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Events During the Week of March 27th through April 3rd, 2022

Monday, March 28th, 2022

Special Talk
"Exoplanet and solar system synergies through novel instrumentation and observations”
Time: 3:30 pm
Place: 4421 Sterling Hall, Coffee and Cookies at 3:30 pm, Talk starts at 3:45 pm
Speaker: Dr. Emily Martin, 51 Pegasi b Fellow, UC Santa Cruz
Abstract: There are now thousands of known exoplanets in our galaxy and yet characterizing them remains a technical challenge. Solar system planets and brown dwarfs can serve as benchmarks for exoplanet observations and they provide high signal-to-noise data that we cannot yet access for exoplanets. My research combines instrumentation development with observations of brown dwarfs and solar system planets to advance our ability to interpret exoplanet atmospheres. In this talk, I will present an overview of the NIRSPEC upgrade for Keck Observatory, which made the instrument more sensitive for observing exoplanet and brown dwarf atmospheres. Then, I will present preliminary work using upgraded NIRSPEC to track time-resolved varying spectral features to create 2D surface maps of cold brown dwarfs. Lastly, I will discuss a new instrument that I designed and built for Lick Observatory, the Planet as Exoplanet Analog Spectrograph (PEAS) that observes solar system planets as if they are point-source exoplanets.

If you are not able to come, please use link below

Host: Professor Christi Tremonti
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Tuesday, March 29th, 2022

Network in Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS) Seminar
Nuclei in Core-Collapse Supernovae
Time: 6:00 pm
Speaker: Shun Furusawa, Kanto Gakuin/iTHEMS
Abstract: Core-collapse supernovae are one of the most fascinating phenomena in astrophysics but the explosion mechanism is not clearly understood yet because of their intricacies. I will give an overview about the role of nuclei and nuclear physics uncertainties in supernovae. I will also discuss key nuclei and their key information to be investigated for further supernova study, and introduce recent progress of the research on Equations of state for astrophysical simulations.
Host: Baha Balantekin
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Wednesday, March 30th, 2022

Physics ∩ ML Seminar
Machine Learning Statistical Gravity from Multi-Region Entanglement Entropy
Time: 11:00 am
Place: Chamberlin 5280 (Zoom link also available for online participants who signed up on our mailing list)
Speaker: Yi-Zhuang You, UC San Diego
Abstract: The Ryu-Takayanagi formula directly connects quantum entanglement and geometry. Yet the assumption of static geometry lead to an exponentially small mutual information between far-separated disjoint regions, which does not hold in many systems such as free fermion conformal field theories. In this talk, I will present a microscopic model by superimposing entanglement features of an ensemble of random tensor networks of different bond dimensions, which can be mapped to a statistical gravity model consisting of a massive scalar field on a fluctuating background geometry. We propose a machine-learning algorithm that recovers the underlying geometry fluctuation from multi-region entanglement entropy data by modeling the bulk geometry distribution via a generative neural network. To demonstrate its effectiveness, we tested the model on a free fermion system and showed mutual information can be mediated effectively by geometric fluctuation. Remarkably, locality emerged from the learned distribution of bulk geometries, pointing to a local statistical gravity theory in the holographic bulk.
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Department Meeting
Closed Department Meeting
Time: 12:15 pm
Place: B343 Sterling Hall
Speaker: Mark Eriksson, Department Chair
pursuant to Section 19.85(1)(c) of the Wisconsin Open Meetings Law Closed to all but tenured faculty
Host: Mark Eriksson
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Thursday, March 31st, 2022

R. G. Herb Condensed Matter Seminar
ML, ray-based framework for tuning quantum dot devices: Two dots and beyond
Time: 10:00 am
Place: 5310 Chamberlin
Speaker: Justyna Zwolak, NIST
Abstract: Arrays of quantum dots (QDs) are one of the many candidate systems to realize qubits--the fundamental building blocks of quantum computers--and provide a platform for quantum computing [1]. However, the current practice of manually tuning QDs is a relatively time-consuming procedure, inherently impractical for scaling up and other applications. Recently, we have proposed an auto-tuning paradigm that combines a machine learning (ML) algorithm with optimization routines to assist experimental efforts in tuning semiconductor QD devices [2,3]. Our approach provides a paradigm for fully-automated experimental initialization through a closed-loop system that does not rely on human intuition and experience.

To address the issue of tuning arrays in higher dimensions, we expand upon our prior work and propose a novel approach in which we "fingerprint" the state space instead of working with full-sized 2D scans of the gate voltage space. Using 1D traces ("rays") measured ("shone") in multiple directions, we train an ML algorithm to recognize the relative position of the features characterizing each state (i.e., to "fingerprint") in order to differentiate between various state configurations. I will report the performance of the ray-based learning when used off-line on experimental scans of a double dot device and compare it with our existing, CNN-based approach [4]. I will also discuss how it extends to higher-dimensional systems. Using rays not only allows us to automate the recognition of states but also to significantly reduce (e.g., by 70 % for the two-dots case) the number of measured points required for tuning.

[1] D. Loss and D. P. DiVincenzo. Phys. Rev. A, 57: 120–126, 1998.
[2] S. S. Kalantre, J. P. Zwolak, S. Ragole, X. Wu, N. M. Zimmerman, M. D. Stewart, Jr., J. M. Taylor. Machine learning techniques for state recognition and auto-tuning in quantum dots. npj Quantum Inf. 5 (6): 1–10 (2019).
[3] J. P. Zwolak, T. McJunkin, S. S. Kalantre, J. P. Dodson, E. R. MacQuarrie, D. E. Savage, M. G. Lagally, S. N. Coppersmith, M. A. Eriksson, J. M. Taylor. Autotuning of Double-Dot Devices In Situ with Machine Learning. Phys. Rev. Applied 13, 034075 (2020).
[4] J. P. Zwolak, T. McJunkin, S. S. Kalantre, S. F. Neyens, E. R. MacQuarrie, M. A. Eriksson, and J. M. Taylor. Ray-Based Framework for State Identification in Quantum Dot Devices. PRX Quantum 2, 020335 (2021).
Host: Mark Eriksson
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Friday, April 1st, 2022

Wisconsin Quantum Institute
HQAN Quantum Research Colloquium
Time: 9:00 am
Place: 4274 Chamberlin
Speaker: Elizabeth Goldschmidt (UIUC), Edgar Solomonik (UIUC)
Abstract: Join us for updates on the latest research from the NSF Quantum Leap Challenge Institute HQAN. Coffee and pastries will be provided.
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Theory Seminar (High Energy/Cosmology)
The Festina Lente Bound
Time: 1:00 pm
Place: Chamberlin 5280
Speaker: Thomas Van Riet, Leuven University
Abstract: The Festina Lente proposal bounds masses of charged particles in terms of the Hubble scale and the Planck scale. This bound is supposed to be a Swampland bound and is required for successful UV completion of an EFT. I will explain how this bound is motivated from semi-classical black hole physics, I briefly sketch how it can constrain both bottom-up phenomenology and string phenomenology.
Host: George Wojcik
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Physics Department Colloquium
Exploring anyons and black holes-like dynamics in flatland
Time: 3:30 pm
Place: 2103 Chamberlin Hall
Speaker: Smitha Vishveshwara, UIUC
Abstract: The world and the Universe we live in are composed of fermions and bosons. The quantum statistics of these particles overwhelmingly governs what we see around us. But one could wonder, can other kinds of quantum particles exist? I will begin this colloquium with an introduction of quantum statistics and the fascinating possible existence of anyons, particles which obey 'fractional' statistics. The quantum Hall system forms a marvelous two-dimensional realm for hosting many rich phenomena, including fractional statistics. I will describe how anyons can emerge in this setting, how they could be detected borrowing from beam-splitter and other principles used to detect bosons and fermions, and how recent landmark experiments did perform such detection. I will also illustrate how the same setting can probe dynamics akin to that found in the astrophysical realm of black holes. Specifically, point-contact geometries can exhibit phenomena parallel to Hawking-Unruh radiation and black hole quasinormal modes associated with ringdowns in gravitational wave detection.
Host: Alex Levchenko
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Saturday, April 2nd, 2022

Wisconsin Quantum Institute
HQAN visit to UChicago
Time: 9:00 am
Place: to indicate interest:
Speaker: various, HQAN
Abstract: There will be a one-day visit to UChicago on Saturday April 2.

This time we have already reserved a large bus for transport so everyone interested will be able to participate. Please share this info with your research group. A google doc sign up sheet is linked to below.

All HQAN researchers are welcome, as well as any research group members who are not directly supported by HQAN but working on related topics. The visit will provide an opportunity to visit research labs and have informal discussions about research topics and projects.

The nominal schedule for Apr 2 is

Nominal schedule on Feb. 5 will be:
9:00 am depart from Chamberlin Hall/ Charter St.
Chartered coach drive to UC.
12 noon arrive UC
12-1 welcome and lunch provided
1-4 lab tours
4-6 informal discussions
6:00 depart in coach for Madison
9:00 arrive back at Chamberlin Hall
Host: HQAN
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