Quantum Dot Cellular Automata (QCA) is a newly developed paradigm for digital design, which holds the potential as possible alternative to the present Complementary Metal Oxide Semi‐Conductor (CMOS) technology. After surviving for nearly five decades, the scaling of CMOS is finally reaching its limits. The asperities are not only seen from the physical and technological viewpoint but also from the material and economical perspectives. With no more scaling possible, there is a need to look for promising alternatives to continue with the nano size/scale computations and to hold on to the Moore’s law. QCA offers a breakthrough required for the fulfilment of certain lacking aspects of CMOS technology in the nano regime. QCA is a technology that involves no current transfer but works on electronic interaction between the cells. The QCA cell basically consists of quantum dots or metal islands separated by certain distance and the entire transmission of information occurs via the interaction between the electrons localized in the potential wells. Since the technology is new and in a premature phase, a huge scope lies ahead of the researchers to investigate and make QCA design a reality. In this paper the QCA technology is reviewed with sufficient focus on basic concepts, implementations and information flow. The various building blocks in QCA are discussed and their working on the basis of physical laws is explained. This paper forms
the basis for further complex digital designing in QCA.
