Optimised Domain-engineered Crystals for Pure Telecom Photon Sources

TL;DR

This paper presents a telecom-wavelength parametric down-conversion photon source using domain engineering, achieving high indistinguishability and efficiency without spectral filtering, advancing quantum communication technologies.

Contribution

It demonstrates a domain-engineered source operating at the limit, producing highly indistinguishable photons with high heralding efficiency at telecom wavelengths.

Findings

Two-photon interference visibility of 98.6% without narrow-band filtering

Net heralding efficiency of 67.5%

Collection efficiencies exceeding 90%

Abstract

The ideal photon-pair source for building up multi-qubit states needs to produce indistinguishable photons with high efficiency. Indistinguishability is crucial for minimising errors in two-photon interference, central to building larger states, while high heralding rates will be needed to overcome unfavourable loss scaling. Domain engineering in parametric down-conversion sources negates the need for lossy spectral filtering allowing one to satisfy these conditions inherently within the source design. Here, we present a telecom-wavelength parametric down-conversion photon source that operates on the achievable limit of domain engineering. We generate photons from independent sources which achieve two-photon interference visibilities of up to $98.6\pm1.1\%$ without narrow-band filtering. As a consequence, we reach net heralding efficiencies of up to $67.5\%$, which corresponds to collection efficiencies exceeding $90\%$.