Measurements of a quantum bulk acoustic resonator using a superconducting qubit

  1. M.-H. Chou,
  2. É. Dumur,
  3. Y. P. Zhong,
  4. G. A. Peairs,
  5. A. Bienfait,
  6. H.-S. Chang,
  7. C. R. Conner,
  8. J. Grebel,
  9. R. G. Povey,
  10. K. J. Satzinger,
  11. and A. N. Cleland
Phonon modes at microwave frequencies can be cooled to their quantum ground state using conventional cryogenic refrigeration, providing a convenient way to study and manipulate quantum states at the single phonon level. Phonons are of particular interest because mechanical deformations can mediate interactions with a wide range of different quantum systems, including solid-state defects, superconducting qubits, as well as optical photons when using optomechanically-active constructs. Phonons thus hold promise for quantum-focused applications as diverse as sensing, information processing, and communication. Here, we describe a piezoelectric quantum bulk acoustic resonator (QBAR) with a 4.88 GHz resonant frequency that at cryogenic temperatures displays large electromechanical coupling strength combined with a high intrinsic mechanical quality factor Qi≈4.3×104. Using a recently-developed flip-chip technique, we couple this QBAR resonator to a superconducting qubit on a separate die and demonstrate quantum control of the mechanics in the coupled system. This approach promises a facile and flexible experimental approach to quantum acoustics and hybrid quantum systems.
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