Multi-User Quantum Private Query Using Symmetric Multi-Particle W State

The previous quantum private query (QPQ) protocols based on quantum key distribution can only allow a single user to query the database. However, in the real environment, people can accomplish a task only by cooperating with each other. In this context, a multi-user quantum private query protocol based on multi-particle W state is first proposed, where users could query an item of common interest in the database only if they work together. The proposed multi-user protocol not only has all the advantages of single-user QPQ protocol, such as loss tolerance and cheat-sensitive, but also becomes more sensitive to database owner’s deception with the increasing of the number of users.