# Quantum many-body systems out of equilibrium

Closed quantum many-body systems out of equilibrium pose several long-standing problems in physics. Recent years have seen a tremendous progress in approaching these questions, not least due to experiments with cold atoms and trapped ions in instances of quantum simulations. We work on various topics related to the dynamical equilibration and thermalisation of closed quantum many-body systems out of equilibrium due to quenches and ramps, as well as on notions of transport, many-body localisation, and universality near phase transitions.

Research in the group is two-pronged: On the one hand, we are aiming for a rigorous understanding of out-of-equilibrium properties of quantum many-body systems from the perspective of mathematical physics. On the other, we closely collaborate with leading experimentalists performing experiments with ultra-cold atoms in optical lattices or on top of atom chips, constituting sophisticatedly controlled quantum simulators for the research questions at hand.

**Selected group publications**

- Decay and recurrence of non-Gaussian correlations in a quantum many-body system

Nature Physics 17, 559 (2021) - Dynamical structure factors of dynamical quantum simulators

PNAS 117, 26123-26134 (2020) - Entanglement-ergodic quantum systems equilibrate exponentially well

Physical Review Letters 123, 200604 (2019) - Time evolution of many-body localized systems in two spatial dimensions

Physical Review B 102, 235132 (2020) - Emergence of coherence and the dynamics of quantum phase transitions

PNAS 112, 3641 (2015) - Equilibration via Gaussification in fermionic lattice systems

Physical Review Letters 117, 190602 (2016) - Probing the relaxation towards equilibrium in an isolated strongly correlated 1D Bose gas

Nature Physics 8, 325 (2012) - Towards experimental quantum field tomography with ultracold atoms

Nature Communications 6, 7663 (2015) - Many-body localisation implies that eigenvectors are matrix-product states

Physical Review Letters 114, 170505 (2015) - Thermalization in nature and on a quantum computer

Physical Review Letters 108, 080402 (2012) - Absence of thermalization in non-integrable systems

Physical Review Letters 106, 040401 (2011) - Exact relaxation in a class of non-equilibrium quantum lattice systems

Physical Review Letters 100, 030602 (2008) - Exploring local quantum many-body relaxation by atoms in optical superlattices

Physical Review Letters 101, 063001 (2008) - A quantum central limit theorem for non-equilibrium systems: Exact local relaxation of correlated states

New Journal of Physics 12, 055020 (2010)

**Group reviews **

- Quantum many-body systems out of equilibrium

Nature Physics 11, 124 (2015) - Equilibration, thermalisation, and the emergence of statistical mechanics in closed quantum systems

Reports of Progress in Physics 79, 056001 (2016)