Multi-user quantum private query

Abstract

Quantum private query (QPQ) is a kind of secure information retrieve protocol, in which both user and database privacy can be protected. Previous QPQ protocols generally consider one user retrieving and need to be performed repeatedly between each user and the database provider when multiple users want to retrieve information from a database. This work focuses on a particular scenario, where multiple users work together to accomplish a task and need to securely query the same item from a database, and proposes a multi-user QPQ protocol using entanglement swapping technology of multi-particle GHZ state. The security analysis shows that the user and database privacy are both guaranteed by real-time security detection.