2025-10-30 理化学研究所
Web要約 の発言：
図1 新規進行波型ジョセフソンパラメトリック増幅器（JTWPA）の設計と性能の概要
＜関連情報＞
- https://www.riken.jp/press/2025/20251030_1/index.html
- https://journals.aps.org/prapplied/abstract/10.1103/qhl6-cz2z
低固有損失集積素子コプラナ波導管を用いたジョセフソン進行波パラメトリック増幅器 Josephson traveling-wave parametric amplifier based on a low-intrinsic-loss lumped-element coplanar waveguide
C.W. Sandbo Chang, Arjan F. Van Loo, Chih-Chiao Hung, Yu Zhou, Christian Gnandt, Shuhei Tamate, and Yasunobu Nakamura
Physical Review Applied Published: 27 October, 2025
DOI: https://doi.org/10.1103/qhl6-cz2z
Abstract
We present a Josephson traveling-wave parametric amplifier (JTWPA) based on a low-loss lumped-element coplanar waveguide architecture. By employing open-stub capacitors and Manhattan-pattern junctions, our device achieves an insertion loss below 1 dB up to 12 GHz. We introduce windowed sinusoidal modulation for phase matching, demonstrating that a smooth transition in the impedance-modulation strength effectively suppresses intrinsic gain ripples. Using Tukey-windowed modulation with 8% impedance variation, we achieve 20–23-dB gain over 5-GHz bandwidth under ideal matching conditions. In a more practical circuit having impedance mismatches, the device maintains 17–20-dB gain over 4.8-GHz bandwidth with an added noise of 0.18 quanta above standard quantum limit at 20-dB gain and −99-dBm saturation power, while featuring zero to negative backward gain below the band-gap frequency.
