Security of discrete-modulated continuous-variable quantum key distribution

Stefan B\"aumlCarlos Pascual Garc\'iaVictoria WrightOmar FawziAntonio Ac\'in

Mar 2023

摘要

Continuous variable quantum key distribution with discrete modulation has thepotential to provide quantum physical security using widely available opticalelements and existing telecom infrastructure. While their implementation issignificantly simpler than that for protocols based on Gaussian modulation,proving their finite-size security against coherent attacks poses a challenge.In this work we apply the entropy accumulation theorem, a tool that haspreviously been used in the setting of discrete variables, to prove finite-sizesecurity against coherent attacks for a discrete-modulated quantum keydistribution protocol involving four coherent states and heterodyne detection.To do so, and contrary to previous approaches, we consider a protocol in whichall the information is discretised. We first bound its asymptotic rate under arealistic photon number cutoff assumption. This bound is then upgraded into afinite-size security proof using entropy accumulation. Our analysis providesnon-trivial key rates for $n=10^{12}$ rounds.

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