ABSTRACT With the advent of delegated quantum computing as a service, verifying the integrity of quantum computations is becoming a question of great importance. Existing information‐theoretically Secure Delegated Quantum Computing (SDQC) protocols require the client to possess the ability to perform either trusted state preparations or measurements. Whether it is possible to verify universal quantum computations with information‐theoretic security without trusted preparations or measurements was an open question so far. In this paper, we settle this question in the affirmative by presenting a modular, composable, and efficient way to turn known verification schemes into protocols that rely only on trusted gates. Our first contribution is an extremely lightweight reduction of the problem of quantum verification for to the trusted application of single‐qubit rotations around the axis and bit flips. The second construction presented in this work shows that it is possible to information‐theoretically verify arbitrary quantum computations without trusted preparations or measurements if the verifier can perform two‐qubit gates on a register whose size is logarithmic in the security parameter. Our third contribution extends these two results to the multi‐party setting in which multiple mutually distrustful clients delegate a joint computation to a potentially malicious server.
ABSTRACT With the advent of delegated quantum computing as a service, verifying the integrity of quantum computations is becoming a question of great importance. Existing information‐theoretically Secure Delegated Quantum Computing (SDQC) protocols require the client to possess the ability to perform either trusted state preparations or measurements. Whether it is possible to verify universal quantum computations with information‐theoretic security without trusted preparations or measurements was an open question so far. In this paper, we settle this question in the affirmative by presenting a modular, composable, and efficient way to turn known verification schemes into protocols that rely only on trusted gates. Our first contribution is an extremely lightweight reduction of the problem of quantum verification for to the trusted application of single‐qubit rotations around the axis and bit flips. The second construction presented in this work shows that it is possible to information‐theoretically verify arbitrary quantum computations without trusted preparations or measurements if the verifier can perform two‐qubit gates on a register whose size is logarithmic in the security parameter. Our third contribution extends these two results to the multi‐party setting in which multiple mutually distrustful clients delegate a joint computation to a potentially malicious server.
How can a user with limited quantum resources verify the output of an untrusted, fully quantum server? This manuscript provides a conceptual synthesis of some recent developments toward answering this question under statistical (information-theoretic) security. Rather than duplicating the dense technical proofs of the underlying publications, our focus here is on the physical motivations, the structural connections between different protocols, and the path toward hardware-efficient implementation.
We begin by introducing a modular, composable framework that partitions verification into three distinct, independent primitives: remote state preparation, trap-based deviation detection, and error-correcting embedding. Using this framework, we show how the demanding hardware requirements of early protocols can be systematically relaxed. We review schemes that eliminate the spatial overhead, remove the need to prepare computational-basis dummy states, and replace single-photon sources with trusted local rotations or weak coherent pulses. Finally, we examine how these techniques scale, both to asymmetric multi-party settings and to the delegation of fully fault-tolerant computations in the presence of gate-level noise. This document is intended as a guide to the architectural principles of practical quantum verification.
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.
Blind quantum computation (BQC) provides a secure framework for clients to delegate quantum computations to servers without revealing their private information. Among BQC protocols, those built on iterated gate teleportation (IGTBQC) have demonstrated promising potential in overcoming the constraints imposed by the no-programming theorem and significantly reducing communication overhead. However, existing IGTBQC protocols lack mechanisms for clients to verify the correctness of computation results and deal with only one type of clients capable of preparing qubits. To address these limitations, we first extend the current IGTBQC protocol to be a verifiable one and then propose another verifiable IGTBQC protocol tailored for a different type of clients with the capability of measuring single-qubit states. Furthermore, both protocols are shown to satisfy blindness and verification simultaneously in a relatively formal way. Our results not only broaden the applicability to a wider range of clients but also enhance the practicality of delegated quantum computation.
In the domain of quantum communication, cryptographic protocols often require users to have access to trusted qubit sources or detectors. Recently, it was shown that on an architecture called the Qline, several protocols can equivalently be performed by parties capable only of single-qubit rotations. In this work, we introduce two composably secure constructions that together show how in most quantum cryptographic protocols, parties traditionally required to perform trusted qubit preparation or measurement can delegate these tasks to an untrusted provider and instead rely on a trusted single-qubit rotation device. Our first construction implements single-qubit measurement and is universally applicable across any context. In contrast, our second construction, which addresses qubit preparation, relies on specific assumptions regarding the underlying protocol. We show, however, that these assumptions are inherently satisfied by the vast majority of common quantum cryptographic protocols. A notable consequence of our results is the formal validation of the Qline as a versatile architecture capable of supporting a wide range of single-qubit protocols.
We give a protocol for the delegation of quantum computation on encrypted data. More specifically, we show that in a client–server scenario, where the client holds the encryption key for an encrypted quantum register held by the server, it is possible for the server to perform a universal set of quantum gates on the quantum data. All Clifford group gates are non-interactive, while the remaining non-Clifford group gate that we implement (the π/8 gate) requires the client to prepare and send a single random auxiliary qubit (chosen among four possibilities), and exchange classical communication. This construction improves on previous work, which requires either multiple auxiliary qubits or two-way quantum communication. Using a reduction to an entanglement-based protocol, we show privacy against any adversarial server according to a simulation-based security definition.
Verifiable blind quantum computing is a secure delegated quantum computing where a client with a limited quantum technology delegates her quantum computing to a server who has a universal quantum computer. The client's privacy is protected (blindness), and the correctness of the computation is verifiable by the client despite her limited quantum technology (verifiability). There are mainly two types of protocols for verifiable blind quantum computing: the protocol where the client has only to generate single-qubit states and the protocol where the client needs only the ability of single-qubit measurements. The latter is called the measurement-only verifiable blind quantum computing. If the input of the client's quantum computing is a quantum state, whose classical efficient description is not known to the client, there was no way for the measurement-only client to verify the correctness of the input. Here we introduce a protocol of measurement-only verifiable blind quantum computing where the correctness of the quantum input is also verifiable.