Quasi-static operation of Josephson Atto - Weber switches (JAWS) fabricated using the selective niobium anodization process (SNAP)

Recent measurements of Nb-aSi-Nb Josephson tunnel junctions fabritated using SNAP have demonstrated that this technique is a possible alternative to the Pb alloy technology. In the present work, the results of quasi-static measurements are reported on the first logic gates made using SNAP. The basic gate consists of a JAWS with both junctions having the same critical current. Operating margins in terms of the bias, off-set, and input currents are presented for individual gates and for series strings of gates having fanouts of 1 and 2. Whereas the use of an offset current substantially increases the margin of an individual gate, the increase in margin for a string is considerably less. The data are described well by a simple model taking into account the leakage current in the actual gates, and demonstrate the potential utility of SNAP.