Crystalline superconductor-semiconductor Josephson junctions for compact superconducting qubits

High-quality, single-crystal van der Waals (vdW) materials provide a promising platform for constructing Josephson junctions, but systematic studies have been limited by fabrication and measurement challenges. Here researchers characterize 24 vertical vdW superconductor-semiconductor junctions, including microwave spectroscopy of an all-vdW transmon qubit. Transport measurements reveal a crossover from proximity- to tunneling-type behavior with increasing semiconductor thickness. The results demonstrate how band alignment and materials engineering can be used to tailor qubit properties, establishing vdW heterostructures as an emerging platform for next-generation superconducting qubits.