Events at Physics
Conversely, in the nondegenerate case, gain is independent of phase. Here the pump frequency is not a multiple of the signal frequency, and it becomes necessary to consider idler tones. For the nondegenerate three-wave case, we present an intuitive picture for a parametric amplifier containing a flux-pumped SQUID where current at the signal frequency depends upon the load impedance at an idler frequency. This understanding has recently lead to the experimental realization of a SQUID parametric amplifier with strong environmental coupling, allowing for substantially increased bandwidth and dynamic range.
The use of equivalent impedances offers insights not always apparent from the Hamiltonian equations of motion. In particular, our "pumpistor" impedance models immediately provide readily testable predictions for many other circuits containing flux-pumped SQUIDs.