Three-party quantum key agreement with seven-particle entangled states against collective noise: IBM Qiskit implementation

Quantum key agreement (QKA) constitutes a vital branch of quantum cryptography, referring to the collaborative establishment of a shared key among multiple participants. Among these, the three-party quantum key agreement (TPQKA) represents a specific form of QKA involving only three participants. Quantum states inevitably suffer from noise during transmission through quantum channels, which reduces the efficiency of qubits. To significantly improve the efficiency of qubits and further enhance their reliability in quantum applications, this paper proposes two TPQKA protocols based on seven-particle entangled states to provide protection against collective noise effects. In this paper, IBM Qiskit is employed to present the preparation circuit of the seven-particle entangled state, as well as the quantum circuits under two types of collective noise. In both protocols, the three parties apply a hash function to their own keys. In the particle transmission process, according to the measurement results of the particles, the three parties perform the corresponding unitary operation, and ultimately they equally negotiate the final shared key. Both protocols are robust against collective noise, and their qubit efficiency reaches 19.35%. In addition, the security analysis shows that both protocols are resistant to participant attacks and outside attacks, including intercept-resend attacks and entangle-measure attacks. This paper details the detection method of eavesdropping by eavesdroppers in collective noise through simulation, and finally presents key post-processing.