Simple and loss-tolerant free-space QKD using a squeezed laser

Abstract

We consider a continuous-variable (CV) quantum key distribution (QKD) protocol over free-space channels, which is simpler and more robust than typical CV QKD protocols. It uses a bright laser, squeezed and modulated in the amplitude quadrature, and self-homodyne detection. We consider a scenario, where the line of sight is classically monitored to detect active eavesdroppers, so that we can assume a passive eavesdropper. Under this assumption, we analyse security of the QKD protocol in the composable finite-size regime. Proper modulation of the squeezed laser to the shot-noise level can completely eliminate information leakage to the eavesdropper and also eliminate the turbulence-induced noise of the channel in the amplitude quadrature. Under these conditions, estimation of the eavesdropper's information is no longer required. The protocol is extremely robust to modulation noise and highly loss-tolerant, which makes it a promising candidate for satellite-based continuous-variable quantum communication.

9 pages, 3 figures. arXiv admin note: text overlap with arXiv:2002.03476

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• Classical-Quantum Dual Encoding for Laser Communications in Space
• No Tradeoff between Coherence and Sub-Poissonianity for Heisenberg-Limited Lasers
• Optimized Laser Models with Heisenberg-Limited Coherence and Sub-Poissonian Beam Photon Statistics