High-efficiency single-photon source above the loss-tolerant threshold for efficient linear optical quantum computing

Abstract

Photon loss is the biggest problem for scalable photonic quantum information processing. This issue can be tackled through quantum error correction, provided that the overall photon loss is below a threshold of one-third. However, all reported on-demand and indistinguishable single-photon sources still fall short of this threshold. Here, by using tailor shaped laser pulse excitation on a high-quantum efficiency single quantum dot deterministically coupled to a tunable open microcavity, we simultaneously demonstrate a high-performance source with a low multi-photon error of g(2)(0) = 0.0205(6), photon indistinguishability of 0.9856(13) and overall system efficiency of 0.712(18). This source for the first time reaches the efficiency threshold for scalable photonic quantum computing. With this source, we further demonstrate 1.89(14) dB intensity squeezing, and consecutive 40-photon events with a count rate of 1.67 mHz. By resonant excitation of an InAs quantum dot embedded in a microcavity, a deterministic single-photon source is demonstrated. Single-photon purity of 0.9795(6), photon indistinguishability of 0.9856(13), and an overall end-to-end efficiency of 0.712(18) are simultaneously obtained.