Dissertationen: „Photonic computing“

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Cao, Yameng. „Semiconductor light sources for photonic quantum computing“. Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/56619.

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The isolation of qubits from decoherence is crucial to the prospect of building revolutionary quantum devices. This work is devoted to an optical study of the decoherence on spin qubits in self-assembled quantum dots. This thesis contributes towards a complete understanding of quantum decoherence, of which highlighted discoveries include bypassing the spectral diffusion in neutral quantum dot emission lines; observing for the first time the self-polarization phenomenon of nuclear spins, via the resonance-locking effect on a negatively charged quantum dot; and revealing the limiting factors on hole spin dephasing, by measuring polarization correlations on a positively charged quantum dot. Three studies were conducted using two different spectroscopy techniques. For the first study, the spectral diffusion of emission line due to random electrostatic fluctuations was revealed, by scanning a neutral quantum dot transition across the laser resonance. Exciting the quantum dot resonantly bypassed this problem, paving the way for an on-demand antibunched source that generates narrow-band photons. For the second study, evidences supporting the spontaneous self-polarization of nuclear spins were observed for the first time, since it was predicted nearly four decades ago by M. Dyankonov and V.I. Perel. The self-polarization phenomenon is a remarkable demonstration of dynamic nuclear spin polarization since it manifests without the ground state electron being spin-polarized. In the last study, factors limiting the hole spin lifetime was inferred from measuring polarization correlation of successively emitted photons from a positively charged quantum dot. Evidences support a strong dependence on the carrier repopulation rate and the single electron spin dephasing in the upper state, due to the Overhauser field. In combination with the observation of spontaneous nuclear polarization, this opens the possibility of an electron spin sensor, which can indirectly probe the nuclear field.

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Birchall, Patrick Matthew. „Fundamental advantages and practicalities of quantum-photonic metrology and computing“. Thesis, University of Bristol, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.752791.

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Vinckier, Quentin. „Analog bio-inspired photonic processors based on the reservoir computing paradigm“. Doctoral thesis, Universite Libre de Bruxelles, 2016. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/237069.

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For many challenging problems where the mathematical description is not explicitly defined, artificial intelligence methods appear to be much more robust compared to traditional algorithms. Such methods share the common property of learning from examples in order to “explore” the problem to solve. Then, they generalize these examples to new and unseen input signals. The reservoir computing paradigm is a bio-inspired approach drawn from the theory of artificial Recurrent Neural Networks (RNNs) to process time-dependent data. This machine learning method was proposed independently by several research groups in the early 2000s. It has enabled a breakthrough in analog information processing, with several experiments demonstrating state-of-the-art performance for a wide range of hard nonlinear tasks. These tasks include for instance dynamic pattern classification, grammar modeling, speechrecognition, nonlinear channel equalization, detection of epileptic seizures, robot control, timeseries prediction, brain-machine interfacing, power system monitoring, financial forecasting, or handwriting recognition. A Reservoir Computer (RC) is composed of three different layers. There is first the neural network itself, called “reservoir”, which consists of a large number of internal variables (i.e. reservoir states) all interconnected together to exchange information. The internal dynamics of such a system, driven by a function of the inputs and the former reservoir states, is thus extremely rich. Through an input layer, a time-dependent input signal is applied to all the internal variables to disturb the neural network dynamics. Then, in the output layer, all these reservoir states are processed, often by taking a linear combination thereof at each time-step, to compute the output signal. Let us note that the presence of a non-linearity somewhere in the system is essential to reach high performance computing on nonlinear tasks. The principal novelty of the reservoir computing paradigm was to propose an RNN where most of the connection weights are generated randomly, except for the weights adjusted to compute the output signal from a linear combination of the reservoir states. In addition, some global parameters can be tuned to get the best performance, depending on the reservoir architecture and on the task. This simple and easy process considerably decreases the training complexity compared to traditional RNNs, for which all the weights needed to be optimized. RC algorithms can be programmed using modern traditional processors. But these electronic processors are better suited to digital processing for which a lot of transistors continuously need to be switched on and off, leading to higher power consumption. As we can intuitively understand, processors with hardware directly dedicated to RC operations – in otherwords analog bio-inspired processors – could be much more efficient regarding both speed and power consumption. Based on the same idea of high speed and low power consumption, the last few decades have seen an increasing use of coherent optics in the transport of information thanks to its high bandwidth and high power efficiency advantages. In order to address the future challenge of high performance, high speed, and power efficient nontrivial computing, it is thus natural to turn towards optical implementations of RCs using coherent light. Over the last few years, several physical implementations of RCs using optics and (opto)electronics have been successfully demonstrated. In the present PhD thesis, the reservoirs are based on a large coherently driven linear passive fiber cavity. The internal states are encoded by time-multiplexing in the cavity. Each reservoir state is therefore processed sequentially. This reservoir architecture exhibits many qualities that were either absent or not simultaneously present in previous works: we can perform analog optical signal processing; the easy tunability of each key parameter achieves the best operating point for each task; the system is able to reach a strikingly weak noise floor thanks to the absence of active elements in the reservoir itself; a richer dynamics is provided by operating in coherent light, as the reservoir states are encoded in both the amplitude and the phase of the electromagnetic field; high power efficiency is obtained as a result of the passive nature and simplicity of the setup. However, it is important to note that at this stage we have only obtained low optical power consumption for the reservoir itself. We have not tried to minimize the overall power consumption, including all control electronics. The first experiment reported in chapter 4 uses a quadratic non-linearity on each reservoir state in the output layer. This non-linearity is provided by a readout photodiode since it produces a current proportional to the intensity of the light. On a number of benchmark tasks widely used in the reservoir computing community, the error rates demonstrated with this RC architecture – both in simulation and experimentally – are, to our knowledge, the lowest obtained so far. Furthermore, the analytic model describing our experiment is also of interest, asit constitutes a very simple high performance RC algorithm. The setup reported in chapter 4 requires offline digital post-processing to compute its output signal by summing the weighted reservoir states at each time-step. In chapter 5, we numerically study a realistic model of an optoelectronic “analog readout layer” adapted on the setup presented in chapter 4. This readout layer is based on an RLC low-pass filter acting as an integrator over the weighted reservoir states to autonomously generate the RC output signal. On three benchmark tasks, we obtained very good simulation results that need to be confirmed experimentally in the future. These promising simulation results pave the way for standalone high performance physical reservoir computers.The RC architecture presented in chapter 5 is an autonomous optoelectronic implementation able to electrically generate its output signal. In order to contribute to the challenge of all-optical computing, chapter 6 highlights the possibility of processing information autonomously and optically using an RC based on two coherently driven passive linear cavities. The first one constitutes the reservoir itself and pumps the second one, which acts as an optical integrator onthe weighted reservoir states to optically generate the RC output signal after sampling. A sine non-linearity is implemented on the input signal, whereas both the reservoir and the readout layer are kept linear. Let us note that, because the non-linearity in this system is provided by a Mach-Zehnder modulator on the input signal, the input signal of this RC configuration needs to be an electrical signal. On the contrary, the RC implementation presented in chapter 5 processes optical input signals, but its output is electrical. We obtained very good simulation results on a single task and promising experimental results on two tasks. At the end of this chapter, interesting perspectives are pointed out to improve the performance of this challenging experiment. This system constitutes the first autonomous photonic RC able to optically generate its output signal.
Doctorat en Sciences de l'ingénieur et technologie
info:eu-repo/semantics/nonPublished

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Denis-Le, Coarer Florian. „Neuromorphic computing using nonlinear ring resonators on a Silicon photonic chip“. Electronic Thesis or Diss., CentraleSupélec, 2020. http://www.theses.fr/2020CSUP0001.

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Avec les volumes exponentiels de données numériques générées chaque jour, un besoin de traitement des données en temps réel et économe en énergie s'est fait sentir. Ces défis ont motivé la recherche sur le traitement non conventionnel de l'information. Parmi les techniques existantes, l'apprentissage machine est un paradigme très efficace de l'informatique cognitive. Il fournit, au travers de nombreuses implémentations dont celle des réseaux de neurones artificiels, un ensemble de techniques pour apprendre à un ordinateur ou un système physique à effectuer des tâches complexes, telles que la classification, la reconnaissance de formes ou la génération de signaux. Le reservoir computing a été proposé il y a une dizaine d'années pour simplifier la procédure d’entraînement du réseau de neurones artificiels. En effet, le réseau est maintenu fixe et seules les connexions entre la couche de lecture et la sortie sont entraînées par une simple régression linéaire. L'architecture interne d’un reservoir computer permet des implémentations au niveau physique, et plusieurs implémentations ont été proposées sur différentes plateformes technologiques, dont les dispositifs photoniques. Le reservoir computing sur circuits intégrés optiques est un candidat très prometteur pour relever ces défis. L’objectif de ce travail de thèse a été de proposer trois architectures différentes de réservoir intégré basées sur l’utilisation des micro-anneaux résonnants. Nous en avons numériquement étudié les performances et mis en évidence des vitesses de traitement de données pouvant atteindre plusieurs dizaines de Gigabit par seconde avec des consommations énergétiques de quelques milliwatt
With the exponential volumes of digital data generated every day, there is a need for real-time, energy-efficient data processing. These challenges have motivated research on unconventional information processing. Among the existing techniques, machine learning is a very effective paradigm of cognitive computing. It provides, through many implementations including that of artificial neural networks, a set of techniques to teach a computer or physical system to perform complex tasks, such as classification, pattern recognition or signal generation. Reservoir computing was proposed about ten years ago to simplify the procedure for training the artificial neural network. Indeed, the network is kept fixed and only the connections between the reading layer and the output are driven by a simple linear regression. The internal architecture of a reservoir computer allows physical implementations, and several implementations have been proposed on different technological platforms, including photonic devices. On-chip reservoir computing is a very promising candidate to meet these challenges. The objective of this thesis work was to propose three different integrated reservoir architectures based on the use of resonant micro-rings. We have digitally studied its performance and highlighted data processing speeds of up to several tens of Gigabits per second with energy consumption of a few milliwatts

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Mwamsojo, Nickson. „Neuromorphic photonic systems for information processing“. Electronic Thesis or Diss., Institut polytechnique de Paris, 2023. http://www.theses.fr/2023IPPAS002.

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Par une utilisation performante de nombreux algorithmes dont les réseaux neuronaux, l'intelligence artificielle révolutionne le développement de la société numérique. Néanmoins, la tendance actuelle dépasse les limites prédites par la loi de Moore et celle de Koomey, ce qui implique des limitations éventuelles des implémentations numériques de ces systèmes. Pour répondre plus efficacement aux besoins calculatoires spécifiques de cette révolution, des systèmes physiques innovants tentent en amont d'apporter des solutions, nommées "neuro-morphiques" puisqu'elles imitent le fonctionnement des cerveaux biologiques. Les systèmes existants sont basés sur des techniques dites de "Reservoir Computing" ou "coherent Ising Machine." Leurs versions photoniques, ont permis de démontrer l'intérêt de ces techniques notamment pour la reconnaissance vocale avec un état de l'art en 2017 attestant de bonnes performances en termes de reconnaissance à un rythme d'1 million de mots par seconde. Nous proposons dans un premier temps une technique d'ajustement automatique des hyperparamètres pour le "Reservoir Computing", accompagnée d'une étude théorique de convergence. Nous proposons ensuite une solution au problème de la détection précoce de la maladie d'Alzheimer de type "Reservoir Computing" optoélectronique. En plus des taux de classifications obtenus meilleurs que l'état de l'art, une étude complète du compromis coût énergétique performance démontre la validité de cette approche. Enfin, le problème de la restauration d'image par maximum de vraisemblance est abordé à l'aide d'une implémentation optoélectronique appropriée de type "coherent Ising Machine"
Artificial Intelligence has revolutionized the scientific community thanks to the advent of a robust computation workforce and Artificial Neural Neural Networks. However, the current implementation trends introduce a rapidly growing demand for computational power surpassing the rates and limitations of Moore's and Koomey's Laws, which implies an eventual efficiency barricade. To respond to these demands, bio-inspired techniques, known as 'neuro-morphic' systems, are proposed using physical devices. Of these systems, we focus on 'Reservoir Computing' and 'Coherent Ising Machines' in our works.Reservoir Computing, for instance, demonstrated its computation power such as the state-of-the-art performance of up to 1 million words per second using photonic hardware in 2017. We propose an automatic hyperparameter tuning algorithm for Reservoir Computing and give a theoretical study of its convergence. Moreover, we propose Reservoir Computing for early-stage Alzheimer's disease detection with a thorough assessment of the energy costs versus performance compromise. Finally, we confront the noisy image restoration problem by maximum a posteriori using an optoelectronic implementation of a Coherent Ising Machine

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Alipour, Motaallem Seyed Payam. „Reconfigurable integrated photonic circuits on silicon“. Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51792.

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Integrated optics as a platform for signal processing offers significant benefits such as large bandwidth, low loss, and a potentially high degree of reconfigurability. Silicon (Si) has unique advantages as a material platform for integration, as well as properties such as a strong thermo-optic mechanism that allows for the realization of highly reconfigurable photonic systems. Chapter 1 is devoted to the discussion of these advantages, and Chapter 2 provides the theoretical background for the analysis of integrated Si-photonic devices. The thermo-optic property of Si, while proving extremely useful in facilitating reconfiguration, can turn into a nuisance when there is a need for thermally stable devices on the photonic chip. Chapter 3 presents a technique for resolving this issue without relying on a dynamic temperature stabilization process. Temperature-insensitive (or “athermal”) Si microdisk resonators with low optical loss are realized by using a polymer overlayer whose thermo-optic property is opposite to that of Si, and TiO2 is introduced as an alternative to polymer to deal with potential CMOS-compatibility issues. Chapter 4 demonstrates an ultra-compact, low-loss, fully reconfigurable, and high-finesse integrated photonic filter implemented on a Si chip, which can be used for RF-photonic as well as purely optical signal processing purposes. A novel, thermally reconfigurable reflection suppressor is presented in Chapter 5 for on-chip feedback elimination which can be critical for mitigating spurious interferences and protecting lasers from disturbance. Chapter 6 demonstrates a novel device for on-chip control of optical fiber polarization. Chapter 7 deals with select issues in the implementation of Si integrated photonic circuits. Chapter 8 concludes the dissertation.

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Mohamed, Abdalla Mohab Sameh. „Reservoir computing in lithium niobate on insulator platforms“. Electronic Thesis or Diss., Ecully, Ecole centrale de Lyon, 2024. http://www.theses.fr/2024ECDL0051.

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Cette étude concerne le calcul par réservoir à retard temporel, en anglais Time-Delay Reservoir Computing (TDRC) dans les plateformes de photonique intégré, en particulier la plateforme Lithium Niobate On Insulator (LNOI). Nous proposons une nouvelle architecture intégrée « tout optique », avec seulement un déphaseur comme paramètre modifiable pouvant atteindre de bonnes performances sur plusieurs tâches de référence de calcul par réservoir. Nous étudions également l'espace de conception de cette architecture et le fonctionnement asynchrone du TDRC, qui s'écarte du cadre plus courant consistant à envisager les ordinateurs TDRC comme des réseaux. En outre, nous suggérons d'exploiter le schéma tout optique pour se passer du masque d'entrée, ce qui permet de contourner la conversion Optique/Electronique/Optique (O/E/O), souvent nécessaire pour appliquer le masque dans les architectures TDRC. Dans des travaux futurs, cela pourra permettre le traitement de signaux entrants en temps réel, éventuellement pour des applications de télécommunication de pointe. Les effets de la lecture électronique de sortie sur cette architecture sont également étudiés. Aussi, nous suggérons d'utiliser la corrélation de Pearson comme une métrique nous permettant de concevoir un réservoir capable de traiter plusieurs tâches en même temps sur le même signal entrant (et éventuellement sur des signaux dans des canaux différents). Les premiers travaux expérimentaux menés à l'université RMIT sont également présentés. Par ces travaux, nous voulons étudier la performance de ces nouvelles architectures TDRC tout en ayant minimisant la complexité du matériel photonique. Pour cela on s’appuiera principalement sur les faibles pertes du LNOI qui permettent l'intégration du guide d'onde de rétroaction, et en utilisant uniquement l'interférence et la conversion d'intensité à la sortie (par le biais d'un photodétecteur) en tant que non-linéarité. Cela constitue une base sur laquelle pourront s’appuyer de futurs travaux étudiant les gains de performance lorsque des non-linéarités supplémentaires sont prises en compte (telles que celles de la plateforme LNOI) et lorsque la complexité globale du système augmente par l'introduction d'un plus grand nombre de paramètres. Ces travaux portent donc sur l'exploration d'une approche informatique non conventionnelle particulière (TDRC), utilisant une technologie particulière (la photonique intégrée), sur une plateforme particulière (LNOI). Ces travaux s'appuient sur l'intérêt croissant pour l'informatique non conventionnelle puisqu'il a été démontré au fil des ans que les ordinateurs numériques ne peuvent plus être une solution unique, en particulier pour les applications émergentes telles que l'intelligence artificielle (IA). Le paysage futur de l'informatique englobera probablement une grande variété de paradigmes informatiques, d'architectures et de hardware, afin de répondre aux besoins d'applications spécialisées croissantes, tout en coexistant avec les ordinateurs numériques qui restent - du moins pour l'instant - mieux adaptés à l'informatique à usage général
This work concerns time-delay reservoir computing (TDRC) in integrated photonic platforms, specifically the Lithium Niobate on Insulator (LNOI) platform. We propose a novel all-optical integrated architecture, which has only one tunable parameter in the form of a phase-shifter, and which can achieve good performance on several reservoir computing benchmark tasks. We also investigate the design space of this architecture and the asynchronous operation, which represents a departure from the more common framework of envisioning time-delay reservoir computers as networks in the stricter sense. Additionally, we suggest to leverage the all-optical scheme to dispense with the input mask, which allows the bypassing of an O/E/O conversion, often necessary to apply the mask in TDRC architectures. In future work, this can allow the processing of real-time incoming signals, possibly for telecom/edge applications. The effects of the output electronic readout on this architecture are also investigated. Furthermore, it is suggested to use the Pearson correlation as a simple way to design a reservoir which can handle multiple tasks at the same time, on the same incoming signal (and possibly on signals in different channels). Initial experimental work carried out at RMIT University is also reported. The unifying theme of this work is to investigate the performance possibilities with minimum photonic hardware requirements, relying mainly on LNOI’s low losses which enables the integration of the feedback waveguide, and using only interference and subsequent intensity conversion (through a photodetector) as the nonlinearity. This provides a base for future work to compare against in terms of performance gains when additional nonlinearities are considered (such as those of the LNOI platform), and when overall system complexity is increased by means of introducing more tunable parameters. Thus, the scope of this work is about the exploration of one particular unconventional computing approach (reservoir computing), using one particular technology (photonics), on one particular platform (lithium niobate on insulator). This work builds on the increasing interest of exploring unconventional computing, since it has been shown over the years that digital computers can no longer be a `one-size-fits-all', especially for emerging applications like artificial intelligence (AI). The future landscape of computing will likely encompass a rich variety of computing paradigms, architectures, and hardware, to meet the needs of rising specialized applications, and all in coexistence with digital computers which remain --- at least for now --- better suited for general-purpose computing

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Baylon, Fuentes Antonio. „Ring topology of an optical phase delayed nonlinear dynamics for neuromorphic photonic computing“. Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2047/document.

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Aujourd'hui, la plupart des ordinateurs sont encore basés sur des concepts développés il y a plus de 60 ans par Alan Turing et John von Neumann. Cependant, ces ordinateurs numériques ont déjà commencé à atteindre certaines limites physiques via la technologie de la microélectronique au silicium (dissipation, vitesse, limites d'intégration, consommation d'énergie). Des approches alternatives, plus puissantes, plus efficaces et moins consommatrices d'énergie, constituent depuis plusieurs années un enjeu scientifique majeur. Beaucoup de ces approches s'inspirent naturellement du cerveau humain, dont les principes opérationnels sont encore loin d'être compris. Au début des années 2000, la communauté scientifique s'est aperçue qu'une modification du réseau neuronal récurrent (RNN), plus simple et maintenant appelée Reservoir Computing (RC), est parfois plus efficace pour certaines fonctionnalités, et est un nouveau paradigme de calcul qui s'inspire du cerveau. Sa structure est assez semblable aux concepts classiques de RNN, présentant généralement trois parties: une couche d'entrée pour injecter l'information dans un système dynamique non-linéaire (Write-In), une seconde couche où l'information d'entrée est projetée dans un espace de grande dimension (appelé réservoir dynamique) et une couche de sortie à partir de laquelle les informations traitées sont extraites par une fonction dite de lecture-sortie. Dans l'approche RC, la procédure d'apprentissage est effectuée uniquement dans la couche de sortie, tandis que la couche d'entrée et la couche réservoir sont fixées de manière aléatoire, ce qui constitue l'originalité principale du RC par rapport aux méthodes RNN. Cette fonctionnalité permet d'obtenir plus d'efficacité, de rapidité, de convergence d'apprentissage, et permet une mise en œuvre expérimentale. Cette thèse de doctorat a pour objectifs d'implémenter pour la première fois le RC photoniques en utilisant des dispositifs de télécommunication. Notre mise en œuvre expérimentale est basée sur un système dynamique non linéaire à retard, qui repose sur un oscillateur électro-optique (EO) avec une modulation de phase différentielle. Cet oscillateur EO a été largement étudié dans le contexte de la cryptographie optique du chaos. La dynamique présentée par de tels systèmes est en effet exploitée pour développer des comportements complexes dans un espace de phase à dimension infinie, et des analogies avec la dynamique spatio-temporelle (tels que les réseaux neuronaux) sont également trouvés dans la littérature. De telles particularités des systèmes à retard ont conforté l'idée de remplacer le RNN traditionnel (généralement difficile à concevoir technologiquement) par une architecture à retard d'EO non linéaire. Afin d'évaluer la puissance de calcul de notre approche RC, nous avons mis en œuvre deux tests de reconnaissance de chiffres parlés (tests de classification) à partir d'une base de données standard en intelligence artificielle (TI-46 et AURORA-2), et nous avons obtenu des performances très proches de l'état de l'art tout en établissant un nouvel état de l'art en ce qui concerne la vitesse de classification. Notre approche RC photonique nous a en effet permis de traiter environ 1 million de mots par seconde, améliorant la vitesse de traitement de l'information d'un facteur supérieur à ~3
Nowadays most of computers are still based on concepts developed more than 60 years ago by Alan Turing and John von Neumann. However, these digital computers have already begun to reach certain physical limits of their implementation via silicon microelectronics technology (dissipation, speed, integration limits, energy consumption). Alternative approaches, more powerful, more efficient and with less consume of energy, have constituted a major scientific issue for several years. Many of these approaches naturally attempt to get inspiration for the human brain, whose operating principles are still far from being understood. In this line of research, a surprising variation of recurrent neural network (RNN), simpler, and also even sometimes more efficient for features or processing cases, has appeared in the early 2000s, now known as Reservoir Computing (RC), which is currently emerging new brain-inspired computational paradigm. Its structure is quite similar to the classical RNN computing concepts, exhibiting generally three parts: an input layer to inject the information into a nonlinear dynamical system (Write-In), a second layer where the input information is projected in a space of high dimension called dynamical reservoir and an output layer from which the processed information is extracted through a so-called Read-Out function. In RC approach the learning procedure is performed in the output layer only, while the input and reservoir layer are randomly fixed, being the main originality of RC compared to the RNN methods. This feature allows to get more efficiency, rapidity and a learning convergence, as well as to provide an experimental implementation solution. This PhD thesis is dedicated to one of the first photonic RC implementation using telecommunication devices. Our experimental implementation is based on a nonlinear delayed dynamical system, which relies on an electro-optic (EO) oscillator with a differential phase modulation. This EO oscillator was extensively studied in the context of the optical chaos cryptography. Dynamics exhibited by such systems are indeed known to develop complex behaviors in an infinite dimensional phase space, and analogies with space-time dynamics (as neural network ones are a kind of) are also found in the literature. Such peculiarities of delay systems supported the idea of replacing the traditional RNN (usually difficult to design technologically) by a nonlinear EO delay architecture. In order to evaluate the computational power of our RC approach, we implement two spoken digit recognition tests (classification tests) taken from a standard databases in artificial intelligence TI-46 and AURORA-2, obtaining results very close to state-of-the-art performances and establishing state-of-the-art in classification speed. Our photonic RC approach allowed us to process around of 1 million of words per second, improving the information processing speed by a factor ~3

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Thraskias, Christos A., Eythimios N. Lallas, Niels Neumann, Laurent Schares, Bert J. Offrein, Ronny Henker, Dirk Plettemeier, Frank Ellinger, Juerg Leuthold und Ioannis Tomkos. „Survey of Photonic and Plasmonic Interconnect Technologies for Intra-Datacenter and High-Performance Computing Communications“. Institute of Electrical and Electronics Engineers (IEEE), 2018. https://tud.qucosa.de/id/qucosa%3A35391.

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Large scale data centers (DC) and high performance computing (HPC) systems require more and more computing power at higher energy efficiency. They are already consuming megawatts of power, and a linear extrapolation of trends reveals that they may eventually lead to unrealistic power consumption scenarios in order to satisfy future requirements (e.g., Exascale computing). Conventional complementary metal oxide semiconductor (CMOS)-based electronic interconnects are not expected to keep up with the envisioned future board-to-board and chip-to-chip (within multi-chip-modules) interconnect requirements because of bandwidth-density and power-consumption limitations. However, low-power and high-speed optics-based interconnects are emerging as alternatives for DC and HPC communications; they offer unique opportunities for continued energy-efficiency and bandwidth-density improvements, although cost is a challenge at the shortest length scales. Plasmonics-based interconnects on the other hand, due to their extremely small size, offer another interesting solution for further scaling operational speed and energy efficiency. At the device-level, CMOS compatibility is also an important issue, since ultimately photonics or plasmonics will have to be co-integrated with electronics. In this paper, we survey the available literature and compare the aforementioned interconnect technologies, with respect to their suitability for high-speed and energy-efficient on-chip and offchip communications. This paper refers to relatively short links with potential applications in the following interconnect distance hierarchy: local group of racks, board to board, module to module, chip to chip, and on chip connections. We compare different interconnect device modules, including low-energy output devices (such as lasers, modulators, and LEDs), photodetectors, passive devices (i.e., waveguides and couplers) and electrical circuitry (such as laserdiode drivers, modulator drivers, transimpedance, and limiting amplifiers). We show that photonic technologies have the potential to meet the requirements for selected HPC and DC applications in a shorter term. We also present that plasmonic interconnect modules could offer ultra-compact active areas, leading to high integration bandwidth densities, and low device capacitances allowing for ultra-high bandwidth operation that would satisfy the application requirements further into the future.

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Marquez, Alfonzo Bicky. „Reservoir computing photonique et méthodes non-linéaires de représentation de signaux complexes : Application à la prédiction de séries temporelles“. Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCD042/document.

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Les réseaux de neurones artificiels constituent des systèmes alternatifs pour effectuer des calculs complexes, ainsi que pour contribuer à l'étude des systèmes neuronaux biologiques. Ils sont capables de résoudre des problèmes complexes, tel que la prédiction de signaux chaotiques, avec des performances à l'état de l'art. Cependant, la compréhension du fonctionnement des réseaux de neurones dans la résolution de problèmes comme la prédiction reste vague ; l'analogie avec une boîte-noire est souvent employée. En combinant la théorie des systèmes dynamiques non linéaires avec celle de l'apprentissage automatique (Machine Learning), nous avons développé un nouveau concept décrivant à la fois le fonctionnement des réseaux neuronaux ainsi que les mécanismes à l'œuvre dans leurs capacités de prédiction. Grâce à ce concept, nous avons pu imaginer un processeur neuronal hybride composé d'un réseaux de neurones et d'une mémoire externe. Nous avons également identifié les mécanismes basés sur la synchronisation spatio-temporelle avec lesquels des réseaux neuronaux aléatoires récurrents peuvent effectivement fonctionner, au-delà de leurs états de point fixe habituellement utilisés. Cette synchronisation a entre autre pour effet de réduire l'impact de la dynamique régulière spontanée sur la performance du système. Enfin, nous avons construit physiquement un réseau récurrent à retard dans un montage électro-optique basé sur le système dynamique d'Ikeda. Celui-ci a dans un premier temps été étudié dans le contexte de la dynamique non-linéaire afin d'en explorer certaines propriétés, puis nous l'avons utilisé pour implémenter un processeur neuromorphique dédié à la prédiction de signaux chaotiques
Artificial neural networks are systems prominently used in computation and investigations of biological neural systems. They provide state-of-the-art performance in challenging problems like the prediction of chaotic signals. Yet, the understanding of how neural networks actually solve problems like prediction remains vague; the black-box analogy is often employed. Merging nonlinear dynamical systems theory with machine learning, we develop a new concept which describes neural networks and prediction within the same framework. Taking profit of the obtained insight, we a-priori design a hybrid computer, which extends a neural network by an external memory. Furthermore, we identify mechanisms based on spatio-temporal synchronization with which random recurrent neural networks operated beyond their fixed point could reduce the negative impact of regular spontaneous dynamics on their computational performance. Finally, we build a recurrent delay network in an electro-optical setup inspired by the Ikeda system, which at first is investigated in a nonlinear dynamics framework. We then implement a neuromorphic processor dedicated to a prediction task

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Pauwels, Jaël. „High performance optical reservoir computing based on spatially extended systems“. Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/331699/3/thesis.pdf.

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In this thesis we study photonic computation within the framework of reservoir computing. Inspired by the insight that the human brain processes information by generating patterns of transient neuronal activity excited by input sensory signals, reservoir computing exploits the transient dynamics of an analogue nonlinear dynamical system to solve tasks that are hard to solve by algorithmic approaches. Harnessing the massive parallelism offered by optics, we consider a generic class of nonlinear dynamical systems which are suitable for reservoir computing and which we label photonic computing liquids. These are spatially extended systems which exhibit dispersive or diffractive signal coupling and nonlinear signal distortion. We demonstrate that a wide range of optical systems meet these requirements and allow for elegant and performant imple- mentations of optical reservoirs. These advances address the limitations of current photonic reservoirs in terms of scalability, ease of implementation and the transition towards truly all-optical computing systems.We start with an abstract presentation of a photonic computing liquid and an in-depth analysis of what makes these kinds of systems function as potent reservoir computers. We then present an experimental study of two photonic reservoir computers, the first based on a diffractive free-space cavity, the second based on a fiber-loop cavity. These systems allow us to validate the promising concept of photonic computing liquids, to investigate the effects of symme- tries in the neural interconnectivity and to demonstrate the effectiveness of weak and distributed optical nonlinearities. We also investigate the ability to recover performance lost due to uncontrolled parameters variations in unstable operating environments by introducing an easily scalable way to expand a reservoir’s output layer. Finally, we show how to exploit random diffraction in a strongly dispersive optical system, including applications in optical telecom- munications. In the conclusion we discuss future perspectives and identify the characteristic of the optical systems that we consider most promising for the future of photonic reservoir computing.
Doctorat en Sciences
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O'Hara, John. „Quantum light with quantum dots in III-V photonic integrated circuits : towards scalable quantum computing architectures“. Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/20113/.

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The work in this thesis is motivated by the goal of creating scalable quantum computers, and equally by the physical understanding that develops alongside and follows from this. The fields of physics and technology are symbiotic, and quantum information processing is a prime example. The field has the potential to test quantum mechanics in new and profound ways. Here we approach the technological problem by building upon the foundations laid by the semiconductor chip manufacturing industry. This architecture is based on the III-V semiconductors Gallium Arsenide and Indium Arsenide. Combining the two we can create chip-embedded atom-like light sources -- quantum dots -- that can produce quantum photonic states in lithographically etched nanoscale waveguides and cavities. We demonstrate the integration of quantum light sources and single-mode beam splitters in the same on-chip device. These are the two primary ingredients that are needed to produce the entangled states that are the basis of this type of quantum computing. Next we look at the quantum light source in more detail, showing that with cavity-enhancement we can significantly mitigate the detrimental dephasing associated with nanostructures. The source can be used as a means to produce coherently scattered photons in the waveguides. More importantly, the on-demand photons obtained from pulsed excitation are more indistinguishable and thus more suitable for quantum information carrying and processing. Through experiments and simulations, we investigate some aspects of single-photon sources under pulsed excitation, including emission rate, emission number probabilities, and indistinguishability. A new technique to measure very short lifetimes is demonstrated and examined theoretically. Finally we look at preliminary steps to extend the platform further. The inclusion of photonic crystals and superconducting nanowires provides on-chip filters and detectors, and etched diode structures enable electrical excitation and tunability of the circuit components. These show some clear paths that the work can continue to evolve along.

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TALA, Mahdi. „CROSS-LAYER SYNTHESIS AND INTEGRATION METHODOLOGY OF WAVELENGTH-ROUTED OPTICAL NETWORKS-ON-CHIP FOR 3D-STACKED PARALLEL COMPUTING SYSTEM“. Doctoral thesis, Università degli studi di Ferrara, 2019. http://hdl.handle.net/11392/2488092.

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In future high-performance computing systems, congruent multiples in GOPS/W are expected more from the improvement of system integration levels (such as 3D stacking or 2.5D integration) rather than from the scaling of device dimensions. The expected outcome will be large chip-scale multiprocessors that will pose unprecedented bandwidth requirements for intra and inter-die communications. In this context, system performance needs to be sustained by a scalable on-chip communication infrastructure capable of delivering large bandwidth capacities and stringent latency requirements in a power efficient fashion. By capitalizing on the latest advances of silicon photonics, optical networks-on-chip (ONoCs) stand out as a promising solution to overcome the interconnect limitations and enable the continued scaling of many-core architectures. With respect to traditional electronic NoCs, they preserve the chip-scale networking paradigm while changing the technology substrate. However, ONoCs currently suffer from a huge gap between device developers and system designers which prevents their "system ability", that is the capability to do system level design with them. A research investment on design automation and on system-level integration methods is the only way to bridge the abstraction gap and enable system designers to work out efficient solutions for the connectivity problem at hand. For this purpose, the thesis aims at improving the "system ability" of a specific family of ONoCs that holds promise of all-optical, predictable and low-latency communications, namely wavelength-routed ONoCs (WRONoCs). In this context, the thesis aims at addressing two correlated aspects of this abstraction gap: 1)On the one hand, the thesis will pursue cross-layer synthesis methodologies to enable the design space exploration and the specification of abstract solutions for the connectivity problem at hand, as well as their refinement into an actual physical structure. This represents a milestone contribution to shed light on a design space which is currently limited to the few topology design points that researchers' intuition was able to unveil. The enabling approach is to bring design automation beyond its electronic roots. 2)On the other hand, the thesis will investigate how to compose silicon nanophotonic networks with the other system-level components. This integration issue is typically overlooked in literature, since it is oversimplified as a stage of E/O and O/E conversion circuits. This thesis demonstrates that the interface of such networks to the electronic part of the system is much more complex than that, and implies a new multi-technology architecture building block that we call "the bridge", with major impact upon the network power budget and performance. In practice, an energy-efficient, low-latency and flexible bridge is designed to connect an ONoC with the baseline electronic NoC in a 3D-stacked parallel computing system. In addition to this, the configuration space of the bridge is explored in terms of aggregate connection data rate and bit-level parallelism in optics, in search for the most energy-efficient configuration for the bridge and for the network as a whole. To expand the configuration space, we add a unique technology optimization plane, where we consider two successive CMOS process nodes (40nm and 28nm) and a high-performance 130nm BiCMOS node. An interesting outcome of the thesis is the characterization of the trade-offs arising from the partitioning of the bridge among these technologies. To pursue the above goals, a systematic approach has been adopted that continuously correlates the design choices at the architectural and / or topological level with the corresponding effects in terms of layout efficiency, power consumption and performance.
L’incremento delle prestazioni e dell’efficienza energetica dei futuri sistemi di elaborazione non sarà raggiunto solo tramite la tradizionale riduzione delle dimensioni dei dispositivi, ma soprattutto attraverso il miglioramento dei metodi di integrazione a livello sistema (come l’integrazione 2.5D o 3D). L’esito di questo trend saranno sistemi multiprocessore ad elevato parallelismo che richiederanno una banda altissima sia per le comunicazioni all’interno del chip sia per quelle tra il chip e l’esterno. In questo contesto, le prestazioni aggregate del sistema dovranno essere sostenute da un'infrastruttura di comunicazione scalabile a livello chip che sia in grado di fornire alte densità di banda, di estendersi alla comunicazione off-chip in modo trasparente, di ridurre la latenza ed il consumo energetico. Considerando i recenti progressi della fotonica del silicio, le reti di interconnessioni ottiche integrate (ONoCs) risultato la tecnologia più promettente per superare il collo di bottiglia della comunicazione e per continuare lo scaling delle architetture many-core esistenti. Rispetto alle tradizionali NoC elettroniche, le ONoCs preservano il paradigma del networking tra gli attori della comunicazione a livello chip, ma cambiano il substrato tecnologico. Tuttavia, le ONoCs attualmente soffrono di un enorme divario tra gli sviluppatori della tecnologia e i progettisti a livello sistema, che impedisce la loro "system-ability", ovvero la capacità di progettare a livello sistema utilizzando questa tecnologia emergente. Un investimento di ricerca sulla automazione della progettazione e sui metodi di integrazione a livello sistema è l'unico modo per colmare il divario e per consentire ai progettisti di fornire soluzioni efficienti e non-intuitive per i problemi di connettività che devono affrontare. A tal fine, la mia tesi di dottorato mira a migliorare la "system-ability" di una specifica famiglia di ONoC, ossia il wavelength-routed (WRONoCs). In particolare, la tesi affronta due aspetti correlati del divario: 1)Da un lato, la tesi persegue metodologie di sintesi ad elevata integrazione verticale per consentire l'esplorazione dello spazio di progetto e la specifica di soluzioni astratte per il problema di connettività sotto esame, oltre al loro raffinamento progressivo in strutture fisiche reali. Questo rappresenta un contributo fondamentale per conoscere uno spazio di progetto che è attualmente limitato ai pochi punti che l’intuizione dei ricercatori riesce a concepire. Ultimamente, questo approccio consiste nel portare la consolidata disciplina dell’automazione della progettazione oltre le sue radici elettroniche. 2)D'altro lato, la tesi studia il metodo di integrare le reti nanofotoniche al silicio con gli altri componenti a livello architetturale. Questo problema di integrazione “orizzontale” è tipicamente trascurato dalla letteratura scientifica, poiché è risolto in maniera semplicistica tramite uno stadio di circuiti di conversione da elettronica a ottica (E/O) e viceversa (O/E). Questa tesi dimostra che l'interfacciamento di tali reti con la parte elettronica del sistema è molto più complesso di questo modello semplificato, dal momento che richiede la progettazione di un nuovo blocco architetturale implementato mediante tecnologie potenzialmente eterogenee, e che ho chiamato " Bridge". Questo bridge in realtà ha un impatto significativo sul bilancio energetico e sulle prestazioni dell’intera rete ottica integrata. La mia tesi ha esplorato lo spazio delle configurazioni del bridge in un piano di ottimizzazione bidimensionale che include la velocità di trasmissione complessiva di un segnale ottico ed il livello di parallelismo dei dati su una connessione, con lo scopo di quantificare i trade-off performance-energia sia per il bridge sia per la rete completa.

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Spring, Justin Benjamin. „Single photon generation and quantum computing with integrated photonics“. Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:b08937c7-ec87-47f8-b5ac-902673f87ce2.

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Photonics has consistently played an important role in the investigation of quantum-enhanced technologies and the corresponding study of fundamental quantum phenomena. The majority of these experiments have relied on the free space propagation of light between bulk optical components. This relatively simple and flexible approach often provides the fastest route to small proof-of-principle demonstrations. Unfortunately, such experiments occupy significant space, are not inherently phase stable, and can exhibit significant scattering loss which severely limits their use. Integrated photonics offers a scalable route to building larger quantum states of light by surmounting these barriers. In the first half of this thesis, we describe the operation of on-chip heralded sources of single photons. Loss plays a critical role in determining whether many quantum technologies have any hope of outperforming their classical analogues. Minimizing loss leads us to choose Spontaneous Four-Wave Mixing (SFWM) in a silica waveguide for our source design; silica exhibits extremely low scattering loss and emission can be efficiently coupled to the silica chips and fibers that are widely used in quantum optics experiments. We show there is a straightforward route to maximizing heralded photon purity by minimizing the spectral correlations between emitted photon pairs. Fabrication of identical sources on a large scale is demonstrated by a series of high-visibility interference experiments. This architecture offers a promising route to the construction of nonclassical states of higher photon number by operating many on-chip SFWM sources in parallel. In the second half, we detail one of the first proof-of-principle demonstrations of a new intermediate model of quantum computation called boson sampling. While likely less powerful than a universal quantum computer, boson sampling machines appear significantly easier to build and may allow the first convincing demonstration of a quantum-enhanced computation in the not-distant future. Boson sampling requires a large interferometric network which are challenging to build with bulk optics, we therefore perform our experiment on-chip. We model the effect of loss on our postselected experiment and implement a circuit characterization technique that accounts for this loss. Experimental imperfections, including higher-order emission from our photon pair sources and photon distinguishability, are modeled and found to explain the sampling error observed in our experiment.

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Antonik, Piotr. „Application of FPGA to real-time machine learning: hardware reservoir computers and software image processing“. Doctoral thesis, Universite Libre de Bruxelles, 2017. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/257660.

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Reservoir computing est un ensemble de techniques permettant de simplifierl’utilisation des réseaux de neurones artificiels. Les réalisations expérimentales,notamment optiques, de ce concept ont montré des performances proches de l’étatde l’art ces dernières années. La vitesse élevée des expériences optiques ne permetpas d’y intervenir en temps réel avec un ordinateur standard. Dans ce travail, nousutilisons une carte de logique programmable (Field-Programmable Gate Array, ouFPGA) très rapide afin d’interagir avec l’expérience en temps réel, ce qui permetde développer de nouvelles fonctionnalités.Quatre expériences ont été réalisées dans ce cadre. La première visait à implé-menter un algorithme de online training, permettant d’optimiser les paramètresdu réseau de neurones en temps réel. Nous avons montré qu’un tel système étaitcapable d’accomplir des tâches réalistes dont les consignes variaient au cours dutemps.Le but de la deuxième expérience était de créer un reservoir computer optiquepermettant l’optimisation de ses poids d’entrée suivant l’algorithme de backpropaga-tion through time. L’expérience a montré que cette idée était tout à fait réalisable,malgré les quelques difficultés techniques rencontrées. Nous avons testé le systèmeobtenu sur des tâches complexes (au-delà des capacités de reservoir computers clas-siques) et avons obtenu des résultats proches de l’état de l’art.Dans la troisième expérience nous avons rebouclé notre reservoir computer op-tique sur lui-même afin de pouvoir générer des séries temporelles de façon autonome.Le système a été testé avec succès sur des séries périodiques et des attracteurs chao-tiques. L’expérience nous a également permis de mettre en évidence les effets debruit expérimental dans les systèmes rebouclés.La quatrième expérience, bien que numérique, visait le développement d’unecouche de sortie analogique. Nous avons pu vérifier que la méthode de onlinetraining, développée précédemment, était robuste contre tous les problèmes expéri-mentaux étudiés. Par conséquent, nous avons toutes les informations pour réalisercette idée expérimentalement.Finalement, durant les derniers mois de ma thèse, j’ai effectué un stage dont lebut était d’appliquer mes connaissance en programmation de FPGA et réseaux deneurones artificiels à un problème concret en imagerie cardiovasculaire. Nous avonsdéveloppé un programme capable d’analyser les images en temps réel, convenablepour des applications cliniques.
Doctorat en Sciences
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Li, Zhen. „Reconfigurable computing architecture exploration using silicon photonics technology“. Thesis, Ecully, Ecole centrale de Lyon, 2015. http://www.theses.fr/2015ECDL0001/document.

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Les progrès dans la fabrication des systèmes de calcul reconfigurables de type « Field Programmable Gate Arrays » (FPGA) s’appuient sur la technologie CMOS, ce qui engendre une consommation des puces élevée. Des nouveaux paradigmes de calcul sont désormais nécessaires pour remplacer les architectures de calcul traditionnel ayant une faible performance et une haute consommation énergétique. En particulier, optique intégré pourrait offrir des solutions intéressantes. Beaucoup de travail sont déjà adressées à l’utilisation d’interconnexion optique pour relaxer les contraintes intrinsèques d’interconnexion électronique. Dans ce contexte, nous proposons une nouvelle architecture de calcul reconfigurable optique, la « optical lookup table » (OLUT), qui est une implémentation optique de la lookup table (LUT). Elle améliore significativement la latence et la consommation énergétique par rapport aux architectures de calcul d’optique actuelles tel que RDL (« reconfigurable directed logic »), en utilisant le spectre de la lumière au travers de la technologie WDM. Nous proposons une méthodologie de conception multi-niveaux permettant l'explorer l’espace de conception et ainsi de réduire la consommation énergétique tout en garantissant une fiabilité élevée des calculs (BER~10-18). Les résultats indiquent que l’OLUT permet une consommation inférieure à 100fJ/opération logique, ce qui répondait en partie aux besoins d’un FPGA tout-optique à l’avenir
Advances in the design of high performance silicon chips for reconfigurable computing, i.e. Field Programmable Gate Arrays (FPGAs), rely on CMOS technology and are essentially limited by energy dissipation. New design paradigms are mandatory to replace traditional, slow and power consuming, electronic computing architectures. Integrated optics, in particular, could offer attractive solutions. Many related works already addressed the use of optical on-chip interconnects to help overcome the technology limitations of electrical interconnects. Integrated silicon photonics also has the potential for realizing high performance computing architectures. In this context, we present an energy-efficient on-chip reconfigurable photonic logic architecture, the so-called OLUT, which is an optical core implementation of a lookup table. It offers significant improvement in latency and power consumption with respect to optical directed logic architectures, through allowing the use of wavelength division multiplexing (WDM) for computation parallelism. We proposed a multi-level modeling approach based on the design space exploration that elucidates the optical device characteristics needed to produce a computing architecture with high computation reliability (BER~10-18) and low energy dissipation. Analytical results demonstrate the potential of the resulting OLUT implementation to reach <100 fJ/bit per logic operation, which may meet future demands for on-chip optical FPGAs

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Lee, James. „Photon sources for linear optical quantum computing“. Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287474.

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Quantum photonic technologies have many exciting applications including secure commu- nication, quantum enhanced measurement and quantum computing. Linear optical quantum computing (LOQC) is a technology of particular interest - especially given that recent progress in on-chip waveguide technology removes the requirement for complex and costly bulk optics setups and state-of-the-art detectors have detection efficiencies of over 90%. Arguably the largest remaining technological hurdle for LOQC is the development of a suitable photon source. A suitable source would produce single, indistinguishable photons deterministically. Additionally, it would be beneficial if the generated photons were entangled, as this can significantly reduce the degree of multiplexing needed to implement LOQC. Quantum dots are a suitable candidate system for these photon sources as they exhibit bright single photon emission and can act as the interface between light and a trapped spin qubit. These properties have resulted in proposals to generate multi-photon entangled states suitable for use in LOQC. This thesis presents some of the progress we have made towards the creation of a suitable photon source. After introducing the background material, we demonstrate pulsed resonant excitation using a single-electron-charged quantum dot. Deterministic excitation is demonstrated by performing Rabi oscillations and Ramsey interference in the excitonic population. We also investigate Ramsey interference in a Faraday geometry magnetic field and observe a variety of beats and oscillations in the interferograms. We develop a model to explain our results and conclude that controlling the phase between the two Ramsey interference pulses allows a degree of control over the state of the trapped spin. We then also demonstrate the coherent optical manipulation of a trapped spin in a Voigt geometry magnetic field. Once we have presented the manipulation of the excitonic state and the state of the trapped spin, we proceed to investigate the properties of the light produced by the resonant excitation of a quantum dot. Hong Ou Mandel interference experiments allow us to probe the indistinguishability of the photons resulting from the resonant excitation of the negative trion transition. Repeating the measurement using light generated from a similar system (this time with a trapped hole rather than a trapped electron) that is embedded in a micropillar cavity, we find that the cavity enhancement of the transition results is higher indistinguishabilities. We make use of this bright source of indistinguishable photons to perform an on-chip quantum enhanced measurement and observe the phase superresolution associated with N00N states. In the final experimental chapter, we propose and implement a scheme to generate multi- qubit single photon states. We show that by repeatedly driving a micropillar-cavity-enhanced Raman transition of a single-hole-charged quantum dot in a Voigt geometry magnetic field it is possible to coherently superpose a photon across multiple time bins. The scheme is conceptually similar to proposed schemes for producing multi-photon entangled states. Lastly, we propose a scheme that makes use of the capabilities shown in the three experimental chapters to overcome several of the experimental difficulties associated with generating multi-photon entangled states.

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Bazzanella, Davide. „Microring Based Neuromorphic Photonics“. Doctoral thesis, Università degli studi di Trento, 2022. http://hdl.handle.net/11572/344624.

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This manuscript investigates the use of microring resonators to create all-optical reservoir-computing networks implemented in silicon photonics. Artificial neural networks and reservoir-computing are promising applications for integrated photonics, as they could make use of the bandwidth and the intrinsic parallelism of optical signals. This work mainly illustrates two aspects: the modelling of photonic integrated circuits and the experimental results obtained with all-optical devices. The modelling of photonic integrated circuits is examined in detail, both concerning fundamental theory and from the point of view of numerical simulations. In particular, the simulations focus on the nonlinear effects present in integrated optical cavities, which increase the inherent complexity of their optical response. Toward this objective, I developed a new numerical tool, precise, which can simulate arbitrary circuits, taking into account both linear propagation and nonlinear effects. The experimental results concentrate on the use of SCISSORs and a single microring resonator as reservoirs and the complex perceptron scheme. The devices have been extensively tested with logical operations, achieving bit error rates of less than 10^−5 at 16 Gbps in the case of the complex perceptron. Additionally, an in-depth explanation of the experimental setup and the description of the manufactured designs are provided. The achievements reported in this work mark an encouraging first step in the direction of the development of novel networks that employ the full potential of all-optical devices.

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Holleczek, Annemarie. „Linear optics quantum computing with single photons from an atom-cavity system“. Thesis, University of Oxford, 2016. http://ora.ox.ac.uk/objects/uuid:d655fa1c-3405-413d-8af8-eecf6212ab74.

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One of today’s challenges to realise computing based on quantum mechanics is to reliably and scalably encode information in quantum systems. Here, we present a photon source to on-demand deliver photonic quantum bits of information based on a strongly coupled atom-cavity system. The source operates intermittently for periods of up to 100 μs, with a single-photon repetition rate of 1 MHz, and an intra-cavity production efficiency of up to 85%. Our ability to arbitrarily control the photons’ wavepackets and phase profiles, together with long coherence times of 500 ns, allows to store time-bin encoded quantum information within a single photon. To do so, the spatio-temporal envelope of a single photon is sub-divided in d time bins which allows for the delivery of arbitrary qu-d-its. This is done with a fidelity of > 95% for qubits, and 94% for qutrits verified using a newly developed time-resolved quantum-homodyne measurement technique. Additionally, we combine two separate fields of quantum physics by using our deterministic single-photon source to seed linear optics quantum computing (LOQC) circuits. As a step towards quantum networking, it is shown that this photon source can be combined with quantum gates, namely a chip-integrated beam splitter, a controlled-NOT (CNOT) gate as well as a CNOT4 gate. We use this CNOT4 gate to entangle photons deterministically emitted from our source and observe non-classical correlations between events separated by periods exceeding the travel time across the chip by three orders of magnitude. Additionally, we use time-bin encoded qubits to systematically study the de- and re-phasing of quantum states as well as the the effects of time-varying internal phases in photonic quantum circuits.

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Floether, Frederik. „Development of SiOxNy waveguides for integrated quantum photonics“. Thesis, University of Cambridge, 2015. https://www.repository.cam.ac.uk/handle/1810/253107.

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The development of integrated quantum photonics is integral to many areas of quantum information science, in particular linear optical quantum computing. In this context, a diversity of physical systems is being explored and thus versatility and adaptability are important prerequisites for any candidate platform. Silicon oxynitride is a promising material because its refractive index can be varied over a wide range. This dissertation describes the development of silicon oxynitride waveguides for applications in the field of integrated quantum photonics. The project consisted of three stages: design, characterisation, and application. First, the parameter space was studied through simulations. The structures were optimised to achieve low-loss devices with a small footprint at a wavelength of 900 nm. Buried channel waveguides with a cross-section of 1.6 ?m x 1.6 ?m and a core (cladding) refractive index of 1.545 (1.505) were chosen. Second, following their fabrication with plasma-enhanced chemical vapour deposition, electron beam lithography, and reactive ion etching, the waveguides were characterised. The refractive index was shown to be tunable from the silica to the silicon nitride regime. Optimised tapers significantly improved the coupling efficiency. The minimum bend radius was measured to be less than 2 mm. Propagation losses as low as 1.45 dB cm-1 were achieved. Directional couplers with coupling ratios ranging from 0 to 1 were realised. Third, building blocks for linear optical quantum computing were demonstrated. Reconfigurable quantum circuits consisting of Mach-Zehnder interferometers with near perfect visibilities were fabricated along with a four-port switch. The potential of quantum speedup was illustrated by carrying out the Deutsch-Jozsa algorithm with a fidelity of 100 % using on-demand single photons from a quantum dot. This dissertation presents the first implementation of tunable Mach-Zehnder interferometers, which act on single photons, based on silicon oxynitride waveguides. Furthermore, for the first time silicon oxynitride photonic quantum circuits were operated with on-demand single photons. Accordingly, this work has created a platform for the development of integrated quantum photonics.

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Masominia, Amir Hossein. „Neuro-inspired computing with excitable microlasers“. Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP053.

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Cette thèse présente des recherches sur des systèmes de calcul alternatifs, en se concentrant spécifiquement sur le calcul analogique et neuromimétique. La quête d'une intelligence artificielle plus générale a mis en évidence les limitations des unités de calcul conventionnelles basées sur les architectures de Von Neumann, en particulier en termes d'efficacité énergétique et de complexité. Les architectures de calcul inspirées du cerveau et les ordinateurs analogiques sont des prétendants de premier plan dans ce domaine. Parmi les différentes possibilités, les systèmes photoniques impulsionnels (spiking) offrent des avantages significatifs en termes de vitesse de traitement, ainsi qu'une efficacité énergétique accrue. Nous proposons une approche novatrice pour les tâches de classification et de reconnaissance d'images en utilisant un laser à micropilier développé en interne fonctionnant comme un neurone artificiel. La non-linéarité du laser excitable, résultant des dynamiques internes, permet de projeter les informations entrantes, injectées optiquement dans le micropilier au travers de son gain, dans des dimensions supérieures. Cela permet de trouver des régions linéairement séparables pour la classification. Le micropilier laser excitable présente toutes les propriétés fondamentales d'un neurone biologique, y compris l'excitabilité, la période réfractaire et l'effet de sommation, avec des échelles caractéristiques de fonctionnement sous la nanoseconde. Cela en fait un candidat de premier choix dans les systèmes impulsionnels où la dynamique de l'impulsion elle-même porte des informations, par opposition aux systèmes qui considèrent uniquement la fréquence moyenne des impulsions. Nous avons conçu et étudié plusieurs systèmes utilisant le micropilier laser, basés sur un calculateur à réservoir à nœud physique unique qui émule un calculateur à plusieurs noeuds et utilisant différents régimes dynamiques du microlaser. Ces systèmes ont atteint des performances de reconnaissance plus élevées par rapport aux systèmes sans le microlaser. De plus, nous introduisons un nouveau modèle inspiré des champs réceptifs dans le cortex visuel, capable de classifier un ensemble de chiffres tout en éliminant le besoin d'un ordinateur conventionnel dans le processus. Ce système a été mis en œuvre expérimentalement avec succès en utilisant une configuration optique combinée en espace libre et fibrée, ouvrant des perspectives intéressantes pour le calcul analogue ultra-rapide sur architecture matérielle
This thesis presents research on alternative computing systems, with a focus on analog and neuromimetic computing. The pursuit of more general artificial intelligence has underscored limitations in conventional computing units based on Von Neumann architectures, particularly regarding energy efficiency and complexity. Brain-inspired computing architectures and analog computers are key contenders in this field. Among the various proposed methods, photonic spiking systems offer significant advantages in processing and communication speeds, as well as potential energy efficiency. We propose a novel approach to classification and image recognition tasks using an in-house developed micropillar laser as the artificial neuron. The nonlinearity of the spiking micropillar laser, resulting from the internal dynamics of the system, allows for mapping incoming information, optically injected to the micropillar through gain, into higher dimensions. This enables finding linearly separable regions for classification. The micropillar laser exhibits all fundamental properties of a biological neuron, including excitability, refractory period, and summation effect, with sub-nanosecond characteristic timescales. This makes it a strong candidate in spiking systems where the dynamics of the spike itself carries information, as opposed to systems that consider spiking rates only. We designed and studied several systems using the micropillar laser, based on a reservoir computer with a single physical node that emulates a reservoir computer with several nodes, using different dynamical regimes of the microlaser. These systems achieved higher performance in prediction accuracy of the classes compared to systems without the micropillar. Additionally, we introduce a novel system inspired by receptive fields in the visual cortex, capable of classifying a digit dataset entirely online, eliminating the need for a conventional computer in the process. This system was successfully implemented experimentally using a combined fiber and free-space optical setup, opening promising prospects for ultra-fast, hardware based feature selection and classification systems

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Nisbet-Jones, Peter. „Shaping single photons“. Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:c75d4896-c5a8-42b8-a166-ffcd4166fc09.

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The possibility of creating a scaleable quantum network by interconverting photonic and atomic qubits shows great promise. The fundamental requirement for such a network is deterministic control over the emission and absorption of photons from single atoms. This thesis reports on the experi-mental construction of a photon source that can emit single-photons with arbitrary spatio-temporal shape, phase, and frequency. The photon source itself is a strongly-coupled atom cavity system based on a single ⁸⁷ Rb atom within a macroscopic high-finesse Fabry-Perot cavity. It operates intermittently for periods of up to 100µs, with single-photon repetition rates of 1.0 MHz and an efficiency of almost 80%. Atoms are loaded into the cavity using an atomic fountain, with the upper turning point near the centre of the cavity mode. This ensures long interaction times without any disturbances introduced by trapping potentials. The photons’ indistinguishability was tested, with a two-photon Hong-Ou-Mandel visibility of 87%. This ability to both generate, and control, the photons’ properties, for example producing photons with symmetric or multi-peaked spatio-temporal shapes, allows for the production of photons in an n-time-bin superposition state where each time-bin has an arbitrarily defined amplitude and phase. These photons can be used as photonic qubits, qutrits and qquads, and their properties have been tested using a small linear-optics network.

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Patel, Meena. „Numerical study of non-linear spectroscopy and four-wave-mixing in two and multi-level atoms“. Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2623.

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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018.
In this research, we undertake a numerical study of the interaction between laser beams and two as well as multi-level atoms. The main aim of this research is to obtain a deeper understanding of laser-atom interactions and non-linear processes such as optical four-wave mixing. This work will supplement experiments to be conducted by other members of the group, who are involved in generating entangled photons via four-wave mixing in cold rubidium atoms. We begin by performing a basic study of the interaction between laser beams and two-level atoms as an aid to gain knowledge of numerical techniques, as well as an understanding of the physics behind light-atom interactions. We make use of a semi-classical approach to describe the system where the atoms are treated quantum mechanically and the laser beams are treated classically. We study the interaction between atoms and laser beams using the density matrix operator and Maxwell's equations respectively. By solving the optical Bloch equations for two-level atoms we examine the atomic populations and coherences and present plots of the density matrix elements as a function of time. The e ects of various parameters such as laser intensity, detuning and laser modulation have been tested. The behaviour of the laser beam as it propagates through the atomic sample is also studied. This is determined by Maxwell's equation where the atomic polarization is estimated from the coherence terms of the density matrix elements.
French South African Institute of Technology National Research Foundation

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Sinha, Raju. „Tunable, Room Temperature THz Emitters Based on Nonlinear Photonics“. FIU Digital Commons, 2017. http://digitalcommons.fiu.edu/etd/3172.

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The Terahertz (1012 Hz) region of the electromagnetic spectrum covers the frequency range from roughly 300 GHz to 10 THz, which is in between the microwave and infrared regimes. The increasing interest in the development of ultra-compact, tunable room temperature Terahertz (THz) emitters with wide-range tunability has stimulated in-depth studies of different mechanisms of THz generation in the past decade due to its various potential applications such as biomedical diagnosis, security screening, chemical identification, life sciences and very high speed wireless communication. Despite the tremendous research and development efforts, all the available state-of-the-art THz emitters suffer from either being large, complex and costly, or operating at low temperatures, lacking tunability, having a very short spectral range and a low output power. Hence, the major objective of this research was to develop simple, inexpensive, compact, room temperature THz sources with wide-range tunability. We investigated THz radiation in a hybrid optical and THz micro-ring resonators system. For the first time, we were able to satisfy the DFG phase matching condition for the above-mentioned THz range in one single device geometry by employing a modal phase matching technique and using two separately designed resonators capable of oscillating at input optical waves and generated THz waves. In chapter 6, we proposed a novel plasmonic antenna geometry – the dimer rod-tapered antenna (DRTA), where we created a hot-spot in the nanogap between the dimer arms with a very large intensity enhancement of 4.1×105 at optical resonant wavelength. Then, we investigated DFG operation in the antenna geometry by incorporating a nonlinear nanodot in the hot-spot of the antenna and achieved continuously tunable enhanced THz radiation across 0.5-10 THz range. In chapter 8, we designed a multi-metallic resonators providing an ultrasharp toroidal response at THz frequency, then fabricated and experimentally demonstrated an efficient polarization dependent plasmonic toroid switch operating at THz frequency. In summary, we have successfully designed, analytically and numerically investigated novel THz emitters with the advantages of wide range tunability, compactness, room temperature operation, fast modulation and the possibility for monolithic integration, which are the most sought after properties in the new generation THz sources.

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Lamoureux, Louis-Philippe. „Theoretical and experimental aspects of quantum cryptographic protocols“. Doctoral thesis, Universite Libre de Bruxelles, 2006. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210776.

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La mécanique quantique est sans aucun doute la théorie la mieux vérifiée qui n’a jamais existée. En se retournant vers le passé, nous constatons qu’un siècle de théorie quantique a non seulement changé la perception que nous avons de l’univers dans lequel nous vivons mais aussi est responsable de plusieurs concepts technologiques qui ont le potentiel de révolutionner notre monde.

La présente dissertation a pour but de mettre en avance ces potentiels, tant dans le domaine théorique qu’expérimental. Plus précisément, dans un premier temps, nous étudierons des protocoles de communication quantique et démontrerons que ces protocoles offrent des avantages de sécurité qui n’ont pas d’égaux en communication classique. Dans un deuxième temps nous étudierons trois problèmes spécifiques en clonage quantique ou chaque solution

apportée pourrait, à sa façon, être exploitée dans un problème de communication quantique.

Nous débuterons par décrire de façon théorique le premier protocole de communication quantique qui a pour but la distribution d’une clé secrète entre deux parties éloignées. Ce chapitre nous permettra d’introduire plusieurs concepts et outils théoriques qui seront nécessaires dans les chapitres successifs. Le chapitre suivant servira aussi d’introduction, mais cette fois-ci penché plutôt vers le côté expériemental. Nous présenterons une élégante technique qui nous permettra d’implémenter des protocoles de communication quantique de façon simple. Nous décrirons ensuite des expériences originales de communication quantique basées sur cette technique. Plus précisément, nous introduirons le concept de filtration d’erreur et utiliserons cette technique afin d’implémenter une distribution de clé quantique bruyante qui ne pourrait pas être sécurisé sans cette technique. Nous démontrerons ensuite des expériences implémentant le tirage au sort quantique et d’identification quantique.

Dans un deuxième temps nous étudierons des problèmes de clonage quantique basé sur le formalisme introduit dans le chapitre d’introduction. Puisqu’il ne sera pas toujours possible de prouver l’optimalité de nos solutions, nous introduirons une technique numérique qui nous

permettra de mettre en valeur nos résultats.

Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished

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Conterio, Michael John. „An electrically driven resonant tunnelling semiconductor quantum dot single photon source“. Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708597.

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Barter, Oliver. „Deterministic quantum feedback control in probabilistic atom-photon entanglement“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:9faa5f68-39fa-4bd2-9362-785b3cd0111e.

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The prospect of a universal quantum computer is alluring, yet formidable. Smaller scale quantum information processing, however, has been demonstrated. Quantum networks, interlinking flying and stationary qubits, and linear optical quantum computing (LOQC) are both good candidates for scaling up such computations. A strongly coupled atom-cavity system is a promising approach for applications in these fields, both as a node in a quantum network, and as a source of photons for LOQC. This thesis demonstrates the versatile capabilities of an atom-cavity system comprising a single ⁸⁷Rb atom within a macroscopic high-finesse Fabry-Pérot cavity. It operates intermittently for periods of up to 100 μs, with single-photon repetition rates of 1 MHz and an intra-cavity production efficiency of up to 85%. Exploiting the long coherence time of around 500 ns, the photons are subdivided into d time bins, with arbitrary amplitudes and phases, thus encoding arbitrary qudits. High fidelity quantum logic is shown, operating a controlled-NOT gate integrated into a photonic chip with a classical fidelity of 95.9^+1.4_-1.7 %. Additionally, the generation of entanglement is verified and non-classical correlations between events separated by periods exceeding the travel time across the chip by three orders of magnitude are observed. Photonic quantum simulation is performed, using temporally encoded qudits to mimic the correlation statistics of both fermions and anyons, in addition to bosons. Finally measurement-based quantum feedback is demonstrated and used to actively control the routing of temporal qubits.

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Sampath, Vimal G. „ULTRA–LOW POWER STRAINTRONIC NANOMAGNETIC COMPUTING WITH SAW WAVES: AN EXPERIMENTAL STUDY OF SAW INDUCED MAGNETIZATION SWITCHING AND PROPERTIES OF MAGNETIC NANOSTRUCTURES“. VCU Scholars Compass, 2016. http://scholarscompass.vcu.edu/etd/4617.

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A recent International Technology Roadmap for Semiconductors (ITRS) report (2.0, 2015 edition) has shown that Moore’s law is unlikely to hold beyond 2028. There is a need for alternate devices to replace CMOS based devices, if further miniaturization and high energy efficiency is desired. The goal of this dissertation is to experimentally demonstrate the feasibility of nanomagnetic memory and logic devices that can be clocked with acoustic waves in an extremely energy efficient manner. While clocking nanomagnetic logic by stressing the magnetostrictive layer of a multiferroic logic element with with an electric field applied across the piezoelectric layer is known to be an extremely energy-efficient clocking scheme, stressing every nanomagnet separately requires individual contacts to each one of them that would necessitate cumbersome lithography. On the other hand, if all nanomagnets are stressed simultaneously with a global voltage, it will eliminate the need for individual contacts, but such a global clock makes the architecture non-pipelined (the next input bit cannot be written till the previous bit has completely propagated through the chain) and therefore, unacceptably slow and error prone. Use of global acoustic wave, that has in-built granularity, would offer the best of both worlds. As the crest and the trough propagate in space with a velocity, nanomagnets that find themselves at a crest are stressed in tension while those in the trough are compressed. All other magnets are relaxed (no stress). Thus, all magnets are not stressed simultaneously but are clocked in a sequentially manner, even though the clocking agent is global. Finally, the acoustic wave energy is distributed over billions of nanomagnets it clocks, which results in an extremely small energy cost per bit per nanomagnet. In summary, acoustic clocking of nanomagnets can lead to extremely energy efficient nanomagnetic computing devices while also eliminating the need for complex lithography. The dissertation work focuses on the following two topics: Acoustic Waves, generated by IDTs fabricated on a piezoelectric lithium niobate substrate, can be utilized to manipulate the magnetization states in elliptical Co nanomagnets. The magnetization switches from its initial single-domain state to a vortex state after SAW stress cycles propagate through the nanomagnets. The vortex states are stable and the magnetization remains in this state until it is ‘reset’ by an external magnetic field. 2. Acoustic Waves can also be utilized to induce 1800 magnetization switching in dipole coupled elliptical Co nanomagnets. The magnetization switches from its initial single-domain ‘up’ state to a single-domain ‘down’ state after SAW tensile/compressive stress cycles propagate through the nanomagnets. The switched state is stable and non-volatile. These results show the effective implementation of a Boolean NOT gate. Ultimately, the advantage of this technology is that it could also perform higher order information processing (not discussed here) while consuming extremely low power. Finally, while we have demonstrated acoustically clocked nanomagnetic memory and logic schemes with Co nanomagnets, materials with higher magnetostriction (such as FeGa) may ultimately improve the switching reliability of such devices. With this in mind we prepared and studied FeGa films using a ferromagnetic resonance (FMR) technique to extract properties of importance to magnetization dynamics in such materials that could have higher magneto elastic coupling than either Co or Ni.

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Dilley, Jerome Alexander Martin. „A single-photon source for quantum networking“. Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:380a4aaf-e809-4fff-84c7-5b6a0856a6cf.

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Cavity quantum electrodynamics (cavity QED) with single atoms and single photons provides a promising route toward scalable quantum information processing (QIP) and computing. A strongly coupled atom-cavity system should act as a universal quantum interface, allowing the generation and storage of quantum information. This thesis describes the realisation of an atom-cavity system used for the production and manipulation of single photons. These photons are shown to exhibit strong sub-Poissonian statistics and indistinguishability, both prerequisites for their use in realistic quantum systems. Further, the ability to control the temporal shape and internal phase of the photons, as they are generated in the cavity, is demonstrated. This high degree of control presents a novel mechanism enabling the creation of arbitrary photonic quantum bits.

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Johnson, Buxton L. Sr. „HYBRID PARALLELIZATION OF THE NASA GEMINI ELECTROMAGNETIC MODELING TOOL“. UKnowledge, 2017. http://uknowledge.uky.edu/ece_etds/99.

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Understanding, predicting, and controlling electromagnetic field interactions on and between complex RF platforms requires high fidelity computational electromagnetic (CEM) simulation. The primary CEM tool within NASA is GEMINI, an integral equation based method-of-moments (MoM) code for frequency domain electromagnetic modeling. However, GEMINI is currently limited in the size and complexity of problems that can be effectively handled. To extend GEMINI’S CEM capabilities beyond those currently available, primary research is devoted to integrating the MFDlib library developed at the University of Kentucky with GEMINI for efficient filling, factorization, and solution of large electromagnetic problems formulated using integral equation methods. A secondary research project involves the hybrid parallelization of GEMINI for the efficient speedup of the impedance matrix filling process. This thesis discusses the research, development, and testing of the secondary research project on the High Performance Computing DLX Linux supercomputer cluster. Initial testing of GEMINI’s existing MPI parallelization establishes the benchmark for speedup and reveals performance issues subsequently solved by the NASA CEM Lab. Implementation of hybrid parallelization incorporates GEMINI’s existing course level MPI parallelization with Open MP fine level parallel threading. Simple and nested Open MP threading are compared. Final testing documents the improvements realized by hybrid parallelization.

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Huthmacher, Lukas. „Investigation of efficient spin-photon interfaces for the realisation of quantum networks“. Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277150.

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Quantum networks lie at the heart of distributed quantum computing and secure quantum communication - research areas that have seen a strong increase of interest over the last decade. Their basic architecture consist of stationary nodes composed of quantum processors which are linked via photonic channels. The key requirement, and at the same time the most demanding challenge, is the efficient distribution of entanglement between distant nodes. The two ground states of single spins confined in self-assembled InGaAs quantum dots provide an effective two-level system for the implementation of quantum bits. Moreover, they offer strong transition dipole moments with outstanding photonic properties allowing for the realisation of close to ideal, high-bandwidth spin-photon interfaces. These properties are combined with the benefits of working in the solid state, such as scalability and integrability of devices, to form a promising candidate for the implementation of fast entanglement distribution. In this dissertation we provide the first implementation of a unit cell of a quantum network based on single electron spins in InGaAs. We use a probabilistic scheme based on spin-photon entanglement and the erasure of which path information to project the two distant spins into a maximally entangled Bell state. The successful generation of entanglement is verified through a reconstruction of the final two-spin state and we achieve an average fidelity of $61.6\pm2.3\%$ at a record-high generation rate of $5.8\,\mathrm{kHz}$. One of the main constraints to the achieved fidelity is the limited coherence of the electron spin. We show that it can be extended by three orders of magnitude through decoupling techniques and develop a new measurement technique, allowing us to investigate the origins of the decoherence which has previously been obscured by nuclear feedback processes. Our results evidence that further extension of coherence is ultimately limited by intrinsic mechanisms closely related to local strain due to the growth method of self-assembled quantum dots. After establishing the intrinsic limits to the electron coherence we investigate the coherence properties of the single hole spin as an alternative two-level system with the potential for higher coherence times. We show that the hole spin coherence is indeed superior to the one of the electron and realise the first successful dynamic decoupling scheme implemented in these systems. We find that the decoherence at low external magnetic fields is still governed by coupling to the nuclear spins whereas it is dominated by electrical noise for fields exceeding a few Tesla. This noise source is extrinsic to the quantum dots and a better understanding offers the potential for further improvement of the coherence time. The findings of this work present a complete study of the coherence of the charge carriers in self-assembled quantum dots and provide the knowledge needed to improve the implementation of a quantum-dot based quantum network. In particular, the combination of spin-spin entanglement and the hole coherence times enable further research towards multidimensional photonic cluster states.

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Oliverio, Lucas. „Nonlinear dynamics from a laser diode with both optical injection and optical feedback for telecommunication applications“. Electronic Thesis or Diss., CentraleSupélec, 2024. http://www.theses.fr/2024CSUP0002.

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Le traitement actuel de l'information dans les grands clusters de calcul, est responsable d'un fort impact énergétique au niveau mondial. Le paradigme actuel est à repenser, et une architecture de calcul basée sur des composants photoniques (laser à semi-conducteur notamment) est étudiée dans cette thèse. La structure envisagée est un réseau de neurones artificiels pour du traitement de données de télécommunications. Nous étudions une diode laser et ses états dynamiques lorsque soumise à une injection optique et à un feedback optiques simultanés et les liens avec sa capacité de calcul neuroinspirée par de la simulation et de l'expérimentation
The current processing of information in large computing clusters is responsible for a strong energetic impact at a global level. The current paradigm needs to be rethought, and a computing architecture based on photonic components (semiconductor laser in particular) is studied in this thesis. The considered structure is a network of artificial neurons for telecommunications data processing. This involves using a laser diode to study the relationship between the dynamics with optical injection and optical feedback and neuroinspired computing capacity with simulations and experimental work

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Sethi, Avtej Singh. „Single-Photon Generation through Unconventional Blockade in a Three-Mode Optomechanical Cavity with Kerr Nonlinearity“. Miami University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=miami1596151791078551.

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Hsiao, Tzu-Kan. „A single-photon source based on a lateral n-i-p junction driven by a surface acoustic wave“. Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283189.

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Single-photon sources are essential building blocks in quantum photonic networks, where quantum-mechanical properties of photons are utilised to achieve quantum technologies such as quantum cryptography and quantum computing. In this thesis, a single-photon source driven by a surface acoustic wave (SAW) is developed and characterised. This single-photon source is based on a SAW-driven lateral n-i-p junction in a GaAs quantum-well structure. On this device, the lateral n-i-p junction is formed by gate-induced electrons and holes in two adjacent regions. The SAW potential minima create dynamic quantum dots in a 1D channel between these two regions, and are able to transport single electrons to the region of holes along the channel. Single-photon emission can therefore be generated as these electrons consecutively recombine with holes. After characterisation and optimisation in four batches of devices, clear SAW-driven charge transport and the corresponding electroluminescence (EL) can be observed on an optimised SAW-driven n-i-p junction. Time-resolved measurements have been carried out to study the dynamics of SAW-driven electrons. Time-resolved EL signals indicate that a packet of electrons is transported to the region of holes in each SAW minimum. In addition, the carrier lifetime of SAW-driven electrons in the region of holes is shown to be $\sim 100$ ps, which is much shorter than the SAW period of $860$ ps. Hence, it is promising to observe single-photon emission in the optimised device. In order to test single-photon emission, a Hanbury Brown-Twiss experimental setup has been employed to record an autocorrelation histogram of the SAW-driven EL signal at the single-electron regime. Suppression of autocorrelation coincidences at time delay $\Delta t = 0$ is evidence of photon antibunching. By fitting theoretical functions describing the SAW-driven EL signal, it is found that the second-order correlation function shows $g^{(2)}(0) = 0.39 \pm 0.05$, which is lower than the common criterion for a single-photon source $g^{(2)}(0) < 0.5$. Moreover, theoretical calculation and simulation suggest that, if a constant background signal can be filtered out, $\sim 80 \%$ of the SAW-driven EL is single-photon emission.

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Pfeiffer, Robert. „HIGH-ORDER INTEGRAL EQUATION METHODS FOR QUASI-MAGNETOSTATIC AND CORROSION-RELATED FIELD ANALYSIS WITH MARITIME APPLICATIONS“. UKnowledge, 2018. https://uknowledge.uky.edu/ece_etds/119.

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This dissertation presents techniques for high-order simulation of electromagnetic fields, particularly for problems involving ships with ferromagnetic hulls and active corrosion-protection systems. A set of numerically constrained hexahedral basis functions for volume integral equation discretization is presented in a method-of-moments context. Test simulations demonstrate the accuracy achievable with these functions as well as the improvement brought about in system conditioning when compared to other basis sets. A general method for converting between a locally-corrected Nyström discretization of an integral equation and a method-of-moments discretization is presented next. Several problems involving conducting and magnetic-conducting materials are solved to verify the accuracy of the method and to illustrate both the reduction in number of unknowns and the effect of the numerically constrained bases on the conditioning of the converted matrix. Finally, a surface integral equation derived from Laplace’s equation is discretized using the locally-corrected Nyström method in order to calculate the electric fields created by impressed-current corrosion protection systems. An iterative technique is presented for handling nonlinear boundary conditions. In addition we examine different approaches for calculating the magnetic field radiated by the corrosion protection system. Numerical tests show the accuracy achievable by higher-order discretizations, validate the iterative technique presented. Various methods for magnetic field calculation are also applied to basic test cases.

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Vatin, Jeremy. „Photonique neuro-inspirée pour des applications télécoms“. Electronic Thesis or Diss., CentraleSupélec, 2020. http://www.theses.fr/2020CSUP0004.

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Nous produisons chaque jour de grandes quantités de données, que nous échangeons sur le réseau Internet. Ces données sont traitées grâce à des clusters de calcul, responsables de la consommation énergétique d’internet. Dans cette thèse, nous étudions une architecture faite de composants photoniques, pour se débarrasser des composants électroniques consommant de l'énergie. Grâce aux composants actuellement utilisés dans le réseau Internet (laser et fibre optique), nous réalisons un réseau neuronal artificiel capable de traiter les données de télécommunication. Le réseau de neurones artificiel est constitué d'un laser et d'une fibre optique qui renvoie la lumière dans ce laser. Le comportement complexe de ce système est utilisé pour alimenter les neurones artificiels qui sont répartis le long de la fibre. Nous sommes en mesure de prouver que ce système est capable de traiter soit un signal avec une grande efficacité, soit deux signaux au prix d'une petite perte de précision
We are producing everyday thousands of gigabits of data, exchanged over the internet network. These data are processed thanks to computation clusters, which are responsible of the large amount of energy consumed by the internet network. In this work, we study an architecture made of photonic components, to get rid of electronic components that are power consuming. Thanks to components that are currently used in the internet network (laser and optical fiber), we aim at building an artificial neural network that is able to process telecommunication data. The artificial neural network is made of a laser, and an optical fiber that send back the light into the laser. The complex behavior of this system is used to feed the artificial neurons that are distributed along the fiber. We are able to prove that this system is able either to process one signal with a high efficiency, or two signals at the expense of a small loss of accuracy

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Aspernäs, Andreas, und Mattias Nensén. „Container Hosts as Virtual Machines : A performance study“. Thesis, Linnéuniversitetet, Institutionen för datavetenskap (DV), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-57019.

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Virtualization is a technique used to abstract the operating system from the hardware. The primary gains of virtualization is increased server consolidation, leading to greater hardware utilization and infrastructure manageability. Another technology that can be used to achieve similar goals is containerization. Containerization is an operating-system level virtualization technique which allows applications to run in partial isolation on the same hardware. Containerized applications share the same Linux kernel but run in packaged containers which includes just enough binaries and libraries for the application to function. In recent years it has become more common to see hardware virtualization beneath the container host operating systems. An upcoming technology to further this development is VMware’s vSphere Integrated Containers which aims to integrate management of Linux Containers with the vSphere (a hardware virtualization platform by VMware) management interface. With these technologies as background we set out to measure the impact of hardware virtualization on Linux Container performance by running a suite of macro-benchmarks on a LAMP-application stack. We perform the macro-benchmarks on three different operating systems (CentOS, CoreOS and Photon OS) in order to see if the choice of container host affects the performance. Our results show a decrease in performance when comparing a hardware virtualized container host to a container hosts running directly on the hardware. However, the impact on containerized application performance can vary depending on the actual application, the choice of operating system and even the type of operation performed. It is therefore important to consider these three items before implementing container hosts as virtual machines.

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38

Michelberger, Patrick Steffen. „Room temperature caesium quantum memory for quantum information applications“. Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:19c9421d-0276-4c6d-a641-7640d2981da3.

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Quantum memories are key components in photonics-based quantum information processing networks. Their ability to store and retrieve information on demand makes repeat-until-success strategies scalable. Warm alkali-metal vapours are interesting candidates for the implementation of such memories, thanks to their very long storage times as well as their experimental simplicity and versatility. Operation with the Raman memory protocol enables high time-bandwidth products, which denote the number of possible storage trials within the memory lifetime. Since large time-bandwidth products enable multiple synchronisation trials of probabilistically operating quantum gates via memory-based temporal multiplexing, the Raman memory is a promising tool for such tasks. Particularly, the broad spectral bandwidth allows for direct and technologically simple interfacing with other photonic primitives, such as heralded single photon sources. Here, this kind of light-matter interface is implemented using a warm caesium vapour Raman memory. Firstly, we study the storage of polarisation-encoded quantum information, a common standard in quantum information processing. High quality polarisation preservation for bright coherent state input signals can be achieved, when operating the Raman memory in a dual-rail configuration inside a polarisation interferometer. Secondly, heralded single photons are stored in the memory. To this end, the memory is operated on-demand by feed-forward of source heralding events, which constitutes a key technological capability for applications in temporal multiplexing. Prior to storage, single photons are produced in a waveguide-based spontaneous parametric down conversion source, whose bespoke design spectrally tailors the heralded photons to the memory acceptance bandwidth. The faithful retrieval of stored single photons is found to be currently limited by noise in the memory, with a signal-to-noise ratio of approximately 0.3 in the memory output. Nevertheless, a clear influence of the quantum nature of an input photon is observed in the retrieved light by measuring the read-out signal's photon statistics via the g⁽²⁾-autocorrelation function. Here, we find a drop in g⁽²⁾ by more than three standard deviations, from g⁽²⁾ ~ 1.69 to g⁽²⁾ ~ 1.59 upon changing the input signal from coherent states to heralded single photons. Finally, the memory noise processes and their scalings with the experimental parameters are examined in detail. Four-wave-mixing noise is determined as the sole important noise source for the Raman memory. These experimental results and their theoretical description point towards practical solutions for noise-free operation.

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39

Esmail, Adam Ashiq. „Charge dynamics in superconducting double dots“. Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270018.

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The work presented in this thesis investigates transitions between quantum states in superconducting double dots (SDDs), a nanoscale device consisting of two aluminium superconducting islands coupled together by a Josephson junction, with each dot connected to a normal state lead. The energy landscape consists of a two level manifold of even charge parity Cooper pair states, and continuous bands corresponding to charge states with single quasiparticles in one or both islands. These devices are fabricated using shadow mask evaporation, and are measured at sub Kelvin temperatures using a dilution refrigerator. We use radio frequency reflectometry to measure quantum capacitance, which is dependent on the quantum state of the device. We measure the quantum capacitance as a function of gate voltage, and observe capacitance maxima corresponding to the Josephson coupling between even parity states. We also perform charge sensing and detect odd parity states. These measurements support the theoretical model of the energy landscape of the SDD. By measuring the quantum capacitance in the time domain, we observe random switching of capacitance between two levels. We determine this to be the stochastic breaking and recombination of single Cooper pairs. By carrying out spectroscopy of the bath responsible for the pair breaking we attribute it to black-body radiation in the cryogenic environment. We also drive the breaking process with a continuous microwave signal, and find that the rate is linearly proportional to incident power. This suggests that a single photon process is responsible, and demonstrates the potential of the SDD as a single photon microwave detector. We investigate this mechanism further, and design an experiment in which the breaking rate is enhanced when the SDD is in the antisymmetric state rather than the symmetric state. We also measure the quantum capacitance of a charge isolated double dot. We observe 2e periodicity, indicating the tunnelling of Cooper pairs and the lack of occupation of quasiparticle states. This work is relevant to the range of experiments investigating the effect of non-equilibrium quasiparticles on the operation of superconducting qubits and other superconducting devices.

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40

林峻緯. „Two Toolboxes for Computing Photonic Crystal Band Structures“. Thesis, 2018. http://ndltd.ncl.edu.tw/handle/88pq6k.

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碩士
國立交通大學
應用數學系數學建模與科學計算碩士班
106
A Photonic crystal is a kind of special material which has the important optic property: band gap in the band structure. In the past, by the limitation of Computer Science the scientist used computers to calculate the band structure of 1-D or 2-D Photonic crystal mainly. In recent years, due to development of technology, it has some research and numerical simulation about the 3-D Phononic crystal. However, it has a few numerical results because of large calculation and time. Based on the emergence of the Fast Algorithms for Maxwell’s Equations (FAME), the band structure of 14 crystal structures has been calculated more quickly. What we have done in this paper would be divided into three parts. Firstly, we create a set of graphical user interfaces(GUI) that can be used to make the model required for FAME calculations based on the properties of 14 crystal structures. The second work in this paper is to improve the graphical user interface version of FAME based on the FAME software package and the resulting model. Lastly, we combine the FAME package by using these data and the parallel computing of the GPU to calculate the band structure of many crystals. Finally, we relevant data and the numerical results we calculated are set up on a website for others to use.

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41

Chen, Cathy. „Photonic Interconnection Networks for Applications in Heterogeneous Utility Computing Systems“. Thesis, 2015. https://doi.org/10.7916/D82806PV.

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Growing demands in heterogeneous utility computing systems in future cloud and high performance computing systems are driving the development of processor-hardware accelerator interconnects with greater performance, flexibility, and dynamism. Recent innovations in the field of utility computing have led to an emergence in the use of heterogeneous compute elements. By leveraging the computing advantages of hardware accelerators alongside typical general purpose processors, performance efficiency can be maximized. The network linking these compute nodes is increasingly becoming the bottleneck in these architectures, limiting the hardware accelerators to be restricted to localized computing. A high-bandwidth, agile interconnect is an imperative enabler for hardware accelerator delocalization in heterogeneous utility computing. A redesign of these systems' interconnect and architecture will be essential to establishing high-bandwidth, low-latency, efficient, and dynamic heterogeneous systems that can meet the challenges of next-generation utility computing. By leveraging an optics-based approach, this dissertation presents the design and implementation of optically-connected hardware accelerators (OCHA) that exploit the distance-independent energy dissipation and bandwidth density of photonic transceivers, in combination with the flexibility, efficiency and data parallelization offered by optical networks. By replacing the electronic buses with an optical interconnection network, architectures that delocalize hardware accelerators can be created that are otherwise infeasible. With delocalized optically-connected hardware accelerator nodes accessible by processors at run time, the system can alleviate the network latency issues plague current heterogeneous systems. Accelerators that would otherwise sit idle, waiting for it's master CPU to feed it data, can instead operate at high utilization rates, leading to dramatic improvements in overall system performance. This work presents a prototype optically-connect hardware accelerator module and custom optical-network-aware, dynamic hardware accelerator allocator that communicate transparently and optically across an optical interconnection network. The hardware accelerators and processor are optimized to enable hardware acceleration across an optical network using fast packet-switching. The versatility of the optical network enables additional performance benefits including optical multicasting to exploit the data parallelism found in many accelerated data sets. The integration of hardware acceleration, heterogeneous computing, and optics constitutes a critical step for both computing and optics. The massive data parallelism, application dependent-location and function, as well as network latency, and bandwidth limitations facing networks today complement well with the strength of optical communications-based systems. Moreover, ongoing efforts focusing on development of low-cost optical components and subsystems that are suitable for computing environment may benefit from the high-volume heterogeneous computing market. This work, therefore, takes the first steps in merging the areas of hardware acceleration and optics by developing architectures, protocols, and systems to interface with the two technologies and demonstrating areas of potential benefits and areas for future work. Next-generation heterogeneous utility computing systems will indubitably benefit from the use of efficient, flexible and high-performance optically connect hardware acceleration.

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42

Wang, Howard. „Photonic Switches and Networks for High-Performance Computing and Data Centers“. Thesis, 2015. https://doi.org/10.7916/D8PC31B2.

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The accelerated growth in performance of microprocessors and the emergence of chip multiprocessors, which are now widely leveraged in current data centers and high-performance computing (HPC) systems, have motivated the need for developing novel interconnection networks solutions to meet the growing need for data transmissions across all levels of the infrastructure. This work posits that, given the unique characteristics of optics---advantages and limitations---purpose-driven systems-level designs are necessary in order to harness the tremendous performance and efficiency opportunities that can be enabled by photonic interconnects. First, an enhanced optically connected network architecture is presented featuring advanced photonic functionalities to support a wider class of bandwidth-intensive traffic patterns characteristic of cloud computing systems. This proposed architectural framework can enable a rich set of photonic resources to be allocated on-demand to optimize communications between various applications within the data center. A prototype of the proposed optical network architecture is constructed and a demonstration of two unique functionalities, serving to validate the physical layer feasibility of the system, is presented. An instantiation of this architectural framework is presented that enables physical layer data duplication in order to more effectively support reliable group data delivery in the data center. Compared to the conventional solutions that duplicate data in the network or application layer, this architecture achieves efficient data transmission over the ultra-fast, loss-free, energy-efficient and low cost optical paths, with simplified flow control, congestion control, and group membership management. Both an end-to-end hardware experiment and large-scale simulations were carried out to evaluate the efficacy of the design. Next, the challenges associated with interfacing to photonically-switched networks are explored. In particular, various interface designs aimed at addressing the unique challenges imposed by optical-packet switched networks are proposed and evaluated. First, an overview of the data vortex network optical packet switch architecture is given. A high-speed optical packet formatter and interface is then presented along with the results of end-to-end data exchanges across the interface connected to a data vortex network. Finally, the design of a low-power all-optical interface alternative is validated with an end-to-end demonstration. Finally, various unique photonic switching node designs are introduced for a variety of applications|a nanosecond-scale bidirectional 2 x —2 switch to construct efficient optical fat-tree architectures, a 4 x —4 switch capable of operating as both a nanosecond-scale optical packet switch and as an optical circuit switch, and a non-blocking 4 x —4 switch designed for constructing on-chip photonic integrated networks.

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43

Ma, Xun Jr. „Strong-Coupling Quantum Dynamics in a Structured Photonic Band Gap: Enabling On-chip All-optical Computing“. Thesis, 2012. http://hdl.handle.net/1807/34791.

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In this thesis, we demonstrate a new type of resonant, nonlinear, light-matter interaction facilitated by the unique electromagnetic vacuum density-of-state (DOS) structure of Photonic Band Gap (PBG) materials. Strong light localization inside PBG waveguides allows extremely strong coupling between laser fields and embedded two-level quantum dots (QD). The resulting Mollow splitting is large enough to traverse the precipitous DOS jump created by a waveguide mode cutoff. This allows the QD Bloch vector to sense the non-smoothness of the vacuum structure and evolve in novel ways that are forbidden in free space. These unusual strong-coupling effects are described using a "vacuum structure term" of the Bloch equation, combined with field-dependent relaxation rates experienced by the QD Bloch vector. This leads to alternation between coherent evolution and enhanced relaxation. As a result, dynamic high-contrast switching of QD populations can be realized with a single beam of picosecond pulses. During enhanced relaxation to a slightly inverted steady state at the pulse peak, the Bloch vector rapidly switches from anti-parallel to parallel alignment with the pulse torque vector. This then leads to a highly inverted state through subsequent coherent "adiabatic following" near the pulse tail, providing a robust mechanism for picosecond, femto-Joule all-optical switching. The simultaneous input of a second, weaker (signal) driving beam at a different frequency on top of the stronger (holding) beam enables rich modulation effects and unprecedented coherent control over the QD population. This occurs through resonant coupling of the signal pulse with the Mollow sideband transitions created by the holding pulse, leading to either augmentation or negation of the final QD population achieved by the holding pulse alone. This effect is applied to ultrafast all-optical logic AND, OR and NOT gates in the presence of significant (0.1 THz) nonradiative dephasing and (about 1%) inhomogeneous broadening. Further numerical studies of pulse evolutions inside the proposed devices demonstrate satisfactory population contrast within a PBG waveguide length of about 10 micro meter. These results provide the building blocks for low-power, ultrafast, multi-wavelength channel, on-chip, all-optical computing.

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44

Bassa, Humairah. „Implementing Grover's search algorithm using the one-way quantum computing model and photonic orbital angular momentum“. Thesis, 2011. http://hdl.handle.net/10413/9704.

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Standard quantum computation proceeds via the unitary evolution of physical qubits (two-level systems) that carry the information. A remarkably different model is one-way quantum computing where a quantum algorithm is implemented by a set of irreversible measurements on a large array of entangled qubits,, known as the cluster state. The order and sequence of these measurements allow for different algorithms to be implemented. With a large enough cluster state and a method in which to perform single-qubit measurements the desired computation can be realised. We propose a potential implementation of one-way quantum computing using qubits encoded in the orbital angular momentum degree of freedom of single photons. Photons are good carriers of quantum information because of their weak interaction with the environment and the orbital angular momentum of single photons offers access to an infinite-dimensional Hilbert space for encoding information. Spontaneous parametric down-conversion is combined with a series of optical elements to generate a four-photon orbital angular momentum entangled cluster state and single-qubit measurements are carried out by means of digital holography. The proposed set-up, which is based on an experiment that utilised polarised photons, can be used to realise Grover’s search algorithm which performs a search through an unstructured database of four elements. Our application is restricted to a two-dimensional subspace of a multi-dimensional system, but this research facilitates the use of orbital angular momentum qubits for quantum information processing and points towards the usage of photonic qudits (multi-level systems). We also review the application of Dirac notation to paraxial light beams on a classical and quantum level. This formalism is generally employed in quantum mechanics but the analogy with paraxial optics allows us to represent the classical states of light by means of Dirac kets. An analysis of the analogy between the classical and quantum states of light using this formalism, is presented.
Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2011.

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45

Pistol, Constantin. „Structures, Circuits and Architectures for Molecular Scale Integrated Sensing and Computing“. Diss., 2009. http://hdl.handle.net/10161/1177.

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Nanoscale devices offer the technological advances to enable a new era in computing. Device sizes at the molecular-scale have the potential to expand the domain of conventional computer systems to reach into environments and application domains that are otherwise impractical, such as single-cell sensing or micro-environmental monitoring.

New potential application domains, like biological scale computing, require processing elements that can function inside nanoscale volumes (e.g. single biological cells) and are thus subject to extreme size and resource constraints. In this thesis we address these critical new domain challenges through a synergistic approach that matches manufacturing techniques, circuit technology, and architectural design with application requirements. We explore and vertically integrate these three fronts: a) assembly methods that can cost-effectively provide nanometer feature sizes, b) device technologies for molecular-scale computing and sensing, and c) architectural design techniques for nanoscale processors, with the goal of mapping a potential path toward achieving molecular-scale computing.

We make four primary contributions in this thesis. First, we develop and experimentally demonstrate a scalable, cost-effective DNA self-assembly-based fabrication technique for molecular circuits. Second, we propose and evaluate Resonance Energy Transfer (RET) logic, a novel nanoscale technology for computing based on single-molecule optical devices. Third, we design and experimentally demonstrate selective sensing of several biomolecules using RET-logic elements. Fourth, we explore the architectural implications of integrating computation and molecular sensors to form nanoscale sensor processors (nSP), nanoscale-sized systems that can sense, process, store and communicate molecular information. Through the use of self-assembly manufacturing, RET molecular logic, and novel architectural techniques, the smallest nSP design is about the size of the largest known virus.

Dissertation

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46

Penney, Jonathan. „A Photon Mapping Based Approach to Computing Celestial Illumination“. 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-470.

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For photographers to capture good pictures of their subjects, the lighting conditions must be taken into account and adjusted for accordingly. The same holds true for a satellite attempting to photograph another object in space: it must know the lighting conditions to adjust camera settings and position itself properly to take the best photograph. This thesis presents a photon mapping based algorithm to compute a physically accurate representation of the illumination of objects in orbit around the Earth, taking into account the effects that cause refraction in the atmosphere. I also discuss the assumptions that I have made to utilize the algorithm in an interactive 3D visualization tool, which I implemented to view the illumination on objects at arbitrary positions in space. Finally, I show that the photon mapping method offers improvements over simpler methods of computing illumination.

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47

Gnanavignesh, R. „Parallel Computing Techniques for High Speed Power System Solutions“. Thesis, 2020. https://etd.iisc.ac.in/handle/2005/4981.

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Modern power systems are enormously large and complex entities. Planning, maintaining and operating such a system would be cumbersome if it were not for the wide assortment of analytical methods available to assist the power engineer. With the advent of interconnected systems came the necessity of developing techniques for enabling the power system operator to determine the electrical state of the network and to predict how it would respond to different disturbances such that reliability and other economic criteria are always met. Increase in system size, introduction of complex controls, uncertainties in forecasting, etc. necessitate faster software tools to handle power system planning, operation and operator training. This thesis aims to improve the performance of power system software tools by proposing parallel algorithms with the objective of reducing their execution time. Solution of a sparse set of linear algebraic equations is one of the most essential modules used in almost all power system software tools. The thesis addresses the issue of reducing the execution time of sparse linear algebraic solver by parallelizing sparse matrix factorization. A LU factorization algorithm which is more amenable for parallelization is identified and chosen. In this work, the structural symmetry property of power system sparse matrices is exploited to maximize the column or node level parallelism. Results obtained from the implementation of the proposed algorithm on Graphical Processing Units (GPUs) corroborate its efficacy by achieving significant reduction in the solution time when compared with state of the art CPU based sequential sparse linear solvers. Power flow algorithm is one of the most frequently executed algorithms with respect to the steady state realm of the power system. The output of the power flow algorithm is the phasor bus voltages and line flows for the given load-generation pattern. Reduction in the solution time for the power flow algorithm would further boost other applications like contingency analysis, optimal power flow, dynamic studies, etc. This thesis proposes a parallel power flow algorithm based on Newton-Raphson method. Inclusion of reactive power limit constraints at generator buses in the problem formulation stage itself eradicates the need to use heuristic techniques. In this work, the given power system network for which the power flow solution is desired, is decomposed into smaller sub-networks and processed in an independent as well as in a concurrent manner. Partial results from the sub-networks are consolidated to arrive at the solution of original network. The proposed algorithm is implemented on a computer architecture comprising of multiple cores. Results obtained indicate preservation of the superior convergence property of Newton-Raphson method and a significant reduction in the solution time required for the parallel version of the power flow when compared with the sequential version. Transient stability assessment is an important module within the Dynamic Security Assessment application. The objective of transient stability assessment is to obtain the dynamic, low frequency electromechanical phenomenon and determine whether the power system would be able to maintain synchronism after an electrical disturbance. Time domain simulation for the stability assessment by solving thousands of Differential Algebraic Equations (DAEs), even though is the preferred method, is computationally intensive and becomes a major computing challenge as system size increases. The thesis proposes a parallel algorithm based on spatial domain decomposition employing relaxation conditions to speedup the transient stability simulation to handle the aforementioned challenge. A convergence enhancing mechanism through selection of appropriate admittance parameters for the network emulating fictitious buses which mimic the remainder of the system for each sub-network is derived. Also, a technique of port dependency reduction, which guarantees convergence for any general network is presented. Results obtained from implementation on a multicore parallel architecture corroborate the scalability and improved speedup features of the methodology which achieves a significant reduction in the simulation execution time which would greatly aid in reliably operating the power system.

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48

Titchener, James. „On-chip generation and characterization of quantum light“. Phd thesis, 2017. http://hdl.handle.net/1885/133189.

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Technologies based on quantum mechanics promise to revolutionize the collection, processing and communication of information. However, due to the fragility of quantum coherence, complex quantum states can only exist in highly isolated and stable environments. One suitable environment is that of a quantum photonic chip. Quantum integrated photonics seeks to generate, process and detect complex quantum states inside a photonic chip. This thesis presents theory and experimental verification of novel approaches for the integration of various functionalities into quantum photonic chips in a scalable way. As such, this thesis encompasses a broad area of physics including quantum optics and nonlinear photonics. The results presented in this thesis have applications in the areas of quantum enhanced measurement, communication and information processing. In particular we develop the theory and experimentally demonstrate flexible on-chip sources of spatially entangled photons, the state of which can be reconfigured alloptically. We show how such techniques could enable the realization of simple cluster state quantum computing algorithms using spatially encoded two-photon states. Furthermore, we suggest new and practical approaches for the efficient characterization of mass produced nonlinear quantum photonic chips. Finally we develop and experimentally demonstrate a scalable method for the full quantum state tomography of multi-photon states on-chip. Importantly this technique only requires a linearly increasing number of single photon detectors relative to the number of photons in the state being characterized, and is also highly compatible with on-chip single photon detectors.

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49

„Entanglement of photons and atoms in leaky cavities and its application to quantum computing“. Thesis, 2008. http://library.cuhk.edu.hk/record=b6074534.

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Adopting the continuous frequency mode approach and the resolvent method, we study the interaction between atoms and photons in leaky optical cavities. In particular, we highlight the physical significance of quantum states of photons in such processes. Single-photon processes and two-photon processes are intensively investigated. With single-photon scattering, various schemes for generating entangled pairs and constructing quantum gates are developed using two-level atoms or Λ-type atoms. The fidelities of these schemes tend to unity for injected photons with specific spectra. We examine the efficiency of the feedback scheme proposed by Hong and Lee [Phys. Rev. Lett. 89 , 237901 (2002)] to generate maximally entangled states of two atoms in an optical cavity from first principles. We find that the efficiency of the scheme deteriorates gradually and hence other competing processes have to be considered properly. Besides, nonlinearity and entanglement of two-photon states in two-sided and one-sided cavities are analyzed in terms of detection probabilities and frequency-correlation of the left- and right-output photons. We discover that two-photon processes in a one-sided cavity can be exploited to generate two-photon maximally entangled states, from which nonlocal shaping effect in the spectra of the two photons can be demonstrated. Lastly, based on the Fredholm method, an iterative analytical method yielding the Schmidt modes and eigenvalues of an entangled state is proposed and discussed.
Fung, Ho Tak = 光子與原子在漏空腔中的糾纏及其在量子計算中的應用 / 馮浩德.
"May 2008."
Adviser: P. T. Leung.
Source: Dissertation Abstracts International, Volume: 70-03, Section: B, page: 1736.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2008.
Includes bibliographical references (p. 155-163).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
Fung, Ho Tak = Guang zi yu yuan zi zai lou kong qiang zhong de jiu chan ji qi zai liang zi ji suan zhong de ying yong / Feng Haode.

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50

Biggerstaff, Devon. „Experiments with Generalized Quantum Measurements and Entangled Photon Pairs“. Thesis, 2009. http://hdl.handle.net/10012/4841.

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This thesis describes a linear-optical device for performing generalized quantum measurements on quantum bits (qubits) encoded in photon polarization, the implementation of said device, and its use in two diff erent but related experiments. The device works by coupling the polarization degree of freedom of a single photon to a `mode' or `path' degree of freedom, and performing a projective measurement in this enlarged state space in order to implement a tunable four-outcome positive operator-valued measure (POVM) on the initial quantum bit. In both experiments, this POVM is performed on one photon from a two-photon entangled state created through spontaneous parametric down-conversion. In the fi rst experiment, this entangled state is viewed as a two-qubit photonic cluster state, and the POVM as a means of increasing the computational power of a given resource state in the cluster-state model of quantum computing. This model traditionally achieves deterministic outputs to quantum computations via successive projective measurements, along with classical feedforward to choose measurement bases, on qubits in a highly entangled resource called a cluster state; we show that `virtual qubits' can be appended to a given cluster by replacing some projective measurements with POVMs. Our experimental demonstration fully realizes an arbitrary three-qubit cluster computation by implementing the POVM, as well as fast active feed-forward, on our two-qubit photonic cluster state. Over 206 diff erent computations, the average output delity is 0.9832 +/- 0.0002; furthermore the error contribution from our POVM device and feedforward is only of order 10^-3, less than some recent thresholds for fault-tolerant cluster computing. In the second experiment, the POVM device is used to implement a deterministic protocol for remote state preparation (RSP) of arbitrary photon polarization qubits. RSP is the act of preparing a quantum state at a remote location without actually transmitting the state itself. We are able to remotely prepare 178 diff erent pure and mixed qubit states with an average delity of 0.995. Furthermore, we study the the fidelity achievable by RSP protocols permitting only classical communication, without shared entanglement, and compare the resulting benchmarks for average fidelity against our experimental results. Our experimentally-achieved average fi delities surpass the classical thresholds whenever classical communication alone does not trivially allow for perfect RSP.

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