Samuel Wood MPhys MInstP

Abstract:

Superconducting travelling wave parametric amplifiers (TWPAs) exhibit great promise across various applications, owing to their broadband nature, quantum-limited noise performance, and high-gain operation. Whilst their construction is relatively simple, particularly for thin-film-based TWPAs, challenges such as the requirement for an extremely long transmission line, current fabrication limitations, and their sensitivity to fabrication tolerances, mean that their optimal operating conditions often differ from those anticipated during the design stage. As a result, manual fine-tuning of numerous operational parameters becomes necessary to recover optimal performance; a process that is both labour-intensive and time-consuming. This paper introduces an automated methodology designed to significantly accelerate the characterisation of a TWPA by several orders of magnitude without requiring human intervention. Additionally, we have developed metrics to condense the multitude of measured frequency responses of the TWPA, obtained in data cube form, into an easily-understandable format for further scientific interpretation. To demonstrate the efficacy and speed of our methodology, we utilise an existing NbTiN (niobium titanium nitride) TWPA as an example. This showcases the capability of our approach to unveil both broad- and fine-scale behaviours of the device, highlighting the importance of an automated experimental setup for the in-depth investigation of TWPAs for future developments.

Abstract:

Traveling wave parametric amplifiers (TWPAs) offer the most promising solution for high gain, broadband, and quantum noise limited amplification at microwave frequencies. Experimental realization of TWPAs has proved challenging with often major discrepancies between the theoretically predicted and the measured gain performance of the devices. Here, we extend the conventional modeling techniques to account for spatial variation in the surface impedance of the thin film and the parametric sum-frequency conversions effect, which subsequently results in accurate reproduction of experimental device behavior. We further show that such an analysis may be critical to ensure fabricated TWPAs can operate as designed.