Quantum-dot-based single-photon sources are key assets for quantum information technology, supplying on-demand scalable quantum resources for computing and communication. However, longlasting issues such as limited long-term stability and source brightness have traditionally impeded their adoption in real-world applications. Here, we realize a quantum key distribution field trial using true single photons across an 18-km-long dark fibre, located in the Copenhagen metropolitan area, using an optimized, state-of-the-art, quantum-dot single-photon source frequency-converted to the telecom wavelength. A secret key generation rate of >2 kbits/s realized over a 9.6 dB channel loss is achieved with a polarization-encoded BB84 scheme, showing remarkable stability for more than 24 hours of continuous operation. Our results highlight the maturity of deterministic single-photon source technology while paving the way for advanced single-photon-based communication protocols, including fully device-independent quantum key distribution, towards the goal of a quantum internet.
@article{arxiv.2301.09399,
title = {Quantum Key Distribution using Deterministic Single-Photon Sources over a Field-Installed Fibre Link},
author = {Mujtaba Zahidy and Mikkel T. Mikkelsen and Ronny Müller and Beatrice Da Lio and Martin Krehbiel and Ying Wang and Nikolai Bart and Andreas D. Wieck and Arne Ludwig and Michael Galili and Søren Forchhammer and Peter Lodahl and Leif K. Oxenløwe and Davide Bacco and Leonardo Midolo},
journal= {arXiv preprint arXiv:2301.09399},
year = {2023}
}