Finite-size security of continuous-variable quantum key distribution with digital signal processing

TL;DR

This paper presents a secure finite-size continuous-variable quantum key distribution protocol using heterodyne measurements, bridging the gap between theoretical security and practical implementation with digital signal processing.

Contribution

It introduces a robust method for fidelity estimation and provides the first finite-key security proof for a binary phase modulated CV QKD protocol.

Findings

Security proof valid in finite-key regime

Protocol robust against general coherent attacks

Advances practical implementation of CV QKD

Abstract

In comparison to conventional discrete-variable (DV) quantum key distribution (QKD), continuous-variable (CV) QKD with homodyne/heterodyne measurements has distinct advantages of lower-cost implementation and affinity to wavelength division multiplexing. On the other hand, its continuous nature makes it harder to accommodate to practical signal processing, which is always discretized, leading to lack of complete security proofs so far. Here we propose a tight and robust method of estimating fidelity of an optical pulse to a coherent state via heterodyne measurements. We then construct a binary phase modulated CV QKD protocol and prove its security in the finite-key-size regime against general coherent attacks, based on proof techniques of DV QKD. Such a complete security proof achieves a significant milestone in exploiting the benefits of CV QKD.