N00N states from a single non-linear directional coupler

TL;DR

This paper proposes a compact, scalable method to generate 2-photon N00N states directly within a single non-linear waveguide coupler, eliminating the need for post-processing, spectral filtering, or phase stabilization.

Contribution

It introduces a novel approach to produce N00N states using a periodically poled waveguide coupler via type-0 parametric down-conversion, simplifying quantum state generation.

Findings

Successful generation of N00N states without post-processing

Elimination of spectral filtering and phase stabilization requirements

Potential for integrated quantum photonic applications

Abstract

In the quest for applicable quantum information technology miniaturised, compact and scalable sources are of paramount importance. Here, we present the concept for the generation of 2-photon N00N states without further post-processing in a single non-linear optical element. Based upon a periodically poled waveguide coupler, we present the principle of state generation via type-0 parametric down-conversion inside this type of devices. With the eigenmode description of the linear optical element, we utilise the delocalised photon pair generation to generate a N00N state in the measurement basis. We show, that we are able to eliminate the need for narrow-band spectral filtering, as well as for phase-stabilisation of the pump light, making this approach an elegant way to produce 2-photon N00N states.