Design of Power-Efficient Structures of the CAM Cell using a New Approach in QCA Nanoelectronics Technology

Quantum-dot Cellular Automata (QCA) is a new emerging nano-electronic technology. Owing to its many fa-vorable features such as low energy requirements, high speed, and small size, QCA is being actively suggested as a future CMOS replacement by researchers. Many digital circuits have been introduced in QCA technology, most of them aiming to reach the function with optimum construction in terms of area, cell count and power consumption. The memory circuit is the main building block in the digital system therefore the researchers paid attention to design the memory cells with minimum requirements. In this paper, a new methodology is intro-duced to design two forms of CAM cell. The proposed designs required two 2:1 multiplexers, one OR gate and one inverter. The first proposed design reduces the power consumption by 53.3%, 35% and 25.9% at (0.5 Ek, 1 Ek, and 1.5 Ek) while the second design by 53.2%, 31.9% and 20.5% (0.5 Ek, 1 Ek, and 1.5 Ek) respectively

Ab initio Molecular Dynamics Simulations of Field-Coupled Nanocomputing Molecules

Molecular Field-Coupled Nanocomputing (FCN) represents one of the most promising solutions to overcome the issues introduced by CMOS scaling. It encodes the information in the molecule charge distribution and propagates it through electrostatic intermolecular interaction. The need for charge transport is overcome, hugely reducing power dissipation. At the current state-of-the-art, the analysis of molecular FCN is mostly based on quantum mechanics techniques, or ab initio evaluated transcharacteristics. In all the cases, studies mainly consider the position of charges/atoms to be fixed. In a realistic situation, the position of atoms, thus the geometry, is subjected to molecular vibrations. In this work, we analyse the impact of molecular vibrations on the charge distribution of the 1,4-diallyl butane. We employ Ab Initio Molecular Dynamics to provide qualitative and quantitative results which describe the effects of temperature and electric fields on molecule charge distribution, taking into account the effects of molecular vibrations. The molecules are studied at near-absolute zero, cryogenic and ambient temperature conditions, showing promising results which proceed towards the assessment of the molecular FCN technology as a possible candidate for future low-power digital electronics. From a modelling perspective, the diallyl butane demonstrates good robustness against molecular vibrations, further confirming the possibility to use static transcharacteristics to analyse molecular circuits

SYNTHESIS OF COMPOSITE LOGIC GATE IN QCA EMBEDDING UNDERLYING REGULAR CLOCKING

Quantum-dot Cellular Automata (QCA) has emerged as one of the alternative technologies for current CMOS technology. It has the advantage of computing at a faster speed, consuming lower power, and work at Nano- Scale. Besides these advantages, QCA logic is limited to its primitive gates, majority voter and inverter only, results in limitation of cost-efficient logic circuit realization. Numerous designs have been proposed to realize various intricate logic gates in QCA at the penalty of non-uniform clocking and improper layout. This paper proposes a Composite Gate (CG) in QCA, which realizes all the essential digital logic gates such as AND, NAND, Inverter, OR, NOR, and exclusive gates like XOR and XNOR. Reportedly, the proposed design is the first of its kind to generate all basic logic in a single unit. The most striking feature of this work is the augmentation of the underlying clocking circuit with the logic block, making it a more realistic circuit. The Reliable, Efficient, and Scalable (RES) underlying regular clocking scheme is utilized to enhance the proposed design’s scalability and efficiency. The relevance of the proposed design is best cited with coplanar implementation of 2-input symmetric functions, achieving 33% gain in gate count and without any garbage output. The evaluation and analysis of dissipated energy for both the design have been carried out. The end product is verified using the QCADesigner2.0.3 simulator, and QCAPro is employed for the study of power dissipation

Quantum-dot Cellular Automata: Review Paper

Quantum-dot Cellular Automata (QCA) is one of the most important discoveries that will be the successful alternative for CMOS technology in the near future. An important feature of this technique, which has attracted the attention of many researchers, is that it is characterized by its low energy consumption, high speed and small size compared with CMOS.  Inverter and majority gate are the basic building blocks for QCA circuits where it can design the most logical circuit using these gates with help of QCA wire. Due to the lack of availability of review papers, this paper will be a destination for many people who are interested in the QCA field and to know how it works and why it had taken lots of attention recentl

SCERPA: a Self-Consistent Algorithm for the Evaluation of the Information Propagation in Molecular Field-Coupled Nanocomputing

Among the emerging technologies that are intended to outperform the current CMOS technology, the field-coupled nanocomputing (FCN) paradigm is one of the most promising. The molecular quantum-dot cellular automata (MQCA) has been proposed as possible FCN implementation for the expected very high device density and possible room temperature operations. The digital computation is performed via electrostatic interactions among nearby molecular cells, without the need for charge transport, extremely reducing the power dissipation. Due to the lack of mature analysis and design methods, especially from an electronics standpoint, few attempts have been made to study the behavior of logic circuits based on real molecules, and this reduces the design capability. In this article, we propose a novel algorithm, named self-consistent electrostatic potential algorithm (SCERPA), dedicated to the analysis of molecular FCN circuits. The algorithm evaluates the interaction among all molecules in the system using an iterative procedure. It exploits two optimizations modes named Interaction Radius and Active Region which reduce the computational cost of the evaluation, enabling SCERPA to support the simulation of complex molecular FCN circuits and to characterize consequentially the technology potentials. The proposed algorithm fulfills the need for modeling the molecular structures as electronic devices and provides important quantitative results to analyze the information propagation, motivating and supporting further research regarding molecular FCN circuits and eventual prototype fabrication

Designing memory cells with a novel approaches based on a new multiplexer in QCA Technology

Transistor-based CMOS technology has many drawbacks such that it cannot continue to follow the scaling of Moore’s law in the near future. These drawbacks lead researchers to think about alternatives. Quantum-dot Cellular Automata (QCA) is a nanotechnology that has unique features in terms of size and power consumption. QCA has the ability to represent binary numbers by electrons configuration. The memory circuit is a very important part of the digital system. In QCA technology, there are many approaches presented to accomplish memory cells in both RAM and CAM types. CAM is a type of memory used in high-speed applications. In this thesis, novel approaches to design memory cells are proposed. The proposed approaches are based on a 2:1 multiplexer. Using the proposed approach of RAM cell, a singular form of RAM cell (SFRAMC) is accomplished. In QCA technology, researchers strive to design electronic circuits with an emphasis on minimizing important metrics such as cell count, area, delay, cost and power consumption. The SFRAMC demonstrated significant improvements, with a reduction cell count, occupied area and power consumption by 25%, 24% and 36%. In terms of implementation cost, the SFRAMC saves 43% of the cost when compared to the previous best design. On the other hand, by using the proposed approach of CAM cell, two different structures of the QCA-CAM cell have been introduced. The first proposed CAM cell (FPCAMC) gives improvements in terms of cell count, and delay by 15% and 17% respectively. The second proposed CAM cell (SPCAMC) gives improvements in terms of cell count, and delay by 6% and 17% respectively. In terms of total power consumption, both FPCAMC and SPCAMC have an improvement of about 53% over the best-reported design. The above features of the proposed memory cells (RAM and CAM) could pave the road for designing energy-efficient and cost-efficient memory circuits in the future

QCAPro: an error-power estimation tool for QCA circuit design

In this work we present a novel probabilistic modeling tool (QCAPro) to estimate polarization error and non- adiabatic switching power loss in Quantum-dot Cellular Automata (QCA) circuits. The tool uses a fast approximation based technique to estimate highly erroneous cells in QCA circuit design. QCAPro also provides an estimate of power loss in a QCA circuit for clocks with sharp transitions, which result in non-adiabatic operations and provides an upper bound of power expended. QCAPro can be used to estimate average power loss, maximum and minimum power loss in a QCA circuit during an input switching operation. This work will provide a good platform for researchers who wish to study polarization error and power dissipation related issues in QCA circuits