Secure Entanglement Distillation for Double-Server Blind Quantum Computation

Blind quantum computation is a new secure quantum computing protocol where a client, who does not have enough quantum technologies at her disposal, can delegate her quantum computation to a server, who has a fully fledged quantum computer, in such a way that the server cannot learn anything about the client’s input, output, and program. If the client interacts with only a single server, the client has to have some minimum quantum power, such as the ability of emitting randomly rotated single-qubit states or the ability of measuring states. If the client interacts with two servers who share Bell pairs but cannot communicate with each other, the client can be completely classical. For such a double-server scheme, two servers have to share clean Bell pairs, and therefore the entanglement distillation is necessary in a realistic noisy environment. In this Letter, we show that it is possible to perform entanglement distillation in the double-server scheme without degrading the security of blind quantum computing.

Figure 1

The single-server blind protocol. (a) Alice sends many single-qubit states to Bob. QD is a device which emits randomly rotated single qubits. (b) Bob creates a resource state. Alice and Bob perform measurement-based quantum computation through the two-way classical channel. CC is a classical computer.

Figure 2

The double-server blind protocol. (a) Bob1 and Bob2 share Bell pairs. Alice sends classical messages to Bob1. Bob1 performs measurements on his qubits of the Bell pairs and tells the measurement results to Alice. (b) Alice and Bob2 run the single-server blind protocol through the two-way classical channel. CC is a classical computer.