Applicability of Squeezed-and Coherent-State Continuous-Variable Quantum Key Distribution over Satellite Links

TL;DR

This paper evaluates the feasibility of continuous-variable quantum key distribution using squeezed and coherent states over satellite links, analyzing security, noise, and loss factors for practical implementation.

Contribution

It provides tight security bounds and proposes a segmented pass strategy to enhance robustness, demonstrating the benefits of signal squeezing for satellite quantum communication.

Findings

Security bounds indicate the need for setup stabilization and noise reduction.

Segmenting satellite passes improves robustness against channel noise.

Signal squeezing enhances protocol applicability and resilience.

Abstract

We address the applicability of quantum key distribution with continuous-variable coherent and squeezed states over long-distance satellite-based links, considering low Earth orbits and taking into account strong varying channel attenuation, atmospheric turbulence and finite data ensemble size effects. We obtain tight security bounds on the untrusted excess noise on the channel output, which suggest that substantial efforts aimed at setup stabilization and reduction of noise and loss are required, or the protocols can be realistically implemented over satellite links once either individual or passive collective attacks are assumed. Furthermore, splitting the satellite pass into discrete segments and extracting the key from each rather than from the overall single pass allows one to effectively improve robustness against the untrusted channel noise and establish a secure key under active collective attacks. We show that feasible amounts of optimized signal squeezing can substantially improve the applicability of the protocols allowing for lower system clock rates and aperture sizes and resulting in higher robustness against channel attenuation and noise compared to the coherent-state protocol