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arXiv · 2504.17145

Broadband Kinetic-Inductance Parametric Amplifiers with Impedance Engineering

Chih-Chiao Hung·Hiroki Kutsuma·Chung Wai Sandbo Chang·Arjan Ferdinand van Loo·Yasunobu Nakamura
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Abstract

Broadband quantum-limited parametric amplifiers (PAs) are essential components in quantum information science and technology. Impedance-engineered resonator-based PAs and traveling-wave PAs are the primary approaches to overcome the gain-bandwidth constraint. While the former PAs are simpler to fabricate, the target characteristic impedance Z_\text{NR} of the nonlinear resonator has been restricted to be below 10 \Omega, requiring large capacitance. Moreover, these PAs have only been implemented with aluminum-based Josephson junctions (JJs), hindering their operation at high temperatures or strong magnetic fields. To address these issues, we propose a three-stage impedance-transformer scheme, showcased with a 20-nm-thick, 250-nm-wide high-kinetic-inductance niobium-titanium-nitride (NbTiN) film. Our scheme enables Z_\text{NR} up to several tens of ohms--a tenfold improvement over conventional designs, achieved through an additional quarter-wavelength transmission line with the characteristic impedance of 180 \Omega. Our kinetic-inductance impedance-engineered parametric amplifiers (KIMPA), featuring a 330-fF shunt capacitor, demonstrate a phase-preserving amplification with a 450-MHz bandwidth at 17-dB gain, and an added noise ranging from 0.5-1.3 quanta near the center frequency of 8.4 GHz. Due to the high critical current of the NbTiN nanowire, the KIMPA also achieves a saturation power of up to -68\pm3 dBm, approximately 30-dB higher than that of JJ-based PAs. This scheme also opens new possibilities for other three-wave-mixing building blocks.

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Chih-Chiao Hung, Hiroki Kutsuma, Chung Wai Sandbo Chang, Arjan Ferdinand van Loo, Yasunobu Nakamura. 2025-04-23. Broadband Kinetic-Inductance Parametric Amplifiers with Impedance Engineering. https://arxiv.org/abs/2504.17145

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