Strong environmental coupling in a Josephson parametric amplifier.

Authors :: Mutus, J. Y.
White, T. C.
Barends, R.
Yu Chen
Chen, Z.
Chiaro, B.
Dunsworth, A.
Jeffrey, E.
Kelly, J.
Megrant, A.
Neill, C.
O'Malley, P. J. J.
Roushan, P.
Sank, D.
Vainsencher, A.
Wenner, J.
Sundqvist, K. M.
Cleland, A. N.
Martinis, John M.
Source :: Applied Physics Letters. 6/30/2014, Vol. 104 Issue 26, p1-4. 4p. 1 Diagram, 2 Graphs.
Publication Year :: 2014
Abstract: 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 behavior using the "pumpistor" model which allows for frequency dependent variation of the external impedance. Using this understanding, we demonstrate control over the complexity of gain profiles through added variation 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. [ABSTRACT FROM AUTHOR]