Security Proof for Quantum Key Distribution Using Qudit Systems

TL;DR

This paper establishes security bounds for quantum key distribution protocols using high-dimensional qudit systems, showing increased key rates and noise robustness with system dimension, with finite-key effects largely unaffected up to dimension 20.

Contribution

It provides the first security bounds for qudit-based QKD protocols against coherent attacks, highlighting advantages of higher-dimensional systems.

Findings

Secret key rate increases with system dimension.

Robustness to noise improves with higher dimensions.

Finite-key corrections are stable for dimensions up to 20.

Abstract

We provide security bounds against coherent attacks for two families of quantum key distribution protocols that use $d$-dimensional quantum systems. In the asymptotic regime, both the secret key rate for fixed noise and the robustness to noise increase with $d$. The finite-key corrections are found to be almost insensitive to $d\lesssim 20$.