PURPOSE:To eliminate the influence of the background magnetic fields in directions vertical and horizontal to a grounding plane as well as of a trap magnetic flux by connecting the first and second superconductive thin films of the U-shape electrically by at least two Josephson junctions through an insulator with those overlapped. CONSTITUTION:The first and second superconductive thin films 1 and 2 having the U-shape are overlapped each other through an insulator 3 and are connected electrically by at least two Josephson junctions 5. If there is a superconductive grounding plane 9 having a sufficiently large extent compared with a superconductive loop 6, a distribution in local spots of an external magnetic field in the vicinity of an interferometer loopis nearly uniform and it ranges over the internal plane of the superconductive loop vertical to unit vectors n2, n3, and n4. As the unit vectors n2 and n4 are opposite, the external magnetic flux becomes approximately zero under condition that a magnetic field vector B penetrating the interferometer is nearly equal locally. Accordingly, the operation of this superconductive quantum interferometer gate is not influenced by the existence of the background magnetic field of vertical and horizontal directions to the grounding plane which is independent of a trap, as well as of a trap magnetic flux.
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