Gate-Tunable Circuit QED Experiment in a Three-Dimensional Cavity Architecture*

Hybrid quantum systems based on nanowire Josephson junctions enable the realization of novel qubits such as gatemons, 0-<!--[if gte msEquation 12]> style='mso-bidi-font-style:normal'>π qubits and Andreev qubits. Furthermore, circuit quantum electrodynamics (circuit QED) can serve as a technique to probe Majorana zero modes. Previous related cQED experiments were performed in a two dimensional (2D) architecture involving superconducting coplanar waveguides. However, a magnetic field perpendicular to the substrate can significantly degrade the resonator performance and vortex pinning for in-plane magnetic field compatibility requires strenuous efforts. In this work, we present a three-dimensional copper cavity architecture design, compatible with a DC gate line and magnetic field, for probing hybrid devices. We test the design by demonstrating the gate-tunable qubit-cavity interaction and the qubit spectroscopy. Our technique allows the probing of hybrid superconducting-semiconductor devices in a 3D circuit QED architecture where gate voltages and a magnetic field are necessary.