NbN- and NbTiN-base Kinetic Inductance Traveling-Wave Parametric Amplifiers (KITWPAs) for Quantum Information Circuits

Chun-Lun Wang^1*, Hsiao-Wen Chang¹, Jen-Chieh Cheng¹, Ta-Shun Wei¹, Chuang-Pin Chiu¹, Yen-Pin Chang¹, Tse-Jun Chen¹, Po-Wei Huang², Jeng-Chung Chen², Chao-Te Li¹, Ming-Jye Wang¹

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Department of physics, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Chun-Lun Wang, email:clwang@asiaa.sinica.edu.tw

We present our current progress on developing kinetic inductance traveling-wave parametric amplifiers (KITWPAs) for quantum information circuits. The devices are made of niobium nitride (NbN) or niobium-titanium nitride (NbTiN) superconducting ultrathin film, consisting of periodically loaded coplanar waveguides (CPWs) on silicon substrates. NbN and NbTiN thin film are 10 nm and 17 nm thick, respectively, DC magnetron sputtered on high resistivity silicon wafer with a 25 nm aluminum nitride buffer layer. Ultrathin films were characterized by SEM and HRTEM. The electrical properties and penetration depths of the thin film are determined by DC and RF measurements to the devices. The critical temperature (T_C) and penetration depth of NbN on device are 10.8 K and 670 nm, respectively, while those of the NbTiN device are 9.1 K and 430 nm. When measured in a 25 mK dilution refrigerator, the NbTiN device has the first stop band at 6.83 GHz, and the signal amplification was discovered at frequencies from 4.0 to 5.5 GHz when driven by the pump tone near -3dBm at the stop band. It has achieved the maximum gain near 5 dB at 3.7 GHz and has at least 1.7 GHz bandwidth. It shows three-wave mixing behavior as the pump frequency ω_p is nearly twice the signal frequency, ω_s.

Keywords: KITWPA, NbN, NbTiN, Three-wave mixing, Quantum information