Quantum Private Information Retrieval
Ämin Baumeler · Repository for Publications and Research Data (ETH Zurich) · 2012
This thesis discusses Quantum Private Information Retrieval in the single-server scenario with information-theoretic privacy.We show that for such a protocol to be secure against the weakest reasonable adversary, the protocol requires a linear amount of communication.Hence, the trivial protocol for Quantum Private Information Retrieval is optimal.Furthermore, we discuss the mentioned weakest reasonable adversaries, called specious.As a motivation to this research, we analyze and break a recent protocol for Quantum Private Information Retrieval.i Note that due to the effect of phase-kickback, the above unitary may leak information about the index i to the register DB.However, this happens only in the case of non-classical inputs on the registers A or IDX.Because we assume that the client is honest, and hence does not perform queries in superpositions, we nevertheless use this unitary as the ideal functionality.