Dissertations / Theses on the topic 'Molecular quantum-dot cellular automata'
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1
Karim, Faizal. "Clocking electrode design and phase analysis for molecular quantum-dot cellular automata based circuits." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/31504.
Full textAbstract:
Molecular quantum-dot cellular automaton (QCA) offers an alternative paradigm
for computing at the nano-scale. Such Q C A circuits require an external
clock, which can be generated using a network of submerged electrodes, to
synchronize information flow, and provide the required power to drive the
computation. In this thesis, the effect of electrode separation and applied
potential on the likelihood of different Q C A cell states of molecular cells located
above and in between two adjacent electrodes is analysed. Using this
analysis, estimates of operational ranges are developed for the placement,
applied potential, and relative phase between adjacent clocking electrodes to
ensure that only those states that are used in the computation, are energetically
favourable. Conclusions on the trade-off between cell size and applied
clocking potential are drawn and the temperature dependency on the operation
of fundamental Q C A building blocks is considered. Lastly, the impact
of random phase shifts on the underlying clocking network is investigated
and a set of universal Q C A building blocks is classified into distinct groups
based on their sensitivity to these random phase shifts.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
2
Davies, Hazel M. "Synthesis and characterisation of molecular materials." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501495.
Full textAbstract:
Chapter 1 contains a brief background into subjects such as Robin-Day classes, binary code, logic gates and electrochemistry in order to aid understanding of the rest of the chapter. The unique paradigm of Molecular Quantum Cellular Automata (MQCA) is presented along with the advantages it offers to traditional silicon based electronics. A summary of the existing modelled and synthesised MQCA systems is included along with an explanation of the characteristics required for materials to be suitable for MQCA. The subject of chapter 2 is cyclopentadiene cobalt cyclobutadiene complexes for the application of MQCA. The introduction examines the mechanism for the formation of cyclopentadiene cobalt cyclobutadiene complexes and the bonding in these compounds. A range of acetylenes were prepared for the formation of cyclopentadiene cobalt cyclobutadiene complexes were examined and characterised. Metal fragments including {Ru(dppe)2Cl} and AuPPh3Cl were attached to a cyclopentadiene cobalt cyclobutadiene core and these materials were characterised. The subject of chapter 3 is benzene based materials for the application of MQCA. 1,2,4,5-tetrakis(ferrocenylethynyl)benzene was prepared, characterised and the electrochemistry was examined for electronic communication between the ferrocene sites. A range of two metal centre compounds were examined for solubility and electrochemical stability with the view of preparing four metal centre compounds with a benzene core. The subject of chapter 4 is porphyrin based materials. This was the first area of work for this thesis and was discontinued. A brief summary of the synthetic work carried out is described, along with some literature work that was published whilst this work was being carried. Chapter 5 contains the experimental information for chapters 2-4.
3
Santana, Bonilla Alejandro, Rafael Gutierrez, Sandonas Leonardo Medrano, Daijiro Nozaki, Alessandro Paolo Bramanti, and Gianaurelio Cuniberti. "Structural distortions in molecular-based quantum cellular automata: a minimal model based study." Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36371.
Full textAbstract:
Molecular-based quantum cellular automata (m-QCA), as an extension of quantum-dot QCAs, offer a novel alternative in which binary information can be encoded in the molecular charge configuration of a cell and propagated via nearest-neighbor Coulombic cell–cell interactions. Appropriate functionality of m-QCAs involves a complex relationship between quantum mechanical effects, such as electron transfer processes within the molecular building blocks, and electrostatic interactions between cells. The influence of structural distortions of single m-QCA are addressed in this paper within a minimal model using an diabatic-to-adiabatic transformation. We show that even small changes of the classical square geometry between driver and target cells, such as those induced by distance variations or shape distortions, can make cells respond to interactions in a far less symmetric fashion, modifying and potentially impairing the expected computational behavior of the m-QCA.
4
Santana-Bonilla, Alejandro. "Density functional theory and model-based studies of charge transfer and molecular self-organization on surfaces:." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-222478.
Full textAbstract:
Molecular-based quantum cellular automata (m-QCA), as an extension of quantum-dot QCAs, offer a novel alternative in which binary information can be encoded in the molecular charge configuration of a cell and propagated via nearest-neighbor Coulombic cell-cell interactions. Appropriate functionality of m-QCAs involves a complex relationship between quantum mechanical effects, such as electron transfer processes within the molecular building blocks, and electrostatic interactions between cells. In the first part of this document, the influence of structural distortions in single m-QCA is addressed within a minimal model using an diabatic-to-adiabatic transformation. Thus, it is shown that even small changes of the classical square geometry between driver and target cells, such as those induced by distance variations or shape distortions, can make cells respond to interactions in a far less symmetric fashion, modifying and potentially impairing the expected computational behavior of the m-QCA. The model has been further extended to consider time-dependent external electric fields in which a special emphasis is given to the profiles in which this external parameter can interact with the associated molecular complex. The results of the model have been validated by a direct comparison with first-principle calculations allowing to conclude the plausibility to induce the intra-molecular charge transfer process in a controllable manner via the interaction with the external electric field. The influence played by the electric field profile in the response of the molecular complex is also investigated. The results suggests a major role played by this variable in terms of the time length in which the intra-molecular charge transfer can be observed.
In the second part, first-principle theoretical calculations of the self-assembly properties and electronic structure of Ferrocene-functionalized complexes have been carried out. Hence, five different molecular complexes which offer a potential playground to realistic implement the m-QCA paradigm have been investigated. The main emphasis is given to study the interaction between localized charge-carrier molecular states and the delocalized surface states. The results of these calculations demonstrate the possibility to obtain real systems in which intra-molecular charge localization can be combined with self-assembly scaffolding and absorbed on either Highly oriented pyrolytic graphite (HOPG) or metallic-surfaces. Finally, the validation of these findings is carried out via comparison with accesible experimental results and opening the gate to plausible strategies where the paradigm can be implemented.
5
Srivastava, Saket. "Probabilistic modeling of quantum-dot cellular automata." [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002399.
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Santana-Bonilla, Alejandro [Verfasser], Gianaurelio [Akademischer Betreuer] Cuniberti, and Wendin [Gutachter] Goeran. "Density functional theory and model-based studies of charge transfer and molecular self-organization on surfaces: : implications for molecular-based Quantum Cellular Automata / Alejandro Santana-Bonilla ; Gutachter: Wendin Goeran ; Betreuer: Gianaurelio Cuniberti." Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1129105172/34.
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7
Mandell, Eric S. "Theoretical studies of inter-dot potential barrier modulation in quantum-dot cellular automata." Virtual Press, 2001. http://liblink.bsu.edu/uhtbin/catkey/1221305.
Full textAbstract:
Quantum-Dot Cellular Automata (QCA) is being investigated as a possible alternative for encoding and processing binary information in an attempt to realize dramatic improvements in device density and processing speed over conventional CMOS design. The binary information is encoded in the locations of two excess electrons in a system of four quantum dots. The dots are arranged with each on a corner of a square, and electrons are able to quantum-mechanically tunnel between dots. Each set of four dots and two excess electrons constitutes a QCA cell. Coulomb repulsion ensures that the electrons will tend to occupy antipodal sites, giving two possible polarizations, or lowest energy ground states for a QCA cell. The electrons would tend to align along one diagonal or the other. Arrangements of QCA cells can be used to pass along input binary information and perform necessary logic operations on the input signal.When electrons tunnel back and forth between dots, it is possible they will occupy excited states in the dots. Two undesirable effects result from this: 1) Energy will be dissipated to the environment and cause thermal heating, and 2) it is possible a cell could become locked in a metastable state, which may be a local energy minimum, but is not one of the ground state polarizations we desire. Through the modulation of the heights of the inter-dot potential barriers, it would be possible to allow electrons to more easily tunnel between dots. This would help prevent the system from reaching excited states. The time variance in the heights of the potential barriers must be greater than the time it takes for the electrons to tunnel between dots, thus, effectively clocking the QCA device.We present theoretical studies of controlling the inter-dot potential barriers in a QCA device using an electric field due to electrostatically charged rods. The amount of charge on the rods is varied in time to increase and decrease the electric field, which will raise and lower the inter-dot potential barriers as desired. Different arrangements of rods provide different time-dependent behavior in the electric field, which may be useful depending on the arrangements of QCA cells required to make a logic device.Department of Physics and Astronomy
8
Hendrichsen, Melissa K. "Thermal effect and fault tolerance in quantum dot cellular automata." Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1314329.
Full textAbstract:
To have a useful QCA device it is first necessary to study how to control data flow in a device, then study how temperature and manufacturing defects will affect the proper output of the device. Theoretically a "quantum wire" of perfectly aligned QCA cells at zero Kelvin temperature has been examined. However, QCA processors will not be operating at a temperature of zero Kelvin and inherently the manufacturing process will introduce defects into the system. Many different types of defects could occur at the device level and the individual cell level, both kinds of defects should be examined. Device defects include but are not limited to linear and/or rotational translation, and missing or extra cell(s). The internal cell defects would include an odd sized cell, and one or more miss-sized or dislocated quantum dot(s). These defects may have little effect on the operation of the QCA device, or could cause a complete failure. In addition, the thermal effect on the QCA devices may also cause a failure of the device or system. The defect and thermal operating limit of a QCA device must be determined.In the present investigation, the thermal and defect tolerance of clocked QCA devices will be studied. In order to study tolerance of QCA devices theoretical models will be developed. In particular, some existing computer simulation programs will be studied and expanded.Department of Physics and Astronomy
9
Kanuchok, Jonathan L. "The thermal effect and clocking in quantum-dot cellular automata." Virtual Press, 2004. http://liblink.bsu.edu/uhtbin/catkey/1286605.
Full textAbstract:
We present a theoretical study of quasi-adiabatic clocking and thermal effect in Quantum-dot Cellular Automata (QCA). Quasi-adiabatic clocking is the modulation of an inter-dot potential barrier in order to keep the QCA cells near the ground state throughout the switching process. A time-dependent electric field is calculated for arrays of charged rods. The electron tunneling between dots is controlled by raising and lowering a potential barrier in the cell.A quantum statistical model has been introduced to obtain the thermal average of polarization of a QCA cell. We have studied the thermal effect on QCA devices. The theoretical analysis has been approximated for a two-state model where the cells are in one of two possible eigenstates of the cell Hamiltonian. In general, the average polarization of each cell decreases with temperature and the distance from the driver cells. The results demonstrate the critical nature of temperature dependence for the operation of QCA.Department of Physics and Astronomy
10
Tung, Chia-Ching. "Implementation of multi-CLB designs using quantum-dot cellular automata /." Online version of thesis, 2010. http://hdl.handle.net/1850/11699.
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Barclay, Travis J. "The temperature effect and defect study in quantum-dot cellular automata." Virtual Press, 2005. http://liblink.bsu.edu/uhtbin/catkey/1319217.
Full textAbstract:
Quantum-dot Cellular Automata (QCA) is a new paradigm for computation that utilizes polarization states instead of using current switching. It is being studied because of the realization of the quickly approaching limitation of the current CMOS technology. The location of two excess electrons located within four or five quantum dots on a particular cell can transmit the binary information. These dots are located in the corner of a square cell, and if there is a fifth dot it is located in the center. The electrons are allowed to tunnel freely among the dots, but are restricted from tunneling between neighboring cells. Because of the interaction between the electrons, they will anti-align within the cell giving one of two particular configurations. This configuration can be transmitted to neighboring cells. In other words, data is flowing.We present a numerical study of the fabrication defect's influence on Quantum-dot Cellular Automata (QCA) operation. The statistical model that has been introduced simulates the random distribution of positional defects of the dots within cells and of cells within arrays. Missing dots within a QCA cell structure have also been studied.We have studied specific non-clocked QCA devices using the Inter-cellular Hartree Approximation, for different temperatures. Parameters such as success rate and breakdown displacement factor were defined and calculated numerically. Results show the thermal dependence of the breakdown displacement factor of the QCA devices. It has been shown, that the breakdown displacement factor decreases with increasing temperature. As expected, multiple defects within the same QCA array have shown a reduction in success rate greater than that of a single defect influencing the system.Department of Physics and Astronomy
12
Patalay, Dinkar. "64-bit high efficiency binary comparator in quantum-dot cellular automata." Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10111200.
Full textAbstract:
Quantum-dot Cellular Automata (QCA) are proposed models of quantum computation, which are articulated in analogy to Von Neumann's conventional models of cellular automata. These models are worthy for the architecture of ultra-dense low-power and high-performance digital circuits. Efficient solutions have recently been proposed for several arithmetic circuits, such as adders, multipliers, and comparators. Since the design of digital circuits in QCA still poses several challenges, novel implementation strategies and methodologies are highly desirable. This project demonstrates a new design approach oriented to the implementation of binary comparators using QCA. This strategy is implemented for designing various architectures of binary comparator. With respect to existing counterparts, the comparators proposed here exhibit significantly higher speed and reduced overall area.
13
Singhal, Rahul. "Logic Realization Using Regular Structures in Quantum-Dot Cellular Automata (QCA)." PDXScholar, 2011. https://pdxscholar.library.pdx.edu/open_access_etds/196.
Full textAbstract:
Semiconductor industry seems to approach a wall where physical geometry and power density issues could possibly render the device fabrication infeasible. Quantum-dot Cellular Automata (QCA) is a new nanotechnology that claims to offer the potential of manufacturing even denser integrated circuits, which can operate at high frequencies and low power consumption. In QCA technology, the signal propagation occurs as a result of electrostatic interaction among the electrons as opposed to flow to the electrons in a wire. The basic building block of QCA technology is a QCA cell which encodes binary information with the relative position of electrons in it. A QCA cell can be used either as a wire or as logic. In QCA, the directionality of the signal flow is controlled by phase-shifted electric field generated on a separate layer than QCA cell layer. This process is called clocking of QCA circuits. The logic realization using regular structures such as PLAs have played a significant role in the semiconductor field due to their manufacturability, behavioral predictability and the ease of logic mapping. Along with these benefits, regular structures in QCA's would allow for uniform QCA clocking structure. The clocking structure is important because the pioneers of QCA technology propose it to be fabricated in CMOS technology. This thesis presents a detailed design implementation and a comparative analysis of logic realization using regular structures, namely Shannon-Lattices and PLAs for QCAs. A software tool was developed as a part of this research, which automatically generates complete QCA-Shannon-Lattice and QCA-PLA layouts for single-output Boolean functions based on an input macro-cell library. The equations for latency and throughput for the new QCA-PLA and QCA-Shannon-Lattice design implementations were also formulated. The correctness of the equations was verified by performing simulations of the tool-generate layouts with QCADesigner. A brief design trade-off analysis between the tool-generated regular structure implementation and the unstructured custom layout in QCA is presented for the full-adder circuit.
14
Venkataramani, Praveen. "Sequential quantum dot cellular automata design and analysis using Dynamic Bayesian Networks." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002787.
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Karim, Faizal. "Investigation of the correlated dynamics of quantum-dot cellular automata circuits and systems." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/49968.
Full textAbstract:
Quantum-dot Cellular Automata (QCA) provides a basis for classical computation without transistors. Many simulations of QCA rely upon the Intercellular Hartree Approximation (ICHA), which neglects the possibility of entanglement between cells. While simple and computationally efficient, the ICHA’s many shortcomings make it difficult to accurately model the dynamics of large systems of QCA cells. On the other hand, solving a full Hamiltonian for each circuit, while more accurate, becomes computationally intractable as the number of cells increases. This work explores an intermediate solution that exists somewhere in the solution space spanned by the ICHA and the full Hamiltonian.
The solution presented in this thesis builds off of the work done by Toth et al., and studies the role that correlations play in the dynamics of QCA circuits. Using the coherence-vector formalism, we show that we can accurately capture the dynamical behaviour of QCA systems by including two-cell correlations.
In order to capture the system’s interaction with the environment, we introduce a new method for computing the steady-state configurations of a QCA system using well-known stochastic methods, and use the relaxation-time approximation to drive the QCA system to these configurations. For relatively-low temperatures, we show that this approach is accurate to within a few percent, and can be computed in linear time.
QCADesigner, the de facto simulation tool used in QCA research, has been used and cited in hundreds of papers since its creation in 2004. By implementing computationally accurate and efficient algorithms to the existing simulation engines present in QCADesigner, this research is expected to make a significant contribution to the future of QCA circuit design. In particular, researchers in the field will be able to identity a whole new set of design rules that will lead to more compact circuit design, realistic clocking schemes, and crosstalk-tolerant layouts. In addition, proper estimates on the power dissipation, pipelining, and limitations of room temperature operation will now be feasible for QCA circuits of any size; a huge step forward for QCA design.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Padgett, Benjamin David. "Modeling and simulation of fault tolerant properties of quantum-dot cellular automata devices." CardinalScholar 1.0, 2010. http://liblink.bsu.edu/uhtbin/catkey/1569024.
Full textAbstract:
I present a theoretical study of fault tolerant properties in Quantum-dot Cellular Automata (QCA) devices. The study consists of modeling and simulation of various possible manufacturing, fabrication and operational defects. My focus is to explore the effects of temperature and dot displacement defects at the cell level of various QCA devices. Results of simple devices such as binary wire, logical gates, inverter, cross-over and XOR will be presented. A Hubbard-type Hamiltonian and the inter-cellular Hartree approximation have been used for modeling the QCA devices. Random distribution has been used for defect simulations. In order to show the operational limit of a device, defect parameters have been defined and calculated. Results show fault tolerance of a device is strongly dependent on the temperature as well as on the manufacturing defects.Cell design -- Basic logic gates -- The exclusive or gate.
Department of Physics and Astronomy
17
Kapkar, Rohan Viren. "Modeling and Simulation of Altera Logic Array Block using Quantum-Dot Cellular Automata." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1304616947.
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Raviraj, Tejas. "Design, Implementation, and Test of Next Generation FPGAs Using Quantum-Dot Cellular Automata Technology." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302291185.
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Anduwan, Gabriel A. Y. "The thermal effect and fault tolerance on nanoscale devices : the quantum dot cellular automata (QCA)." Virtual Press, 2007. http://liblink.bsu.edu/uhtbin/catkey/1369913.
Full textAbstract:
The defects and fault tolerance study is essential in the QCA devices in order to know its characteristics. Knowing the characteristics, one can understand the flow of information in a QCA system with and without manufacturing and operational defects. The manufacturing defects could be at device level or cell level. At the device level, the cell could be rotated, displaced vertically or horizontally, the cell could be missing or the size of the cell could be different. At the cell level, there could be a missing dot, dot could be displaced from its position or the size of the dots could be different. The operational defects are due to its surrounding, such as temperature or stray charge. Each of these defects and fault tolerances can be studies in detail in order to find the optimum working conditions where the information can be safely transmitted to the appropriate locations in the device.The theoretical studies have shown that at absolute temperature and without any defect, the QCA devices are operational. But it is almost impossible to manufacture a perfect or defect free device, and also it is impractical to think about operating a system at absolute zero temperature environment.Therefore, it is important to investigate the fault tolerant properties with defects and higher temperatures to see how far the QCA device can operate safely. Many studies have been done to investigate the fault tolerant properties in QCA devices. However, these studies have not completely exhausted the study of defects and temperature effects. In this study, the dot displacement and missing dots with temperature effects are investigated for the basic QCA devices and a Full Adder. In order to study fault tolerant properties, the existing theoretical model and computer simulation programs have been expanded and used. The defect characteristics have been simulated using normal distribution.Department of Physics and Astronomy
20
Balijepalli, Heman. "Design, Implementation, and Test of Novel Quantum-dot Cellular Automata FPGAs for the beyond CMOS Era." University of Toledo / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1333730938.
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Labrado, Carson. "Exploration of Majority Logic Based Designs for Arithmetic Circuits." UKnowledge, 2017. http://uknowledge.uky.edu/ece_etds/102.
Full textAbstract:
Since its inception, Moore's Law has been a reliable predictor of computational power. This steady increase in computational power has been due to the ability to fit increasing numbers of transistors in a single chip. A consequence of increasing the number of transistors is also increasing the power consumption. The physical properties of CMOS technologies will make this powerwall unavoidable and will result in severe restrictions to future progress and applications. A potential solution to the problem of rising power demands is to investigate alternative low power nanotechnologies for implementing logic circuits. The intrinsic properties of these emerging nanotechnologies result in them being low power in nature when compared to current CMOS technologies. This thesis specifically highlights quantum dot celluar automata (QCA) and nanomagnetic logic (NML) as just two possible technologies. Designs in NML and QCA are explored for simple arithmetic units such as full adders and subtractors. A new multilayer 5-input majority gate design is proposed for use in NML. Designs of reversible adders are proposed which are easily testable for unidirectional stuck at faults.
22
Thapliyal, Himanshu. "Design, Synthesis and Test of Reversible Circuits for Emerging Nanotechnologies." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3379.
Full textAbstract:
Reversible circuits are similar to conventional logic circuits except that they are built from reversible gates. In reversible gates, there is a unique, one-to-one mapping between the inputs and outputs, not the case with conventional logic. Also, reversible gates require constant ancilla
inputs for reconfiguration of gate functions and garbage outputs that help in keeping reversibility. Reversible circuits hold promise in futuristic computing technologies like quantum computing, quantum dot cellular automata, DNA computing, optical computing, etc. Thus, it is important to
minimize parameters such as ancilla and garbage bits, quantum cost and delay in the design of reversible circuits.
The first contribution of this dissertation is the design of a new reversible gate namely the TR gate (Thapliyal-Ranganathan) which has the unique structure that makes it ideal for the realization of arithmetic circuits such as adders, subtractors and comparators, efficient in terms of the parameters such as ancilla and garbage bits, quantum cost and delay. The second contribution is the development of design methodologies and a synthesis framework to synthesize reversible data path
functional units, such as binary and BCD adders, subtractors, adder-subtractors and binary comparators. The objective behind the proposed design methodologies is to synthesize arithmetic and logic functional units optimizing key metrics such as ancilla inputs, garbage outputs, quantum cost and delay. A library of reversible gates such as the Fredkin gate, the Toffoli gate, the TR gate, etc. was developed by coding in Verilog for use during synthesis. The third contribution of this dissertation
is the set of methodologies for the design of reversible sequential circuits such as reversible latches, flip-flops and shift registers. The reversible designs of asynchronous set/reset D latch and the D flip-flop are attempted for the first time. It is shown that the designs are optimal in terms of number of garbage outputs while exploring the best possible values for quantum cost and delay.
The other important contributions of this dissertation are the applications of reversible logic as well as a special class of reversible logic called conservative reversible logic towards concurrent (online) and offline testing of single as well as multiple faults in traditional and reversible nanoscale VLSI circuits, based on emerging nanotechnologies such as QCA, quantum computing, etc. Nanoelectronic devices tend to have high permanent and transient faults and thus are susceptible to high
error rates. Specific contributions include (i) concurrently testable sequential circuits for molecular QCA based on reversible logic, (ii) concurrently testable QCA-based FPGA, (iii) design of self checking conservative logic gates for QCA, (iv) concurrent multiple error detection in emerging nanotechnologies using reversible logic, (v) two-vectors, all 0s and all 1s, testable reversible sequential circuits.
23
Isaksen, Beth Claire. "Molecular quantum-dot cellular automata." 2003. http://etd.nd.edu/ETD-db/theses/available/etd-07012003-121454/.
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Yan, Minjun. "Electric field detection by electrostatic force microscopy for clocking quantum-dot cellular automata molecules." 2006. http://etd.nd.edu/ETD-db/theses/available/etd-07312006-140503/.
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Thesis (Ph. D.)--University of Notre Dame, 2006.Thesis directed by Gary H. Bernstein for the Department of Electrical Engineering. "July 2006." Includes bibliographical references (leaves 120-136).
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Jin, Zengxiao. "Fabrication and measurement of molecular quantum cellular automata (QCA) device." 2006. http://etd.nd.edu/ETD-db/theses/available/etd-06292006-143025/.
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Thesis (M.S.E.E.)--University of Notre Dame, 2006.Thesis directed by Gregory L. Snider for the Department of Electrical Engineering. "June 2006." Includes bibliographical references (leaves 64-65).
26
Jiao, Jieying. "Synthesis, characterization and surface attachment of square mixed-valence complexes as building blocks for molecular quantum cellular automata." 2004. http://etd.nd.edu.lib-proxy.nd.edu/ETD-db/theses/available/etd-07062004-104143/.
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Thesis (Ph. D.)--University of Notre Dame, 2004.Thesis directed by Thomas P. Fehlner for the Department of Chemistry and Biochemistry. "July 2004." Includes bibliographical references (leaves 199-213).
27
Santana-Bonilla, Alejandro. "Density functional theory and model-based studies of charge transfer and molecular self-organization on surfaces:: implications for molecular-based Quantum Cellular Automata." Doctoral thesis, 2016. https://tud.qucosa.de/id/qucosa%3A30246.
Full textAbstract:
Molecular-based quantum cellular automata (m-QCA), as an extension of quantum-dot QCAs, offer a novel alternative in which binary information can be encoded in the molecular charge configuration of a cell and propagated via nearest-neighbor Coulombic cell-cell interactions. Appropriate functionality of m-QCAs involves a complex relationship between quantum mechanical effects, such as electron transfer processes within the molecular building blocks, and electrostatic interactions between cells. In the first part of this document, the influence of structural distortions in single m-QCA is addressed within a minimal model using an diabatic-to-adiabatic transformation. Thus, it is shown that even small changes of the classical square geometry between driver and target cells, such as those induced by distance variations or shape distortions, can make cells respond to interactions in a far less symmetric fashion, modifying and potentially impairing the expected computational behavior of the m-QCA. The model has been further extended to consider time-dependent external electric fields in which a special emphasis is given to the profiles in which this external parameter can interact with the associated molecular complex. The results of the model have been validated by a direct comparison with first-principle calculations allowing to conclude the plausibility to induce the intra-molecular charge transfer process in a controllable manner via the interaction with the external electric field. The influence played by the electric field profile in the response of the molecular complex is also investigated. The results suggests a major role played by this variable in terms of the time length in which the intra-molecular charge transfer can be observed.
In the second part, first-principle theoretical calculations of the self-assembly properties and electronic structure of Ferrocene-functionalized complexes have been carried out. Hence, five different molecular complexes which offer a potential playground to realistic implement the m-QCA paradigm have been investigated. The main emphasis is given to study the interaction between localized charge-carrier molecular states and the delocalized surface states. The results of these calculations demonstrate the possibility to obtain real systems in which intra-molecular charge localization can be combined with self-assembly scaffolding and absorbed on either Highly oriented pyrolytic graphite (HOPG) or metallic-surfaces. Finally, the validation of these findings is carried out via comparison with accesible experimental results and opening the gate to plausible strategies where the paradigm can be implemented.
28
Frost, Sarah Elizabeth. "Memory architecture for quantum-dot cellular automata." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-03212005-160059/.
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Thesis (M.S.C.S.E.)--University of Notre Dame, 2005.Thesis directed by Peter Kogge for the Department of Computer Science and Engineering. "March 2005." Includes bibliographical references (leaves 129-133).
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Kummamuru, Ravi Kiran. "Experimental studies on quantum-dot cellular automata devices." 2004. http://etd.nd.edu/ETD-db/theses/available/etd-04162004-163831/.
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Thesis (Ph. D.)--University of Notre Dame, 2004.Thesis directed by Gregory L. Snider for the Department of Electrical Engineering. "April 2004." Includes bibliographical references (leaves 135-139).
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Liu, Mo. "Robustness and power dissipation in quantum-dot cellular automata." 2006. http://etd.nd.edu/ETD-db/theses/available/etd-02212006-120033/.
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Patitz, Zachary Daniel. "Fault tolerant quantum-dot cellular automata majority gate design." 2006. http://digital.library.okstate.edu/etd/umi-okstate-1816.pdf.
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Dysart, Timothy J. "Defect properties and design tools for quantum dot cellular automata." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-07212005-155243/.
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Thesis (M.S.C.S.E.)--University of Notre Dame, 2005.Thesis directed by Peter M. Kogge for the Department of Computer Science and Engineering. "July 2005." Includes bibliographical references (leaves 117-122).
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賴建丞. "Minimum-Crossing Layout Synthesis for Quantum-Dot Cellular Automata (QCA)." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/43253686911218981810.
Full textAbstract:
碩士國立交通大學
資訊科學系所
94
Quantum-dot cellular automata (QCA) is a novel nano-scale computing mechanism that can represent binary information based on spatial distribution of electron charge configuration in molecules. A QCA physical synthesis flow consists of four stages: partitioning, placement, pin-assignment and channel routing. Because wire crossings in QCA layout increase the complexity of circuit layout design, this work focus on minimizing wire crossings of the circuit under synthesis. In this paper, the problem of QCA placement is mapped to a famous problem “k-layer bigraph crossing problem” and a new heuristic is developed for this problem. Pin assignment stage is prior to channel routing stage, which provides a legal pin assignment for the following channel routing stage. Finally, a new cycle breaking algorithm to reduce wire crossings in channel routing stage is presented. Based on our experimental results, placement and cycle breaking obtain good crossing reduction. We also simulate our circuit by QCA Design 2.0.3 and obtain correct simulation result and other benchmark circuits does not have simulation result since they are too large to complete simulation in time.
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Tang, Yong. "Experimental demonstration of radio frequency quantum-dot cellular automata devices." 2009. http://etd.nd.edu/ETD-db/theses/available/etd-12102009-172906/.
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Thesis (Ph. D.)--University of Notre Dame, 2009.Thesis directed by Patrick J. Fay and Alexei O. Orlov for the Department of Electrical Engineering. "December 2009." Includes bibliographical references (leaves 169-177).
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Cho, Heumpil. "Adder and multiplier design and analysis in quantum-dot cellular automata." Thesis, 2006. http://hdl.handle.net/2152/2848.
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Kim, Seong-Wan. "Design of parallel multipliers and dividers in quantum-dot cellular automata." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-2730.
Full textAbstract:
Conventional CMOS (the current dominant technology for VLSI) implemented with ever smaller
transistors is expected to encounter serious problems in the near future with the need for difficult fabrication technologies. The most important problem is heat generation. The desire for device density, power dissipation and performance improvement necessitates new technologies that will provide innovative solutions to integration and computations. Nanotechnology, especially Quantum-dot Cellular Automata (QCA)
provides new possibilities for computing owing to its unique properties. Numerous nanoelectronic devices are being investigated and many experimental devices have been developed. Thus, high level circuit design is needed to keep pace with changing physical studies. The circuit design aspects of QCA have not been studied much because of its novelty. Arithmetic units, especially multipliers and dividers play an important role in the design of digital processors and application specific systems.
Therefore, designs for parallel multipliers and dividers are presented using this technology.
Optimal design of parallel multipliers for Quantum-Dot Cellular
Automata is explored in this dissertation. As a main basic element to build multipliers, adders are implemented and compared their performances with previous adders. And two different layout schemes that single layer and multi-layer wire crossings are compared and analyzed. This dissertation proposes three kinds of multipliers. Wallace and Dadda parallel multipliers, quasi-modular multipliers, and array multipliers are designed and simulated with several different operand sizes.
Also array multipliers that are well suited in QCA are constructed and formed by a regular lattice of identical functional units so that the structure is conformable to QCA technology without extra wire delay. All these designs are constructed using coplanar layouts and compared with other QCA multipliers. The delay, area and complexity are compared for several different operand sizes.
This research also studies divider designs for quantum-dot cellular automata. A digit recurrence restoring binary divider is a conventional design that serves as a baseline. By using controlled full subtractor cell units, a relatively simple and efficient implementation is realized. The Goldschmidt divider using the new architecture (data tag method) to control the various elements of the divider is compared for the performance.text
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Choi, Myungsu. "A study on a quantum-dot cellular automata based asynchronous circuit design." 2005. http://digital.library.okstate.edu/etd/umi-okstate-1625.pdf.
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Imre, Alexandra. "Experimental study of nanomagnets for magnetic quantum-dot cellular automata (MQCA) logic applications." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-03252005-050421/.
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Thesis (Ph. D.)--University of Notre Dame, 2005.Thesis directed by Wolfgang Porod and Gary H. Bernstein for the Department of Electrical Engineering. "April 2005." Includes bibliographical references (leaves 93-97).
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Beck, Adam Christopher. "STM investigation of phthalocyanines as possible building blocks for quantum-dot cellular automata." 2005. http://etd.nd.edu/ETD-db/theses/available/etd-10312005-193422/.
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Thesis (M.S.)--University of Notre Dame, 2005.Thesis directed by S. Alex Kandel for the Department of Chemistry and Biochemistry. "November 2005." Includes bibliographical references (leaves 52-56).
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Beard, Mary Jean. "Design and simulation of fault-tolerant Quantum-dot Cellular Automata (QCA) NOT gates." Thesis, 2006. http://hdl.handle.net/10057/561.
Full textAbstract:
This paper details the design and simulation of a fault-tolerant Quantum-dot Cellular Automata (QCA) NOT gate. A version of the standard NOT gate can be constructed to take advantage to the ability to easily integrate redundant structures into a QCA design. The fault-tolerant characteristics of this inverter are analyzed with QCADesigner v2.0.3 (Windows version) simulation software. These characteristics are then compared with the characteristics of two other non-redundant styles of NOT gates. The redundant version of the gate is more robust than the standard style for the inverter. However, another simple inverter style seems to be even more than this fault-tolerant design. Both versions of the gate will need to be studied further in the future to determine which design is most practical.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical and Computer Engineering
"July 2006."
Includes bibliographic references (leaves 31-33)
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Chilakam, Madhusudan. "A Novel Reconfiguration Scheme in Quantum-Dot Cellular Automata for Energy Efficient Nanocomputing." 2013. https://scholarworks.umass.edu/theses/1028.
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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.
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Liu, Mao-Hung, and 劉茂宏. "Simulation and Analysis of Two-Phase Clock Systems Based on Quantum-Dot Cellular Automata Architectures." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/99811596778301077516.
Full textAbstract:
碩士中國文化大學
材料科學與製造研究所
93
The quantum-dot cellular automata (QCA) technology is based on the interaction of bi-stable QCA cells constructed from four quantum dots. The cell is charged with two free electrons, which are able to tunnel between adjacent dots. These electrons tend to occupy antipodal sites as a result of their mutual electrostatic repulsion. The QCA paradigm is a revolutionary approach to molecular-scale computing which represents binary information using the charge configuration of nanostructures in lieu of current switching devices. Electrostatic interaction between neighboring cells allows the design of QCA wires, logic devices and even simple microprocessors. The design of QCA circuits now lies not only in the logic structure of the cells, but also in the layout of clocking wires. We discuss the clocking of QCA devices and connect layout to architecture. Two-phase logic design is a technique that has long been used in the IC industry to increase data throughput and improve silicon efficiency. Silicon area improvement can be realized by partitioning the design into control and datapath Sections, and by using two-phase clocking rather than edge-triggered. There are two benefits of two-phase clocking. An improvement in data throughput is often realized since control decisions and data manipulations can occur twice during the clock period. Also, since the time step resolution is now effectively doubled. the designer can take advantage of opportunities to share datapath resources.
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Varga, Edit. "Experimental study of new magnetic circuit elements built from nanomagnets for magnetic quantum-dot cellular automata logic applications." 2009. http://etd.nd.edu/ETD-db/theses/available/etd-12102009-133342/.
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Sultana, Sayeeda. "A design for testability scheme for modular and non-modular quantum dot cellular automata (QCA) employing stuck-at fault model." Thesis, 2006. http://spectrum.library.concordia.ca/9091/1/MR20755.pdf.
Full textAbstract:
Today leading VLSI experts predict a hard wall for CMOS and other conventional fabrication technology due to fundamental physical limits (ultra-thin gate oxide, short channel effects, doping fluctuations, etc.), and increasingly difficult and expensive lithography in nanoscale. Extensive research conducted in recent years at nanoscale aiming to surpass CMOS has proposed Quantum Dot Cellular Automata as a viable alternative for nanoscale computing. Quantum Dot Cellular Automata (QCA) paradigm is an innovatory approach to computing, which encodes binary information by means of charge configuration of nanostructures instead of current switching devices. The fundamental building block of QCA devices is the QCA cell, and electrostatic interaction between neighboring cells governs the design of all QCA wires and logic gates. The two primary logic elements in QCA technology are: majority voter and inverter. Binary wires and inverter chains are used for interconnection purposes. Logic operation AND, and OR can be achieved by maneuvering inputs to the majority voter. Clocking enables precise control over timing and data flow direction, as well as power gain in QCA circuits. Also proper clocking can achieve computational pipelining and can drastically reduce circuit power dissipation. Manufacturing of a QCA cell is expected to result in defects like cell displacement, misalignment, and absence of cell or additional cell in circuitry, causing the circuit to exhibit faulty behavior. So a well-defined testing scheme becomes necessary for this technology. Though the technology is different from conventional CMOS design, it is shown to be effective and realistic to use existing testing schemes at this stage. Stuck-at (s-a-v) fault model is quite acceptable in this regard in spite of the fact, that this model does not incorporate all the defective behaviors occurring in the fabrication process. With this in view, single stuck-at value faults have been considered for testing QCA circuits. In this thesis a new strategy for designing QCA logic, exhaustively testable for single s-a-v faults, is presented. In particular, the method facilitates QCA functionality testing. Any combinational logic can be implemented using only AND-OR gates (with negated signals available), and in QCA this generally results in reduced test set for exhaustive fault detection within the data path. Previously this strategy was used for QCA logic testing considering only primary inputs (either true or complemented, but not both) feeding different majority voters, which fails for general circuits where fanouts are allowed for primary inputs and their complement. Here, a design scheme has been proposed which makes testing possible for any combinational QCA circuit. The extension to modular design testing is also presented. Two design approaches are proposed for testing modular and non-modular logic. The first design uses 2 n ( n = primary inputs) ' Test Enable ' majority voters, and is tested with two 4-bit vectors regardless of complexity of design and the input size. Second design employs n majority voters for the same purpose, thus requiring lesser number of majority voters, but at the price of increased vector length. Application specific conditions would decide which design becomes optimal. Without going into the features of a particular QCA fabrication, errors on logic level is addressed, such that the approach achieves generality, and could be applied to any particular implementation of QCA. Also to overcome the fault masking in modular circuit design, a solution has been presented. To verify the scheme, a simulation and layout tool, QCADesigner version 2.0.3 was used. First the fault free circuit was designed and simulated. Then random s-a-v faults were injected in different locations of data path. In all cases, 100% fault coverage was achieved confirming the validity of proposed approach
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Kong, Inwook. "Improved algorithms and hardware designs for division by convergence." 2009. http://hdl.handle.net/2152/7844.
Full textAbstract:
This dissertation focuses on improving the division-by-convergence algorithm. While the division by convergence algorithm has many advantages, it has some drawbacks, such as a need for extra bits in the multiplier and a large ROM table for the initial approximation. To mitigate these problems, two new methods are proposed here. In addition, the research scope is extended to seek an efficient architecture for implementing a divider with Quantum-dot Cellular Automata (QCA), an emerging technology. For the first proposed approach, a new rounding method to reduce the required precision of the multiplier for division by convergence is presented. It allows twice the error tolerance of conventional methods and inclusive error bounds. The proposed method further reduces the required precision of the multiplier by considering the asymmetric error bounds of Goldschmidt dividers. The second proposed approach is a method to increase the speed of convergence for Goldschmidt division using simple logic circuits. The proposed method achieves nearly cubic convergence. It reduces the logic complexity and delay by using an approximate squarer with a simple logic implementation and a redundant binary Booth recoder. Finally, a new architecture for division-by-convergence in QCA is proposed. State machines for QCA often have synchronization problems due to the long wire delays. To resolve this problem, a data tag method is proposed. It also increases the throughput significantly since multiple division computations can be performed in a time skewed manner using one iterative divider.text
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Jun, Kihwan. "Modified non-restoring division algorithm with improved delay profile." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3300.
Full textAbstract:
This thesis focuses on reducing the delay of non-restoring division. Although the digit recurrence division is lower in complexity and occupies a smaller area than division by convergence, it has a drawback: slow division speed. To mitigate this problem, two modification ideas are proposed here for the non-restoring division, the fastest division algorithm of the digit recurrence division methods.
For the first proposed approach, the delay of the multiplexer for selecting the quotient digit and determining the way to calculate the partial remainder can be reduced through inverting the order of its flowchart. Second, one adder and one inverter can be removed by using a new quotient digit converter. To prove these ideas are valid, the simulation results comparing the modified non-restoring division and the standard non-restoring division are provided.text