Multi-input Josephson AND gate with ladder structure

A multi-input AND gate composed of multiple stages, each with a three-junction interferometer and a single junction (ladder structure) is proposed. The number of inputs to this multi-input with multi-stage AND gate can easily be extended by systematically increasing the number of stages without decreasing the operating margin. The design and experimental results are described. Operating margins of the six-input AND gate were +or-30% (from simulation) and +or-20% (from experiment). The operating speed, simulated for 2.5- mu m-diameter junctions, was 60 ps, whereas the measured speed was 130 ps. The difference seems to be due to circuit parameter spread because the chip used for measuring the speed had large critical current deviation.<
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