Abstract

The out-of-equilibrium dynamics of interacting many-body systems presents one of the most challenging problems in modern physics with implications ranging from thermalization dynamics over the formation of order to questions at the heart of quantum complexity and quantum information processing. Traditionally, however, out-of-equilibrium dynamics was mostly confined to short transients, since typical systems would ultimately relax back into well-understood—and rather boring—thermal states. During this thermalization, all quantum information present in the initial state is spread over the whole system and thereby becomes inaccessible. In this talk, I will demonstrate that synthetic many-body systems offer access to intrinsically non-ergodic dynamics, where a quantum non-equilibrium system can beat thermodynamics and never relax to a thermal state. We use ultracold atoms in optical lattices as a very versatile platform to study quantum many-body physics in a clean and well-controlled environment. One example, connected to ‘classical’ integrability, is the sudden expansion of hard-core lattice bosons. The second, more generic example is the experimental realization of Many-Body Localization of interacting fermions, where the presence of disorder creates a non-ergodic state that will, in a closed system, never thermalize, and preserve some local memory of the initial conditions for all times.