Semi-Quantum Private Query Protocol Without Invoking the Measurement Capability of Classical User

Recently, Yang et al. suggested a semi-quantum private query (SQPQ) protocol (Quantum Inf Process (2015)14:1017) using one quantum state. Later, Yu et al. (Quantum Inf Process (2015)14:4201) pointed out that Yang et al.'s SQPQ protocol runs the risk of user privacy being invaded, i.e., the database owner can manipulate the conclusiveness of bits definitely by launching a special kind of fake initial state attack, and then constructed an improved quantum private query (QPQ) protocol to avoid this risk. However, Yu et al.'s QPQ protocol is not semi-quantum. In this paper, we successfully design the SQPQ protocol without running the risk of user privacy being invaded. The proposed SQPQ protocol has the following features: (1) it only employs one kind of quantum state as the initial quantum state; (2) it doesn't require the classical user to perform the measurement operation; and (3) it is cheat-sensitive, which means that if the database privacy or the user privacy is invaded, the attack behavior can be detected.