Telecom Single-Photon Source Enables 227 km Quantum Encryption

Researchers at Heriot-Watt University and the University of Strathclyde have demonstrated positive secret key rates in a quantum key distribution (QKD) scheme over 227 kilometers of optical fiber. The team implemented a “decoy-state” protocol using a telecom C-band single-emitter source, achieving a loss tolerance one order of magnitude greater than traditional, non-decoy schemes. This work broadens the scope of single-photon sources for future quantum networks by enabling long-distance QKD with realistic levels of single-photon purity, moving beyond the limits of current attenuated laser technology. This distance represents a substantial advance for QKD, exceeding the performance of many non-decoy schemes and pushing the boundaries of practical quantum communication networks. Researchers at the Institute of Photonics and Quantum Sciences, Heriot-Watt University, and the SUPA Department of Physics, University of Strathclyde, detailed their findings in a recent publication, focusing on a “decoy-state” protocol to enhance security and range. The core of this advancement lies in the utilization of a frequency-converted telecom single-emitter source. Unlike traditional…