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Events During the Week of May 11th through May 18th, 2025
Sunday, May 11th, 2025: Academic Calendar; Graduate School Spring 2025: Doctoral degree deadline; Time: 11:55 pm - 12:55 am; Abstract: CONTACT: 262-2433, gsacserv@grad.wisc.edu; Add this event to your calendar
Monday, May 12th, 2025: Academic Calendar; Spring Semester Grading deadline; Abstract: *Note: actual end time may vary.*; Add this event to your calendar; Theory Seminar (High Energy/Cosmology); Axion couplings as UV probes; Time: 1:00 pm - 2:30 pm; Place: Chamberlin 5280; Speaker: Michael Nee, Harvard University; Abstract: The couplings of axions to gauge bosons are highly restricted in Grand Unified Theories and heterotic string models. The topological nature of these couplings allows them to be matched from the UV to the IR, and the ratio of the anomaly with photons and gluons for any axion is fixed by UV physics. This implies that in these theories there is a single axion, the QCD axion, with an anomalous coupling to photons. Other light axion-like particles can couple to photons by mixing through the QCD axion portal and lie to the right of the QCD line in the mass-coupling plane. A discovery of an axion to the left of the QCD line can rule out unified theories and some heterotic models. Axion experiments are therefore probes of unification and string theory. Event recording:; Host: Jakob Moritz; Add this event to your calendar; Preliminary Exam; The Magellanic System: The Clouds and their circumgalactic medium within a cosmological context; Time: 1:00 pm - 3:00 pm; Place: B343 Sterling or; Speaker: Robin Chisholm, Physics PhD student; Abstract: Despite tremendous strides in our understanding of the Magellanic Clouds -the closest and most massive dwarf galaxies to the Milky Way (MW)- many questions, especially regarding their circumgalactic medium (CGM), remain open. We characterize the warm CGM of an isolated dwarf galaxy pair with properties similar to the Magellanic Clouds prior to their infall into a MW-mass halo, in the HESTIA cosmological simulations. The massive dwarf hosts a warm coronal gas envelope with a temperature of T ~ 3 x 10^5 K, consistent with expectations for virialized CGM in dwarf halos. Tidal interactions produce a neutral gas stream that extends over ~ 150 kpc, with an HI mass of ~ 10^8 M⊙, similar to the Magellanic Stream. Furthermore, in the Hestia simulation suite, we find that coronal gas is ubiquitous in all halos with M > 10^11 M⊙, implying that massive dwarfs generically develop extended gaseous envelopes prior to accretion. This result has significant implications for the survival of neutral tidal structures, and suggests that current and future high-ion UV absorption-line observations are indicative of warm coronae surrounding LMC-mass dwarfs, independent of their environment. We conclude by discussing future plans to further our understanding of the Magellanic System by running a suite of isolated simulations to constrain the Small Magellanic Cloud's orbital histories.; Host: Elena D'Onghia; Add this event to your calendar
Tuesday, May 13th, 2025: No events scheduled
Wednesday, May 14th, 2025: Climate & Diversity; Suicide Prevention Workshop: Physics Department; Time: 12:00 pm - 1:30 pm; Place: Sterling B343; Speaker: Wendy Ellis, University Health Services; Abstract: Anyone can experience thoughts of suicide and there is no typical way that a person having thoughts of suicide will present to those around them. Anytime you’re concerned about someone, this should be taken seriously. It’s important to remember that you are one link in someone’s chain of support—be a good link, but know your limits. You may not resolve their concern, but you can help get them to the next link in their chain of support.; Host: Rachel Zizmann; Add this event to your calendar
Thursday, May 15th, 2025: R. G. Herb Condensed Matter Seminar; Superconducting quantum networks (and what to do with them); Time: 10:00 am - 6:00 pm; Place: 5310 Chamberlin; Speaker: Wolfgang Pfaff, UIUC; Abstract: In a quantum network, coherent qubit nodes communicate with each other in an on-demand fashion through photonic links. Such networks may be an interesting path toward scaling highly coherent quantum systems, provided they can be interfaced efficiently with photonic interfaces. In a more fundamental direction, networks provide an intriguing platform for investigating limits for preserving distributed quantum states among weakly-interacting or non-interacting qubits. Current research in our group is aimed at realizing different flavors of microwave quantum networks between superconducting qubits and cavities. Recently, we have implemented high-efficiency interconnects for such networks [1]. In this talk, I will focus on our efforts to use those interconnects for scaling superconducting quantum devices, and to investigate the possibility of stabilizing entanglement in open systems. First, we are interested in networks as a scaling approach for high-coherence platforms. A bottleneck for such platforms is generally the choice of suitable nonlinearity for quantum state creation and detection. I will discuss our plans for combining high-Q cavities with the fluxonium qubit as high-coherence control and communication qubit. As a first step toward that end, we have investigated coupling a fluxonium to a linear storage resonator. We have investigated the nonlinearities in this system and used the fluxonium to create and readout quantum states in the resonator. Our results indicate that the fluxonium may be a promising alternative to the transmon for operating, manipulating, and connecting high-Q cavities. Second, we ask whether it is possible to autonomously stabilize entanglement between effectively non-interacting qubits. To answer this question, we have realized a prototypical cascaded quantum network between separate superconducting qubit devices. Using local drives and nonreciprocal photon propagation, we have implemented a protocol that is predicted to generate driven-dissipative remote entanglement [2]. I will present experimental data that show evidence of entanglement stabilization. Additionally, I will discuss perspectives for extending our setup for high-fidelity entanglement delivery and autonomous distillation [3]. [1] M. Mollenhauer, et al., arXiv:2407.16743. Accepted in Nat. Electron. [2] K. Stannigel, P. Rabl, and P. Zoller, New J. Phys. 14, 063014 (2012). [3] A. Irfan, et al., Phys. Rev. Research 6, 033212 (2024).; Host: Britton Plourde; Add this event to your calendar
Friday, May 16th, 2025: Thesis Defense; Noise characterization for Spin and Charge qubits; Time: 10:00 am - 12:00 pm; Place: 5280 CH; Speaker: Deepak Mallubhotla, Physics PhD student; Abstract: Quantum computing offers substantial advantages over classical computers for certain problems, but a fundamental challenge persists: qubits suffer from environmental noise causing decoherence. To achieve scales required for practical applications, error correction techniques must overcome these noise limitations. Studying various noise types is essential for developing effective mitigation strategies.

This dissertation first analyzes evanescent-wave Johnson noise (EWJN) near small metallic devices. Caused by thermal and quantum charge motion in conductors, this noise creates field fluctuations beyond the conductor's surface. Noise correlations B(x, t) B(x', t') are calculated when device size is smaller than material skin depth, yielding closed-form solutions via multipole expansion.

Next, EWJN is examined near BCS superconductors using a half-space geometry where superconductor dimensions exceed qubit distance. Superconductors generate less noise than normal conductors at temperatures well below critical temperature, for both magnetic and electric fields. A Hebel-Slichter peak with enhanced noise appears just below critical temperature, dependent on qubit orientation.

Finally, this dissertation discusses 1/f charge noise.
It has been hypothesized that this noise is caused by fluctuating two-level systems (TLSs). We show that measurements of noise power spectral density do not fully determine TLS parameters exactly, and present a Bayesian technique of assigning likelihoods to different parameter ranges instead. This allows for partial, statistical information to be extracted, giving predictions of TLS size and density. Two recent measurements are analyzed, giving predictions consistent with both each other and with measurements in the literature obtained through other techniques.; Host: Maxim Vavilov/Bob Joynt; Add this event to your calendar; Theory Seminar (High Energy/Cosmology); Quantum Entanglement Theory and Its Generic Searches at the Colliders; Time: 1:30 pm - 3:00 pm; Place: Sterling B343; Speaker: Tianjun Li, Beijing, Inst. Theor. Phys.; Abstract: We propose a new formalism for quantum entanglement, and study its generic searches at the colliders. For a general quantum system with N particles, we show that the quantum space (the total spin polarization parameter space) is complex projective space, and the classical space (the spin polarization parameter space for classical theory) is the cartesian product of the complex projective spaces. Thus, the quantum entanglement space is the difference of these two spaces. For the ff, AA, Af, fff, and ffA systems, we calculate their discrimants \Delta_i. The corresponding classical spaces are the discrimant locus \Delta=0 for ff system, and intersections of the discriminant loci \Delta_i=0 for AA, Af, fff, and ffA systems in the quantum space. We show that our criterion \Delta\not=0 is equivalent to the original Peres-Horodecki criterion for ff system. At the colliders, we can reconstruct the discriminants from various measurements, and probe the quantum entanglement spaces at exact level. This provides a fundamental approach to test the quantum entanglement. In addition, for the specific approach, we propose a generic method to calculate the quantum range and classical range for the expectation value of any physics observable, and can probe the quantum entanglement spaces which the previous way cannot test for some cases. Furthermore, we define the quantum non-locality tests as the tests for quantum entanglement space via the space-like separated measurements, which can be done at colliders as well. Event recording:; Host: Vernon Barger; Add this event to your calendar
Saturday, May 17th, 2025: No events scheduled
Sunday, May 18th, 2025: Academic Calendar; Faculty contract year ends; Abstract: *Note: actual end time may vary.*; Add this event to your calendar

Events During the Week of May 11th through May 18th, 2025