Flux-driven Josephson traveling-wave parametric amplifier.

We have developed a concept for a traveling-wave parametric amplifier driven by a magnetic-flux wave. The circuit consists of a serial array of symmetric DC SQUIDs coupled inductively to a separate superconducting LC-transmission line carrying the pump wave; thereby the signal and pump are applied to different ports. The advantage of the proposed flux-driven circuit with three-wave mixing includes, firstly, an adjustable phase velocity of the signal/idler microwave and, hence, good phase matching yielding large gain in a wide frequency range and, secondly, overcoming of the pump depletion problem. The experimental parameters and characteristics of this amplifier have been evaluated and show promise for applications in quantum information single-photon circuits.