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Global quantum secure communication can be achieved using quantum keydistribution (QKD) with orbiting satellites. Established techniques useattenuated lasers as weak coherent pulse (WCP) sources, with so-calleddecoy-state protocols, to generate the required single-photon-level pulses.While such approaches are elegant, they come at the expense of attainable finalkey due to inherent multi-photon emission, thereby constraining secure keygeneration over the high-loss, noisy channels expected for satellitetransmissions. In this work we improve on this limitation by using truesingle-photon pulses generated from a semiconductor quantum dot (QD) embeddedin a nanowire, possessing low multi-photon emission ($<10^{-6}$) and anextraction system efficiency of -15 dB (or 3.1%). Despite the limitedefficiency, the key generated by the QD source is greater than that generatedby a WCP source under identical repetition rate and link conditionsrepresentative of a satellite pass. We predict that with realistic improvementsof the QD extraction efficiency to -4.0 dB (or 40%), the quantum-dot QKDprotocol outperforms WCP-decoy-state QKD by almost an order of magnitude.Consequently, a QD source could allow generation of a secure key in conditionswhere a WCP source would simply fail, such as in the case of high channellosses. Our demonstration is the first specific use case that shows a clearbenefit for QD-based single-photon sources in secure quantum communication, andhas the potential to enhance the viability and efficiency of satellite-basedQKD networks.

Enhancing secure key rates of satellite QKD using a quantum dot single-photon source