Josephson parametric converter saturation and higher order effects

Understand

Microwave parametric amplifiers based on Josephson junctions have become a key component of many quantum information experiments.

• One key limitation which has not been well predicted by theory is the gain saturation behavior which determines its ability to process large amplitude signals.
• The typical explanation for this behavior in phase-preserving amplifiers based on three-wave mixing is pump depletion, in which the consumption of pump photons to produce amplification results in a reduction in gain.
• However, in this work we present experimental data and theoretical calculations showing that the fourth-order Kerr nonlinearities inherent in the Josephson junctions are the dominant factor in the Josephson Parametric Converter (JPC).