Single-flux-quantum logic circuits exploiting collision-based fusion gates

We propose a single-flux-quantum (SFQ) logic circuit based on the fusion computing systems-collision based and reaction-diffusion fusion computers. A fusion computing system consists of regularly arrayed unit cells (fusion gates), where each unit has two input arms and two output arms and is connected to its neighboring cells with the arms. We designed functional SFQ circuits that implemented the fusion computation. The unit cell was able to be made with ten Josephson junctions. Circuit simulation with standard Nb/Al-AlOx/Nb 2.5-kA/cm(2) process parameters showed that the SFQ fusion computing systems could operate at 10 GHz clock. (c) 2008 Elsevier B.V. All rights reserved.