Continuous-variable entanglement of two bright coherent states that never interacted

TL;DR

This paper demonstrates how a nonlinear waveguide system can generate continuous-variable entanglement between bright coherent states without direct interaction, offering a practical source for quantum information processing.

Contribution

It introduces a novel scheme using coupled nonlinear waveguides to produce entanglement between non-interacting bright pump modes in a traveling-wave setup.

Findings

Entangles non-interacting bright pump modes via a cascade effect.

Produces two-colour quadripartite entanglement with proper parameters.

Operates with broad-spectrum quantum light in a feasible setup.

Abstract

We study continuous-variable entanglement of bright quantum states in a pair of evanescently coupled nonlinear $\chi^{(2)}$ waveguides operating in the regime of degenerate down-conversion. We consider the case where only the energy of the nonlinearly generated fields is exchanged between the waveguides while the pump fields stay independently guided in each original waveguide. We show that this device, when operated in the depletion regime, entangles the two non-interacting bright pump modes due to a nonlinear cascade effect. It is also shown that two-colour quadripartite entanglement can be produced when certain system parameters are appropriately set. This device works in the traveling-wave configuration, such that the generated quantum light shows a broad spectrum. The proposed device can be easily realized with current technology and therefore stands as a good candidate for a source of bipartite or multipartite entangled states for the emerging field of optical continuous-variable quantum information processing.