Quantum Private Query Protocol Based on Two Non-Orthogonal States

We propose a loss tolerant quantum private query (QPQ) protocol based on two non-orthogonal states and unambiguous state discrimination (USD) measurement. By analyzing a two-point attack by a third party, we find that our protocol has a stronger ability to resist external attacks than G-protocol and Y-protocol. Our protocol requires a smaller number of compressions than that in G-protocol (Gao et al., Opt. Exp. 2012, 20, 17411–17420) and Y-protocol (Yan et al. Quant. Inf. Process. 2014, 13, 805–813), which means less post-processing. Our protocol shows better database security and user privacy compared with G-protocol.