Quantum theory describes our universe incredibly successfully. To our classically-inclined brains, however, it is a bizarre description that requires a reimagining of what fundamental reality, or 'ontology', could look like. This thesis examines different ontological features in light of the success of quantum theory, what it requires, and what it rules out. While these investigations are primarily foundational, they also have relevance to quantum information, quantum communication, and experiments on quantum systems. The way that quantum theory describes the state of a system is one of its most unintuitive features. It is natural, therefore, to ask whether a similarly strange description of states is required on an ontological level. This thesis proves that almost all quantum superposition states for d > 3 dimensions must be real - that is, present in the ontology in a well-defined sense. This is a strong requirement which prevents intuitive explanations of the many quantum phenomena which are based on superpositions. A new theorem is also presented showing that quantum theory is incompatible with macro-realist ontologies, where certain physical quantities must always have definite values. This improves on the Leggett-Garg argument, which also aims to prove incompatibility with macro-realism but contains loopholes. Variations on both of these results that are error-tolerant (and therefore amenable to experimentation) are presented, as well as numerous related theorems showing that the ontology of quantum states must be somewhat similar to the quantum states themselves in various specific ways. Extending these same methods to quantum communication, a simple proof is found showing that an exponential number of classical bits are required to communicate a linear number of qubits. That is, classical systems are exponentially bad at storing quantum data. Causal influences are another part of ontology where quantum theory demands a revision of our classical notions. This follows from the outcomes of Bell experiments, as rigorously shown in recent analyses. Here, the task of constructing a native quantum framework for reasoning about causal influences is tackled. This is done by first analysing the simple example of a common cause, from which a quantum version of Reichenbach's principle is identified. This quantum principle relies on an identification of quantum conditional independence which can be defined in four ways, each naturally generalising a corresponding definition for classical conditional independence. Not only does this allow one to reason about common causes in a quantum experiments, but it can also be generalised to a full framework of quantum causal models (mirroring how classical causal models generalise Reichenbach's principle). This new definition of quantum causal models is illustrated by examples and strengthened by it's foundation on a robust quantum Reichenbach's principle. An unusual, but surprisingly fruitful, setting for considering quantum ontology is found by considering time travel to the past. This provides a testbed for different ontological concepts in quantum theory and new ways to compare classical and quantum frameworks. It is especially useful for comparing computational properties. In particular, time travel introduces non-linearity to quantum theory, which brings (sometimes implicit) ontological assumptions to the fore while introducing strange new abilities. Here, a model for quantum time travel is presented which arguably has fewer objectionable features than previous attempts, while remaining similarly well-motivated. This model is discussed and compared with previous quantum models, as well as with the classical case. Together, these threads of investigation develop a better understanding of how quantum theory affects possible ontologies and how ontological prejudices influence quantum theory.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2016-06-30T17:58:39Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tulio FINAL - Dissertação.pdf: 1494431 bytes, checksum: d90053700bc882607a8c54c546d0eb98 (MD5) / Made available in DSpace on 2016-06-30T17:58:39Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tulio FINAL - Dissertação.pdf: 1494431 bytes, checksum: d90053700bc882607a8c54c546d0eb98 (MD5) Previous issue date: 2015-02-27 / CAPES / Investiga, guiado pelos conceitos teórico-metodológicos da Filosofia e da Ciência da Informação, como a Ciência da Informação, sobretudo brasileira, configura a sua pesquisa filosófica e os alicerces para sua construção enquanto Ciência. Adota o termo Filosofia da Informação bem como analisa seu conceito a partir do filósofo Italiano Luciano Floridi, devido ao seu pioneirismo em fomentar e apresentar as teorias para o estudo filosófico da Informação. Diante dessa perspectiva e para uma construção de uma estrutura panorâmica conceitual entre a Filosofia da Informação e a Ciência da Informação, analisa a literatura científica, sobretudo artigos, contidos na Base de Dados Referenciais de Artigos de Periódicos em Ciência da Informação (Brapci), usando os termos “Filosofia da Informação”; “Filosofia da Ciência da Informação” e “Luciano Floridi” para analisar as obras que tratam conceitualmente sobre a Filosofia da Informação, e assim poder identificar como está se configurando seu estudo na literature sobre Ciência da Informação o Brasil. A partir desse levantamento, constitui um corpus sobre os autores e temas relacionados à Filosofia da Informação floridiana, com o objetivo de realizar uma análise sobre os títulos identificados e, posteriormente, analisar as formas de apresentação da Filosofia da Informação no Brasil em suas modalidades de produção e circulação social do objeto. Para isto, identifica e estuda, utilizando a análise de conteúdo, os artigos que tratam da filosofia da informação, com o propósito de contribuir para a identificação do estudo filosófico da informação que emerge no Brasil. / Investigates, guided by theoretical and methodological concepts of Philosophy and Information Science, as the Information Science, particularly Brazil, sets his philosophical research and its foundations for its construction as Science. Adopts the term Information Philosophy and analyzes its concept from the Italian philosopher Luciano Floridi, due to its pioneering promote and present the theories to the philosophical study of Information. Given the perspective and a mounting a conceptualoverview structure of the Information Philosophy and Information Science, analyzes the scientific literature, especially articles contained in the Reference Database Articles Journals in Information Science (Brapci), using the terms "Information Philosophy"; "Information Philosophy of Science" and "Luciano Floridi" them to identify projects that address conceptually on the Philosophy of Information, and thus able to identify how you are setting up your study in Information Science Brazilian. From this survey, is a corpus of authors and topics related to Floridiana Philosophy ofInformation in order to perform an analysis of the identified titles and then examine ways of presenting Philosophy of Informationin Brazil in their method of production andsocial movement of the object. For this, identifies and analyzes within the content analysis, the articles dealing mainly the philosophy of information, in order to contribute to the identification of the philosophical study of information emerging in Brazil.

Ce mémoire propose une analyse conceptuelle de la vie privée et des enjeux éthiques qui s’y rapportent à l’ère des données massives et de l’essor de l’intelligence artificielle. Alors que la définition du concept de vie privée est encore disputée, les défis liés à son maintien dans le monde numérique d'aujourd'hui sont indéniables. L’analyse de ces enjeux requiert de faire appel à des éléments conceptuels provenant de la philosophie de l’information, mais également aux notions de structures de pouvoir tirées de la philosophie politique et de la sociologie. À travers ce prisme, ce travail offre un survol des éléments essentiels au traitement des enjeux de vie privée dans le contexte actuel d’utilisation des données massives, et défend qu’en l’absence de processus adéquats pour protéger et préserver la vie privée d'une personne en ligne, la capacité à maintenir une vie privée numérique devient illusoire. En définitive, un argument moral en faveur d’une meilleure protection de la vie privée en ligne est présenté, démontrant que la vie privée est notamment garante de l’autonomie des personnes. / This essay provides a conceptual analysis of privacy and the ethical issues that surround it in the age of big data and artificial intelligence. While the definition of privacy is still disputed, the challenges of maintaining it in today’s digital world are undeniable. In order to analyze these challenges, one can combine conceptual elements taken from the philosophy of information with notions of power found in political philosophy and sociology. Through this lens, this paper offers an overview of how one can address privacy-related ethical concerns in the current context of massive data collection, analysis and use. It is argued that, without adequate processes in place to protect and preserve one’s privacy online, the ability to maintain digital privacy becomes illusory. This paper concludes by providing a moral argument to demonstrate how privacy can be better preserved online, demonstrating that privacy is notably a condition of personal autonomy.