Quasi-phasematching in a Josephson traveling-wave parametric amplifier. Additional information

Recently, the traveling-waves parametric amplifiers based on the superconducting transmission lines including Josephson junctions are extensively developed. Due to high signal gain, wide bandwidth, low losses, and potentially quantum-limited performance these devices become extremely useful tools in the field of quantum technology. However, in order to achieve ultimate characteristics, careful phase-matching of interacting microwaves should be done in these amplifiers. One of the ways to improve performance of the Josephson traveling-wave parametric amplifies with three-wave mixing is implementation of the quasi-phasematching (QPM) concept (see A. B. Zorin, https://arxiv.org/abs/2101.11697), which has been widely used in the field of nonlinear optics since the 90s. The material presents additional information to the above preprint including the nonlinear wave equation, the set of coupled mode equations (CMEs), the method of digitizing the QPM profiles (with attached dataset for the tapered meander shape), and the self-written QBASIC code for solving the CMEs