Quantum Computer Security

Updated 12 October 2025

Quantum computer security is a discipline that safeguards quantum systems, data, and infrastructures from threats emerging at the quantum-classical interface.
It addresses vulnerabilities such as crosstalk, side-channel leakage, and compiler attacks using methods like QTEE and QPUFs.
Research focuses on integrating classical and quantum defenses to secure cloud-based environments and maintain system integrity against adversarial interference.

Quantum computer security is the discipline concerned with protecting quantum computers, quantum data, and associated ecosystems (hardware, software, and cloud infrastructure) against an expanding spectrum of threats that emerge from both the unique physical properties of quantum information and the hybridization with classical control hardware. Unlike post-quantum cryptography, which focuses on defending traditional systems from quantum-enabled attacks, quantum computer security directly addresses the vulnerabilities intrinsic to quantum computing platforms themselves, including adversarial interference, side-channel leakage, intellectual property theft, and system integrity in multi-tenant or cloud-based environments (Deshpande et al., 7 Oct 2025).

1. Security Principles and Unique Vulnerabilities

Quantum computer security is shaped by a mixture of quantum-mechanical advantages and distinctive risks. The no-cloning theorem provides fundamental protection against copying arbitrary quantum states; formally, for any unknown $|\psi\rangle$ , there exists no universal unitary $U$ such that $U(|\psi\rangle \otimes |e\rangle) = |\psi\rangle \otimes |\psi\rangle$ . This precludes attacks analogous to classical memory cloning but offers no immunity to other classes of compromise (Deshpande et al., 7 Oct 2025).

Quantum hardware diverges from classical computers in its dependence on complex, physically accessible control systems—including FPGAs, mixers, RF sources, and extensive cabling—which enlarge the physical attack surface relative to hermetically sealed microchip-based systems. Major vulnerabilities arise through these classical-quantum interfaces. The susceptibility is accentuated in modular, data-center-deployed systems, where physical or logical access is less constrained (Deshpande et al., 7 Oct 2025, Ghosh et al., 2023).

Key vulnerabilities include:

Crosstalk Attacks: In shared quantum systems, operations on one set of qubits can induce errors in adjacent qubits, intentionally or unintentionally, due to residual couplings (Deshpande et al., 7 Oct 2025, Ovaskainen et al., 23 Jul 2025).
Side-Channel Leakage: Timing variations, power consumption, and incomplete qubit reset procedures may reveal gate sequences or partial program information (Deshpande et al., 7 Oct 2025, Xu et al., 2023).
Compiler and Software Attacks: Untrusted compilation services can analyze, modify, or watermark proprietary circuits; adversaries may also embed "QTrojan" circuits hidden as innocuous pulse calibrations that undermine the security of computation (Deshpande et al., 7 Oct 2025).
Multi-tenant and Cloud Risks: Quantum cloud services expose users to insider threats, where physical access or observability at the provider side allows for information leakage or tampering (Deshpande et al., 7 Oct 2025, Coupel et al., 27 Apr 2025).

While quantum mechanics blocks certain classic exploits, it simultaneously demands novel defenses at every layer of the quantum stack.

2. Physical and Hardware-Level Attacks

Quantum hardware security must address:

Physical Probing: Direct probing of control lines, components, or temperature-sensitive setups can leak information about program execution (Deshpande et al., 7 Oct 2025).
Crosstalk Exploitation: Deliberate injection of noise or adversarial circuit placement exploits inter-qubit couplings. Experimental results report correct output probabilities for typical quantum algorithms (like Grover's search) dropping below 20% under targeted crosstalk, scaling approximately as $P_\text{correct} \approx (1-\epsilon)^n$ , where $\epsilon$ is the error introduced per adversary-induced gate (Ovaskainen et al., 23 Jul 2025, Ghosh et al., 2023).
Side-Channel Harvesting: Pulsed control electronics (AWGs, FPGAs) can be monitored for timing and power characteristics; advanced power-based side-channel attacks reconstruct gate-level circuit structure from per-qubit channel traces using metrics such as $P_c[p_c(x)] = \operatorname{Re}^2[p_c(x)] + \operatorname{Im}^2[p_c(x)]$ (Xu et al., 2023).
Incomplete Reset and State Leakage: Reset gates may not reliably return qubits from higher-lying states (e.g., $|2\rangle$ in superconducting devices), allowing adversarial "bleed" of information or persistent errors across jobs (Ovaskainen et al., 23 Jul 2025).

Widespread adoption of quantum cloud and multi-programming augments the risk of such attacks, given the increased privilege and observability afforded to operators and co-located users.

3. Software and System-Level Threats

The software stack and execution environment introduce additional routes for compromise:

Compiler Attacks and QTrojan Injection: Malicious or compromised compilers can insert backdoors, extract circuit intellectual property, or watermark workloads for later identification. The QTrojan attack—embedding modifications as subtle, seemingly routine calibration operations—allows for stealthy disruption of data encoding or logical gate mapping (Deshpande et al., 7 Oct 2025).
Obfuscation and Watermarking: Defensive approaches such as circuit obfuscation, watermarking, and splitting (dividing sensitive computations across devices) complicate reverse engineering but currently are active areas of research rather than standardized practice (Deshpande et al., 7 Oct 2025, Ghosh et al., 2023).
Quantum Antivirus and Pattern Detection: Early work demonstrates subgraph isomorphism-based detection for crosstalk-generating malicious subcircuits, functioning analogously to classical antivirus (Deshpande et al., 7 Oct 2025).
Multi-Tenancy Software Risks: In shared regimes, adversaries can deliberately occupy well-connected qubits to force victim circuits onto noisier paths (adversarial SWAP injection), or can perform "qubit sensing" to infer outcomes on adjacent logical registers using statistical distance metrics on readout distributions (Ovaskainen et al., 23 Jul 2025).

System-level defenses require integration of quantum-specific anomaly detection, access controls, and active monitoring throughout the execution stack.

4. Trusted Execution and Hardware Authentication

To counter both physical and software-layer threats, several hardware-rooted defenses are explored:

Quantum Trusted Execution Environments (QTEE): Secure hardware enclaves resident on the cryogenic side of dilution refrigerators decrypt and control access to user circuits, apply decoy pulse obfuscation, and use tamper-detection mechanisms to erase sensitive keys or input mappings upon intrusion. Decoy control pulses are inserted, and only the QTEE, protected by post-quantum public-key cryptography, knows which pulses are genuine; variational distance metrics $\delta(P, Q) = \frac{1}{2} \sum |P - Q|$ are used to calibrate the fidelity-security tradeoff (Trochatos et al., 2023).
Quantum Physical Unclonable Functions (QPUFs): These exploit unique gate error rates and decoherence patterns to generate chip-specific, clone-resistant fingerprints for device authentication, mitigating risk of hardware replication or misallocation in cloud jobs (Phalak et al., 2021, Ghosh et al., 2023). Metrics such as the intra-die Hamming distance (as low as 4%) and inter-die Hamming distance (around 55%) quantify their discriminability.
Device Fingerprinting/Watermarking: Methods such as embedding known subcircuits or parameter perturbations into workloads (watermarking) or extracting decoherence signatures (fingerprinting) have been proposed to track circuit provenance or detect unauthorized device substitutions (Deshpande et al., 7 Oct 2025, Ghosh et al., 2023).

These mechanisms shift some elements of trust from software to hardware, recognizing the limitations of purely logical security in hybrid quantum-classical systems.

5. Side-Channel and Multi-Tenant Security

Quantum computer security must account for an expanded taxonomy of side-channel and multi-tenant threats:

Power and Timing Side-Channels: Even with the no-cloning theorem, classical control hardware (e.g., room-temperature FPGAs) can emit power or timing signals from which adversaries infer quantum circuit identities or data, including shot structure, gate sequences, and device type (Xu et al., 2023).
Circuit Reconstruction Attacks: By analyzing sandwiched execution timing or output statistics, attackers using neural network classifiers achieve up to 65% success in distinguishing victim firmware (Ovaskainen et al., 23 Jul 2025).
Blueprinting and Resource Contention: Adversaries can reconstruct hardware topology via measured crosstalk and timing, enabling targeted attacks despite attempts at obfuscation by providers (Ovaskainen et al., 23 Jul 2025).
Insider Threats: Personnel with physical access can monitor control signals or directly observe SFQ-based control systems, using bias current deviations $\Delta I_\text{bias} = f(n_\text{switches}, t_\text{switch})$ to infer gate activities (Coupel et al., 27 Apr 2025).

Emerging architectural solutions include logic locking, camouflaging, and entropy-based anomaly detection, but performance-security tradeoffs remain unresolved.

6. Research Direction and Defenses

Current and future defense strategies span:

Blind Quantum Computation: Protocols that keep the client’s inputs, operations, and outputs private from the server via cryptography or obfuscated encodings are proposed but require further development for large-scale and noisy hardware (Ghosh et al., 2023, Saki et al., 2021).
Circuit Obfuscation and Splitting: Defensive programming—including insertion of dummy gates, circuit segmentation, or separation of sensitive tasks—reduces IP leakage and attack effectiveness (Deshpande et al., 7 Oct 2025, Ghosh et al., 2023).
Anomaly and Pattern Detection: Statistical and machine-learning techniques for process and output monitoring are being adapted to quantum control flows for early detection of suspicious activity or program deviation (Ovaskainen et al., 23 Jul 2025).
Integration of Classical and Quantum Countermeasures: Compilers and cloud platforms are evolving to combine noise/error mitigation with security enforcement—prioritizing resource allocation to limit adversarial crosstalk and optimize hardware utilization while maintaining isolation (Ovaskainen et al., 23 Jul 2025, Saki et al., 2021).

Research continues in taxonomies for threat analysis (Deshpande et al., 7 Oct 2025), modeling of attack surfaces unique to quantum-classical hybrid platforms, and development of standardized hardware/software certification procedures.

7. Comparison with Traditional Computer Security

Quantum computer security both inherits and diverges from classical paradigms. While layered defense-in-depth remains valuable, quantum platforms are characterized by their physicality, nonlocal interactions, and the necessity to secure interfaces across a quantum-classical boundary. Quantum-specific features—like the no-cloning theorem—provide some native immunity but do not compensate for new threats introduced by the combinatorial complexity of physical observables, side-channel emissions, and untrusted code paths (Deshpande et al., 7 Oct 2025).

In contrast to the classical norm of exclusive reliance on cryptographic verification and software access control, quantum systems must invest in hardware identity mechanisms (e.g., QPUFs), trusted hardware enforcement (QTEE), novel anomaly detectors, and hybrid approaches that bridge post-quantum cryptography with physical security controls (Deshpande et al., 7 Oct 2025, Trochatos et al., 2023, Ghosh et al., 2023). The center of gravity in quantum computer security shifts toward the orchestration of cryptographic, physical, and architectural defenses across an extended attack surface.

Overall, quantum computer security emerges as a multifaceted discipline at the intersection of quantum physics, hardware engineering, system architecture, and cybersecurity. Its goal is to anticipate and defeat threats that are distinctive both in their physical origins and in their exploitation of the hybrid quantum-classical stack—a landscape certain to expand as quantum hardware matures and integrates further with distributed, cloud-native infrastructures (Deshpande et al., 7 Oct 2025, Xu et al., 2023, Ghosh et al., 2023).