Hybrid 2D-3D Heterostructures for Merged Element Transmons*

Merged element transmon (MET) designs combine the Josephson junction and large shunting capacitor of a transmon qubit into a single circuit element. We explore a MET design utilizing the 2D insulator hexagonal boron nitride (hBN), which takes advantage of both its large band gap and low-defect crystalline nature to potentially improve qubit quality. Here, we demonstrate that by using flip-stack techniques in addition to traditional dry polymer transfer methods, deposited superconducting metals such as can be integrated into a 2D VdW heterostructure in a way that preserves the properties of clean 2D-3D interfaces throughout the stack. We report transport measurements in these structures, as well as discuss their integration into superconducting quantum circuits.