International Journal of Computer Applications (0975 – 8887) Volume 43– No.2, April 2012 22 Quantum Cellular Automata based Novel Unit 2:1 Multiplexer Debarka Mukhopadhyay Assistant Professor Department of Computer Science and Engineering Bengal Institute of Technology and Management, Santiniketan, WB, India Paramartha Dutta Professor Department of Computer and System Sciences Visva-Bharati University Santiniketan, West Bengal, India ABSTRACT Quantum Cellular Automata (QCA) is an emerging nanotechnology and one of the top six technologies of the future. CMOS technology has a lot of limitations while scaling into a nano-level. QCA technology is a perfect replacement of CMOS technology with no such limitations. In this paper we have proposed one 2:1 multiplexer circuit having lowest complexity and area compared to the existing QCA based approaches. The proposed design is verified using QCADesigner. General Terms QCA, QCA Designer, Multiplexer. Keywords Majority Voter circuit, Minority Voter Circuit, Nanotechnology . 1. INTRODUCTION CMOS Technology is approaching its scaling limit very fast. In practical point of view this technology in nano-scales is facing lot of problems. So in order to enhance the performance of a system new nano-technology approach should be taken into account. Quantum Cellular Automata[13,14] is now one of the promising and emerging technology which not only providing a solution at nano- scale, but also offers solutions that currently CMOS technology is facing[1,2]. The basic building block of every QCA circuit is majority gate and every QCA circuit can be built using Majority and inverter gate [3].The majority logic can be implemented in a different manner from that of Boolean logic. The Boolean logic operators (like AND, OR and their complements) and other digital functions can be implemented using Majority logic [4]. The majority logic can be termed as more powerful for implementing digital functions because of very small number of logic gates [5, 6]. In this paper we propose a new design methodology for a 2:1 MUX Using this design as a unit complex MUX design is possible. In comparison to existing implementation, this method has demonstrated significant improvements. The proposed 2:1 MUX resulted in decrease in cell counts and decrease in input to output delay. The presented design is justified using QCA Designer [7] simulation results. Fig 1: (a) Basic QCA cell and binary encoding, (b) A QCA majority gate and (c) A QCA inverter. 2. DESCRIPTION AND ANALYSIS 2.1 Relevant QCA Concept This technology is built up in cells. Each cell has 2 electrons trapped on it [8,9]and 4 as illustrated in Fig1(a). The electrons can be on any island and can tunnel between the islands. However, due to Coulomb repulsion, they will always settle to one of two stable states. One configuration of charge represents a binary “1, “the other a "0,” but no current flows into or out of the cell[11,12]. The field from the charge configuration of one cell alters the charge configuration of the next cell. Remarkably, this basic device-device interaction, coupled with a clocking scheme for modulating the effective barrier between states,is sufficient to support general- purpose computing with very low power dissipation. Binary wire can be assembled where all cells in the chain have the same value. The fundamental logic gate is the Majority Gate. A majority gate takes three inputs; its output is equal to whichever two inputs agree as illustrated in Fig 1(b). Assuming three inputs labeled A, B and C, the logic function of majority gate is M(A,B,C)=AB+BC+C ………………………. (1)