Talks

Driven by rapid advancements in quantum simulation capabilities across diverse physical platforms, open quantum systems are now of great interest, with special focus on thermalization processes of interacting many-body systems. Various techniques have been used to study operator spreading, to characterize entanglement dynamics, and even to identify exotic phases enabled by dynamical symmetries.

This talk will present a novel perspective on dynamical quantum systems that is capable of reproducing many previous results under a single intuitive framework and enables new results in symmetry-constrained systems. This is accomplished via a mapping between the dynamics averaged over Brownian random time evolution and the low-energy spectrum of a Lindblad superoperator, which acts as an effective Hamiltonian in a doubled Hilbert space. Doing so, we identify emergent hydrodynamics governing charge transport in open quantum systems with various symmetries, constraints, and ranges of interactions. By explicitly constructing dispersive excited states of this effective Hamiltonian using a single mode approximation, we provide a comprehensive understanding of diffusive, subdiffusive, and superdiffusive relaxation in many-body systems with conserved multipole moments and variable interaction ranges. Our approach further allows us to identify exotic Krylov-space-resolved diffusive relaxation despite the presence of dipole conservation, which we verify numerically. Therefore, we provide a simple, general, and versatile framework to qualitatively understand the dynamics of conserved operators under random unitary time evolution, and by extension, thermalizing quantum systems.

O. Ogunnaike, J. Feldmeier, J.Y. Lee, "Unifying Emergent Hydrodynamics and Lindbladian Low-Energy Spectra across Symmetries, Constraints, and Long-Range Interactions," arXiv:2304.13028 (accepted to PRL)

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The cosmic microwave background is a sensitive probe of early-Universe physics, and yet fundamental constants at recombination can differ from their present-day values due to degeneracies in the standard cosmological model. Such scenarios have been invoked to reconcile discrepant measurements of the present-day expansion rate, but even absent such motivation they raise the intriguing possibility of yet-undiscovered physics coupled directly to Standard Model particles. I will discuss theories in which a new scalar field shifts the electron's mass at early times; viable models are already stringently constrained by measurements of quasar absorption lines, the abundances of light elements, and the universality of free fall. I will show that the remaining parameter space is exactly that which allows not only the primary cosmic microwave background but also low-redshift distances to be consistent with observations. After presenting the results of parameter inference I will discuss additional cosmological and laboratory signatures of the model.

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Zoom link https://pitp.zoom.us/j/99705853481?pwd=MTZRWC9hREkvOXpiZkxCM3UvdnRNQT09

Squeezing has proven to be a powerful tool for suppressing noise in bosonic quantum sensing and communication. However, it is fragile and the resulting quantum advantage is extremely vulnerable to loss and noise. In this seminar, I will first overview the method of formulating loss and noise and thereby characterizing the practical quantum advantages. Then I will present our recent progress on entanglement-assisted protocols using two-mode squeezed-vacuum states, which are robust to loss and noise. I will demonstrate the quantum advantages in three scenarios: dark matter search, absorption spectroscopy, and telecommunication. Notably, we derived the ultimate precision limit of noise sensing and dark matter search. As a result, we found the two-mode squeezed vacuum is the optimal quantum source for dark matter search at the limit of strong squeezing. This optimality extends to entanglement-assisted communication. In each of the presented scenarios, entanglement-assisted protocols yield quantum advantages of orders of magnitude over classical protocols.

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Zoom link https://pitp.zoom.us/j/94873478582?pwd=c1dxNEVtMGx0ZU4vZjRvTU5OakZoUT09

Abstract TBA

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Zoom link https://pitp.zoom.us/j/92901106970?pwd=SEdZajRQYWlrQzJhRnM0WnRpeHVNdz09

W-algebras are a family of vertex algebras obtained as Hamiltonian reductions of affine vertex algebras parametrized by nilpotent orbits. The W-algebras associated with regular nilpotent orbits enjoy the Feigin-Frenkel duality. More recently, Gaiotto and Rap\v{c}\'ak generalize this result to hook-type W-algebras with the triality for vertex algebras at the corner. In this talk, I will present the correspondence of representation categories for the hook-type W-superalgebras and how to gain general W-algebras in type A from hook-type W-algebras. The talk is based on joint works with my collaborators.

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Zoom link https://pitp.zoom.us/j/92163414611?pwd=a1A5NHUrbEpxUUVuS3pEd1VYQk5kdz09