We introduce a simple protocol for verifiable measurement-only blind quantum computing. Alice, a client, can perform only single-qubit measurements, whereas Bob, a server, can generate and store entangled many-qubit states. Bob generates copies of a graph state, which is a universal resource state for measurement-based quantum computing, and sends Alice each qubit of them one by one. Alice adaptively measures each qubit according to her program. If Bob is honest, he generates the correct graph state, and therefore Alice can obtain the correct computation result. Regarding the security, whatever Bob does, Bob cannot learn any information about Alice's computation because of the no-signaling principle. Furthermore, malicious Bob does not necessarily send the copies of the correct graph state, but Alice can check the correctness of Bob's state by directly verifying stabilizers of some copies.Blind quantum computing is a quantum cryptographic protocol that enables Alice (a client), who does not have any sophisticated quantum technology, to delegate her quantum computing to Bob (a server), who has a sufficiently powerful quantum computer, without leaking any her privacy. The first protocol of blind quantum computing that uses the measurement-based quantum computing [1] was proposed by Broadbent, Fitzsimons, and Kashefi [2], and a proof-of-principle experiment was demonstrated with photonic qubits [3]. In the protocol of Ref. [2], Alice generates many randomly-rotated singlequbit states, and sends them to Bob. Bob generates a universal resource state of the measurement-based quantum computing by applying entangling gates on qubits sent from Alice. Then, they do two-way classical communications: Alice instructs Bob how to measure each qubit, and Bob returns measurement results so that Alice can perform the feed-forward calculations. It was shown in Ref.[2] that if Bob is honest, Alice can obtain the correct quantum computing result (which we call the correctness), and that whatever evil Bob does, he cannot learn anything about Alice's input, output, and program (which we call the blindness) [4]. (See also Ref.[5] for a precise proof of the security.) Inspired by the seminal result, plenty of improvements have been done [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. For example, it was shown that instead of single-qubit states generation, single-qubit measurements [6] or coherent states generation [7] are sufficient for Alice. In the protocol of Ref. [6], so called the measurement-only blind quantum computing, Bob generates a universal resource state of measurement-based quantum computing (Fig 1(a)), and sends each qubit of the resource state one by one to Alice (Fig. 1(b)). Alice adaptively measures each qubit according to her program ( Fig. 1(b)). Since adaptive single-qubit measurements on certain states are universal [1,[21][22][23], Alice with only single-qubit measurements ability can perform universal quantum computing if Bob prepares the correct resource state. Furthermore, since this protocol is a o...

Blind quantum computation is a new secure quantum computing protocol which enables Alice who does not have sufficient quantum technology to delegate her quantum computation to Bob who has a fully-fledged quantum computer in such a way that Bob cannot learn anything about Alice's input, output, and algorithm. In previous protocols, Alice needs to have a device which generates quantum states, such as single-photon states. Here we propose another type of blind computing protocol where Alice does only measurements, such as the polarization measurements with a threshold detector. In several experimental setups, such as optical systems, the measurement of a state is much easier than the generation of a single-qubit state. Therefore our protocols ease Alice's burden. Furthermore, the security of our protocol is based on the no-signaling principle, which is more fundamental than quantum physics. Finally, our protocols are device independent in the sense that Alice does not need to trust her measurement device in order to guarantee the security.A first-generation quantum computer will be implemented in the "cloud" style, since only limited number of groups, such as governments and huge industries, will be able to possess it. How can a client of such a cloud quantum computing assure the security of his/her privacy? Protocols of blind quantum computation [1-11] provide a solution. Blind quantum computation is a new secure quantum computing protocol which enables a client (Alice) who has only a classical computer or a primitive quantum device which is not sufficient for universal quantum computation to delegate her computation to a server (Bob) who has a fully-fledged quantum computer without leaking any Alice's privacy (i.e., which algorithm Alice wants to run, which value Alice inputs, and what is the output of the computation) to Bob [1][2][3][4][5][6][7][8][9][10][11].The first example of blind quantum computation was proposed by Childs [1] where the quantum circuit model was used, and the register state was encrypted with quantum one-time pad [12] so that Bob who performs quantum gates learns nothing about information in the quantum register. In this method, however, Alice needs to have a quantum memory and the ability to perform the SWAP gate. The protocol proposed by Arrighi and Salvail [2] is that for the calculation of certain classical functions, i.e., not the universal quantum computation, and it requires Alice to prepare and measure multi-qubit entangled states. Furthermore, it is cheat-sensitive, i.e., Bob can gain information if he does not mind being caught. Finally, in their protocol, Bob knows the unitary which Alice wants to implement. Aharonov, Ben-Or and Eban's protocol [4] requires a constant-sized quantum computer with a quantum memory for Alice.On the other hand, in 2009, Broadbent, Fitzsimons and Kashefi [3] proposed a new blind quantum computation protocol which uses the one-way model [13][14][15][16]. In their protocol, all Alice needs are a classical computer and a primitive quantum device, w...

Blind quantum computation is a novel secure quantum-computing protocol that enables Alice, who does not have sufficient quantum technology at her disposal, to delegate her quantum computation to Bob, who has a fully fledged quantum computer, in such a way that Bob cannot learn anything about Alice's input, output and algorithm. A recent proof-of-principle experiment demonstrating blind quantum computation in an optical system has raised new challenges regarding the scalability of blind quantum computation in realistic noisy conditions. Here we show that fault-tolerant blind quantum computation is possible in a topologically protected manner using the Raussendorf–Harrington–Goyal scheme. The error threshold of our scheme is 4.3×10−3, which is comparable to that (7.5×10−3) of non-blind topological quantum computation. As the error per gate of the order 10−3 was already achieved in some experimental systems, our result implies that secure cloud quantum computation is within reach.