A cold atom experiment can be used to simulate analogous solid-state systems. This provides the bene�t of having a high degree of control over the system parameters and allowing direct detection methods. Disordered transport is one example of where such a system has much to o�er. This thesis concerns the development of a Bose-Fermi mixture experiment for study of two-dimensional optical lattice systems. To achieve single site resolution of the lattice, the experiment makes use of a double microscope set-up. One microscope provides imaging and the second is used to image a spatial light modulator onto the atomic plane. This provides an extremely versatile potential landscape for a trapped cloud. This thesis presents an overview of the set-up of the experiment including progress towards condensation. Particular focus is given to the design and characterisation of the vacuum system and the combined double microscope and spatial light modulator system. The vacuum system design requires a narrow magneto-optical trapping chamber. A novel epoxy sealing technique has been developed, allowing construction of a chamber of just 36mm thickness whilst maintaining high optical access. To provide illumination for the spatial light modulator a technique for homogenising the output of multi-mode �bre has been developed.
A cold atom experiment can be used to simulate analogous solid-state systems. This provides the bene�t of having a high degree of control over the system parameters and allowing direct detection methods. Disordered transport is one example of where such a system has much to o�er. This thesis concerns the development of a Bose-Fermi mixture experiment for study of two-dimensional optical lattice systems. To achieve single site resolution of the lattice, the experiment makes use of a double microscope set-up. One microscope provides imaging and the second is used to image a spatial light modulator onto the atomic plane. This provides an extremely versatile potential landscape for a trapped cloud. This thesis presents an overview of the set-up of the experiment including progress towards condensation. Particular focus is given to the design and characterisation of the vacuum system and the combined double microscope and spatial light modulator system. The vacuum system design requires a narrow magneto-optical trapping chamber. A novel epoxy sealing technique has been developed, allowing construction of a chamber of just 36mm thickness whilst maintaining high optical access. To provide illumination for the spatial light modulator a technique for homogenising the output of multi-mode �bre has been developed.
This thesis describes the progress achieved towards two goals. One is the construction of a compact magneto-optical trap (MOT) apparatus, used both as a standalone undergraduate laboratory experiment and as part of a public engagement demonstration of cold atom physics. The setup, which utilises a dichroic atomic vapour laser lock (DAVLL) system plus homemade sideband generation electronics, is capable of trapping and cooling up to 8x10⁷ ⁸⁵Rb atoms in a standard six-beam laser cooling scheme. The second goal is the loading of an ultracold ensemble of ⁸⁷Rb atoms into novel optical trap geometries using a phase-only liquid crystal spatial light modulator (LC SLM) for applications to atomtronics and quantum simulation. Details of a double vacuum chamber apparatus, designed to produce the first Bose-Einstein condensates (BECs) at St Andrews, are provided. The setup incorporates a hybrid trap evaporative cooling scheme towards quantum degeneracy and reliably produces BECs of 1.9 10⁵ ⁸⁷Rb atoms. Two computational techniques, developed during the course of this project, are presented with the aim of creating flexible, smooth holographic optical traps. The first method illuminates a single SLM with overlapped, co-propagating light beams of different wavelengths to create a composite optical pattern for atom manipulation. The second uses conjugate gradient minimisation to create exceptionally high fidelity light patterns in both amplitude and phase for light in the output plane. These techniques, combined with the implementation of a light sheet into the experimental setup, are used to trap atoms in both a ring profile and in a set of narrow waveguides connected with a tunnelling barrier.
This thesis presents work towards the realisation of dark solitons in a two-dimensional Bose-Einstein condensate. \nThe technical redesign of two sets of coils, necessary for magnetic trapping of the atom cloud in order to \ncreate a condensate, is reported. Two different types of coil technology are presented, discussed, and used. \nThe fabrication of the coils is described, and each set of coils is characterised. Both sets of coils have been installed on the main experiment and are fully operational. \nA key aspect of this thesis is the development of an optical system capable of achieving resolution on the micrometer scale, which can be used for manipulation of a two-dimensional condensate by the method of phase imprinting. The optical system demagnifes the image on a spatial light modulator and focuses the image on the atom plane. Characterisation of the resolution of the optical system shows that a resolution of 3 µm is achieved. The optical system has successfully been implemented on the main experiment and has been used to manipulate the condensate. \nA two-dimensional BEC of \\(^{87}\\)Rb with 31000 atoms and a temperature of 88 nK is realised in a dipole trap of frequencies ω\\(_x\\) = 2π∙5.8 Hz, ω\\(_y\\)= 2π∙19.1 Hz, ω\\(_z\\)= 2π∙269.4 Hz, with gravity being in the z-direction. The method of phase imprinting is used to create the first observed soliton in a 2D BEC. Preliminary analysis of the soliton velocity, width and curvature is presented.
Since the experimental achievement of Bose-Einstein condensation (BEC) in dilute gases, ultra-cold atom systems have proven to be an unparalleled test bed for condensed matter phenomena. With this in mind, our laboratory set out to build an apparatus for the study of the effects of disorder on condensed matter phase transitions using a BEC loaded into one, two, and three-dimensional lattices. My thesis is divided into two main sections. In the first section I describe in detail the design and construction of our apparatus. Our system is designed to form <super>87<\super>Rb condensates of approximately 10<super>5<\super> atoms. We have three possible experimental science chambers. 1. One can perform 1D lattice experiments in the chamber where the condensate is formed. There is a mirror located in vacuum, which is suitable for this purpose. 2. In a glass chamber one can do 1D, 2D, or 3D lattice experiments. Atoms are loaded into a dipole trap (optical tweezer) prior to condensation and transported approximately 20 cm to the glass cell where optical evaporation is performed to form a BEC. 3. One can transfer, using the same techniques as (2), to a chamber with a multi-channel plate detector for Rydberg atom experiments. The experimental results described in my thesis pertain to situation (1). However, I describe some details of (2) in the construction section. The first experiment presented in my thesis demonstrates the effect of disorder on the time-dependent dynamics of lattice systems. We observe that a small perturbation produces a dramatic change in the adiabaticity criteria for loading a BEC into one-dimensional optical lattice. I conclude with experiments that we expect to perform on this apparatus.
This thesis describes and characterizes a setup to conduct experiments combining the fields of cold atoms and nanophotonics. Furthermore, a series of numerical simulations is employed to deepen of atom transport under experimentally realistic conditions. The study of cold atoms is usually fundamental in nature and a very clean approach to investigate the laws of physics. High purity samples of atoms are cooled down to millikelvins or microkelvins. The potential landscape for the atoms can be carefully controlled using lasers and/or magnetic fields. Since the atoms' responses to electric, magnetic or electromagnetic fields are known with very high fidelity, any deviations to the state the atoms are prepared in can be precisely measured. Nanophotonics is the study of light close to or beyond the diffraction limit. In this region the field-like nature of light starts to play a role. By confining light in sub-wavelength-sized structures, high peak intensities can be achieved, giving rise to exciting non-linear optics phenomena. The strong field gradient that can be created allows, for instance, precise spectroscopy measurements, phase-sensitive sub-wavelength microscopy, as well as producing highly receptive sensing devices. Combining cold atoms and nanophotonics creates strong synergy effects. It gives access to strong coupling of light and matter. The scalability of nanophotonics now extends to atomic physics. Atoms can be trapped, coupled and manipulated at very small length scales, and in large numbers. Moreover, the potential landscape for atoms is highly customizable. The rubidium isotope 87 is used in this setup. A cloud of rubidium atoms is gathered and cooled in a two dimensional magneto-optical trap (MOT). Since the atoms are only cooled in two dimensions, they are free to escape in the third dimension and load a following three dimensional MOT. The atoms are now cooled further, compressed and loaded into an optical dipole trap. This dipole trap transports the atoms close to a sample inside the vacuum chamber. A moving optical lattice, or optical conveyor belt, brings the atoms then close to the sample surface. Now experiments can be conducted, studying the interaction of cold atoms and strongly confined light. The atom transport down to the sample surface shows some unexpected behaviour: the atoms seem to spread through the optical lattice during transport. A combination of microscopic and macroscopic numerical simulations, including genetic algorithms, are used to deepen our understanding of the underlying physics. This also allows us to get access to experimental variables that cannot be directly obtained.
The entry into the new millennium was marked in the quantum community by the first experimental realizations of the Bose-Einstein condensation of atoms in a vapor, achieved in different research groups. Twenty-five years later, such systems are 'routinely' produced and are the core of many experiments. At the frontier between condensed matter their y, quantum optics, and atomic physics, ultra-cold atoms are subjects of high scientific interest.Ultra-cold gas can be trapped in optical lattices, giving a realistic way of experimentally realizing a new range of lattice Hamiltonians, that are used to simulate condensed matter systems. In these simulations, ultra-cold atoms are used to mimic the behavior of electrons in a solid-state material and could be used to simulate a wide range of complex condensed matter phenomena, such as the fractional quantum Hall effect, topological insulators, and high-temperature superconductivity.In order to study such systems, diffraction-limited quantum gas microscopes have emerged as a way to manipulate and detect atoms trapped in lattice potentials. Using far-field interference, experiments have mainly been restricted to a lattice spacing of 500 nm. This limits the speed of dynamics of all physical processes.Higher energy regimes could be accessed by reducing the lattice spacing. For this purpose, one of the long-term goals of the team is to trap atoms in the near-field of a surface and to make use of the Casimir-Polder forces to shape sub-wavelength potentials. Thanks to nano-fabrication capabilities, the spacing can be reduced to a few tens of nanometers. However, this requires to adapt the imaging techniques to observe cold-atoms with sub-wavelength spatial resolutions.In this PhD thesis, I report first on the advances toward implementing an atom chip in our experiment, which will serve as an integrated platform to manipulate the quantum gas. I present simulations and study an experimental solution allowing the cloud to be transported to the near-field. The method is based on the interference of a laser radiation in the near field of a rotating surface. It has been fully simulated, and the limitations have been numerically and experimentally assessed. I conclude this part by presenting the first model of chip that has been fabricated.In a second part, I report on the development of a sub-wavelength imaging method of cold Rubidium 87 atoms which is based on excited state dressing. I detail the concept of this nano-metric spatial resolution method and apply it to super-resolve a single longitudinal wave function trapped in a tight lattice that exhibits a width below 30 nm.