Quantum computing promises revolutionary advances across fields like medicine and security, but ensuring the confidentiality and reliability of computations performed on these machines presents a significant challenge. Paolo Bernardi, Antonio Brogi, and Gian-Luigi Ferrari, from the University of Pisa, Italy, alongside Giuseppe Bisicchia, address this critical need by developing a method to assess security properties within quantum circuits. Their work focuses on practical techniques for evaluating secrecy and integrity, particularly important as current quantum processors, known as Noisy Intermediate-Scale (NISQ) devices, are often operated by third-party providers who may not be fully trusted. This research establishes a crucial step towards building secure quantum systems and protecting sensitive data processed on these emerging technologies, offering a way to verify computations even when complete trust in the hardware provider is absent.
Current quantum computers possess limited qubits and are susceptible to noise, restricting the size and complexity of algorithms they can reliably execute. Despite these limitations, the potential for quantum computers to break existing cryptographic algorithms drives the development of quantum-resistant cryptography and, simultaneously, the need to secure quantum algorithms themselves. Traditional security methods for classical computers do not directly apply to quantum systems due to the fundamental differences in how they process information.
Quantum states are inherently probabilistic, and measurement alters these states, introducing complexities not found in classical systems. Furthermore, quantum circuit execution is vulnerable to errors from qubit decoherence, gate inaccuracies, and measurement errors, potentially compromising data integrity and confidentiality. Therefore, new techniques are needed to evaluate the security of quantum circuits and ensure reliable algorithm execution. This research addresses this need by investigating methods for formally verifying the security properties of quantum circuits, with a focus on confidentiality and integrity.
The research aims to create a framework that allows security experts to define security policies and automatically verify whether a given quantum circuit meets those policies. This framework combines techniques from formal methods, quantum information theory, and computer science to provide a comprehensive approach to quantum security evaluation. Ultimately, the goal is to build confidence in the secure execution of quantum algorithms and facilitate the development of trustworthy quantum computing systems.
Blind Quantum Computation for Untrusted Processors
With the availability of Noisy Intermediate-Scale Quantum (NISQ) devices, this work focuses on a practical approach to evaluate security properties, such as secrecy and integrity, when using quantum processors owned by potentially untrustworthy providers. The proposed approach utilizes blind quantum computation, allowing a client to delegate a quantum computation to a server without revealing the computation itself. This is achieved through a specific encoding scheme and a series of transformations applied to the quantum circuit, effectively masking the client’s input and algorithm. The methodology involves constructing a modified quantum circuit incorporating these transformations and then executing it on the remote quantum processor.
To verify the computation’s correctness without trusting the server, the client requests a set of measurement outcomes, which are then used to reconstruct the result of the original computation. The security of this approach relies on the computational difficulty of certain mathematical problems, ensuring the server cannot learn any information about the client’s computation or data. The methodology is evaluated by simulating quantum circuit execution on various NISQ devices and analysing the accuracy and efficiency of the security measures. Specifically, the team assesses the scheme’s resilience against potential server attacks and quantifies the overhead introduced by the encoding and transformation processes.
Distributed Quantum Computing Enhances Security and Reliability
This research investigates security and privacy in quantum computing, specifically addressing the challenges of running computations on near-term, noisy intermediate-scale quantum (NISQ) devices. The central idea is to explore methods for distributing quantum computations across multiple quantum computers to improve reliability, scalability, and security. A key technique investigated is quantum circuit cutting, which breaks down large quantum circuits into smaller pieces that can be executed on individual quantum computers and then recombined. The research emphasizes a probabilistic non-interference (PNI) based methodology for evaluating the security of these distributed computations.
Quantum circuit cutting divides a large quantum circuit into smaller, manageable sub-circuits, necessary because current quantum computers have limited qubit counts and coherence times. Distributed quantum computing executes these sub-circuits on multiple quantum computers in parallel, aiming to improve scalability and reduce the impact of errors on any single device. Probabilistic non-interference (PNI) is a security model used to ensure that the execution of a computation does not leak information about sensitive data. The authors use PNI as a framework for evaluating the security of their distributed quantum computation schemes.
The research contributes a framework for secure distributed quantum computing, using circuit cutting and PNI, and investigates the trade-offs between security, reliability, and performance. Practical implementations and benchmarks on real quantum hardware demonstrate the feasibility of the techniques. The work integrates with existing security techniques, such as circuit obfuscation and noise injection, and contributes to a roadmap for quantum software engineering.
Quantum Circuit Cutting Verifies Cloud Security
This research addresses a critical security challenge in cloud-based quantum computing, where users rely on third-party providers to execute sensitive computations. The work investigates methods to verify the confidentiality and integrity of information processed on these remote quantum processors, acknowledging the risk of malicious interference from the provider. Researchers developed a practical heuristic, grounded in the principles of probabilistic noninterference, to evaluate different configurations of a quantum circuit cutting technique. This approach divides complex computations into smaller parts, allowing execution on limited hardware while also offering a means to assess security properties.
The results demonstrate a pathway to compare the security of various quantum circuit cutting strategies, identifying configurations that offer greater resilience against adversaries with read and write access to sub-circuits. While acknowledging that probabilistic noninterference requires adaptation for quantum systems due to the nature of measurement and interference, the study provides a valuable framework for assessing security in this context. The authors note limitations stemming from the heuristic nature of their approach and suggest future work could focus on refining the methodology. This research contributes to building trust in cloud-based quantum computing by offering a means to evaluate and improve the security of remote computations.