Josephson traveling-wave parametric amplifiers based on aluminum coplanar lumped-element waveguides*

Over the past decade, Josephson traveling-wave parametric amplifiers (JTWPAs) have become increasingly important for superconducting-circuit experiments such as multiplexed qubit readouts [1] and sensing [2]. However, the complexity in the design and fabrication of JTWPAs has slowed their adoption in the community. Despite on-going efforts, the insertion loss of the underlying waveguide in most existing JTWPAs is still relatively high, limiting their potential applications beyond signal amplification.

 

In this work, we propose a four-wave-mixing JTWPA design based on aluminum coplanar lumped elements and Josephson junctions, where phase-matched gain is achieved with a periodic modulation in their geometries. Without the use of a lossy dielectric layer commonly found in JTWPA unit cells, our design allows a simplified JTWPA fabrication process and a further reduction in the insertion loss, enabling amplification with higher quantum efficiency. We discuss typical issues in periodic-loading JTWPA designs, and how to avoid them.

 

[1] J. Heinsoo et al., Phys. Rev. Applied 10, 034040 (2018)

[2] C. Bartram et al., Rev. Sci. Instrum., 94, 044703 (2023)