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Events During the Week of February 4th through February 11th, 2024

Monday, February 5th, 2024

Atomic Physics Seminar
Novel strategies for hardware-efficient quantum processors
Time: 12:00 pm - 1:00 pm
Place: 5310 Chamberlin Hall
Speaker: Harry Levine, AWS Center for Quantum Computing
Abstract: Quantum error correction is an exciting scientific frontier at the interface of many fields including quantum information science, many-body physics, and computer science. The field has developed rapidly in the last several years, with major milestones marking the first glimpses into a future of error-corrected quantum computers. At the same time, these advances have also illuminated the major science and engineering challenges that remain on the road to useful fault-tolerant quantum computers due to large resource overheads and demanding performance and control requirements. In this talk, I will discuss recent progress in strategies to ease the demands of error correction with a focus on two leading quantum information platforms: superconducting circuits and cold atoms. First, I will discuss the paradigm of “erasure qubits” which are qubits for which errors can be flagged in real-time and are consequently easier to correct. In this context, I will discuss recent experiments showing how erasure qubits can be realized using a “dual-rail” encoding in superconducting transmons, offering a way to package standard qubit components into better error correction building blocks. Second, I will discuss the recent, rapid progress in neutral atom quantum computers and highlight how the unique capabilities for efficient and flexible control can ease the path towards scalable operation of error-corrected quantum processors. Finally, I will discuss prospects for next-generation neutral atom systems and applications in quantum error correction and precision measurement.
Host: Thad Walker
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Plasma Physics (Physics/ECE/NE 922) Seminar
Magnetohydrodynamics of tokamak disruptions
Time: 12:00 pm - 1:15 pm
Place: 1227 Engineering Hall
Speaker: Prof. Carl Sovinec, UW-Madison
Abstract: Full-scale operation of the ITER experiment will produce plasma thermal energy and releasable magnetic energy on the order of hundreds of mega-Joules. Unplanned disruptions to these discharges will be capable of causing significant material damage to plasma-facing components and electrically conducting structures. As such, the susceptibility to disruptions poses the greatest challenge for the tokamak as a fusion reactor concept. In this presentation, operational limits and the typical sequence of dynamics during disruptions are reviewed, as is the physics behind localized heat deposition, electromechanical forcing, and runaway electron (RE) generation. Extended-magnetohydrodynamic (MHD) numerical simulations provide insight into the physics of tokamak disruptions. Results computed with the NIMROD code (nimrodteam.org) describe profile relaxation and surface-force densities during asymmetric vertical displacement. Other simulations show the importance of MHD for mitigation with massive gas injection and shattered pellet injection. The confinement of REs and their influence on MHD is also considered.
Host: Prof. Carl Sovinec
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Tuesday, February 6th, 2024

Wisconsin Quantum Institute
Quantum Coffee Hour
Time: 3:00 pm - 4:00 pm
Place: Rm.5294, Chamberlin Hall
Abstract: Please join us for the bi-weekly WQI Quantum Coffee, beginning Tuesday, February 6th, at 3PM in the Physics Faculty Lounge (Rm.5294 in Chamberlin Hall…at least initially). This series 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, February 7th, 2024

Preliminary Exam
Neutral Beam Injection on WHAM
Time: 10:00 am - 12:00 pm
Place: B343 Sterling
Speaker: Kunal Sanwalka, Physics Graduate Student
Abstract: WHAM is an experiment to study the axisymmetric mirror as a candidate plasma confinement scheme for fusion energy. In order to make a fusion plasma in WHAM, a beam of neutral particles at high energy is fired on a cold background plasma which will create a non-thermal population of fast ions. It is these fast ions which will perform the majority of the fusion in WHAM. In this presentation, I will talk about the current status of the neutral beam injector and planned future experimental campaigns. These include studying the fast ion confinement and effects of fast ions on plasma stability via finite larmor radius effects. These will be measured with an array of diagnostics such as the beam shine-thru array, interferometer, fusion proton detector etc.
Host: Cary Forest
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Atomic Physics Seminar
Quantum Science with Ultracold Atoms: from Quantum Simulation to Quantum Networking
Time: 12:00 pm - 1:00 pm
Place: 5310 Chamberlin Hall
Speaker: Elmer Guardado-Sanchez, Harvard University
Abstract: The field of ultracold atoms is undergoing a significant transformation, evolving from primarily Analog quantum simulation to systems featuring comprehensive Digital control over all components. This advancement has enabled full coherent control over hundreds of individual atoms, opening pathways to prepare novel states of matter and positioning these systems as a credible platform for Quantum Information Processing. In this talk, I will present some of the developments in my field, illustrated through my own research. First on the Analog side, I will delve into the exciting science that a Fermionic Quantum Gas Microscope opens up to explore. This programmable quantum simulator gives unprecedented access into the microscopics of condensed matter systems. Then on the Digital side, I will talk about recent work coupling two individual atoms to a high-cooperativity cavity, highlighting how, beyond communication, optical networking nodes can also be used as mediators of entanglement. The talk will conclude with two future research directions, one focusing on a platform for next-generation quantum simulation and a second potential avenue for a scalable quantum internet using a novel atomic species.
Host: Thad Walker
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Thursday, February 8th, 2024

Astronomy Colloquium
X-Ray Spectroscopic Insights Into the Microphysics of Collisionless Shocks
Time: 3:30 pm - 4:30 pm
Place: 4421 Sterling Hall
Speaker: Ehud Behar, Technion
Abstract: The theory of collisionless shocks is well established and explains a multitude of astrophysical phenomena, while their microphysics is extremely difficult to probe with observations.
Narrow radiative recombination continua are the smoking gun of highly ionized species recombining with cold (kT ~ eV) electrons.
They are naturally observed in photo-ionized plasmas of active galaxies and X-Ray binaries, but what are they doing in hot (kT ~ keV) shocked plasmas, such as those observed in colliding wind binaries, supernova remnants, planetary nebulae, and novae?
The talk will present line-resolved X-ray spectra of these sources, the highlight of which will be spectacular XMM-Newton and Chandra X-ray observations of the 2020 nova YZ Ret.
The data provide a unique insight into the microphysics of shocked gases that no other measurement can, delivering unambiguous evidence for hot shocked gas directly mixing with cold electrons and neutral atoms, likely right around the shock front.
Host: Ke Zhang
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Friday, February 9th, 2024

Physics Department Colloquium
Retrieving images from tarnished 19th century daguerreotypes using X-ray fluorescence imaging with an X-ray micro beam with tunable energy
Time: 3:30 pm - 5:00 pm
Place: Chamberlin 2241
Speaker: Tsun-Kong (T.K.) Sham, Western University, Ontario
Abstract: An overview of the recent success of using X ray fluorescence (XRF) imaging excited with a tunable X-ray microbeam from synchrotron light sources for the recovery of damaged and obstructed 19th century daguerreotype will be presented. [1, 2] Daguerreotype is the first commercial photography in human history (early 1800’s) produced on a polished, silver coated copper plate. We show that high quality images can always be retrieved from tarnished plates using Hg L XRF as long as the bulk of the image particles and their distribution remain intact. This technique overcomes the challenges of conventional conservation methods which are often unable to bright the image back to life. We also report results from using tunable tender X-rays (2 - 7 keV) to image in high vacuum at energy above the Ag L-edge and the Hg M-edge, extracting images using Ag L and Hg M, respectively among others (e.g., S to track corrosion). Images obtained with the surface sensitive total electron yield (TEY) and the bulk sensitive fluorescence yield (FLY) as well as corresponding micro-XANES are noted. Flux tolerance to high intensity X-beam is also explored. These results and their implications for cultural heritage and other cultural heritage research and prospects of the technique at fourth generation light sources will be discussed. 1. Kozachuk, M.S.; Sham, T.K.; Martin, R.R.; Nelson, A.J.; Coulthard, I.; McElhone, J.P. Recovery of Degraded-Beyond Recognition 19th Century Daguerreotypes with Rapid High Dynamic Range Elemental X-ray Fluorescence Imaging of Mercury L Emission. Sci. Rep. 2018, 8, 1. 2. Stark, A; Filice, F.; Noël, J.J.; Martin, R.R.; Sham T.K.; Finfrock, Y.Z.; Heald, S.M. Retrieving Tarnished Daguerreotype Content Using X-ray Fluorescence Imaging-Recent Observations on the Effect of Chemical and Electrochemical Cleaning Methods, Herit. Sci. 2021, 4, 1605-1615 *Research conducted at Western University is supported by NSERC, CFI, CRC of Canada and OIT of Ontario and Western University
Host: Uwe Bergmann
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Outreach
Chasing ghost particles: searching for neutrinos from high-energy sources in real time
Time: 7:15 pm - 9:00 pm
Place: Space Place, 2300 S Park St and virtual, see abstract for link
Speaker: Jessie Thwaites, UW–Madison Physics / WIPAC
Abstract: Neutrinos are tiny, nearly massless particles that interact very rarely. Because of this, astrophysical neutrinos can travel very far, all the way to the South Pole, carrying information directly from their sources. The IceCube Neutrino Observatory has detected these astrophysical neutrinos, but only a few sources have been identified thus far. We search for these neutrinos from transient sources – sources that vary in their brightness over time, such as gamma-ray bursts (GRBs), supernovae, novae, or mergers of compact objects. These sources often have very energetic processes happening inside them to accelerate particles and produce these neutrinos. By searching for these transient sources as they’re happening (in real time), we can inform follow-up by other observatories also searching for them, and better understand the nature of some of the highest energy phenomena in our universe.

Jessie Thwaites is a 4th year graduate student in the UW—Madison Physics department, working with Justin Vandenbroucke on the IceCube Neutrino Observatory. Their research focuses on searching for high energy astrophysical sources of neutrinos from transient sources, in both real time and archival data. In addition to research, Jessie writes for Astrobites, a daily science communication blog that summarizes astronomy or astrophysics papers into bite-sized pieces for the public. Outside of physics, Jessie plays horn and enjoys hanging out with their cat, Ryan.

This meeting will take place in-person at our usual Space Place classroom location. It will also be streamed live to our YouTube channel at
Host: Madison Astronomical Society
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Saturday, February 10th, 2024

Wonders of Physics
The Wonders of Physics 41st annual show
Time: 1:00 pm - 2:15 pm
Place: 2103 Chamberlin
Abstract: A fun, fast-paced physics demonstration show for all ages!
Host: Haddie McLean
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Wonders of Physics
The Wonders of Physics 41st annual show
Time: 4:00 pm - 5:15 pm
Place: 2103 Chamberlin
Abstract: A fun, fast-paced physics demonstration show for all ages!
Host: Haddie McLean
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Sunday, February 11th, 2024

Wonders of Physics
The Wonders of Physics 41st annual show
Time: 1:00 pm - 2:15 pm
Place: 2103 Chamberlin
Abstract: A fun, fast-paced physics demonstration show for all ages!
Host: Haddie McLean
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Wonders of Physics
The Wonders of Physics 41st annual show
Time: 4:00 pm - 5:15 pm
Place: 2103 Chamberlin
Abstract: A fun, fast-paced physics demonstration show for all ages!
Host: Haddie McLean
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