Emergence of Hydrodynamics from Open Quantum Dynamics

Hydrodynamics provides a remarkably universal description of matter in terms of a few continuous?fields. But how does this continuum description emerge from the dynamics of discrete quantum particles? I will address this question in open quantum systems of bosons with a conserved particle-number symmetry. In mixed states this symmetry can be either strong or weak, and distinct dynamical phases can be characterized by the spontaneous breaking of these symmetries. A strong-to-weak spontaneous symmetry-breaking (SW-SSB) transition can be diagnosed by information-theoretic quantities that are nonlinear in the mixed-state density matrix. Remarkably, a nite-time SW-SSB transition can occur, separating quantum from classical dynamics - after the transition classical hydrodynamics emerges. I will discuss observations of a SW-SSB transition in cold atomic gas experiments.

Speaker: Matthew Fisher, UC Santa Barbara