Events at Physics |
Events During the Week of February 12th through February 19th, 2023
Sunday, February 12th, 2023
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 1:00 pm - 2:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 4:00 pm - 5:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.
Monday, February 13th, 2023
- Atomic Physics Seminar
- The geometry of quantum error correction under biased noise
- Time: 11:00 am - 12:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Arpit Dua
- Abstract: Quantum error correction is necessary because physical qubits have much higher error rates per gate operation than are needed for practical tasks. The popular choice is to encode a logical qubit in a large enough planar layout of many physical qubits, called the surface code, to have sufficiently low logical error rates. The optimal logical error rates depend on the statistical mechanics of logical operators. For example, under biased Pauli noise, having more higher-weight logical operator representations with a higher ratio of low-rate Pauli operators is better. Using this idea, I will discuss how, in active error correction, measuring Clifford-rotated Pauli stabilizers of the surface code can enhance code performance: higher error thresholds and lower subthreshold logical error rates, for biased Pauli noise. Using statistical mechanics and percolation theory, I will describe a phase diagram of 50% thresholds for random Clifford-rotated surface codes under pure dephasing noise. Using tensor network numerics, I will show that certain families of these random codes outperform the best-known translation invariant Clifford-rotated surface codes for finitely biased depolarizing noise.
- Host: Thad Walker
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Multiscale Nature of Turbulence in Space Plasmas
- Time: 12:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Yan Yang, University of Delaware
- Abstract: Turbulence enters into space plasmas in many guises. The complexity and variability of the behavior of plasma turbulence are in large part due to the involvement of dynamics at many scales, ranging from macroscopic fluid to sub-electron scales. Based on what plasma properties we are interested in studying, be they dominant at small or large scales, plasma can be treated as tractable models in various limits, such as the kinetic theory and magnetohydrodynamic (MHD) theory. Turbulence flows are characterized by the nonlinear transfer of energy and other quantities across a huge range of scales. Observed turbulence in space is expected to involve cross-scale energy transfer and subsequent dissipation and heating. Space plasmas are frequently taken to be weakly collisional or collisionless. Therefore, an explicit form of viscous dissipation as in collisional (e.g., MHD) cases cannot be easily defined. A variety of approaches have attempted to characterize specific mechanisms (e.g., magnetic reconnection, wave-particle interaction, and turbulent-driven intermittency) and to quantify the dissipation. However, the community has not come to a consensus solution applicable to all systems. In this talk I will first give an overview of some basic properties for turbulence. Then I will briefly review turbulence theory application in space plasmas. I will discuss in detail how to disentangle multiscale properties, how plasma dynamics bridges multiple scales, what new ingredients are introduced in cross-scale transfer as models progress from fluid to kinetic, and how to identify key steps in energy transfer and estimate energy dissipation rate in weakly collisional plasmas. These also motivate several unresolved issues that may be addressed by future studies. Where feasible, examples are given from MHD, Particle in Cell, and hybrid Vlasov-Maxwell simulations, and from Magnetospheric Multiscale (MMS) observations.
Tuesday, February 14th, 2023
- R. G. Herb Condensed Matter Seminar
- Discovering and Engineering Two-Dimensional Magnetism and Superconductivity
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Tiancheng Song, Princeton
- Abstract: Understanding and manipulating macroscopic quantum phenomena such as superconductivity and magnetism are crucial for future quantum science and technology. Two-dimensional (2D) materials and their van der Waals (vdW) heterostructures offer a promising platform to achieve this goal due to their exceptionally broad tunability. In this talk, I will highlight the potential of such a platform through two outstanding examples: 2D magnetism and 2D superconductivity. In the first part, I will talk about a series of emergent phenomena enabled by the vdW nature of 2D magnets, including (1) giant tunneling magnetoresistance enhanced by spin-filtering effects; (2) control of interlayer magnetism by tuning layer stacking; (3) novel moiré magnetism by twisting two layers of 2D magnets. In the second part, I will introduce a new probe to detect superconducting fluctuations down to millikelvin temperatures based on thermoelectric measurements of a monolayer nanoflake. I will discuss surprisingly unusual vortex Nernst signals, which reveal an unconventional superconducting quantum criticality in an electrically tunable 2D superconductor. Finally, I will conclude by highlighting unique opportunities for discovering and engineering new quantum materials and electronic phases in two dimensions.
- Host: Victor Brar
- Council Meeting
- Time: 3:00 pm - 4:00 pm
- Place: 2314 Chamberlin Hall
- Speaker: Mark Eriksson, UW-Madison
- Host: Mark Eriksson
Wednesday, February 15th, 2023
- Atomic Physics Seminar
- Achieving Practical Computations on Quantum Computers: From Better Qubits to Better Algorithms
- Time: 11:00 am - 12:00 pm
- Place: 5310 Chamberlin Hall
- Speaker: Matthew Otten , Hughes Research Laboratories
- Abstract: Quantum information science holds the potential to revolutionize computation, communication, and sensing. Despite recent progress, significant challenges remain to make quantum technology practical and scalable. In this talk, I will highlight my research on simulating open quantum systems, benchmarking quantum devices, and developing efficient quantum algorithms. I will also discuss the physics of different qubits, methods for characterizing and verifying them, and quantum algorithms for chemistry. Finally, I will outline my plans to tackle the remaining challenges and bring practical quantum computing closer to reality.
- Host: Thad Walker
- Department Meeting
- Time: 12:15 pm - 1:15 pm
- Place: B343 Sterling Hall
- Speaker: Mark Eriksson, UW-Madison
- Host: Mark Eriksson
Thursday, February 16th, 2023
- R. G. Herb Condensed Matter Seminar
- Strange Metal Behavior in the Hall Coefficient of BaFe2(As,P)2
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Ian Hayes, University of Maryland
- Abstract: Even after decades of research on the high-Tc cuprates, several parts of their phase diagrams remain mysterious, especially the normal state above Tc near optimal doping, a region commonly referred to as the strange metal phase. New avenues for studying this physics were opened up by the discovery of the iron-based high-Tc materials, which also exhibit strange metal characteristics, particularly a T-linear resistivity and a roughly 1/T Hall coefficient near optimal doping. In this talk I will present measurements of the Hall coefficient in phosphorous-doped BaFe2As2 in fields of up to 65 tesla, which is enough to suppress superconductivity even at optimal doping. These measurements reveal a striking parallel between the effects of increasing magnetic field and the effects of increasing temperature, a phenomenon that is reminiscent of the field-temperature scaling seen in the resistivity of this compound. This characteristic field dependence allows us to clearly identify the extent of strange metal physics in the entire phosphorous-doping phase diagram. Intriguingly, the presence of strange metal behavior in the Hall coefficient is directly related to the presence of the superconductivity across the phase diagram. I will discuss the implications of these observations for different approaches to the strange metal as well as the opportunities they present for future research.
- Host: Victor Brar
- NPAC (Nuclear/Particle/Astro/Cosmo) Forum
- Particle acceleration in astrophysical, magnetized turbulent plasmas
- Time: 2:30 pm - 3:30 pm
- Place: CH4274/Invite Link Invite Link
- Speaker: Martin Lemoine , Institut d’Astrophysique de Paris, CNRS
- Abstract: How magnetized turbulent plasmas can accelerate charged particles to high energies represents a long-standing question with far-reaching implications for high-energy and multi-messenger astrophysics. It indeed goes back to the seminal works of Enrico Fermi (1949, 1954) and nowadays, it is commonly invoked to model the generation of non-thermal particle spectra in a broad variety of astrophysical sites, including extreme, relativistic sources. In particular, it has recently been considered as a possible origin for the high-energy neutrinos seen by Ice Cube in the direction of nearby active galactic nuclei. Our understanding of particle acceleration in turbulent plasmas has known substantial progress in recent years, mostly spurred by large-scale, kinetic numerical simulations. This talk will address those developments and discuss a theoretical picture to describe the physics at play, based on non-resonant interactions between particles and velocity structures. This model, which can be seen as a modern implementation of the original Fermi scenario, appears supported by recent numerical simulations of turbulence in the semi- and fully-relativistic regime. It also brings to light an interesting connection between the properties of intermittency of the turbulence and the spectrum of accelerated particles. I will discuss those features then conclude with some possible applications and extensions.
- Host: Ellen Zweibel
- Physics Majors Fair
- Time: 4:30 pm - 5:30 pm
- Place: University Ave Lobby and Physics Museum
- Speaker: Evan Heintz, Undergraduate Advisor
- Abstract: Learn about the Physics major! We'll have faculty and staff on hand who can help you declare your major in Physics and answer any questions you may have about studying undergraduate Physics at UW-Madison.
- Host: Evan Heintz
Friday, February 17th, 2023
- Academic Calendar
- Deadline for students (except Graduate) to change variable credits
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students (except Graduate) to request pass/fail or credit/audit options for a Spring term course
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Academic Calendar
- Deadline for students to drop a Spring term course and receive 50% tuition adjustment
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Preliminary Exam
- 2D Convolutional Network for IceCube DeepCore Oscillation Studies
- Time: 12:00 pm - 2:00 pm
- Place: 2335 Sterling or
- Speaker: Josh Peterson, Physics Graduate Student
- Abstract: IceCube DeepCore is an extension of the IceCube Neutrino Observatory designed to measure GeV scale atmospheric neutrino interactions. Neutrino reconstruction and classification tasks are especially difficult at GeV scale energies in IceCube DeepCore due to sparse instrumentation. Convolutional neural networks (CNNs) have been found to have better success at neutrino event reconstruction than likelihood-based methods. I present a new CNN model that exploits time and depth translational symmetry in IceCube DeepCore data and present the model’s performance, specifically for neutrino flavor identification. This new CNN model will be used for inelasticity reconstruction and/or matter effect dependent neutrino oscillation studies.
- Host: Kael Hanson
- Physics Department Colloquium
- So a quantum computer walks into the White House…
- Time: 3:25 pm - 6:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Charles Tahan , Laboratory for Physical Sciences
- Abstract: Charle Tahan is Director of the National Quantum Coordination Office (NQCO) within the
White House Office of Science and Technology Policy. Tahan is also
Chief Scientist of the National Security Agency's Laboratory for Physical Sciences.
He got his PhD degree under the supervision of Bob Joynt at UW-Madison.
- Host: Robert Joynt
Saturday, February 18th, 2023
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 1:00 pm - 2:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 4:00 pm - 5:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.
Sunday, February 19th, 2023
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 1:00 pm - 2:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.
- Wonders of Physics
- The Wonders of Physics 40th annual show
- Time: 4:00 pm - 5:15 pm
- Place: 2103 Chamberlin
- Abstract: The Wonders of Physics annual show is a fast-paced, engaging, and educational physics program, filled with demonstrations that help people better understand the physics in the world around them, while having fun at the same time.