Low Noise Four-Photon Josephson Parametric Amplification

Abstract
We report the first double-sideband noise temperature measurements of a Josephson parametric amplifier. The 9 GHz amplifier consists of an LC-resonant tunnel junction coupled to a low impedance transformer. TDSB=4.5±3K and GDSB=+13dB was measured in the externally pumped four photon mode with an instantaneous bandwidth of 290 MHz. Room temperature noise was reduced to a low level by a cryogenic circulator and a cooled 20 dB attenuator. The noise temperature measurements were made via a “hot/cold” technique with input temperatures close to the bath temperature.

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