Bulletin of the American Physical Society
49th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics APS Meeting
Volume 63, Number 5
Monday–Friday, May 28–June 1 2018; Ft. Lauderdale, Florida
Session H04: Laser Cooling and Trapping |
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Chair: Brian Anderson, American University Room: Grand C |
Wednesday, May 30, 2018 8:00AM - 8:12AM |
H04.00001: Steady-state ultracold Sr with unity phase-space density ChunChia Chen, Shayne Bennetts, Rodrigo González Escudero, Benjamin Pasquiou, Florian Schreck We demonstrate a way to make a steady state sample of ultracold strontium with a phase-space density approaching degeneracy. This long-standing goal within atomic physics represents a critical step towards demonstrating steady-state quantum gas devices such as atom lasers, interferometers and superradiant lasers which hitherto have only been possible in pulsed operation. Our machine tackles this goal by simultaneously cooling atoms in spatially separated regions on both the broad 30-MHz and narrow 7.4-kHz linewidth Sr transitions [1]. In this way, we are able to continuously load a dipole trap at high phase space density in which a stark shift protected [2] dimple trap collects and concentrates the coldest atoms. We measure a steady-state atomic cloud with a phase-space density above unity. We discuss methods to characterize the atomic sample and search for signs of the existence of a steady-state Bose-Einstein condensate. [1] S. Bennetts et al, Phys. Rev. Lett. 119, 223202(2017). [2] S. Stellmer et al, Phys. Rev. Lett. 110, 263003(2013). [Preview Abstract] |
Wednesday, May 30, 2018 8:12AM - 8:24AM |
H04.00002: Towards arrays of strontium atoms in optical tweezers. Jacob Covey, Alexandre Cooper, Ivaylo Madjarov, Brian Timar, Emily Qiu, Alexander Baumgärtner, Manuel Endres Cold atoms in optical tweezer arrays have emerged as a versatile platform for quantum simulation and quantum computing. Recent work has demonstrated approaches to cooling atoms close to their motional ground state and to assembling atoms into large, defect-free arrays. We extend the work done on alkali atoms to strontium, where the cooling is done on the narrow intercombination transition, thus providing a unique setting where motional states are directly resolved. In this talk, we will describe our protocol for loading strontium atoms into tweezers near a green magic wavelength and for detecting them on the broad singlet transition while cooling on the intercombination line. We will then describe our strategy for exciting atoms to S-Rydberg states via a single photon transition from the optical clock state, providing a novel avenue for controlling coherent long-range interactions and investigating quantum many-body dynamics. [Preview Abstract] |
Wednesday, May 30, 2018 8:24AM - 8:36AM |
H04.00003: Single-Frequency Sisyphus Cooling of Lithium in the Presence of a Dipole Trap Yanping Cai, Daniel Allman, Parth Sabharwal, Kevin Wright We have applied a single-frequency large-detuning Sisyphus cooling technique (originally demonstrated with $^7$Li in free space: Hamilton \textit{et al.} PRA \textbf{89} 023409) to enhance capture of $^6$Li atoms in a NIR dipole trap. We report on the effectiveness of 1D and 2D Sisyphus cooling in the absence of other fields, and in the presence of crossed-beam traps up to 1 mK deep. The cooling technique is relatively insensitive to polarization, detuning, and magnetic fields. We expect to be able to enhance capture of both lithium isotopes simultaneously with a single-frequency Sisyphus beam detuned between the $^6$Li $D_2$ and $^7$Li $D_1$ lines. [Preview Abstract] |
Wednesday, May 30, 2018 8:36AM - 8:48AM |
H04.00004: Observation of sub-doppler cooling via swept adiabatic transfer in Rb Baochen Wu, Graham P. Greve, James K. Thompson Norcia et al (arXiv:1707.01944) recently demonstrated a novel cooling mechanism on narrow-linewidth optical transitions~in Sr. Counter-propagating laser beams are swept in frequency in a sawtooth manner to cause adiabatic Landau-Zener~transfers between an atom's ground state and excited state. ~Doppler shifts impose a time-ordering of the interactions with each laser beam such that the associated~photon recoils oppose the atom's motion, leading to cooling. Here we expand the idea to artificial two-photon transitions in Rb.~We are able to cool atoms from 42 uK to 6 uK over several sweeps, and we achieve a moderate amount of phase space~density compression. Because the dynamics of the adiabatic transfer are crucial for understanding the cooling rate, we~developed a generic model for assessing the feasibility of two-photon Landau-Zener transitions in the presence of free~space scattering, and propose a dimensionless quality factor~to quantify the maximum efficiency of the process. Both~the experiment and theoretical modeling may find potential applications in cooling molecules or other systems that lack~high-quality cycling transitions. [Preview Abstract] |
Wednesday, May 30, 2018 8:48AM - 9:00AM |
H04.00005: Demonstration of a magneto-optic trap formed using a reversible, solid-state electrochemical Rb device Songbai Kang, Kaitlin Moore, James Mcgilligan, Russell Mott, Allison Mis, Chris Roper, Elizabeth Donley, John Kitching Fast, reversible, low-power alkali-atom sources are desirable for both tabletop cold-atom experiments and portable cold-atom-based sensors. Previously, the alkali-atom sinking and sourcing functions of such a device have been demonstrated only in hot-atom applications[1]. In this work, we demonstrate the first rubidium (Rb) cold-atom magneto-optic trap (MOT) using this type of solid-state device. Unlike past efforts[2,3], the number of emitted Rb atoms is linearly dependent on current applied across the device and saturates the MOT number irrespective of vapor-cell material and geometry, while also consuming less than 1 mW of electrical power to regulate the alkali-atom number. Significantly, this device can also sink and store Rb atoms controllably. Measurement results show that the sinking time constant is at least as fast as 500 ms. Lastly, we demonstrate an order of magnitude suppression of MOT-number fluctuations by providing feedback to the device. The core technology of this device translates readily to other alkali and alkaline-earth elements that find a wide range of uses in cold-atom systems. [1] S. Kang et al, APL 110, 244101 (2017)~ [2] C. Klempt et al, PRA 73, 013410 (2006)~ [3] L. Torralbo-Campo et al, Nat. Sci. Rep. 5, 14729 (2015) [Preview Abstract] |
Wednesday, May 30, 2018 9:00AM - 9:12AM |
H04.00006: Density variations with mm-scale periodicity in optical molasses Timothy Roach, Patrick Connolly We have been studying large (mm) scale periodic density variations appearing in a conventional 6-beam magneto-optic trap and in optical molasses. Such phenomena have been documented before and have been ascribed not to optical potentials but rather to variation in stickiness of the optical molasses, which itself results from variation in the character of the net optical field polarization. For example, a small misalignment angle between the two laser beams of a nearly counter-propagating pair produces phase changes across the interaction region giving rise to long scale variations in molasses. In this simplest instance, we find a 1D fringe-like periodic density variation corresponding to a wave vector equal to the difference between the wave vectors of the two nearly counter-propagating beams. For the case of nearly perfect counter-propagating alignment, the long scale spatial variation appears as an instability in the MOT cloud position, since small phase shifts in any one beam dramatically affect the net polarization. We observe that small misalignment of a second pair of nearly counter-propagating beams produces density variations that are rotated or are periodic in two dimensions. We will present recent results on angle and polarization dependence. [Preview Abstract] |
Wednesday, May 30, 2018 9:12AM - 9:24AM |
H04.00007: The Quantum Efficiency of Adiabatic Transfer Laser Cooling J.P. Bartolotta, M.A. Norcia, J.R.K. Cline, J.K. Thompson, M.J. Holland SWAP (Sawtooth Wave Adiabatic Passage) cooling is a new laser cooling mechanism that offers significant advantages over traditional cooling techniques for particles with narrow linewidth transitions. The particles interact with counter-propagating laser beams that are repeatedly, linearly swept over the transition frequency. Compared to Doppler cooling, SWAP cooling's reduced reliance on spontaneous emission allows for larger slowing forces per scattering event, i.e., a higher quantum efficiency. Using simulation techniques such as quantum Monte Carlo wavefunction and c-number Langevin equation methods, we characterize the parameters necessary to achieve significant phase space compression with minimal scattering events. We also investigate other quantities of interest, such as minimum temperatures, conservative forces and capture range. SWAP cooling's ability to promote significant coherent transfer suggests its applicability to systems lacking closed cycling transitions, such as molecules. [Preview Abstract] |
Wednesday, May 30, 2018 9:24AM - 9:36AM |
H04.00008: Building one Molecule from a Reservoir of Two Atoms Lee Liu, Jonathan Hood, Yichao Yu, Jessie Zhang, Nicholas Hutzler, Till Rosenband, Kang-Kuen Ni We demonstrate building a single molecule from 2 atoms in an optical tweezer. We begin by trapping a single Cs and single Na atom in separate optical tweezers, then merging them into the same tweezer. The tightly trapped ultracold sample of precisely two atoms allows discovery of previously unseen resonances near the molecular dissociation threshold and the measurement of collision rates, providing a valuable tool for studies of chemical reactions in the single-atom limit. In addition, cold atoms trapped in an array of tight optical tweezers have allowed for single site manipulation and formation of defect-free crystals. Combining this with long range, anisotropic dipole dipole interactions and a myriad of possible long-lived pseudospin states afforded by polar molecules would provide an unprecedented resource for quantum simulation and quantum information processing. [Preview Abstract] |
Wednesday, May 30, 2018 9:36AM - 9:48AM |
H04.00009: Continuous loading of $\nu=0$ $^{85}$Rb$_2$ ultracold molecules in a crossed optical dipole trap from a magneto-optical trap Henry Passagem, Nadia Bouloufa-Maafa, Olivier Dulieu, Luis Marcassa The development of cooling and trapping techniques for diatomic polar molecules have been motivated by their wide range of potential applications, which are associated with their long-range dipole-dipole interaction and complex internal structure. Although, such applications are all very exciting, the production of a cold and dense molecular sample is still very challenging. Its main difficult is that laser cooling can’t be applied directly to any molecules since there is no close transitions, like in atomic systems. In this work, we have developed a technique to continuously load $\nu=0$ $^{85}$Rb$_2$ ultracold molecules into a crossed optical dipole trap from a standard magneto optical trap using a single light beam. Such beam is composed of a single frequency coherent light source, which is responsible for short range PA of cold rubidium atoms, and an incoherent broadband light source which transfers the molecules in different vibrational levels ($\nu_x$) of the singlet-ground-state X, into $\nu=0$, through optical pumping. The molecules can be observed by REMPI technique. The molecular trap lifetime was measured and we believe in present conditions is limited by on resonance photon scattering from the ODT. This technique maybe applied to different atomic systems as well. [Preview Abstract] |
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