Towards the bottom-up concept: Extended quantum-dot cellular automata

In this article we present an extended quantum-dot cellular automaton (QCA) cell. The classical QCA cell is extended in the sense of an enlarged range of its possible stable and usable states. Indeed, in the classical QCA cell the electrons, owing to electrostatic repulsion, align along one of the two diagonal configurations that correspond to their maximal spatial separation. The QCA cell thus has the ability to encode two states - two logic values (0 and 1). By extending the QCA cell with four additional quantum dots, we introduce the extended QCA (EQCA) cell and analyze its behavior, the analysis of which is based on the semi-classical modeling approach. Experiments showed that by using a special interpretation of electron configurations in the EQCA, the range of possible states can be increased from two to three, giving the EQCA cell the ability to encode the logic values (0, 1/2 and 1). The primary motive of this article is to promote the idea of finally switching focus from pure miniaturization and the top-down concept to the bottom-up concept and start extending the currently available approaches to allow for 'richer' processing and data storage capabilities without a major increase in space requirements. (c) 2006 Elsevier B.V. All rights reserved.