A prototype apparatus for very long baseline atom interferometry

verfasst von: Dorothee Tell
betreut von: Ernst Maria Rasel
Abstract: The sensitivity of interferometers based on freely falling atoms depends on the time atoms spend in the interferometer, i. e. the interrogation time. In a terrestrial experiment, this time is limited by the available free fall baseline. The Very Long Baseline Atom Interferometry (VLBAI) facility in Hannover tackles this by employing a 10.5m long vacuum tube, allowing for a total interferometry time of 2.55 s for atoms launched from its bottom source chamber. One of the most prominent applications of light pulse atom interferometers are measurements of accelerations. Next to the available free fall time, many other factors influence and limit the accessible sensitivity of the atom interferometer to measure the desired inertial effects. Therefore, accurate engineering of the atom source and interferometry setup are necessary to make use of the device’s long baseline. This work aims to describe the setup and initial commissioning of this source, presenting a system ready for operation in the VLBAI apparatus. A Bose-Einstein condensate of rubidium is created in an all-optical sequence using an optical dipole trap, targeting large atom numbers and short cycle times. The focus of this work will be on two key experiments conducted with the cold atoms: The characterization of Bragg atom optics processes required to perform atom interferometry and a method to reduce the expansion velocity of a cold rubidium ensemble in three dimensions in order to allow for a high contrast even after long free fall times. The Bragg beam splitter experiments are performed as proof-of-principle measurements on a short baseline. A detailed analysis of experimental and simulated parameters allows us to use this as a basis for Bragg interferometry compatible with the requirements of the VLBAI facility. In order to realise a reduction of expansion velocity in a trapped matter-wave lens, the parameter space for 3D time-averaged optical dipole traps is explored, leading to an improved quantitative understanding. The method is used to reduce the 3D temperature of a cold rubidium ensemble by more than a factor of two while losing less atoms than an equivalent evaporative cooling sequence. The challenges of time-averaged optical dipole traps especially in three dimensions are discussed in detail and alternative approaches to achieve effective sub-nanokelvin temperatures useful for atom interferometry are discussed.
Organisationseinheit(en): Institut für Quantenoptik
QUEST Leibniz Forschungsschule
Typ: Dissertation
Anzahl der Seiten: 105
Publikationsdatum: 2024
Publikationsstatus: Veröffentlicht
Elektronische Version(en): https://doi.org/10.15488/17346 (Zugang: Offen)
: Details im Forschungsportal „Research@Leibniz University“

BibTeX

@phdthesis{79c7775719fd427c8546018bde3325f4,
title = "A prototype apparatus for very long baseline atom interferometry",
abstract = "The sensitivity of interferometers based on freely falling atoms depends on the time atoms spend in the interferometer, i. e. the interrogation time. In a terrestrial experiment, this time is limited by the available free fall baseline. The Very Long Baseline Atom Interferometry (VLBAI) facility in Hannover tackles this by employing a 10.5m long vacuum tube, allowing for a total interferometry time of 2.55 s for atoms launched from its bottom source chamber. One of the most prominent applications of light pulse atom interferometers are measurements of accelerations. Next to the available free fall time, many other factors influence and limit the accessible sensitivity of the atom interferometer to measure the desired inertial effects. Therefore, accurate engineering of the atom source and interferometry setup are necessary to make use of the device{\textquoteright}s long baseline. This work aims to describe the setup and initial commissioning of this source, presenting a system ready for operation in the VLBAI apparatus. A Bose-Einstein condensate of rubidium is created in an all-optical sequence using an optical dipole trap, targeting large atom numbers and short cycle times. The focus of this work will be on two key experiments conducted with the cold atoms: The characterization of Bragg atom optics processes required to perform atom interferometry and a method to reduce the expansion velocity of a cold rubidium ensemble in three dimensions in order to allow for a high contrast even after long free fall times. The Bragg beam splitter experiments are performed as proof-of-principle measurements on a short baseline. A detailed analysis of experimental and simulated parameters allows us to use this as a basis for Bragg interferometry compatible with the requirements of the VLBAI facility. In order to realise a reduction of expansion velocity in a trapped matter-wave lens, the parameter space for 3D time-averaged optical dipole traps is explored, leading to an improved quantitative understanding. The method is used to reduce the 3D temperature of a cold rubidium ensemble by more than a factor of two while losing less atoms than an equivalent evaporative cooling sequence. The challenges of time-averaged optical dipole traps especially in three dimensions are discussed in detail and alternative approaches to achieve effective sub-nanokelvin temperatures useful for atom interferometry are discussed.",
author = "Dorothee Tell",
year = "2024",
doi = "10.15488/17346",
language = "English",
publisher = "Leibniz Universit{\"a}t Hannover",
school = "Leibniz University Hannover",
}