Novel Ultra-Energy-Efficient Reversible Designs of Sequential Logic Quantum-Dot Cellular Automata Flip-Flop Circuits

Abstract

Quantum-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-higher integration densities. Current QCA circuit designs are nonreversible, 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 nonreversible 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. Nonreversible 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 nonreversible QCA circuits are examined comprehensively.

Hybrid Quantum-Dot Cellular Automata Nanocomputing Circuits

“…QCADesigner-E 2.2 uses a microscopic quantum mechanical model of tunnelling inside a QCA cell, along with the intra-and intercell electrostatic interactions, and a density matrix description of energy dissipation within a phenomenological model [30]. Our earlier paper [17] provides more details on the energy dissipation treatment within the quantum mechanical coherence vector formalism for the density matrix.…”

“…Theoretically, reversible computing operations, in which reversibility is maintained from the logic synthesis level down to the physical layout level, result in no information loss and consequently zero energy dissipation into the environment [13]. Several studies have simulated QCA digital circuits with extremely low energy dissipation by utilising logically and physically reversible design techniques [14][15][16][17][18]. These reversible design techniques use reversible majority gates, which recycle the input signals, as the main building blocks.…”

Reversible Quantum-Dot Cellular Automata-Based Arithmetic Logic Unit

“…The results showed that combinational QCA circuits that are both logically and www.videleaf.com physically reversible can operate with energy dissipation values lower than Landauer's limit. Later, researchers implemented this technique to develop more sophisticated combinational QCA logic circuits, as well as sequential QCA circuits, characterized by feedback loops [21,22]. In this research, we introduce the first multilayer reversible QCA ALU built using the logically and physically reversible QCA design technique.…”