Subcarrier wave continuous variable quantum key distribution with discrete modulation: mathematical model and finite-key analysis

TL;DR

This paper introduces a continuous-variable quantum key distribution protocol using multimode coherent states on subcarrier frequencies, with a finite-key security analysis demonstrating feasible secret key distribution over channels with up to 9 dB loss.

Contribution

It presents a novel CV-QKD protocol with subcarrier modulation, a mathematical model, and a finite-key security analysis under realistic conditions.

Findings

Secret key rate lower bound calculated for negligible channel noise

System can distribute keys over channels with up to 9 dB loss

Security analysis performed under collective attack assumption

Abstract

In this paper we report a continuous-variable quantum key distribution protocol using multimode coherent states generated on subcarrier frequencies of the optical spectrum. To detect the quadrature components of bosonic field we propose a coherent detection scheme where power from a carrier wave is used as a local oscillator. We compose a mathematical model of the proposed scheme and perform its security analysis in the finite-size regime using fully quantum asymptotic equipartition property technique. We calculate a lower bound on the secret key rate for the system under the assumption that the quantum channel noise is negligible compared to detector dark counts, and an eavesdropper is restricted to collective attacks. Our calculation shows that the current realistic system implementation would allow distributing secret keys over channels with losses up to 9 dB.