Entanglement dynamics of a hard-core quantum gas during a Joule expansion

TL;DR

This paper investigates the entanglement evolution of a one-dimensional hard-core quantum gas during a sudden expansion, demonstrating the validity of hydrodynamic predictions over multiple reflections and exploring long-time Floquet dynamics.

Contribution

It provides an analytic description of entanglement dynamics in a quantum gas during expansion and examines the breakdown of hydrodynamics at long times.

Findings

Hydrodynamic predictions match entanglement entropy measurements after multiple reflections.

Analytic formulas accurately describe entanglement dynamics during the expansion.

Hydrodynamics breaks down in the long-time Floquet regime.

Abstract

We study the entanglement dynamics of a one-dimensional hard-core quantum gas initially confined in a box of size $L$ with saturated density $\rho=1$. The gas is suddenly released into a region of size $2L$ by moving one of the box edges. We show that the analytic prediction for the entanglement entropy obtained from quantum fluctuating hydrodynamics holds quantitatively true even after several reflections of the gas against the box edges. We further investigate the long time limit $t/L\gg 1$ where a Floquet picture of the non-equilibrium dynamics emerges and hydrodynamics eventually breaks down.