Orientador: Jose Antonio Roversi / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-09T01:48:12Z (GMT). No. of bitstreams: 1 Yabu-uti_BrunoFerreiradeCamargo_M.pdf: 1406553 bytes, checksum: 938ab0006a4b98ac2e95d69ce2f1f39f (MD5) Previous issue date: 2007 / Resumo: Nessa dissertação de mestrado estudamos a dinâmica do emaranhamento entre dois átomos remotos localizados em cavidades distintas. O foco principal é a produção de estados maximamente emaranhados entre átomos de dois níveis em cavidades distintas e, em particular, acopladas. Inicialmente apresentamos os principais conceitos da Teoria de Informação Quântica, aspectos qualitativos e quantitativos do emaranhamento quântico, em seguida partimos para o sistema físico proposto: átomos em cavidades. Apresentamos o modelo de Jaynes-Cummings (MJC) e uma breve análise do emaranhamento que surge da interação átomo-campo descrita por esse modelo. No sistema de duas cavidades desacopladas apresentamos como gerar emaranhamento entre átomos remotos de forma condicional. É apresentado então o sistema formado por duas cavidades acopladas interagindo com átomos de dois níveis idênticos, fato que corresponde a constantes de acoplamento átomo-campo iguais (g1= g2). A interação àtomo-campo ainda é descrita pelo MJC já o sistema das cavidades acopladas pode ser modelado conforme a proposta de Zoubi et. al [1](para cavidades separadas por um meio físico a uma curta distância) ou pela proposta de Pellizzari [2](para cavidades conectadas por uma fibra ótica). Para escolhas adequadas dos parâmetros relevantes em cada caso, a dinâmica dos dois sistemas é equivalente a interação dos áomos com um campo mono-modo. Em conseqüência da aparente simplicidade, investigamos a dinâmica do emaranhamento entre átomos distantes, incluindo a geração de estados maximamente emaranhados (essencial para o processamento de informação quântica, comunicação quântica [3] e computação quântica distribuída [4, 5] ) de forma determinística e sem a necessidade de uma interação indireta entre os modos das cavidades para gerar um estado inicial emaranhado compartilhado / Abstract: In this work, we study the dynamics of the entanglement between two remote atoms in distinct cavities. The main focus is the production of maximal entangled states between identical atoms of two levels in distinct cavities and, in particular, coupled cavities. Initially we present the main concepts of the Theory of Quantum Information, qualitative and quantitative aspects of the quantum entanglement, after that we consider the physical system: atoms in cavities. We present the Jaynes-Cummings model (JCM) and make one brief analysis of the entan-glement that appears due to such atom-field interaction. In the system of two uncoupled cavities we present how to generate entanglement between remote atoms in conditional form. We introduce the system formed by two coupled cavities interacting with identical atoms, fact that corresponds to identical coupling constant (g1= g2). The atom-field interaction is still described by the JCM and the system of coupled cavities can be modeled by the Zoubi et. al.¿s proposal [1] (for separate cavities for an environment for a short distance) or for the Pellizzari¿s proposal [2] (for cavities connected by a optical fiber). For appropriate choices of parameters in each case, the dynamics of the two systems is equivalent to the interaction of atoms with a mono-mode field. Due to the apparent simplicity, we investigate the dynamics of the entanglement between distant atoms, including the generation of maximal entangled states (essential for the processing of quantum information, quantum communication [3] and distributed quantum computation [4,5] ) in determinist form and without necessity of an indirect interaction between the modes of the cavities to generate a shared entangled initial state / Mestrado / Física / Mestre em Física

[pt] Neste trabalho, desenvolvemos um laser a fibra, monomodo e de cavidades acopladas, cujo meio de ganho é uma Fibra Dopada com Érbio. As duas cavidades, C1 e C2, foram feitas no mesmo pedaço de fibra dopada, com a mesma concentração de Érbio (Er) e mesmo índice de refração. A Fibra Dopada com Érbio usada era também dopada com Germânio (Ge), que aumenta a fotossensitividade da fibra. Portanto, foi possível escrever Redes de Bragg na mesma fibra para serem usadas como os espelhos da cavidade. A configuração do laser consiste em três Redes de Bragg, escritas no mesmo núcleo da fibra, centradas em 1532nm e separadas por 30cm. As reflectividades das Redes de Bragg eram de 95 por cento, 80 por cento e 60 por cento. Com essa configuração simples de cavidades acopladas, conseguimos uma emissão laser estável e monomodo. Será apresentado também um estudo teórico para descrever o sistema. / [en] In this work, we developed a single mode coupled cavity fiber laser, in which the gain medium is an Erbium Doped Fiber. The two cavities, C1 and C2, were made in the same piece of the doped fiber, with the same concentration of Erbium (Er) and the same refraction index. The Erbium Doped Fiber used was codoped with Germanium (Ge), which increases the photosensitivity of the fiber. Therefore, it was possible to write bragg Gratings in the same fiber to be used as the cavity mirrors. The laser configuration consists of three Bragg Gratings, written in the core of the fiber, centered in 1532 nm and separated by 30cm. Ther Bragg Grating reflectivities were 95 per cent, 80 per cent and 60 per cent. With this simple configuration of coupled cavities, a stable, single mode laser emission was achieved. A theoretical study to describe the system will also be presented.

L’optique non linéaire traite les modifications des propriétés optiques d'un matériau induites par la propagation de la lumière. Depuis ses débuts, il y a cinquante ans, des nombreuses applications ont été démontrées dans presque tous les domaines de la science. Dans le domaine de la micro et nano-photonique, les phénomènes non linéaires sont à la fois au cœur d’une physique fondamentale fascinante et des applications intéressantes: ils permettent d'adapter et de contrôler le flux de lumière à une échelle spatiale inferieure à la longueur d'onde. En effet, les effets non linéaires peuvent être amplifiés dans des systèmes qui confinent la lumière dans des espaces restreints et avec de faibles pertes optiques. Des bons candidats pour ce confinement sont les nanocavités à cristaux photoniques (CPs), qui ont été largement étudiées ces dernières années. Parmi la grande diversité des processus non linéaires en optique, les phénomènes dynamiques tels que la bistabilité et l'excitabilité font l’objet de nombreuses études. La bistabilité est bien connue pour ces applications potentielles pour les mémoires et les commutateurs optiques et pour les portes logiques. Une réponse excitable typique est celle subjacente dans le déclanchement du potentiel d'action dans les neurones. En optique, l'excitabilité a été observée il y a une quinzaine d’années. Dans ce travail, nous avons étudié les régimes bistables, auto-oscillants et excitables dans des nanocavités semiconductrices III-V à CP. Afin de coupler efficacement la lumière dans les nanocavités, nous avons développé une technique de couplage par onde évanescente en utilisant une microfibre optique étirée. Grâce à cette technique, nous avons démontré pour la première fois l’excitabilité dans une nanocavité à CP. En parallèle, nous avons accompli la première étape vers la dynamique non linéaire dans un réseau de cavités couplées en démontrant le couplage optique linéaire entre nanocavitités adjacentes. Ceci a été réalisé en utilisant de mesures de photoluminescence en champ lointain. Un ensemble de résonateurs non linéaires couplés ouvre la voie à une famille de phénomènes dynamiques non linéaires très riches, basés sur la rupture spontanée de symétrie. Nous avons démontré théoriquement ce phénomène dans deux cavités couplées par onde évanescente. Les premières études expérimentales de ce régime ont été menées, établissant ainsi les bases pour une future démonstration de la rupture spontanée de symétrie dans un réseau de nanocavités non linéaires couplées. / Nonlinear optics concerns the modifications of the optical properties of a material induced by the propagation of light. Since its beginnings, fifty years ago, it has already found applications in almost any field of science. In micro and nano-photonics, nonlinear phenomena are at the heart of both fascinating fundamental physics and interesting potential applications: they give a handle to tailor and control the flow of light within a sub-wavelength spatial scale. Indeed, the nonlinear effects can be enhanced in systems allowing tight light confinement and low optical loses. Good candidates for this are the Photonic Crystal (PhC) nanocavities, which have been extensively studied in recent years. Among the great diversity of nonlinear processes in optics, nonlinear dynamical phenomena such as bistability and excitability have recently received considerable attention. While bistability is well known as a building block for all-optical memories, switching and logic gates, excitability has been demonstrated in optics about fifteen years ago: coming from neuroscience, it is the mechanism underlying action potential firing in neurons. In this work, we have studied bistable, self-pulsing and excitable regimes in InP-based PhC nanocavities. In order to achieve efficient light coupling into the nanocavities, we have developed an evanescent coupling technique using tapered optical microfibers. As a result, we have demonstrated for the first time excitability in a PhC nanocavity. In addition, we have accomplished the first step towards nonlinear dynamics in arrays of coupled cavities by demonstrating optical linear coupling between adjacent nanocavitites. This was achieved using far field measurements of photoluminescence. A set of coupled nonlinear resonators opens the door to a rich family of nonlinear dynamical phenomena based on spontaneous symmetry breaking. We have theoretically demonstrated this phenomenon in two evanescently coupled cavities. The first experimental studies on this regime were carried out, which establish a basis for a future demonstration of spontaneous symmetry breaking in arrays of nonlinear coupled PhC nanocavities.