Flip-chip integration of high-impedance microwave and acoustic resonators

High-impedance microwave resonators, owing to their high zero-point voltage fluctuations, can enable strong capacitive coupling to other quantum systems, such as qubits or other resonators. Since high-impedance resonators typically have low self-capacitance, they are susceptible to stray capacitances. These stray capacitances can be reduced by careful design considerations. We couple a high-impedance surface acoustic wave resonator and a high-impedance superconducting microwave resonator in a flip-chip assembly with minimized stray capacitances. We demonstrate a capacitive coupling between the two resonators of about 6 MHz. This work serves as a model for other hybrid quantum systems with small capacitances.