Abstract: A switch is provided that introduces quasiparticles at an asymmetric location into a reduced cross-sectional area microbridge link that is part of an output path. The quasiparticles nucleate a small region of normal resistivity and the normal region propagates to produce normal resistivity in the entire reduced cross-sectional area microbridge link. The asymmetry of the location provides input-output isolation. The high critical current, high resistivity material for the reduced cross-section member provides high current and voltage gain and the small size provides high speed. In one structure, an input film conductor is asymmetrically, centrally positioned in an insulator stack and a microbridge like is positioned on a beveled side of the stack with the input conductor in tunneling relationship with part of the narrow portion of the microbridge link. Decoupling between input and output sufficient to permit one switch to drive several others is provided.

Abstract: A method for trimming the zero voltage Josephson current of a tunnel junction including the steps of measuring the I-V characteristics of the completed junctions to quantify the change in I.sub.o necessary to meet the design requirements, placing the tested Josephson junctions on a metal block which is mounted in the sample chamber of an ion implanter structure which is pumped to 1.10.sup.-6 Torr. The junctions, kept at room temperature and oriented at a direction nearly normal to the ion beam, are implanted with magnetically analyzed ions of energies 50 keV to 2300 keV. Spatial uniformity of the ion implant beam is .+-.2% over a sample. Uniform spatial implantation over a large area sample is obtained by either sweeping of the beam across the sample, or restoring the sample through a stationary beam, determining the required ion dose to effect trimming from calibration curves, remeasuring the I-V characteristics after implantation to confirm that the required I.sub.