Spectrally separable photon-pair generation in dispersion engineered thin-film lithium niobate

TL;DR

This paper demonstrates the engineering of dispersion in thin-film lithium niobate waveguides to generate spectrally separable photon pairs suitable for scalable quantum networks, achieving high spectral purity.

Contribution

It introduces a method to engineer dispersion in thin-film lithium niobate for generating spectrally pure photon pairs, overcoming previous material limitations.

Findings

Heralded-state spectral purity exceeds 94%.

Joint spectral phase-sensitive measurement shows 86% purity.

Suitable for scalable quantum network applications.

Abstract

Existing nonlinear-optic implementations of pure, unfiltered heralded single-photon sources do not offer the scalability required for densely integrated quantum networks. Additionally, lithium niobate has hitherto been unsuitable for such use due to its material dispersion. We engineer the dispersion and the quasi-phasematching conditions of a waveguide in the rapidly emerging thin-film lithium niobate platform to generate spectrally separable photon pairs in the telecommunications band. Such photon pairs can be used as spectrally pure heralded single-photon sources in quantum networks. We estimate a heralded-state spectral purity of ${>}94\%$ based on joint spectral intensity measurements. Further, a joint spectral phase-sensitive measurement of the unheralded time-integrated second-order correlation function yields a heralded-state purity of $(86 \pm 5)\%$.