In quantum private information retrieval (QPIR), a user retrieves a classical file from multiple servers by downloading quantum systems without leaking the identity of the retrived file to the servers. The QPIR capacity is the maximal achievalbe ratio of the size of the retrived file to the total download size. The QPIR capacity is derived for various settings: on the non-communicating servers, colluding servers, and distributed storage. The tight upper bound of the QPIR capacity is proved by entropic inequalities and the lower bound is derived by constructing capacity-achieving.


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