In cloud quantum computing, a classical client delegate quantum computing to a remote quantum server. An important property of cloud quantum computing is the verifiability: the client can check the integrity of the server. Whether such a classical verification of quantum computing is possible or not is one of the most important open problems in quantum computing. We tackle this problem from the view point of quantum interactive proof systems. Dr Tomoyuki Morimae is part of the Quantum Information Group at the Yukawa Institute for Theoretical Physics at Kyoto University, Japan. He leads a team which is concerned with two main research subjects: quantum supremacy and the verification of quantum computing.
In cloud quantum computing, a classical client delegate quantum computing to a remote quantum server. An important property of cloud quantum computing is the verifiability: the client can check the integrity of the server. Whether such a classical verification of quantum computing is possible or not is one of the most important open problems in quantum computing. We tackle this problem from the view point of quantum interactive proof systems. Dr Tomoyuki Morimae is part of the Quantum Information Group at the Yukawa Institute for Theoretical Physics at Kyoto University, Japan. He leads a team which is concerned with two main research subjects: quantum supremacy and the verification of quantum computing.
Blind quantum computing is a new secure quantum computing protocol where a client who does not have any sophisticated quantum technology can delegate her quantum computing to a server without leaking any privacy. It is known that a client who has only a measurement device can perform blind quantum computing [T. Morimae and K. Fujii, Phys. Rev. A 87, 050301(R) (2013)]. It has been an open problem whether the protocol can enjoy the verification, i.e., the ability of the client to check the correctness of the computing. In this paper, we propose a protocol of verification for the measurement-only blind quantum computing.
Limitations due to high costs and technological requirements will require users to access the first quantum processors through the cloud. Delegating a computation, however, raises privacy issues about the clients' data and poses questions about the verifiability of computations in high complexity regimes. These concerns have inspired a plethora of blind and verifiable quantum computation protocols, which allow a client with limited quantum capabilities to delegate a quantum computation to a remote server while hiding her data and preserving the integrity of the computation. The majority of these protocols are constrained to discrete quantum systems, but quantum information can also be processed by continuous-variable architectures. These offer a competitive alternative to their discrete-variable counterparts for numerous practical benefits: They rely on well-established quantum optical techniques, allow for the generation of very large optical resource states, offer higher detection efficiencies, and can be integrated into existing optical-fibre networks, all of which are highly desirable features for cloud quantum computing. In this work we fill this gap by presenting a blind and verifiable quantum computing protocol tailored to the unique features of continuous-variable systems. One such feature is the experimental accessibility of Gaussian operations. Our protocol is then based on the delegation of the experimentally challenging non-Gaussian operations. In this sense, it is experimentally friendly to the client, who only needs to perform Gaussian operations. Furthermore, unlike previous schemes, this protocol does not require repeated interactions between the client and server because it only involves the server sending the client non-Gaussian states. We prove universality and blindness using standard techniques, and we introduce an efficient fidelity test - based on homodyne detection - that allows the client to verify the correctness of the computation. This test is interesting in its own right because it could be employed in the context of state-certification of optical systems. The division of quantum hardware between client and server assumed here is typical of the experimental constraints expected in realistic, commercially useful schemes for continuous-variable cloud quantum computing. As such, we believe our protocol constitutes a significant advance towards their actual realisation.
The importance of being able to verify quantum computation delegated to remote servers increases with recent development of quantum technologies. In some of the proposed protocols for this task, a client delegates her quantum computation to non-communicating servers. The fact that the servers do not communicate is not physically justified and it is essential for the proof of security of such protocols. For the best of our knowledge, we present in this work the first verifiable delegation scheme where a classical client delegates her quantum computation to two entangled servers that are allowed to communicate, but respecting the plausible assumption that information cannot be propagated faster than speed of light. We achieve this result by proposing the first one-round two-prover game for the Local Hamiltonian problem where provers only need polynomial time quantum computation and access to copies of the groundstate of the Hamiltonian.
Abstract With the advent of cloud-based quantum computing, it has become vital to provide strong guarantees that computations delegated by clients to quantum service providers have been executed faithfully. Secure—blind and verifiable—delegated quantum computing (SDQC) has emerged as one of the key approaches to address this challenge, yet current protocols lack at least one of the following three ingredients: composability, noise-robustness and modularity. To tackle this question, our paper lays out the fundamental structure of SDQC protocols, namely mixing two components: the computation which the client would like the server to perform and tests that are designed to detect a server’s malicious behaviour. Using this abstraction, our main technical result is a set of sufficient conditions on these components which imply the security and noise-robustness of generic SDQC protocols in the composable Abstract Cryptography framework. This is done by establishing a correspondence between these security properties and the error-detection capabilities of the test computations. Changing the types of tests and how they are mixed with the client’s computation automatically yields new SDQC protocols with different security and noise-robustness capabilities. This approach thereby provides the desired modularity as our sufficient conditions on test computations simplify the steps required to prove the security of the protocols and allows to focus on the design and optimisation of test rounds to specific situations. We showcase this by systematising the search for improved SDQC protocols for bounded-error quantum polynomial-time ( BQP ) computations. The resulting protocols do not require more hardware on the server’s side than what is necessary to blindly delegate the computation without verification, and they outperform all previously known results.
In this paper, we propose a verifiable quantum cloud computation scheme based on blind quantum computation which effectively solves the privacy and verifiability problem for clients when interfacing with quantum computer in cloud computation. Different from most of present works (e.g. using brickwork state as resource state), we use cluster state with grid distributed structure to realize the universal and cryptographic calculation which is more suitable for the distributed architecture of cloud computation. Throughout the process, the random key is always held by the client that effectively promote the confidentiality. Moreover, we propose a new method to make the client Alice verifies the correctness of the results through only classical calculation. Security analysis shows that cloud server Bob can only obtain the dimension of input state and cluster state from the calculation, but cannot obtain any information of the input, the output and the algorithm. Dishonest Bob will be detected during the verification.
Blind quantum computing (BQC) allows a client to delegate quantum computations to a remote server without revealing the input, computation, or output. In addition to being blind, the client can sometimes also verify that the server has performed their instructions correctly, a property known as verifiability. A key part of realizing such verifiable BQC (VBQC) is choosing the design of the client device: many architectures have been proposed, each with different hardware requirements, security properties, and performance characteristics, making it difficult to identify which is most suitable for a given implementation. In this work, we present a comparative analysis of client architectures for VBQC with a matter-qubit server. We restrict our analysis to single-server, single-client protocols with information-theoretic security based on measurement-based quantum computation. We identify three main categories of client: emission-based, measurement-based, and rotation-based, each with multiple variants depending on how the client interacts with the server. We evaluate each across different dimensions: we compare guarantees of existing corresponding security proofs, we derive equations for the rate at which each client can execute a protocol, we provide an overview of each architecture's error behaviour, and discuss hardware cost and design considerations. Client architectures implementing measurement-based remote state preparation and reflection-based teleportation emerge as strong default candidates, but as the right choice remains context-dependent, we provide a framework for navigating considerations to guide the selection of the most suitable architecture for a given setting.