A Scalable Signal Distribution Network for Quantum-Dot Cellular Automata

The authors describe a signal distribution network (SDN) for quantum-dot cellular automata (QCA) devices. This network allows the distribution of a set of inputs to an arbitrary number of combinational functions, overcoming the challenges associated with wire crossings that have faced QCA systems for many years. As an additional benefit, the proposed SDN requires only four distinct clock signals, regardless of the number of inputs or outputs, and those clock signals each repeat a very simple pattern. Furthermore, this network is highly scalable, completing the distribution of inputs to an arbitrary number of distributed signals and an arbitrary number of outputs in 4 - 2 clock cycles. To illustrate its operation, the authors apply the SDN to a two-input/one-output exclusive OR operation, a three-input/two-output full adder, and a four-input/four-output multiplier.