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Applied Physics Letters

Superconducting quantum interference device with very low magnetic flux noise energy

Dale J. Van Harlingen, R. H. Koch, John L. Clarke

Published Jul 15, 1982• 67 citations
Publisher

Abstract

We have fabricated dc superconducting quantum interference devices incorporating Josephson tunnel junctions with an inductance of about 2 pH and a capacitance per junction of about 0.3 pF. The lowest measured flux noise energy was 3.2 h/ at 1.4 K at a frequency of 202 kHz. When the 1/f noise was subtracted, the white noise energy decreased from around 3h/ at 4.2 K to below 2h/ at 1.4 K.

DOI
10.1063/1.93460

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We have fabricated dc superconducting quantum interference devices incorporating Josephson tunnel junctions with an inductance of about 2 pH and a capacitance per junction of about 0.3 pF. The lowest measured flux noise energy was 3.2 h/ at 1.4 K at a frequency of 202 kHz. When the 1/f noise was subtracted, the white noise energy decreased from around 3h/ at 4.2 K to below 2h/ at 1.4 K.
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We present the results of an investigation of thin-film dc super conducting quantum interference device (SQUID’s) with very high energy resolution. The SQUID’s were fabricated using integrated-circuit techniques appropriate for superconducting devices. A weakly coupled SQUID with very low inductance (1 pH) had an intrinsic energy sensitivity 6×10−34 J/Hz = 0.9 h. A well-coupled SQUID (coupling constant α = 0.43) had an energy sensitivity referred to the input coil of 4.7×10−32 J/Hz = 71 h.
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