A robust wire crossing design for thermostability and fault tolerance in quantum–dot cellular automata

Abstract

Quantum-dot cellular automata (QCA) present an unconventional computing model in the nanometer regime. The applications in QCA require complex wire crossings between intersectional wires. The existing wire crossing schemes show low fault tolerance or thermal instability. In this paper, a robust wire crossing scheme is proposed by using two opposite clock zones and redundant cells. The thermostability and fault tolerance are illustrated by using statistical analysis and fault simulations with regard to cell undeposition. This paper also presents a new signal distribution network (SDN) using the proposed wire crossings. The layouts of an XOR gate and a full adder are investigated to show the scalability of the proposed designs to circuits for logic functions with various number of inputs. For the proposed wire crossing and SDN, the circuitries of metal wires to provide the electric fields for driving the involved cells in each clock zone are also discussed. The functionalities of these circuits are validated by using QCADesigner.