Tunable generation of entangled photons in a nonlinear directional coupler

TL;DR

This paper presents a tunable on-chip quantum light source using a nonlinear directional coupler, enabling dynamic control of entangled photon states for advanced quantum photonic circuits.

Contribution

It introduces a novel, experimentally demonstrated method for on-demand reconfigurable entangled photon generation in a nonlinear directional coupler.

Findings

Spatial photon-pair correlations can be reconfigured by phase tuning.

Generation of robust N00N states demonstrated.

Biphoton steering achieved with tunable parameters.

Abstract

The on-chip integration of quantum light sources has enabled the realization of complex quantum photonic circuits. However, for the practical implementation of such circuits in quantum information applications it is crucial to develop sources delivering entangled quantum photon states with on-demand tunability. Here we propose and experimentally demonstrate the concept of a widely tunable quantum light source based on spontaneous parametric down-conversion in a nonlinear directional coupler. We show that spatial photon-pair correlations and entanglement can be reconfigured on-demand by tuning the phase difference between the pump beams and the phase mismatch inside the structure. We demonstrate the generation of split states, robust N00N states, various intermediate regimes and biphoton steering. This fundamental scheme provides an important advance towards the realization of reconfigurable quantum circuitry.