proton has changed dramatically since the discovery of quarks.  Just as the structure of the atom was unveiled early in the 20th century, the structure of the proton is being unveiled in the first decades of the 21st century.  Another intriguing aspect of the proton arises from the fact that QCD is the only theory in nature that has essentially no free parameters. String theory, that attempts to unify our understanding of gravity and the quantum world, grew out of early efforts to understand the strong interaction.  Since string theory deals with the topology of space and time, it is tempting to believe that a deep understanding of the proton may one day provide a window into even more fundamental questions. The colloquium will cover some recent developments in our understanding of the nucleon, as well as providing a glimpse of where this rich area of research is heading in upcoming years.

VIDEO:

Attend virtually via Zoom: 
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Friday, September 10, 2021
3:30 PM
Physics Building, Room 204

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"Stirring by staring: Induced non-equilibrium states by measurements in quantum systems"


Israel Klich , University of Virginia - Department of Physics
[Host: Despina Louca]
ABSTRACT:

In quantum mechanics, the role of an observer is fundamentally different from that of a classical observer.  The quantum mechanical observer necessarily plays an active role in the dynamics of the system that it is observing.  This apparent difficulty may be turned into a tool to drive an initially trivial system into a complicated quantum many-body state simply by observing it.  I will present two remarkable examples of states induced by measurement. In the first, we examine the role of a moving density measuring device interacting with a system of fermions, and in particular, show that it would leave behind a wake of purely quantum origin. In the second example, inspired by the recent invention of topological Floquet insulators, we will see how a suitably chosen set of density measurements, repeated periodically, will induce robust chiral edge motion on a lattice of free fermions. Our examples show how quantum mechanical observation can be added as a versatile tool to the arsenal of quantum engineering in condensed matter systems.

VIDEO:
Click on the following link to attend the online colloquium:
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, February 12, 2021
2:00 PM
Online, Room via Zoom
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"Complexity of magnetic patterns and self-induced spin-glass state"


Prof. Mikhail Katsnelson , Radboud University of Nijmegen, The Netherlands,
[Host: Dima Pesin]
ABSTRACT:

The origin of complexity remains one of the most important and, at the same time, the most controversial scientific problems. Earlier attempts were based on theory of dynamical systems but did not lead to a satisfactory solution of the problem. I believe that a deeper understanding is possible based on a recent development of statistical physics, combining it with relevant ideas from evolutionary biology and machine learning.

Using patterns in magnetic materials as the main example, I discuss some general problems such as (a) a formal definition of pattern complexity [1]; (b) self-induced spin glassiness due to competing interactions as a way to interpret chaotic patterns [2]; (c) multi-well states intermediate between glasses and ordinary ordered states and their relevance for the problem of long-term memory in complicated systems [3]; and (d) complexity of frustrated quantum spin systems [4]. I will also review a very recent experimental observation of self-induced spin-glass state in elemental neodymium [5].

[1] A. A. Bagrov, I. A. Iakovlev, A. A. Iliasov, M. I. Katsnelson, and V. V. Mazurenko, Multi-scale structural complexity of natural patterns, PNAS 117, 30241 (2020).
[2] A. Principi and M. I. Katsnelson, Spin glasses in ferromagnetic thin films, Phys. Rev. B 93, 054410 (2016); Self-induced glassiness and pattern formation in spin systems due to long-range interactions, Phys. Rev. Lett. 117, 137201 (2016).
[3] A. Kolmus, M. I. Katsnelson, A. A. Khajetoorians, and H. J. Kappen, Atom-by-atom construction of attractors in a tunable finite size spin array, New J. Phys. 22, 023038 (2020).
[4] T. Westerhout, N. Astrakhantsev, K. S. Tikhonov, M. I. Katsnelson, and A. A. Bagrov, Generalization properties of neural network approximations to frustrated magnet ground states, Nature Commun. 11, 1 (2020).
[5] U. Kamber et al, Self-induced spin glass state in elemental and crystalline neodymium, Science 368, eaay6757 (2020).
VIDEO:
Click on the following link to attend the online colloquium:
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, February 5, 2021
3:30 PM
Physics Building, Room via Zoom
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"A fermionic triangular-lattice quantum gas microscope "


Peter Schauss , University of Virginia - Physics Dept.
[Host: Bob Jones]
ABSTRACT:

Geometrically frustrated many-body systems show many interesting emerging phenomena, ranging from kinetic frustration to exotic spin ordering and chiral spin liquid phases. Ultracold atom systems offer great tunability and flexibility to realize such systems in a wide parameter range of interactions, densities, and spin-imbalance.

In this talk, I will present our recent results on site-resolved imaging of ultracold fermionic lithium atoms on a triangular optical lattice.

Degenerate Fermi gases with about one tenth of the Fermi temperature have been realized within a crossed dipole trap and successfully loaded into a two-dimensional triangular optical lattice. To characterize this lattice, we observed Kapitza-Dirac scattering using a molecular Bose-Einstein condensate. Collecting the emitted photons during Raman sideband cooling in the triangular lattice using a high-resolution microscope objective enabled the high-fidelity imaging of individual fermionic atoms in the lattice with single-site resolution.

The next step will be the realization of a triangular lattice Hubbard model by implementing an additional optical lattice to increase interactions.

This novel experimental platform will allow us to study spin and density correlations in the triangular Hubbard model to explore signatures of frustration and spin-hole bound states and may lead to a direct observation of non-vanishing chiral correlations.

VIDEO:
Click on the following link to attend the online colloquium:
https://web.phys.virginia.edu/Private/Covid-19/colloquium.asp

Friday, October 23, 2020
3:30 PM
Online, Room via Zoom
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"Bosonic Quantum Information Processing with Superconducting Circuits"


Professor Liang Jiang , Pritzker School of Molecular Engineering, University of Chicago
[Host: Olivier Pfister]
ABSTRACT:

Bosonic modes are widely used for quantum communication and information processing. Recent developments in superconducting circuits enable us to control bosonic microwave cavity modes and implement arbitrary operations allowed by quantum mechanics, such as quantum error correction against excitation loss errors. We investigate different bosonic encoding and error correction protocols, and provide a perspective on using bosonic quantum error correction for various applications.

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