Quantum private query based on quantum homomorphic encryption with qubit rotation

In the current era of big data, the privacy of user behavior is as important as the privacy of their data. In this paper, we propose a single ternary quantum homomorphic encryption (QHE) protocol based on qubit rotation, which has high security and flexibility. The user utilizes the classical angle as the key for QHE, and encryption and decryption do not need to be implemented in a specific order. Based on this flexible QHE protocol, we further propose a quantum privacy query (QPQ) protocol. Our protocol uses homologous encryption to send query requests and obtain results after processing with an oracle machine-which exists independently of the database-in one round of communication. Our protocol has advantages in terms of its feasibility and efficiency. In addition to this, our protocol offers new ideas for implementing QPQ.