A Clocking Strategy for Scalable and Fault-Tolerant QDCA Signal Distribution in Combinational and Sequential Devices

Abstract

A signal distribution network (SDN) for Quantum-dot Cellular Automata (QDCA) devices is described. This network allows the distribution of a set of inputs to an arbitrary number of outputs in any desired order, overcoming the challenges associated with wire crossings that have faced QDCA systems in the past. The proposed signal distribution network requires only four distinct clock signals, regardless of the number of inputs or outputs, and those clock signals each repeat a very simple pattern. This network is highly scalable, completing the distribution of N inputs to an arbitrary number of distributed signals in 4N – 2 clock cycles. The operation of this device is demonstrated by applying it to a two-input/one-output XOR gate and a three-input/two-output full adder. A modified SDN customized for use with sequential devices is also shown.