Special Physics Seminar

New perspectives in the dynamics of quantum systems

Kartiek Agarwal

Princeton University

Conventional wisdom holds that systems of interacting particles reach equilibrium at long enough times. This implies that quantum information encoded in the initial state is eventually lost and the dynamics of the system can be simply described by classical hydrodynamic equations. In this talk, I will present instances where such notions are challenged due to “emergent integrability” and the consequence of this on quantum dynamics.

First, I will discuss the phenomenon of many-body localization whereby sufficiently disordered quantum systems exhibit persistent quantum correlations due to the formation of local integrals of motion. I will review our current understanding of this phase, focussing on the transition from the ergodic phase with classical dynamics to the ergodicity-breaking many-body localized phase. I will present some of the open questions and challenges in this field and how experiments inform them. In a shorter second part, I will discuss how integrability often emerges in clean systems in low dimensions, and at low energies. Lack of thermalization makes cooling such systems harder, which is a matter of practical interest. I will show how an understanding of the symmetries of the emergent integrable theory allows one to develop protocols for the fast preparation of the ground states of such systems.