POSTER: Stealthy SWAP-Based Side-Channel Attack on Multi-Tenant Quantum Cloud Systems
Wei Jie Bryan Lee, Siyi Wang, Siddartha Dutta, Walid El Maouaki, Anupam Chattopadhyay · 2025
The rapid advancement of quantum computing has led to an increased use of cloud-based quantum devices, raising concerns over the privacy and security of computations on multi-tenant quantum systems. Previous studies have explored crosstalk in these environments, but several questions remain regarding its causes, countermeasures, and applicability. In this work, we revisit the crosstalk effect, tracing it to the SWAP path between qubits, demonstrating its effectiveness even over long distances. Specifically, we introduce a SWAP-based side-channel attack in both active and passive modes, validated on real IBM quantum devices. In the active attack, a single CNOT gate disrupts Grover’s Algorithm from afar with an 81.62% reduction in output accuracy. The passive attack, using a circuit just 6.25% of the victim’s size, achieves 100% accuracy in predicting circuit attributes in Simon’s Algorithm. These findings challenge the existing defense strategy of maximizing topological distance between circuits, demonstrating that attackers can still extract sensitive information or manipulate results remotely.