Events at Physics

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Events During the Week of March 6th through March 13th, 2022

Monday, March 7th, 2022

No events scheduled

Tuesday, March 8th, 2022

R. G. Herb Condensed Matter Seminar
Simulating quantum many-body phenomena with superconducting qubits
Time: 10:00 am - 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Roman Kuzmin, University of Maryland
Abstract: Superconducting circuits are ubiquitous in quantum simulations, computing, and metrology. In this talk, I will show a superconducting circuit platform extended to the extreme, in which the circuits actually become insulating. Remarkably, such nominally insulating circuits are a valuable resource. They create a tunable high-impedance environment and facilitate exceptionally strong interactions between photons and superconducting qubits. This opens up new directions for analog quantum simulations of interacting many-body problems, with examples ranging from quantum phase transitions to many-body localization. In particular, I will start with the demonstration of a dissipative quantum phase transition in a Josephson junction facing an Ohmic environment. Despite many experimental attempts, the existence of such a transition remains controversial. Using the high-impedance circuit environment, I will present evidence of the transition with a conceptually new approach, which relies on monitoring environmental degrees of freedom. A similar approach applies to analog quantum simulations of other strongly interacting models, which I will illustrate on two quantum impurity models relevant to the physics of Luttinger liquids and the Kondo effect. In the latter case, interactions induced by a quantum impurity in a finite size system allow us to observe the phenomenon of many-body localization. Finally, I will argue that the high-impedance circuit platform can contribute to the development of various areas of quantum science and technology.
Host: Mark Saffman
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A Brief History of Time(keeping): Optical atomic clocks and their applications
Time: 7:00 pm - 8:00 pm
Place: UW Space Place, 2300 S. Park St or live on their YouTube Channel. See for details.
Speaker: Shimon Kolkowitz, UW–Madison Physics
Abstract: What would you do with a clock so accurate that it won’t gain or lose one second over the entire age of the universe? You could use it to test the theory of relativity and search for dark matter, among other things. Our speaker will help us understand how physicists use such amazing timekeepers for fundamental research.
Host: UW Space Place
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Wednesday, March 9th, 2022

Physics ∩ ML Seminar
Rethinking AutoML for Diverse Tasks
Time: 11:00 am - 12:15 pm
Place: Chamberlin 5280 (Zoom link for those attending online: )
Speaker: Nicholas Roberts, University of Wisconsin-Madison
Abstract: The underlying motivation of automated machine learning, or AutoML, is to automate away tasks which require machine learning (ML) expertise--such that experts in domains other than ML can reap its potential benefits for their problems. These automation efforts are mostly siloed within the machine learning community by their reliance on the tasks or domains which are most familiar to machine learning experts--classification tasks in computer vision or NLP. Unfortunately, this neglects the heavy-tail of tasks and domains that practitioners might care about and directly contradicts a core premise of AutoML: usefulness to non-ML-experts. In this talk, we present two of our recent directions which make progress toward alleviating this issue by expanding into under-explored domains and problem types. In the first half of the talk, we will present a class of search spaces over deep neural network operations which can specialize a given CNN architecture to any domain of interest by generalizing the convolution theorem from signal processing. In the second half of the talk, we will discuss the limitations of weak supervision for semi-automated dataset curation and show how to generalize weak supervision so that it can be applied to any label space equipped with a distance metric, as opposed to categorical labels alone.
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Thursday, March 10th, 2022

R. G. Herb Condensed Matter Seminar
Skyrmion pairing: a topological route to superconductivity
Time: 10:00 am - 11:00 am
Place: 5310 Chamberlin Hall
Speaker: Shubhayu Chatterjee, University of California Berkeley
Abstract: Atomically thin Van der Waals materials have emerged as a highly versatile platform to advance our understanding of quantum matter driven by strong electron correlations. Recent experimental breakthroughs in stabilizing few-layered graphene structures with a “magic” relative twist between layers has led to the discovery of a wide variety of correlated states ranging from magnetism to superconductivity. Despite compelling experimental evidence for unconventional superconductivity, the glue which binds electrons into Cooper pairs remains a mystery. In this talk I will propose a novel resolution: the Cooper pairs are composed of electrically charged topological spin textures called “skyrmions,” rather than electrons. First proposed by Tony Skyrme to model baryons in particle physics, I will explain how their topological properties can give rise to superconductivity in an electronic model with purely repulsive interactions, and without recourse to phonons which are conventionally responsible for pairing.
Host: Robert McDermott
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Seminar at Bergmann Group
A two-state picture of water and possible consequences
Time: 4:30 pm - 5:30 pm
Place: Room 1306 Chamberlin Hall
Speaker: Professor Lars Pettersson, University of Stockholm
Host: Uwe Bergmann
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Friday, March 11th, 2022

Theory Seminar (High Energy/Cosmology)
Gravitational Wave Probes of Axion Rotations Responsible for Dark Matter and Baryon Asymmetry
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Raymond Co, University of Minnesota
Abstract: We established a paradigm where the (QCD) axion’s novel cosmological evolution, a rotation in the field space, gives rise to dark matter and the baryon asymmetry. The axion rotations also provide a natural origin for a kination era, where the total energy density is dominated by the kinetic term of the axion field, preceded by an early era of matter domination. We investigate the effects of this cosmological scenario on the spectrum of possible primordial gravitational waves from inflation or cosmic strings and find that the spectrum features a triangular peak. As a result, future gravitational wave observations can probe the viable parameter space of kination, including regions that produce axion dark matter by the kinetic misalignment mechanism or the baryon asymmetry by axiogenesis. Lastly, the axion rotation may also source the cosmic perturbations with an observable amount of non-Gaussianity.
Host: George Wojcik
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Physics Department Colloquium
CFS and the new public-private fusion energy landscape
Time: 3:30 pm
Place: 2241 Chamberlin Hall
Speaker: Robert Mumgaard, CFS Energy
Abstract: With the successful demonstration of its 20T, full-scale toroidal field model coil in September 2021, Commonwealth Fusion Systems (CFS) is now entering the SPARC Era. Over the next four years, CFS and its partners will build, commission and operate the SPARC net-energy tokamak. In parallel, CFS will demonstrate the fusion technology advances required for the first generation of the ARC commercial fusion power plant, which is due to be commissioned in the early 2030’s.This is motivated by the market requirements of the global clean energy transition, and in particular the requirements for fusion to take its place as an industrial energy concern capable of combating climate change. CFS as a company and fusion as a technology are well positioned to reach these goals. CFS has raised over $2b in private funding to date and built a global network of over 40 partner institutions. CFS' roadmap is highly aligned with the strategic goals identified by the US fusion community and National Academy of Sciences, and is involved in multiple public-private partnerships, including many supported in part by competitive DOE awards. Supported by an ARPA-E award, CFS is building 20T all-HTS end coils for the University of Wisconsin's axisymmetric mirror (or WHAM) experiment, demonstrating the speed and flexibility that private companies can bring to the academic ecosystem. In this talk, CFS’ CEO, Bob Mumgaard, will present an overview of the new public-private fusion landscape, CFS’ current status and position in that landscape, and the open problems and challenges on the path to commercial fusion energy.
Host: Cary Forest
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Soundswaves: small - medium - large
Time: 7:30 pm - 9:30 pm
Place: H.F. DeLuca Forum, Discovery Building
Speaker: Brian Rebel and others, UW–Madison Physics and other UW depts
Abstract: SoundWaves looks at the ideas of size and scale. How can tiny particles of matter have a big effect in our universe? How big is infinity? How can a small branch of economic theory explain behaviors outside the scope of economics? How can a collection of individual musical instruments become one instrument that revolutionized the direction of the music we listen to today? Find out in our first event of 2022.

Featuring: Brian Rebel, physics; Raymond Deneckere, economics; Tullia Dymarz, mathematics; Daniel Grabois, SoundWaves curator, music; and Matthew Endres, music.

This event will be held at the Discovery Building and will also be livestreamed on Zoom.

Register at:
Host: WARF
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Saturday, March 12th, 2022

Academic Calendar
Spring recess
Abstract: *Note: actual end time may vary.* March 12-20, 2021
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Sunday, March 13th, 2022

Academic Calendar
Spring recess
Abstract: *Note: actual end time may vary.*
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Wisconsin Quantum Institute
Quantum education open house at APS March Meeting
Time: 4:00 pm - 7:00 pm
Place: Visit for more info
Speaker: various, various
Abstract: Inviting all educators and members of the community to the Quantum Education Open House, taking place before the 2022 APS March Meeting, to learn about quantum education efforts and workforce development programs. The Open House will include information and demonstrations from a range of programs.
Host: CQE
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