Observation of Quantum Equilibration in Dilute Bose Gases

TL;DR

This study experimentally demonstrates quantum equilibration in a dilute Bose gas, observing a non-Gaussian momentum distribution that remains stable for about 40 ms before becoming classical and Gaussian.

Contribution

First experimental observation of quantum equilibration dynamics in a non-integrable Bose-Einstein condensate loaded into an optical lattice.

Findings

Quantum equilibration persists for approximately 40 ms.

Momentum distribution remains non-Gaussian during equilibration.

Transition to classical behavior occurs after the equilibration period.

Abstract

We investigate experimentally the dynamical relaxation of a non-integrable quantum many-body system to its equilibrium state. A Bose-Einstein condensate is loaded into the first excited band of an optical lattice and let to evolve up to a few hundreds of milliseconds. Signs of quantum equilibration are observed. There is a period of time, roughly 40 ms long, during which both the aspect ratio of the cloud and its momentum distribution remain constant. In particular, the momentum distribution has a flat top and is not a Gaussian thermal distribution. After this period, the cloud becomes classical as its momentum distribution becomes Gaussian.