Transport and spectroscopy of junction Andreev bound states in half-shell nanowire transmon devices*

Semiconductor/superconductor hybrid nanowire-based devices in a cQED implementation are a promising platform for the detection of properties related to topological superconductivity. Here we study a gate-controlled Josephson junction, formed by selectively removing Al in a lithographically defined segment of a hybrid InAs/Al half-shell nanowire. The junction is incorporated in a transmon device geometry which enables both low-frequency transport studies and coherent time domain qubit control via cQED techniques. Variation of voltages on nearby electrostatic gates allows for drastic changes in the qubit frequency response as function of parallel magnetic field. The effects observed experimentally are in agreement with a theoretical model that suggests flux-modulated energies of Andreev bound states within the junction.