InAs-Nb Josephson Junctions for Voltage-Tunable Fluxonium Qubits

A path to higher temperature operation of qubits necessarily requires higher temperature superconductors such as Nb. While there is no conformal Nb oxide similar to Al oxide, in planar superconductor-semiconductor materials this can be remedied using layer-by-layer growth using molecular beam epitaxy. In this talk, we study Josephson junctions using Nb-InAs and compare their characteristics with Al-InAs devices. Next we discuss how these junctions can be incorporated into qubit architectures such as gatemonium, a voltage-controlled fluxonium for high temperature qubit operation. We discuss how the Josephson plasma frequency can be enhanced using Nb-based Josephson junction arrays with a larger energy gap.