Hybrid 2D-3D Heterostructures for Transmon Qubits

The crystalline nature of 2D materials has the potential to improve qubit quality by reducing dissipation due to two-level systems. However, many 2D superconductors present significant fabrication challenges, particularly with their significant oxidation and degradation in atmosphere. By using a deposited metal “via” technique and dry-polymer transfer, a 2D insulating tunnel barrier can be used alongside a 3D deposited superconductor. With this method, we can fabricate both a Josephson junction and a shunt capacitor for a transmon qubit in one highly compact footprint, while also improving qubit quality. We report measurements on this structure, and considerations for its integration into a larger superconducting quantum circuit.