A key obstacle to the experimental realization of many photonic quantum-enhanced technologies is the lack of low-loss sources of single photons in pure quantum states. We demonstrate a promising solution: generation of heralded single photons in a silica photonic chip by spontaneous four-wave mixing. A heralding efficiency of 40%, corresponding to a preparation efficiency of 80% accounting for detector performance, is achieved due to efficient coupling of the low-loss source to optical fibers. A single photon purity of 0.86 is measured from the source number statistics without filtering, and confirmed by direct measurement of the joint spectral intensity. We calculate that similar high-heralded-purity output can be obtained from visible to telecom spectral regions using this approach. On-chip silica sources can have immediate application in a wide range of single-photon quantum optics applications which employ silica photonics.
@article{arxiv.1304.7781,
title = {On-chip low loss heralded source of pure single photons},
author = {Justin B. Spring and Patrick S. Salter and Benjamin J. Metcalf and Peter C. Humphreys and Merritt Moore and Nicholas Thomas-Peter and Marco Barbieri and Xian-Min Jin and Nathan K. Langford and W. Steven Kolthammer and Martin J. Booth and Ian A. Walmsley},
journal= {arXiv preprint arXiv:1304.7781},
year = {2013}
}