A Lightweight Approach to Detect Malicious/Unexpected Changes in the Error Rates of NISQ Computers

Despite the current progress in quantum computing, the reliability of quantum computers is very challenging. Near-term quantum computers referred to as Noisy Intermediate-Scale Quantum (NISQ) computers are expected to operate in the presence of errors. To run a quantum circuit on a NISQ computer, the circuit should be mapped to satisfy the physical constraints of the quantum architecture. The mapping process takes into account the error rates of the quantum hardware. It selects physical qubits and their movements, which minimize the circuit error rates. The output of the quantum circuit can be obtained through several runs on NISQ computers. What's important from a security perspective is that the output of the quantum circuit is inherently dependent on the error parameters of the quantum hardware. An adversary can, therefore, leverage such dependency to alter the functional behavior of the quantum circuit. We show that malicious changes in the error rates used for mapping quantum circuits can change their output. To detect this attack on NISQ architectures, we propose inserting test points into the quantum circuits to study their error rates with respect to other qubit allocations. We utilize superposition, classical, and un-compute tests to provide side-channel information of the quantum circuit. We study the effectiveness of our approach using IBMQ 16 Melbourne quantum computer and Qiskit tools as an exemplar.