High Saturation-Power Broadband NbTiN Parametric Amplifiers in a Traveling-Wave Architecture

We report the development of high-saturation-power parametric amplifiers based on the nonlinearity of high-kinetic-inductance (KI) superconducting materials, offering a promising alternative to conventional designs based on Josephson junctions~(JJs). While the saturation power of amplifiers based on JJs is constrained by the small critical current of JJs, KI-based devices often achieve output saturation powers up to 30-dB higher and operate reliably under higher temperatures and magnetic fields. Our implementation employs a 20-nm-thick NbTiN thin film in a coplanar-waveguide transmission line, with parametric gain provided by four-wave mixing in the gigahertz range. Phase matching among the interacting waves is maintained through resonators that control the pump tone’s phase shift.

The architecture provides over 15-dB of gain with minimal ripple across a 4-GHz bandwidth~(5.5-7.5 and 8.5-10.5 GHz), and a smaller footprint than conventional periodic-loading designs. By combining wide bandwidth, high gain, and significantly enhanced saturation power, KI-based parametric amplifiers present a viable pathway toward replacing semiconductor cryogenic amplifiers in quantum measurement systems.