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Events on Thursday, October 13th, 2022

R. G. Herb Condensed Matter Seminar
Measurement-induced Phase Transitions in the Dynamics of Quantum Entanglement
Time: 11:00 am
Place: 5310 Chamberlin
Speaker: Brian Skinner , Ohio State University
Abstract: When a quantum system evolves under unitary dynamics, as produced by either a Hamiltonian or by a sequence of gates inside a quantum computer, its various component parts tend to become more entangled with each other. Making measurements, on the other hand, tends to reduce this entanglement by collapsing some of the system's degrees of freedom. In this talk I'll consider what happens to the entanglement when a quantum many-body system undergoes both unitary evolution and sporadic measurements. I'll show that the competition between these two effects leads to a new kind of dynamical phase transition, such that when the measurement rate is lower than a critical value the dynamics is "entangling", while a higher-than-critical measurement rate leads to a "disentangling" phase. I will discuss our work demonstrating the existence of this transition, as well as more recent efforts to find exact solutions for its critical properties. I will show how intuition from classical percolation in disordered conductors played a key role in our understanding of the transition.
Host: Alex Levchenko
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Astronomy Colloquium
The Smallest and Faintest Galaxies: Clues to the Nature of Dark Matter and Galaxy Formation
Time: 3:30 pm
Place: 4421 Sterling Hall, Or via zoom
Speaker: Burçin Mutlu-Pakdil, Dartmouth University
Abstract: The smallest and faintest galaxies around the Milky Way are the most ancient, most metal-poor, and most dark-matter-dominated systems known. These extreme objects offer unique access to small scales where the stellar and dark matter content can be studied simultaneously. They hold the promise of major breakthroughs in understanding the nature of dark matter and a more complete picture of galaxy formation. Thus, their discovery and characterization are among the most important goals in the field. In this talk, I will share our ongoing observational efforts to detect these faint systems around the Milky Way and beyond, and upcoming advances in the era of deep and wide imaging instrumentation, with a focus on their implications.
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Wisconsin Quantum Institute
Quantum Nanophotonics Hardware: From Nanofabrication to Quantum Circuit Mapping
Time: 4:00 pm
Place: MS&E Building room 265
Speaker: Marina Radulaski, Department of Electrical and Computer Engineering University of California - Davis
Abstract: Photonic systems are the leading candidates for deterministic quantum sources, quantum repeaters, and other key devices for quantum information processing. Scalability of this technology depends on the stability, homogeneity and coherence properties of quantum emitters. Here, color centers in wide band gap materials offer favorable properties for applications in quantum memories, single-photon sources, quantum sensors, and spin-photon interfaces [1,2]. Silicon carbide, in particular, has been an attractive commercial host of color centers featuring fiber-compatible single photon emission, long spincoherence times and nonlinear optical properties [3]. Integration of color centers with nanophotonic devices has been a challenging task, but significant progress has been made with demonstrations up to 120-fold resonant emission enhancement of emitters embedded in photonic crystal cavities [4]. A novel direction in overcoming the integration challenge has been the development of triangular photonic devices, recently shown to preserve millisecond-scale spin-coherence in silicon carbide defects [5,6]. Triangular photonics has promising applications in quantum networks, integrated quantum circuits, and quantum simulation. Here, open quantum system modeling provides insights into polaritonic physics achievable with realistic device parameters through evaluation of cavity-protection, localization and phase transition effects [7]. Mapping of this dynamic to gate-based quantum circuits opens doors for quantum advantage in understanding cavity quantum electrodynamical (QED) effects using commercial Noisy Intermediate-Scale Quantum (NISQ) hardware [8].
Host: Mikhail Kats
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