My internship was with the Air Force Research Laboratory’s Quantum Sensing Timing group. This group has been heading research into high-aspect ratio, direct-bonded copper substrates for the last 2 decades and have made major contributions to the field in terms of the maximum achievable gradients for micro-scale chip traps. Over the course of this paper, I will detail some of the basic formalism involved, give a little history, detail some improvements made over the last few years, and then end with using what I’ve learned to theory- craft a functional atom-chip utilizing best-practices. This chip’s theoretical limits will hit a trap frequency of up to 1500 Hz, be able to trap up to 1.13 mm away from the chip surface and will need a perpendicular bias field of up to 132 Gauss.
My internship was with the Air Force Research Laboratory’s Quantum Sensing Timing group. This group has been heading research into high-aspect ratio, direct-bonded copper substrates for the last 2 decades and have made major contributions to the field in terms of the maximum achievable gradients for micro-scale chip traps. Over the course of this paper, I will detail some of the basic formalism involved, give a little history, detail some improvements made over the last few years, and then end with using what I’ve learned to theory- craft a functional atom-chip utilizing best-practices. This chip’s theoretical limits will hit a trap frequency of up to 1500 Hz, be able to trap up to 1.13 mm away from the chip surface and will need a perpendicular bias field of up to 132 Gauss.
Abstract : During 2005, a new basic research effort was begun to better understand confined cold atom systems and determine if atom interferometry for the detection of rotation was possible utilizing spatially and temporally modulated magnetic fields generated using currents running through traces on microchips. During the next seven years, significant progress has been made in evaluating the constraints posed by both theory and practical experimental considerations. This report encompasses three of these studies: collisional decoherence in trapped interferometers, adjustable microchip ring-traps, and atom chips on direct bonded copper substrates. The first of these describes an analytical model developed to describe the effects of collisions between atoms in a harmonic magnetically confined atom interferometer. The second describes a method to create an agile circular magnetic waveguide for deBroglie waves on a microchip, while the third presents the use of direct bonded copper (DBC) for the straightforward fabrication of high power atom chips. Each of these efforts has incrementally added to our cold atom interferometry knowledge base and has enabled the future construction of a working atom chip based interferometer for the ultrasensitive detection of rotation.
In order to take quantum mechanical systems out of the lab and produce practical devices, a method of miniaturizing and integrating apparatus components is needed. In the context of ultracold atomic gas experiments, the ideal method of achieving this miniaturization is the implementation of atom chip technology. By depositing micro-scale current carrying wires onto planar substrates, it is possible to create a magnetic trap capable of confining a cloud of neutral atoms in sufficient proximity to the chip surface for solid state devices to interact with the cloud. This thesis presents our lab’s first steps towards creating an atom chip capable of confining a cloud of rubidium-87. The chip prototypes were developed with the intent to incorporate them into the hybrid system apparatus within our lab. The chips are intended to serve as a platform for facilitating the interaction between the atomic gas ensemble and mesoscopic solid-state devices, allowing for the hybridization of the two systems. In this work I describe the design of the trapping wire configuration and the fabrication of the first two generations of chip prototypes. Additionally, I provide numerical simulations of the produced magnetic field, from which estimates of the trap frequency and depth can be calculated. Finally, I introduce some basic characterization tests of the absolute current limitations and resistive behavior of the chip wires, and the dimensional uniformity of the fabricated wire profiles.
Several techniques for manipulating neutral atoms (more precisely, ultracold clouds of neutral atoms) in chip-based magnetic traps and atomic waveguides have been demonstrated. Such traps and waveguides are promising components of future quantum sensors that would offer sensitivities much greater than those of conventional sensors. Potential applications include gyroscopy and basic research in physical phenomena that involve gravitational and/or electromagnetic fields. The developed techniques make it possible to control atoms with greater versatility and dexterity than were previously possible and, hence, can be expected to contribute to the value of chip-based magnetic traps and atomic waveguides. The basic principle of these techniques is to control gradient magnetic fields with suitable timing so as to alter a trap to exert position-, velocity-, and/or time-dependent forces on atoms in the trap to obtain desired effects. The trap magnetic fields are generated by controlled electric currents flowing in both macroscopic off-chip electromagnet coils and microscopic wires on the surface of the chip. The methods are best explained in terms of examples. Rather than simply allowing atoms to expand freely into an atomic waveguide, one can give them a controllable push by switching on an externally generated or a chip-based gradient magnetic field. This push can increase the speed of the atoms, typically from about 5 to about 20 cm/s. Applying a non-linear magnetic-field gradient exerts different forces on atoms in different positions a phenomenon that one can exploit by introducing a delay between releasing atoms into the waveguide and turning on the magnetic field.
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.
Microfabricated ion traps are an important tool in the development of scalable quantum systems. Tremendous advancements towards an ion quantum computer were made in the past decade and most requirements for a quantum computer have been fulfilled in individual experiments. Incorporating all essential capabilities in a fully scalable system will require the further advancement of established quantum information technologies and development of new trap fabrication techniques. In my thesis I will discuss the theoretical background and experimental setup required for the operation of ion traps. Measurement of the important ion trap heating rate was performed in the setup and I will discuss the results in more detail. I will give a review of microfabrication processes used for the fabrication of traps, outlining advantages, disadvantages and issues inherent to the processes. Following the review I will present my work on a concept for a scalable ion trap quantum system based on microwave quantum gates and shuttling through X-junctions. Many of the required building blocks, including ion trap structures with current-carrying wires intended to create strong magnetic field gradients for microwave gates were investigated further. A novel fabrication process was developed to combine current-carrying wires with advanced multilayered ion trap structures. Several trap designs intended for proof of principle experiments of high fidelity microwave gates, advanced detection techniques and shuttling between electrically disconnected ion traps will be presented. Also the electrode geometry of an optimized X-junction design with strongly suppressed rf barrier height will be presented. Further, I developed several modifications for the experimental setup to extend the existing capabilities. A plasma source capable of performing in-situ cleans of the trap electrode surfaces, which has been demonstrated to dramatically reduce the heating rate in ion traps, was incorporated. I will also present a vacuum system modification designed to cool ion traps with current-carrying wires and transport the generated heat out of the vacuum system. In addition a novel low-noise, high-speed, multichannel voltage control system was developed by me. The device can be used in future experiments to precisely shuttle ions from one trapping zone to another and also to shuttle ions through ion trap junctions. Lastly I will outline the process optimization and microfabrication of my ion trap designs. A novel fabrication process which makes use of the extremely high thermal conductivity of diamond substrates and combines it with thick copper tracks embedded in the substrate was developed. Large currents will be passed through the wires creating a strong and controllable magnetic field gradient. Ion trap designs with isolated electrodes connected via buried wires can be placed on top of the current-carrying wires, allowing the most advanced electrode designs to be fabricated with current-carrying wires.
In this work we present the results of studies of one-dimensional (1D) and twodimensional (2D) optical lattices on a chip.We have developed a method to create 1D and 2D optical lattices above an optical waveguide.The method is based on the destructive interference of the evanescent waves of two modes of the waveguide, resulting in a periodic array of nodes above the waveguide surface.For blue-detuned light, this constitutes an array of optical dipole traps for neutral atoms.One pair of modes coupled into a ridge waveguide creates a 1D array of nodes in this manner, and two orthogonal pairs of modes in a slab waveguide result in a 2D array of nodes.Computational analysis of our method showed that these optical atom chips may be suitable for use as a quantum register, and for studies of atom-surface interactions between the trapped atoms and the waveguide surface.Using realistic waveguide materials and laboratory laser parameters we found that for a laser power of ~100 mW nodes can be created ~100 nm above the waveguide surface.The nodes constitute atom traps that are ~1mK deep, and have trap frequencies ~1MHz and ground state sizes of ~10 nm.The spacing between traps is ~1 µm enabling individual addressing with a focused laser beam.iii With the implementation of two-qubit gates in mind, initial investigations of extensions of the basic 2D optical lattice were conducted.Computational results for a counter-propagating 2D optical lattice with very close trap spacing (~λ/4) in one dimension, and for a 2D optical lattice with adjustable spacing between pairs of traps in one dimension are presented.An experimental setup for the realization of the proposed 2D optical lattices on a chip was designed and built.Several cooling and trapping steps necessary to prepare a cold atom sample for loading of the 2D optical lattice have been implemented successfully.In the course of previous studies of atom-surface interactions, a novel surfaceionization detector for 2D imaging of neutral atom samples was built and characterized.We find a detection efficiency ~50 %, a spatial resolution of 20 µm and a time response < 1/30 s. iv To my family.v ACKNOWLEDGMENTS First and foremost I would like to thank my advisor Greg Lafyatis for everything that he taught me.I also want to thank Frank DeLucia for always being there with his advice when I needed it.I appreciate Eric Herbst and Junko Shigemitsu for being willing to serve on