Observation of quasiparticle pair-production and quantum entanglement in atomic quantum gases quenched to an attractive interaction

TL;DR

This study demonstrates the creation and evolution of quantum entanglement between quasiparticles in an atomic superfluid following a quench to attractive interactions, confirmed through density noise spectrum analysis.

Contribution

It provides the first experimental observation of quasiparticle pair-production and quantum entanglement in atomic gases quenched to attractive interactions.

Findings

Observation of large amplitude growth in the density noise spectrum

Detection of coherent oscillations indicating quasiparticle evolution

Confirmation of quantum entanglement via the Peres-Horodecki criterion

Abstract

We report observation of quasiparticle pair-production and characterize quantum entanglement created by a modulational instability in an atomic superfluid. By quenching the atomic interaction to attractive and then back to weakly repulsive, we produce correlated quasiparticles and monitor their evolution in a superfluid through evaluating the in situ density noise power spectrum, which essentially measures a 'homodyne' interference between ground state atoms and quasiparticles of opposite momenta. We observe large amplitude growth in the power spectrum and subsequent coherent oscillations in a wide spatial frequency band within our resolution limit, demonstrating coherent quasiparticle generation and evolution. The spectrum is observed to oscillate below a quantum limit set by the Peres-Horodecki separability criterion of continuous-variable states, thereby confirming quantum entanglement between interaction quench-induced quasiparticles.