Abstract: In superconductive circuitry including a superconducting ground plane, a magnetic flux trapping moat is provided which surrounds a superconductive device. The moat is preferably a cut through the superconducting ground plane which extends along a perimeter surrounding the superconducting device, the moat being continuous except for small regions where there is no cut. The small regions serve as current carrying portions to link the ground plane within the moat to the rest of the ground plane outside of the moat. The moat is a flux pinning center so that magnetic flux does not enter the ground plane region located near the superconducting device. In a Josephson circuit, the Josephson tunnel devices are especially sensitive to trapped magnetic flux in the ground plane, and the provision of a moat around each of the devices prevents flux from moving into the ground plane areas near the devices and becoming trapped therein.