Security of continuous-variable quantum key distribution against general attacks

TL;DR

This paper proves the security of Gaussian continuous-variable quantum key distribution against any attack in finite-size settings by leveraging phase space symmetries to approximate the Hilbert space as finite-dimensional, enabling practical security guarantees.

Contribution

It introduces a novel proof technique using phase space symmetries to establish security in finite-size regimes, improving upon previous methods based on the de Finetti theorem.

Findings

Security proof valid for finite-size implementations

Utilizes phase space symmetries to approximate Hilbert space

Enables practical security guarantees for CV-QKD

Abstract

We prove the security of Gaussian continuous-variable quantum key distribution against arbitrary attacks in the finite-size regime. The novelty of our proof is to consider symmetries of quantum key distribution in phase space in order to show that, to good approximation, the Hilbert space of interest can be considered to be finite-dimensional, thereby allowing for the use of the postselection technique introduced by Christandl, Koenig and Renner (Phys. Rev. Lett. 102, 020504 (2009)). Our result greatly improves on previous work based on the de Finetti theorem which could not provide security for realistic, finite-size, implementations.