Events at Physics |
Events During the Week of April 30th through May 7th, 2023
Monday, May 1st, 2023
- Graduate Program Event
- PhD Final Defense
- Nanoscale Enhancement of Dipole Emission: Modeling Multi-Photon Effects and Microwave Emission from Small Josephson Junctions
- Time: 10:00 am - 12:00 pm
- Place: 4274 Chamberlin
- Speaker: Colin Whisler, Physics Graduate Student
- Abstract: The classical electric dipole acts as a source of electromagnetic radiation, and the power emitted can be modified significantly by optimizing the emitter's environment. This topic has numerous applications, as the electric dipole serves as an excellent representation for processes such as fluorescence from an atomic emitter in an excited state or radiation from a Josephson junction in the AC Josephson effect. Finite difference time domain (FDTD) simulations can provide powerful tools for analyzing these phenomena in arbitrary geometries. This dissertation first calculates the enhancement of two-photon spontaneous emission (2PSE) from trivalent and divalent rare earth ions in proximity to graphene and graphene nanoribbons for achievable experimental conditions using a combination of FDTD simulations and direct computation of transition rates between energy levels in rare earths. The second portion of the dissertation considers the enhancement of dipole emission in a nanoscale gap between an atomically sharp conducting tip and a metallic surface. This serves as a model for Josephson junction spectroscopy, in which the tunneling of Cooper pairs releases local microwaves at bias-dependent frequencies that can be absorbed by nearby molecules, causing DC current to flow. Our results suggest intriguing possibilities for new applications in quantum technology while also discussing the challenges that still must be overcome.
- Host: Victor Brar
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Initial Results from the DIII-D Negative Triangularity Campaign
- Time: 12:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Kathreen Thome, General Atomics
- Abstract: Negative Triangularity (NT) is a potentially transformative scenario for fusion energy with its high-performance core, L-mode-like edge, and low-field-side divertors that could readily scale to an integrated reactor solution free of ELMs. Benefits of the NT shape were originally demonstrated on the TCV tokamak and high-performance has been previously achieved on DIII-D, which motivated the installation of graphite-tile armor on the low-field-side lower outer wall to attain high-power diverted plasmas with strong negative triangularity. In early 2023, a dedicated multiple-week experimental campaign was conducted to qualify the NT scenario for future reactors. During this campaign, high confinement (H98y,2≥1), high current (q95<3), and high normalized pressure plasmas (βN~3) were achieved at high-injected-power in strongly NT-shaped plasmas with δavg= - 0.5 and a lower outer divertor X-point during a dedicated experimental campaign on DIII-D that also demonstrated high normalized density (ne/nGW≤2) and a detached divertor, all while maintaining a non-ELMing NT-edge. Further results on performance, stability, transport, and core-edge integration will be presented.
Tuesday, May 2nd, 2023
- Preliminary Exam
- Search for dark matter produced in association with Higgs boson decaying to bottom quark pair
- Time: 10:00 am - 12:00 pm
- Place: 5310 Chamberlin
- Speaker: Shivani Lomte, Physics Graduate Student
- Graduate Program Event
- Can X-rays Trace the Origins of Printing?
- Time: 2:30 pm - 3:30 pm
- Place: Auditorium of Genetics/Biotech
- Speaker: Minhal Gardezi, Dept of Physics
- Abstract: Minhal's WN@TL presentation is being re-recorded for PBS Wisconsin's University Place! In addition to learning about her cool work, you can help fill the audience to make it look like her talk was as popular as it really was (which it was! just a few months ago).
Abstract:
With the advent of the Gutenberg printing press in the mid 15th century came a boom in literacy, revolutionizing the way Europeans standardized and disseminated information, and establishing the printing press as one of humanity’s most important inventions. While multiple original Gutenberg Bibles have been preserved to the present day, surprisingly little is known about the actual press itself, leaving several unanswered questions about the origins of printing.
However, Gutenberg’s press is only a fraction of the story of early human print. While the first Gutenberg Bibles were being print, thousands of miles away, Korean artisans were building upon hundreds of years of diverse printing experience. The earliest known preserved document printed on a moveable type printing press is a Korean Buddhist text called Jikji, printed in 1377, nearly 80 years before Gutenberg’s Bibles. A wealth of documents proceeding Jikji remain preserved, and their study is critical to understanding early human print.
The questions remain: How were early Eastern and Western printing presses constructed? And how, if at all, were they connected? Here we bring a physicist’s perspective to the investigation. We use synchrotron-generated X-rays to study the makeup of early printed pages from both regions, including leaves of an original Gutenberg Bible and a Korean Confucius text. Collaborating with a large team of scholars from around the globe, we seek to shed new light (literally) on the origins of print. - Host: WN@TL
- Council Meeting
- Time: 3:00 pm - 4:00 pm
- Place: 2314 Chamberlin Hall
- Speaker: Mark Eriksson, UW-Madison
- Host: Mark Eriksson
Wednesday, May 3rd, 2023
- Preliminary Exam
- Multi-Messenger Searches for High Energy Cosmic Ray Accelerators
- Time: 11:00 am - 1:00 am
- Place: 4274 Chamberlin
- Speaker: David Guevel, Physics Graduate Student
- Abstract: The sources of the highest energy cosmic rays are unknown. Within the Milky Way, cosmic rays, which are high energy protons and nuclei, are accelerated to a few PeV by accelerators which have yet to be identified. Even higher energy cosmic rays are thought to be accelerated by distant active galaxies. In both cases, cosmic rays themselves cannot be directly traced back to their sources because they are deflected by the magnetic fields they traverse. Multi-messenger observations can reveal the origin of the cosmic rays through the underlying physics that connects cosmic rays, gamma-rays, and neutrinos. I will present two ongoing works: (1) X-ray observations by Swift-XRT of the Cygnus Cocoon, a gamma-ray source which has been identified as a likely PeV cosmic ray source within the Milky Way, can be used to rule out alternative models of gamma-ray emission thus providing evidence the cosmic ray acceleration model. (2) IceCube neutrinos are an indicator of high energy cosmic ray production. A cross correlation of IceCube neutrinos with a galaxy catalog can constrain the sources that emit extragalactic cosmic rays.
- Host: Ke Fang
- Theory Seminar (High Energy/Cosmology)
- Building non-vanilla QCD axion models
- Time: 1:00 pm - 2:30 pm
- Place: Chamberlin 5280
- Speaker: Felix Yu, Fermilab
- Abstract: In [1] and [2], my co-authors and I revisit the the field theory of axion model building from two separate perspectives. We first considered [1] the effects of small-size instantons arising from enlarged color gauge groups on the QCD axion mass, reaffirming earlier results that QCD axion masses can be parametrically heavier than vanilla models when the confinement effects of the extended color group symmetry contribute to the Peccei-Quinn (PQ) breaking. Notably, we discuss an improvement of the vanilla chiral Lagrangian that readily incorporates non-vanilla 't Hooft determinantal operators. In [2], we present the "Anarchic Axion" model where a possible soft-breaking of PQ symmetry is included in the scalar potential. Depending on the phase and magnitude of the soft-breaking term, an arbitrarily light QCD axion remains to solve the strong CP problem, albeit at the expense of increasing fine tuning. Besides expanding the axion parameter space beyond the vanilla QCD axion band, we have also discussed the phenomenology of axion-like particle effective field theories when the Standard Model is extended to include a gauged baryon number symmetry, offering new collider signatures for ALPs and Z' bosons [3]. [1] Kivel, Laux, FY, [JHEP 11(2022) 088, arXiv:2207.08740] [2] Elahi, Elor, Kivel, Laux, Najjari, FY [arXiv:2301.08760] [3] Kivel, Laux, FY [JHEP 03 (2023) 078, arXiv:2211.12155]
- Host: George Wojcik
- Astronomy Colloquium
- Building stars, planets and the ingredients for life in space
- Time: 3:30 pm - 4:30 pm
- Place: 4421 Sterling Hall
- Speaker: Ewine F. van Dishoeck, Leiden Observatory, Leiden University, the Netherlands
- Abstract: Thousands of planets have been discovered around stars other than our
Sun. But how and where are these exo-planets born, and why are they so
different from those in our own solar system? Which ingredients are
available to build them? Thanks to powerful new telescopes, including
the James Webb Space Telescope, astronomers can now zoom in to
planetary construction sites and study their composition. Water and a
surprisingly rich variety of organic materials are found near forming
stars, including simple sugars, ethers, alcohols and hydrocarbons.
How are these molecules made under the extreme conditions in space and
can they be delivered to new planets to form the basis for life
elsewhere in the universe? - Host: Ke Zhang
Thursday, May 4th, 2023
- R. G. Herb Condensed Matter Seminar
- SQUID-Based Broadband Microwave Isolator
- Time: 10:00 am - 6:00 pm
- Place: 5310 Chamberlin
- Speaker: Matt Beck, IBM Yorktown Heights
- Abstract: As superconducting quantum processors grow in size and complexity, so must the peripheral hardware required for the control and readout of such processors. One singular piece of hardware common to superconducting quantum processors setups is the microwave isolator. Current microwave isolator technology can be generally understood in the context of timereversal symmetry breaking via the use of ferrite materials. While generally exhibiting wide (> GHz) bandwidths and large (>20 dB) directionality, these ferrite-based devices are physically large with volumes exceeding 15 cm^3. These devices can also introduce uncontrolled magnetic fields at or near the quantum processor resulting in deleterious effects such as frequency shifts, excess flux noise, or flux vortex formation. For quantum processors at scale to achieve quantum advantage, a replacement must be found. In this talk, I will describe work towards the realization of a superconducting broadband microwave isolator utilizing DC-SQUIDs. I will detail how, with appropriate application of microwave flux drives, the non-linear inductance of the SQUIDs allows for power at the signal frequency travelling in the forward direction to be three-wave mixed and back resulting in constructive interference and near unity transmission. I will also show how, in the reverse direction, the same mixing process results in destructive interference and thus suppression of the signal frequency. Data will be presented on a variety of nanofabricated devices. The data show excellent model-hardware correlation where directionality greater than 15 dB at bandwidths approaching 700 MHz with minimal added insertion loss is achieved. Finally, further extensions of the work will be discussed on how to achieve commercial levels of isolation and the realization of a fully superconducting replacement of commercial ferrite isolators.
- Host: Robert McDermott
Friday, May 5th, 2023
- Academic Calendar
- Last class day for spring semester
- Abstract: *Note: actual end time may vary.* URL:
- Academic Calendar
- Deadline for Graduate students to withdraw from the Spring term
- Abstract: *Note: actual end time may vary.* CONTACT: 262-3811, registrar@em.wisc.edu URL:
- Physics Department Colloquium
- Programmable control of indistinguishable particles: from sampling to clocks to qubits
- Time: 3:30 pm - 6:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Adam Kaufman, UC Boulder
- Abstract: Quantum information science seeks to exploit the collective behavior of a large quantum system to enable tasks that are impossible (or less possible!) with classical resources alone. This burgeoning field encompasses a variety of directions, ranging from metrology to computing. While distinguished in objective, all of these directions rely on the preparation and control of many identical particles or qubits. Meeting this need is a defining challenge of the field. There are several promising platforms that are targeting these capabilities, and I will focus on one such platform — optically-trapped neutral atoms. We have been developing a new suite of tools, based on the use of more exotic atomic species, new trapping architectures, and new control methods. I will provide an overview of these developments and a few specific examples of our recent results, which range from the use of bosonic atoms for sampling problems, a new kind of atomic clock, and a different kind of qubit.
- Host: Shimon Kolkowitz
- Physics Student/Alumni Awards Banquet
- Time: 5:30 pm - 8:30 pm
- Place: WID
- Speaker: Mark Eriksson, UW-Madison
- Abstract: Annual Student and Alumni Awards Banquet.
- Host: Mark Eriksson
Saturday, May 6th, 2023
- Academic Calendar
- Study day
- Abstract: *Note: actual end time may vary.* URL:
Sunday, May 7th, 2023
- Academic Calendar
- Final exams
- Abstract: *Note: actual end time may vary.* URL: