Broadband Bandpass Purcell Filter for Circuit Quantum Electrodynamics

  1. Haoxiong Yan,
  2. Xuntao Wu,
  3. Andrew Lingenfelter,
  4. Yash J. Joshi,
  5. Gustav Andersson,
  6. Christopher R. Conner,
  7. Ming-Han Chou,
  8. Joel Grebel,
  9. Jacob M. Miller,
  10. Rhys G. Povey,
  11. Hong Qiao,
  12. Aashish A. Clerk,
  13. and Andrew N. Cleland
In circuit quantum electrodynamics (QED), qubits are typically measured using dispersively-coupled readout resonators. Coupling between each readout resonator and its electrical environment however reduces the qubit lifetime via the Purcell effect. Inserting a Purcell filter counters this effect while maintaining high readout fidelity, but reduces measurement bandwidth and thus limits multiplexing readout capacity. In this letter, we develop and implement a multi-stage bandpass Purcell filter that yields better qubit protection while simultaneously increasing measurement bandwidth and multiplexed capacity. We report on the experimental performance of our transmission-line–based implementation of this approach, a flexible design that can easily be integrated with current scaled-up, long coherence time superconducting quantum processors.
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