UC Santa Barbara
Quantum control of surface acoustic wave phonons
- Author(s): Satzinger, Kevin Joseph
- Advisor(s): Cleland, Andrew N
- et al.
Quantum behavior in a macroscopic mechanical resonator is of great scientific and technological interest, but it is a substantial experimental challenge to realize. In particular, surface acoustic waves have emerged in recent years as a likely platform for coupling disparate quantum systems together. In this thesis, we present a surface acoustic wave resonator strongly coupled to a superconducting qubit. We begin by describing simple experiments with surface acoustic waves. Next, we discuss the design of a qubit and tunable coupler circuit to maintain good qubit performance in the presence of a surface acoustic wave resonator on an incompatible substrate. We then explain how to bring together devices on separate chips in a simple, accessible flip-chip assembly. Finally, we put these elements together to establish quantum control of surface acoustic wave phonons. We demonstrate good qubit performance and strong, tunable coupling to the acoustic mode. We show ground state cooling of the surface acoustic wave resonator with probability at least 99.5%. Finally, we illustrate quantum superposition in the surface acoustic wave resonator, conducting Wigner tomography of a superposition |0⟩ + |1⟩, which we find has fidelity 0.945 ± 0.006.