High-fidelity optical readout of a superconducting qubit using a scalable piezo-optomechanical transducer

  1. T.C. van Thiel,
  2. M.J. Weaver,
  3. F. Berto,
  4. P. Duivestein,
  5. M. Lemang,
  6. K. Schuurman,
  7. M. Žemlička,
  8. F. Hijazi,
  9. A.C. Bernasconi,
  10. E. Lachman,
  11. M. Field,
  12. Y. Mohan,
  13. F. de Vries,
  14. N. Bultink,
  15. J. van Oven,
  16. J. Y. Mutus,
  17. R. Stockill,
  18. and S. Gröblacher
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 high-fidelity multi-shot optical readout through an optical fiber of a superconducting transmon qubit connected via a coaxial cable to a fully integrated piezo-optomechanical transducer. Using a demolition readout technique, we achieve a multi-shot readout fidelity of >99% at 6 μW of optical power transmitted into the cryostat with as few as 200 averages, without the use of a quantum-limited amplifier. With improved frequency matching between the transducer and the qubit readout resonator, we anticipate that single-shot optical readout is achievable. Due to the small footprint (<0.15mm2) and the modular fiber-based architecture, this device platform has the potential to scale towards use with thousands of qubits. Our results illustrate the potential of piezo-optomechanical transduction for low-dissipation operation of large quantum processors.
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