A stand-alone fiber-coupled single-photon source

In this work, we present a stand-alone and fiber-coupled quantum-light source. The plug-and-play device is based on an optically driven quantum dot delivering single photons via an optical fiber. The quantum dot is deterministically integrated in a monolithic microlens which is precisely coupled to the core of an optical fiber via active optical alignment and epoxide adhesive bonding. The rigidly coupled fiber-emitter assembly is integrated in a compact Stirling cryocooler with a base temperature of 35 K. We benchmark our practical quantum device via photon auto-correlation measurements revealing $g^{(2)}(0)=0.07 \pm 0.05$ under continuous-wave excitation and we demonstrate triggered non-classical light at a repetition rate of 80 MHz. The long-term stability of our quantum light source is evaluated by endurance tests showing that the fiber-coupled quantum dot emission is stable within 4% over several successive cool-down/warm-up cycles. Additionally, we demonstrate non-classical photon emission for a user-intervention-free 100-hour test run and stable single-photon count rates up to 11.7 kHz with a standard deviation of 4%.