Multi-User Quantum Private Query Protocol

Abstract

Recently, Gao et al. suggested a flexible quantum private query (QPQ) protocol (Opt Express, 2012, 20(16):17411) through Jakobi et al.’s quantum-key-distribution based QPQ protocol (Phys Rev A, 2011, 83:022301). Inspired by Gao et al.’s QPQ protocol, we design a multi-user QPQ protocol by using the product states of single-photon states. Its database privacy and user privacy should be compromised by choosing an suitable value for θ. Due to the honesty check process for the database owner, an smaller θ can be priorly chosen to guarantee better database privacy. Moreover, it naturally inherits some good characteristics of Gao et al.’s QPQ protocol so that it is also loss-tolerant, practical to huge-database condition, robust against quantum memory attack and flexible. It differs from Gao et al.’s QPQ protocol on three aspects: firstly, it adds the process of checking the presence of an illegal eavesdropper; secondly, it adds the process of checking the database owner’s honesty; and finally, it is feasible for n users to query the items of database simultaneously.