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(a) Schematic circuit diagram of the flux-driven Josephson parametric amplifier. (b) Operation principle of the parametric amplifier. The solid curve represents the resonant frequency of the cavity. ac flux modulation induces the modulation of the resonant frequency about its static value , which leads to the parametric amplification. (c) Schematic diagram of the measurement setup. Squares with a number inside represent fixed attenuators with the corresponding attenuation in decibels. Squares with an arrow inside represent isolators.
(a) Resonant frequency as a function of the normalized magnetic flux. The inset shows the phase of the reflection coefficient as a function of the frequency in gigahertz at . (b) An intensity plot of (pump on) as a function of the signal frequency and the normalized magnetic flux. The inset shows a cross section at together with the data when the pump is off.
(a) Sideband peak measured by the spectrum analyzer. The peak is located at 10.78 GHz . The solid curve is a spectrum when the pump is on, while the dashed curve is a spectrum when the pump is off. (b) Gain as a function of the carrier phase of the signal.
Maximum gain as a function of the input signal power . For and 10.78 GHz, and 10.77 GHz, respectively. The inset shows the maximum gain as a function of the input signal frequency for .
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