Millimeter-Wave Four-Wave Mixing via Kinetic Inductance for Quantum Devices

Millimeter-wave superconducting devices offer a platform for quantum experiments at temperatures above 1 K, and new avenues for studying light-matter interactions in the strong coupling regime. Using the intrinsic nonlinearity associated with kinetic inductance of thin-film materials, we realize four-wave mixing at millimeter-wave frequencies, demonstrating a key component for superconducting quantum systems. We report on the performance of niobium nitride resonators around 100 GHz, patterned on thin (20--50-nm) films grown by atomic layer deposition, with sheet inductances up to $212\phantom{\rule{0.2em}{0ex}}\mathrm{pH}/◻$ and critical temperatures up to 13.9 K. For films thicker than 20 nm, we measure quality factors from $1\ifmmode\times\else\texttimes\fi{}{10}^{4}$ to $6\ifmmode\times\else\texttimes\fi{}{10}^{4}$, and explore potential loss mechanisms. Finally, we measure degenerate parametric conversion for a 95-GHz device with a forward efficiency up to $+16\phantom{\rule{0.2em}{0ex}}\mathrm{dB}$, paving the way for the development of nonlinear quantum devices at millimeter-wave frequencies.