Triggered telecom C-band single-photon source with high brightness, high indistinguishability and sub-GHz spectral linewidth

TL;DR

This paper reports a telecom C-band single-photon source with high brightness, indistinguishability, and narrow spectral linewidth, suitable for quantum networks and quantum memory applications.

Contribution

It demonstrates the first telecom C-band single-photon source with combined high purity, indistinguishability, and spectral narrowness using a novel excitation scheme.

Findings

Achieved $g^{(2)}(0)$ below 0.03 indicating high purity

Obtained two-photon interference visibility over 0.5

Produced polarized photons at rates up to 1.45 MHz

Abstract

Long-range, terrestrial quantum networks will require high brightness single-photon sources emitting in the telecom C-band for maximum transmission rate. Many applications additionally demand triggered operation with high indistinguishability and narrow spectral linewidth. This would enable the efficient implementation of photonic gate operations and photon storage in quantum memories, as for instance required for a quantum repeater. Especially, semiconductor quantum dots (QDs) have shown these properties in the near-infrared regime. However, the simultaneous demonstration of all these properties in the telecom C-band has been elusive. Here, we present a coherently (incoherently) optically-pumped narrow-band (0.8 GHz) triggered single-photon source in the telecom C-band. The source shows simultaneously high single-photon purity with $g^{(2)}(0) = 0.026$ ($g^{(2)}(0) = 0.014$), high two-photon interference visibility of 0.508 (0.664) and high application-ready rates of 0.75 MHz (1.45 MHz) of polarized photons. The source is based on a QD coupled to a circular Bragg grating cavity combined with spectral filtering. Coherent (incoherent) operation is performed via the novel SUPER scheme (phonon-assisted excitation).