Bulletin of the American Physical Society
43rd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 57, Number 5
Monday–Friday, June 4–8, 2012; Orange County, California
Session J2: Novel Techniques for Cold Atoms |
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Chair: Cass Sackett, University of Virginia Room: Grand Ballroom GF |
Wednesday, June 6, 2012 2:00PM - 2:12PM |
J2.00001: Characterization and manipulation of a high-magnetic field trap Eric Paradis, Georg Raithel We report on the characterization of an efficient atom trap within a background magnetic field of 2.6 Tesla. Up to 10\^{}8 Rubidium atoms are recaptured from a cold atomic beam with a 2-3{\%} collection efficiency, in a cigar-shaped volume and cooled with a six-beam optical molasses. The aspect ratio of the trap is measured as a function of the magnetic field curvature, which can be varied to produce a range of trap shapes. The trapping lineshape is both narrow and asymmetric, as is characteristic of laser-cooling of atoms or ions in an external trapping potential. Additional features of the high magnetic field trap include cooling onto hollow shell-like structures. Simulation results are also presented. [Preview Abstract] |
Wednesday, June 6, 2012 2:12PM - 2:24PM |
J2.00002: Towards ultracold single neutral atoms in microscale optical dipole traps Adam Kaufman, Brian Lester, Cindy Regal We seek to create a small array of single neutral atoms laser-cooled to their motional ground state in microscale optical dipole traps. Experiments in such traps have demonstrated versatile capabilities in quantum logic and atom-light coupling, but to-date the atomic motion has often been uncontrolled and limiting. By cooling atoms in a few movable traps created with a high numerical aperture lens we envision abilities such as: Studying small arrays of interacting atoms with individual initialization of motion and spin, and coupling localized atoms to submicron optical modes. We present our initial studies of trapping and laser cooling a single $^{87}$Rb atom. [Preview Abstract] |
Wednesday, June 6, 2012 2:24PM - 2:36PM |
J2.00003: A passively pumped cell for cold and ultracold atoms K.J. Hughes, A. Brown, T. Arpornthip, C.A. Sackett The demanding vacuum environment required by many techniques in AMO physics is one barrier to commercialization of these technologies. Even some research applications are hampered by the magnetic and electrical interference coming from conventional vacuum pumps and metal vacuum fittings. To help address these problems, we have developed an ultra-high vacuum cell that uses only passive pumping techniques and requires a minimal amount of metal. Vacuum in the cell was adequate to implement a rubidium magneto-optical trap and to maintain it over an extended period of time without active pumping. The demonstrated cells are simple and very compact, but a wide variety of configurations can be manufactured using similar techniques. We will present our results and discuss strategies for the future direction of this research. [Preview Abstract] |
Wednesday, June 6, 2012 2:36PM - 2:48PM |
J2.00004: Optical bichromatic forces for enhancing the number of trapped atoms Joshua Grossman, Adam Hammett, Francesco Narducci Many applications of cold, trapped atoms would benefit from an increased number of atoms. Fieldable devices, such as sensors, need to be small. Because the number of trapped atoms scales as the fourth power o f the trapping beam, reducing the size of the laser beams used in a magneto-optical trap leads to a large reduction in the number of trapped atoms. A larger optical force can potentially compensate for the reduction in stopping distance. Bichromatic forces rely on absorption followed by stimulated emission and, as such, they are in principle limited only by laser intensity. While bichromatic forces have been applied for cooling in one dimension, we present here our work toward using bichromatic forces for both cooling and trapping in three dimensions. [Preview Abstract] |
Wednesday, June 6, 2012 2:48PM - 3:00PM |
J2.00005: Loading and high efficiency evaporative cooling to BEC with a MACRO-FORT Abraham Olson, Robert Niffenegger, Yong P. Chen We present modeling and experimental results for efficient evaporative cooling in all-optical BEC experiments. By employing a misaligned crossed-beam far off-resonance optical dipole trap (MACRO-FORT [1]) we achieve decreasing trap depth with increasing average trap frequency during the evaporative cooling process, allowing highly efficient runaway evaporation. This method is effective even with a low initial atom density, and it has experimentally allowed us to create BECs of $^{87}$Rb starting from only a few $10^5$ atoms initially in the optical trap before evaporation. We have also studied the direct loading of $^{87}$Rb atoms from a MOT to our 1550nm optical trap, where the atomic D2 transition has a significant AC Stark shift.\\[4pt] [1] J.-F. Clement \textit{et al}., Phys. Rev. A \textbf{79}, 061406(R) (2009) [Preview Abstract] |
Wednesday, June 6, 2012 3:00PM - 3:12PM |
J2.00006: Trapping atoms in a bottle beam generated by a diffractive optical element V. Ivanov, J. Isaacs, M. Saffman, S.A. Kemme, G.R. Brady, A.R. Ellis, J.R. Wendt Highly excited Rydberg states have been used to demonstrate a neutral atom quantum gate, two-atom entanglement and hold promise for studies of surface potentials, such as the Casimir-Polder potential. Blue detuned Optical Bottle Beam (BoB) traps where atoms are confined in intensity minima trap both ground and Rydberg state atoms. This minimizes qubit decoherence and allows accurate measurements of the frequencies of the Rydberg transitions. We have generated optical bottle beam traps using a segmented diffractive optical element with $\pi$ phase shift between the inner and outer regions. The idea for this trap follows the approach used by Ozeri, et al. Phys. Rev. A 59, R1750 (1999) but integrates the phase shift and focusing lens into a single diffractive element fabricated at Sandia National Lab. Measured profiles of the trap light intensity are compared with numerical predictions using a Fresnel diffraction code. Progress towards atom trapping in the bottle for studies of atom-surface interactions will be presented. [Preview Abstract] |
Wednesday, June 6, 2012 3:12PM - 3:24PM |
J2.00007: Study of mesoscopic clouds of cold atoms in the interacting regime Ronan Bourgain, Andreas Fuhrmanek, Joseph Pellegrino, Yvan R.P Sortais, Antoine Browaeys We present studies on cold and dense atomic $^{87}$Rb clouds containing $N\sim 2-100$ interacting atoms. We produced such mesoscopic ensembles by loading a microscopic optical dipole trap from a MOT. Due to $2$-body light-assisted collisions, we have found that in steady state such ensembles exhibit reduced number fluctuations with respect to a Poisson distribution. For $N \geq 2$, we measured a reduction Fano factor $F=0.72\pm0.07$ consistent with the value $F=3/4$ predicted at large $N$ by a general stochastic model [1,2]. To enhance interactions between the atoms, we are following two tracks. Firstly we evaporatively cooled a few hundreds of trapped atoms and obtained $\sim10$ atoms close to quantum degeneracy ($n\lambda_{dB}^3\sim1$) in the microscopic trap. In this regime s-wave interactions dominate ($n=2~10^{14}$~at.cm$^{-3}$). Secondly we sent near resonant light ($\lambda_{p}$) on the small cloud (size $l$). When $l<\lambda_{p}/2\pi$, dipole-dipole interactions should lead to collective behaviour.\\[4pt] [1] A. Fuhrmanek, Y.R.P. Sortais, P. Grangier, A. Browaeys, Phys. Rev. A \textbf{82}, 023623 (2010).\\[0pt] [2] Y.R.P. Sortais, A. Fuhrmanek, R. Bourgain, A. Browaeys, ``Sub-Poissonian atom number fluctuations using light-assisted collisions,'' arXiv:1111.5203 (2011). [Preview Abstract] |
Wednesday, June 6, 2012 3:24PM - 3:36PM |
J2.00008: See-saw Doppler cooling of three-level atoms by coherent pulse trains Mahmoud Ahmed, Ekaterina Ilinova, Andrei Derevianko We explore the feasibility of decelerating and Doppler cooling an ensemble of three-level $\Lambda$-type atoms by a coherent train of ultrashort laser pulses. In the frequency domain such trains form frequency combs. We show that driving atoms by frequency combs that do not satisfy the two-photon Raman resonance condition results in a persistent radiative force. We also propose a see-saw scheme of cooling multilevel atoms. In these scheme the teeth of the frequency comb are periodically moved in and out of resonance for the allowed transitions. The see-saw cooling may be practically attained by switching carrier-envelope phase between predefined values. We carry out numerical calculations of optimal train parameters, radiative force and time evolution of the velocity distribution [Preview Abstract] |
Wednesday, June 6, 2012 3:36PM - 3:48PM |
J2.00009: Towards site-resolved imaging and control of ultracold fermions in optical lattices Florian Huber, Widagdo Setiawan, Kate Wooley-Brown, Maxwell Parsons, Sebastian Blatt, Markus Greiner Recent successes in site-resolved imaging and control of bosonic Rb atoms trapped in optical lattices have enable many new possibilities to emulate simple condensed matter systems. Many of the open questions in condensed matter, however, stem from the fermionic nature of electrons. Extending the high degree of control available with ultracold quantum gases in optical lattices to fermionic atoms will allow us to address these questions. The light mass of fermionic 6-Li leads to system dynamics on fast timescales, making it an ideal candidate for such studies. We report progress towards a 6-Li quantum gas microscope and present improved imaging, cooling, and trapping techniques compatible with the light mass of 6-Li. A major challenge in the pursuit of single-site imaging with Lithium is cooling atoms during the imaging process. Single-site experiments with bosons benefit from the resolved hyperfine splitting in the excited state of 87-Rb, which allows the use of optical molasses. This method cannot be straightforwardly applied to 6-Li. We present our efforts to cool and image 6-Li using Raman sideband cooling. [Preview Abstract] |
Wednesday, June 6, 2012 3:48PM - 4:00PM |
J2.00010: Optical control of Feshbach resonances in Fermi gases using molecular dark states Haibin Wu, John E. Thomas We investigate optical control of magnetic Feshbach resonances in ultracold atomic gases with more than one molecular state in an energetically closed channel. Using two optical fields to couple two states in the closed channel, inelastic collisional loss arising from spontaneous emission is greatly suppressed by destructive quantum interference near the two-photon resonance, i.e., dark-state formation, while the scattering length is widely tunable. Further, the effective range can be controlled by varying the parameters of optical fields. The method opens many new fields of study, such as nonequilibrium strongly interacting Fermi gases and new cooling mechanisms with narrow Feshbach resonance. [Preview Abstract] |
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