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Entanglement and Decoherence in Loop Quantum Gravity Alexandre Feller

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Entanglement and Decoherence in Loop Quantum Gravity Alexandre Feller Entanglement and Decoherence in Loop Quantum Gravity Alexandre Feller To cite this version: Alexandre Feller. Entanglement and Decoherence in Loop Quantum Gravity. Quantum Physics [quant-ph]. Université de Lyon, 2017. English. NNT : 2017LYSEN058. tel-01650029 HAL Id: tel-01650029 https://tel.archives-ouvertes.fr/tel-01650029 Submitted on 28 Nov 2017 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Numéro National de Thèse : 2017LYSEN058 Thèse de Doctorat de l’Université de Lyon opérée par l’École Normale Supérieure de Lyon École Doctorale 52 École Doctorale de Physique et d’Astrophysique de Lyon Discipline : Physique Soutenue publiquement le : 23 Octobre 2017 par Alexandre FELLER Entanglement and Decoherence in Loop Quantum Gravity Intrication et décohérence en gravitation quantique à boucles Devant le jury composé de : Pascal DEGIOVANNI Directeur de recherche ENS de Lyon Examinateur Ivette FUENTES Professor University of Nottingham Examinatrice Etera LIVINE Directeur de recherche ENS de Lyon Directeur de thèse Daniele ORITI Senior Scientist Max Planck Institute Rapporteur Simone SPEZIALE Chargé de recherhe Aix-Marseille Université Examinateur Daniel TERNO Associate Professor Macquarie University Rapporteur 2 Remember... Pour moi, les meilleurs remerciements que l’on peut adresser ne prennent pas la forme de quelques mots, formant à cet instant le début de la fin de trois belles années de travail doctoral, mais la forme de souvenirs, dans ma mémoire. Quoi qu’il en soit, je vais essayer ici de modestement les partager bien que cela paraîtra au lecteur parfois flou et obscur. La thèse a commencé il y trois ans et ce fut trois années incroyables. Et naturellement Etera a toujours été là en tant que directeur de thèse, pour m’apprendre le travail de recherche, pour m’aider et me guider dans mes questions, mes interrogations, mes zones d’ombres. Ça a été un vrai plaisir de travailler ensemble. Pas très loin, dans l’autre couloir, Pascal est dans son dortoir... pardon bureau, et fait son petit repos... pardon boulot. Il a était lui aussi, et le sera encore, un peu mon mentor. Grande nouvelle pour beaucoup au labo, il n’a pas été mon directeur mais, il faut un moment l’avouer, a beaucoup contribué à mon travail de part les nombreuses discussions que nous avons eues. Tous les deux forment la base du petit chercheur que je suis et voudrais être. Toujours au labo, comment ne pas mentionner mes frères Daltons, Clément et Benjamin, avec qui nous avons tellement été sérieux, tous les jours au bureau sous le regard bienveillant de Sigmund, du matin tôt jusqu’au soir tard, à travailler d’arrache-pied nos papiers, à discuter sans s’arrêter de science, de philosophie, de politique, de tous les sujets. Notre seul dérapage a été de bloquer et d’enfumer un peu trop de laboratoire un vendredi pour le désinsectiser. Pardon Thierry pour ce dérangement, mais j’en pouvais plus de ces bestioles, mon travail allait perdre en efficacité. Bien sûr, nous n’étions pas que trois au laboratoire. Une pensée toute particulière pour Sylvain Joubs, Éric et Arnaud, pour les longs moments à la pause café, mais j’y reviendrai un peu plus loin. À Sylvain Gram aussi pour ces nombreuses heures en pleurs devant la profonde incompréhension de la renormalisation. Mais, je ne pourrai pas parler de tout le monde, ce serait beaucoup trop long. Une chose est certaine, ce laboratoire est épanouissant, vivant, drôle, rempli de personnes toujours prêtes à discuter, de science et de tous les sujets. C’est un endroit parfait pour un jeune chercheur, bien qu’attention, il ne faut pas trop se faire d’illusion, le reste du monde ne tourne pas aussi rond. En tout cas, merci à toutes les personnes avec qui j’ai discuté et rencontré ici. Pendant ces trois ans, j’ai eu aussi la chance de pouvoir enseigner la physique à l’ENS, peut-être au grand désespoir des étudiants. C’est dire, je faisais parti des enseignants à la 3 4 préparation à l’agrégation, même si je l’ai jamais passée, mais passons. Cette expérience, assez inattendue, fut vraiment très enrichissante. Elle m’a permis de rencontrer plein de nouvelles personnes, de travailler avec Arnaud, Joubs, Marc et Henning, qui ont toujours été à l’écoute et plein de conseils. Pensée spéciale pour Arnaud pour avoir été un si bon enseignant durant mes années d’études à l’École, pour les longues discussions au café, pas toujours très éthique et responsable. Enseigner n’est pas si facile mais c’est très gratifiant d’aider et de voir, dans le regard de quelqu’un, qu’il a compris quelque chose en partie grâce à vous. Étant encore gamin dans ma tête, j’ai pu surtout, en étant en contact avec les jeunes de l’école, la relève des vieux, me faire de nouveaux amis, Chris, Charles, Grégoire et d’autres encore. Certains ne se rappellent plus que je les ai eus en cours, étant encore en gueule de bois de la veille au soir... Cette thèse va bientôt s’achever par la soutenance, dans quelques jours, et il naturel de remercier l’ensemble des membres de jury, en particulier Ivette Fuentes, Simone Speziale, Daniele Oriti et Daniel Terno qui viennent de loin pour m’écouter et en particulier ces deux derniers pour avoir patiemment relu la thèse et m’avoir fait part de leur remarques. Finalement, ce travail n’aurait pas pu voir le jour sans l’ensemble des personnes du Laboratoire de Physique, du département de physique, de l’ENS de Lyon et de l’École doctorale. Un big up particulier pour les secrétaires du laboratoire, Laurence, Fatiha, Laure et Nadine pour tout le travail qu’elles font ainsi qu’à Jérôme au département. Merci à tous. Mais voila, ce n’est qu’une partie de l’histoire qui vient d’être écrite. Rien n’aurait pu aussi bien se passer si je n’avais pas si bien été entouré. Et là c’est une longue histoire. Elle pourrait commencer il y a longtemps, mais on va remonter à six ans lors de mon arrivé dans cette petite institution qu’est l’ENS de Lyon. Il n’est pas possible de décrire l’ensemble des souvenirs que j’ai ici et l’ensemble des personnes que j’ai connues. Clément d’abord pour les innombrables heures passées à jouer à des jeux tous plus improbables les uns que les autres, les mois d’entraînement sur le jeu le plus dur du monde, les discussions farfelues à la coloc et ta magnifique œuvre d’art biologique dont je ne parlerai pas plus. Noé pour tous les moments passés à regarder animés et films au lieu de bosser, où j’ai appris que les films primés à Cannes n’étaient pas fait pour moi (ni pour Clément d’ailleurs), pour toutes les bouffes qu’on a faites et pour m’avoir fait découvrir la voile. Benjamin pour ce sens de l’humour si particulier, ton sens de la réplique, ces discussions dont on taira les sujets et la passion que l’on partage à trasher les gens. Enfin, je pense à bien d’autres personnes encore, Guilhem, Grimaud, Paul, Solène, Quentin... Un peu plus tard, j’ai découvert les joies des soirées, du foyer et de la vie étudiante de l’École. Sans conteste, le centre névralgique de toute cette (ma) vie se trouve au babyfoot. Impossible de compter les heures passées là, ce serait indécent d’ailleurs. Lilou, Chris, Jerem, Percy, Dédé, Lulu, Sami, Anthony, tellement de rire, tellement de conneries, tellement de rage d’avoir perdu mes deux BO 69 que le mur de (l’ancien, RIP) foyer s’en est souvenu. Pour toutes ses soirées en Festive, en ville, ou tranquille chez les uns ou les autres, pour ces vacances à Nice au bord de la piscine, à manger, boire et chanter 5 du Jean-Jacques. En soirée, le baby est rarement accessible, mais le bière-pong est là pour pimenter les choses entre deux chorées. En dehors de l’école, il y a naturellement le Ninka, lieu où nous allons, après une dure journée de labeur, se délecter d’un petit apéro pour souvent ensuite finir au resto. Avec Arnaud à refaire le monde, avec Joubs qui finit en train de dormir sur la table ou Monsieur Éric, toujours increvable avec son sens de l’humour trash, avec Jerem, Léo et Chris. Un endroit simple pour s’enjailler. Au fil du temps, surtout pendant la thèse où de nombreux amis sont partis suivre divers horizons, j’ai appris à connaître de nouvelles personnes. Lilou d’abord, autour d’une crêpe lors d’une soirée d’intégration où l’on a appris que l’on partageait les mêmes intérêts en science. C’était il n’y a pas si longtemps finalement, mais depuis on a rattrapé le temps, par de nombreuses conversations, du babyfoot, en soirée ou à distance, à Lyon, à Paris ou à Nice. Jérémy aussi, partenaire de baby, de SC2 ou de OW. On en a fait des choses depuis ces trois dernières années. Avec Léo naturellement, toujours comme moi prête à bitcher, nous nous sommes évadés de tellement d’endroits.
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