Security of discrete-modulated continuous-variable quantum key distribution

Security of discrete-modulated continuous-variable quantum key distribution

Seminar author:Stefan Baeuml

Event date and time:06/08/2023 03:00:pm

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Continuous variable quantum key distribution with discrete modulation has the potential to provide quantum physical security using widely available optical elements and existing telecom infrastructure. While their implementation is significantly 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 has previously been used in the setting of discrete variables, to prove finite-size security against coherent attacks for a discrete-modulated quantum key distribution protocol involving four coherent states and heterodyne detection. To do so, and contrary to previous approaches, we consider a protocol in which all the information is discretised. We first bound its asymptotic rate under a realistic photon number cutoff assumption. This bound is then upgraded into a finite-size security proof using entropy accumulation.