  Two-dimensional (2D) transition-metal dichalcogenide superconductors have
unique and desirable properties for integration with conventional
superconducting circuits. However, fully superconducting contact must be made
between the 2D material and three-dimensional (3D) superconductors in order to
employ the standard microwave drive and readout of qubits in such circuits.
Here, we present a method for creating zero-resistance contacts between 2D
NbSe$_2$ and 3D aluminum that behave as Josephson junctions (JJs) with large
effective areas compared to 3D-3D JJs. We present a model for the supercurrent
flow in a 2D-3D superconducting structure by numerical solution of the
Ginzburg-Landau equations and find good agreement with experiment. These
results demonstrate a crucial step towards a new generation of hybrid
superconducting quantum circuits.
