Travelling-wave parametric amplifiers based on Josephson metamaterials offer broadband gain with near-quantum-limited added noise, valuable for quantum information processing and sensing. Long devices deliver high gain but suffer from dissipation and standing waves, while short ones are cleaner but give less gain.

Researchers at Aalto University and VTT have combined both: a short, low-dissipation amplifier built from SNAIL elements as the first stage, followed by a conventional long amplifier. The cascade achieves nearly 30 dB of total gain over a tunable bandwidth of about 1 GHz, with added noise close to the quantum limit. The authors, Ilari Lilja, Ekaterina Mukhanova, Stanislav Khaldeev, Ilya Golokolenov, Visa Vesterinen and Pertti Hakonen, bring together QMAT's Hakonen group at Aalto and VTT.

The preprint has not yet been peer reviewed.

Image: QMAT