Exploring the fundamental limit of dielectric loss in the single-crystalline material*

Future quantum devices will require the use of dielectric materials with reduced loss in order to improve coherence. Van der Waals (vdW) materials possess desirable properties for superconducting quantum devices because they are single-crystalline, have ultra-low defect density, and lack dangling bonds. Moreover, the electronic properties of certain vdW materials can be tuned by electrostatic gating, such as the carrier density and superconducting gap energy. These characteristics can enable Josephson junctions with superior tunnel barrier homogeneity and low microwave loss, where the electric field is confined to ultra-clean vdW crystals and interfaces. We characterize the dielectric loss of vdW materials in parallel plate capacitors using superconducting resonators, showing that vdW materials are compatible with high-quality-factor superconducting quantum devices. Furthermore, we conduct a comparative analysis of vdW materials against other dielectric materials in terms of their loss tangent for quantum devices.