We present a lumped-element Josephson parametric amplifier designed to operate with strong coupling to the environment. In this regime, we observe broadband frequency dependent amplification with multi-peaked gain profiles. We account for this behaviour using the "pumpistor" model which allows for frequency dependent variation of the external impedance. Using this understanding, we demonstrate control over gain profiles through changes in the environment impedance at a given frequency. With strong coupling to a suitable external impedance we observe a significant increase in dynamic range, and large amplification bandwidth up to 700 MHz giving near quantum-limited performance.
@article{arxiv.1401.3799,
title = {Strong environmental coupling in a Josephson parametric amplifier},
author = {Josh Mutus and Ted White and Rami Barends and Yu Chen and Zijun Chen and Ben Chiaro and Andrew Dunsworth and Evan Jeffrey and Julian Kelly and Anthony Megrant and Charles Neill and Peter O'Malley and Pedram Roushan and Daniel Sank and Amit Vainsencher and James Wenner and Kyle Sundqvist and Andrew Cleland and John Martinis},
journal= {arXiv preprint arXiv:1401.3799},
year = {2014}
}