A symmetrization technique for continuous-variable quantum key distribution

TL;DR

This paper presents a symmetrization method for continuous-variable quantum key distribution that simplifies security analysis and proves Gaussian attacks are optimal under certain conditions, enhancing protocol robustness.

Contribution

Introduces a phase space symmetrization technique that simplifies security proofs and extends security guarantees to non-Gaussian attacks in CV-QKD protocols.

Findings

Symmetrization simplifies security analysis.

Gaussian attacks are proven optimal under certain conditions.

Enhances security proof applicability for protocols with postselection.

Abstract

We introduce a symmetrization technique which can be used as an extra step in some continuous-variable quantum key distribution protocols. By randomizing the data in phase space, one can dramatically simplify the security analysis of the protocols, in particular in the case of collective attacks. The main application of this procedure concerns protocols with postselection, for which security was established only against Gaussian attacks until now. Here, we prove that under some experimentally verifiable conditions, Gaussian attacks are optimal among all collective attacks.