INTEGRATING SUPERCONDUCTING QUBITS WITH QUANTUM FLUIDS AND SURFACE ACOUSTIC WAVE DEVICES

Superconducting qubits, mesoscopic superconducting circuits with a single quantum co- herent degree of freedom, have emerged as both a promising platform for quantum compu- tation and a versatile tool for creating hybrid systems with quantum mechanical degrees of freedom. In this dissertation, we report on several experiments investigating the coupling of superconducting 3D transmon qubits to two different systems: superfluid helium and piezo- electrically actuated surface acoustic waves (SAWs). We report the first measurements of superconducting qubits in the presence of superfluid helium, studying the spectroscopic and decoherence properties of this combined system. We analyze the spectroscopic properties of this composite system using the framework of circuit quantum electrodynamics, and in the presence of superfluid helium we observe modest increases in the pure dephasing time. We attribute this to improved thermalization of the microwave environment via the superfluid, raising hopes that thermalization mediated by superfluid helium may be a resource for ex- periments employing superconducting circuits. We also present ongoing work developing a new capacitive coupling scheme for creating hybrid superconducting qubit-SAW resonators. The tools developed to model and implement this experiment lay the groundwork for future experiments to achieve robust coupling between 3D transmon qubits and surface acoustic wave devices. Finally, we present results describing the first measurements of SAW induced transport in exfoliated graphene devices.