Multi-user quantum private query using Bell states

Quantum private query (QPQ) can protect both user and database privacy when a user retrieves an entry from a database. Most existing QPQ protocols only support a single user retrieving a database, but in reality, people collaborate with each other to complete a task. Thus, it is necessary for multiple users to simultaneously retrieve a database. So far, all proposed multi-user QPQ protocols are based on high-dimensional quantum states and do not consider external attackers. In this paper, we present a multi-user QPQ protocol with two-way authentication based on Bell state and entanglement swapping technology. Under the premise of ensuring the privacy of users and the database, this protocol enables multiple users to simultaneously retrieve entries from a database. The security analysis demonstrates that the protocol can ensure privacy and resist external attacks.