Relation between information and disturbance in quantum key distribution protocol with classical Alice

TL;DR

This paper analyzes a semi-quantum key distribution protocol, deriving a trade-off inequality that limits eavesdropper information based on disturbance, ensuring security with minimal quantum requirements for Alice.

Contribution

It introduces a new trade-off inequality for semi-quantum protocols, linking Eve's information gain to disturbance observed, enhancing understanding of security in semi-quantum key distribution.

Findings

Eve's information gain is limited by disturbance levels.

The protocol guarantees security with minimal quantum capabilities for Alice.

A quantitative trade-off inequality is established.

Abstract

The "semiquantum" key distribution protocol introduced by Zou et al. [Phys. Rev. A Vol.79, 052312 (2009)] is examined. The protocol while using two-way quantum communication requires only Bob to be fully quantum. We derive a trade-off inequality between information gained by Eve and the disturbance observed by legitimate users. It guarantees that Eve cannot obtain large information if the disturbance is sufficiently small.