  In this paper, we present a quantum-key-distribution (QKD)-based quantum
private query (QPQ) protocol utilizing single-photon signal of multiple optical
pulses. It maintains the advantages of the QKD-based QPQ, i.e., easy to
implement and loss tolerant. In addition, different from the situations in the
previous QKD-based QPQ protocols, in our protocol, the number of the items an
honest user will obtain is always one and the failure probability is always
zero. This characteristic not only improves the stability (in the sense that,
ignoring the noise and the attack, the protocol would always succeed), but also
benefits the privacy of the database (since the database will no more reveal
additional secrets to the honest users). Furthermore, for the user's privacy,
the proposed protocol is cheat sensitive, and for security of the database, we
obtain an upper bound for the leaked information of the database in theory.
