Two-party Quantum Key Agreement with Six-particle Entangled States Against Collective Noise

Abstract

Quantum key agreement (QKA) is an advanced technique that allows multiple parties to share a secret key through cooperation. At present, most QKA protocols have the problems of weak anti-noise ability and low qubit efficiency. In this paper, two improved two-party QKA protocols are proposed using two sets of special logical qubits, which are immune to the collective noise. The main idea of these two protocols is that first, through the measurement correlation of the six-particle entangled states, the communication parties can fairly build a common key. Then, decoy logical qubits and delayed measurement technology are employed to prevent eavesdropping in quantum channels. Security analysis indicates that both protocols are unconditionally secure and capable of resisting internal and external attacks. In addition, compared with existing protocols, both protocols improve the efficiency because they transmit longer qubits.