Phys.org April 2, 2024
Continuous-variable (CV) quantum key distribution (QKD) with coherent states and coherent detection integrates well with existing telecommunication networks. Thus far, long-distance CV-QKD has only been demonstrated using a highly complex scheme where the local oscillator is transmitted, opening security loopholes for eavesdroppers, and limiting potential applications. Researchers in Denmark have demonstrated a long-distance CV-QKD experiment with a locally generated oscillator over a 100-kilometer fiber channel with a total loss of 15.4 decibels. This was done by controlling the phase noise–induced excess noise through a machine learning framework for carrier recovery and optimizing the modulation variance. They implemented the full CV-QKD protocol and demonstrated the generation of keys secure against collective attacks in the finite-size regime. According to the researchers their results mark a substantial milestone for realizing CV quantum access networks with a high loss budget and pave the way for large-scale deployment of secure QKD… read more. Open Access TECHNICAL ARTICLE
Long-distance continuous-variable–quantum key distribution (CV-QKD) system. Credit: SCIENCE ADVANCES, 3 Jan 2024, Vol 10, Issue 1