Variational quantum circuits represent a promising frontier in computation, offering potential advantages for problems beyond the reach of conventional computers, but their design demands considerable resources and expertise, making them valuable intellectual property. Cheng Chu, Lei Jiang, and Fan Chen from Indiana University Bloomington present a new watermarking scheme, BVQC, designed to protect these circuits from unauthorised use. Unlike existing methods that can be removed during circuit optimisation or significantly reduce performance, BVQC introduces a subtle “backdoor” that preserves original performance during normal operation, yet reveals the watermark when triggered. This innovative approach minimises interference with the circuit’s primary task, maintaining accuracy while demonstrably improving upon existing watermarking technologies in terms of both authorship proof and watermark detection reliability.
Existing quantum circuit watermarking techniques often fail because watermarks can be removed during circuit re-compilation, and these methods significantly increase task loss due to the extensive length of inserted watermarks. To address these challenges, the research proposes BVQC, a backdoor-based watermarking technique for VQCs that preserves the original loss in typical execution settings, while deliberately introducing a detectable anomaly when triggered.
Backdoor Embedding Protects Quantum Circuit Ownership
This research addresses the crucial need to protect intellectual property in the rapidly developing field of quantum computing. As quantum algorithms become more complex, ensuring ownership and preventing unauthorized use is a significant challenge. The team introduces a novel watermarking approach, BVQC, that embeds a backdoor into the variational quantum circuit (VQC). This means the circuit performs well on a specific task unless a predefined input is used, at which point it reveals the watermark. The BVQC scheme minimizes performance overhead by carefully selecting watermark configurations that conflict minimally with the base task. Furthermore, the watermark is embedded directly into the unitary matrix of the VQC, making it resistant to circuit re-compilation, a common optimization technique that destroys traditional watermarks. The authors validate the effectiveness of their scheme through simulations and experiments on quantum hardware.
Protecting Quantum Circuit Designs with Watermarks
Researchers have developed a new technique to protect the intellectual property embedded within variational quantum circuits (VQCs). VQCs are increasingly used for complex calculations, but their designs are vulnerable to unauthorized copying. Existing watermarking methods suffer from being removed during standard circuit optimization processes and reducing the accuracy of the calculations. This new approach, termed BVQC, addresses these limitations by embedding a watermark that remains hidden during typical circuit execution but becomes detectable when specifically targeted for extraction. Unlike previous methods that alter the circuit, BVQC minimizes interference with the core calculation, preserving the original accuracy of the VQC.
The technique achieves this by designing the watermark as a “backdoor,” meaning it only impacts the results when intentionally activated for verification purposes. Evaluations demonstrate that BVQC significantly improves upon existing watermarking technologies, reducing changes to a key metric called Probabilistic Proof of Authorship (PPA) and ground truth distance (GTD). Importantly, the watermark remains robust even after the circuit undergoes recompilation. Tests show that while prior watermarking methods experienced a substantial increase in PPA after recompilation, BVQC maintains its integrity. Furthermore, the technique minimizes accuracy degradation, demonstrating a lower GTD compared to circuits watermarked with earlier technologies. This combination of robustness and minimal performance impact represents a significant advancement in protecting quantum intellectual property and fostering innovation.
BVQC Watermarking Protects Quantum Circuit Integrity
This research introduces a new watermarking scheme, BVQC, designed to protect the intellectual property embedded within variational quantum circuits. Existing methods often suffer from watermarks being removed during circuit re-compilation and introducing significant errors that degrade performance. BVQC addresses these limitations by embedding a ‘backdoor’ into the circuit’s design, intentionally increasing loss only when the watermark is being extracted, while maintaining accuracy during normal operation. Evaluations demonstrate that BVQC significantly reduces both changes in Probabilistic Proof of Authorship and ground truth distance, key metrics for watermark integrity and accuracy, compared to previous techniques.
The method achieves this by carefully selecting watermark configurations that minimise interference with the circuit’s primary task, ensuring optimal performance even with the watermark present. While the research demonstrates improved watermark robustness and reduced performance impact, the authors acknowledge the ongoing need for methods that can withstand increasingly sophisticated attacks and circuit optimisation processes. Future work may focus on enhancing the scheme’s resilience against these evolving threats and exploring its application to a wider range of quantum algorithms.