Unconditional Security of Single-Photon Differential Phase Shift Quantum Key Distribution

TL;DR

This paper proves the unconditional security of the single-photon differential phase shift quantum key distribution protocol by relating it to an entanglement-based protocol, establishing security up to a 4.12% error rate.

Contribution

It provides the first unconditional security proof for single-photon DPS-QKD, linking it to an entanglement-based framework and estimating phase error bounds.

Findings

DPS-QKD can generate secure keys with up to 4.12% bit error rate.

The security proof is based on converting DPS-QKD to an entanglement-based protocol.

This work advances the theoretical foundation of quantum key distribution security.

Abstract

In this Letter, we prove the unconditional security of single-photon differential phase shift quantum key distribution (DPS-QKD) protocol, based on the conversion to an equivalent entanglement-based protocol. We estimate the upper bound of the phase error rate from the bit error rate, and show that DPS-QKD can generate unconditionally secure key when the bit error rate is not greater than 4.12%. This proof is the first step to the unconditional security proof of coherent state DPS-QKD.