Orientador: Antonio Vidiella Barranco / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T14:52:42Z (GMT). No. of bitstreams: 1 Lourenco_FelipedeCampos_M.pdf: 1075719 bytes, checksum: 3053a24a405a3d715e3f7faf6455b424 (MD5) Previous issue date: 2008 / Resumo: O principal propósito dessa dissertação é estudar um novo modelo de interação entre um átomo e um modo do campo eletromagnético quantizado, assim como a sua aplicação no problema de transferência de emaranhamento entre qubits e sistemas de variáveis contínuas. Inicialmente, apresentamos uma revisão do principal modelo de interação átomo campo quantizado, conhecido como modelo de Jaynes Cummings, e também uma introdução ao emaranhamento, com o objetivo de estabelecer as medidas que serão utilizadas no restante do trabalho. Após essa parte introdutória, baseados no já conhecido modelo Raman degenerado, propomos o modelo Raman Quase degenerado com intuito de descrever a interação de um átomo de três níveis na configuração L e um modo do campo quantizado. Admitimos que o campo, no limite dispersivo, acopla os dois níveis atômicos inferiores ao estado de maior energia e este é eliminado por uma transformação unitária, ou por eliminação adiabática. Dessa forma, ele passa a desempenhar o papel de um nível virtual que possibilita a transição efetiva entre os dois estados de menor energia do átomo. Para chegarmos à forma final do Hamiltoniano efetivo, ainda supomos que a diferença de energia entre os dois níveis inferiores é muito pequena se comparada à dessintonia do nível excitado em relação à freqüência do campo interagente. A partir das equações que descrevem a dinâmica do átomo interagindo com um campo coerente, investigamos a transferência de emaranhamento de um par de átomos maximamente emaranhados para um par de cavidades preparadas inicialmente no estado puro e separável de campo coerente. Naturalmente, também consideramos a transferência no sentido contrário, campo átomo. Os resultados obtidos mostram que é possível a transferência completa nas duas situações. O último assunto abordado nessa dissertação foram os estados coerentes emaranhados do tipo cluster. Propomos um esquema para a geração desse tipo de estado entre quatro cavidades separadas espacialmente utilizando apenas um átomo e duas zonas de Ramsey e também estudamos a influência da dissipação de energia / Abstract: The main purpose of this dissertation is to study a new model to describe the interaction between an atom and a mode of the quantized electromagnetic field and also its application to the entanglement reciprocation problem between qubits and continuous variable systems. Firstly, we review the main model used to describe the atom field interaction,known as the Jaynes Cummings model, and also make an introduction to entanglement, aiming to establish the measures that will be used latter.After this introductory part and based on the known degenerate Raman model, we propose the Quasi degenerate Raman model with the intention to describe the interaction between a three level atom in the L configuration and a mode of the quantized field. We admit that the field, in the dispersive limit, couples the two lower atomic levels to the highest energy state, which is then eliminated by a unitary transformation, or by an adiabatic elimination.In this way, it plays the role of a virtual level which enables the effective transition between the other two lower energy levels. To get to the final form of the effective Hamiltonian we still assume that the energy difference between these two lower energy levels is too small when compared to the detuning of the excited level. From the equations that describe the dynamics of an atom interacting with a coherent field, we investigate the entanglement transfer from two maximally entangled atoms to two cavities initially prepared in a pure separable coherent state. Naturally, we also consider the transfer on the opposite way, field -- atom. Our results show that the complete entanglement reciprocation is possible. The last subject of this dissertation is the cluster type entangled coherent states. We propose a new scheme for the generation of this kind of state among four spatially separated cavities using only one atom and two Ramsey zones and also study the energy dissipation influence / Mestrado / Física Atômica e Molecular / Mestre em Física

Orientadores: Jose Antonio Roversi, Antonio Vidiella Barranco / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-10T23:26:43Z (GMT). No. of bitstreams: 1 Munhoz_PabloParmezani_D.pdf: 2389817 bytes, checksum: 8dde8d8180015b471d0fc6581dc6ee87 (MD5) Previous issue date: 2008 / Resumo: Neste trabalho, analisamos conceitos de Informação Quântica e Óptica Quântica no contexto de Eletrodinâmica Quântica de Cavidades (CQED). Recentemente, CQED vem apresentando grandes avanços tecnológicos, justificando o interesse em várias propostas de implementação experimental. Na primeira parte do trabalho, consideramos o efeito da emissão espontânea num sistema de dois átomos de dois-níveis idênticos interagindo dispersivamente com o campo eletromagnético quantizado numa cavidade de alto fator de qualidade Q. Investigamos o efeito destrutivo do decaimento atômico na geração de estados maximamente emaranhados. Em particular, calculamos a fidelidade de teletransporte, obtendo o limite superior para a taxa de decaimento espontâneo dos átomos que ainda permite teletransporte usando tais estados como canal quântico. Na segunda parte, apresentamos os Estados Coerentes Emaranhados Tipo-Cluster (CTECS) e discuti-mos suas propriedades. Apresentamos um esquema de geração desses estados em cavidades, mediante escolhas convenientes de interações átomo-cavidade, através do ajuste de dessintonias e aplicação de um campo clássico externo. Após a realização de medidas atômicas, CTECS representando campos eletro-magnéticos não-locais em cavidades separadas podem ser gerados. Generalizamos o esquema de geração para 2p-cavidades e analisamos a utilidade do CTECS gerado para teletransporte, considerando perda de fótons nas cavidades / Abstract: In this work, we analyze concepts of Quantum Information and Quantum Optics in the context of Cavity Quantum Electrodynamics (CQED). Nowadays, CQED is achieving great technological advances, justifying the interest in several proposals of experimental implementation. In the first part of the work, we consider the effect of spontaneous emission in a system of two identical two-level atoms dispersively interacting with the quantized electromagnetic field inside a high quality factor Q cavity. We investigate the destructive effect of the atomic decay in the generation of maximally entangled states. In particular, we compute the fidelity of teleportation, obtaining an upper limit for the spontaneous atomic decay rate which still allows teleportation using those states as quantum channels. In the second part, we present the cluster-type entangled coherent states (CTECS) and discuss their properties. We present a generation scheme of these states in cavities, by means of convenient choices of atom-field interactions, through adjustments of detunings and application of a classical external field. After the realization of simple atomic measurements, CTECS representing nonlocal electromagnetic fields in separate cavities can be generated. We generalize the scheme for 2p-cavities, analyzing the utility of the generated CTECS for teleportation, considering photon leakage in the cavities / Doutorado / Física Clássica e Física Quântica : Mecânica e Campos / Doutor em Ciências

Dans cette thèse, nous avons étudié l'impact considérable de désordre aléatoire sur le transport de la lumière lente dans les guides à cristaux photoniques 1D, c'est-à-dire la localisation de la lumière. Les mesures en champ proche, les simulations statistiques et le modèle théorique révèlent l'existence d'une limite inférieure de l’extension spatiale des modes localisés. Nous avons également présenté que le niveau de désordre et l’extension spatiale de mode localisé individuelle sont liés par la masse effective de photons plutôt que la vitesse de groupe considérant en général.Deuxièmement, les systèmes hybrides d'atomes froids et des guides à cristaux photoniques ont été reconnus comme un approche prometteuse pour l'ingénierie grande interaction lumière-matière au niveau des atomes et des photons individuels. Dans cette thèse, nous avons étudié la physique, à savoir le transport de la lumière dans des guides de nanophotonique périodiques couplées à des atomes à deux niveaux. Notre expression semi-analytique développée est générale et peut rapidement caractériser le couplage entre les atomes froids et les photons guidées. Pour surmonter les difficultés techniques considérables existent dans les systèmes hybrides atomique et photonique, nous avons conçu un guide nanophotonique qui supporte un mode de Bloch lente guidée avec grande queue évanescente dans l'espace libre pour les atomes froids de piégeage. Pour adapter précisément la région de fréquence de la lumière lente du mode guidé à la ligne de transition atomique, nous avons conçu la bande photonique et de la courbe de dispersion du mode guidé afin que la force de l'interaction est robuste contre imprévisible fabrication imperfection. / In this thesis, we firstly investigated the striking influence of random disorder on light transport near band edges in one dimensional photonic crystal wave guides, i.e. light localization. Near-field measurements, statistical simulations and theoretical model revealed the existence of a lower bound for the spatial extent of localized modes. We also showed that the disorder level and the spatial extent of individual localized mode is linked by the photon effective mass rather than the generally considered group velocity. Secondly, hybrid cold atoms and photonic crystal wave guides system have been recognized as a promising paradigm for engineering large light-matter interaction at single atoms and photons level. In this thesis, we studied the basic physics, i.e. light transport in periodic nanophotonic wave guides coupled to two-level atoms. Our developed general semi-analytical expression can quickly characterize the coupling between cold atoms and guided photons. Aim to overcome the significant technical challenges existed for developing hybrid atom-photonic systems, we designed a nanophotonic waveguide, which supports a slow guided Bloch mode with large evanescent tail in free space for cold atoms trapping (release the limitation imposed by Casmir Polder force and technical challenge of nanoscale manipulation of cold atoms). To match precisely the slow light region of the guided mode to the atomic transition line, we carefully engineered the photonic band and the dispersion curve (i.e.flatness) of the guided mode so that the interaction strength is robust against unpredictable fabrication imperfection.

Dans ce mémoire de thèse, je rapporte les résultats des études réalisées durant ces trois dernières années à l'Institut Non Linéaire de Nice. D'une part, je présente nos expériences de miroir de rétro-action conduisant à la formation spontanée de patterns dans la section transversale d'un faisceau laser (pompe) traversant le centre d'un nuage d'atomes froids de 87Rb et rétro-réfléchi par un miroir placé à une distance du nuage. Dans ces expériences nous discernons trois types de mécanismes de nonlinéarités : la nonlinéarité de spin qui est liée au pompage Zeeman, la nonlinéarité électronique existant pour un atome à deux niveaux et la nonlinéarité opto-mécanique qui est liée à la force dipolaire. Ces mécanismes dépendant des paramètres du MOT et de la pompe (intensité, désaccord, durée) sont étudiés séparément en jouant sur ces paramètres. Ces études expérimentales sont comparées avec des résultats obtenus avec des modèles théoriques. D'autre part, je présente nos observation concernant la densité d'état intégrée et les la densité d'états locale des bandes d'un quasi-cristal bidimensionnel. Dans cette expérience réalisée au Laboratoire de Physique de la Matière Condensée, nous avons réalisé des quasi-cristaux en disposant des résonateurs diélectriques agissant dans le domaine micro-onde sur des pavages de Penrose 2D. Un modèle numérique prenant en compte les paramètres expérimentaux est utilisé pour comparer les résultats obtenus. / First, I present our feedback experiment leading to the spontaneous formation of patterns in the cross section of a laser beam passing through a cloud of cold 87Rb atoms and retroreflected by a mirror. In these experiments we were able to identify three mechanisms of nonlinearity: the spin nonlinearity associated with the Zeeman degrees of freedom, the electronic nonlinearity due to the saturation of a two-level atom and the optomechanical nonlinearity due to the spatial bunching of atoms by the dipole force. The instabilities corresponding to each nonlinear mechanism occurs in different range of the experimental parameters and can be selected and studied independently. The experimental observations are compared with various theoretical models. In the second part of the thesis, I present our study of the integrated density of states (IDOS) and the local density of states (LDOS) of the bands of a two-dimensional quasicrystal. In an experiment conducted at Laboratoire de Physique de la Matière Condensée (LPMC), we realized quasicrystals by disposing dielectric resonators operating in the microwave regime on 2D Penrose tiling. A numerical model including experimental parameters is used to compare to the experimental findings.

L'augmentation de l'interaction lumière-matière aux échelles micro et nanométriques est un des fers de lance de la nanophotonique. En effet, le contrôle de la répartition spatiale de la lumière grâce à l'interaction résonante entre nanostructures et ondes électromagnétiques a conduit aux développements de nombreuses applications dans des domaines variés tels que les télécommunications,la spectroscopie et la détection d'objets. Le ralentissement de la lumière, sujet de la thèse, obtenue grâces à l'interférence d'ondes contre-propageantes dans des milieux périodiques ou le confinement sub-longueur d'onde dans des guides d'ondes plasmoniques, est associé à une compression des pulses lumineux et une forte augmentation du champ électrique, deux phénomènes clés pour la miniaturisation de composées optiques et l'augmentation de l'interaction lumière matière. / Enhancing light-matter interactions at micro and nanoscales is one of the spearheads of nanophotonics. Indeed, the control of the field distribution due to the resonant interaction of nanostructures with electromagnetic waves has prompted the development of numerous optical components for many applications in telecommunication, spectroscopy or sensing. A promising approach lies in the control of light speed in nanostructures. Light slowdown, obtained by wave interferences in periodic structures or subwavelength confinement in plasmonic waveguides, is associated to pulse compressions and large field enhancements,which are envisioned as key processes for the miniaturization of optical devices and the enhancement of light-matter interactions.The thesis studies both fundamental aspects and possible applications related to slow light in photonic and plasmonic nanostructures. In particular, we study the impact of periodic system sizes on the group velocity reduction and propose a novelfamily of resonators that implement slow light on very small spatial scales. We then investigate the role of fabrication disorder in slow periodic waveguides on light localization and demonstrate how modal properties influence the confinement of localized modes. Also we propose a new hollow-core photonic crystal waveguide that provides efficient and remote couplings between the waveguide and atoms thatare trapped away from it. Finally we demonstrate the important role played by slow plasmons on the emission of quantum emitters placed in nanogap plasmonic antennas and explain how large radiation efficiency can be achieved by overcoming quenching in the metal. Additionally, one part of the thesis is devoted to thederivation of a novel modal method to accurately describe the dynamics of plasmonic resonators under short pulse illumination.