Noise properties of YBaCuO step edge DC-SQUIDs with different inductance

Autonomous step edge DC-SQUIDs (superconducting quantum interference devices) with inductances between 20 pH and 140 pH have been prepared on one chip. The noise properties of these devices have been determined by operating them in the flux locked loop. The best energy sensitivity of 6*10/sup -31/ J/Hz was obtained for a 20 pH SQUID and frequencies above 100 Hz. The frequency-dependent noise for the best devices was about 2*10/sup -29/ J/Hz at 1 Hz and could be reduced by applying an AC bias.<
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