Stacked Josephson junctions for quantum circuit applications

Low-loss inductors are essential components in various superconducting circuits, such as qubits or digital electronics. In this study, we investigate highly compact inductors formed by vertical stacking of Josephson junctions. Our implementation employs multiple layers of aluminum separated by tunnel barriers. Individual stacks are connected by suspended superconducting bridges, which are free of additional dielectric materials and therefore should not contribute significantly to losses. We present implementation details, fabrication results, and device characterization measurements.