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Kilin, S. Ya, J. Wrachtrup i kilin@ifanbel bas-net by. "Diamond Quantum Computer". ESI preprints, 2000. ftp://ftp.esi.ac.at/pub/Preprints/esi950.ps.
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Mosca, Michele. "Quantum computer algorithms". Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301184.
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Wallace, Julia. "Quantum computer software". Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369975.
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Giesecke, Normen. "Ternary quantum logic". PDXScholar, 2006. https://pdxscholar.library.pdx.edu/open_access_etds/4092.
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The application of Moore's Law would not be feasible by using the computing systems fabrication principles that are prevalent today. Fundamental changes in the field of computing are needed to keep Moore's Law operational. Different quantum technologies are available to take the advancement of computing into the future. Logic in quantum technology uses gates that are very different from those used in contemporary technology. Limiting itself to reversible operations, this thesis presents different methods to realize these logic gates. Two methods using Generalized Ternary Gates and Muthukrishnan Stroud Gates are presented for synthesis of ternary logic gates. Realizations of well-known quantum gates like the Feynman gate, Toffoli Gate, 2-qudit and 3-qudit SW AP gates are shown. In addition a new gate, the Inverse SW AP gate, is proposed and its realization is also presented.
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Papanikolaou, Nikolaos K. "Model checking quantum protocols". Thesis, University of Warwick, 2009. http://wrap.warwick.ac.uk/2236/.
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This thesis describes model checking techniques for protocols arising in quantum information theory and quantum cryptography. We discuss the theory and implementation of a practical model checker, QMC, for quantum protocols. In our framework, we assume that the quantum operations performed in a protocol are restricted to those within the stabilizer formalism; while this particular set of operations is not universal for quantum computation, it allows us to develop models of several useful protocols as well as of systems involving both classical and quantum information processing. We detail the syntax, semantics and type system of QMC’s modelling language, the logic QCTL which is used for verification, and the verification algorithms that have been implemented in the tool. We demonstrate our techniques with applications to a number of case studies.
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George, R. E. "Towards a silicon quantum computer". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599362.
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This thesis investigates the properties of electrons in silicon with a view to their use as quibits in a prospective quantum computer. The thesis first investigates the properties of Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET) devices doped with sodium, characterising bound-states formed by the presence of sodium ions though studying the temperature dependence of the device conductivity as s function of carrier density. The thesis then studies Electron Paramagnetic Resonance (EPR) of sodium doped silicon devices, searching for a resonance from the sodium bound-states, and determining the effect of moving the sodium atoms on the spectrogram, finding no sharp resonance due to the presence of sodium, but detecting the effects of the sodium drifting procedure on related E’ interface states. The EPR technique is then used to characterise the resonance from a related silicon-germanium sample containing an electron gas and point defects that has application as a standard reference sample containing an accurately determined number of spins. The work turns to fabricating and characterising Single Electron Transistor (SET) devise in silicon, with a view to application as a sensitive electrometer for use in a spin to charge conversion measurements. The device shows a magnetic field dependent oscillation in conductivity, consistent with the electron phase coherence length being larger than the dimensions of the SET at the lowest temperatures used. The document concludes with a review and suggestions for further work.
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Chong, Henry H. W. 1974. "Toward a personal quantum computer". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/42797.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 115-118).
by Henry H.W. Chong.
M.Eng.
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Delbecque, Yannick. "Quantum games as quantum types". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40670.
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In this thesis, we present a new model for higher-order quantum programming languages. The proposed model is an adaptation of the probabilistic game semantics developed by Danos and Harmer: we expand it with quantum strategies which enable one to represent quantum states and quantum operations. Some of the basic properties of these strategies are established and then used to construct denotational semantics for three quantum programming languages. The first of these languages is a formalisation of the measurement calculus proposed by Danos et al. The other two are new: they are higher-order quantum programming languages. Previous attempts to define a denotational semantics for higher-order quantum programming languages have failed. We identify some of the key reasons for this and base the design of our higher-order languages on these observations. The game semantics proposed in this thesis is the first denotational semantics for a lambda-calculus equipped with quantum types and with extra operations which allow one to program quantum algorithms. The results presented validate the two different approaches used in the design of these two new higher-order languages: a first one where quantum states are used through references and a second one where they are introduced as constants in the language. The quantum strategies presented in this thesis allow one to understand the constraints that must be imposed on quantum type systems with higher-order types. The most significant constraint is the fact that abstraction over part of the tensor product of many unknown quantum states must not be allowed. Quantum strategies are a new mathematical model which describes the interaction between classical and quantum data using system-environment dialogues. The interactions between the different parts of a quantum system are described using the rich structure generated by composition of strategies. This approach has enough generality to be put in relation with other work in quNous présentons dans cette thèse un nouveau modèlepour les langages de programmation quantique. Notre modèle est uneadaptation de la sémantique de jeux probabilistes définie par Danos etHarmer: nous y ajoutons des stratégies quantiquespour permettre la représentation des états et des opérations quantiques.Nous établissons quelques propriétés de base de ces stratégies. Cespropriétés sont ensuite utilisées pour construire des sémantiquesdénotationnelles pour trois langages de programmation quantique. Le premierlangage est une formalisation du calcul par mesures proposé par Danoset al. Les deux autres langages sont nouveaux: ce sont deslangages quantiques d'ordre supérieur dont la syntaxe a été construiteà partir d'observations expliquant l'échec des tentatives précédentespour construire une sémantique dénotationnelle pour de tels langages. La sémantique de jeux présentée dans cette thèseest la première sémantique dénotationnelle pour de telslambda-calculs équipés de types et d'opérations supplémentairespermettant la programmation d'algorithmes quantiques. Les résultatsprésentés valident les deux approches différentes utilitées dans laconception de ces deux nouveaux languages d'ordre supérieur: une premièreoù les états quantiques sont indirectement accessibles via desréférences et une seconde où ils sont introduit directement comme desconstantes dans le langage. Les stratégies quantiques présentéespermettent de comprendre les contraintes devant êtreimposées aux systèmes de type quantique comportant des types d'ordresupérieurs. La contrainte la plus importante est le fait que l'abstractionsur une partie d'un état quantique comportant plusieurs qbits inconnus doitêtre prohibée. Les stratégies quantiques constituent un nouveau modèle mathématique quidécrit l'interaction entre les données classiques et quantiques par desdialogues entre système et environnement. L'interaction entre les differentespar
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Mims, Mark McGrew. "Dynamical stability of quantum algorithms /". Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004342.
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Janzing, Dominik. "Computer science approach to quantum control". Karlsruhe : Univ.-Verl. Karlsruhe, 2006. http://www.uvka.de/univerlag/volltexte/2006/175/.
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Hansen, Rasmus Hvass. "Towards the nuclear spin quantum computer". Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442465.
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Maguire, Yael G. 1975. "Towards a table top quantum computer". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/61842.
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Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 1999.Includes bibliographical references (leaves 135-139).
In the early 1990s, quantum computing proved to be an enticing theoretical possibility but a extremely difficult experimental challenge. Two advances have made experimental quantum computing demonstrable: Quantum error correction; and bulk, thermal quantum computing using nuclear magnetic resonance (NMR). Simple algorithms have been implemented on large, commercial NMR spectrometers that are expensive and cumbersome. The goal of this project is to construct a table-top quantum computer that can match and eventually exceed the performance of commercial machines. This computer should be an inexpensive, easy-to-use machine that can be considered more a computer than its "supercomputer" counterparts. For this thesis, the goal is to develop a low-cost, table-top quantum computer capable of implementing simple quantum algorithms demonstrated thus far in the community, but is also amenable to the many scaling issues of practical quantum computing. Understanding these scaling issues requires developing a theoretical understanding of the signal enhancement techniques and fundamental noise sources of this powerful but delicate system. Complementary to quantum computing, this high performance but low cost NMR machine will be useful for a number of medical, low cost sensing and tagging applications due the unique properties of NMR: the ability to sense and manipulate the information content of materials on macroscopic and microscopic scales.
Yael G. Maguire.
S.M.
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Lukac, Martin. "Quantum Inductive Learning and Quantum Logic Synthesis". PDXScholar, 2009. https://pdxscholar.library.pdx.edu/open_access_etds/2319.
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Since Quantum Computer is almost realizable on large scale and Quantum Technology is one of the main solutions to the Moore Limit, Quantum Logic Synthesis (QLS) has become a required theory and tool for designing Quantum Logic Circuits. However, despite its growth, there is no any unified aproach to QLS as Quantum Computing is still being discovered and novel applications are being identified.
The intent of this study is to experimentally explore principles of Quantum Logic Synthesis and its applications to Inductive Machine Learning. Based on algorithmic approach, I first design a Genetic Algorithm for Quantum Logic Synthesis that is used to prove and verify the methods proposed in this work.
Based on results obtained from the evolutionary experimentation, I propose a fast, structure and cost based exhaustive search that is used for the design of a novel, least expensive universal family of quantum gates.
The results form both the evolutionary and heuristic search are used to formulate an Inductive Learning Approach based on Quantum Logic Synthesis with the intended application being the humanoid behavioral robotics.
The presented approach illustrates a successful algorithmic approach, where the search algorithm was able to invent/discover novel quantum circuits as well as novel principles in Quantum Logic Synthesis.
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Babar, Zunaira. "Quantum error correction codes". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/380165/.
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Quantum parallel processing techniques are capable of solving certain complex problems at a substantially lower complexity than their classical counterparts. From the perspective of telecommunications, this quantum-domain parallel processing provides a plausible solution for achieving full-search based multi-stream detection, which is vital for future gigabit-wireless systems. The peculiar laws of quantum mechanics have also spurred interest in the absolutely secure quantum-based communication systems. Unfortunately, quantum decoherence imposes a hitherto insurmountable impairment on the practical implementation of quantum computation as well as on quantum communication systems, which may be overcome with the aid of efficient error correction codes. In this thesis, we design error correction codes for the quantum domain, which is an intricate journey from the realm of classical channel coding theory to that of the Quantum Error Correction Codes (QECCs). Since quantum-based communication systems are capable of supporting the transmission of both classical and quantum information, we initially focus our attention on the code design for entanglementassisted classical communication over the quantum depolarizing channel. We conceive an Extrinsic Information Transfer (EXIT) chart aided near-capacity classical-quantum code design, which invokes a classical Irregular Convolutional Code (IRCC) and a Unity Rate Code (URC) in conjunction with our proposed soft-decision aided SuperDense Code (SD). Hence, it is referred to as an ‘IRCC-URCSD’ arrangement. The proposed scheme is intrinsically amalgamated both with 2-qubit as well as 3-qubit SD coding protocols and it is benchmarked against the corresponding entanglement-assisted classical capacity. Since the IRCC-URC-SD scheme is a bit-based design, it incurs a capacity loss. As a further advance, we design a symbol based concatenated code design, referred to as a symbol-based ‘CC-URC-SD’, which relies on a single-component classical Convolutional Code (CC). Additionally, for the sake of reducing the associated decoding complexity, we also investigate the impact of the constraint length of the convolutional code on the achievable performance. Our initial designs, namely IRCC-URC-SD and CC-URC-SD, exploit redundancy in the classical domain. By contrast, QECCs relying on the quantum-domain redundancy are indispensable for conceiving a quantum communication system supporting the transmission of quantum information and also for quantum computing. Therefore, we next provide insights into the transformation from the family of classical codes to the class of quantum codes known as ‘Quantum Stabilizer Codes’ (QSC), which invoke the classical syndrome decoding. Particularly, we detail the underlying quantum-to classical isomorphism, which facilitates the design of meritorious families of QECCs from the known classical codes. We further study the syndrome decoding techniques operating over classical channels, which may be exploited for decoding QSCs. In this context, we conceive a syndrome-based block decoding approach for the classical Turbo Trellis Coded Modulation (TTCM), whose performance is investigated for transmission over an Additive White Gaussian Noise (AWGN) channel as well as over an uncorrelated Rayleigh fading channel. Pursuing our objective of designing efficient QECCs, we next consider the construction of Hashingbound-approaching concatenated quantum codes. In this quest, we appropriately adapt the conventional non-binary EXIT charts for Quantum Turbo Codes (QTCs) by exploiting the intrinsic quantumto- classical isomorphism. We further demonstrate the explicit benefit of our EXIT-chart technique for achieving a Hashing-bound-approaching code design. We also propose a generically applicable structure for Quantum Irregular Convolutional Codes (QIRCCs), which can be dynamically adapted to a specific application scenario with the aid of the EXIT charts. More explicitly, we provide a detailed design example by constructing a 10-subcode QIRCC and use it as an outer code in a concatenated quantum code structure for evaluating its performance. Working further in the direction of iterative code structures, we survey Quantum Low Density Parity Check (QLPDC) codes from the perspective of code design as well as in terms of their decoding algorithms. Furthermore, we propose a radically new class of high-rate row-circulant Quasi-Cyclic QLDPC (QC-QLDPC) codes, which can be constructed from arbitrary row-circulant classical QC LDPC matrices. We also conceive a modified non-binary decoding algorithm for homogeneous Calderbank-Shor-Steane (CSS)-type QLDPC codes, which is capable of alleviating the problems imposed by the unavoidable length-4 cycles. Our modified decoder outperforms the state-of-the-art decoders in terms of their Word Error Rate (WER) performance, despite imposing a reduced decoding complexity. Finally, we intricately amalgamate our modified decoder with the classic Uniformly-ReWeighted Belief Propagation (URW-BP) for the sake of achieving further performance improvement.
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Huang, Wei-Han 1979. "Instrumentation for quantum computers". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/30104.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2004.Includes bibliographical references (p. 209-215).
Quantum computation poses challenging engineering and basic physics issues for the control of nanoscale systems. In particular, experimental realizations of up to seven-qubit NMR quantum computers have acutely illustrated how quantum circuits require extremely precise control instrumentation for pulsed excitation. In this thesis, we develop two general-purpose, low-cost pulse programmers and two Class E power amplifiers, designed for precise control of qubits and complex pulse excitation. The first-generation pulse programmer has timing resolutions of 235 ns, while the second-generation one has resolutions of 10 ns. The Class E power amplifier has [mu]s transient response times, a high quality-factor, and a small form factor. The verification of the pulse programmer and the Class E power amplifier is demonstrated using a customized nuclear quadrupole resonance (NQR) spectrom- eter, which incorporates both devices. The two devices control the generation of RF pulses used in NQR experiments on paradichlorobenzene (C₆H₄C₁₂) and sodium nitrite (NaNO₂). The NQR signals originating from ¹⁴N in sodium nitrite and from ³⁵Cl in paradichlorobenzene are measured using the NQR spectrometer. The pulse programmer and the Class E power amplifier represent first steps towards development of practical NMR quantum computers.
by Wei-Han Huang.
S.M.
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Brandhorst-Satzkorn, Johan. "A Review of Freely Available Quantum Computer Simulation Software". Thesis, Linköpings universitet, Matematik och tillämpad matematik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78650.
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A study has been made of a few different freely available Quantum Computer simulators.All the simulators tested are available online on their respective websites. A number oftests have been performed to compare the different simulators against each other. Someuntested simulators of various programming languages are included to show the diversityof the quantum computer simulator applications. The conclusion of the review is that LibQuantum is the best of the simulatorstested because of ease of coding, a great amount of pre-defined functionimplementations and decoherence simulation support among other reasons.
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Ardeshir-Larijani, Ebrahim. "Automated equivalence checking of quantum information systems". Thesis, University of Warwick, 2014. http://wrap.warwick.ac.uk/63940/.
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Quantum technologies have progressed beyond the laboratory setting and are beginning to make an impact on industrial development. The construction of practical, general purpose quantum computers has been challenging, to say the least. But quantum cryptographic and communication devices have been available in the commercial marketplace for a few years. Quantum networks have been built in various cities around the world, and plans are afoot to launch a dedicated satellite for quantum communication. Such new technologies demand rigorous analysis and verification before they can be trusted in safety and security-critical applications. In this thesis we investigate the theory and practice of equivalence checking of quantum information systems. We present a tool, Quantum Equivalence Checker (QEC), which uses a concurrent language for describing quantum systems, and performs verification by checking equivalence between specification and implementation. For our process algebraic language CCSq, we define an operational semantics and a superoperator semantics. While in general, simulation of quantum systems using current computing technology is infeasible, we restrict ourselves to the stabilizer formalism, in which there are efficient simulation algorithms and representation of quantum states. By using the stabilizer representation of quantum states we introduce various algorithms for testing equality of stabilizer states. In this thesis, we consider concurrent quantum protocols that behave functionally in the sense of computing a deterministic input-output relation for all interleavings of a concurrent system. Crucially, these input-output relations can be abstracted by superoperators, enabling us to take advantage of linearity. This allows us to analyse the behaviour of protocols with arbitrary input, by simulating their operation on a finite basis set consisting of stabilizer states. We present algorithms for the checking of functionality and equivalence of quantum protocols. Despite the limitations of the stabilizer formalism and also the range of protocols that can be analysed using equivalence checking, QEC is applied to specify and verify a variety of interesting and practical quantum protocols from quantum communication and quantum cryptography to quantum error correction and quantum fault tolerant computation, where for each protocol different sequential and concurrent model are defined in CCSq. We also explain the implementation details of the QEC tool and report on the experimental results produced by using it on the verification of a number of case studies.
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Zuccon, Guido. "Document ranking with quantum probabilities". Thesis, University of Glasgow, 2012. https://eprints.qut.edu.au/69287/1/zuccon2012b.pdf.
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In this thesis we investigate the use of quantum probability theory for ranking documents. Quantum probability theory is used to estimate the probability of relevance of a document given a user's query. We posit that quantum probability theory can lead to a better estimation of the probability of a document being relevant to a user's query than the common approach, i. e. the Probability Ranking Principle (PRP), which is based upon Kolmogorovian probability theory. Following our hypothesis, we formulate an analogy between the document retrieval scenario and a physical scenario, that of the double slit experiment. Through the analogy, we propose a novel ranking approach, the quantum probability ranking principle (qPRP). Key to our proposal is the presence of quantum interference. Mathematically, this is the statistical deviation between empirical observations and expected values predicted by the Kolmogorovian rule of additivity of probabilities of disjoint events in configurations such that of the double slit experiment. We propose an interpretation of quantum interference in the document ranking scenario, and examine how quantum interference can be effectively estimated for document retrieval.
To validate our proposal and to gain more insights about approaches for document ranking, we
(1) analyse PRP, qPRP and other ranking approaches, exposing the assumptions underlying their ranking criteria and formulating the conditions for the optimality of the two ranking principles,
(2) empirically compare three ranking principles (i. e. PRP, interactive PRP, and qPRP) and two state-of-the-art ranking strategies in two retrieval scenarios, those of ad-hoc retrieval and diversity retrieval,
(3) analytically contrast the ranking criteria of the examined approaches, exposing similarities and differences,
(4) study the ranking behaviours of approaches alternative to PRP in terms of the kinematics they impose on relevant documents, i. e. by considering the extent and direction of the movements of relevant documents across the ranking recorded when comparing PRP against its alternatives.
Our findings show that the effectiveness of the examined ranking approaches strongly depends upon the evaluation context. In the traditional evaluation context of ad-hoc retrieval, PRP is empirically shown to be better or comparable to alternative ranking approaches. However, when we turn to examine evaluation contexts that account for interdependent document relevance (i. e. when the relevance of a document is assessed also with respect to other retrieved documents, as it is the case in the diversity retrieval scenario) then the use of quantum probability theory and thus of qPRP is shown to improve retrieval and ranking effectiveness over the traditional PRP and alternative ranking strategies, such as Maximal Marginal Relevance, Portfolio theory, and Interactive PRP.
This work represents a significant step forward regarding the use of quantum theory in information retrieval. It demonstrates in fact that the application of quantum theory to problems within information retrieval can lead to improvements both in modelling power and retrieval effectiveness, allowing the constructions of models that capture the complexity of information retrieval situations.
Furthermore, the thesis opens up a number of lines for future research. These include:
(1) investigating estimations and approximations of quantum interference in qPRP;
(2) exploiting complex numbers for the representation of documents and queries, and;
(3) applying the concepts underlying qPRP to tasks other than document ranking.
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Zuccon, Guido. "Document ranking with quantum probabilities". Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3463/.
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In this thesis we investigate the use of quantum probability theory for ranking documents. Quantum probability theory is used to estimate the probability of relevance of a document given a user's query. We posit that quantum probability theory can lead to a better estimation of the probability of a document being relevant to a user's query than the common approach, i.e. the Probability Ranking Principle (PRP), which is based upon Kolmogorovian probability theory. Following our hypothesis, we formulate an analogy between the document retrieval scenario and a physical scenario, that of the double slit experiment. Through the analogy, we propose a novel ranking approach, the quantum probability ranking principle (qPRP). Key to our proposal is the presence of quantum interference. Mathematically, this is the statistical deviation between empirical observations and expected values predicted by the Kolmogorovian rule of additivity of probabilities of disjoint events in configurations such that of the double slit experiment. We propose an interpretation of quantum interference in the document ranking scenario, and examine how quantum interference can be effectively estimated for document retrieval. To validate our proposal and to gain more insights about approaches for document ranking, we (1) analyse PRP, qPRP and other ranking approaches, exposing the assumptions underlying their ranking criteria and formulating the conditions for the optimality of the two ranking principles, (2) empirically compare three ranking principles (i.e. PRP, interactive PRP, and qPRP) and two state-of-the-art ranking strategies in two retrieval scenarios, those of ad-hoc retrieval and diversity retrieval, (3) analytically contrast the ranking criteria of the examined approaches, exposing similarities and differences, (4) study the ranking behaviours of approaches alternative to PRP in terms of the kinematics they impose on relevant documents, i.e. by considering the extent and direction of the movements of relevant documents across the ranking recorded when comparing PRP against its alternatives. Our findings show that the effectiveness of the examined ranking approaches strongly depends upon the evaluation context. In the traditional evaluation context of ad-hoc retrieval, PRP is empirically shown to be better or comparable to alternative ranking approaches. However, when we turn to examine evaluation contexts that account for interdependent document relevance (i.e. when the relevance of a document is assessed also with respect to other retrieved documents, as it is the case in the diversity retrieval scenario) then the use of quantum probability theory and thus of qPRP is shown to improve retrieval and ranking effectiveness over the traditional PRP and alternative ranking strategies, such as Maximal Marginal Relevance, Portfolio theory, and Interactive PRP. This work represents a significant step forward regarding the use of quantum theory in information retrieval. It demonstrates in fact that the application of quantum theory to problems within information retrieval can lead to improvements both in modelling power and retrieval effectiveness, allowing the constructions of models that capture the complexity of information retrieval situations. Furthermore, the thesis opens up a number of lines for future research. These include (1) investigating estimations and approximations of quantum interference in qPRP, (2) exploiting complex numbers for the representation of documents and queries, and (3) applying the concepts underlying qPRP to tasks other than document ranking.
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Devitt, Simon John. "Quantum information engineering : concepts to quantum technologies /". Connect to thesis, 2007. http://eprints.unimelb.edu.au/archive/00003925.
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Cross, Andrew W. (Andrew William) 1979. "Fault-tolerant quantum computer architectures using hierarchies of quantum error-correcting codes". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44407.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 221-238).
Quantum computers have been shown to efficiently solve a class of problems for which no efficient solution is otherwise known. Physical systems can implement quantum computation, but devising realistic schemes is an extremely challenging problem largely due to the effect of noise. A quantum computer that is capable of correctly solving problems more rapidly than modern digital computers requires some use of so-called fault-tolerant components. Code-based fault-tolerance using quantum error-correcting codes is one of the most promising and versatile of the known routes for fault-tolerant quantum computation. This dissertation presents three main, new results about code-based fault-tolerant quantum computer architectures. The first result is a large new family of quantum codes that go beyond stabilizer codes, the most well-studied family of quantum codes. Our new family of codeword stabilized codes contains all known codes with optimal parameters. Furthermore, we show how to systematically find, construct, and understand such codes as a pair of codes: an additive quantum code and a classical (nonlinear) code. Second, we resolve an open question about universality of so-called transversal gates acting on stabilizer codes. Such gates are universal for classical fault-tolerant computation, but they were conjectured to be insufficient for universal fault-tolerant quantum computation. We show that transversal gates have a restricted form and prove that some important families of them cannot be quantum universal. This is strong evidence that so-called quantum software is necessary to achieve universality, and, therefore, fault-tolerant quantum computer architecture is fundamentally different from classical computer architecture. Finally, we partition the fault-tolerant design problem into levels of a hierarchy of concatenated codes and present methods, compatible with rigorous threshold theorems, for numerically evaluating these codes.
(cont.) The methods are applied to measure inner error-correcting code performance, as a first step toward elucidation of an effective fault-tolerant quantum computer architecture that uses no more than a physical, inner, and outer level of coding. Of the inner codes, the Golay code gives the highest pseudothreshold of 2 x 10-3. A comparison of logical error rate and overhead shows that the Bacon-Shor codes are competitive with Knill's C₄/C₆ scheme at a base error rate of 10⁻⁴.
by Andrew W. Cross.
Ph.D.
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Raynaud, Guillaume. "Fibred contextual quantum physics". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/1685/.
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Inspired by the recast of the quantum mechanics in a toposical framework, we develop a contextual quantum mechanics via the geometric mathematics to propose a quantum contextuality adaptable in every topos. The contextuality adopted corresponds to the belief that the quantum world must only be seen from the classical viewpoints à la Bohr consequently putting forth the notion of a context, while retaining a realist understanding. Mathematically, the cardinal object is a spectral Stone bundle Σ → B (between stably-compact locales) permitting a treatment of the kinematics, fibre by fibre and fully point-free. In leading naturally to a new notion of points, the geometricity permits to understand those of the base space B as the contexts C — the commutative C*–algebras of a incommutative C*–algebras — and those of the spectral locale Σ as the couples (C, ψ), with ψ a state of the system from the perspective of such a C. The contexts are furnished with a natural order, the aggregation order which is installed as the specialization on B and Σ thanks to (one part of) the Priestley's duality adapted geometrically as well as to the effectuality of the lax descent of the Stone bundles along the perfect maps.
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Desrosiers, Simon Pierre. "Quantum entropic security". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95620.
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We present full generalizations of entropic security and entropic indistinguishability,notions introduced by Russell and Wang and then Dodis and Smith, to the quantumworld where no assumption other than a limit on the knowledge of the adversary ismade. This limit is quantified using the quantum conditional min-entropy as introducedby Renner. In this fully generalized model, we allow any kind of entanglementor correlation between the Sender and the Eavesdropper.A proof of equivalence between the two security definitions is presented. This proofof equivalence is much simpler and more powerful than what was previously doneand is by itself a worthy contribution. We also provide proofs of security for twodifferent ciphers in this model. These ciphers generalize existing schemes for approximatequantum encryption to the entropic security model. The key length requirementof these two schemes is exactly the same as their classical counterparts for separablestates. It is also, as far as we know, the first time that one can prove securityfor encryption schemes while allowing entanglement with the adversary and yet notrequiring perfect security .Une généralisation complète des notions de sécurité entropique et d'indistinguabilitéentropique, telles que définies par Russell et Wang puis par Dodis et Smith, aumonde quantique est présentée. Aucune autre hypothèse qu'une borne inférieure surl'incertitude de l'adversaire, incertitude quantifiée par la notion de min-entropie conditionellequantique telle que définie par Renner, n'est présumée. Ce modèle permettoute forme de corrélation ou d'intrication entre l'adversaire et l'émetteur du message.Une démonstration de l'équivalence entre ces deux notions de sécurité est présentéequi est beaucoup plus simple que ce qui était connue au-paravant. Cette nouvellesimplicité est une contribution notable. Deux chiffres sont aussi généralisés à ce nouveaumodèle de sécurité et leur sécurité est démontrée. La taille de la clef requise afind'assurer la sécurité de ces deux chiffres est exactement la même que celle requise parleur équivalent classique. Ces chiffres sont sécuritaires même en présence d'intricationentre l'adversaire et l'émetteur, ce qui est, autant que nous le sachions, une premièresans requérir une sécurité parfaite.
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Grattage, Jonathan James. "A functional quantum programming language". Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10250/.
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This thesis introduces the language QML, a functional language for quantum computations on finite types. QML exhibits quantum data and control structures, and integrates reversible and irreversible quantum computations. The design of QML is guided by the categorical semantics: QML programs are interpreted by morphisms in the category FQC of finite quantum computations, which provides a constructive operational semantics of irreversible quantum computations, realisable as quantum circuits. The quantum circuit model is also given a formal categorical definition via the category FQC. QML integrates reversible and irreversible quantum computations in one language, using first order strict linear logic to make weakenings, which may lead to the collapse of the quantum wavefunction, explicit. Strict programs are free from measurement, and hence preserve superpositions and entanglement. A denotational semantics of QML programs is presented, which maps QML terms into superoperators, via the operational semantics, made precise by the category Q. Extensional equality for QML programs is also presented, via a mapping from FQC morphisms into the category Q.
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Botsinis, Panagiotis. "Quantum-assisted multi-user wireless systems". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/381235/.
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The high complexity of numerous optimal classical communication schemes, such as the Maximum Likelihood (ML) and Maximum A posteriori Probability (MAP) Multi-User Detector (MUD) designed for coherent detection or the ML and MAP Multiple-Symbol Differential Detectors (MSDD) conceived for non-coherent receivers often prevents their practical implementation. In this thesis we commence with a review and tutorial on Quantum Search Algorithms (QSA) and propose a number of hard-output and iterative Quantum-assisted MUDs (QMUD) and MSDDs (QMSDD). We employ a QSA, termed as the Durr-Hyer Algorithm (DHA) that finds the minimum of a function in order to perform near-optimal detection with quadratic reduction in the computational complexity, when compared to that of the ML MUD / MSDD. Two further techniques conceived for reducing the complexity of the DHA-based Quantum-assisted MUD (QMUD) are also proposed. These novel QMUDs / QMSDDs are employed in the uplink of various multiple access systems, such as Direct Sequence Code Division Multiple Access systems, Space Division Multiple Access systems as well as in Direct-Sequence Spreading and Slow Subcarrier Hopping SDMA systems amalgamated with Orthogonal Frequency Division Multiplexing and Interleave Division Multiple Access systems. Furthermore, we follow a quantum approach to achieve the same performance as the optimal Soft Input Soft-Output (SISO) classical detectors by replacing them with a quantum algorithm, which estimates the weighted sum of all the evaluations of a function. We propose a SISO QMUD / QMSDD scheme, which is the quantum-domain equivalent of the MAP MUD / MSDD. Both our EXtrinsic Information Transfer (EXIT) charts and Bit Error Ratio (BER) curves show that the computational complexity of the proposed QMUD / QMSDD is significantly lower than that of the MAP MUD / MSDD, whilst their performance remains equivalent. Moreover, we propose two additional families of iterative DHA-based QMUD / QMSDDs for performing near-optimal MAP detection exhibiting an even lower tunable complexity than the QWSA QMUD. Several variations of the proposed QMUD / QMSDDs have been developed and they are shown to perform better than the state-of-the-art low-complexity MUDs / MSDDs at a given complexity. Their iterative decoding performance is investigated with the aid of non-Gaussian EXIT charts.
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Nicholson, Lori Eileen. "Quantum Algorithm Animator". NSUWorks, 2010. http://nsuworks.nova.edu/gscis_etd/262.
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The design and development of quantum algorithms present a challenge, especially for inexperienced computer science students. Despite the numerous common concepts with classical computer science, quantum computation is still considered a branch of theoretical physics not commonly used by computer scientists. Experimental research into the development of a quantum computer makes the use of quantum mechanics in organizing computation more attractive, however the physical realization of a working quantum computer may still be decades away.
This study introduces quantum computing to computer science students using a quantum algorithm animator called QuAL. QuAL's design uses features common to classical algorithm animators guided by an exploratory study but refined to animate the esoteric and interesting aspects of quantum algorithms.
In addition, this study investigates the potential for the animation of a quantum sorting algorithm to help novice computer science students understand the formidable concepts of quantum computing. The animations focus on the concepts required to understand enough about quantum algorithms to entice student interest and promote the integration of quantum computational concepts into computer science applications and curricula.
The experimental case study showed no significant improvement in student learning when using QuAL's initial prototype. Possible reasons include the animator's presentation of concepts and the study's pedagogical framework such as choice of algorithm (Wallace and Narayanan's sorting algorithm), design of pre- and post tests, and the study's small size (20 students) and brief duration (2 hours). Nonetheless, the animation system was well received by students. Future work includes enhancing this animation tool for illustrating elusive concepts in quantum computing.
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Barenco, Adriano. "Quantum computation". Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360152.
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Copsey, Dean Elbert. "Designing scalable quantum computer architectures : layout and initialization /". For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2005. http://uclibs.org/PID/11984.
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Mower, Jacob. "Photonic quantum computers and communication systems". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/103851.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 123-137).
Quantum information processors have been proposed to solve classically intractable or unsolvable problems in computing, sensing, and secure communication. There has been growing interest in photonic implementations of quantum processors as they offer relatively long coherence lengths, precise state manipulation, and efficient measurement. In this thesis, we first present experimental techniques to generate on-chip, photonic quantum processors and then discuss protocols for fast and secure quantum communication. In particular, we describe how -to combine the outputs of multiple stochastic single-photon sources using a photonic integrated circuit to generate an efficient source of single photons. We then show designs for silicon-based quantum photonic processors that can be programmed to implement a large class of existing quantum algorithms and can lead to quicker testing of new algorithms than was previously possible. We will then present the integration of large numbers of high-efficiency, low-timing jitter single-photon detectors onto a silicon photonic integrated circuit. To conclude, we will present a quantum key distribution protocol that uses the robust temporal degree of freedom of entangled photons to enable fast, secure key exchange, as well as experimental results for implementing key distribution protocols using silicon photonic integrated circuits.
by Jacob Mower.
Ph. D.
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Anderzén, Rodenkirchen Sven, i Marcus Granström. "Performance evaluation of quantum Fourier transform on a modern quantum device". Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229682.
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Quantum computing has in the last decades gone from a purely theoretical concept to being implemented on actual devices in the real world. However, one of the major challenges of quantum computing still remains; its sensitivity to noise. Great progress has been made in the last couple of years in reducing the effects of noise on a quantum computation which raises the question of how good a non error corrected quantum computation actually performs on a modern quantum device. In this work we perform quantum Fourier transform, a common operation found in many quantum algorithms on a real quantum device, the IBMQX4. We compare the results obtained from the real quantum device against the same error-free results obtained through simulation and measure the impact the error has had on the period. We show that although it is possible to distinguish a correct result for trivial problem instances, error caused by noise is still to large to obtain a correct result for any non-trivial problems. We conclude that quantum error correcting techniques are a necessity for quantum computations of any non-trivial problem size.Kvantberäkningar har under de senaste decennierna gått från att vara ett teoretiskt koncept till att implementeras på riktiga enheter. En stor utmaning finns dock kvar; kvantdatorernas känslighet för störningar. Under de senaste åren har stora framsteg gjorts för att minska påverkan av störningar i kvantberäkningar vilket öppnar upp för frågan; hur bra fungerar en icke-felrättande kvantberäkning på en modern kvantdator? I detta arbete utför vi kvant-Fouriertransform, en vanlig operation i många kvantalgoritmer, på den riktig kvantdatorn IBMQX4. Vi jämför resultaten från den riktiga kvantdatorn mot felfria simuleringar och mäter den inverkan felen haft på perioden. Vi visar att även om det är möjligt att urskilja ett korrekt resultat för triviala probleminstanser så är fel orsakat av störningar fortfarande för stort för att erhålla ett korrekt resultat för icke-triviala problem. Vi fastställer att tekniker för felkorrigering inom kvantberäkningar är en nödvändighet för icke-triviala probleminstanser.
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Venkatraman, Dheera. "Quantum-mimetic imaging". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97762.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 139-146).
Many recent experiments have explored the use of nonclassical states of light to perform imaging or sensing. Although these experiments require quantum descriptions of light to explain their behavior, the advantages they claim are not necessarily unique to quantum light. This thesis explores the underlying principles behind two of those imaging techniques and realizes classical experiments that demonstrate properties similar to their quantum counterparts. The principal contributions of this thesis in the preceding quantum-mimetic imaging paradigm are the experimental implementation of phase-conjugate optical coherence tomography and phase-sensitive ghost imaging, two experiments whose quantum counterparts utilize phase-sensitive light with nonclassical strength. This thesis also explores the use of compressed sensing to further speed up acquisition of ghost imaging. Finally, a new paradigm inspired by compressed sensing is demonstrated, in which high-quality depth and reflectivity images are simultaneously captured using only the first photon arrival at each pixel. This paradigm is also extended to the case of single-photon APD arrays which may offer few-photon low-light imaging capabilities beyond what is possible with current camera technologies.
by Dheera Venkatraman.
Ph. D.
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Eldar, Yonina Chana 1973. "Quantum signal processing". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/16805.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2002.Includes bibliographical references (p. 337-346).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Quantum signal processing (QSP) as formulated in this thesis, borrows from the formalism and principles of quantum mechanics and some of its interesting axioms and constraints, leading to a novel paradigm for signal processing with applications in areas ranging from frame theory, quantization and sampling methods to detection, parameter estimation, covariance shaping and multiuser wireless communication systems. The QSP framework is aimed at developing new or modifying existing signal processing algorithms by drawing a parallel between quantum mechanical measurements and signal processing algorithms, and by exploiting the rich mathematical structure of quantum mechanics, but not requiring a physical implementation based on quantum mechanics. This framework provides a unifying conceptual structure for a variety of traditional processing techniques, and a precise mathematical setting for developing generalizations and extensions of algorithms. Emulating the probabilistic nature of quantum mechanics in the QSP framework gives rise to probabilistic and randomized algorithms. As an example we introduce a probabilistic quantizer and derive its statistical properties. Exploiting the concept of generalized quantum measurements we develop frame-theoretical analogues of various quantum-mechanical concepts and results, as well as new classes of frames including oblique frame expansions, that are then applied to the development of a general framework for sampling in arbitrary spaces. Building upon the problem of optimal quantum measurement design, we develop and discuss applications of optimal methods that construct a set of vectors.
(cont.) We demonstrate that, even for problems without inherent inner product constraints, imposing such constraints in combination with least-squares inner product shaping leads to interesting processing techniques that often exhibit improved performance over traditional methods. In particular, we formulate a new viewpoint toward matched filter detection that leads to the notion of minimum mean-squared error covariance shaping. Using this concept we develop an effective linear estimator for the unknown parameters in a linear model, referred to as the covariance shaping least-squares estimator. Applying this estimator to a multiuser wireless setting, we derive an efficient covariance shaping multiuser receiver for suppressing interference in multiuser communication systems.
by Yonina Chana Eldar.
Ph.D.
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Patino, Alberto. "Reversible Logic Synthesis Using a Non-blocking Order Search". PDXScholar, 2010. https://pdxscholar.library.pdx.edu/open_access_etds/162.
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Reversible logic is an emerging area of research. With the rapid growth of markets such as mobile computing, power dissipation has become an increasing concern for designers (temperature range limitations, generating smaller transistors) as well as customers (battery life, overheating). The main benefit of utilizing reversible logic is that there exists, theoretically, zero power dissipation. The synthesis of circuits is an important part of any design cycle. The circuit used to realize any specification must meet detailed requirements for both layout and manufacturing. Quantum cost is the main metric used in reversible logic. Many algorithms have been proposed thus far which result in both low gate count and quantum cost. In this thesis the AP algorithm is introduced. The goal of the algorithm is to drive quantum cost down by using multiple non-blocking orders, a breadth first search, and a quantum cost reduction transformation. The results shown by the AP algorithm demonstrate that the resulting quantum cost for well-known benchmarks are improved by at least 9% and up to 49%.
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Hnatenko, O. S. "Quantum computing. Quantum information technologies as the basis for future learning platforms". Thesis, ISMA University of Applied Science, Riga, Latvia, 2021. https://openarchive.nure.ua/handle/document/16270.
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This paper presents the place of quantum technologies in the modern information world. The technique of quantum computing is described. Also presented is a new model of a qubit based on a nanolaser with frequency stabilization, which emits at different wavelengths, which corresponds to its different states. Thus, the work proposes a scheme of a qubit, which underlies quantum technologies and quantum computers. Quantum computing is a thousand times faster than existing ones. In the future this technology will be able to solve problems that are beyond the power of modern computers, which means it will become the basis for learning and understanding the world more broadly.
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Welch, Jonathan M. "On the Synthesis of Quantum Circuits for Diagonal Operators in Quantum Computation". Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:23845468.
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Diagonal unitary operators are commonly found in many quantum algorithms. They find application as analytical potential operators for quantum simulation, as well as for complex oracles used in quantum searches. However, in order to implement a quantum algorithm on a given quantum device, each operator must be decomposed into a sequence of fault-tolerant, device-level instructions. In general, to implement an $n$-qubit diagonal unitary {\em exactly} on a quantum computer generally requires $2^{n+1}-3$ one- and two-qubit gates. However, for most practical implementations of diagonal unitaries, some degree of approximation will be necessary if the circuit is to be efficient. In this thesis we develop two complementary methods for the approximate synthesis of quantum circuits for diagonal unitaries. We show how to apply these techniques to real-space quantum simulation and show how efficient high fidelity quantum simulations can be implemented with low-depth quantum circuits.Engineering and Applied Sciences - Applied Physics
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Schneider, Scott (Scott David) 1978. "Quantum Systems Simulator". Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86873.
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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science; and, (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2000.Includes bibliographical references (leaf 41).
by Scott Schneider.
M.Eng.and S.B.
S.B.
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Janzing, Dominik [Verfasser]. "Computer science approach to quantum control / von Dominik Janzing". Karlsruhe : Univ.-Verl. Karlsruhe, 2006. http://d-nb.info/982614721/34.
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Cox, Hazel. "The quantum-mechanical three-body problem using computer algebra". Thesis, University of York, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239780.
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Cross, Andrew W. (Andrew William) 1979. "Synthesis and evaluation of fault-tolerant quantum computer architectures". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/30175.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (p. 241-247).
Fault-tolerance is the cornerstone of practical, large-scale quantum computing, pushed into its prominent position with heroic theoretical efforts. The fault-tolerance threshold, which is the component failure probability below which arbitrarily reliable quantum computation becomes possible, is one standard quality measure of fault-tolerant designs based on recursive simulation. However, there is a gulf between theoretical achievements and the physical reality and complexity of envisioned quantum computing systems. This thesis takes a step toward bridging that gap. We develop a new experimental method for estimating fault-tolerance thresholds that applies to realistic models of quantum computer architectures, and demonstrate this technique numerically. We clarify a central problem for experimental approaches to fault-tolerance evaluation--namely, distinguishing between potentially optimistic pseudo-thresholds and actual thresholds that determine scalability. Next, we create a system architecture model for the trapped-ion quantum computer, discuss potential layouts, and numerically estimate the fault-tolerance threshold for this system when it is constrained to a local layout. Finally, we place the problem of evaluation and synthesis of fault-tolerant quantum computers into a broader framework by considering a software architecture for quantum computer design.
by Andrew W. Cross.
S.M.
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SILVA, Adenilton José da. "Artificial neural network architecture selection in a quantum computer". UNIVERSIDADE FEDERAL DE PERNAMBUCO, 2015. https://repositorio.ufpe.br/handle/123456789/15011.
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CNPq
Miniaturisation of computers components is taking us from classical to quantum physics domain. Further reduction in computer components size eventually will lead to the development of computer systems whose components will be on such a small scale that quantum physics intrinsic properties must be taken into account. The expression quantum computation and a first formal model of a quantum computer were first employed in the eighties. With the discovery of a quantum algorithm for factoring exponentially faster than any known classical algorithm in 1997, quantum computing began to attract industry investments for the development of a quantum computer and the design of novel quantum algorithms. For instance, the development of learning algorithms for neural networks. Some artificial neural networks models can simulate an universal Turing machine, and together with learning capabilities have numerous applications in real life problems. One limitation of artificial neural networks is the lack of an efficient algorithm to determine its optimal architecture. The main objective of this work is to verify whether we can obtain some advantage with the use of quantum computation techniques in a neural network learning and architecture selection procedure. We propose a quantum neural network, named quantum perceptron over a field (QPF). QPF is a direct generalisation of a classical perceptron which addresses some drawbacks found in previous models for quantum perceptrons. We also present a learning algorithm named Superposition based Architecture Learning algorithm (SAL) that optimises the neural network weights and architectures. SAL searches for the best architecture in a finite set of neural network architectures and neural networks parameters in linear time over the number of examples in the training set. SAL is the first quantum learning algorithm to determine neural network architectures in linear time. This speedup is obtained by the use of quantum parallelism and a non linear quantum operator.
A miniaturização dos componentes dos computadores está nos levando dos domínios da física clássica aos domínios da física quântica. Futuras reduções nos componentes dos computadores eventualmente levará ao desenvolvimento de computadores cujos componentes estarão em uma escala em que efeitos intrínsecos da física quântica deverão ser considerados. O termo computação quântica e um primeiro modelo formal de computação quântica foram definidos na década de 80. Com a descoberta no ano de 1997 de um algoritmo quântico para fatoração exponencialmente mais rápido do que qualquer algoritmo clássico conhecido a computação quântica passou a atrair investimentos de diversas empresas para a construção de um computador quântico e para o desenvolvimento de algoritmos quânticos. Por exemplo, o desenvolvimento de algoritmos de aprendizado para redes neurais. Alguns modelos de Redes Neurais Artificiais podem ser utilizados para simular uma máquina de Turing universal. Devido a sua capacidade de aprendizado, existem aplicações de redes neurais artificiais nas mais diversas áreas do conhecimento. Uma das limitações das redes neurais artificiais é a inexistência de um algoritmo com custo polinomial para determinar a melhor arquitetura de uma rede neural. Este trabalho tem como objetivo principal verificar se é possível obter alguma vantagem no uso da computação quântica no processo de seleção de arquiteturas de uma rede neural. Um modelo de rede neural quântica denominado perceptron quântico sobre um corpo foi proposto. O perceptron quântico sobre um corpo é uma generalização direta de um perceptron clássico que resolve algumas das limitações em modelos de redes neurais quânticas previamente propostos. Um algoritmo de aprendizado denominado algoritmo de aprendizado de arquitetura baseado no princípio da superposição que otimiza pesos e arquitetura de uma rede neural simultaneamente é apresentado. O algoritmo proposto possui custo linear e determina a melhor arquitetura em um conjunto finito de arquiteturas e os parâmetros da rede neural. O algoritmo de aprendizado proposto é o primeiro algoritmo quântico para determinar a arquitetura de uma rede neural com custo linear. O custo linear é obtido pelo uso do paralelismo quântico e de um operador quântico não linear.
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Feinstein, David Dov Yehuda. "Computer-aided-design methods for emerging quantum computing technologies". Ann Arbor, Mich. : ProQuest, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303775.
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Thesis (Ph.D. in Computer Engineering)--S.M.U.Title from PDF title page (viewed Mar. 16, 2009). Source: Dissertation Abstracts International, Volume: 69-03, Section: B, page: 1733. Adviser: Mitchell A. Thornton. Includes bibliographical references.
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Chung, Hyeyoun M. Eng Massachusetts Institute of Technology. "The study of entangled states in quantum computation and quantum information science". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45991.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 267-274).
This thesis explores the use of entangled states in quantum computation and quantum information science. Entanglement, a quantum phenomenon with no classical counterpart, has been identified as an important and quantifiable resource in many areas of theoretical quantum information science, including quantum error correction, quantum cryptography, and quantum algorithms. We first investigate the equivalence classes of a particular class of entangled states (known as graph states due to their association with mathematical graphs) under local operations. We prove that for graph states corresponding to graphs with neither cycles of length 3 nor 4, the equivalence classes can be characterized in a very simple way. We also present software for analyzing and manipulating graph states. We then study quantum error-correcting codes whose codewords are highly entangled states. An important area of investigation concerning QECCs is to determine which resources are necessary in order to carry out any computation on the code to an arbitrary degree of accuracy, while simultaneously maintaining a high degree of resistance to noise. We prove that transversal gates, which are designed to prevent the propagation of errors through a system, are insufficient to achieve universal computation on almost all QECCs. Finally, we study the problem of creating efficient quantum circuits for creating entangling measurements.
(cont.) Entangling measurements can be used to harness the apparent extra computing power of quantum systems by allowing us to extract information about the global, collective properties of a quantum state using local measurements. We construct explicit quantum circuits that create entangling measurements, and show that these circuits scale polynomially in the input parameters.
by Hyeyoun Chung.
M.Eng.
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Mayfield, James L. IV. "A Parameterized Framework for Quantum Computation". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342543546.
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Green, Alexander S. "Towards a formally verified functional quantum programming language". Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11457/.
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This thesis looks at the development of a framework for a functional quantum programming language. The framework is first developed in Haskell, looking at how a monadic structure can be used to explicitly deal with the side-effects inherent in the measurement of quantum systems, and goes on to look at how a dependently-typed reimplementation in Agda gives us the basis for a formally verified quantum programming language. The two implementations are not in themselves fully developed quantum programming languages, as they are embedded in their respective parent languages, but are a major step towards the development of a full formally verified, functional quantum programming language. Dubbed the “Quantum IO Monad”, this framework is designed following a structural approach as given by a categorical model of quantum computation.
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Williams, Benjamin S. (Benjamin Stanford) 1974. "Terahertz quantum cascade lasers". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17012.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (p. 297-310).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
The development of the terahertz frequency range has long been impeded by the relative dearth of compact, coherent radiation sources of reasonable power. This thesis details the development of quantum cascade lasers (QCLs) that operate in the terahertz with photon energies below the semiconductor Reststrahlen band. Photons are emitted via electronic intersubband transitions that take place entirely within the conduction band, where the wavelength is chosen by engineering the well and barrier widths in multiple-quantum-well heterostructures. Fabrication of such long wavelength lasers has traditionally been challenging, since it is difficult to obtain a population inversion between such closely spaced energy levels, and because traditional dielectric waveguides become extremely lossy due to free carrier absorption. This thesis reports the development of terahertz QCLs in which the lower radiative state is depopulated via resonant longitudinal-optical phonon scattering. This mechanism is efficient and temperature insensitive, and provides protection from thermal backfilling due to the large energy separation between the lower radiative state and the injector. Both properties are important in allowing higher temperature operation at longer wavelengths. Lasers using a surface plasmon based waveguide grown on a semi-insulating (SI) GaAs substrate were demonstrated at 3.4 THz in pulsed mode up to 87 K, with peak collected powers of 14 mW at 5 K, and 4 mW at 77 K.
Additionally, the first terahertz QCLs have been demonstrated that use metalmetal waveguides, where the mode is confined between metal layers placed immediately above and below the active region. These devices have confinement factors close to unity, and are expected to be advantageous over SI-surface-plasmon waveguides, especially at long wavelengths. Such a waveguide was used to obtain lasing at 3.8 THz in pulsed mode up to a record high temperature of 137 K, whereas similar devices fabricated in SI-surface-plasmon waveguides had lower maximum lasing temperatures due to the higher losses and lower confinement factors. This thesis describes the theory, design, fabrication, and testing of terahertz quantum cascade laser devices. A summary of theory relevant to design is presented, including intersubband radiative transitions and gain, intersubband scattering, and coherent resonant tunneling transport using a tight-binding density matrix model. Analysis of the effects of the complex heterostructure phonon spectra on terahertz QCL design are considered. Calculations of the properties of various terahertz waveguides are presented and compared with experimental results. Various fabrication methods have been developed, including a robust metallic wafer bonding technique used to fabricate metal-metal waveguides. A wide variety of quantum cascade structures, both lasing and non-lasing, have been experimentally characterized, which yield valuable information about the transport and optical properties of terahertz devices. Finally, prospects for higher temperature operation of terahertz QCLs are considered.
by Benjamin S. Williams.
Ph.D.
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Preda, Daniel C. (Daniel Ciprian) 1979. "Quantum query complexity revisited". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29689.
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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2003.Includes bibliographical references (leaves 30-31).
In this thesis, we look at the polynomial method for quantum query complexity and relate it to the BQPA = PA question for a random oracle A. We will also look at some open problems and improve some bounds relating classical and quantum complexity.
by Daniel C. Preda.
M.Eng.and S.B.
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Smith, Adam (Adam Davidson) 1977. "Multi-party quantum computation". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86782.
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Wilson, Frederick Wilson. "Simulating atomic-scale dopant placement for a solid-state quantum computer". Thesis, The University of Sydney, 2006. https://hdl.handle.net/2123/28160.
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A quantum computer is a device which exploits quantum mechanics to per—
form calculations which would be impractical using ordinary classical means.
Fabrication of a large—scale quantum computer would drastically expand the
scope of possible calculations, and is seen as one of the most important technological challenges of the near future. While a wide variety of different quan— tum computing architectures have been proposed, one particularly promising scheme due to Bruce Kane has attracted a great deal of experimental and theoretical attention, due to its scalability and use of conventional doped—
silicon technology. In this thesis, I present simulations aimed at determining how such a device can be fabricated.
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Malik, Zahid. "Computer simulation of fundamental quantum processes using the Bohm theory". Thesis, University of Portsmouth, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238808.
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Dixon, Alexander Robert. "High speed and actively stabilised quantum key distribution". Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609865.
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