Security of two-way quantum key distribution

TL;DR

This paper establishes a security proof for two-way quantum key distribution protocols against general attacks, demonstrating their potential to outperform traditional one-way protocols using minimal device assumptions.

Contribution

It introduces a security proof framework for two-way QKD protocols based on entropic uncertainty, highlighting their advantages over one-way protocols.

Findings

Security proof against general quantum attacks

Two-way protocols can outperform one-way protocols

Minimal assumptions required for security analysis

Abstract

Quantum key distribution protocols typically make use of a one-way quantum channel to distribute a shared secret string to two distant users. However, protocols exploiting a two-way quantum channel have been proposed as an alternative route to the same goal, with the potential advantage of outperforming one-way protocols. Here we provide a strategy to prove security for two-way quantum key distribution protocols against the most general quantum attack possible by an eavesdropper. We utilize an entropic uncertainty relation, and only a few assumptions need to be made about the devices used in the protocol. We also show that a two-way protocol can outperform comparable one-way protocols.