1,720,978 research outputs found
Advancing Atom Interferometry with a Bloch-bands Approach
No full textThesis (Ph.D.)--University of Washington, 2019This work presents experiments and theory on ``magic depths" in Bloch oscillation acceleration pulses and the implications for advancing atom interferometry. For a particle in a sinusoidal potential, we define the magic depth as the depth where there is a vanishing first derivative of its average energy\footnote{Averaged over the first Brillouin zone.}, occurring only for excited bands. A Bloch-bands picture demonstrates that this average area is proportional to the diffraction phase shift experienced by a particle undergoing Bloch oscillations. A vanishing first derivative permits the phase to be significantly more stable against unavoidable light intensity fluctuations, creating new opportunities for the use of Bloch oscillations within atom interferometers
Interacting Quantum Gases of Lithium and Ytterbium
No full textThesis (Ph.D.)--University of Washington, 2013This dissertation describes the development of a scientic apparatus for trapping ultracold quantum gases of atomic lithium and ytterbium, and discusses the studies of interactions between such particles under a range of experimental conditions. The atoms are sequentially magneto-optically trapped and cooled, and subsequently transferred to an optical dipole trap. It is shown that, due to the details of the electronic structure of the constituent species, as well as the large atomic mass of ytterbium, the system is well-suited for cooling to temperatures well below a microkelvin, and for subsequent studies of quantum few- and many-body physics. The dynamical behavior of the ultracold samples is studied at a wide range of interaction strengths. These are controlled by means of externally applied magnetic fields, or by optical transfer of atoms to long-lived, metastable orbitals. The work described in this paper paves the way for a large number of future experiments, including studies of quantum few-body physics in highly mass-mismatched systems and studies of dipolar matter using ultracold LiYb molecules
Vertical Contrast Interferometry and Bloch-Band Approach to Atom Optics
Full text linkThesis (Ph.D.)--University of Washington, 2020This dissertation covers a series of atom interferometry experiments with a focus on applying the Bloch-band model to atom optics and performing vertical interferometry with a magnetically neutral atom. This approach lets us analyze the diffraction processes from a pulsed optical lattice in terms of the Bloch solutions for the atom in the periodic lattice Hamiltonian. Using a ytterbium (174Yb) Bose-Einstein condesate as the matter-wave source, measurements of Rabi frequencies, as well as those of diffraction phase and amplitude, demonstrate the validity of the Bloch-band approach over a regime which is typically satisfied within an atom interferometer. Applications for this model are discussed, including the use of an interferometric phase measurement to determine an unknown band structure. Additionally, a unique feature of the excited Bloch-bands—the magic depth—is exploited to improve the phase stability of atom interferometers which use Bloch oscillations for large momentum transfer. We also demonstrate the technique of delta-kick cooling as a fruitful method for reduction of the BEC’s vertical velocity distribution, allowing for more efficient momentum transfer with a vertical optical lattice. This is a crucial tool for non-magnetic atoms such as 174Yb, which we use to perform vertical interferometry in our system with both a contrast interferometer geometry and a double Mach-Zehnder interferometer. Lastly, the effect of Landau-Zener-St¨uckelberg interference during Bloch oscillations is studied in its relation to momentum transfer efficiency for precision interferometry
Ytterbium and Lithium Quantum Gases: Heteronuclear Molecules and Bose-Fermi Superfluid Mixtures
No full textThesis (Ph.D.)--University of Washington, 2017-06This dissertation describes a series of experiments conducted in an ultracold mixture of fermionic 6Li and bosonic 174Yb atoms, with a focus on the creation of heteronuclear YbLi molecules and the realization of a mixture of Bose and Fermi superfluids. Measurements of field-dependent inelastic scattering between metastable (3P2) Yb and ground state (2S1/2) Li are discussed, revealing the existence of interspecies Feshbach resonances which in principle may be used to create ultracold YbLi molecules in a coherent fashion, but in practice exhibit prohibitively large inelastic loss in the specific scattering channel used. An alternative all-optical two-photon pathway to ground state YbLi molecules is also explored, with the initial results presented here being the exploration of excited state YbLi molecular potentials using photoassociation spectroscopy, and the successful production of YbLi* molecules in a dual-species magneto-optical trap. An upgraded crossed optical dipole trap is implemented on the Yb-Li experimental apparatus, with a novel application of time-averaged potential shaping for very rapid and efficient Yb BEC production. Lastly, we detail the realization of an interacting mixture of Bose and Fermi superfluids, and identify the exchange of angular momentum between the superfluids by the excitation of a rotational mode of oscillation in the bosonic component due to interspecies interactions
Laser Cooling and Trapping of 6Li: Experimental Tools for Many-Body Fermionic Dynamics and Ring Trap
No full textThesis (Ph.D.)--University of Washington, 2023This thesis delves into the laser cooling and trapping of 6Li, a fermionic atom, with the aimof creating experimental tools for the exploration of many-body fermionic dynamics in quantum
degeneracy, specifically within ring traps. We provide an overview of 6Li properties,
the theoretical underpinnings of many-body fermionic dynamics in cold atom traps, and the
principles of AC Stark shift in far-off-resonance light fields. Our experimental apparatus,
capable of trapping Yb and Li, and completed experiments on YbLi Magnetic Feshbach
Resonance (MFR) and Yb bosonic dynamics are detailed, along with technical adaptations
for laser cooling and trapping of 6Li towards a single-species Fermi condensate. We discuss
our sub-Doppler cooling system, magnetic field stabilization method, and progress towards
quantum degeneracy, as well as a developed method of optical pulses to induce dynamics
in the paired Fermi condensate. Our work on ring traps and entrainment, including the
development of a ring beam setup using a Digital Micromirror Device (DMD), is also elaborated.
The thesis concludes by underscoring the significance of our developments in the
context of many-body fermionic dynamics in quantum degeneracy and the use of ring traps
for studying dual-superfluid systems, contributing to the broader field of ultracold atomic
physics
Ytterbium Atom Interferometry Within an Optical Lattice
Full text linkThesis (Ph.D.)--University of Washington, 2025Matterwave interferometers utilizing atoms and optical lattices are subject to theinstabilities and systematics associated with lattice dynamics. We apply a Bloch
band approach to atom optics to understand the systematic effects on interferometric
phases. In particular, we examine the effects of the coherent quantum passage of
atoms accelerating in different lattice bands—also known as Bloch oscillations—in a
vertically oriented optical lattice for atom interferometry. This work details observations
of multi-path Landau-Zener-Stückelberg-Majorana interference effects, used to
measure phases within an optical lattice due to Bloch oscillations. We expound on
their relevance towards next-generation atom interferometers employing many Bloch
oscillations for improved sensitivity. Optical lattices are also a promising tool for
trapped atom interferometry, the matterwave analog for optical interferometry with
fiber optics. We demonstrate the first lattice-trapped atom interferometer with a
Bose-Einstein condensate. The effect of the choice of band on the visibility of lattice-trapped
interferometers has been hitherto unexplored. We show improvements in the
visibility of the interferometer fringes by trapping at the so-called “magic depths” of
excited bands, where lattice-induced phases are first-order insensitive to variations in
lattice depth. We showcase excited-band lattice-trapped interferometers and trapped
interferometers for ytterbium for the first time and use them for gravitational sensing
Interaction-driven dynamical delocalization in a kicked one-dimensional ultracold gas
No full textThesis (Ph.D.)--University of Washington, 2022This dissertation reports on the experimental observation of interaction-driven dynamical delocalization in a kicked one-dimensional ultracold gas. In the absence of interactions, particles in a one-dimensional disordered medium are localized due to quantum interference as predicted by the Anderson model. The evolution of this well-known localization phenomenon in the presence of interactions has been the subject of intense scrutiny in the past decades, including conflicting theoretical predictions in some cases. Using the quantum kicked rotor (QKR), we engineered the Anderson model in the synthetic momentum space where the equivalent localization phenomenon is termed dynamical localization. However, interaction effects had not been observed in earlier experimental observations of dynamical localization. We detail the implementation of a three-dimensional optical lattice that is used to control the interactions in the system and to realize the QKR Hamiltonian. Using ultracold gases in 1D tubes, we perform a quantum simulation of the QKR Hamiltonian in the presence of interactions and find that interactions destroy the localization and lead to slower-than-linear energy growth or sub-diffusive dynamics. The measured sub-diffusive exponents are not universal or monotonically varying with the various experimental parameters. However, we find that the onset time of delocalization is always shorter with stronger interaction or kick strengths. By temporally modulating the kick strength with incommensurate frequencies, we also engineered higher dimensional Anderson models and observed similar interaction-driven delocalization phenomena. The metal-insulator Anderson transition in the presence of interactions is also studied in the 3D case with varying kick strength. Our results shed light on interaction-driven transport, in a regime where theoretical approaches are extremely challenging and predict drastically different dynamics
Interactions in the Ultracold Lithium Ytterbium 3P2 System
No full textThesis (Ph.D.)--University of Washington, 2015I detail the execution and results of experiments in a mixture of ultracold atomic gases using fermionic lithium (6Li) and bosonic ytterbium (174Yb) in the metastable 3P2 state. We demonstrate efficient transfer of ground state Yb atoms to this metastable state in the presence of Li. A method to spin-purify the resulting metastable Yb atoms via a magnetic gradient is presented. We investigate intra-species and inter-species inelastic collisions over a wide range of magnetic fields. The resulting inelastic spectrum is linked to a potential collisional resonance between the m_J=-1 metastable state of Yb and ground state Li near 450G. This work begins the path towards creation of trapped ultracold and magnetic ground state molecules. Such molecules allow experiments which cannot be accessed by current generations of bi-alkali molecule experiments
Heteronuclear Feshbach Resonances in Ultracold Mixtures of Ytterbium and Lithium
No full textThesis (Ph.D.)--University of Washington, 2019This thesis reports on experimental observation of heteronuclear Feshbach resonances between ultracold alkaline-earth-like Yb and alkali Li atoms, revealing methods for experimental control of heteronuclear scattering properties and strategies for coherent production of YbLi molecules. Optical Feshbach resonances are observed between Yb-174 and Li-6 through photoassociation (PA) spectroscopy. Two-photon PA spectroscopy of a series of the least-bound vibrational states in the YbLi electronic ground state provides an accurate description of the long-range interatomic potential and an accurate value of the s-wave scattering lengths between Yb and Li. A dark atom-molecule superposition state is created by optically dressing pairs of colliding atoms within an optically trapped bulk mixture and the feasibility of using such a state for coherent molecule production through stimulated Raman adiabatic passage is discussed. Magnetic Feshbach resonances (MFRs) between Yb-173 and Li-6 are observed. In the combination of closed-shell Yb and open-shell Li, MFRs are shown to stem from short-ranged hyperfine coupling between the unpaired Li electron spin and the Yb-173 nuclear spin, as demonstrated by analysis of Feshbach spectroscopy on ultracold mixtures in which both species are fully spin polarized. This work identifies two pathways for the coherent production of paramagnetic, polar molecules from a mixture of trapped Yb and Li: manipulation of either an optical or magnetic Feshbach resonance
Experiments in the Ultracold Lithium - Ytterbium System
No full textThesis (Ph.D.)--University of Washington, 2013I detail the construction of an experimental apparatus created for performing ultracold atomic experiments with fermionic lithium-6 (Li) and several isotopes of ytterbium (Yb), and several of the first experiments performed using this apparatus. The apparatus consists of a vacuum chamber, laser and auxiliary systems, which together are used to produce the first instance of trapped ultracold mixtures of lithium and ytterbium. We show that the system is stable and obtain the s-wave scattering properties of Li-Yb collisions. By using Yb to sympathetically cool Li, double quantum degeneracy is achieved. I demonstrate the versatility of the new system with several experiments. In the first, we investigate the behvaiour of Li near a broad Feshbach resonance, and modify it with Yb. In the second, we produce Yb in the metastable state, and trap it in a 1064 nm optical dipole trap, which allows for a technically simple spin polarization procedure. We then characterize the dynamics of a Li - metastable Yb mixture. The work described in this thesis provides a pathway to future extensions such as the magentic tuning of Li-Yb interactions and the production of LiYb molecules by either photo- or magnetoassociation. The potential interest of this specific system lies in the combination of alkali and spin-singlet atom, leading to a potential paramagnetic ground state molecule, and experimental realizations of systems which cannot be accessed with bialkali experiments
- …
