Tayloring non-linearity of Josephson Parametric Amplifiers using SQUID arrays

Gain, bandwidth and noise temperature (or quantum efficiency) are the most cited figures of merit of an amplifier. However when dealing with Josephson Parametric Amplifiers (JPA), it appears that non-linearity is of prime importance. Indeed this quantity imposes the strength of the pump and thus the input saturation power (characterized as the 1dB compression point) of such amplifiers. We present a new design of JPA made of an array of eighty superconducting quantum interference devices (SQUIDs), reaching close to quantum-limited amplification through a 4-wave Kerr nonlinearity. This device is a lambda/4 non-linear resonator and we present a general method to map it to an effective non-linear series LC oscillator. Our ability to tailor the Kerr nonlinearity via the number of SQUIDs in the array and thus increasing the dynamical range of the JPA permits to break the usual trade-off between bandwidth and dynamical range of the JPA. At 20dB gain, a bandwidth of 47MHz and a 1dB compression point of -110dBm are measured. A single-SQUID JPA showing the same bandwidth and resonant frequency would display a saturation power more than 10dB lower.