10:00–11:00 am
Please Join us:
Ming-Han Chou's PhD Thesis Defense
Tuesday November 29th, 2022 at 10:00 am CST
Quantum measurements of microwave-frequency acoustic resonators with superconducting circuits
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, and optical photons when using optomechanically active constructs. Phonons, thus, hold promise for quantum-focused applications as diverse as sensing, information processing, and communication. In this talk, we will describe a piezoelectric quantum bulk acoustic resonator with a 4.88 GHz resonant frequency, which, at cryogenic temperatures, displays large electromechanical coupling strength combined with a high intrinsic mechanical quality factor Q_i ~ 4.3*10^4. Using a recently developed flip-chip technique, we couple this resonator to a superconducting qubit on a separate die and demonstrate the quantum control of the mechanics in the coupled system. The resonator lifetime at a single phonon level is measured, which yields a Q_i ~ 4.43*10^3. This lower quality factor at a single phonon level is likely due to the two-level system (TLS) defects contamination in the device. To test whether this dissipation comes from the TLS defects, a hole-burning technique is implemented to saturate those defects. As a result, the resonator quality factor is enhanced back to Q_i ~ 3*10^4, demonstrating that TLS defects significantly contribute to our device's dissipation.
Committee Members:
Andrew Cleland (Chair)
Paolo Privitera
David Schuster
Giulia Galli
Ming-Han will be joining the AWS Center for Quantum Computing as a Research Scientist.