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Events During the Week of March 17th through March 24th, 2024

Monday, March 18th, 2024

R. G. Herb Condensed Matter Seminar
Quantum skyrmion Hall effect
Time: 12:00 pm - 1:00 pm
Place: 5310 Chamberlin Hall
Speaker: Ashely Cook, Max Planck Institutes for the Physics of Complex Systems and the Chemical Physics of Solids
Abstract: In the quantum Hall effect, a two-dimensional gas of electrons is subjected to an out-of-plane magnetic field and electron transport quantises: the Hall conductivity plateaus at values proportional to integers and rational numbers in units of fundamental constants, with remarkably low error. Shortly after experimental discovery of the quantum Hall effect in 1980, theorists developed a framework explaining this quantization as a consequence of topological phases of matter, or those phases with signatures unaffected by sufficiently small perturbations. In particular, a theory in terms of point charges coupling to external fields beautifully described this physics. A great variety of topological phases have been classified as a consequence of discovery of the quantum Hall effect, but this work has recently led to discovery of topological skyrmion phases of matter, multiplicative topological phases of matter, and finite-size topological phases of matter, which contradict key assumptions of established classification schemes. The discovery of these three sets of topological states necessitates a paradigm shift from the quantum Hall effect framework to that of the quantum skyrmion Hall effect, in which the point charges of the quantum Hall effect are generalised to truly quantum counterparts of topological textures in observable fields, called skyrmions.
Host: Alex Levchenko
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Plasma Physics (Physics/ECE/NE 922) Seminar
"Cylindrical Implosion Experiments at Los Alamos National Laboratory"
Time: 12:00 pm - 1:15 pm
Place: 1227 Engineering Hall
Speaker: Josh Sauppe, LANL (Los Alamos National Laboratory)
Abstract: The advent of high-power laser facilities such as the National Ignition Facility (NIF) has ushered in a new and exciting era in high-energy-density (HED) physics research, and the flexibility of the NIF allows many distinct targets to be fielded beyond the standard indirect-drive inertial confinement fusion (ICF) configuration. Los Alamos scientists are using directly driven cylindrical implosion experiments at the NIF to study hydrodynamic instability growth in regimes relevant to ICF systems, as cylinders enable direct measurements by viewing down the cylinder axis. These physical systems are often modeled in more tractable two-dimensional (2D) simulations with assumed symmetry, but this simplification risks inadvertently masking crucial features. Here, we show experimental evidence of a 3D asymmetry in directly driven cylindrical implosions which was not predicted with 2D modeling, and we accurately reproduce this feature in 3D simulations. The asymmetry arises from the NIF beam geometry and the dependence of laser absorption on beam incidence angle, and we also find that there is a north/south skew to the drive asymmetry. This skew is obscured in radiographs that image down the cylinder axis, complicating inferences of instability growth. This has significant implications for targets with off-normal beam pointing such as polar direct-drive ICF, and it may also be important for a more complete understanding of indirect-drive systems. In particular, differences between experimental data and synthetic data generated from 2D simulations can be misattributed to deficiencies in physics models rather than 3D effects. A similar but more subtle 3D effect is also identified for smaller-scale cylindrical implosion experiments fielded at the OMEGA laser facility, and this is confirmed in recent experiments.
Host: Prof. Carl Sovinec
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Tuesday, March 19th, 2024

Preliminary Exam
Electron Cyclotron Heating in the WHAM device
Time: 2:00 pm - 4:00 pm
Place: B343 Sterling
Speaker: Jonathan Pizzo, Physics Graduate Student
Abstract: The Wisconsin HTS Axisymmetric Mirror (WHAM) is an experiment that will study the axisymmetric mirror as a candidate for magnetically confined fusion energy. WHAM will use electron cyclotron heating (ECH) for many important functions that are necessary to achieve its physics goals. The ECH system has been designed and built over the past 4 years to reliably deliver up to 500kW of 110 GHz power into the WHAM central cell, with control over power level, polarization, pulse length, and deposition location. When operational, this will give WHAM the highest ECH power density of any plasma device to date. In this presentation I will discuss the design and construction of the ECH system throughout the years, including the gyrotron, waveguide transmission line, launch system, and other components. I will also discuss planned future experiments to be done with ECH on WHAM and the potential to use off-axis ECH heating to improve the MHD stability of an axisymmetric mirror.
Host: Cary Forest
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Wisconsin Quantum Institute
Quantum Coffee Hour
Time: 3:00 pm - 4:00 pm
Place: Rm.5294, Chamberlin Hall
Abstract: Please join us for the WQI Quantum Coffee today at 3PM in the Physics Faculty Lounge (Rm.5294 in Chamberlin Hall). This series, which takes place approximately every other Tuesday, aims to foster a casual and collaborative atmosphere where faculty, post-docs, students, and anyone with an interest in quantum information sciences can come together. There will be coffee and treats.
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Wednesday, March 20th, 2024

R. G. Herb Condensed Matter Seminar
Protecting Qubits from High-energy Impacts
Time: 12:00 pm - 1:00 pm
Place: 5310 Chamberlin Hall
Speaker: Britton Plourde, Syracuse University
Abstract: Superconducting circuits are an attractive system for forming qubits in a quantum computer because of the natural energy gap to excitations in the superconductor. However, experimentally it is observed that superconducting qubits have dissipative excitations above the superconducting ground state, known as quasiparticles, that can be generated in bursts, leading to correlated errors between qubits across an array. Such correlated errors pose a significant challenge for current quantum error correction schemes. Quasiparticle bursts can be produced by a range of energy-deposition sources, including the impact of high-energy particles from background radioactivity. These events result in a significant number of energetic phonons that travel efficiently throughout the substrate and generate quasiparticles when they impinge on the qubits. I will describe experiments measuring correlated phonon-mediated quasiparticle poisoning in multi-qubit chips in the aftermath of high-energy particle impacts, as well as numerical modeling of the phonon and quasiparticle dynamics. In addition, I will discuss strategies for protecting qubits from these poisoning effects for the implementation of future fault-tolerant quantum processors.
Host: Robert McDermott
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Thursday, March 21st, 2024

Astronomy Colloquium
The cosmic journey of the elements, from dust to life
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Lia Corrales, University of Michigan
Abstract: To understand our origins, we must understand the role that interstellar dust plays in delivering heavy elements to planetary systems. This requires an understanding of the chemical composition, sizes and shapes of interstellar dust: astromineralogy. X-ray observations provide the most direct means for astromineralogy through the absorption signatures of dust imprinted in the spectra of bright Galactic X-ray sources. I’ll review the latest results in astromineralogy and our work on connecting interstellar dust with suspected extra-solar grains collected in our own Solar System. I’ll also describe how the recently launched XRISM space mission is poised for major breakthroughs in astromineralogy. Finally, I’ll show how I am adapting this work to study aerosols in exoplanet atmospheres, which have the power to alter planetary climate and habitability. By investigating exoplanet transits at short wavelengths, we are opening new windows on aerosols, atmospheric escape, and the role that stars play in sculpting planets.
Host: Ke Zhang
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Friday, March 22nd, 2024

Physics Department Colloquium
Towards EeV neutrino astronomy with GRAND
Time: 3:30 pm - 6:00 pm
Place: 2241 Chamberlin Hall
Speaker: Kumiko Kotera , Institut d'astrophysique de Paris
Abstract: We are living exciting times: we are now able to probe the most violent events of the Universe with diverse messengers (cosmic rays, neutrinos, photons and gravitational waves). One challenge to complete the multi-messenger picture resides in the highest energies, as no ultra-high energy neutrinos, with energy > 10^17 eV, have been observed yet. This challenge could be undertaken by the GRAND (Giant Radio Array for Neutrino Detection) project. GRAND is a proposal for a large-scale array of self-triggered radio antennas. It stands out today as a unique experiment which plans to reach ambitious sensitivity and sub-degree angular resolution to launch multi-messenger astronomy at ultra-high-energies. A design has been proposed for the GRAND detector, and the instrumentation is being tested and optimized with 3 small-scale prototypes: GRAND@Nançay, GRAND@Auger, and GRANDProto300. Based on these pathfinders, the GRAND Collaboration is starting to explore improved GRAND technical designs for the next large-scale phase of the project. This will consist in two arrays of 10'000 km2 each, in the Northern and Southern hemispheres to be deployed from 2028. In this talk, we will present the status of the GRAND prototypes, the preliminary designs and simulation results for the next stages, and the rich research program that these will enable.
Host: Ke Fang
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Saturday, March 23rd, 2024

Academic Calendar
Spring recess
Abstract: *Note: actual end time may vary.*
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Sunday, March 24th, 2024

Academic Calendar
Spring recess
Abstract: *Note: actual end time may vary.*
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