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Q: Fachverband Quantenoptik und Photonik

Q 48: QuanTour IV – Building Blocks

Q 48.7: Vortrag

Donnerstag, 5. März 2026, 12:45–13:00, P 7

Decoy-state quantum key distribution over 227 km with a frequency-converted telecom single-photon source — •Frederik Brooke Barnes¹, Robert Gonzalez-Pousa², Christopher L. Morrison¹, Zhe Xian Koong¹, Joseph Ho¹, Francesco Graffitti¹, John Jeffers², Daniel K. L. Oi², Brian D. Gerardot¹, and Alessandro Fedrizzi¹ — ¹Institute of Photonics and Quantum Sciences, School of Engineering and Physical Sciences, Heriot-Watt Univer- sity, Edinburgh, EH14 4AS, UK — ²SUPA Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK

We implement a decoy-state quantum key distribution scheme using a quantum dot frequency-converted to the telecom C-band. The decoy states are created by varying the optical excitation of the quantum emitter to modulate the photon number distribution. We provide an analysis of our scheme based on existing security proofs, allowing the calculation of secret key rates including finite key effects. This enables us to demonstrate, with a realistic single-photon source, positive secret key rates using our scheme over 227~km of optical fibre, equivalent to an increase in loss tolerance greater than one order of magnitude compared to non-decoy schemes, and within 2dB of the tolerable loss when using a single-photon source with similar brightness but perfect single- photon purity. We provide a short perspective on how our methods could be applied to other quantum communication protocols, such as those compatible with quantum memories, to extend secure transmission distances beyond the repeater-less limit.