Correlations in an expanding gas of hard-core bosons

TL;DR

This paper studies how correlations in a one-dimensional gas of hard-core bosons evolve during free expansion, revealing that initial state correlations are preserved due to the system's integrability.

Contribution

It demonstrates that initial correlations in momentum space remain intact during expansion, highlighting the role of integrability in preserving quantum correlations.

Findings

Correlations in momentum space are preserved during expansion.

Broken translational invariance in the initial state encodes in correlations.

Correlations do not relax due to integrability.

Abstract

We consider a longitudinal expansion of a one-dimensional gas of hard-core bosons suddenly released from a trap. We show that the broken translational invariance in the initial state of the system is encoded in correlations between the bosonic occupation numbers in the momentum space. The correlations are protected by the integrability and exhibit no relaxation during the expansion.