A Traveling Wave Parametric Amplifier with Improved Resilience to Fabrication Variations

Josephson junction-based traveling wave parametric amplifiers (JTWPAs) are widely used in cQED experiments for high-fidelity readout of superconducting qubits over a wide bandwidth. The bandwidth results from a transmission line configuration with thousands of Josephson junctions. However, fabrication imperfections such as Junction critical current variation limit their gain and noise performance.

In this work, we both develop a fabrication process that features a low relative standard deviation (RSD) in Josephson critical current and realize traveling wave parametric amplifiers with improved resilience to Junction critical current RSD. Devices fabricated with this process exhibit reduced self-oscillations and signal reflections. We study the sensitivity to process variation and outline the design elements that enable improved resilience. We perform Monte-Carlo modeling of cell-to-cell variation of circuit elements and evaluate the impact of non-uniformity on the gain, quantum efficiency, return loss, and insertion loss. Finally, we demonstrate improved readout performance using these JTWPAs.