Signal amplification and signal to noise ratio improvements in thermally switching SQUIDs

The response of the circulating screening current to applied magnetic flux in a variety of DC SQUIDs has been studied in a regime in which thermal noise induces rapid switching between the internal flux states of the SQUID. We observe an unexpected jump of 10 dB to 25 dB in the amplitude and signal...

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Bibliographic Details
Published in:Applied superconductivity 1999, Vol.6 (10), p.495-499
Main Authors: Hibbs, Andrew D, Whitecotton, Brian R
Format: Article
Language:English
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Summary:The response of the circulating screening current to applied magnetic flux in a variety of DC SQUIDs has been studied in a regime in which thermal noise induces rapid switching between the internal flux states of the SQUID. We observe an unexpected jump of 10 dB to 25 dB in the amplitude and signal to noise ratio (SNR) at the output of the SQUID in response to input signals of frequency below the knee of the switching spectrum. The magnitude of the gain in SNR has been measured as a function of both barrier height and energy difference between local minima of the SQUID energy potential revealing new features of SQUID behavior. A new analysis is put forth for the DC SQUID which is able to reproduce the key features of these observations.
ISSN:0964-1807
1879-1530
DOI:10.1016/S0964-1807(99)00002-2