Dual-path source engineering in integrated quantum optics

TL;DR

This paper introduces a novel integrated quantum optical device that efficiently generates high-fidelity two-photon NOON states using a dual-path waveguide system, enhancing quantum state engineering without complex stabilization.

Contribution

It presents a new physical concept and state generation protocol for integrated waveguide systems, enabling efficient two-photon NOON state production without additional overhead.

Findings

Achieved a two-photon NOON state fidelity of 84.2%.

Observed a NOON state interference visibility of 93.3%.

Demonstrated effective state engineering in integrated quantum optics.

Abstract

Quantum optics in combination with integrated optical devices shows great promise for efficient manipulation of single photons. New physical concepts, however, can only be found when these fields truly merge and reciprocally enhance each other. Here we work at the merging point and investigate the physical concept behind a two-coupled-waveguide system with an integrated parametric down-conversion process. We use the eigenmode description of the linear system and the resulting modification in momentum conservation to derive the state generation protocol for this type of device. With this new concept of state engineering, we are able to effectively implement a two-in-one waveguide source that produces the useful two-photon NOON state without extra overhead such as phase stabilization or narrow-band filtering. Experimentally, we benchmark our device by measuring a two-photon NOON state fidelity of $\mathcal{F} = (84.2 \pm 2.6) \%$ and observe the characteristic interferometric pattern directly given by the doubled phase dependence with a visibility of $V_{\mathrm{NOON}} = (93.3 \pm 3.7) \%$.