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.

The Standard Model has granted exquisite power to predict the behaviour of high-energy particle collisions. It is not, however, without conceptual and empirical weaknesses. Several theories have been proposed which aim to resolve these difficulties. This thesis describes searches for two such theories: models of extra spatial dimensions, and supersymmetry. The Large Hadron Collider has extended the frontiers of energy and intensity in particle physics. In 2015, the LHC resumed proton–proton collisions at a centre-of-mass energy of 13 TeV. This increase over previous operation grants an enhancement in sensitivity to many processes beyond those of the Standard Model. Extra-dimensional theories address the hierarchical nature of the Standard Model. The lowered fundamental scale of gravity in these models allows a rich phenomenology at energies which may be accessible to the LHC. Some models predict the formation of microscopic black holes, which are the target of an analysis of collisions recorded by the ATLAS detector in 2015. No significant deviations from Standard Model predictions were observed. The constraints inferred on the parameters of the model are a significant advance on previous results. Lepton flavour is conserved in the Standard Model. This is not the result of a known fundamental symmetry, however. The latter part of this thesis proposes a search examining asymmetries of charge and flavour in the eμ final state. Models of supersymmetry with an R-parity-violating λ'₂₃₁ coupling are taken as motivation. The strategy is developed using collision data recorded by ATLAS in 2015 and 2016, and the most significant biasing effects are addressed.

In this thesis we study the time evolution of Rényi and entanglement entropies of thermal states in Conformal Field Theory (CFT). These quantities are usually hard to compute but Ryu-Takayanagi (RT) and Hubeny-Rangamani-Takayanagi (HRT) proposals allow us to find the same quantities using calculations in general relativity. We will introduce main concepts of holography, quantum information and conformal field theory that will be used to derive the results of this thesis. In the first part of the thesis, we explicitly compute entanglement entropy of the rotating BTZ black hole by directly applying HRT proposal and finding lengths of spacelike geodesics. Rényi entropy of thermal state perturbed by a local quantum quench is computed by mapping correlators on two glued cylinders to the plane for field theory containing a single free boson and for 2d CFTs in the large c limit. We consider Thermofield Double State (TFD) which is an entangled state in direct product of two 2D CFTs. It is conjectured to be holographically equivalent to the eternal BTZ black hole. TFD state is perturbed by a local quench in one CFT and mutual information between two intervals in two CFTs is computed. We find when mutual information vanishes and interpret this as scrambling time, i.e. time scale required for the system to thermalize. This field theory result is modelled with a massive free falling particle in the BTZ black hole. We have computed the back-reaction of the particle on the metric of BTZ and used RT proposal to find holographic entanglement entropy. Finally, we generalize this calculation to the case of rotating BTZ with inner and outer horizons. It is dual to the CFT with different temperatures for left and right moving modes. We calculate mutual information and scrambling time and find exact agreement between results in the gravity and those in the CFT.

Political, environmental and marketing factors mean there is a global requirement to produce vehicles with improved fuel economy and reduced emissions. This thesis shows that the gasoline direct injection (GDI) engine will continue to form a significant portion of the automotive propulsion market in the short to medium term. However, to reach future targets continuous development and optimisation of these engines is essential. The introduction to this thesis discusses the role some of the key aspects of GDI engine design have on overall engine efficiency. The fuel spray is shown to be a key contributor to this, as it is a primary driver in the fuel/air mixing process, and therefore intrinsically linked to the combustion efficiency.

Nesta dissertação estão apresentados os principais conceitos teóricos envolvidos na ação dos jatos formados em dissipadores tipo salto esqui sobre fossa de erosão pré-escavada, desde o trajeto do jato em sua fase aérea e em sua fase submersa, dando especial ênfase às pressões hidrodinâmicas e sua caraterização junto ao fundo da bacia. Para estudar experimentalmente a ação dos jatos nas bacias de dissipação, utilizou-se de um modelo físico de escala 1:100 construído no Laboratório de Obras Hidráulicas do IPH/UFRGS com ensaios de diferentes vazões e diferentes profundidades de fossas pré-escavadas. Os dados foram extraídos dos ensaios no modelo físico através de vasta instrumentação, utilizando-se comportas, pontas linimétricas, piezômetros, sensores de pressão, imagens e outros equipamentos. Foi realizada uma análise criteriosa dos dados gerados no modelo físico a partir das imagens do jato na sua trajetória aérea e no escoamento do jato em sua fase submersa, comparando os dados do modelo aos resultados obtidos por métodos tradicionais de cálculo. Também foram analisados os dados de pressão gerados durante os ensaios, sendo apresentados os resultados relativos às pressões médias e às pressões dinâmicas. As pressões dinâmicas observadas no modelo físico foram comparadas com as calculadas por meio de metodologia teórica abordada na bibliografia com a finalidade de avaliar a qualidade dessa metodologia para aplicação em projetos de engenharia, onde se observou grandes diferenças de magnitude da pressão quando em colchões rasos, e diferenças de distribuição de pressão ao longo do fundo da bacia de dissipação, principalmente quando em colchões profundos. No sentido de ajustar a metodologia aplicada, foi proposta a variação de parâmetros que regulam a forma do bulbo de pressões e a aplicação de um coeficiente de amortecimento de pressões, sendo que assim foi possível melhorar significativamente a distribuição e a magnitude das pressões calculadas devido à ação dos jatos no fundo da bacia de dissipação. Os resultados se mostram satisfatórios até determinada distância após o pico de pressão provocado pelo jato, sendo que após este ponto os efeitos de ressalto hidráulico prevalecem e devem ser pesquisados em estudos futuros. / In this dissertation are presented the main theorical concepts involved in the action of the jets formed in ski jump spillways on stilling basins type pre-excavated scour hole, from the path of the jet in its air stage and in his submerged phase, with particular emphasis on hydrodynamic pressures and its characterization by the bottom of the basin. To experimentally study the action of the jets in stilling basins, was used a physical model in scale 1:100 built in Hydraulic Works Laboratory of IPH/UFRGS with experiments of different flow rates and different depths of pre-excavated scour hole. The data were extracted from experiments on the physical model through extensive instrumentation, using gates, piezometers, pressure sensors, images and other equipment. A careful analysis of the data generated in the physical model from the jet images in your path through the air was performed and the flow of the jet in its submerged phase, comparing the model data to the results obtained by traditional methods of calculation. The pressure data generated during the tests and presented the results for the mean pressures and dynamic pressures were also analyzed. Dynamic pressures observed in the physical model were compared with those calculated by means of theoretical methods for the purpose of evaluating the quality of this methodology for use in engineering projects, where we observed large differences in magnitude of pressure when in shallow water beds, and diferences in pressure distribution over the stilling basin bottom, especially when in deep water beds. In order to adjust the applied methodology, it was proposed to change parameters governing the shape of the pressure bulb and the application of a pressure damping coefficient, and thus was possible to significantly improved the distribution and magnitude of the calculated pressures due to action of the jets in the stilling basin bottom. The results have been satisfactory up to a certain distance after the peak pressure caused by the jet, and after this point the hydraulic jump effects prevail and should be investigated in future studies.

Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-11-06T20:40:37Z No. of bitstreams: 1 GABRIELA COUTINHO LUNA – DISSERTAÇÃO (PPGFísica) 2016.pdf: 715387 bytes, checksum: 874a57d0f89fb17ac576dd091e90bb48 (MD5) / Made available in DSpace on 2018-11-06T20:40:37Z (GMT). No. of bitstreams: 1 GABRIELA COUTINHO LUNA – DISSERTAÇÃO (PPGFísica) 2016.pdf: 715387 bytes, checksum: 874a57d0f89fb17ac576dd091e90bb48 (MD5) Previous issue date: 2016-02 / O estudo do buraco negro acústico, ou análogo acústico, se assemelha ao gravitacional da seguinte forma: verifi ca-se o fenômeno da radiação Hawking, apresença de um horizonte de eventos, a possibilidade de se calcular a sua temperatura, também chamada de temperatura Hawking, e obtêm-se uma métrica que descreve a geometria do buraco negro. Inserimos na métrica acústica a teoria não-comutativa, a fim de vericar as correções que resultam desta teoria. Neste trabalho, consideramos o princípio da incerteza generalizado, no formalismo de tunelamento via método de Hamilton-Jacobi, para determinar a temperatura Hawking e a entropia quântica corrigida para buracos negros acústicos não comutativo sem 2+1 dimensões. Em nossos resultados obtemos uma entropia de área, comum termo de correção logarítmica em ordem dominante um termo, em ordem menor, proporcional à temperatura de radiação associada com os buracos negros acústicos comutativos e um termo extra que depende de uma carga conservada. Assim, como no caso gravitacional, não há necessidade de apresentar o corte ultravioleta e as divergências são eliminadas. / Acoustic black hole study resembles the gravitational black hole as follows: we verify Hawking radiation phenomenon the presence of an event horizon, the possibility to calculate its temperature, also known as Hawking temperature, and we obtain a metric that describes the black hole geometry. We insert in the acoustic metric theory the non commutative theory in order to verify the corrections that result from this theory. In this study, we consider the generalized uncertainty principle in tunneling formalism by Hamilton-Jacobi method to determine Hawking temperature and quantum entropy corrected for non commutative acoustic black holes in 2+1 dimensions. In our results, we obtain an entropy are a with a termoflogarith mic correction in ruling order a termina smaller order, proportional to the radiation temperature associated with the commutative acoustic black holes and an extra term that depends on a conserved charge. Thus as in the gravitational case, there is noneed to present the ultraviolet cut-off and differences are eliminated.

Esta dissertação investiga soluções para o problema genérico de geração de vistas sintéticas a partir de um conjunto de imagens utilizando a abordagem Depth-Image-Based Rendering. Essa abordagem utiliza um formato compacto para a representação de imagens 3D, composto basicamente por duas imagens, uma colorida para a vista de referência e outra em tons de cinza com a correspondência de disparidade para cada pixel. Soluções para esse problema beneficiam aplicações como Free Viewpoint Television. O maior desafio é o preenchimento de regiões sem informação de projeção considerando o novo ponto de vista, genericamente denominados holes, além de outros artefatos como cracks e ghosts que ocorrem por oclusões e erros no mapa de disparidade. Nesta dissertação apresentamos técnicas para remoção e tratamento de cada uma das classes de potenciais artefatos. O conjunto de métodos propostos apresenta melhores resultados quando comparado com o atual estado da arte em geração de vistas sintéticas com o modelo DIBR para o conjunto de dados Middlebury, considerando-se as métricas SSIM e PSNR. / This dissertation investigates solutions to the general problem of generating synthetic views from a set of images using the Depth-Image-Based Rendering approach. This approach uses a compact format for the 3D image representation, composed basically of two images, one color image for the reference view and other grayscale image with the disparity information available for each pixel. Solutions to this problem benefit applications such as Free Viewpoint Television. The biggest challenge is filling in regions without projection information considering the new viewpoint, usually called holes, and other artifacts such as cracks and ghosts that occur due to occlusions and errors in the disparity map. In this dissertation we present techniques for removal and treatment of each of these classes of potential artifacts. The set of proposed methods shows improved results when compared to the current state of the art generation of synthetic views using the DIBR model applied to the Middlebury dataset, considering the SSIM and PSNR metrics.

Os Aços Avançados de Alta Resistência ou AHSS (do inglês Advanced High Strength Steels) apresentam muitas vantagens mecânicas em relação aos aços convencionais. Seu uso crescente na indústria automotiva deve-se principalmente à sua capacidade de possibilitar a redução de peso e, ao mesmo tempo, o aumento da segurança aos ocupantes do veículo em caso de colisões. No entanto, apresentam maiores dificuldades no que se refere à conformabilidade (maiores níveis de solicitação e desgaste das ferramentas, menor deformabilidade plástica, etc). Assim, alguns testes para avaliar a conformabilidade destes materiais ganham maior importância. É o caso do Teste de Expansão de Furos, cuja propriedade medida é a Razão de Expansão de Furos (REF). Neste trabalho investiga-se o processo de expansão de furos para o aço avançado de alta resistência (AHSS) martensítico DOCOL 190M, sob as seguintes condições de processo: duas formas de obtenção do furo (jato d’água e usinagem); duas geometrias distintas de punções (cônico de 60º e elíptico); diversos diâmetros do furo inicial; com e sem o uso de lubrificante; com acabamento diferenciado da borda do furo; e expansão com deslocamento do punção em etapas. Os experimentos demonstram que a expansão de furos possui uma estreita relação com a geometria do punção utilizado para a expansão, bem como com o diâmetro do furo inicial, acabamento da borda e condições de lubrificação. A partir dos resultados experimentais de expansão de furos foi possível realizar a calibração de um software de simulação computacional em relação ao dano crítico do material no momento da fatura na borda do furo. / Advanced High Strength Steels (AHSS) offer many mechanical advantages over conventional steels. Its increasing use in the automotive industry is mainly due to its ability to reduce weight and, at the same time, increase occupant safety in the event of collisions. However, they present greater difficulties with respect to the formability (higher levels of solicitation and wear of the tools, lower plastic formability, etc). Thus, some tests to evaluate the formability of these materials come to have greater importance. This is the case of the Hole Expansion Test, whose measured property is the Hole Expansion Ratio (REF). This work investigates the hole expansion process for a martensitic advanced high-strength steel (AHSS), DOCOL 190M, under the following process conditions: two ways of obtaining the hole (water jet and machining); two different geometries of punctures (conical of 60º and elliptical); various diameters of the initial hole; with and without the use of lubricant; with differentiated finishing of the hole edge; and expansion with punch displacement in steps. The experiments demonstrate that the hole expansion has a close relationship with the geometry of the punch used for the expansion, as well as the initial hole diameter, edge finish and lubrication conditions. From the experimental hole expansion results it was possible to carry out the calibration of a computational simulation software in relation to the critical damage of the material at the moment of hole edge rupture.

En raison des enjeux économiques et écologiques majeurs auxquels doivent faire face les acteurs de l’industrie aéronautique depuis plusieurs décennies, la part massique de composite dans la composition des avions n’a cessé d’augmenter : elle était d’environ 5% en 1972 pour l’Airbus A300 pour arriver à plus de 50% en 2013 pour l’Airbus A350. En effet, l’objectif étant de réduire toujours plus la masse des avions, les alliages d’aluminium qui les composaient en grande majorité (75% de la masse dans les années 70) ont été progressivement remplacés par d’autres matériaux aux caractéristiques mécaniques spécifiques jugées plus intéressantes et notamment par le CFRP (Carbon Fiber Reinforced Plastic) que l’on couple souvent aux alliages de titane parce qu’ils font preuve d’une meilleure compatibilité thermique et électrochimique que le couple CFRP/alliage d’aluminium.En conséquence, de nombreux cas d’assemblage sont aujourd’hui des empilages hybrides CFRP/Ti6Al4V pour lesquels l’objectif est de pouvoir réaliser le perçage en une seule opération comme c’était le cas auparavant avec les assemblages métal/métal. Les études réalisées sur le perçage de ces empilages hybrides ont montré que les températures de coupe élevées de l’opération, majoritairement dues à l’usinage de la partie constituée de Ti6Al4V, étaient une cause majeure du non-respect des spécifications aéronautiques. C’est à partir de ces constatations que l’idée d’utiliser l’assistance cryogénique est née : refroidir la zone de coupe en injectant de l’azote liquide par le centre broche, en lieu et place des moyens de lubrification et de refroidissement plus classiques.En effet, la chaleur latente que l’azote liquide absorbe lors de sa vaporisation en fait un excellent candidat pour refroidir efficacement la zone de coupe. Son utilisation est de plus une solution totalement écologique puisqu’elle permet d’éviter l’utilisation de fluides de coupe et permet ainsi d’éviter les opérations de lavage des pièces, d’essorage des copeaux et de recyclage des fluides tout en restant neutre pour l’opérateur et la planète.Ainsi, ce projet de thèse s’articule autour de l’étude des effets de l’assistance cryogénique sur le perçage du Ti6Al4V et s’intéresse en particulier à son impact sur le phénomène de resserrement du trou. En effet, les chargements thermomécaniques induits par l’opération ainsi que les formes et dimensions finales des trous réalisés sont en réalité fortement liés à ce phénomène qui n’avait jusqu’ici été que très peu étudié. Par conséquent, cette thèse propose d’une part de mettre en évidence l’importance du resserrement du trou en perçage de Ti6Al4V et d’autre part de fournir des éléments d’analyse et de compréhension sur ce phénomène dans les conditions d’usinage à sec et avec assistance cryogénique. / On account of the major economic and ecological stakes to which the aeronautic industry stakeholders had to react during the last decades, the composite mass percentage in aircrafts never stopped to increase and reached more than 50% in 2013 for the Airbus A350. Indeed, the aim always being to build lighter aircrafts, aluminum alloys (which represented more than 75% of the total mass in the 70’) were gradually replaced by other materials which were considered to have more advantageous mechanical properties to weight ratios and especially by CFRP (Carbon Fiber Reinforced Plastic). Since the CFRP/titanium alloy pair demonstrates a better thermal and electrochemical compatibility compared to the CFRP/aluminum alloy pair, the use of titanium alloys in aircraft increased as well.Therefore, many assembly cases are currently CFRP/Ti6Al4V hybrid stacks for which the goal is to be able to drill them in one shot, just as it was done for metal/metal stacks. Studies were carried out concerning hybrid stacks drilling and highlighted that the elevated temperatures during the Ti6Al4V drilling were mainly responsible for the non-fulfilment of aeronautical specifications. Based on these observations, the idea of using the cryogenic assistance emerged: cooling down the cutting area by using liquid nitrogen instead of classic modes of lubrication and cooling.Indeed, the latent heat that liquid nitrogen absorbs when it vaporizes makes it an excellent candidate to efficiently cool the cutting zone. Moreover, since it evaporates quickly at room temperature, it eliminates the need to clean the parts and to recycle the fluids while being neutral for the planet and the machine operator.This Ph.D thesis revolves around the study of cryogenic assistance effects in Ti6Al4V drilling and focuses especially on its impact on hole shrinkage. Indeed, the shape and dimensions of the drilled hole, as well as the thermomechanical loads induced by the operation depend on this little-known phenomenon. Therefore, this thesis proposes to highlight the key role of hole shrinkage in Ti6Al4V drilling and to give elements of analysis and understanding on the phenomenon, for dry and cryogenic cutting conditions.

Submitted by Leonardo Cavalcante (leo.ocavalcante@gmail.com) on 2018-04-30T12:02:07Z No. of bitstreams: 1 Arquivototal.pdf: 24368358 bytes, checksum: fd9b0467308dbf6dbef945eb954aa2e3 (MD5) / Made available in DSpace on 2018-04-30T12:02:07Z (GMT). No. of bitstreams: 1 Arquivototal.pdf: 24368358 bytes, checksum: fd9b0467308dbf6dbef945eb954aa2e3 (MD5) Previous issue date: 2017-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Abstract indisponível - entregue como imagem / Resumo indisponível - entregue como imagem