Bulletin of the American Physical Society
2015 Annual Meeting of the APS Mid-Atlantic Section
Volume 60, Number 14
Friday–Sunday, October 23–25, 2015; Morgantown, West Virginia
Session A2: Atomic Control and Interactions |
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Chair: Ryan Wilson, US Naval Academy Room: Morganton Marriott B1 |
Saturday, October 24, 2015 10:30AM - 10:42AM |
A2.00001: Superfluid Atom Circuits Gretchen Campbell Weak connections between superconductors or superfluids can differ from classical links due to quantum coherence, which allows for flow without resistance. The properties of a weak link are characterized by a single function, the current-phase relationship. In recent experiments with a ring-shaped Bose Einstein condensate, we have developed a technique to directly measure the current-phase relationship of a weak link. Our weak link is created using a laser beam that acts as a barrier across one side of the ring condensate. By rotating the weak link we can control the current around the ring. When the weak link is rotated at low rotation rates, we have observed phase slips between well-defined, quantized, current states, and have demonstrated that the system exhibits hysteresis. Recently, we have studied the time needed for phase slips to occur, as well as the role temperature plays in the process. At higher rotation rates we have directly measured the onset of resistive flow across the weak link. Such measurements may open new avenues of research in quantum transport. [Preview Abstract] |
Saturday, October 24, 2015 10:42AM - 10:54AM |
A2.00002: Atom Interferometer Gradient Magnetometer Arvind Srinivasan, Sara DeSavage, Charles Adler, Jon Davis, Francesco Narducci We have used cold $^{85}$Rb atoms in a fountain experiment to measure magnetic fields and magnetic field gradients in our apparatus. Optically prepared atoms are tossed up a 10 cm tall tower and a pulse of light stimulating a Raman transition is applied at times variable with respect to the time of the toss. Knowledge of the magnetic field is extracted from the Raman spectrum, which is measured at various heights in the tower. From these measurements, we can map out the magnetic field within the tower. We describe methods for phase locking the Raman laser to the cooling laser in order to control fluctuations in the AC stark shifts caused by the free running Raman laser. We also describe a method for probing magnetic field gradients at two locations simultaneously. [Preview Abstract] |
Saturday, October 24, 2015 10:54AM - 11:06AM |
A2.00003: Resonant wavepackets and shock waves in an atomtronic SQUID Yi-Hsieh Wang, A. Kumar, F. Jendrzejewski, Ryan M. Wilson, Mark Edwards, S. Eckel, G. K. Campbell, Charles W. Clark The fundamental dynamics of ultracold atomtronic devices are reflected in their phonon modes of excitation. We probe such a spectrum by applying a harmonically driven potential barrier to a $^{23}$Na Bose-Einstein condensate in a ring-shaped trap. This perturbation excites phonon wavepackets. When excited resonantly, these wavepackets display a regular periodic structure. The resonant frequencies depend upon the particular configuration of the barrier, but are commensurate with the orbital frequency of a Bogoliubov sound wave traveling around the ring. Energy transfer to the condensate over many cycles of the periodic wavepacket motion causes enhanced atom loss from the trap at resonant frequencies. Solutions of the time-dependent Gross-Pitaevskii equation exhibit quantitative agreement with the experimental data. We also observe the generation of supersonic shock waves under conditions of strong excitation, and collisions of two shock wavepackets. [Preview Abstract] |
Saturday, October 24, 2015 11:06AM - 11:18AM |
A2.00004: Control of Trapped Ions on a Chip Trap for Quantum Information Katherine Collins, Kenneth Wright, Christopher Rickerd, Christopher Monroe Macroscopic traps have been the standard ion trap for some time; however, these traps are fabricated by hand, making them difficult to reproduce and therefore not scalable. Micro-fabricated surface traps, such as the ``Ball Grid Array" (BGA) trap designed by Georgia Tech Research Institute (GTRI) and micro-fabricated by Honeywell International, are the new generation of ion traps. These surface traps are produced in CMOS foundry and are highly reproducible and scalable. Our group traps $^{171}$Yb$^{+}$ ions using the 48-electrode BGA trap that improves the control of the ions. We discuss the ability to shuttle ions to different areas on the trap as well as optical control, coherent operations, measurement of heating rate of the ions in the trap, and the possible quantum information application of boson sampling\footnote{S. Aaronson, S. and A. Arkhipov, Proc. 43rd Annual ACM Symposium on Theory of Computing, 333 (2011).}$^{,}$\footnote{C. Shen, Z. Zhang, and L.-M. Duan, Phys. Rev. Lett. 112, 050504 (2014)}. [Preview Abstract] |
Saturday, October 24, 2015 11:18AM - 11:54AM |
A2.00005: Direct Observation of Spin- and Charge-Density Waves in a Luttinger Liquid Invited Speaker: Kenneth O'Hara . [Preview Abstract] |
Saturday, October 24, 2015 11:54AM - 12:06PM |
A2.00006: Multidimensional coherent spectroscopy of a semiconductor microcavity Brian Wilmer, Felix Passmann, Michael Gehl, Galina Khitrova, Alan Bristow Two-dimensional coherent spectra map the anticrossing associated with normal-mode splitting in a semiconductor microcavity [1]. For a 12-meV detuning range near zero detuning, two diagonal features related to intra-action of exciton-polariton branches and two off-diagonal features related to coherent interaction between polaritons are observed. At negative detuning, line shape properties of diagonal intra-action features are distinguishable and can be associated with cavitylike and excitonlike modes. A biexcitonic feature is observed, shifted from the exciton feature by the biexciton binding energy. Closer to zero detuning, all features are enhanced and diagonal intra-action features become nearly equal in amplitude and linewidth. At positive detuning excitonlike and cavitylike characteristics return to the diagonal intra-action features. Off-diagonal interaction features exhibit asymmetry in their amplitudes throughout the detuning range. Amplitudes are strongly modulated (and invert) at small positive detuning, as the lower polariton branch crosses the bound biexciton energy determined from negatively detuned spectra. \newline [1]. Wilmer et al, Phys. Rev. B 91, 201304(R) (2015) [Preview Abstract] |
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