Design and Simulation of Reversible Time-Synchronized Quantum-Dot Cellular Automata Combinational Logic Circuits with Ultralow Energy Dissipation

Abstract

The quantum-dot cellular automata (QCA) represent emerging nanotechnology that is poised to supersede the current complementary metal-oxide-semiconductor digital integrated circuit technology. QCA constitutes an extremely promising transistor-less paradigm that can be downscaled to the molecular level, thereby facilitating tera-scale device integration and extremely low energy dissipation. Reversible QCA circuits, which have reversibility sustained down from the logical level to the physical level, can execute computing operations dissipating less energy than the Landauer energy limit (kBTln2). Time synchronization of logic gates is an essential additional requirement, especially in cases involving complex circuits, for ensuring accurate computational results. This paper reports the design and simulation of eight new both logically and physically reversible time-synchronized QCA combinational logic circuits. The new circuit design presented here mitigates the clock delay problems, which are caused by the non-synchronization of logic gate information, via the use of an inherently more symmetric circuit configuration. The simulation results confirm the behaviour of the proposed reversible time-synchronized QCA combinational logic circuits which exhibit ultralow energy dissipation and simultaneously provide accurate computational results.