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

Coherent pair-production processes are enabling mechanisms for quantum entanglement generation in continuous variable states. In this talk, we present an experimental scheme to initiate pair-production of quasiparticles in atomic quantum gases by quenching to an attractive interaction. We characterize non-classical correlation in quasiparticles by quenching the atomic interaction back to repulsive, and by monitoring the in situ density noise power spectrum, which effectively 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, demonstrating coherent quasiparticle generation and evolution. The spectrum is observed to oscillate below a limit set by the Peres-Horodecki separability criterion of continuous-variable states, thereby confirming quantum entanglement between interaction quench-induced quasiparticles.