Optical readout of superconducting qubits using piezo-optomechanical transducers

Superconducting quantum processors have made significant progress in size and computing potential. As a result, the practical cryogenic limitations of operating large numbers of superconducting qubits are becoming a bottleneck for further scaling. Due to the low thermal conductivity and the dense optical multiplexing capacity of telecommunications fiber, converting qubit signal processing to the optical domain using microwave-to-optics transduction would significantly relax the strain on cryogenic space and thermal budgets. Here, we demonstrate optical readout of a superconducting transmon qubit connected via a coaxial cable to a fiber-coupled piezo-optomechanical transducer. Using a demolition readout technique, we achieve a single shot readout fidelity of 81%. We further demonstrate that the optical pump has minimal impact on qubit decoherence times. With further improvement to our transducer and by leveraging the modular fiber-based nature and small footprint of this device platform, we envision all-optical dispersive qubit readout of thousands of qubits in parallel.