Low-loss fabrication platform for superconducting microwave quantum circuitry

As superconducting qubit processors increase in size, complexity, and coherence, so must the adjacent quantum technology used to route, filter, or amplify the microwave signals to and from the qubits. These circuits require a versatile and low loss fabrication platform that can accommodate demanding circuit complexity, flexible wiring topologies and compact lumped-element components. At NIST, we developed a “Nb-trilayer” platform with Nb-Al/AlOx-Nb Josephson junctions (JJ) and low-loss amorphous silicon (a-Si) as inter-wiring dielectric that meets these demands. We present characterization and optimization of the fabrication process and show that it enables implementation of a variety of circuits: including DC- and RF-SQUID based Josephson parametric amplifiers (JPA), compact Purcell filters for superconducting qubits, and traveling-wave parametric amplifiers (TWPA) with thousands of JJs and low attenuation per unit length.  The versatility of the platform makes it suitable for a wide range of other low-loss superconducting circuits.