Session F2: Atomic, Molecular and Optical Physics

Towards Quantum Double-Well Dynamics of Trapped Ion Crystals near a Structural Phase Transition

Small arrays of laser-cooled trapped ions are widely used for quantum information research, but they are also a versatile mesoscopic system to investigate physics with a flavor reminiscent of familiar models in condensed matter. For example, in a linear rf Paul trap, laser-cooled trapped ions organize into a linear array when the transverse confinement of the trap is strong enough; however, at a critical trap anisotropy the ions undergo a symmetry–breaking structural transition to a two-dimensional zigzag configuration. I will discuss our current investigations of dynamics near this linear-zigzag transition at ultralow temperatures, corresponding to just a few quanta or less of thermal energy in the vibrations of the ion array. The second-order nature of the linear-zigzag transition, and the resulting double-well potential that develops as the transition is crossed, offer the possibility to explore a variety of quantum effects, in particular tunneling phenomena near the critical point. We are interested to see whether superposition states of the zig and zag symmetry-broken configurations can be prepared, and how the decoherence of such states depends on the number of ions.   

Dual Species Co-Magnetometer using 129Xe and 199Hg for Measurement of the Neutron's Electron Dipole Moment

A new ultra cold neutron (UCN) facility is under development with a flagship experiment of measuring the neutron’s electric dipole moment (EDM) with a precision of $10^{-27}$ e-cm. Construction of the main apparatus is taking place at TRIUMF, with collaborators from Japan and Canada. To measure the nEDM, a magnetic resonance experiment on polarized neutrons is performed, where the uncertainty is limited by how well the magnetic field and its gradient are known. Previous nEDM experiments relied on in-situ measurements of the magnetic field using a Ramsey fringe measurement of the spin precession of 199Hg (cohabiting with the neutrons). In our work we introduce 129Xe as a second species (forming a dual co-magnetometer with 199Hg). Both species are utilized simultaneously to measure the magnetic field, thereby lowering the systematic uncertainties in the nEDM measurement. 129Xe was chosen for several reasons including its negligible interaction with the neutrons and 199Hg. The spin precession of polarized 129Xe is detected by measuring the fluorescence decay following a spin-selective 126-nm optical transition of 5p$^{6}$($^{1}$S$_{0}$) \rightarrow 5p$^{5}$($^{2}$P$_{3/2}$)6p. In this talk I will present our current progress in preliminary spectroscopy on 129Xe.   

Large Energy Superpositions via Rydberg Dressing

We propose to create superposition states of over 100 Strontium atoms being in a ground state or metastable optical clock state, using the Kerr-type interaction due to Rydberg state dressing in an optical lattice. The two components of the superposition can differ by of order 300 eV in energy, allowing tests of energy decoherence models with greatly improved sensitivity. We take into account the effects of higher-order nonlinearities, spatial inhomogeneity of the interaction, decay from the Rydberg state, and diminishing Rydberg level separation for increasing principal number.\\ \\M. Khazali, H. W. Lau, A. Humeniuk, C. Simon, arXiv:1509.01303v2 (2015)   

Non-linear optics in cold $^{\mathrm{87}}$Rb atoms at ultralow powers via an optical nanofiber

Tight confinement of the evanescent field around subwavelength diameter optical nanofibers (ONF) presents a suitable tool for studying nonlinear optics in atomic media. Such ultrathin fibers integrated with cold atoms can also provide ideal building blocks for atom-photon hybrid quantum networks. Here, we study phenomena, e.g. Autler-Townes splitting (ATS) and electromagnetically induced transparency (EIT) using a \textasciitilde 350 nm diameter ONF surrounded by laser-cooled rubidium atoms. We use a near or on-resonance two-photon excitation process in a three-level ladder type configuration to observe the effects. The impact of the high intensity light field on the ground and intermediate atomic states is studied in terms of ATS [1]. Multilevel cascaded EIT is demonstrated and exploited to make an all-optical switch [2]. Power levels needed to observe these nonlinear effects are in the range of nanoWatts. Apart from their fundamental importance, these studies will be useful for fiber based quantum networks with Rydberg atoms. Reference: [1] R. Kumar, V. Gokhroo, K. Deasy, and S. Nic Chormaic, Phys. Rev. A 91, 053842 (2015) [2] R. Kumar, V. Gokhroo, and S. Nic Chormaic, New J. Phys. 17, 123012 (2015)   

Spin-orbit coupled Bose-Einstein condensates with lattice-band pseudospins

Dilute-gas Bose-Einstein Condensates provide a flexible platform to model a wide variety of condensed matter phenomena. To this goal, dressing atoms with suitably tailored laser beams is a premier tool and can be used to generate spin-orbit coupling, artificial gauge fields, and lattice structures. In this talk, a set of recent and ongoing experiments conducted at Washington State University will be described in which we apply both static and moving optical lattices to form Floquet-Bloch states. The s-band and the px-band of the static lattice are considered pseudospins, and it is shown that spin-orbit coupling can be introduced between such lattice band pseudospins. The notion of lattice band pseudospins provides a new viewpoint for quantum gas experiments that may pave the way for engineering novel quantum matter using hybrid orbital bands.