Reducing fabrication complexity of Josephson traveling-wave parametric amplifiers

Combining high-gain and near quantum-limited noise performance over a multi-GHz bandwidth, Josephson traveling-wave parametric amplifiers (JTWPA) [1] have become essential for characterizations in circuit-QED experiments, such as simultaneous multi-qubit readout in a large-scale superconducting quantum computer. While being highly sought-after, due to the need of phase and impedance-matching structures, JTWPAs often involve multi-layer and complex fabrications which hindered their wide adoptions in laboratories. In this work, we propose a JTWPA design with matching structures implemented using coplanar lumped-element waveguides, greatly simplifying the fabrication process. Without the use of oxide layers for capacitors found in conventional JTWPA designs, our device is expected to exhibit reduced insertion loss, which could further improve quantum efficiency in measurements. Preliminary experimental results will be presented.

[1] C. Macklin et al., Science 350, 6258 (2015)