Deconstructing the Traveling Wave Parametric Amplifier

Traveling wave parametric amplifiers (TWPAs) play a prominent role in modern superconducting quantum computing efforts. They are valued for their relatively high power handling capability, bandwidth, and simple operation. However, the core mechanism for producing gain in these systems is based on very long nonlinear transmission lines that can be difficult to engineer for ideal behavior and require additional bulky passive components to adequately isolate quantum circuits. In this article, we describe our attempt to distill the core principle of traveling wave amplifier operation and discuss prospects for extending this approach to building much smaller discrete circuits that possess some of the advantageous properties of TWPAs, specifically directional gain with a simple pumping scheme.