Practical decoy-state quantum private queries against joint-measurement attack under weak coherent pulse sources

Quantum-key-distribution (QKD)-based quantum private queries (QPQs) are the most practical protocols for the symmetrically private information retrieval problem. But these protocols cannot resist joint-measurement (JM) attack. Recently, Wei et al. proposed a QPQ protocol with good performance in resisting JM attack (RJM-QPQ) (Phys. Rev. A 93, 042318 (2016)). However, due to the imperfections of ideal single-photon source, one has to consider the security of this protocol under weak coherent pulses sources (WCPS). In this paper, after analyzing the security loophole of RJM-QPQ protocol under WCPS, we propose a QPQ protocol with decoy-state method (DS-QPQ). Compared to the RJM-QPQ protocol, DS-QPQ has better performance under WCPS. It can also resist the JM attack. Furthermore, it improves database security, user privacy and efficiency. Moreover, DS-QPQ retains the good characters of QKD-based QPQs, e.g., it is loss tolerant and robust against quantum memory attack.