Superconducting-semiconducting voltage-tunable qubits in the third dimension*

We propose superconducting-semiconducting qubit and coupler designs based on high-quality, compact through-silicon vias (TSVs).  A "probe" chip is used to contact a sample chip with, for example, a superconductor-proximitized, epitaxially-grown, quantum well.  By utilizing the capacitance of the TSVs on the probe chip, the majority of the electric field in the qubits is pulled away from lossy regions that are present in the semiconducting wafer.  We find that the presence of the probe chip can reduce the qubit electric field participation in the sample wafer significantly.  We also show how this scheme is extensible to multi-qubit systems which have tunable qubit-qubit couplings without magnetic fields. This approach promises to accelerate the understanding of super-semi heterostructures in a variety of systems.