Direct generation of entangled photon pairs in nonlinear optical waveguides

TL;DR

This paper presents a novel method for directly generating entangled photon pairs within optical waveguides using the material's intrinsic nonlinearity, eliminating the need for bulky optical components and enabling more compact quantum devices.

Contribution

The authors introduce a scheme for direct entangled photon pair generation in waveguides via photon down-conversion, avoiding external optical elements and achieving competitive conversion efficiencies.

Findings

Direct generation of entangled photon pairs in waveguides demonstrated.

Achieved conversion efficiencies comparable to existing schemes.

Method enables more compact and efficient quantum optics devices.

Abstract

Entangled photons are pivotal elements in emerging quantum information technologies. While several schemes are available for the production of entangled photons, they typically require the assistance of cumbersome optical elements to couple them to other components involved in logic operations. Here, we introduce a scheme by which entangled photon pairs are directly generated as guided mode states in optical waveguides. The scheme relies on the intrinsic nonlinearity of the waveguide material, circumventing the use of bulky optical components. Specifically, we consider an optical fiber under normal illumination, so that photon down-conversion can take place to waveguide states emitted with opposite momentum into a spectral region populated by only two accessible modes. By additionally configuring the external illumination to interfere different incident directions, we can produce maximally entangled photon-pair states, directly generated as waveguide modes with conversion efficiencies that are competitive with respect to existing macroscopic schemes. These results should find application in the design of more efficient and compact quantum optics devices.