Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download High Contrast Measurements With A Bose Einstein Condensate Atom Interferometer PDF full book. Access full book title High Contrast Measurements With A Bose Einstein Condensate Atom Interferometer.
| Author | : Billy Ian Robertson |
| Publisher | : |
| Total Pages | : |
| Release | : 2016 |
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| Author | : Christopher Hugh Carson |
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| Total Pages | : 0 |
| Release | : 2015 |
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This thesis outlines the main experimental results of a Bose-Einstein condensate(BEC) interferometer and the finite temperature coherence of elongated BECs. Cold atom and BEC-based interferometers take advantage of the wave nature of atoms as they are cooled and can be used for precision measurements of fundamental physics, fundamental constants, rotations and gravitational gradients. The coherence properties of atomic matter-waves are of great interest, in particular phase coherence, which has played an important role in fundamental research involving BEC interferometry. When subject to high cloud aspect ratios, BECs become elongated and exhibited phase fluctuations, which can have a dramatic affect on the performance of matter-wave interferometers. A brief overview of the history and basic theory of Bose-Einstein condensates is presented as well as introducing the various studies and applications in metrology involving BECs. The theory of the techniques used to create a BEC, such as laser cooling, trapping and evaporation, are discussed along with the dynamics of BECs, matter-wave interference and phase fluctuations. The experimental chapters describe the various concepts, techniques and mechanisms used to experimentally observe matter-wave interference fringes. The interference fringes are a result of realising two BECs from a double-well potential, which is created using a combination of magnetic and optical potentials, and allowing them to expand and overlap. The main interferometry results are then discussed, this includes the observation of single-shot interference fringes with contrast ≥95%, which has a strong dependence on the detuning of the imaging beam. Also, a strong dependence on fringe contrast with the focal location of the camera is observed, which can now be clearly attributed to the Talbot effect. This is the first reported observation of the spatial Talbot effect of light interacting with period BEC fringes, revealing the drastic effect it can have on the interference signal. The major results regarding phase fluctuations in elongated condensates are presented. These include the existence of large regular period phase fluctuations, which should normally be of random phase and size. By dynamically changing the aspect ratio of the condensate during an experimental sequence, a controlled generation and removal of phase fluctuations in a Bose-Einstein condensate is observed, indicating a phase revival. The thesis concludes by considering potential improvements and future experiments, which could be used towards the experimental implementation of a BEC interferometer.
| Author | : Alan O. Jamison |
| Publisher | : |
| Total Pages | : 191 |
| Release | : 2014 |
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This dissertation describes the creation of the first matter-wave interferometer using ytterbium (Yb) atoms. Most of the experiments focus on a contrast interferometer geometry with a Bose-Einstein condensate (BEC) as source. The recoil frequency of the 174-Yb atom is measured with this interferometer. The recoil frequency of an atom is part of a set of precision measurements that together give a value for the fine structure constant. The experimental results of this dissertation lay the groundwork for a future sub part-per-billion (ppb) precision measurement of the Yb recoil frequency. The contrast interferometry technique is extended to substantially longer times scales than those achieved in previous experiments. A measurement at the ~10 parts-per-million level is made. Systematic effects and statistical scaling are studied and found to be compatible with the desired sub-ppb precision for a future measurement. Such a measurement requires a detailed theoretical study of possible systematic shifts to the measured value. A substantial portion of this dissertation consists of this analysis, carried out in sufficient generality as to guide future sub-ppb level measurements. In addition to a large number of possible systematic shifts due to well-understood physics, two more complex effects are identified and studied: Diffraction phases and atom-atom interactions.
| Author | : Tarik Berrada |
| Publisher | : Springer |
| Total Pages | : 244 |
| Release | : 2015-12-17 |
| Genre | : Science |
| ISBN | : 3319272330 |
This thesis demonstrates a full Mach–Zehnder interferometer with interacting Bose–Einstein condensates confined on an atom chip. It relies on the coherent manipulation of atoms trapped in a magnetic double-well potential, for which the author developed a novel type of beam splitter. Particle-wave duality enables the construction of interferometers for matter waves, which complement optical interferometers in precision measurement devices, both for technological applications and fundamental tests. This requires the development of atom-optics analogues to beam splitters, phase shifters and recombiners. Particle interactions in the Bose–Einstein condensate lead to a nonlinearity, absent in photon optics. This is exploited to generate a non-classical state with reduced atom-number fluctuations inside the interferometer. This state is then used to study the interaction-induced dephasing of the quantum superposition. The resulting coherence times are found to be a factor of three longer than expected for coherent states, highlighting the potential of entanglement as a resource for quantum-enhanced metrology.
| Author | : Daniel Doering |
| Publisher | : |
| Total Pages | : 280 |
| Release | : 2011 |
| Genre | : Atoms |
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Bose-Einstein condensates are coherent matter waves, produced by cooling gaseous atomic clouds to ultra-low temperatures. For applications in atom interferometry and precision measurements, Bose-condensed sources present an intriguing alternative to thermal atoms. Although the current sensitivity achievable with interferometers using coherent atoms is not comparable to thermal beam machines (mainly due to the lower flux), there are promising ways to utilise the potential of Bose-condensed sources for atom interferometry. Among those is the low momentum width of Bose-Einstein condensates, which can generally be well controlled and is advantageous for increased interferometric sensitivities by implementing large momentum transfer beam splitters. As part of this thesis, experimental and theoretical investigations are presented to investigate the potential of Bose-Einstein condensates for such applications. We shall present the quantum projection noise limited performance of a Ramsey interferometer operating on the atomic clock transition of a freely expanding cloud of Bose-condensed rubidium 87 atoms. The results include Ramsey fringes of high visibility, not measurably affected by atomic interaction-induced dephasing effects. The achievement and detection of the quantum projection noise limit rely critically on the precision and accuracy of both the imaging setup and the coupling scheme in the interferometric beam splitters. The stabilisation of the beam splitters via an optical Sagnac interferometer is the basis for the quantum projection noise limited performance of the interferometer presented. For an increase of bandwidth and flux in atom interferometric measurements, it is advantageous to use a continuous atomic beam. A truly continuous coherent atom source has not been realised to date, and we present results on a pumping mechanism in this thesis, as a decisive step towards a continuous atom laser. By the investigation of different momentum resonances, we find that the pumping scheme relies on a Raman superradiance-like process. Finally, the thesis demonstrates two interaction measurements in rubidium. The strong mean field interactions due to the high densities in Bose-Einstein condensates are used to probe the potential of a rubidium 87 condensate with an atom laser. The measurement allows a determination of the scattering length between the two atomic states involved. In addition to this two-body scattering scheme, we present a measurement of three-body loss coefficients, extracted from loss curves in rubidium 85 Bose-Einstein condensates. The measurement provides new upper bounds on the three-body loss coefficients at the scattering lengths considered.
| Author | : Rudra Prasad Kafle |
| Publisher | : |
| Total Pages | : 490 |
| Release | : 2012 |
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Abstract: Atom interferometers and gyroscopes are highly sensitive atom-optical devices which are capable to measure inertial, gravitational, electric, and magnetic fields and to sense rotations. Theoretically, the signal-to-noise ratio of atomic gyroscopes is about a hundred billion times more than that of their optical counterparts for the same particle flux and the enclosed area. Ultra cold atoms from a Bose-Einstein condensate (BEC) can easily be controlled and coherently manipulated on small chips by laser pulses. Atom-optical devices will therefore play a significant role in fundamental research, precision measurements, and navigation systems. In BEC-based atom interferometers, a BEC in a trap is split by using laser pulses, the split clouds are allowed to evolve, they are reflected, and then recombined by laser pulses to observe interference. The split clouds accumulate spatial phase because of the trap and the nonlinearity caused by atom-atom interactions. A velocity mismatch due to reflection laser pulses also introduces a phase gradient across each cloud. These factors contribute to spatial relative phase between the clouds at recombination, causing the loss of contrast of the interference fringes. The main objective of this dissertation is to study the dynamics of a split condensate in atom Michelson interferometers, investigate the effect of trap frequencies, nonlinearity, and the velocity mismatch on the contrast, and to obtain the best theoretical limit of performance in terms of the experimental parameters: trap frequencies, number of atoms, and the velocity imparted to the clouds by the splitting laser pulses.
| Author | : Julia Pahl |
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| Total Pages | : 0 |
| Release | : 2023* |
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Englische Version: 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.
| Author | : Paul Anthony Altin |
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| Total Pages | : 342 |
| Release | : 2012 |
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In recent years, atom interferometry has become established as an indispensable tool in both fundamental and applied physics. With present state-of-the-art devices based on thermal atoms reaching limits imposed by the momentum spread of the initial atomic wavepacket, it seems natural to ask whether colder sources such as Bose-Einstein condensates may prove beneficial in advancing the precision of interferometric measurements. The thesis at hand aims to inform this question, specifically by examining the role played by atomic interactions in interferometers based on Bose-condensed atoms. Interactions can have both advantageous and deleterious consequences in the context of atom interferometry. They provide a means to control the momentum width of the condensate, and facilitate the generation of nonclassical squeezed states which may enhance the phase sensitivity beyond the shot noise limit. Conversely, the condensate self-interaction causes mean-field shifts, multimode excitations and phase diffusion which can erode both the precision and the accuracy of an interferometric measurement. The question of when and in which systems the detrimental effects of interactions outweigh the advantages of using Bose-Einstein condensates is an important one, and warrants investigation. This thesis presents experimental studies into the role of interactions in both internal- and external-state atom interferometers. As a foundation for these investigations, we describe the design and construction of an apparatus for creating Bose-Einstein condensates of the two stable rubidium isotopes in an optical trap. By sympathetic cooling with a rubidium-87 reservoir, we are able to produce condensates of rubidium-85 in which the interactions may be adjusted by means of a magnetic Feshbach resonance. The tunability afforded by the Feshbach resonance is used to study inelastic losses in ultracold rubidium-85 clouds, as well as the effect of interactions on condensate stability and on the ground state of dual-species mixtures. In particular, we offer new experimental data on the dynamics of collapsing condensates with attractive interactions, over which some controversy has existed since the first experiments more than a decade ago. Good agreement is found between the measured collapse times and a simple mean-field model. Proceeding to interferometry, we present results from Ramsey interferometers operating on the clock transition of rubidium-87 Bose-Einstein condensates. In free-space operation with Raman beamsplitters, we demonstrate projection-noise-limited performance, an important prerequisite for the realisation of squeezing-enhanced sensitivity. Using large condensates of up to 106 atoms and microwave coupling, we study the effect of interactions on the Ramsey fringe contrast. The dominant source of decoherence is found to be spatial dynamics driven by the difference in interparticle interaction strengths, which are analysed using the spin-echo technique and numerical simulations of the Gross-Pitaevskii equation. Finally, we turn our attention to external-state interferometry, implementing a Mach-Zehnder gravimeter using Bragg transitions in a freely falling rubidium-87 condensate. Large-momentum-transfer beamsplitters composed of higher-order Bragg diffraction and Bloch oscillations are used to increase the accumulated phase and thus the sensitivity of the interferometer. The role of interactions in this system is examined, and we canvass methods for achieving further increases in sensitivity. -- provided by Candidate.
| Author | : S. Martellucci |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 322 |
| Release | : 2007-05-08 |
| Genre | : Technology & Engineering |
| ISBN | : 0306471035 |
Proceedings of the International School of Quantum Electronics 27th course on Bose Einstein Condensates and Atom Lasers, October 19-24, 1999, Erice, Italy. Since the experimental demonstration of Bose Einstein Condensation in dilute atomic gases there has been an explosion of interest in the properties of this novel macroscopic quantum system. The book covers the methods used to produce these new samples of coherent atoms, their manipulation and the study of their properties. Emphasis is given to the anticipated development of new types of sources, which more and more resemble traditional types of lasers. Because of recent new applications and increasing demand for lasers, sensors and associated instrumentation, the chapters also cover current developments in the basic techniques, materials and applications in the field of the generation of coherent atoms.
| Author | : Boris Décamps |
| Publisher | : |
| Total Pages | : 304 |
| Release | : 2016 |
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This thesis's first part describes the realization of three experiments using an atom interferometer operated with a lithium supersonic beam. The second part presents the development of a new BEC interferometer designed to test matter neutrality. The first three experiments rely on the interactions of lithium atom with different electromagnetic fields. A time dependent electric potential difference was used to produce phase modulation of both interferometer arms at different frequencies, leading to homodyne and heterodyne detection of atom waves. A geometric phase of light (the Pancharatnam phase) was successfully transferred to our interferometer signal during Bragg diffraction, enlarging the atom optics toolbox for phase control in an atom interferometer. Finally, a focused laser beam was used to measure accurately the value of one lithium tune-out wavelength (for which its dynamic polarizability is zero). The new BEC interferometer was designed to measure a possible non-zero electric charge of rubidium isotopes 85Rb and 87Rb with enhanced sensitivity to the electron-proton charge difference and neutron neutrality. This setup relies on a large spatial separation between the two interferometer arms in a fountain configuration aiming at a cycle time of 5s. These features required particular design work both on the atomic source (atom-chip) and the diffraction process (Large Momentum Transfer). The technical choices on the vacuum chambers, laser system and magnetic sources are described and characterized. Finally, the up-to-date cold-atom source performances is shown and compared to our expectations.
