**Abstract**

Recently, Low power and reduced heat dissipation are an increasing demand for digital systems. Quantum Dot Cellular Automata (QCA) is a future generation solution based on nanotechnology for the digital systems. The QCA systems have advantages like the small size, ultralow power consumption and high switching frequency. The present research aims at introducing a novel three-input XOR gate containing 12 cells. The energy dissipation analysis of the proposed gate is verified using three different energy levels ( γ= γ= 0.5E , 1.0, E k k and <sup>κ</sup> γ= Ε 1.5 ) at T = 2 Kelvin temperature. Simulation is performed for the proposed gate using QCA Designer tool version 2.0.3. The proposed three-input XOR gate has less number of cells, area and energy dissipation as compared to the previous structures.

**Keywords:** nanotechnology, circuit design, quantum-dot cellular automata (QCA), three-input XOR gate

### **1. Introduction**

The state of the art very large scale integrated circuits (VLSI) technology limits to doping fluctuations and high leakage current [1]. On one side, scaling down of CMOS technology has led to grave challenges in context of power consumption, physical dimensions, and leakage current. These short falls have guided to significant efforts to look for suitable substitutes. On the other side, emerging nanotechnologies seems to be better choice for the future generation digital systems [2, 3]. Thereby, quantum computers promise dramatic improvements in our ability to efficiently solve classically intractable problems ranging from cryptosystems to simulation of quantum systems. Quantum computing has attracted attention in the past two decades because it was found that computers exploiting quantum mechanics are able to outperform classical digital computers in certain areas like factoring integers and searching. Developments in the field of quantum computing have been strongly impacted by the paradigm of quantum-dot cellular automata (QCA), in which information is transmitted and processed through electrostatic interactions in an array of cells. QCA is one of the most significant computing technologies for the future. It will be the alternative candidate for CMOS technology that currently used in integrated circuits (ICs) [2, 3]. The logic function of QCA technology is to

implement circuits using movement of electrons rather than voltage level [3–6]. In fact, QCA technology is anticipated to offer higher density and lower power consumption and more flexible interconnection designs for future System on Chip (SoC). On the other hand, a number of QCA based digital devices have studied to date; designs of XOR gate, full adder, multipliers, dividers, memory circuits, counter QCA based memory cells, flip flops, and multiplexer [7–15]. Among theme, XOR gates are extensively employed in communication systems. So, there is emerging need to develop methods which involve less area and delay overheads to improve the complexity of digital circuits. With this motive, we have proposed a novel design of QCA based three-input XOR gate. The proposed gate has significant improvement compared to others design prestened in the literature.
