Novel ultra-energy-efficient reversible designs of sequential logic quantum-dot cellular automata flip-flop circuits

The version of record of this article, first published in [The Journal of Supercomputing], is available online at Publisher’s website: http://dx.doi.org/10.1007/s11227-023-05134-1Quantum-dot cellular automata (QCA) is a technological approach to implement digital circuits with exceptionally high integration density, high switching frequency, and low energy dissipation. QCA circuits are a potential solution to the energy dissipation issues created by shrinking microprocessors with ultra-high integration densities. Current QCA circuit designs are irreversible, yet reversible circuits are known to increase energy efficiency. Thus, the development of reversible QCA circuits will further reduce energy dissipation. This paper presents novel reversible and irreversible sequential QCA set/reset (SR), data (D), Jack Kilby (JK), and toggle (T) flip-flop designs based on the majority gate that utilizes the universal, standard, and efficient (USE) clocking scheme, which allows the implementation of feedback paths and easy routing for sequential QCA-based circuits. The simulation results confirm that the proposed reversible QCA USE sequential flip-flop circuits exhibit energy dissipation less than the Landauer energy limit. Irreversible QCA USE flip-flop designs, although having higher energy dissipation, sometimes have floorplan areas and delay times less than those of reversible designs; therefore, they are also explored. The trade-offs between the energy dissipation versus the area cost and delay time for the reversible and irreversible QCA circuits are examined comprehensively

Quantum-Dot Cellular Automata Circuits With Reduced External Fixed Inputs

Nanotechnologies, notably quantum-dot cellular automata, have achieved world-wide attentions for their prominent features as compared to the conventional CMOS circuitry. Quantum-dot cellular automata, particularly owning to its considerable reduction in size, energy consumption and latency of circuits, is considered as a potential alternative for the CMOS technology. Considering the manufacturing aspects, in this paper, a method is proposed for designing efficient quantum-dot cellular automata circuits. We inspect an alternative approach for streamlined design of quantum-dot cellular automata circuits such that the required external fixed inputs are substantially reduced. In order to demonstrate the efficiency of the proposed method, the widely used multiplexer, XOR and party generator circuits are considered as case studies. All of the proposed circuits are simulated and verified using QCADesigner which is a valid and popular simulation tool. Comparisons indicate that the proposed method considerably reduces the number of external fixed inputs which simplifies the overall circuit implementation and fabrication