Security of entanglement-based QKD with realistic parametric down-conversion sources

TL;DR

This paper examines the security of entanglement-based quantum key distribution using realistic parametric down-conversion sources, demonstrating that multi-photon emissions do not compromise security and reviewing existing security proofs.

Contribution

It shows that multi-photon emissions from parametric down-conversion sources do not impair the security of entanglement-based QKD, and clarifies the role of source properties in security proofs.

Findings

Multi-photon emissions do not compromise security.

Security proofs are unaffected by source properties.

Entanglement-based QKD remains secure with realistic sources.

Abstract

The paper analyzes security aspects of practical entanglement-based quantum key distribution (QKD), namely, BBM92 or entanglement-based BB84 protocol. Similar to prepare-and-measure QKD protocols, practical implementations of the entanglement-based QKD have to rely upon non-ideal photon sources. A typical solution for entanglement generation is the spontaneous parametric down-conversion. However, this process creates not only single photon pairs, but also quantum states with more than two photons, which potentially may lead to security deterioration. We show that this effect does not impair the security of entanglement-based QKD systems. We also review the available security proofs and show that properties of the entanglement source have nothing to do with security degradation.