N quantum channels are sufficient for Multi-user Quantum Key Distribution protocol between n users

摘要

Quantum Key Distribution (QKD) protocols enable two parties to communicate in a secret manner. As it is necessary that there be a quantum channel between two users, n(n-1)/2 quantum channels are required for a QKD system of n users. We here propose a Multi-user Quantum Key Distribution protocol that utilizes entanglement swapping and by which only n quantum channels are needed for a communication system of n users. Any two among n users of the system can communicate with each other, even though there is no direct quantum channel between them. This is possible because entanglement swapping entangles the quantum states of the two users, establishing a quantum connection between them. Hence n quantum channels are sufficient for communication between n users. Furthermore, Trent, who performs entanglement swapping, has no way to fraudulently intervene in or eavesdrop on the communication between two users.