Van der Waals materials based superconducting qubits*

State-of-the-art superconducting qubits still face materials-limited roadblocks to improving coherence and scalability. Single-crystalline van der Waals (vdW) materials—with ultra-low defect densities, no dangling bonds, and atomically pristine interfaces—offer an ideal platform to circumvent these challenges in compact, long-coherence “merged-element transmon” qubits with 100x smaller footprint than conventional transmon architectures. We study vdW Josephson junctions with NbSe₂ electrodes and WSe₂ weak links of varying thickness and demonstrate Josephson coupling across WSe₂ tunnel barriers up to ~12 nm in thickness. Subgap resistance measurements reveal exceptional quality, with subgap-to-normal resistance ratios increasing exponentially with barrier thickness. These findings allow us to pinpoint the regime for constructing all-vdW-material transmons, and we offer preliminary insights into characterizing these novel qubits.