Authors: M.D. Wagh, Y. Sun, V. Annampedu
Affilation: Lehigh University, United States
Pages: 76 - 79
Keywords: quantum-dot cellular automata, architecture, comparison function
Quantum-Dot cellular automata (QCA) architectures represent the future of computing. But it can only implement an inverter and a three input majority gate directly. Consequently very few QCA architectures are available in literature. By fixing an input, one can also convert the majority gate to a 2 input AND or OR gate and thereby hope to build any required logic function. But such realizations are clearly very inefficient, both in terms of their size and speed. We present a direct and efficient QCA architecture for the comparison function. Our N bit comparison uses less than 4N three input majority gates and has an optimal O(log N) delay. We use recursion to obtain a tree-like structure which has clearly separated clocking zones. The efficiency of our architecture is due to the fact that the use of AND and OR gates, which have a poor realization in QCA technology, are limited to only the first level of the tree. Since comparison is an important component of many computations including realization of arbitrary Boolean functions, this work will have an impact in a multitude of applications.