  Quantum private query (QPQ) is the quantum version for symmetrically private
retrieval. However, the user privacy in QPQ is generally guarded in the
non-realtime and cheat sensitive way. That is, the dishonest database holder's
cheating to elicit user privacy can only be discovered after the protocol is
finished (when the user finds some errors in the retrieved database item). Such
delayed detection may cause very unpleasant results for the user in real-life
applications. Current efforts to protect user privacy in realtime in existing
QPQ protocols mainly use two techniques, i.e., adding an honesty checking on
the database or allowing the user to reorder the qubits. We reexamine these two
kinds of QPQ protocols and find neither of them can work well. We give concrete
cheating strategies for both participants and show that honesty checking of
inner participant should be dealt more carefully in for example the choosing of
checking qubits. We hope such discussion can supply new concerns when detection
of dishonest participant is considered in quantum multi-party secure
computations.
