Non-equilibrium coherence dynamics in one-dimensional Bose gases

TL;DR

This paper experimentally investigates the non-equilibrium coherence dynamics in one-dimensional Bose gases, revealing universal decay behaviors and phase locking phenomena, advancing understanding of quantum many-body dynamics in low-dimensional systems.

Contribution

It provides the first direct experimental observation of coherence dynamics in 1d Bose gases, confirming theoretical predictions of universal decay and phase locking.

Findings

Universal sub-exponential coherence decay in isolated 1d Bose gases

Finite coherence in coupled 1d Bose gases consistent with Bogoliubov theory

Demonstration of phase locking analogous to injection locking in lasers

Abstract

Low-dimensional systems are beautiful examples of many-body quantum physics. For one-dimensional systems the Luttinger liquid approach provides insight into universal properties. Much is known of the equilibrium state, both in the weakly and strongly interacting regime. However, it remains a challenge to probe the dynamics by which this equilibrium state is reached. Here we present a direct experimental study of the coherence dynamics in both isolated and coupled degenerate 1d Bose gases. Dynamic splitting is used to create two 1d systems in a phase coherent state. The time evolution of the coherence is revealed in local phase shifts of the subsequently observed interference patterns. Completely isolated 1d Bose gases are observed to exhibit a universal sub-exponential coherence decay in excellent agreement with recent predictions by Burkov et al. [Phys. Rev. Lett. 98, 200404 (2007)]. For two coupled 1d Bose gases the coherence factor is observed to approach a non-zero equilibrium value as predicted by a Bogoliubov approach. This coupled-system decay to finite coherence is the matter wave equivalent of phase locking two lasers by injection. The non-equilibrium dynamics of superfluids plays an important role in a wide range of physical systems, such as superconductors, quantum-Hall systems, superfluid Helium, and spin systems. Our experiments studying coherence dynamics show that 1d Bose gases are ideally suited for investigating this class of phenomena.