Fault-tolerant Operations for Universal Blind Quantum Computation

Abstract

Blind quantum computation is an appealing use of quantum information technology because it can conceal both the client's data and the algorithm itself from the server. However, problems need to be solved in the practical use of blind quantum computation and fault-tolerance is a major challenge. On an example circuit, the computational cost measured in T gates executed by the client is 97 times more than performing the original computation directly, without using the server, even before applying error correction. (The client still benefits due to drastically reduced memory requirements.) Broadbent et al. proposed running error correction over blind computation, but our first protocol applies one layer of Steane's [[7,1,3]] code underneath instead. This protocol has better fault tolerance, but still results in a substantial overhead. We propose another protocol to reduce the client's computational load by transferring the qubit preparation to the server. For each logical qubit used in the computation, the client is only required to receive eight logical qubits via teleportation then buffer two logical qubits before returning one. This protocol also protects the client's fault-tolerant preparation of logical qubits from a side-channel attack.