Hardware-efficient erasure-error detection with an integer fluxonium

  1. Junyoung An,
  2. Helin Zhang,
  3. Jeffrey M. Gertler,
  4. Kate Azar,
  5. Renée DePencier Piñero,
  6. Michael Gingras,
  7. Junghyun Kim,
  8. Bethany M. Niedzielski,
  9. Ilan T. Rosen,
  10. Mollie E. Schwartz,
  11. Joel I.J. Wang,
  12. Terry P. Orlando,
  13. Jeffrey A. Grover,
  14. Max Hays,
  15. Kyle Serniak,
  16. and William D. Oliver
Erasure-error detection can improve the efficiency of quantum error correction by revealing the times and locations of their error events. In this work, we demonstrate erasure conversions and mid-circuit erasure detections in a single integer fluxonium, in which the states |g⟩,|f⟩ encode the logical states and |e⟩ encodes the erasure state. The integer fluxonium suppresses direct |f⟩→|g⟩ transitions and allows the dominant |f⟩→|e⟩ transitions to be converted into detectable erasures. Furthermore, we identified a design space that nullifies the resonant-frequency shift between the two logical states, enabling ancilla-free mid-circuit erasure checks using the same resonator employed for final readout. By discarding the detected erasure events, we achieved an 8.4-fold increase in the |f⟩ state lifetime, a 1.38-fold increase in the Hahn-echo time, and a reduction of single-qubit gate error from 0.061(2)% to 0.030(5)%. Our results establish integer fluxonium as a hardware-efficient platform for erasure-error detection and conversion, while identifying the improvements required to realize an effective erasure qubit with high erasure bias.
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