Engineering the nonlinearity of a SNAIL parametric amplifier to achieve higher dynamic range: part 2

Quantum-limited Josephson parametric amplifiers are an important component for most superconducting qubit readout methods. Although the basic theoretical model that describes such amplifiers is very general, the exact physical realization may rely on using different types of nonlinearity for mixing. Pure three-wave mixing amplifiers use 3rd order nonlinearity for the mixing leading to amplification, while keeping away harmful 4th order Kerr nonlinearity that limits the dynamic range of the amplifier. We present a degenerate amplifier based on an array of SNAILs (Superconducting Nonlinear Asymmetric Inductive Elements),in which the 3rd and 4th order nonlinearities can be separately adjusted in order to optimize the amplifier performance. In particular, this SNAIL parametric amplifier can be flux-tuned to a Kerr-free point while still possessing third order nonlinearity. In part 2, we report the observation of an increase in the saturation power at the Kerr-free operating point of the device and provide design guidelines for optimizing a general pumped mixing process.