Towards reversible QCA computers: Reversible gates and ALU

This work presents a novel implementation of reversible gates and reversible ALU, all based in quantum-dot cellular automata (QCA). QCA has been considered as an alternative for field-effect transistors due to its quite small size (nanometers), ultra-low power consumption and clock rate (terahertz range). On the other hand, reversible computation is a new paradigm where all logic operations can be performed in an invertible way. This feature is important to different technologies, such as quantum computing, adiabatic circuits, low power computation, etc. Regarding low power consumption, QCA has been seen as a promising technology for approaching the thermodynamic limit of computation and this work focus on designing a QCA reversible ALU in order to go beyond that limit, bridging the gap between QCA technology and reversible components. In a bottom-up approach, we first discuss QCA reversible gates and a few design choices. We also present the ALU´s QCA design, demonstrate the functionality, test and validate the proposed architecture using QCADesigner simulator. Due to the importance of these new computational paradigms, this study is central in consolidating possible emerging technologies.