Security of quantum key distribution with bit and basis dependent detector flaws

TL;DR

This paper analyzes the security of the BB84 quantum key distribution protocol considering detector flaws that depend on bits and bases, providing a security proof against sophisticated attacks in realistic imperfect systems.

Contribution

It introduces a powerful attack model for systems with detector efficiency mismatch and offers a security proof applicable to basis-dependent, lossy optical imperfections without relying on the squashing detector model.

Findings

Identified vulnerabilities due to detector efficiency mismatch.

Proposed an attack applicable even with random detector assignment.

Provided a security proof for basis-dependent imperfections.

Abstract

We consider the security of the Bennett-Brassard 1984 (BB84) protocol for Quantum Key Distribution (QKD), in the presence of bit and basis dependent detector flaws. We suggest a powerful attack that can be used in systems with detector efficiency mismatch, even if the detector assignments are chosen randomly by Bob. A security proof is provided, valid for any basis dependent, possibly lossy, linear optical imperfections in the channel/receiver/detectors. The proof does not assume the so-called squashing detector model.