Intermodulation distortion in wideband high-power Josephson parametric amplifiers

We characterize intermodulation distortion in a wideband impedance matched Josephson parametric amplifier (JPA) with high dynamic range. We observe excess intermodulation in 2-tone experiments for inter-tone spacing smaller than 1 MHz, with anomalous dependence on tone power and spacing. We will show that the effect can be understood as arising from nonlinearity associated with saturable losses in the device dielectrics due to a bath of two-level systems (TLS). At low powers, the TLS nonlinearity dominates over the usual Kerr nonlinearity of the JPA, whereas at higher powers the two compete. This work points to intermodulation distortion measurements as a possible technique for characterizing TLS in dielectrics.