A stabilized logical quantum bit encoded in grid states of a superconducting cavity

  1. P. Campagne-Ibarcq,
  2. A. Eickbusch,
  3. S. Touzard,
  4. E. Zalys-Geller,
  5. N. E. Frattini,
  6. V. V. Sivak,
  7. P. Reinhold,
  8. S. Puri,
  9. S. Shankar,
  10. R. J. Schoelkopf,
  11. L. Frunzio,
  12. M. Mirrahimi,
  13. and M.H. Devoret
The majority of quantum information tasks require error-corrected logical qubits whose coherence times are vastly longer than that of currently available physical qubits. Among the many quantum error correction codes, bosonic codes are particularly attractive as they make use of a single quantum harmonic oscillator to encode a correctable qubit in a hardware-efficient manner. One such encoding, based on grid states of an oscillator, has the potential to protect a logical qubit against all major physical noise processes. By stroboscopically modulating the interaction of a superconducting microwave cavity with an ancillary transmon, we have successfully prepared and permanently stabilized these grid states. The lifetimes of the three Bloch vector components of the encoded qubit are enhanced by the application of this protocol, and agree with a theoretical estimate based on the measured imperfections of the experiment.
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