  Quantum computing has undergone rapid development in recent years. Owing to
limitations on scalability, personal quantum computers still seem slightly
unrealistic in the near future. The first practical quantum computer for
ordinary users is likely to be on the cloud. However, the adoption of cloud
computing is possible only if security is ensured. Homomorphic encryption is a
cryptographic protocol that allows computation to be performed on encrypted
data without decrypting them, so it is well suited to cloud computing. Here, we
first applied homomorphic encryption on IBM's cloud quantum computer platform.
In our experiments, we successfully implemented a quantum algorithm for linear
equations while protecting our privacy. This demonstration opens a feasible
path to the next stage of development of cloud quantum information technology.
