Multimode entanglement in coupled cavity arrays

TL;DR

This paper demonstrates that quantum correlated states and entanglement can be generated in coupled cavity arrays with weak nonlinearity, using interference effects, enabling new quantum simulation and photon source applications.

Contribution

It reveals that significant quantum correlations and entanglement are achievable in driven-dissipative cavity arrays with weak nonlinearity, challenging previous assumptions.

Findings

Quantum correlations arise from interference pathways.

Entanglement persists under realistic dephasing rates.

Continuous-variable entanglement observed in cavity arrays.

Abstract

We study a driven-dissipative array of coupled nonlinear optical resonators by numerically solving the Von Neumann equation for the density matrix. We demonstrate that quantum correlated states of many photons can be generated also in the limit where the nonlinearity is much smaller than the losses, contrarily to common expectations. Quantum correlations in this case arise from interference between different pathways that the system can follow in the Hilbert space to reach its steady state under the effect of coherent driving fields. We characterize in particular two systems: a linear chain of three coupled cavities and an array of eight coupled cavities. We demonstrate the existence of a parameter range where the system emits photons with continuous-variable bipartite and quadripartite entanglement, in the case of the first and the second system respectively. This entanglement is shown to survive realistic rates of pure dephasing and opens a new perspective for the realization of quantum simulators or entangled photon sources without the challenging requirement of strong optical nonlinearities.