Superconducting quantum interference device with very low magnetic flux noise energy

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.