Continuous variable entanglement in a cold-atoms mirrorless optical parametric oscillator

TL;DR

This paper demonstrates quantum entanglement between multiple modes in a cold-atom mirrorless optical parametric oscillator, revealing potential for quantum networks and higher-order entanglement studies.

Contribution

It introduces a new heterodyne technique to observe and quantify entanglement in a cold-atom system operating below threshold, with the generation of four entangled modes.

Findings

Quantum entanglement observed between two pairs of modes.

Successful recovery of the covariance matrix using a new heterodyne method.

Generation of four entangled modes in a cold-atom system.

Abstract

In this work, we explore both the internal and external atomic degrees of freedom to observe quantum entanglement between the modes produced by a mirrorless optical parametric oscillator operating below the oscillation threshold in a sample of free-space cold cesium atoms. Using a new heterodyne technique, we recover the covariance matrix that reveals the quantum entanglement for two different pairs of modes, thus demonstrating the generation of four entangled modes in this system. Applications to quantum networks, and the possibilities of studying higher orders of entanglement are a direct consequence of the present study.