Compact low-loss superconducting inductors utilizing vertically stacked Josephson junctions

Compact low-loss inductors are a central requirement for a wide variety of superconducting circuits, including qubits. For instance, long-lived fluxonium flux qubits commonly utilize inductors composed of chains of Josephson junctions. To reduce the footprint of these circuit elements, we investigate an alternative approach of making very compact Josephson junction arrays. We implement the chains of Josephson junctions by fabricating multiple aluminum layers separated by tunnel barriers and connecting such stacks of junctions with suspended superconducting bridges, free of additional dielectrics [1]. We will present the electrical characteristics of the stacks and evaluate the losses in these novel circuit elements.

[1] A. Kreuzer, et al. In preperation (2024)