Cellular Automata

Modelling and simulation are disciplines of major importance for science and engineering. There is no science without models, and simulation has nowadays become a very useful tool, sometimes unavoidable, for development of both science and engineering. The main attractive feature of cellular automata is that, in spite of their conceptual simplicity which allows an easiness of implementation for computer simulation, as a detailed and complete mathematical analysis in principle, they are able to exhibit a wide variety of amazingly complex behaviour. This feature of cellular automata has attracted the researchers' attention from a wide variety of divergent fields of the exact disciplines of science and engineering, but also of the social sciences, and sometimes beyond. The collective complex behaviour of numerous systems, which emerge from the interaction of a multitude of simple individuals, is being conveniently modelled and simulated with cellular automata for very different purposes. In this book, a number of innovative applications of cellular automata models in the fields of Quantum Computing, Materials Science, Cryptography and Coding, and Robotics and Image Processing are presented

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

Reversible Quantum-Dot Cellular Automata-Based Arithmetic Logic Unit

Quantum-dot cellular automata (QCA) are a promising nanoscale computing technology that exploits the quantum mechanical tunneling of electrons between quantum dots in a cell andelectrostatic interaction between dots in neighboring cells. QCA can achieve higher speed, lowerpower, and smaller areas than conventional, complementary metal-oxide semiconductor (CMOS) technology. Developing QCA circuits in a logically and physically reversible manner can provide exceptional reductions in energy dissipation. The main challenge is to maintain reversibility down to the physical level. A crucial component of a computer’s central processing unit (CPU) is the arithmetic logic unit (ALU), which executes multiple logical and arithmetic functions on the data processed by the CPU. Current QCA ALU designs are either irreversible or logically reversible; however, they lack physical reversibility, a crucial requirement to increase energy efficiency. This paper shows a new multilayer design for a QCA ALU that can carry out 16 different operations and is both logically and physically reversible. The design is based on reversible majority gates, which are the key building blocks. We use QCA Designer-E software to simulate and evaluate energy dissipation. The proposed logically and physically reversible QCA ALU offers an improvement of 88.8% in energy efficiency. Compared to the next most efficient 16-operation QCA ALU, this ALU uses 51% fewer QCA cells and 47% less area

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

Electron Spin for Classical Information Processing: A Brief Survey of Spin-Based Logic Devices, Gates and Circuits

In electronics, information has been traditionally stored, processed and communicated using an electron's charge. This paradigm is increasingly turning out to be energy-inefficient, because movement of charge within an information-processing device invariably causes current flow and an associated dissipation. Replacing charge with the "spin" of an electron to encode information may eliminate much of this dissipation and lead to more energy-efficient "green electronics". This realization has spurred significant research in spintronic devices and circuits where spin either directly acts as the physical variable for hosting information or augments the role of charge. In this review article, we discuss and elucidate some of these ideas, and highlight their strengths and weaknesses. Many of them can potentially reduce energy dissipation significantly, but unfortunately are error-prone and unreliable. Moreover, there are serious obstacles to their technological implementation that may be difficult to overcome in the near term. This review addresses three constructs: (1) single devices or binary switches that can be constituents of Boolean logic gates for digital information processing, (2) complete gates that are capable of performing specific Boolean logic operations, and (3) combinational circuits or architectures (equivalent to many gates working in unison) that are capable of performing universal computation.Comment: Topical Revie

Implementation of multi-CLB designs using quantum-dot cellular automata

CMOS scaling is currently facing a technological barrier. Novel technologies are being proposed to keep up with the need for computation power and speed. One of the proposed ideas is the quantum-dot cellular automata (QCA) technology. QCA uses quantum mechanical effects in the device at the molecular scale. QCA systems have the potential for low power, high density, and regularity. This thesis studies QCA devices and uses those devices to build a simple field programmable gate array (FPGA). The FPGA is a combination of multiple configure logical blocks (CLBs) tiled together. Most previous work on this area has focused on fixed logic and programmable interconnect. In contrast, the work at the Rochester Institute of Technology (RIT) has designed and simulated a configurable logic block (CLB) based on look-up tables (LUTs). This thesis presents a simple FPGA that consists of multiple copies of the CLB created by the RIT group. The FPGA is configured to emulate a ripple-carry adder and a bit-serial multiplier. The latency and throughput of both functions are analyzed. We employ a multilevel approach to design specification and simulation. QCADesigner software is used for layout and simulation of an individual CLB. For the FPGA, the high-level HDLQ Verilog library is used. This hybrid approach provides a high degree of confidence in reasonable simulation time

A Novel Reconfiguration Scheme in Quantum-Dot Cellular Automata for Energy Efficient Nanocomputing

Quantum-Dot Cellular Automata (QCA) is currently being investigated as an alternative to CMOS technology. There has been extensive study on a wide range of circuits from simple logical circuits such as adders to complex circuits such as 4-bit processors. At the same time, little if any work has been done in considering the possibility of reconfiguration to reduce power in QCA devices. This work presents one of the first such efforts when considering reconfigurable QCA architectures which are expected to be both robust and power efficient. We present a new reconfiguration scheme which is highly robust and is expected to dissipate less power with respect to conventional designs. An adder design based on the reconfiguration scheme will be presented in this thesis, with a detailed power analysis and comparison with existing designs. In order to overcome the problems of routing which comes with reconfigurability, a new wire crossing mechanism is also presented as part of this thesis