$\mathcal{PT}$-Symmetric Quantum State Discrimination for Attack on BB84 Quantum Key Distribution

TL;DR

This paper demonstrates that $ ext{PT}$-symmetric quantum mechanics can be exploited to enhance quantum state discrimination, posing a new threat to the security of the BB84 quantum key distribution protocol.

Contribution

It introduces a novel attack method on BB84 using $ ext{PT}$-symmetric quantum mechanics, significantly improving eavesdropping success rates compared to traditional approaches.

Findings

$ ext{PT}$-symmetry accelerates quantum state discrimination.

The attack increases eavesdropping success rate on BB84.

$ ext{PT}$-based attack outperforms Hermitian methods.

Abstract

Quantum Key Distribution or QKD provides symmetric key distribution using the quantum mechanics/channels with new security properties. The security of QKD relies on the difficulty of the quantum state discrimination problem. We discover that the recent developments in $\mathcal{PT}$ symmetry can be used to expedite the quantum state discrimination problem and therefore to attack the BB84 QKD scheme. We analyze the security of the BB84 scheme and show that the attack significantly increases the eavesdropping success rate over the previous Hermitian quantum state discrimination approach. We design and analyze the approaches to attack BB84 QKD protocol exploiting an extra degree of freedom provided by the $\mathcal{PT}$-symmetric quantum mechanics.