Fault‐tolerant design and analysis of QCA‐based circuits

Emerging nanoscale computing structure quantum-dot cellular automata (QCA) is evolving as a possible replacement for complementary metal–oxide–semiconductor technology in near future. Being a new technology, it is prone to various types of fabrication-related faults and process variations. So, QCA-based circuits are prone to errors, and therefore pose significant reliability-related issues. Hence, there is an emerging need to design fault-tolerant QCA-based circuits to mitigate the reliability issues. This study first presents QCA-based new designs of 2-input Exclusive-OR gate and 1 bit full adder using conventional design approach without redundant QCA cells. Then, the fault tolerance has been implemented in these designs by introducing redundant QCA cells. The proposed circuits exhibit significant improvements in fault-tolerant capability against cell omission, misalignment, displacement, and extra cell deposition defects. The proposed fault-tolerant designs have been compared with existing designs in terms of generalised design metrics of QCA circuits. Energy dissipation results have been computed for the proposed fault-tolerant circuits using accurate QCAPro power estimator tool. Influence of temperature variations on the polarisation of the proposed fault-tolerant circuits has also been investigated. The functionality of the proposed circuits has been verified with QCADesigner version 2.0.3 tool.