Relaxation and Pre-thermalization in an Isolated Quantum System

TL;DR

This study uses full quantum distribution measurements to explore relaxation and pre-thermalization in a 1D Bose gas, revealing a thermal-like steady state characterized by an effective temperature independent of initial conditions.

Contribution

It introduces a novel experimental approach to characterize transient states in quantum systems and demonstrates the emergence of a pre-thermalized state described by a generalized Gibbs ensemble.

Findings

Observation of rapid evolution towards a thermal-like steady state.

Identification of an effective temperature independent of initial conditions.

Evidence supporting pre-thermalization and generalized Gibbs ensemble description.

Abstract

Understanding relaxation processes is an important unsolved problem in many areas of physics. A key challenge in studying such non-equilibrium dynamics is the scarcity of experimental tools for characterizing their complex transient states. We employ measurements of full quantum mechanical probability distributions of matter-wave interference to study the relaxation dynamics of a coherently split one-dimensional Bose gas and obtain unprecedented information about the dynamical states of the system. Following an initial rapid evolution, the full distributions reveal the approach towards a thermal-like steady state characterized by an effective temperature that is independent from the initial equilibrium temperature of the system before the splitting process. We conjecture that this state can be described through a generalized Gibbs ensemble and associate it with pre-thermalization.