Single-emitter quantum key distribution over 175 km of fiber with optimised finite key rates
Christopher L. Morrison, Roberto G. Pousa, Francesco Graffitti, Zhe Xian Koong, Peter Barrow, Nick Stoltz, Dirk Bouwmeester, John R. Jeffers, Daniel K. L. Oi, Brian D. Gerardot, Alessandro Fedrizzi · arXiv (Cornell University) · 2022
Quantum key distribution with solid-state single-photon emitters is gaining traction due to their rapidly improving performance and compatibility with future quantum network architectures. In this work, we perform fibre-based quantum key distribution with a quantum dot frequency-converted to telecom wavelength, achieving count rates of 1.6 MHz with $g^{\left(2\right)}\left(0\right) = 3.6 \%$. We demonstrate positive key rates up to 175 km in the asymptotic regime. We then show that the community standard analysis for non-decoy state QKD drastically overestimates the acquisition time required to generate secure finite keys. Our improved analysis using the multiplicative Chernoff bound reduces the required number of received signals by a factor of $10^8$ over existing work, with the finite key rate approaching the asymptotic limit at all achievable distances for acquisition times of one hour. Over a practical distance of 100 km we achieve a finite key rate of 13 kbps after one minute of integration time. This result represents major progress towards the feasibility of long-distance single-emitter QKD networks.