Quantum simulation of expanding space-time with tunnel-coupled condensates

TL;DR

This paper proposes using tunnel-coupled cold atom condensates to simulate the quantum dynamics of an expanding universe, leveraging the sine-Gordon model to study quantum fluctuations and breather formation.

Contribution

It introduces a novel quantum simulation approach for expanding space-time using coupled condensates and analyzes observable phenomena like fluctuation freezing and breather formation.

Findings

Quantum fluctuations freeze during accelerated expansion.

Sine-Gordon breathers can form from quantum fluctuations.

Experimental protocols for observing these phenomena are discussed.

Abstract

We consider two weakly interacting quasi-1D condensates of cold bosonic atoms. It turns out that a time-dependent variation of the tunnel-coupling between those condensates is equivalent with the spatial expansion of a one-dimensional toy-Universe with regard to the dynamics of the relative phase field. The dynamics of this field is governed by the quantum sine-Gordon equation. Thus, this analogy could be used to 'quantum simulate' the dynamics of a scalar, interacting quantum field on an expanding background. We discuss, how to observe the freezing out of quantum fluctuations during an accelerating expansion in a possible experiment. We also discuss an experimental protocol to study the formation of sine-Gordon breathers in the relative phase field out of quantum fluctuations.