I Know What You Are Reading: Evaluating Readout Crosstalk in Cloud-based Quantum Computers
Abstract
Frequency-multiplexing is a technique used for achieving resource-efficient readout in superconducting-based quantum computers. By enabling multiple resonators to share a common feed line, it significantly reduces the number of required cables and passive components. However, this gain in scalability introduces increased readout crosstalk. The readout crosstalk is not only a reliability issue, but also a possible security issue. Prior work has explored readout crosstalk in experimental systems not publicly available. This work builds on the prior findings and evaluates readout crosstalk in commercial, cloud-based quantum computers. In the process, this work also reconstructs the likely architecture for the shared readout feed lines and shows which qubit readout resonators likely share a feed line. This work finally shows that crosstalk-induced errors occurring during readout can be exploited by adversaries to infer the state of co-located victim qubits, leading to unintended information leakage.
