Thèses : « Quantum science and technology »

1

Peruzzo, Alberto. « Quantum information science in integrated photonics technology ». Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573139.

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Quantum information science provides new paradigms of communication, computation and measurement; such as perfectly secure quantum key distribution, intrinsic parallel computation and increased precision measurement by beating the standard quantum limit. The first implementation of optical quantum circuits whose performance exceeds that required for fault tolerance quantum computation is presented. Near- unit fidelity non-classical interference and entangling operations are demonstrated in integrated photonic waveguides fabricated on silica on silicon chips. Improvement of about 5% in the measured performance is the result of perfectly indistinguishable photon pairs produced from an SPDC source. These integrated devices, combined with high efficiency single photon sources and detectors, will be the building block for future demonstrations of quantum information. Operation of quantum optics circuits with superconducting nanowire single photon detectors (SNSPD) is reported. The lower jitter of SNSPDs compared to silicon single photon avalanche photodiodes (SPADs) enables the measurement of higher visibility non-classical interference on directional couplers, CNOT gates and Mach-Zehnder interferometer. SSPDs are fast, low noise and can detect single photons in a broad range of wavelengths. Recent studies show very high detection efficiency making these devices promising for future photonic quantum information processing. Quantum interference in multi-mode interference (MMI) devices is reported for the first time. These devices allow the design of NxM splitters with superior performances, excellent tolerance to polarization and wavelength variations and relaxed fabrication requirements compared to the other main beam splitting technology, the directional couplers. However, to date, there have been no demonstrations of quantum interference in MMI devices (one may be concerned that multi-mode operation could prevent or perturb such interference). It is found that that the quantum interference visibility is significantly lower than that of a directional coupler with the same source. A major reason for the reduced visibility is the coherence length of the photons, which is set by the large-band interference filters. Since the different modes see different effective refractive indices within the interferometer, a jitter is 'introduced which allows distinguishability between the photons. To overcome this problem a narrower filter was introduced in one of the channels between the device and the detector, i.e. not affecting the source. This quantum erasure technique increases the detected indistinguishability of the photons, showing a high visibility and confirming that timing jitter limits quantum interference with large filters. The first observation of quantum walks of two indistinguishable particles is reported. Quantum walks offer new tools for simulating physical, chemical and biological systems, performing universal quantum computation and studying generalized quantum interference. Experimental demonstrations to date have shown single particle quantum walks; the observable dynamics of which can be fully explained with classical wave mechanics and experimentally mimicked using, for example, bright laser light. To observe uniquely quantum mechanical correlations in quantum walks, the propagation of two single, indistinguishable photons in an array of 21 waveguides in a silicon oxynitride chip is measured. The simultaneous walk of two photons on a graph simulate the walk of a single photon on a larger graph; the graph growing exponentially when linearly increasing the number of photons. These results violate classical bounds and cannot be efficiently simulated or described using classical mechanics. It is shown that the output strongly depends on the input state. Previous quantum optical work has highlighted the promise of monolithic integrated optics for quantum information science. This demonstration takes advantage of the intrinsic stability of photonic waveguide circuits to perform two-photon interference on a large scale. The results presented in this Thesis demonstrate the potential of integrated quantum photonic technology for quantum information applications, in particular quantum computation and quantum simulation.

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Wollmann, Sabine. « Resources for Optical Quantum Information Science and Technology ». Thesis, Griffith University, 2017. http://hdl.handle.net/10072/365844.

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Quantum information science explores the foundational aspects of quantum mechanics and its ombination with information science for new information technologies. The underlying key resource is non-classical correlations. These counter-intuitive correlations between quantum systems can be used for encoding, transmitting and measuring information in quantum information tasks. Although quantum properties can be used in a variety of systems, here we explore photons. These information carriers are fast, easy to generate and manipulate and only interact weakly with the environment. These properties make them to excellent candidates to be employed in experiments. Developing quantum technology, such as single photon sources and single photon detectors, allows us to investigate the foundational aspects of quantum mechanics in quantum information tasks. These tasks use non-classical correlations, which form a hierarchy, from Bell nonlocality to Einstein-Podolsky-Rosen (EPR) steering to quantum nonseparability. Two systems are nonlocally correlated, when measuring one system affects the measurement results on the other system, hence the name `steering. In test for non-classical correlations, we share a quantum state between two observers which are trusted or untrusted. While observers are both untrusted or trusted in entanglement witness tests and Bell inequality violations, respectively, EPR-steering is distinct from these two classes by its fundamental asymmetry: one party is trusted while the other is untrusted.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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Matthews, Jonathan C. F. « Multi-photon quantum information science and technology in integrated optics ». Thesis, University of Bristol, 2011. http://hdl.handle.net/1983/9199e590-ef8b-4a6f-b032-507b0960adc4.

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Fundamental quantum physics and quantum information science has found great experimental success with the implementation of single photons. To date, however, the majority of quantum optical experiments use large scale (bulk) optical elements bolted down to an optical bench; an approach that ultimately limits the complexity and stability of quantum circuits required for quantum science and technology (QST). Here, a series of experiments are reported in the emerging field of integrated quantum photonics that show monolithic waveguide chips to be a suitable platform for realising the next generation of quantum optical circuits. The thesis begins by reporting high quality Hong-Ou-Mandel interference-a phenomena that is central to nearly all photonic QST -in directly written waveguide structures. We then observe multi-photon quantum interference in lithographically fabricated waveguide circuits to implement the following demonstrations relevant to quantum computation, quantum metrology and analogue quantum simulation: (i) a compiled version of Shor's quantum algorithm is performed to factorize 15, using a number of integrated single- and two-qubit gates; (ii) a reconfigurable circuit is used to observe super-sensitive quantum interference fringes by manipulating two- and four-photon number-path entanglement; (iii) high quality quantum interference is observed in the reconfigurable device, indicating use as a building block for arbitrary reconfigurable circuits and (iv) a scheme for heralding two- and four-photon entanglement is implemented using projective measurement of auxiliary photons. The capabilities of integrated quantum photonics are extended beyond those of bulk quantum optics with two further demonstrations using arrays of evanescently coupled waveguide: (v) continuous quantum interference of two photons in a 21 mode quantum walk is realised, demonstrating generalisation of the Hong-OuMandel effect and (vi) the symmetry and quantum correlations of two polarisation entangled photons injected into a waveguide array are used to directly simulate quantum interference of fermions, bosons and a continuum of fractional behaviour exhibited by anyons. The latter demonstration is shown to generalise simulation of quantum interference in any mode transformation and to simulate quantum interference of any number of particles. For both demonstrations, implementing such unitary evolution with bulk optics would require hundreds of individual elements in a large interferometric structure which in practice is beyond the abilities of conventional quantum optics. The results presented in this thesis report elementary integrated circuits for future quantum devices and presents quantum experiments realised in integrated photonics, that cannot be realised with bulk optical components. These demonstrations are foundational in developing a new quantum photonic platform necessary for studying fundamental quantum physics and for advancing quantum information science and technology.

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Eltony, Amira M. (Amira Madeleine). « Scalable trap technology for quantum computing with ions ». Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99822.

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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 [187]-214).
Quantum computers employ quantum mechanical effects, such as superposition and entanglement, to process information in a distinctive way, with advantages for simulation and for new, and in some cases more-efficient algorithms. A quantum bit is a two-level quantum system, such as the electronic or spin state of a trapped atomic ion. Physics experiments with single atomic ions acting as "quantum bits" have demonstrated many of the ingredients for a quantum computer. But to perform useful computations these experimental systems will need to be vastly scaled-up. Our goal is to engineer systems for large-scale quantum computation with trapped ions. Building on established techniques of microfabrication, we create ion traps incorporating exotic materials and devices, and we investigate how quantum algorithms can be efficiently mapped onto physical trap hardware. An existing apparatus built around a bath cryostat is modified for characterization of novel ion traps and devices at cryogenic temperatures (4 K and 77 K). We demonstrate an ion trap on a transparent chip with an integrated photodetector, which allows for scalable, efficient state detection of a quantum bit. To understand and better control electric field noise (which limits gate fidelities), we experiment with coating trap electrodes in graphene. We develop traps compatible with standard CMOS manufacturing to leverage the precision and scale of this platform, and we design a Single Instruction Multiple Data (SIMD) algorithm for implementing the QFT using a distributed array of ion chains. Lastly, we explore how to bring it all together to create an integrated trap module from which a scalable architecture can be assembled.
by Amira M. Eltony.
Ph. D.

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Zhao, Xinyue M. Eng Massachusetts Institute of Technology. « Commercialization of Quantum Dot White Light Emitting Diode technology ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37678.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references.
It is well known that the use of high-brightness LEDs for illumination has the potential to substitute conventional lighting and revolutionize the lighting industry over the next 10 to 20 years. However, successful penetration of this extremely large lighting market would require vast improvements in power conversion efficiencies, color index, light output per device and drastic reduction in cost. Quantum Dot white LED (QD WLED) technology may be one of the best choices, due to its higher energy efficiency, larger color render in index, better versatility and more importantly lower cost, compared to conventional blue LED plus YAG: Ce yellow phosphor technology. Due to the fundamental difference of the material structure, QD LEDs will win a steady position among existing white LED patents and a hybrid fabless plus IP business model has the best position to promote this technology to maximize its benefits and potential for the entire LED industry.
by Xinyue Zhao.
M.Eng.

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Liu, Jingwei M. Eng Massachusetts Institute of Technology. « An evaluation of indium antimonide quantum well transistor technology ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37883.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2006.
Includes bibliographical references (leaves 98-102).
Motivated by the super high electron mobility of Indium Antimonide (InSb), researchers have seen great potential to use this new material in high switching speed and low power transistors. In Dec, 2005, Intel and its partner, QinetiQ, Ltd, announced 85nm gate length enhancement and depletion mode InSb quantum well transistors. Such transistors can operate as high as 305GHz and power consumption is reduced by a factor of 10. In this thesis, the emerging InSb transistor technology is discussed in details. Given its superior performance, it may complement silicon transistor to extend Moore's law in the next decade. The prospect of InSb transistor is also compared with other nanotechnology transistors, such as carbon nanotube and silicon nanowire. Several potential markets are figured out, namely, microprocessor, low noise amplifier and millimeter wave device. Related patents are evaluated. It is found that most of the patents are held by Intel's partner, QinetiQ Ltd. and thus patents issue would not block the launch of products. A joint venture or strategy alliance model is proposed to reduce the risk of investment. In addition, a cost model is presented at the end. It is concluded that cheap silicon substrate and large enough production scale are two crucial factors for the commercialization success of InSb transistor technology.
by Jingwei Liu.
M.Eng.

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Waters, Jayson Cydhaarth. « Estranged/Entangled : The History, Theory, and Technology of Quantum Mechanics in International Relations ». Thesis, The University of Sydney, 2022. https://hdl.handle.net/2123/29604.

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In recent years a growing number of scholars of international relations (IR) have looked hopefully towards quantum mechanics (QM) as a source of new analytical tools and critical approaches to address many of the intractable problems — and emergent challenges — faced by the discipline and the world. It now appears that what some call a new ‘wave’ — or ‘turn’ or ‘era’ — and others a paradigm shift may be coming to the discipline. Novel, and more accurate, methods for modelling behaviour are being introduced by Quantum Decision Theory and Quantum Game Theory, and old Newtonian analogies, metaphors, and cosmologies are being challenged and replaced by quantum equivalents. Alexander Wendt has even gone so far as to suggest that scholars need to rethink the social sciences from the (quantum) mind up. In place of traditional mind/body dualism, Wendt proposes a quantum monism based on a panpsychist quantum theory of mind. This is a radical proposal, the ramifications of which could drastically reframe understandings of both the social and physical aspects of the world. While there is no doubt that the present ‘quantum wave’ in IR is the most significant, it is not the first. In 1927, during his address to the American Political Science Association, William Bennett Munro called for political scientists to engage with QM and to borrow, by analogy, from the ‘new physics’ to “get rid of intellectual insincerities concerning the nature of sovereignty, the general will, natural rights, and the freedom of the individual” and discover “the true purposes and policies which should direct human action in matters of government.” Remarkably, Munro’s appeal came a mere two months after Max Born and Werner Heisenberg declared “quantum mechanics to be a closed theory” at the Fifth Solvay Conference. Some headway was made during the interwar period, but a complex combination of circumstances leading up to, and following, the Second World War estranged this line of scientific inquiry from IR theory. This pattern of estrangement and entanglement has recurred several times in the history of IR. This thesis employs an experimental methodology to interrogate three neglected aspects of the relationship between QM and IR. The critical approaches of genealogy, semiology, and dromology are applied, respectively, to the historical, theoretical, and technological entanglements of IR and QM. Reinterpreting nearly a century of estrangement and entanglement, the thesis makes the case for a quantum theory of IR that is process-relational and event-ontological. Ultimately, however, this thesis is a work of pre-theory. Rather than presenting a critique of quantum IR, or an attempt at a fully formed quantum theory of IR, this thesis lays the groundwork for future theory and future developments in quantum IR.

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Burkhardt, Martin. « Fabrication technology and measurement of coupled quantum dot devices ». Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11403.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1995.
Includes bibliographical references (p. 163-162).
by Martin Burkhardt.
Ph.D.

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Razzaghe, Ashrafi Babak 1964. « Making and remaking quantum field theory ». Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29762.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Program in Science, Technology and Society, 2003.
Includes bibliographical references (leaves 139-156).
In this thesis, I examine two episodes in the history of quantum field theory using different research techniques and historiographic approaches. The first episode occurred during the 1920's and 1930's when quantum mechanics and relativity were being reconciled. I present some of the central developments of that episode using an approach that relates questions asked by physicists to the structures of putative natural kinds upon which they predicated their research. The second episode occurred during the 1960's and 1970's when important features of quantum field theory were given new interpretations that arose from the exchange of methods and insights between particle physics, solid state physics, statistical mechanics and physical chemistry. Research for the second episode was conducted in collaboration with other historians and scientists using novel web-based and database-backed research tools.
by Babak Razzaghe Ashrafi.
Ph.D.

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Kim, LeeAnn. « Deposition of colloidal quantum dots by microcontact printing for LED display technology ». Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/37207.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.
Includes bibliographical references (p. 81-84).
This thesis demonstrates a new deposition method of colloidal quantum dots within a quantum dot organic light-emitting diode (QD-LED). A monolayer of quantum dots is microcontact printed as small as 20 ,Lm lines as well as millimeter scale planes, and the resulting devices show quantum efficiencies as high as 1.2% and color saturation superior to previous QD-LEDs'. Through a modification of the polydimethylsiloxane (PDMS) stamp with a parylene-C coating, quantum dots solvated in chloroform were successfully inked and stamped onto various substrates, including different molecular organic layers. The ability to control the placement and the pattern of the quantum dots independently from underlying organic layers provides a new level of performance in QD-LEDs, increasing the possibility of QD-LED displays.
by LeeAnn Kim.
M.Eng.

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Spada, Roberta. « The second quantum revolution : designing a teaching-learning activity on the quantum manifesto to futurize science education ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18360/.

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Questa tesi è la conclusione di un lavoro all’interno di I SEE (Inclusive STEM Education to Enhance the capacity to aspire and imagine future careers), un progetto europeo Erasmus+ coordinato dall’Università di Bologna e che coinvolge altri sei partner (http://iseeproject.eu). Il mio lavoro ha portato allo sviluppo di un’attività didattica intitolata “Applicazioni e implicazioni dei computer quantistici nella società” che è parte di un modulo I SEE sui computer quantistici. Progetto e attività mirano a contribuite a due dibattiti nella ricerca sull’educazione scientifica: quello sulla didattica STEM e sulla sua posizione in contesti di ricerca, istituzionali e didattici; quello sulla percezione del futuro da parte dei giovani in questo mondo in accelerazione. Il primo capitolo riguarda lo stato dell’arte del dibattito sulla didattica STEM, da un punto di vista sia di ricerca che istituzionale, come modo di affrontare temi chiave che riguardano il rapporto problematico tra scienza e società. Nel secondo capitolo, viene presentato il progetto I SEE e collocato all’interno della ricerca nella didattica STEM. È fornita una descrizione di come tale progetto contribuisce a promuovere lo sviluppo delle cosiddette future-scaffolding skills e a disegnare un approccio STEM integrato, con una descrizione dei moduli finlandese e italiano sulle tecnologie quantistiche. Il terzo capitolo include la descrizione dell’attività che ho contribuito a sviluppare. Essa è stata costruita per raggiungere diversi obiettivi tra cui guidare gli studenti di scuola secondaria a familiarizzare con la terminologia, le prospettive e i contenuti di documenti istituzionali come il Quantum Manifesto, e rendersi conto delle tante dimensioni coinvolte, riconoscendo dove e come le tecnologie quantistiche potranno essere d’impatto nella vita del singolo. Infine, si discutono i risultati dell’implementazione dell’attività avvenuta a Bologna nel febbraio 2019 con 25 studenti di scuola secondaria.

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Rafiei, Nima. « Quantum Communication Networks ». Thesis, Stockholms universitet, Fysikum, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-186606.

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Quantum communication protocols invoke one of the most fundamentallaws of quantum mechanics, namely the superposition principle whichleads to the no-cloning theorem. During the last three decades, quantumcryptography have gone from prospective theories to practical implementationsscalable for real communication. Scientist from all over the world havecontributed to this major progress, starting from Stephen Wiesner, CharlesH. Bennett and Gilles Brassard who all developed the theory of QuantumKey Distribution (QKD). QKD lets two users share a key through a quantumchannel (free space or fiber link) under unconditionally secure circumstances.They can use this key to encode a message which they thereaftershare through a public channel (internet, telephone,...). Research developmentshave gone from the ordinary 2-User Quantum Key Distribution oververy small free space distances to distances over 200 km in optical fiber andQuantum Key Distribution Networks.As great experimental achievements have been made regarding QKDprotocols, a new quantum communication protocol have been developed,namely Quantum Secret Sharing. Quantum Secret Sharing is an extensionof an old cryptography scheme called Secret Sharing. The aim of secretsharing is to split a secret amongst a set of users in such a way that thesecret is only revealed if every user of this set is ready to collaborate andshare their part of the secret with other users.We have developed a 5-User QKD Network through birefringent singlemode fiber in two configurations. One being a Tree configuration and theother being a Star configuration. In both cases, the number of users, thedistances between them and the stability of our setup are all well competitivewith the current worldwide research involving similar work.We have also developed a Single Qubit Quantum Secret Sharing schemewith phase encoding through single mode fiber with 3, 4 and 5 parties. Thelatter is, to the best of our knowledge, the first time a 5-Party Single QubitQuantum Secret Sharing experiment has been realized.

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Vestgöte, Karl. « Quantum Key Distribution - current state of the technology and prospects in the near future ». Thesis, Linköping University, Department of Electrical Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-17579.

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The thesis presents the basics of Quantum Key Distribution, a survey of the present techniques, a look at the possible future, and finally a comparison to the alternative technique of using public key or manual distribution of keys.

Techniques to integrate QKD with the existing telecom fiber infrastructure have been studied, and so has the EU-funded project SECOQC.

Last the security and efficiency of QKD have been examined, with focus on what level of security that is required, existing security solutions have been used as a comparison.

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Masini, Luca. « Terahertz technology : source design and applications ». Doctoral thesis, Scuola Normale Superiore, 2019. http://hdl.handle.net/11384/85920.

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Costa, De Almeida Ricardo. « Entanglement certification in quantum many-body systems ». Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/356801.

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Entanglement is a fundamental property of quantum systems and its characterization is a central problem for physics. Moreover, there is an increasing demand for scalable protocols that can certify the presence of entanglement. This is primarily due to the role of entanglement as a crucial resource for quantum technologies. However, systematic entanglement certification is highly challenging, and this is particularly the case for quantum many-body systems. In this dissertation, we tackle this challenge and introduce some techniques that allow the certification of multipartite entanglement in many-body systems. This is demonstrated with an application to a model of interacting fermions that shows the presence of resilient multipartite entanglement at finite temperatures. Moreover, we also discuss some subtleties concerning the definition entanglement in systems of indistinguishable particles and provide a formal characterization of multipartite mode entanglement. This requires us to work with an abstract formalism that can be used to define entanglement in quantum many-body systems without reference to a specific structure of the states. To further showcase this technique, and also motivated by current quantum simulation efforts, we use it to extend the framework of entanglement witnesses to lattice gauge theories.
L'entanglement è una proprietà fondamentale dei sistemi quantistici e la sua caratterizzazione è un problema centrale per la fisica. Inoltre, vi è una crescente richiesta di protocolli scalabili in grado di certificare la presenza di entanglement. Ciò è dovuto principalmente al ruolo dell'entanglement come risorsa cruciale per le tecnologie quantistiche. Tuttavia, la certificazione sistematica dell'entanglement è molto impegnativa, e questo è particolarmente vero per i sistemi quantistici a molti corpi. In questa dissertazione, affrontiamo questa sfida e introduciamo alcune tecniche che consentono la certificazione dell'entanglement multipartito in sistemi a molti corpi. Ciò è dimostrato con un'applicazione a un modello di fermioni interagenti che mostra la presenza di entanglement multipartito resiliente a temperature finite. Inoltre, discutiamo anche alcune sottigliezze riguardanti la definizione di entanglement in sistemi di particelle indistinguibili e forniamo una caratterizzazione formale dell'entanglement multipartito. Ciò ci richiede di lavorare con un formalismo astratto che può essere utilizzato per definire l'entanglement nei sistemi quantistici a molti corpi senza fare riferimento a una struttura specifica degli stati. Per mostrare ulteriormente questa tecnica, e anche motivata dagli attuali sforzi di simulazione quantistica, la usiamo per estendere la struttura dei testimoni di entanglement alle teorie di gauge del reticolo.

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Di, Stefano Pietro Giuseppe. « Quantum technologies with superconducting artificial atoms ». Doctoral thesis, Università di Catania, 2017. http://hdl.handle.net/10761/3849.

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In the present work, we explore possible routes to the future exploitation of quantum technologies in superconducting artificial atoms. The objectives of the thesis are twofold. On the one hand, we study advanced control of the quantum states of individual artificial atoms, tailored at robust and faithful quantum information processing in complex architectures and at the detection of the Ultra Strong Coupling regime. On the other hand, we study and propose a framework to experimentally establish quantum stochastic thermodynamics in circuit-QED. In chapter 3, the implementation of a Lambda system in superconducting artificial atoms is discussed. Strategies for optimal design are investigated by means of optimal symmetry breaking and dynamical decoupling. Stimulated Raman Adiabatic Passage (STIRAP), an adiabatic population transfer technique in three-level system, is introduced and its transfer efficiency is shown to be around 70% in the Cooper Pair Box. Optimization strategies are also discussed. In chapter 4, a novel technique for population transfer in a Lambda system is proposed, nicknamed chirped STIRAP (cSTIRAP), its key asset being the possibility of operating with an always on driving field. Robustness against parametric imperfections is assessed and specific regimes of failure due to energy level fluctuations are thoroughly examined. A novel way to control superconducting qutrits in the Lambda system is introduced in chapter 5. It is shown that, by employing a two-photon pump, the spectrum of the devices is changed in a non-trivial way by AC Stark shifts, that can be then compensated by suitable modulation of the driving phases. A 2+1 photons STIRAP technique is introduced, with transfer efficiency of 97% in last generation devices despite the presence of both low and high frequency noise. In chapter 6, dynamical detection of the Ultra Strong Coupling (USC) regime is studied. It is shown that, by implementing a three-level Vee scheme with a flux qutrit, non classical effects and exotic light-matter interaction phenomena can be amplified and detected unambiguously. A Circuit-QED implementation of a non-equilibrium thermodynamic experiment is finally proposed in chapter 7. A stochastic thermodynamics formalism is defined and work and heat are defined at the single quantum trajectory level. Numerical simulations are shown and the possibility to verify detailed fluctuation theorems is demonstrated. Moreover, the entropy production is defined as a witness of irreversibility and trajectory with a negative entropy production are shown, the mean entropy production being non-negative as required by the second law.

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Andersson, Andreas. « State and Process Tomography : In Spekkens' Toy Model ». Thesis, Linköpings universitet, Informationskodning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-163156.

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In 2004 Robert W. Spekkens introduced a toy theory designed to make a case for the epistemic view of quantum mechanics. But how does Spekkens’ toy model differ from quantum theory? While some differences are well-established, we attempt to approach this question from a tomographic point of view. More speciﬁcally, we provide experimentally viableprocedureswhichenablesustocompletelycharacterizethestatesandgatesthatare available in the toy model. We show that, in contrast to quantum theory, decompositions of transformations in the toy model must be done in a non-linear fashion.

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Wu, Juwell Wendy. « Near-infrared emitting quantum dots for cellular and vascular fluorescent labeling in in vivo multiplexed imaging studies ». Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68460.

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Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 199-217).
In vivo multimodal, multiplexed microscopy allows real-time observation of hematopoietic cells, their stem and progenitor cells and metastatic cancer cells in their native bone marrow (BM) environment. Multiplexing has made possible detailed studies of the BM's microarchitecture, which helps define the niche of these cells; it has nonetheless been limited by the paucity of suitable probes fluorescent in the near-infrared spectrum that is favored by tissue optics. This project attempts to address this problem by developing cellular and vascular fluorescent imaging probes comprised of semiconductor nanocrystals, or quantum dots (QDs), with tunable fluorescence between 65o-8oonm and exhibiting photostability, robust quantum yield and narrow fluorescence profiles that are critical for such applications. The synthesis of alloyed CdTexSe1 x QDs will be detailed in the thesis. Reproducibility and workability in subsequent steps are emphasized in the methods. Special attention is also paid to the difference between working with alloyed versus single semiconductor QDs, especially the need to achieve physical and spectral uniformity when composition and its gradient are also variable. The steps for creating biological probes from these QD fluorophores are also described. They include overcoating, water solubilization and functionalization for cellular uptake and vascular retention. Finally, the thesis returns to its motivation and reports novel methods, developed using NIR QD vascular imaging probes, for visualizing in vivo 3-D imaging data of the murine BM and characterizing the tissue's architecture. Measuring the Euclidean distance between BM osteoblasts and blood vessels is presented to exemplify a potential platform for describing the geographic relationships between cells, molecules and structural components in any tissue.
by Juwell Wendy Wu.
Ph.D.

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Geier, Kevin Thomas. « Probing Dynamics and Correlations in Cold-Atom Quantum Simulators ». Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/351120.

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Cold-atom quantum simulators offer unique possibilities to prepare, manipulate, and probe quantum many-body systems. However, despite the high level of control in modern experiments, not all observables of interest are easily accessible. This thesis aims at establishing protocols to measure currently elusive static and dynamic properties of quantum systems. The experimental feasibility of these schemes is illustrated by means of numerical simulations for relevant applications in many-body physics and quantum simulation. In particular, we introduce a general method for measuring dynamical correlations based on non-Hermitian linear response. This enables unbiased tests of the famous fluctuation-dissipation relation as a probe of thermalization in isolated quantum systems. Furthermore, we develop ancilla-based techniques for the measurement of currents and current correlations, permitting the characterization of strongly correlated quantum matter. Another application is geared towards revealing signatures of supersolidity in spin-orbit-coupled Bose gases by exciting the relevant Goldstone modes. Finally, we explore a scenario for quantum-simulating post-inflationary reheating dynamics by parametrically driving a Bose gas into the regime of universal far-from-equilibrium dynamics. The presented protocols also apply to other analog quantum simulation platforms and thus open up promising applications in the field of quantum science and technology.
I simulatori quantistici ad atomi freddi offrono possibilità uniche per preparare, manipolare e sondare sistemi quantistici a molti corpi. Tuttavia, nonostante l'alto livello di controllo raggiunto negli esperimenti moderni, non tutte le osservabili di interesse sono facilmente accessibili. Lo scopo di questa tesi è quello di stabilire protocolli per misurare delle proprietà statiche e dinamiche dei sistemi quantistici attualmente inaccessibili. La fattibilità sperimentale di questi schemi è illustrata mediante simulazioni numeriche per applicazioni rilevanti nella fisica a molti corpi e nella simulazione quantistica. In particolare, introduciamo un metodo generale per misurare le correlazioni dinamiche basato su una risposta lineare non hermitiana. Ciò consente test imparziali della famosa relazione fluttuazione-dissipazione come sonda di termalizzazione in sistemi quantistici isolati. Inoltre, sviluppiamo tecniche basate su ancilla per la misura di correnti e correlazioni di corrente, consentendo la caratterizzazione della materia quantistica fortemente correlata. Un'altra applicazione è orientata a rivelare l'impronta della supersolidità nei gas Bose con accoppiamento spin-orbita eccitando il corrispondente modo di Goldstone. Infine, esploriamo uno scenario per la simulazione quantistica della dinamica di riscaldamento post-inflazione modulando parametricamente un gas Bose e portandolo nel regime della dinamica universale lontana dall'equilibrio. I protocolli presentati si applicano anche ad altre piattaforme di simulazione quantistica analogica e aprono quindi applicazioni promettenti nel campo della scienza e della tecnologia quantistica.
Quantensimulatoren auf Basis ultrakalter Atome eröffnen einzigartige Möglichkeiten zur Präparation, Manipulation und Untersuchung von Quanten-Vielteilchen-Systemen. Trotz des hohen Maßes an Kontrolle in modernen Experimenten sind jedoch nicht alle interessanten Observablen auf einfache Weise zugänglich. Ziel dieser Arbeit ist es, Protokolle zur Messung aktuell nur schwer erfassbarer statischer und dynamischer Eigenschaften von Quantensystemen zu etablieren. Die experimentelle Realisierbarkeit dieser Verfahren wird durch numerische Simulationen anhand relevanter Anwendungen in der Vielteilchenphysik und Quantensimulation veranschaulicht. Insbesondere wird eine allgemeine Methode zur Messung dynamischer Korrelationen basierend auf der linearen Antwort auf nicht-hermitesche Störungen vorgestellt. Diese ermöglicht unabhängige Tests des berühmten Fluktuations-Dissipations-Theorems als Indikator der Thermalisierung isolierter Quantensysteme. Darüber hinaus werden Verfahren zur Messung von Strömen und Strom-Korrelationen mittels Kopplung an einen Hilfszustand entwickelt, welche die Charakterisierung stark korrelierter Quantenmaterie erlauben. Eine weitere Anwendung zielt auf die Enthüllung spezifischer Merkmale von Supersolidität in Spin-Bahn-gekoppelten Bose-Einstein-Kondensaten ab, indem die relevanten Goldstone-Moden angeregt werden. Schließlich wird ein Szenario zur Quantensimulation post-inflationärer Thermalisierungsdynamik durch die parametrische Anregung eines Bose-Gases in das Regime universeller Dynamik fern des Gleichgewichts erschlossen. Die dargestellten Protokolle lassen sich auch auf andere Plattformen für analoge Quantensimulation übertragen und eröffnen damit vielversprechende Anwendungen auf dem Gebiet der Quantentechnologie.

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Bandyopadhyay, Avra Sankar. « Light Matter Interactions in Two-Dimensional Semiconducting Tungsten Diselenide for Next Generation Quantum-Based Optoelectronic Devices ». Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1752376/.

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In this work, we explored one material from the broad family of 2D semiconductors, namely WSe2 to serve as an enabler for advanced, low-power, high-performance nanoelectronics and optoelectronic devices. A 2D WSe2 based field-effect-transistor (FET) was designed and fabricated using electron-beam lithography, that revealed an ultra-high mobility of ~ 625 cm2/V-s, with tunable charge transport behavior in the WSe2 channel, making it a promising candidate for high speed Si-based complimentary-metal-oxide-semiconductor (CMOS) technology. Furthermore, optoelectronic properties in 2D WSe2 based photodetectors and 2D WSe2/2D MoS2 based p-n junction diodes were also analyzed, where the photoresponsivity R and external quantum efficiency were exceptional. The monolayer WSe2 based photodetector, fabricated with Al metal contacts, showed a high R ~502 AW-1 under white light illumination. The EQE was also found to vary from 2.74×101 % - 4.02×103 % within the 400 nm -1100 nm spectral range of the tunable laser source. The interfacial metal-2D WSe2 junction characteristics, which promotes the use of such devices for end-use optoelectronics and quantum scale systems, were also studied and the interfacial stated density Dit in Al/2D WSe2 junction was computed to be the lowest reported to date ~ 3.45×1012 cm-2 eV-1. We also examined the large exciton binding energy present in WSe2 through temperature-dependent Raman and photoluminescence spectroscopy, where localized exciton states perpetuated at 78 K that are gaining increasing attention for single photon emitters for quantum information processing. The exciton and phonon dynamics in 2D WSe2 were further analyzed to unveil other multi-body states besides localized excitons, such as trions whose population densities also evolved with temperature. The phonon lifetime, which is another interesting aspect of phonon dynamics, is calculated in 2D layered WSe2 using Raman spectroscopy for the first time and the influence of external stimuli such as temperature and laser power on the phonon behavior was also studied. Furthermore, we investigated the thermal properties in 2D WSe2 in a suspended architecture platform, and the thermal conductivity in suspended WSe2 was found to be ~ 1940 W/mK which was enhanced by ~ 4X when compared with substrate supported regions. We also studied the use of halide-assisted low-pressure chemical vapor deposition (CVD) with NaCl to help to reduce the growth temperature to ∼750 °C, which is lower than the typical temperatures needed with conventional CVD for realizing 1L WSe2. The synthesis of monolayer WSe2 with high crystalline and optical quality using a halide assisted CVD method was successfully demonstrated where the role of substrate was deemed to play an important role to control the optical quality of the as-grown 2D WSe2. For example, the crystalline, optical and optoelectronics quality in CVD-grown monolayer WSe2 found to improve when sapphire was used as the substrate. Our work provides fundamental insights into the electronic, optoelectronic and quantum properties of WSe2 to pave the way for high-performance electronic, optoelectronic, and quantum-optoelectronic devices using scalable synthesis routes.

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Otto, Ernst. « Development of superconducting bolometer device technology for millimeter-wave cosmology instruments ». Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:30a1103a-ea7a-4b08-ba92-665cbd9740e0.

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The Cold-Electron Bolometer (CEB) is a sensitive detector of millimeter-wave radiation, in which tunnel junctions are used as temperature sensors of a nanoscale normal metal strip absorber. The absorber is fed by an antenna via two Superconductor-Insulator-Normal metal (SIN) tunnel junctions, fabricated at both ends of the absorber. Incoming photons excite electrons, heating the whole electron system. The incoming RF power is determined by measuring the tunneling current through the SIN junctions. Since electrons at highest energy levels escape the absorber through the tunnel junctions, it causes cooling of the absorber. This electron cooling provides electro-thermal feedback that makes the saturation power of a CEB well above that of other types of millimeter-wave receivers. The key features of CEB detectors are high sensitivity, large dynamic range, fast response, easy integration in arrays on planar substrates, and simple readout. The high dynamic range allows the detector to operate under relatively high background levels. In this thesis, we present the development and successful operation of CEB, focusing on the fabrication technology and different implementations of the CEB for efficient detection of electromagnetic signals. We present the CEB detector integrated across a unilateral finline deposited on a planar substrate. We have measured the finline-integrated CEB performance at 280-315 mK using a calibrated black-body source mounted inside the cryostat. The results have demonstrated strong response to the incoming RF power and reasonable sensitivity. We also present CEB devices fabricated with advanced technologies and integrated in log-periodic, double-dipole and cross-slot antennas. The measured CEB performance satisfied the requirements of the balloon-borne experiment BOOMERANG and could be considered for future balloon-borne and ground-based instruments. In this thesis we also investigated a planar phase switch integrated in a back-to-back finline for modulating the polarization of weak electromagnetic signals. We examine the switching characteristics and demonstrate that the switching speed of the device is well above the speed required for phase modulation in astronomical instruments. We also investigated the combination of a detector and a superconducting phase switch for modulating the polarization of electromagnetic radiation.

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Clark, Lewis Alexander. « Quantum feedback for quantum technology ». Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18485/.

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It is widely believed that quantum physics is a fundamental theory describing the Universe. As such, one would expect to be able to see how classical physics that is observed in the macroscopic world emerges from quantum theory. This has so far largely eluded physicists, due to the inherent linear nature of quantum physics and the non-linear behaviour of classical physics. One of the principle differences between classical and quantum physics is the statistical, probabilistic nature of quantum theory. It is from this property that non-classical states can arise, such as entangled states. These states possess maximal correlations. However, they are not the only way in which correlations are created in quantum systems. This thesis aims to show how open quantum systems naturally contain correlations from their quantum nature. Moreover, even seemingly simple open quantum systems can behave far more complexly than expected upon the introduction of quantum feedback. Using this effect, the dynamics may become non-linear and as such behave non-trivially. Furthermore, it is shown how these effects may be exploited for a variety of tasks, including a computational application in hidden quantum Markov models and a quantum metrology scheme that does not require the use of exotic quantum states. This results in the design of systems that benefit from the use of quantum mechanics, but are not constrained by the use of experimentally difficulties such as entanglement.

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Sanders, Barry Cyril. « Quantum information science ». Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/55186.

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Weston, Margan Marianna Mackenzie. « Experimental Optical Quantum Science : Efficient Multi-Photon Sources for Quantum Information Science ». Thesis, Griffith University, 2017. http://hdl.handle.net/10072/367516.

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Quantum optics promises excellent capabilities for experimental demonstrations of quantum information processing. So far, the practical implementation of protocols displaying a clear quantum advantage has been limited, as they rely on perfect quantum states and high delity measurements. Additionally, the fragile nature of the quantum states makes them susceptible to imperfections in measurement devices, and environmental loss. Two of the key challenges for quantum technologies are that of producing single photons, and pairs of entangled photons, more eciently, and overcoming the detrimental effects of photon loss. The research presented in this thesis tackles the practical realisation of quantum-enhanced protocols by improving spontaneous parametric down conversion for producing photon pairs. I present a spontaneous parametric down-conversion source of frequency-uncorrelated polarisation-entangled photon pairs at telecom wavelengths. The source provides photon pairs that display-simultaneously-the key properties for high-performance quantum information tasks and the investigation of fundamental quantum physics. Specifically, the source provides high heralding efficiency, high quantum state purity and high entangled-state fidelity at the same time. Among the different tests applied, perfect non-classical interference between photons from independent sources with a visibility of (1005)% was observed. Additionally, the polarisation-unentangled version of the source achieved symmetric heralding efficiencies of up to (82 2)%. The following two experiments presented in this thesis make use of these high-performance sources to implement an entanglement verication protocol over a high-loss quantum channel, and to perform a quantum metrology experiment, both of which were not previously achievable with existing sources or designs.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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Matsuzaki, Yuichiro. « Robust measurement based quantum technology ». Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540143.

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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 qu
Nous 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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Higgins, Brendon Lloyd. « Quantum Measurement : Concepts, Algorithms, and Experiments in Photonic Quantum Information Science ». Thesis, Griffith University, 2010. http://hdl.handle.net/10072/366295.

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The application of concepts from quantum information science to the task of measuring properties of physical systems allows precision and perspectives going beyond that available through classical approaches. This thesis presents experimental and theoretical work that demonstrates this in the context of optical quantum systems, with particular emphasis on photonics.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Biomolecular and Physical Sciences
Science, Environment, Engineering and Technology
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Aungskunsiri, Kanin. « Reconfigurable photonic circuits for quantum technology ». Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.686825.

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In this thesis, we address critical problems on implementation of quantum key distribution (QKD), and two-qubit unitary estimation using linear optics. One of the most serious issues for practical implementation of the traditional QKD protocol is loss of alignment of shared reference-frame axes between communication parties. Reference-frame-independent quantum key distribution (rfi-QKD) is a protocol that circumvents this issue. Chapter 3 presents an experimental realisation of the rfi-QKD protocol that harnesses polarisations of photonic qubits for key exchange over a telecom polarisation-maintaining fibre (PMF). We have tested the rfi-QKD protocol and demonstrated its robustness for the typical environment in which the PMF would be deployed, including a unique feature of the system that allows the key exchange to recover itself after a period of disturbance. Following on from this work, we propose an ideal implementation of the rfi-QKD protocol configured as a communication between a client and a server, which provides a real prospect for putting this quantum technology into practical use. Next we present work on developing a two-qubit quantum processor, a resource for simulating two-qubit unitary transformation. This work includes theoretical and experimental parts, as well as a complete scheme for bulk-optical implementation. In chapter 4, theoretical work provides both an abstract technique and a linear-optical model for constructing an arbitrary two-qubit gate by implementing a linear combination of quantum operations. This work builds upon a method for adding control to an arbitrary unknown quantum operations in X.-Q. Zhou et al, Nature Communications 2, 413 {2011}. Then, we propose a reconfigurable circuit that harnesses two photons and simple linear-optical elements for implementing a system that can be used as a tool kit for simulating a two-qubit unitary evolution when the inputs are known and in the form of product states. A subset of the complete bulk optical scheme has been experimentally demonstrated and reported in chapter 5.

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Compagno, Enrico. « Lattice based low control quantum technology ». Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10045115/.

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The possibility to designing schemes useful for developing quantum technology devices of practical value necessitates exploiting quantum coherence effects in a scalable physical system in a feasible way. The broad aim of this thesis is to investigate the use of quantum non-equilibrium dynamics for the above, exploiting minimal control to accomplish highly coherent dynamics in a many-body system. How to harness the natural hopping dynamics of particles in a many-site lattice for controlled applications, is still an open question. Through the introduction of few impurities in the lattice potential, we devise a scheme to trigger effective tunable linear optics-like operations between arbitrary sites, that overcomes the limitations of setups based on coherent hopping dynamics, when particles are initially separated by many sites. Our scheme enables the generation of peculiar quantum interference effects as well as quantum metrology applications in a many-site lattice. We design a lattice coupling profile that enables perfect wave-packet splitting between mirror symmetric sites and leads to perfect wave-packet reconstruction, fractional revivals and perfect entanglement distribution, for arbitrary long chains. We prove that composite objects in a lattice, made of more particles initially in a lattice site, are a valuable resource for dynamically generating non-classical states between remote sites, tackling edge-localisation effects via local fields. Finally, we show how the spin independent scattering of two initially distant qubits, can be used to implement an entangling quantum gate between remote sites of a lattice. Our findings have potentially an impact on quantum information, as well as on atomic interferometry in a lattice.

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Ferguson, Elizabeth, et University of Lethbridge Faculty of Arts and Science. « Einstein, sacred science, and quantum leaps a comparative analysis of western science, Native science and quantum physics paradigm ». Thesis, Lethbridge, Alta. : University of Lethbridge, Faculty of Arts and Science, c2005, 2005. http://hdl.handle.net/10133/253.

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Science is curiosity about the natural world translated into knowledge; it serves to identify laws and validate hypotheses. The quest for knowledge is influenced by the paradigm of the scientist. The primary object of this study is to examine Quantum Mechanics and Sacred/Native science for similarities and differences. This will be accomplished through an extensive use of authorities from both Western and Native sciences in an in depth examination of the paradigms upon which their foundations are based. This study will explore language and how language used leads the scientist down a particular pathway. This study will conclude in a summary fashion, an exploration of a few select key concepts from both Native and Western sciences from a comparative perspective.
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Kómár, Péter. « Quantum Information Science and Quantum Metrology : Novel Systems and Applications ». Thesis, Harvard University, 2015. http://nrs.harvard.edu/urn-3:HUL.InstRepos:26718726.

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The current frontier of our understanding of the physical universe is dominated by quantum phenomena. Uncovering the prospects and limitations of acquiring and processing information using quantum effects is an outstanding challenge in physical science. This thesis presents an analysis of several new model systems and applications for quantum information processing and metrology. First, we analyze quantum optomechanical systems exhibiting quantum phenomena in both optical and mechanical degrees of freedom. We investigate the strength of non-classical correlations in a model system of two optical and one mechanical mode. We propose and analyze experimental protocols that exploit these correlations for quantum computation. We then turn our attention to atom-cavity systems involving strong coupling of atoms with optical photons, and investigate the possibility of using them to store information robustly and as relay nodes. We present a scheme for a robust two-qubit quantum gate with inherent error-detection capabilities. We consider several remote entanglement protocols employing this robust gate, and we use these systems to study the performance of the gate in practical applications. Finally, we present a new protocol for running multiple, remote atomic clocks in quantum unison. We show that by creating a cascade of independent Greenberger-Horne-Zeilinger states distributed across the network, the scheme asymptotically reaches the Heisenberg limit, the fundamental limit of measurement accuracy. We propose an experimental realization of such a network consisting of neutral atom clocks, and analyze the practical performance of such a system.
Physics

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Ho, Joseph. « Experimental Optical Quantum Science : Transforming and Measuring Photonic Quantum Systems ». Thesis, Griffith University, 2017. http://hdl.handle.net/10072/366445.

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Photons provide low-noise quantum systems which are ideal for the fundamental studies of the quantum world and for developing new quantum technologies which promise to transform the way we process, transmit and acquire information. The development of the eld of quantum information processing, broadly dened, represents one of the most important scientic and technical challenges of the 21st Century. Photons have been used in demonstrations of basic quantum logic, secure communication tasks, precision measurements and the fundamental studies of quantum mechanics. In order to apply these systems and technologies in an ever increasing scale, it is necessary to develop new methods for eciently manipulating the quantum state of light. This is one of the main goals of this study which experimentally demonstrates new techniques for realising multi-qubit logic gates as well as a new method for amplifying quantum states of light noiselessly.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
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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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Weidt, Sebastian. « Towards microwave based ion trap quantum technology ». Thesis, University of Sussex, 2014. http://sro.sussex.ac.uk/id/eprint/48893/.

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Scalability is a challenging yet key aspect required for large scale quantum computing and simulation using ions trapped in radio-frequency (rf) Paul traps. In this thesis 171Yb+ ions are used to demonstrate a magnetic field insensitive qubit which has a measured coherence time of 1.5 s, making it an ideal candidate to use for storing quantum information. A magnetic field sensitive qubit is also characterised which can be used for the implementation of multi-qubit gates using a potentially very scalable scheme based on microwaves in conjunction with a static magnetic field gradient instead of using lasers. However, the measured coherence time is limited by magnetic field fluctuations and will prohibit high fidelity gate operations from being performed. To address this issue, the preparation of a dressed-state qubit using a microwave based stimulated rapid adiabatic passage (STIRAP) pulse sequence will be presented. This qubit is protected against the noisy environment making it less sensitive to magnetic field fluctuations. The lifetime of this qubit is measured to demonstrate its suitability for storing quantum information. A powerful method for manipulating the dressed-state qubit will be presented and is used to measure a coherence time of the qubit of 500 ms which is two orders of magnitude longer compared to the magnetic field sensitive qubit. It will also be shown that our method allows for the implementation of arbitrary rotations of the dressed-state qubit on the Bloch sphere using only a single rf field. This substantially simplifies the experimental setup for single and multi-qubit gates. Furthermore, this thesis will present a experimental setup capable of successfully operating microfabricated surface ion traps. This setup is then used to operate and characterise the first two-dimensional (2D) lattice of ion traps on a microchip. A unique feature of the microfabrication technique used for this device is the extremely large voltage that can be applied which allows long ion lifetimes along with large secular frequencies to be measured, demonstrating the robustness of this device. Rudimentary shuttling between neighbouring lattice sites will be shown which could be used as part of a efficient scheme to load a large lattice of ions. One of the many applications of a 2D lattice of ions lies in the field of quantum simulations where many-body systems such as quantum magnetism, high temperature superconductivity, the fractional quantum hall effect and synthetic gauge fields can be simulated. It will be shown how making only minor modifications to the microchip the ion-ion separation can be reduced sufficiently to offer an exciting platform for the successful implementation of 2D quantum simulations. A theoretical investigation on the optimal 2D ion trap lattice geometry will also be presented with the aim to maximise the ratio of ion-ion coupling strength to decoherence from motional heating of the ions and to laser induced off-resonant coupling.

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Pope, Damian. « Contrasting quantum mechanics to local hidden variables theories in quantum optics and quantum information science / ». [St. Luica, Qld.], 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16765.pdf.

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Dihal, Kanta. « The stories of quantum physics : quantum physics in literature and popular science, 1900-present ». Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:ebe4c5eb-ce48-495f-b015-024f8ac4f4ac.

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This thesis investigates quantum physics narratives for non-physicists, covering four interlocking modes of writing for adults and children, fictional and nonfictional, from 1900 to the present. It brings together three separate scholarly fields: literature and science, science fiction, and science communication. The thesis has revealed parallels between the approaches to quantum physics in these disparate narratives that have not been addressed before, shedding new light on the mutual influences between science and narrative form. The thesis argues that similar narrative tropes have been employed in popular science writing and in fiction across all age groups, changing non-physicists' ideas of quantum physics. This understanding differs significantly from the professional understanding of quantum physics, as I establish by means of a series of case studies, including popular science books for adults by Alastair I.M. Rae, George Gamow and Robert Gilmore; popularizations for children by Lucy and Stephen Hawking, Russell Stannard, and Otto Fong; children's fiction by Philip Pullman and Madeleine L'Engle; and fiction for adults by Greg Egan, David Walton, Blake Crouch, and Iain Pears. An analysis of authors who wrote for various audiences or in multiple genres, such as Fred Hoyle, Stephen Hawking, and Ian Stewart, shows how the same concerns and conflicts surface in a wide range of stories. Quantum physics is not yet fully understood; the Copenhagen, conscious collapse, many-worlds and other interpretations compete for both scientific and public acceptance. Influential physics communicators such as John Gribbin and Brian Cox have written popularizations in which they express a personal preference for one interpretation, arguing against others. Scientific conflict, which tends to be omitted from university teaching, is thus explicitly present in popularizations, making it clear to the reader that quantum physics is in a constant state of flux. I investigate the conflicts between Fred Hoyle and George Gamow, and Stephen Hawking and Leonard Susskind, to see how they undermine the alleged objectivity of science. The interplay between the different stories of quantum physics shows how the science not only shapes the stories: the stories shape the science, too.

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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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Rakreungdet, Worawarong. « Quantum Information Science with Neutral Atoms ». Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194406.

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We study a system of neutral atoms trapped in a three-dimensional optical lattice suitable for the encoding, initialization and manipulation of atomic qubits. The qubits are manipulated by applied electromagnetic fields interacting with dipole moments of the atoms via light shifts, Raman transitions, Zeeman shifts, and microwave transitions. Our lattice is formed by three orthogonal one-dimensional lattices, which have different frequencies so that interference terms average to zero. This geometry allows considerable freedom in designing the component one-dimensional lattices, so that they provide not only confinement but also independent control in each dimension. Our atomic qubits are initialized from a laser-cooled atomic sample by Raman sideband cooling in individual lattice potential wells. We have demonstrated accurate and robust one-qubit manipulation using resonant microwave fields. In practice such control operations are always subject to errors, in our case spatial inhomogeneities in the microwave Rabi frequency and the light shifted qubit transition frequency. Observation of qubit dynamics in near real time allows us to minimize these inhomogeneities, and therefore optimize qubit logic gates. For qubits in the lattice, we infer a fidelity of 0.990(3) for a single pi-pulse. We have also explored the use of NMR-type pulse techniques in order to further reduce the effect of errors and thus improve gate robustness in the atom/lattice system. Our schemes for two-qubit quantum logic operations are based on controlled collisional interactions. We have experimented with two schemes in order to probe these collisions. The first involves manipulation of the center-of-mass wavepackets of two qubits in a geometry corresponding to two partially overlapping Mach-Zender interferometers. Unfortunately, this scheme has proven extremely sensitive to phase errors, as the wavepackets are moved by the optical lattice. The other scheme starts with two qubits in spatially separated traps, and utilizes microwaves to drive one or both qubits into a third trap in-between the two qubits. Once the wavepackets overlap, the collisions create a large energy shift which can be probed spectroscopically.

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Maurer, Peter. « Coherent control of diamond defects for quantum information science and quantum sensing ». Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11431.

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Quantum mechanics, arguably one of the greatest achievements of modern physics, has not only fundamentally changed our understanding of nature but is also taking an ever increasing role in engineering. Today, the control of quantum systems has already had a far-reaching impact on time and frequency metrology. By gaining further control over a large variety of different quantum systems, many potential applications are emerging. Those applications range from the development of quantum sensors and new quantum metrological approaches to the realization of quantum information processors and quantum networks. Unfortunately most quantum systems are very fragile objects that require tremendous experimental effort to avoid dephasing. Being able to control the interaction between a quantum system with its local environment embodies therefore an important aspect for application and hence is at the focus of this thesis.
Physics

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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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Wanzambi, Ellinor, et Stina Andersson. « Quantum Computing : Implementing Hitting Time for Coined Quantum Walks on Regular Graphs ». Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444818.

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In recent years, quantum walks have been widely researched and haveshown exciting properties. One such is a quadratic speed-up in hittingtime compared to its classical counterpart. In this paper, we design aquantum circuit for the MNRS algorithm, which finds a marked node in agraph with a quantum walk, and use it to find a hitting time for themarked nodes in the walk. We do this by implementing the circuit on IBMquantum simulators and show that the execution on a noise-free simulatorresults in hitting times that agree with the theoretical expectations.We also run the algorithm on a mock backend that simulates the noise ofthe IBM Melbourne computer. As expected, the noise has an extensiveimpact on the output, resulting in outcomes far from the noise-freesimulation.IT 21

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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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Ullah, Khan Sumsam. « Quantum K means Algorithm ». Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-266107.

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Quantum algorithms are being extensively researched nowadays seeing thepotential of providing exponential speed up when compared to classical algorithmexecution. This speed-up can play a big role in machine learning wheretraining a model is usually very slow. Training a machine learning model requiresmanipulating large vectors and quantum computers inherently are reallyfast at manipulating and computing large vectors and tensor products.However, current quantum computers have certain limitations with respect toqubit’s coherence times and noise. These barriers reduce their effectiveness insolving problems with high accuracy. In pursuit of having better results on currentterm noisy quantum computers, implementations of quantum algorithmswith simpler circuits are desired. To address this problem, three different novelmethods of the quantum version of the K-means clustering algorithm are presentedwith optimized shallow depth quantum circuit design. Experimentalresults on the quantum computer IBMQX2 are demonstrated which show asignificant improvement in the accuracy of the quantum K-means algorithm.
Forskning inom kvantalgoritmer har ökat kraftig under de senaste åren p.g.a. en lovande exponentiell speed up för visa beräkningar som kräver en mängd stor data och tar en lång tida i en klassikt dator. Den här speed up:en kan spela en stor roll i maskininlärning där träningen av en modell är vanligtvis mycket långsam. Träning av en maskininlärningsmodell kräver att man manipulerar stora vektorer och kvantdatorer är i själva verket snabba att manipulera och beräkna stora vektorer och tensorprodukter. Nuvarande kvantdatorer har emellertid vissa begränsningar med avseende på qubit-koherens och brus. Dessa hindrar deras effektivitet vid att lösa problem med hög noggrannhet. I strävan efter att ha bättre resultat på de befintliga brus-påverkade kvantdatorer, är det önskvärt att implementera kvantalgoritmer med enklare kvantkretsar. Vi adresserar problematiken med tre olika nya metoder för kvant K-means algorithm som har en optimerad grunddjupkvantkretsdesign. Experimentella resultat på kvantmaskinen IBMQX2 visas och e visar en betydande förbättringav precision hos kvant K-means algoritmen.

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Garrido, Mauricio. « Quantum Optics in Coupled Quantum Dots ». Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1273589966.

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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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Warner, Jamie. « Colloidal lead sulphide nanocrystals for quantum technology applications / ». [St. Lucia, Qld.], 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18436.pdf.

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Collins, Matthew John. « Nonlinear Single-photon Generation for Photonic Quantum Technology ». Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13631.

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Single photons are the smallest indivisible quanta of light, canonically described by quantum mechanics. By carefully controlling the interaction of single photons, exquisite non-classical phenomena can be observed. Mature photonic chip technology has recently emerged as an ideal platform for quantum information processing using single photons. However, generating single photons efficiently on-chip remains a fundamental challenge. One solution is to harness the intrinsic nonlinearity available in certain photonic materials for nonlinear photon generation directly in on-chip waveguides themselves. This work examines nonlinear photon generation in two key material platforms. The first is chalcogenide glass. Chalcogenide, while highly nonlinear, is amorphous and thus has broadband Raman noise. In this study the Raman noise is characterised at the single-photon level to find an intrinsic minima, which is then targeted for low-noise photon generation using an engineered waveguide. The second platform is silicon. As silicon is complementary metal-oxide-semiconductor (CMOS) fabrication compatible, it is congruent with mass production. Thus, in this study, photon-pair generation is first shown in a compact photonic crystal, before combining two monolithic sources using active multiplexing. This thesis presents significant progress towards a key goal of the field – on- demand photon generation in a fully integrated photonic quantum processor.

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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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Gedeborg, Erik, et Mikael Li. « Blinking quantum dots : Statistics through image analysis ». Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-53599.

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In this project we have developed an image processing program called Quantum Dot Analyzer that is able to detect and record quantum dot blinking sequences. Our purpose with the program was to analyze blinking quantum dots and to generate statistics for further research. With the program we can record the size, blinking intensity over time for quantum dots and do statistics of on- and off-times. We have used Java, ImageJ1 and Matlab in the development process. Java is a widely used object-oriented programming language notable for its portability. ImageJ is a public domain image processing program based on Java. For generating statistics we used Matlab, which is a mathematical computing program. The Quantum Dot Analyzer was made to be used as a plugin for ImageJ. The quantum dots show dfferent characteristics - some blinks, some are constantly on, some are off for a long time and then suddenly flash a quick light. By plotting the on- and off-time (logarithmically) for the quantum dots, we could conclude that the quantum dots show very different behaviour.

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