Extending Superconducting Qubits Out of Plane (Part 1): Qubits with Air Bridge Crossovers in Multi-Tier Stacks*

Out-of-plane connectivity within superconducting quantum circuits enables increased complexity and wiring density. We are developing heterogeneous 3D integration of a qubit tier combined with an interposer with high-aspect-ratio superconducting through-silicon vias and a superconducting multi-chip module. In part 1 of this talk, we will focus on circuit complexity within the superconducting qubit tier, including implementation of air bridge crossovers (1) to increase mutual inductance by directly embedding them within qubit and coupler loops, (2) to improve connectivity of the ground plane, and (3) as a method for routing wires and circuit elements past each other.