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Noise performance of lumped element direct current superconducting quantum interference device amplifiers in the 4–8 GHz range
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10.1063/1.3497008
/content/aip/journal/apl/97/14/10.1063/1.3497008
http://aip.metastore.ingenta.com/content/aip/journal/apl/97/14/10.1063/1.3497008
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Experimental layout. This shows the apparatus with the SNTJ. For the y-factor measurements, the apparatus before the directional coupler is replaced by the heated microwave termination. The transfer switch connected to amplifier by superconducting cables allows for calibrated gain measurements. Use of double isolators at both the input and output of the SQUID amplifier realistically simulates a typical quantum measurement experiment.

Image of FIG. 2.
FIG. 2.

System noise temperature as a function of frequency at a good bias point for three amplifiers with different lengths of input resonator. The left—most line is a 2 mm long input resonator, the middle line is 1.6 mm, and the right—most line is 1.4 mm. Inset shows zoomed in noise temperature as a function of frequency around the optimal noise point for the 1.6 mm amplifier. These data were taken using the y-factor method for the 1.6 mm device and the SNTJ method for the other devices, with the configuration of double circulators, directional coupler, and transfer switch shown in Fig. 1.

Image of FIG. 3.
FIG. 3.

System noise temperature in K as a function of current through the flux bias coil and signal frequency for an amplifier with a 1.4 mm resonator. Again, we see useful signal-to-noise improvement over several hundred megahertz frequency range. Also, note the strong dependence of optimal frequency, bandwidth, and minimum noise temperature on flux bias. The current bias is fixed at , which puts the SQUID in finite-voltage state.

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/content/aip/journal/apl/97/14/10.1063/1.3497008
2010-10-04
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Noise performance of lumped element direct current superconducting quantum interference device amplifiers in the 4–8 GHz range
http://aip.metastore.ingenta.com/content/aip/journal/apl/97/14/10.1063/1.3497008
10.1063/1.3497008
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