Noise performance of lumped element direct current superconducting quantum interference device amplifiers in the 4–8 GHz range

摘要

We report on the noise of a lumped element direct current superconducting quantum interference device amplifier. We show that the noise temperature in the 4–8 GHz range over ranges of tens of megahertz is below 1 K (three photons of added noise), characterize the overall behavior of the noise as a function of bias parameters, and discuss potential mechanisms which determine the noise performance in this amplifier. We show that this device can provide more than a factor of 10 improvement in practical system noise over existing phase-preserving microwave measurement systems in this frequency band.