Local emergence of thermal correlations in an isolated quantum many-body system

TL;DR

This paper experimentally investigates how thermal correlations develop and spread locally in a non-equilibrium 1D Bose gas, revealing a light-cone-like propagation leading to a globally relaxed state.

Contribution

It demonstrates the local emergence and propagation of thermal correlations in a quantum many-body system after a quench, highlighting the link between correlation spread and relaxation.

Findings

Thermal correlations emerge locally in a prethermalized state.

Correlations propagate in a light-cone-like manner.

The system reaches a globally relaxed state through local processes.

Abstract

We experimentally demonstrate how thermal properties in an non-equilibrium quantum many- body system emerge locally, spread in space and time, and finally lead to the globally relaxed state. In our experiment, we quench a one-dimensional (1D) Bose gas by coherently splitting it into two parts. By monitoring the phase coherence between the two parts we observe that the thermal correlations of a prethermalized state emerge locally in their final form and propagate through the system in a light-cone-like evolution. Our results underline the close link between the propagation of correlations and relaxation processes in quantum many-body systems.