An efficient XOR design based on NNI and five-input majority voter in quantum-dot cellular automata

As an emerging nanodevice, Quantum-dot cellular automata (QCA) is a hopeful candidate for conventional complementary metal oxide semiconductor devices. XOR, one of the most vital gates, occupies a significant positon in digital logic circuits. In order to improve the property performance of XOR, a novel five-input majority gate is put forward first. Then, an efficient XOR employing a NAND-NOR-Inverter (NNI) and the proposed five-input majority voter is realized in the paper. Compared with previous counterparts based on gates, the proposed design requires fewer cells, occupies less area, and consumes less average energy consumption. Specifically, it improves by 11.11% in cell count, 2.11% in area, and 9.51% (1.5E_k) in energy consumption when compared to the state-of-the-art design. The clock delay of the XOR in the article keeps the same with the minimum of them. Additionally, the proposed design has the lowest QCA cost, including area-delay cost, QCA-specific cost, and energy-delay cost. Moreover, the design is coplanar, without any crossing types. All these make it an outstanding design. To demonstrate its practicality, n-bit parity generators using the proposed XOR are implemented. The novel 4-bit parity generator excels in cell count, area, and average energy dissipation, achieving optimization of up to 10.6%, 6.0%, and 38.6% (0.5E_k), respectively, compared to previous optimum values. The significance of these optimization results becomes more pronounced as the bit of parity generators increases, indicating a promising future for constructing complex circuits.