Phase-Matching Quantum Cryptographic Conferencing

TL;DR

This paper introduces a new phase-matching quantum cryptographic conferencing protocol that enhances key rates and scalability by combining GHZ state post-selection with twin-field QKD techniques, offering improved security and practicality.

Contribution

It proposes a novel QCC protocol based on weak coherent state interference that is immune to detector attacks and scalable, improving key rates over existing measurement device independent protocols.

Findings

Key rate improved from O(η^N) to O(η^{N-1})

Protocol is immune to detector side-channel attacks

Easily scalable to multiple parties

Abstract

Quantum cryptographic conferencing (QCC) holds promise for distributing information-theoretic secure keys among multiple users over long distance. Limited by the fragility of Greenberger-Horne-Zeilinger (GHZ) state, QCC networks based on directly distributing GHZ states at long distance still face big challenge. Another two potential approaches are measurement device independent QCC and conference key agreement with single-photon interference, which was proposed based on the post-selection of GHZ states and the post-selection of W state, respectively. However, implementations of the former protocol are still heavily constrained by the transmission rate $\eta$ of optical channels and the complexity of the setups for post-selecting GHZ states. Meanwhile, the latter protocol cannot be cast to a measurement device independent prepare-and-measure scheme. Combining the idea of post-selecting GHZ state and recently proposed twin-field quantum key distribution protocols, we report a QCC protocol based on weak coherent state interferences named phase-matching quantum cryptographic conferencing, which is immune to all detector side-channel attacks. The proposed protocol can improve the key generation rate from $\mathrm{O}(\eta^N)$ to $\mathrm{O}(\eta^{N-1})$ compared with the measurement device independent QCC protocols. Meanwhile, it can be easily scaled up to multiple parties due to its simple setup.