The increasing accessibility of cloud quantum computing introduces vulnerabilities to circuit structure and timing information, potentially revealing sensitive algorithms to malicious parties. Samuel Punch and Krishnendu Guha, both from University College Cork, and their colleagues address this challenge with a new approach called Noise-Adaptive Dummy-Gate Obfuscation, or NADGO. This system actively enforces operational privacy for quantum workloads by strategically adding carefully controlled noise and masking techniques, limiting the amount of information that can be leaked through observable patterns. The research demonstrates that NADGO not only maintains confidentiality and enables fair access for multiple users, but also achieves lower latency and reduced power consumption compared to existing static methods, representing a significant step towards secure and efficient cloud quantum computing.
Operational privacy is increasingly important for gate-model workloads, necessitating methods to limit observable information leakage. To support both confidentiality and fair multi-tenancy, operators require an auditable compliance mechanism that introduces acceptable overhead. NADGO addresses this need by combining hardware-aware t-design padding for structured cover traffic, particle-filter timing randomisation to mask queue patterns, CASQUE subcircuit routing across heterogeneous backends, and a per-interval leakage estimator, bΔt, with locked calibration artefacts and a dual-threshold kill-switch. The team prototypes this system on a 4-qubit superconducting tile with cryo-CMOS control, and evaluates its performance using depth-varied local-random circuits and small QAOA benchmarks.
Noise-Aware Drift for Quantum Privacy
This research introduces NADGO (Noise-Aware Drift-Governed Orchestration), a system designed to provide per-interval operational privacy for gate-model quantum clouds. It addresses the emerging threat of timing side-channel attacks that could leak information about quantum computations. NADGO offers a solution by actively protecting the confidentiality of quantum computations, crucial for practical applications. NADGO combines several techniques to achieve operational privacy: hardware-aware t-design padding employs random quantum circuits to mask the underlying computation and introduce noise, making timing analysis more difficult.
Drift-robust timing randomization dynamically adjusts the timing of operations to further obscure execution time and account for hardware drift. CASQUE topology-aware routing routes quantum operations through a specific network topology to minimize information leakage and control execution paths. An online leakage estimator continuously monitors the leakage of timing information, and locked thresholds define acceptable leakage levels, triggering actions like aborting the computation if exceeded. Key features include per-interval privacy, providing guarantees for each computation interval, and auditable enforcement, with parameters and thresholds locked for verification.
NADGO uses calibration data to account for hardware characteristics and adapts to changing conditions. Experimental validation, using both Monte Carlo simulations and queue/timing-aware emulation, demonstrates the effectiveness of NADGO, showing it can maintain privacy while keeping performance overhead relatively low. The system operates through a four-stage process: quantum programs are compiled with t-design padding, a scheduler uses timing randomization and CASQUE routing, a monitor continuously assesses timing information, and enforcement mechanisms adjust or abort computations if leakage exceeds defined thresholds. Limitations include abstraction of vendor-specific hardware details and evaluation on relatively small quantum tiles. Future work includes scaling the system to larger quantum computers, addressing coordinated adversaries, exploring multi-region routing, and providing formal security proofs. In essence, NADGO is a comprehensive system that aims to provide practical and auditable operational privacy for quantum cloud services by combining hardware-aware techniques, dynamic adaptation, and secure enforcement mechanisms.
Privacy Safeguards for Quantum Computation Demonstrated
Researchers have developed NADGO, a comprehensive system that safeguards the operational privacy of gate-model quantum computers while maintaining performance and auditability. This innovative approach addresses vulnerabilities stemming from the leakage of information through scheduling metadata, timing patterns, and interference from co-tenants. The team successfully demonstrates a system capable of enforcing strict leakage limits during quantum computations, even under adversarial conditions. At the core of NADGO is a four-stage pipeline that begins with policy-aligned compilation, followed by the injection of dummy gates using a t-design padder to create cover traffic and obscure the circuit structure.
A particle-filter scheduler then dynamically adapts dispatch based on observed hardware drift, and CASQUE routing strategically distributes circuit segments across heterogeneous back-end resources. Crucially, a real-time leakage monitor continuously estimates information leakage and implements a kill-switch, aborting computations when pre-defined thresholds are exceeded, and recording all actions in an immutable audit log. Experiments reveal that NADGO maintains leakage within acceptable budgets during normal operation, with an interval-abort rate below 1 percent. Under attack scenarios, the system exhibits high separation, effectively shielding sensitive information.
Microbenchmarks demonstrate that, at matched leakage targets, NADGO achieves lower latency and cryogenic power consumption compared to static padding techniques, while maintaining competitive cost envelopes. The system was validated on a 4-qubit cryo-CMOS prototype, demonstrating its feasibility for near-term quantum hardware. This breakthrough delivers a significant advancement in quantum cloud security, providing a robust framework for protecting sensitive computations and enabling fair multi-tenancy. By integrating t-design padding, drift-adaptive timing, topology-aware routing, and auditable kill-switch monitoring, NADGO addresses key challenges to operational privacy, offering a unified solution that surpasses existing approaches. The team’s work paves the way for secure and trustworthy quantum cloud services, fostering wider adoption and accelerating the development of quantum technologies.
NADGO Limits Quantum Cloud Information Leakage
The research presents NADGO, a new system designed to protect the privacy of computations performed on cloud-based quantum services. It addresses the risk that sensitive information could be revealed through monitoring of circuit scheduling, timing patterns, and interference from other users. NADGO achieves this by combining techniques including structured cover traffic, randomized timing, and intelligent routing of quantum circuits, alongside a system for auditing compliance and detecting potential information leaks. The system operates by setting limits on the amount of observable information and triggering an abort if those limits are exceeded.
Evaluations using both simulated and emulated cloud environments demonstrate that NADGO effectively limits information leakage while maintaining competitive performance. The results show that the system introduces only small overheads in terms of latency and power consumption under normal operation, and that the abort rates remain low. Importantly, the research demonstrates that the system can reliably detect adversarial attempts to extract information, triggering higher abort rates as expected. The authors acknowledge that the current work focuses on specific attack vectors and that further research is needed to address a wider range of potential threats. Future work could explore the application of these techniques to different quantum computing architectures and the development of more sophisticated methods for detecting and mitigating information leaks.