Abstract:

These lectures will survey recent progress in realizing and characterizing nontrivial many-body phases of open quantum systems. In the first lecture I will discuss how to define steady-state phases of open systems [1], and introduce concepts that are distinctive to open systems, such as strong and weak symmetries and spontaneous strong-to-weak symmetry breaking [2]. In the second lecture I will introduce cavity QED as a setting in which phases such as a nonequilibrium quantum spin glass can be realized [3]. Building on this example, in the second and third lectures I will introduce a dual perspective on open quantum systems, focusing on the classical and quantum information that they leak into the environment. As I will discuss, this emitted information can be used to witness steady-state phase transitions [3], and also underlies a new family of "learnability" transitions [4]. 

[1] Rakovszky, SG, von Keyserlingk, Phys. Rev. X 14, 041031 (2024)

[2] Sala, SG, Oshikawa, You, Phys. Rev. B 110, 155150 (2024)

[3] SG, Lev, Goldbart, Phys. Rev. Lett. 107, 277201 (2011); Marsh et al., Phys. Rev. X 14, 011026 (2024); Kroeze et al., arxiv:2311.04216

[4] Barratt et al., Phys. Rev. Lett. 129, 200602 (2022); Agrawal et al., Phys. Rev. X 14, 041012 (2024); SG, J. Phys. A: Math. Theor. 58 055301 (2025).

Prof. Sarang Gopalakrishnan’s Biography:

SG received his PhD from the University of Illinois at Urbana-Champaign in 2012. Since then he has worked as a postdoc at Harvard (2012-2015) and Caltech (2015-2016); and taught at the City University of New York (2016-2020), Penn State University (2021-2022), and Princeton (2022-present). He has worked on various aspects of quantum dynamics in many-body systems, including the phenomena of thermalization and many-body localization, generalized hydrodynamics of integrable systems, and the dynamics of open and monitored quantum systems. 

Participation is open to all ICFOnians.