La physique moderne repose sur deux théories fondamentales distinctes, la relativité générale et la mécanique quantique. Toutes les deux décrivent d’une part les phénomènes macroscopiques et cosmologiques tels que les ondes gravitationnelles et les trous noirs et d’autre part les phénomènes microscopiques comme la superfluidité ou le spin des particules. L’unification de ces deux théories reste, jusqu’à présent, un problème non résolu. Il est intéressant de noter que les différentes théories de gravité quantique prédisent une violation des principes de la relativité générale à différents niveaux.Il est donc hautement intéressant de détecter les violations de ces principes et de déterminer à quel niveau elles se produisent.De récentes propositions pour effectuer des tests du principe d’ équivalence d’Einstein suggèrent une amélioration spectaculaire des performances en utilisant des capteurs atomiques `a ondes de matière.Dans ce contexte, il est nécessaire de concevoir des états d’entrée de l’interferomètre avec des conditions initiales bien définies. Un test de pointe de l’universalité de la chute libre (Universality of FreeFall en anglais (UFF) ) nécessiterait, par exemple,un contrôle des positions et des vitesses avec une précision de l’ordre de 1 μm et 1 μm.s⁻¹ , respectivement.De plus, les systématiques liées à la taille du paquet d’ondes limitent le taux d’expansion maximum possible à 100 μm.s⁻¹. La création initiale des états d’entrée de l’interféromètre doit être assez rapide,de l’ordre de quelques centaines de ms au maximum,pour que le temps de cycle de l’expérience soit pertinent d’un point de vue métrologique. Dans cette thèse j’ai développé des séquences optimisées s’appuyant sur l’excitation du centre de masse et de la taille d’un ou plusieurs ensembles d’atomes refroidis ainsi que dégénérés. Certaines séquences proposé dans cette thèse ont déjà été implémenté dans des expériences augmentant de manière significative le contrôle des ensembles atomiques. / Modern physics relies on two distinct fundamental theories, General Relativity and Quantum Mechanics. Both describe on one hand macroscopic and cosmological phenomena such as gravitational waves and black holes and on the other hand microscopic phenomena as superfluidity or the spin of particles. The unification of these two theories remains, so far, an unsolved problem. Interestingly, candidate Quantum Gravity theories predict a violation of the principles of General Relativity at different levels. It is, therefore, of a timely interest to detect violations of these principles and determine at which level they occur. Recent proposals to perform Einstein Equivalence Principle tests suggest a dramatic performance improvement using matter-wave atomic sensors. In this context, the design of the input states with well defined initial conditions is required. A state-of-the-art test of the universality of free fall (UFF) would, for example, require a control of positions and velocities at the level of 1 µm and 1 µm.s⁻¹, respectively. Moreover, sizerelated systematics constrain the maximum expansion rate possible to the 100 µm.s⁻¹level. This initial engineering of the input states has to be quite fast, of the order of few hundred ms at maximum, for the experiment’s duty cycle to be metrologically-relevant. In this thesis I developed optimized sequences based on the excitation of the center of mass and the size excitation of one or two cooled atomic sample as well as degenerated gases. Some sequences proposed in this thesis have already been implemented in experiments and significantly increase the control of atomic ensembles.

Ce travail de thèse décrit la première observation directe de particules associées à la déplétion quantique et de premières mesures dans l’espace des impulsions d’un superfluide sur réseau. Ces observations ont été réalisées à partir d'un gaz dégénéré d'Hélium métastable sur un tout nouvel dispositif expérimental, dont la construction a été terminée au cours de cette thèse. Permise par l’Hélium métastable, notre détection électronique sensible à l’atome unique donne accès à la distribution tridimensionnelle dans l’espace des impulsions k.Nous avons d’abord développé une approche hybride pour la réalisation de condensats de Bose-Einstein, qui utilise un piège magnétique comme réservoir du piège dipolaire. Cette méthode permet la production rapide de condensats de Bose-Einstein toutes les 6 secondes sur notre expérience. Nous avons alors pu observer, pour la première fois, les particules excitées hors du condensat à cause des interactions (déplétion quantique). En particulier, nous avons observé la loi de puissance en 1/k4 dans la distribution pour de larges impulsions k, comme attendue dans la théorie de Bogoliubov. Enfin nous avons étudié les distributions de superfluide sur réseau. Il s’agit d’une première mesure de la distribution en impulsion dans un réseau comme le démontre les simulations numériques (Monte-Carlo quantique). Les effets de températures sur les distributions mesurées sont extrêmement visibles, ce qui ouvre la voie à une thermométrie des superfluides sur réseau. / In this thesis, we report the first observation of the particles associated with the quantum depletion and the first measurements of the momentum distribution of correlated superfluid lattice bosons. We performed the experiment with a degenerate metastable Helium gas with a novel experimental setup. Making possible with metastable Helium, our electronic detection allows single-atom detection in momentum space k.Firsly, we have demonstrated a new approach to Bose-Einstein condensation of metastable Helium using a hybrid trap, consisting of a magnetic quadrupole and a crossed optical dipole trap. It results in production of a condensate every 6 seconds. Then we observed the excited particles out of the condensate wavefunction due to presence of the interactions (quantum depletion). We observe atom distributions decaying at large momenta k with the 1/k4 power-law predicted by Bogoliubov theory. Furthermore we studied the three-dimensional far field distribution of correlated superfluid lattice bosons. The momentum distributions of the trapped atoms calculated with an ab-initio Monte-Carlo Worm algorithm for the experimental parameters are in excellent agreement with the measured distributions. The finite temperature effect is not negligible, paving the way for a precise thermometry.

My dissertation treats the physics of ultracold gases, in particular of Bose-Einstein condensates with long-ranged interactions induced by admixing a small fraction of a Rydberg state to the atomic ground state. The resulting interaction leads to the emergence of supersolid states and to the self-trapping of a Bose-Einstein condensate.

Atominterferometrie (AI) auf Basis von Lichtpulsen ist ein wichtiges Werkzeug der Präzisionsmesstechnik in Bereichen der inertialen Sensorik oder Fundamentalphysik geworden. Vor allem in Kombination mit ultrakalten, atomaren Quellen, sowie der Verwendung im schwerelosen Raum, werden hohe Sensitivitäten erwartet, die Verletzungen des schwachen Äquivalenzprinzips nachweisen können. QUANTUS-2 ist ein mobiles Atominterferometer, das am ZARM Fallturm in Bremen operiert. Durch seine Atomchip-basierte atomare Rubidiumquelle mit hoher Flussdichte dient es als Vorreiterexperiment für zukünftige Weltraummissionen, bei denen Schlüsseltechnologien wie die Erzeugung von Bose-Einstein Kondensaten (BECs), Delta-Kick Kollimation oder Anwendung verschiedener AI-Geometrien auf sekundenlangen Zeitskalen untersucht werden. Im Rahmen dieser Arbeit wurde ein Kalium-Diodenlasersystem aufgebaut, um die Funktionalität auf Zwei-Spezies Nutzung zu erweitern. Basierend auf dem Design des Rubidium-Diodenlasersystem mit mikrointegrierten Laserdiodenmodulen und kompakter Elektronik, konnte es erfolgreich qualifiziert werden. In einem Machbarkeitsbeweis wurde eine magneto-optische Falle mit Kalium generiert, die die Fähigkeit des Lasersystems zum Fangen von Atomen demonstriert. Mit Rubidium wurden offene Ramsey-Interferometer und Mach-Zehnder Interferometer (MZIs) am Boden und in über 155 Abwürfen untersucht. Die Kombination von unterschiedlich stark Delta-Kick kollimierten BECs und AI in Schwerelosigkeit eröffnete eine neue Methode zur Bestimmung der magnetischen Linsendauer zur optimalen Kollimierung. Asymmetrische MZIs mit Interferometerzeiten von 2T > 1s konnten erfolgreich demonstriert werden. Mit gravimetrischen Untersuchungen am Boden auf Basis von MZIs und einer zusätzlichen Methode der Atomlevitation wurde die lokale Gravitationsbeschleunigung g ermittelt. Die untersuchten Schlüsseltechnologien sind fundamentale Notwendigkeiten, um den Weg für zukünftige Weltraummissionen aufzubereiten. / Light-pulse atom interferometry (AI) is an important tool for high precision measurements in the fields of inertial sensing or fundamental physics. Especially in combination with ultra-cold atomic sources and operation in microgravity, high sensitivities are expected that are necessary for the search for violations of the weak equivalence principle. QUANTUS-2 is a mobile atom interferometer operating at the ZARM drop tower in Bremen. With its high-flux, atom chip-based atomic rubidium source, it serves as a pathfinder for future space missions, examining key technologies like the generation of Bose-Einstein condensates (BECs), implementation of delta-kick collimation or application of various AI geometries. In this thesis, a potassium diode laser system has been built to complete the preordained functionality of dual-species operation. Based on the design of the rubidium laser system with micro-integrated laser diode modules and compact electronics, it successfully passed the qualification tests. In a proof of principle measurement, a potassium magneto-optical trap could be generated to prove the system’s capability of trapping atoms. With rubidium, open Ramsey type interferometers and Mach-Zehnder interferometers (MZIs) were examined on ground and in over 155 drops in microgravity. The combination of variably delta-kicked collimated BECs and AI in microgravity revealed a new technique to determine the magnetic lens duration for optimal collimation. Asymmetric MZIs with interferometry times of 2T > 1s have successfully been demonstrated. Gravimetric examinations on ground with MZIs and by an additional levitation technique have been performed to determine the local gravitational acceleration g. The examined key technologies are fundamental necessities that have to be considered to pave the way for future space missions.

No description available.

Atoms in optical lattices are promising candidates to implement quantum information processing. Their behaviour is well understood on a microscopic level, they exhibit excellent coherence properties, and they can be easily manipulated using external fields. In very deep optical lattices, each atom is restricted to a single lattice site and can be used as a qubit. If the lattice is shallow enough such that the atoms can move, their properties can be used to simulate certain condensed matter phenomena such as superconductivity. In this thesis, we show how technical problems of optical lattices such as restricted decoherence times, or fundamental shortcomings such as the lack of phonons or strong spin interactions, can be overcome by using current or near-future experimental techniques. We introduce a scheme that makes it possible to simulate model Hamiltonians known from high-temperature superconductivity. For this purpose, previous simulation schemes to realise the spin interaction terms are extended. We especially overcome the condition of a filling factor of exactly one, which otherwise would restrict the phase of the simulated system to a Mott-insulator. This scheme makes a large range of parameters accessible, which is difficult to cover with a condensed matter setup. We also investigate the properties of optical lattices submerged into a Bose-Einstein condensate (BEC). A weak-coupling expansion in the BEC-impurity interaction strength is used to derive a model that describes the lattice atoms in terms of polarons, i.e.~atoms dressed by Bogoliubov phonons. This is analogous to the description of electrons in solids, and we observe similar effects such as a crossover from coherent to incoherent transport for increasing temperatures. Moreover, the condensate mediates an attractive off-site interaction, which leads to macroscopic clusters at experimentally realistic parameters. Since the atoms in the lattice can also be used as a quantum register with the BEC mediating a two-qubit gate, we derive a quantum master equation to examine the coherence properties of the atomic qubits. We show that the system exhibits sub- and superdecoherence and that a fast implementation of the two-qubit gate competes with dephasing. Finally, we show how to realise the encoding of qubits in a decoherence-free subspace (DFS) using optical lattices. We develop methods for implementing robust gate operations on qubits encoded in a DFS exploiting collisional interactions between the atoms. We also give a detailed analysis of the performance and stability of the gate operations and show that a robust implementation of quantum repeaters can be achieved using our setup. We compare the robust repeater scheme to one that makes use of conventional qubits only, and show the conditions under which one outperforms the other.

CALPHAD (CALculation of PHAse Diagrams) denotes the methodology used to assess thermodynamic data based on experiments as well as on first principles calculations. Essential for this method is the coupling of phase diagram and thermodynamic properties. It has been widely and successfully applied for decades in the field of materials science and engineering. Nevertheless, some shortcomings of the existing thermodynamic databases call for updated descriptions with improved thermodynamic modeling from unary, binary to ternary and higher-order systems. This thesis attempts to pioneer the development of a new generation of CALPHAD databases taking C-Co-Cr alloys with subsystems, unaries and binaries, as example. The present modeling and assessment work not only validate the new models applied in the development of the next, the 3rd, generation database, but also result in improved descriptions in a wider temperature range.In this 3rd generation database, thermodynamic descriptions are valid from 0 K up to high temperatures above liquidus. The Einstein model, rather than the polynomial basis functions used in the previous 2nd generation database, is applied to model the harmonic lattice vibration contribution to the heat capacity of condensed phases at low temperatures. In addition, terms describing the electronic excitations and anharmonic lattice vibrations, as well as the magnetic contribution, are added. A generalized two-state model is employed for the liquid phase to describe the gradual transition from the liquid to amorphous state. A revised magnetic model is adopted accounting for both the ferromagnetic and anti-ferromagnetic states explicitly. A newly suggested method to avoid violating the 3rd law of thermodynamics is adopted for e.g. stoichiometric phases. However, there is still some concern as Nernst’s heat theorem which states that 𝑑𝐶𝑃/𝑑𝑇 is zero at 0 K is not obeyed. All solution phases are modelled within the framework of the compound energy formalism (CEF).The task of the thesis is to construct an updated self-consistent thermodynamic description of the C-Co-Cr system for the third generation CALPHAD databases. The improvement is significant from a modeling point of view when compared to the second generation database. A good agreement between the calculated thermodynamic properties and the experimental data is achieved. The reliability of the extrapolations of unary and binary systems into higher order systems is demonstrated. / <p>QC 20170529</p>

Using Gillian Beer's suggestion that literature and science 'share the moment's discourse' (Open Fields, 1996), this thesis explores the ideas associated with Albert Einstein's three revolutionary 1905 papers, examining the ways in which similar concepts appeared across disciplines during the early part of the twentieth century, and focusing in particular on their manifestation within the literary works of Virginia Woolf and D. H. Lawrence. The study seeks to distinguish between instances of direct influence and a shared contemporary discourse, arguing that the analysis of both is essential to studies within the field of literature and science. Part I focuses on concepts of duality and complementarity, considering Max Planck's introduction of the quantum, Einstein's development of light quanta, Louis de Broglie's wave-particle duality and Niels Bohr's principle of complementarity. It analyses other contemporary discussions of duality and complementarity, and explores Virginia Woolf's attempts to simultaneously express both sides of dualistic models, suggesting that Woolf is a complementary writer. Part II focuses on Einstein's theories of relativity, exploring D. H. Lawrence's adoption thereof in Fantasia of the Unconscious (1922), in particular his claim that 'we are in sad need of a theory of human relativity'. It argues that this proposed theory is directly relevant to Lawrence's fictional works, both those that precede Fantasia and those that follow it. It also analyses the impact on Lawrence of contemporary ideas of relativism, especially those of William James as expressed in Pragmatism (1907). Part III explores the ways in which both Woolf and Lawrence write about individuals within crowds. It considers the possible links between such scenes and Einstein's paper on Brownian motion as well as contemporary studies of crowd psychology. It suggests that individual characters within modernist works can be considered as similar to the individual particles suspended in a mass which exhibit Brownian motion.

Approved for public release; distribution in unlimited. / This thesis uses an agent-based simulation model named EINSTein to perform an exploratory study on the feasibility of using Littoral Combat Ships (LCSs) to augment or replace the current defenses of Expeditionary Strike Groups (ESG). Specifically, LCS's ability to help defend an ESGs in an anti-access scenario against a high-density small boat attack is simulated. Numbers of CRUDES (CRUiser, DEStroyer, Frigate) ships are removed and LCSs are added to the ESG force structure in varying amounts to identify force mixes that minimize ship losses. In addition, this thesis explores various conceptual capabilities that might be given to LCS. For example, helicopter/Unmanned Combat Aerial Vehicles (helo/UCAVs), Stealth technology, close-in high volume firepower, and 50+ knot sprint capability. Using graphical analysis, analysis of variance, and large-sample comparison tests we find that being able to control aircraft is the most influential factor for minimizing ship losses. Stealth technology is another significant factor, and the combination of the two is highly effective in reducing ship losses. Close-in high volume firepower is effective only when interacting with helo/UCAVs or stealth. 50+ knot sprint capability is potentially detrimental in this scenario. An effective total sum of CRUDES ships and LCS is between five and seven platforms. / http://hdl.handle.net/10945/855 / Lieutenant, United States Navy

Dans cette thèse des actions conformes de cohomogénéité un sur l'univers d'Einstein tridimensionel sont classifiées. Notre stratégie est d'établir dans un premier temps quel peut être le groupe de transformations conformes impliqué, à conjugaison près. Nous décrivons aussi la topologie et la nature causale des orbites d'une telle action. / In this thesis, the conformal actions of cohomogeneity one on the three-dimensional Einstein universe are classified. Our strategy in this study is to determine the representation of the acting group in the group of conformal transformations of Einstein universe up to conjugacy. Also, we describe the topology and the causal character of the orbits induced by cohomogeneity one actions in Einstein universe.