Les interféromètres stellaires sont des dispositifs à très haute résolution angulaire, permettant une étude approfondie de l’Univers. Cette thèse décrit la mise en place en laboratoire d’un interféromètre à somme de fréquences dédié à la détection de rayonnement infrarouge en bande L :ALOHA@3.39. Afin de pouvoir limiter le bruit généré par les rayonnements thermiques ambiants et de pouvoir bénéficier des technologies matures en terme de détection et de transport cohérents de la lumière collectée, ce système intègre sur chacune des voies interférométrique un processus non linéaire de somme de fréquence. Les rayonnements autour de 3.39 μm sont transposés autour de 810 nm via des cristaux de PPLN alimentés par une pompe unique à 1064 nm. Une première partie présente le contexte expérimental et théorique de la thèse. La deuxième partie concerne la conception, la réalisation et la caractérisation du banc ALOHA@3.39. La troisième partie présente les résultats expérimentaux obtenus en laboratoire. La mesure répétée du contraste en régime de fort flux permet de calibrer le contraste instrumental du montage. Les premières mesures en régime de comptage de photons montrent que nous sommes actuellement capables de détecter des franges d’interférence avec de hauts contrastes en ne disposant que de 100 Fw à l’entrée de chacune des voies. Enfin, nos investigations nous ont amené à la détection de franges d’interférences via le prototype ALOHA@3.39 à partir d’une source thermique, assimilable à un corps noir. Cette thèse conclue sur une estimation de la magnitude limite accessible, et sur l’utilisation de nouvelles technologies de PPLN. / Stellar interferometers are high angular resolution devices, allowing for detailed research of the Universe. This thesis describes the in-lab implementation of a sum frequency generation interferometer dedicated to the infrared detection in the L band : ALOHA@3.39. In the aim of limiting thermal noise due to the room radiation, and benefit mature detectors and fibered components, this device includes a sum frequency generation non-linear process on each of its arms. Stellar radiations around 3.39 μm are transposed to around 810 nm thanks to PPLN cristals powered by a single pump signal at 1064 nm. The first part presents our global experimental context and theoretical elements about this thesis. The second part deals with the conception, the implementation and characterisation of the test bench ALOHA@3.39. The third part tables in-lab experimental results. Repeated measurements of the fringe contrast on high flux regime allow to calibrate the instrumental contrast of the set-up. First measurements on photon counting regime show we are currently able to detect interference fringes with high contrast with only 100 fW at the input of each arm. Finally, our research led us to realise interference fringes detection via the ALOHA@3.39 prototype, observing a thermal source, considered as a black body. This thesis concludes on an estimation of the limiting reachable magnitude, and on the future use of new PPLN technologies.

O fitoplâncton é sensível às perturbações ambientais e identificar a viabilidade destes organismos é importante para o monitoramento aquático. O termo viabilidade tem sido usado neste contexto para determinar basicamente se o organismo está vivo ou morto. O uso de corantes vitais e mortais tem sido uma das técnicas aplicadas neste tipo de análise, mas ainda não se conhece a potencialidade de alguns corantes que se apliquem a espécies de fitoplâncton. Neste trabalho, foram utilizadas espécies de diferentes grupos taxonômicos mantidas em cultivo, as quais foram submetidas a uma série de corantes vitais e mortais com o objetivo de detectar a viabilidade do fitoplâcton marinho. Dentre os corantes testados, o vermelho neutro, azul de Evans e o fluorescente CMFDA tiveram os melhores resultados (observado x esperado) em testes com diferentes porcentagens de células vivas e mortas. A combinação entre o corante vital vermelho neutro e o mortal azul de Evans não foi efetiva para análise simultânea. Alexandrium tamiyavanichii foi a espécie que teve menor afinidade com os corantes. Também foram comparados diferentes métodos de observação e registro de células coradas e não coradas, provando que é possível substituir a observação direta da microscopia pela filmagem no microscópio ou pela FlowCAM. A vantagem do uso destes métodos é que além de serem mais rápidos, é possível salvar as imagens capturadas e não é necessário fazer a análise instantaneamente. O método da filmagem é vantajoso, pois é fácil de ser desenvolvido em qualquer laboratório. / Phytoplankton cells are sensitive to environmental perturbations and, therefore, identifying their viability is important for aquatic monitoring. The term viability has been used in this context to determine whether an organism is alive or dead. The use of vital and mortal stains to detect phytoplankton viability is a promising approach. In this study we investigated the efficiency of several vital and mortal dyes in detecting marine phytoplankton viability. Best results were achieved with neutral red, Evans blue and the fluorescent stain in tests with different percentages of live and dead cells. The combination of neutral red and Evans blue (vital and a mortal stains, respectively) was not effective in simultaneous analysis. Alexandrium tamiyavanichii had low affinity for any given stain. Different observational methods were compared, suggesting that direct microscopic counts can be replaced by image acquisition methods using either a microscope-mounted camera or a FlowCAM. Such imaging methods are fast, allow image archiving, and image processing can be performed on a later stage, which is useful when several experiments need to be run in a short period of time.

Le processus de somme de fréquences optiques est utilisé dans certaines applications pour convertir des signaux de longueurs d’onde infrarouges vers le domaine de longueurs d’onde visibles. Cela permet de bénéficier de technologies plus performantes notamment en terme de détection et de propagation. Les travaux menés dans cette thèse s’intéressent à l’étude de phénomènes optiques parasites générés par ce processus non linéaire dans des cristaux de niobate de lithium périodiquement polarisés (PPLN) pour des applications de conversion de fréquences en régime de comptage de photons. La première partie de ce manuscrit montre l’intérêt du processus de somme de fréquences optiques dans le contexte technologique de la détection infrarouge en régime de comptage de photons, via le concept de détection hybride. Les éléments théoriques et l’état de l’art associés à la détection hybride seront également présentés dans cette première partie. La deuxième partie traite d’une étude comparative entre différents cristaux de PPLN pour la détection hybride à 1550 nm. Pour cela, une analyse expérimentale détaillée des processus parasites est effectuée. Les résultats de cette étude sont utilisés pour des applications en astronomie et en microscopie. Enfin, la troisième partie traite d’une application de la somme de fréquences en interférométrie stellaire. Les résultats de caractérisation des cristaux de PPLN sont mis à contribution dans l’optimisation d’un instrument pour l’astronomie appelé interféromètre à somme de fréquences. Les résultats d’observation sur le site astronomique du Mont Wilson ainsi que les perspectives de cette instrument y sont présentés. / The sum frequency generation process is used in differents applications to convert signals from infrared wavelengths to the field of visible wavelength. This allows to benefit of more efficient technologies in terms of detection and propagation. This thesis describes the study of noise phenomena generated by this process in crystals of periodically poled lithium niobate (PPLN) for frequency up-conversion applications in photon counting regime. The first part of the manuscript shows the advantage of sum frequency generation process in the technological environment of the infrared detection on single photon counting regime, using the concept of hybrid detection. The theoretical elements and the state of the art associated with hybrid detection will also be presented in this first part. The second part deals with a comparative study between different PPLN for hybrid detection at 1550 nm. A detailed experimental analysis of the noise process is performed. The results of this study are used for applications in astronomy and microscopy. The third part deals with an application of the sum frequency in stellar interferometry. The results of PPLN’s characterization are involved in optimizing an instrument for astronomy called sum frequency interferometer. The results of observation on the astronomical site of Mount Wilson and the prospects of this instrument are presented.

Le problème du dénombrement d’un grand nombre de très petits objets en mouvement dans les vidéos est un contexte applicatif jusqu’à présent peu étudié.Dans ce cadre, la difficulté réside essentiellement dans le fait qu’en raison de leurs très petites tailles apparentes dans la vidéo, il n’est pas possible de définir un modèle géométrique fiable de ces objets. Or, les travaux existants dans le domaine de la détection d’objets dans des vidéo, utilisent souvent un tel modèle géométrique des objets d’intérêt. Les méthodes de détection existantes ne sont de ce fait pas applicables directement dans le cadre de la détection de tels très petits objets. Dans le cadre de cette thèse, il est proposé une méthodologie complète permettant la détection de nombreux petits objets, avec un cadre applicatif visant plus particulièrement la détection et le comptage d’oiseaux migrateurs dans une vidéo. Le principe innovant, proposé en tant qu’une solution de ce problème, consiste à associer des coefficients de fiabilité de détection aux objets pour les dénombrer tout en évitant de prendre en compte de trop nombreuses fausses détections. Un algorithme hiérarchique analysant l’aspect spatio-temporel d’objets (leurs apparence et l’évolution dans le temps) dans une vidéo à l’aide de méthodes de traitement d’images, de statistique et de la logique floue est ainsi proposé. Le but des coefficients de fiabilité est d’estimer la probabilité que les paramètres d’une détection correspondent aux paramètres attendus pour les objets d’intérêt. Finalement, l’ensemble des coefficients est converti en une valeur qui évalue la séquence du traitement d’un objet. La somme de ces valeurs correspond au nombre d’objets d’intérêt dans une vidéo. Les résultats obtenus montrent que les bonnes détections sont pour la plupart comprises dans le dénombrement avec des coefficients de fiabilité égaux ou proche de 1, et où les fausses détections sont supprimées ou sous-pondérés avec des coefficients de fiabilité plus faible. Les résultats de comptage dans des vidéos contenant de très nombreux oiseaux sont proches de la vérité terrain, ce qui prouve la validité de la solution proposée comme un moyen de dénombrement automatique d’objets dans des vidéos. / The problem of counting of big volumes of very small moving objects in videos is a domain, which was not studied to date. The difficulty of this application consists essentially in the fact, that because of very small sizes of objects, apparent in the videos, it is impossible to define a reliable geometric model of these objects. The researches, existing in the domain of object detection in videos frequently use a geometrical model of objects of interest.For this reason, the existing methods of object detection cannot be applied for the detection of very small objects in the study case. This thesis proposes a complete methodology, allowing the detection of very small objects in videos, and designed particularly the detection and counting of migrating birds in videos. An innovative principle and the solution of this problem consist in association of coefficients of detection reliability to the objects, in order to count them, avoiding counting of many false detections. The solution proposes a hierarchical algorithm, which analyses the spatial and temporal aspects of objects (their appearance and evolution in time) in a video, by the means of methods of image processing, statistics, and fuzzy logic. The aim of the reliability coefficients is to estimate the probability, that the parameters of a detected objects conform to the expected parameters of the objects of interest. Finally, the coefficients are put together and converted into a value, which evaluates the sequence of processing, applied to detect an object. The sum of these values corresponds to the number of the objects of interest in a video. The results show, that the most of correct detections are characterized in the counting by the reliability coefficient equal or close to 1. The results show, that the most of correct detections have their reliability coefficients close to 1, and the false detection are deleted or have low reliability coefficients. The counting results in the videos with numerous groups of migrating birds are close to the ground trough. This validates the proposed solution as a method of automatic counting of objects in videos.

Orientador: Prof. Dr. André Ricardo Oliveira da Fonseca / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Mestrado Profissional em Matemática em Rede Nacional - PROFMAT, 2014. / Contar elementos pode ser uma das mais antigas atividades que o ser humano tem registro. O desenvolvimento desse assunto deu origem à análise combinatória que estuda técnicas de contagem sem a necessidade de contar os elementos um a um. O objetivo deste trabalho é desenvolver algumas técnicas de contagem durante o Ensino Fundamental, para que o aluno se aproprie delas, mesmo que intuitivamente, e diminua as dificuldades na formalização do conteúdo que ocorre apenas no Ensino Médio. Abordado pela maioria dos livros didáticos em pilares, como arranjos, permutações e combinações, muitas vezes induzem os estudantes à memorização de fórmulas, que podem ser objeto de uma simples escolha que julguem ser a mais adequada na resolução de determinado problema. / Counting elements can be one of the oldest activities that humans have recorded. This subject development gave rise to the combinatorial analysis studies which focus on counting techniques without the need to count the elements one by one. The aim of this work is to develop some techniques of counting during the Fundamental Education, for the student to take ownership of them, even intuitively, and decrease the difficulties when formalizing the content itself, what may occur only in High School. Approached by most textbooks on pillars, as arrangements, permutations and combinations, books often induce students to memorize formulas, which can be subject to a simple choice they deem to be most appropriate in solving a given problem.

O Instituto de Pesquisas Energéticas e Nucleares IPEN-CNEN/SP produz rotineiramente o combustível nuclear necessário para a operação de seu reator de pesquisas IEA-R1. Esse combustível é formado por placas combustíveis contendo núcleos de dispersões U3Si2-Al, obtidas por laminação. As placas combustíveis sofrem um tratamento químico para limpeza de sua superfície, com o objetivo de garantir a remoção de qualquer impureza presente em suas superfícies, incluindo resíduos de urânio. Nos últimos 10 anos foram constatados de forma esporádica aumentos significativos na atividade radioativa da água da piscina do reator IEA-R1. O aumento da atividade no ambiente do reator foi relacionado à entrada na piscina de elementos combustíveis recém-fabricados, entrando em operação. Apesar do processo de tratamento superficial atual estar perfeitamente estável e reprodutível, uma possível causa para o aumento da atividade da água da piscina do reator IEA-R1 é a presença de contaminação residual de urânio na superfície não retirada pelo tratamento químico superficial. Durante anos, esse problema não foi observado devido à baixa potência de operação do reator, no nível de 2 MW. Contudo, com o aumento da potência, acima de 3,5 MW, esse problema começou a ser observado. Esse trabalho verifica a hipótese da contaminação residual de urânio na superfície das placas combustíveis de forma estatística e caracteriza a adequação do processo de tratamento superficial de placas combustíveis. Utilizou-se uma metodologia estatística de avaliação do processo em três níveis: produção presente, contaminação intencional, produção histórica. A contagem de emissões alfa por contador de NaI permitiu a quantificação de urânio residual. Como resultado global, verificou-se que pode ocorrer contaminação abaixo de 1 g de 235U por elemento combustível. Essa contaminação não é significante para causar eventuais acidentes de aumento de atividade no reator IEA-R1. Provou-se no presente trabalho que a metodologia de contagens de emissões alfa é segura, precisa e rápida para se analisarem contaminações superficiais de urânio nas placas combustíveis. / Nuclear and Energy Research Institute - IPEN-CNEN/ SP routinely produces its own nuclear fuel elements, necessary for the operation of its research reactor IEA-R1. This fuel consists of fuel plates containing cores U3Si2-Al dispersions obtained by rolling. Fuel plates undergo a chemical treatment for surface cleaning, aiming to ensure the removal of any impurity present on the surface, including uranium residual dust. Over the past 10 years, it was found sporadically a significant increase of radioactivity emission in water pool of IEA-R1 reactor. The increased activity in the reactor environment was related to the use of newly fabricated fuel elements fed into the core. Although the actual surface treatment process to be perfectly stable and reproducible, a possible cause for the activity increase would be the presence of residual uranium contamination over the surface, which was not removed by chemical surface treatment. For years, this problem was not observed due to the low power of reactor operation, at the level of 2 MW. However, with the increase in power above 3.5 MW, this problem started to be observed. This work verifies the hypothesis of residual uranium contamination on the surface of the fuel plates in a statistical methodology and features the adequacy of the fuel plate surface treatment process. We evaluated, statistically, the process into three levels: present production, intentional contamination, historical production. The NaI alpha emission counter allowed quantification the amount of uranium residual. As an overall result, it was found that contamination may occur below 1 g of 235U per fuel element. The contamination was judged as not significant to cause any activity accidents in the IEA-R1. It has been proven in this paper that the methodology to count alpha emissions is secure, accurate and fast to analyze surface uranium contamination in nuclear fuel plates.

O fitoplâncton é sensível às perturbações ambientais e identificar a viabilidade destes organismos é importante para o monitoramento aquático. O termo viabilidade tem sido usado neste contexto para determinar basicamente se o organismo está vivo ou morto. O uso de corantes vitais e mortais tem sido uma das técnicas aplicadas neste tipo de análise, mas ainda não se conhece a potencialidade de alguns corantes que se apliquem a espécies de fitoplâncton. Neste trabalho, foram utilizadas espécies de diferentes grupos taxonômicos mantidas em cultivo, as quais foram submetidas a uma série de corantes vitais e mortais com o objetivo de detectar a viabilidade do fitoplâcton marinho. Dentre os corantes testados, o vermelho neutro, azul de Evans e o fluorescente CMFDA tiveram os melhores resultados (observado x esperado) em testes com diferentes porcentagens de células vivas e mortas. A combinação entre o corante vital vermelho neutro e o mortal azul de Evans não foi efetiva para análise simultânea. Alexandrium tamiyavanichii foi a espécie que teve menor afinidade com os corantes. Também foram comparados diferentes métodos de observação e registro de células coradas e não coradas, provando que é possível substituir a observação direta da microscopia pela filmagem no microscópio ou pela FlowCAM. A vantagem do uso destes métodos é que além de serem mais rápidos, é possível salvar as imagens capturadas e não é necessário fazer a análise instantaneamente. O método da filmagem é vantajoso, pois é fácil de ser desenvolvido em qualquer laboratório. / Phytoplankton cells are sensitive to environmental perturbations and, therefore, identifying their viability is important for aquatic monitoring. The term viability has been used in this context to determine whether an organism is alive or dead. The use of vital and mortal stains to detect phytoplankton viability is a promising approach. In this study we investigated the efficiency of several vital and mortal dyes in detecting marine phytoplankton viability. Best results were achieved with neutral red, Evans blue and the fluorescent stain in tests with different percentages of live and dead cells. The combination of neutral red and Evans blue (vital and a mortal stains, respectively) was not effective in simultaneous analysis. Alexandrium tamiyavanichii had low affinity for any given stain. Different observational methods were compared, suggesting that direct microscopic counts can be replaced by image acquisition methods using either a microscope-mounted camera or a FlowCAM. Such imaging methods are fast, allow image archiving, and image processing can be performed on a later stage, which is useful when several experiments need to be run in a short period of time.

Cette thèse se compose de plusieurs travaux portant sur deux branches de la théorie des probabilités: processus de particules et cartes planaires aléatoires. Un premier travail concerne les aspects algébriques des mesures invariantes des processus de particules. Nous obtenons des conditions nécessaires et suffisantes sous lesquelles un processus de particules en temps continu avec espace d’états local discret possède une mesure invariante simple. Dans un deuxième travail nous étudions un modèle "biologique" de coexistence de 2 espèces en compétition sur un espace partagé, et soumis à des épidémies modélisées par un modèle probabiliste appelé "feux de forêts". Notre résultat principal montre que pour deux espèces, il existe des régions explicites de paramètres pour lesquelles une espèce domine ou les deux espèces coexistent. Il s’agit d’un des premiers modèles pour lesquels la coexistence d’espèces sur le long terme est prouvée. Les troisièmes et quatrièmes travaux. portent sur les cartes planaires décorées par des arbres. Dans le troisième nous présentons une bijection entre l’ensemble des cartes décorées par des arbres et le produit Cartésien entre l’ensemble des arbres planaires et l’ensemble de cartes à bord simple. Nous obtenons quelques formules de comptage et quelques outils pour l’étude de cartes aléatoires décorées par un arbre. Le quatrième travail montre que les triangulations et quadrangulations aléatoires uniformes avec f faces, bord simple de taille p et décorées par un arbre avec a arêtes, convergent en loi pour la topologie locale vers différentes limites, dépendant du comportement fini ou infini de la limite de f, p et a. / This thesis consists in several works exploring some models belonging to two branches of probability theory: interacting particle systems and random planar maps. A first work concerns algebraic aspects of interacting particle systems invariant measures. We obtain some necessary and sufficient conditions for some continuous time particle systems with discrete local state space, to have a simple invariant measure. In a second work we investigate the effect on survival and coexistence of introducing forest fire epidemics to a certain two-species spatial competition model. Our main results show that, for the two-type model, there are explicit parameter regions where either one species dominates or there is coexistence; contrary to the same model without forest fires, for which the fittest species alwaysdominates. The third and fourth works are related to tree-decorated planar maps. In the third work we present a bijection between the set of tree-decorated maps and the Cartesian product between the set of trees and the set of maps with a simple boundary. We obtain some counting results and some tools to study random decorated map models. In the fourth work we prove that uniform tree-decorated triangulations and quadrangulations with f faces, boundary of length p and decorated by a tree of size a converge weakly for the local topology to different limits, depending on the finite or infinite behavior of f, p and a.

本文主要是探討漢語短語及詞彙層次的輕聲現象。關於短語性的輕聲，鄭良偉先生(1989)是從句法的觀點來分析，本文則採用韻律体系理論來探討。我們提議了一組焦點詞語的原則及幾個相關的制約。此外，我們從蕭宇超先生(1991 & 1994)的韻板計數理論來觀察輕聲的節奏問題，因而修訂了虛詞音板指派及音板連接方向的原則，也建議了一條抵輔音板加入的規則。 　　關於詞彙性的輕聲，我們採用McCarthy及Prince(1986)的構詞規型理論及Kiparsky(1973 & 1982)，Mohanan(1982 & 1986)的字構音韻學理論來探討此一現象。我們建議了詞彙性的輕聲基本上運作於楊抑格音步，然而抵輔調卻運作於抑楊格音步。觀察了相關的音韻及構詞規則，我們也發現到文獻上輕聲的語料可由層級的觀念來分析。 / This thesis deals with neutral tone sandhi in Mandarin Chinese at the phrasal and lexical levels. Previous research of the phrasal neutral tone, e.g., R. Cheng (1989), has focused only at the syntactic level. In this research, we employ prosodic theories (Selkirk (1984 & 1986), Nespor and Vogel (1986), etc.) to condition phrasal neutral tone sandhi, and propose a set of focal phrasing principles and a couple of relevant constraints. In addition, we discuss the rhythm of neutral tone under the framework of the beat-counting theory (Hsiao, 1991 & 1994) to see in what ways the theory has to be modified. We propose a pair of revised principles of functor beat assignment and directional beat adjunction, along with a backup rule of the default beat addition. 　　As to neutral tone at the lexical level, we incorporate morphological template theory (McCarthy and Prince (1986)), and lexical phonology theory (Kiparsky (1973 & 1982), Mohanan (1982 & 1986), etc.). We propose that lexical neutral tone target a trochaic foot template, while a default tone target an iambic foot template. Observing the relevant phonological and morphological rules, we find that the neutral-toned data in the literature can be somehow generalized by way of level ordering.

<p>This doctoral thesis summarizes research in quantum cryptography done at the Department of Electronics and Telecommunications at the Norwegian University of Science and Technology (NTNU) from 1998 through 2007.</p><p>The opening parts contain a brief introduction into quantum cryptography as well as an overview of all existing single photon detection techniques for visible and near infrared light. Then, our implementation of a fiber optic quantum key distribution (QKD) system is described. We employ a one-way phase coding scheme with a 1310 nm attenuated laser source and a polarization-maintaining Mach-Zehnder interferometer. A feature of our scheme is that it tracks phase drift in the interferometer at the single photon level instead of employing hardware phase control measures. An optimal phase tracking algorithm has been developed, implemented and tested. Phase tracking accuracy of +-10 degrees is achieved when approximately 200 photon counts are collected in each cycle of adjustment. Another feature of our QKD system is that it uses a single photon detector based on a germanium avalanche photodiode gated at 20 MHz. To make possible this relatively high gating rate, we have developed, implemented and tested an afterpulse blocking technique, when a number of gating pulses is blocked after each registered avalanche. This technique allows to increase the key generation rate nearly proportionally to the increase of the gating rate. QKD has been demonstrated in the laboratory setting with only a very limited success: by the time of the thesis completion we had malfunctioning components in the setup, and the quantum bit error rate remained unstable with its lowest registered value of about 4%.</p><p>More than half of the thesis is devoted to various security aspects of QKD. We have studied several attacks that exploit component imperfections and loopholes in optical schemes. In a large pulse attack, settings of modulators inside Alice's and Bob's setups are read out by external interrogating light pulses, without interacting with quantum states and without raising security alarms. An external measurement of phase shift at Alice's phase modulator in our setup has been demonstrated experimentally. In a faked states attack, Eve intercepts Alice's qubits and then utilizes various optical imperfections in Bob's scheme to construct and resend light pulses in such a way that Bob does not distinguish his detection results from normal, whereas they give Bob the basis and bit value chosen at Eve's discretion. Construction of such faked states using several different imperfections is discussed. Also, we sketch a practical workflow of breaking into a running quantum cryptolink for the two abovementioned classes of attacks. A special attention is paid to a common imperfection when sensitivity of Bob's two detectors relative to one another can be controlled by Eve via an external parameter, for example via the timing of the incoming pulse. This imperfection is illustrated by measurements on two different single photon detectors. Quantitative results for a faked states attack on the Bennett-Brassard 1984 (BB84) and the Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols using this imperfection are obtained. It is shown how faked states can in principle be constructed for quantum cryptosystems that use a phase-time encoding, the differential phase shift keying (DPSK) and the Ekert protocols. Furthermore we have attempted to integrate this imperfection of detectors into the general security proof for the BB84 protocol. For all attacks, their applicability to and implications for various known QKD schemes are considered, and countermeasures against the attacks are proposed.</p><p>The thesis incorporates published papers [J. Mod. Opt. 48, 2023 (2001)], [Appl. Opt. 43, 4385 (2004)], [J. Mod. Opt. 52, 691 (2005)], [Phys. Rev. A 74, 022313 (2006)], and [quant-ph/0702262].</p>