Universal programmable logic gate based on quantum-dot cellular automata for enhancing reliability and efficiency of digital systems

As quantum-dot cellular automata (QCA) is gaining attention as a next-generation circuit technology, various logic circuits using QCA are being developed. The performance of digital logic circuits depends on the performance of basic logic gates, and the development of efficient universal gates improves the reliability and efficiency of digital systems by reducing the types of basic logic gates. This study proposes an efficient QCA-based universal programmable logic (UPL) gate that can perform not only NAND and NOR, which are well-known as universal gates, but also XOR and XNOR, which have complex structures of 2-level logic gates, with a single gate. A variety of combinational logic circuits are designed using the proposed UPL gate, and it is demonstrated that it operates as a universal gate and is scalable. Furthermore, the average output polarization is highly stable, exceeding 9.5, and it demonstrates a significant 44% improvement in design cost compared to the best existing QCA-based universal gate. These efforts ultimately lead to the simplification of the design and process of digital systems, which reduces the number of points of failure and reduces the manufacturing cost.