Quantum-dot Cellular Automata Circuits Research Articles

A review on regular clocking scheme in quantum dot cellular automata

Quantum-dot cellular automata (QCA) is a novel and emerging nanotechnology that explores the potential of using quantum dots as information carriers in computing devices. The information transfer, as well as timing synchronization of the QCA circuit, is controlled by clocks. Despite this, most of the work done in QCA does not consider the proper layout of the underlying clocking circuit required. Hence, it ends up with QCA circuits with irregular clock zones, which is not suitable for fabrication. However, for efficient design and to provide proper routing options within the clock zones, a regular, scalable clocking scheme is needed. Without a well-defined and regular clocking zone, the QCA circuit designs are incomplete and not a standard fabrication candidate. In this regard, several regular clocking schemes in QCA are discussed in the literature. In this survey, a systematic review of those clocking schemes will be investigated. A detailed comparison of these schemes is also discussed based on design architecture and fabrication point of view.

An Efficient Design of 2-BIT Arithmetic Logical Unit in Quantum Dot Cellular Automata

For the past two decades, CMOS technology has reigned supreme in the world of Very Large Scale Integration (VLSI). But Quantum Dot Cellular Automata (QCA) is stepping into the spotlight, offering a fresh solution to the growing challenges of CMOS. This paper delves into the potential of QCA circuits by presenting a 2-bit Arithmetic Logic Unit (ALU) crafted with this groundbreaking technology, while also benchmarking it against conventional CMOS designs. The proposed QCA-based ALU delivers a trifecta of benefits: streamlined circuit design, exceptional space efficiency, and reduced quantum cost—all while keeping performance sharp in terms of latency and area usage. This 2-bit ALU encompasses a suite of operations: addition, subtraction, multiplication, division, bitwise AND, OR, XOR, and XNOR. QCA technology addresses some of CMOS's major pain points, like slow switching speeds, and doesn't require additional power sources, making it both efficient and environmentally friendly. This is not just an incremental improvement; it's a bold leap into the future of circuit design

An Ultra-Energy-Efficient Reversible Quantum-Dot Cellular Automata 8:1 Multiplexer Circuit

Energy efficiency considerations in terms of reduced power dissipation are a significant issue in the design of digital circuits for very large-scale integration (VLSI) systems. Quantum-dot cellular automata (QCA) is an emerging ultralow power dissipation approach, distinct from traditional, complementary metal-oxide semiconductor (CMOS) technology, for building digital computing circuits. Developing fully reversible QCA circuits has the potential to significantly reduce energy dissipation. Multiplexers are fundamental elements in the construction of useful digital circuits. In this paper, a novel, multilayer, fully reversible QCA 8:1 multiplexer circuit with ultralow energy dissipation is introduced. The power dissipation of the proposed multiplexer is simulated using the QCADesigner-E version 2.2 tool, describing the microscopic physical mechanisms underlying the QCA operation. The results show that the proposed reversible QCA 8:1 multiplexer consumes 89% less energy than the most energy-efficient 8:1 multiplexer circuit previously presented in the literature.

Notice of Violation of IEEE Publication Principles: Design of Cost Efficient Modular Digital QCA Circuits using Optimized XOR Gate

Notice of Violation of IEEE Publication Principles “Design of Cost Efficient Modular Digital QCA Circuits using Optimized XOR Gate” by Suhaib Ahmed and Syed Farah Naz in IEEE Transactions on Circuits and Systems II: Express Briefs After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. This paper contains significant portions of original text from the paper cited below. The original text was copied without attribution (including appropriate references to the original author(s) and/or paper title) and without permission. “Design and Analysis of a Novel Low-Power Exclusive-OR Gate Based on Quantum-Dot Cellular Automata” By Haotian Chen, Hongjun Lv, Zhang Zhang, Xin Cheng and Guangjun Xie in Journal of Circuits, Systems, and Computers, Vol. 28, No. 8, 2017 The advantages such as high operating frequency (in the range of few THz), low power dissipation, small size and high density in the nano regime has led to the application of Quantum dot Cellular Automata (QCA) in designing various digital circuits. In this brief, an ultra-efficient two input XOR gate design in QCA is proposed. It is a single layer design consisting of only 9 cells with no crossover and operating on cell to cell interaction. The functionality of the proposed gate has been verified at both physical and simulation level. In addition to this, fault tolerance to single cell missing defect, single cell addition defect and single cell displacement defect of the proposed XOR gate has also been presented. Based on the performance evaluation, it is seen that the proposed XOR gate has least cell count, least area and least latency which in turn leads to least circuit cost. Also, the proposed design dissipates least energy. The applicability of proposed XOR gate has also been investigated by designing various cost efficient digital circuits such as full adder, parity checker, etc.

A thermally aware performance analysis of quantum cellular automata logic gates

<span lang="EN-US">The high-performance digital circuits can be constructed at high operating frequency, reduced power dissipation, portability, and large density. Using conventional complementary-metal-oxide-semiconductor (CMOS) design process, it is quite difficult to achieve ultra-high-speed circuits due to scaling problems. Recently quantum dot cellular automata (QCA) are prosed to develop logic circuits at atomic level. In this paper, we analyzed the performance of QCA circuits under different temperature effects and observed that polarization of the cells is highly sensitive to temperature. In case of the 3-input majority gate the cell polarization drops to 50% with an increase in the temperature of 18 K and for 5 input majority gate the cell polarization drops more quickly than the 3-input majority. Further, the performance of majority gates also compared in terms of area and power dissipation. It has been noticed that the proposed logic gates can also be used for developing simple and complex and memory circuits.</span>

Programmable Synchronous 2-Bit Counter in Quantum-Dot Cellular Automata

Quantum-dot Cellular Automata (QCA) is a newly-developed nanoscale electron device that has the potential to replace the conventional transistor in the future. Owing to the unique field-coupling mechanism of QCA, several constraints must be fulfilled during the design of QCA sequential circuits, which makes the construction of sequential circuits a relatively intractable issue in QCA research. In this paper, a programmable synchronous 2-bit counter in QCA is proposed, which is consisted of combinational logic and falling edge-triggered JK flip-flops. The count mode of the programmable counter can be changed on-demand by mode control signals. Moreover, an initial state setting method of the QCA circuit is also proposed during the design of the counter so that the effects of random initial states can be avoided. Simulation with QCADesigner software demonstrates the validity of the proposed counter.

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 and electrostatic interaction between dots in neighboring cells. QCA can achieve higher speed, lower power, 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 QCADesigner-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.

Defects of quantum dot cellular automata computing devices: An extensive review, evaluation, and future directions

Quantum dot cellular automata (QCA), a nanoscale technology, are more prone to faults due to their diminutive size and precise fabrication process. The defects of QCA circuits have been the topic of many research papers, and this work has conducted a comprehensive study of the defect characterisation of QCA circuits. In this work, the defects in QCA circuits are divided into four groups: faults in the synthesis phase, faults in the deposition phase, faults in the design phase, and other faults. In addition, some unusual defects, such as stuck-at faults and single electron faults, are looked at. The study of the existing QCA works shows that fault-tolerant wires, tiles, etc. are rarely discussed in the literature. The literature also lacks adequate explanations of the QCA fault-tolerant clocking mechanism and fabrication processes. This work describes the identified challenges as well as their possible solutions. Additionally, this article outlines the future direction of this research and any relevant constraints. As a result, the intended audience can have a holistic understanding of the faults associated with QCA. This effort also seeks to facilitate the understanding of QCA circuit defects by related researchers.

A unique universal block in QCA technology

The limitations of Complementary Metal Oxide Semiconductor (CMOS) such as high-power dissipation, short channel effects, and high lithography has prompted scientists to look forward to alternatives. Many nanotechnologies were emerged and still in the competition such as Fin Field-Effect Transistor (FinFET), Carbon Nanotube Field-Effect Transistor (CNFET), Quantum-dot Cellular Automata (QCA). QCA is a new nanoelectronics technology used a new method for calculations and it is a promising technology in terms of power dissipation. In QCA, circuit complexity is depending on cell count, area and latency. For commercial purposes a universal gate is necessary, this gate can be used alone to design any Boolean function, where in CMOS technology, the NAND or NOT gates have the ability to be a universal gate. The dominant gates in QCA are the majority gate with inverter where QCA circuits cannot be designed using only a universal gate. Because the structure of the gate is important in QCA, this paper introduces a new low complexity singular block that can be used as a universal block. The proposed block can be used to form AND, OR, NOT, Exclusive-OR (XOR) and Multiplexer (MUX). So, this block not just used to design any circuit but also it can be used to form other important functions XOR and MUX to build large circuits in an optimum form.

An ultra-efficient design of fault-tolerant 3-input majority gate (FTMG) with an error probability model based on quantum-dots

Quantum-dot cellular automata (QCA) has recently attracted significant notice thanks to their inherent ability to decrease energy dissipation and decreasing area, which is the primary need of digital circuits. However, the lack of resistance of QCA circuits under defects in previous works is a vital challenge affecting the stability of the circuit and output production. In addition, with the high defect rate in QCA, suggesting resistance and stable structures is critical. Furthermore, the 3-input majority gate is a fundamental component of QCA circuits; therefore, improving this essential gate would enable the development of fault-tolerant circuits. This paper recommends a 3-input majority gate which is 100% fault-tolerant against single-cell omission defects. Moreover, the fundamental gates are introduced based on the proposed gate. In addition, an adder and a 1:2 decoder are also designed. Using QCADesigner 2.0.3 and QCAPro software, simulations of structures and analysis of power consumption are performed.

An efficient three-level nano-design for reversible gate using quantum dot-cellular automata with cost analysis

Quantum-dot Cellular Automata (CA) is a suitable nanotechnology for replacing CMOS circuits. The majority, inverter, and reversible structures, are the primary building blocks in quantum-dot CA circuits. Since the reversible gates have recently attained great attention, this paper proposes a new design of a reversible building block based on the Feynman gate. The proposed quantum-dot CA-based Feynman gate is denser and has low delay than the existing circuits. This paper also tests the possible implementation of the proposed design in quantum-dot CA. The QCADesigner is employed to test the functionality of the proposed structure. The proposed efficient quantum-dot CA-based Feynman gate has only 36 cells in three-layer. It consumes 0.03 µm2, which is the smallest among all previous designs. A quantum-cost comparison of the proposed reversible Feynman gate with conventional reversible gates demonstrates the cost-effectiveness of quantum-dot CA. The simulation result matched the truth table of the Feynman gate, indicating that the suggested quantum-dot CA architecture is functional. The proposed architecture can also be used for n-bit code converters as well.

A New Design of a 3 × 3 Reversible Circuit Based on a Nanoscale Quantum-Dot Cellular Automata

Quantum-dot cellular automata (QCA) is the best-suggested nanotechnology for designing digital electronic circuits. It has a higher switching frequency, low-power expenditures, low area, high speed and higher scale integration. Recently, many types of research have been on the design of reversible logic gates. Nevertheless, a high demand exists for designing high-speed, high-performance and low-area QCA circuits. Reversible circuits have notably improved with developments in complementary metal–oxide–semiconductor (CMOS) and QCA technologies. In QCA systems, it is important to communicate with other circuits and reversible gates reliably. So, we have used efficient approaches for designing a [Formula: see text] reversible circuit based on XOR gates. Also, the suggested circuits can be widely used in reversible and high-performance systems. The suggested architecture for the [Formula: see text] reversible circuit in QCA is composed of 28 cells, occupying only 0.04[Formula: see text][Formula: see text]m2. Compared to the state-of-the-art, shorter time, smaller areas, more operational frequency and better performance are the essential benefits of the suggested reversible gate design. Full simulations have been conducted with the utilization of QCADesigner software. Additionally, the proposed [Formula: see text] gate has been schematized using two XOR gates.

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

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-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.

Tree router design using a novel optimal QCA DEMUX

Quantum-dot cellular automata (QCA) is a new technology to replace CMOS technology in digital circuits. This replacement is necessary since further miniaturization of CMOS devices has posed serious challenges. In this paper, an optimized 1:2 demultiplexer (1:2 DEMUX) as a tree network switch is proposed. The tree network is examined, and the switches, which are the main components of the network, are used for routing. The proposed 1:2 DEMUX uses a rotated majority gate (RMG) based on QCA technology. According to the evaluation of the proposed 1:2 DEMUX circuit, 16 QCA cells are used with a total area and latency of 0.02μm2 and 0.25 clock cycles, respectively. A comparison with the best reported similar designs shows 15.78% improvement in the complexity, cell area, and area usage of the proposed 1:2 DEMUX. Another parameter that plays a very important role in QCA circuits is energy consumption, which can be measured with QCAPro software. In the proposed DEMUX circuit, the values of energy dissipation for 0.5, 1, and 1.5 Ek are 16.75, 24.84, and 34.6 meV respectively. The proposed router is the first of its kind that uses QCA-based DEMUX. This router has 146 cells, and its total area and latency are equal to 0.25μm2 and 0.75 clock cycles, respectively.

Novel Quantum-Dot Cellular Automata-Based Gate Designs for Efficient Reversible Computing

Reversible logic enables ultra-low power circuit design and quantum computation. Quantum-dot Cellular Automata (QCA) is the most promising technology considered to implement reversible circuits, mainly due to the correspondence between features of reversible and QCA circuits. This work aims to push forward the state-of-the-art of the QCA-based reversible circuits implementation by proposing a novel QCA design of a reversible full adder\full subtractor (FA\FS). At first, we consider an efficient XOR-gate, and based on this, new QCA circuit layouts of Feynman, Toffoli, Peres, PQR, TR, RUG, URG, RQCA, and RQG are proposed. The efficient XOR gate significantly reduces the required clock phases and circuit area. As a result, all the proposed reversible circuits are efficient regarding cell count, delay, and circuit area. Finally, based on the presented reversible gates, a novel QCA design of a reversible full adder\full subtractor (FA\FS) is proposed. Compared to the state-of-the-art circuits, the proposed QCA design of FA\FS reversible circuit achieved up to 57% area savings, with 46% and 29% reduction in cell number and delay, respectively.

Nano‐scale design of full adder and full subtractor using reversible logic based decoder circuit in quantum‐dot cellular automata

AbstractThis paper presents a reversible nano‐scale decoder circuit. The decoder is designed by utilizing the new quantum‐dot cellular automata (QCA) format of the QCA1 gate. This QCA1 gate provides 34.25% less cell count with 54.37% less area than the best existing designs. Thus, the proposed QCA1 gate provides less area considering the best existing state‐of‐the‐art plans. The IBMQ‐based quantum realization of the QCA1 gate is also illustrated. The reversible full adder and subtractor circuits by employing the proposed decoder are likewise explored in this paper. A four‐input reversible OR‐gate is structured and concatenates with a decoder circuit to frame the circuit for full adder and subtractor. The energy dissipation by these QCA circuits is assessed to build up that QCA is an attractive option to CMOS for realizing reversible logic designs. The implemented results are compared with the truth table to ensure operational accuracy. The planned circuits can be utilized to structure reversible designs for nano‐communication.

Methodology for Automated Design of Quantum-Dot Cellular Automata Circuits

Quantum-dot Cellular Automata (QCA) provide very high scale integration potential, very high switching frequency, and have extremely low power demands, which make the QCA technology quite attractive for the design and implementation of large-scale, high-performance nanoelectronic circuits. However, state-of-the-art QCA circuit designs were not derived by following a set of universal design rules, as is the case of CMOS circuits, and, as a result, it is either impossible or very difficult to combine QCA circuit blocks in effective large-scale circuits. In this paper, we introduce a novel automated design methodology, which builds upon a QCA specific universal design rules set. The proposed methodology assumes the availability of a generic QCA crossbar architecture and provides the means to customize it in order to implement any given logic function. The programming principles and the flow of the proposed automated design tool for crossbar QCA circuits are described analytically and we apply the proposed automated design method for the design of both combinatorial and sequential circuits. The obtained designs demonstrate that the proposed method is functional, easy to use, and provides the desired QCA circuit design unification.

A Space-Efficient Universal and Multi-Operative Reversible Gate Design Based on Quantum-Dots

Because of the high speed, low-power consumption, low latency and possible use at the atomic and molecular levels, Quantum-dot Cellular Automata (QCA) technology is one of the future nanoscale technologies that can replace the present transistor-based technology. For the purpose of creating QCA circuits, reversible logic can be regarded as an appropriate candidate. In this research, a new structure for multi-operative reversible designs is suggested. The Saeid Nima Gate (SNG), proposed in this research study, is a brand-new, incredibly effective, multi-operative, universal reversible gate implemented in QCA nanotechnology employing both majority and inverter gates. Reversible gates, also known as reversible logic gates, are gates that have n inputs and n outputs, which is an equal number of inputs and outputs. The amount of energy lost during computations will be reduced if the numbers of inputs and outputs are identical. The proposed gate is modified and reorganized to optimize further, employing exact QCA cell interaction. All fundamental logic gates are implemented using it to demonstrate the universality of the proposed SNG. Reversible logic has advanced, and as a result, our suggested solution has a lower quantum cost than previously reported systems. The suggested design is simulated using the QCADesigner-E tools.

Cost-efficient method for inverter reduction and proper placement in quantum-dot cellular automata

ABSTRACT The Quantum-dot Cellular Automata (QCA), an emerging technology, is observed to be the most viable solution to current CMOS. It is capable of finding solutions to challenges, like high power consumptionand device density. The elementary logic primitives are the majority gate, inverter and wire. In QCA, two different event cell orientations for the realisation of the inverter are available, where the diagonally oriented structure (DOS) is mostly utilised in logic synthesis. However, considering the cell misalignment and displacement, the DOS prevails with a more stable polarised output. But the use of DOS increases cell count which increases the area of the circuit. So, it is desirable to minimise the inverter in a circuit due to the non-availability of the simple logic unit of the inverter. In this paper, two algorithms are proposed for the synthesis of cost-efficient QCA circuits from any boolean function to minimize logic primitives. The proposed role-based mechanism for boolean function synthesis results in the reduction of inverter gate, circuit size, QCA cost and power dissipation. The efficiency of the proposed algorithms has been verified with the realization of standard functions, adders and symmetric functions. A significant improvement in inverter reduction has been reported.

Presentation of a fault tolerance algorithm for design of quantum-dot cellular automata circuits

A novel algorithm for working out the Kink energy of quantum-dot cellular automata (QCA) circuits and their fault tolerability is introduced. In this algorithm at first with determining the input values on a specified design, the calculation between cells makes use of Kink physical relations will be managed. Therefore, the polarization of any cell and consequently output cell will be set. Then by determining missed cell(s) on the discussed circuit, the polarization of output cell will be obtained and by comparing it with safe state or software simulation, its fault tolerability will be proved. The proposed algorithm was implemented on a novel and advance fault tolerance full adder whose performance has been demonstrated. This algorithm could be implemented on any QCA circuit. Noticeably higher speed of the algorithm than simulation and traditional manual methods, expandability of this algorithm for variable circuits, beyond of four-dot square of QCA circuits, and the investigation of several damaged cells instead just one and special cell are the advantages of algorithmic action.