Quantum Control of an Oscillator with a Kerr-cat Qubit

  1. Andy Z. Ding,
  2. Benjamin L. Brock,
  3. Alec Eickbusch,
  4. Akshay Koottandavida,
  5. Nicholas E. Frattini,
  6. Rodrigo G. Cortinas,
  7. Vidul R. Joshi,
  8. Stijn J. de Graaf,
  9. Benjamin J. Chapman,
  10. Suhas Ganjam,
  11. Luigi Frunzio,
  12. Robert J. Schoelkopf,
  13. and Michel H. Devoret
Bosonic codes offer a hardware-efficient strategy for quantum error correction by redundantly encoding quantum information in the large Hilbert space of a harmonic oscillator. However, experimental realizations of these codes are often limited by ancilla errors propagating to the encoded logical qubit during syndrome measurements. The Kerr-cat qubit has been proposed as an ancilla for these codes due to its theoretically-exponential noise bias, which would enable fault-tolerant error syndrome measurements, but the coupling required to perform these syndrome measurements has not yet been demonstrated. In this work, we experimentally realize driven parametric coupling of a Kerr-cat qubit to a high-quality-factor microwave cavity and demonstrate a gate set enabling universal quantum control of the cavity. We measure the decoherence of the cavity in the presence of the Kerr-cat and discover excess dephasing due to heating of the Kerr-cat to excited states. By engineering frequency-selective dissipation to counteract this heating, we are able to eliminate this dephasing, thereby demonstrating a high on-off ratio of control. Our results pave the way toward using the Kerr-cat to fault-tolerantly measure error syndromes of bosonic codes.
arxiv pdf

leave comment