Experimental Observation of a Generalized Gibbs Ensemble

TL;DR

This paper experimentally demonstrates that a one-dimensional Bose gas relaxes to a state described by a generalized Gibbs ensemble, highlighting the emergence of classical statistical behavior from quantum dynamics.

Contribution

It provides the first experimental verification that a generalized Gibbs ensemble accurately describes the relaxation of an isolated quantum many-body system.

Findings

Degenerate 1D Bose gas relaxes to a generalized ensemble

Correlation functions up to 10th order match predictions

Supports the emergence of classical statistical mechanics from quantum evolution

Abstract

The connection between the non-equilibrium dynamics of isolated quantum many-body systems and statistical mechanics is a fundamental open question. It is generally believed that the unitary quantum evolution of a sufficiently complex system leads to an apparent maximum-entropy state that can be described by thermodynamical ensembles. However, conventional ensembles fail to describe the large class of systems that exhibit non-trivial conserved quantities. Instead, generalized ensembles have been predicted to maximize entropy in these systems. In our experiments we explicitly show that a degenerate one-dimensional Bose gas relaxes to a state that can be described by such a generalized ensemble. This is verified through a detailed study of correlation functions up to 10th order. The applicability of the generalized ensemble description for isolated quantum many-body systems points to a natural emergence of classical statistical properties from the microscopic unitary quantum evolution.