Quantum-classical transition of correlations of two coupled cavities

TL;DR

This paper investigates the transition from quantum to classical correlations in coupled cavities with second-harmonic generation, highlighting how quantum entanglement persists beyond classical synchronization.

Contribution

It demonstrates the persistence of quantum correlations in coupled cavities even when classical synchronization is absent, bridging quantum and classical regimes.

Findings

Quantum correlations persist off-resonance.

Classical oscillations synchronize via coupling.

Intermediate regime shows minimal correlations.

Abstract

We study the difference between quantum and classical behavior in a pair of nonidentical cavities with second-harmonic generation. In the classical limit, each cavity has a limit-cycle solution, in which the photon number oscillates periodically in time. Coupling between the cavities leads to synchronization of the oscillations and classical correlations between the cavities. In the quantum limit, there are quantum correlations due to entanglement. The quantum correlations persist even when the cavities are far off resonance with each other, in stark contrast with the classical case. We also find that the quantum and classical limits are connected by an intermediate regime of almost no correlations. Our results can be extended to a wide variety of quantum models.