Bulletin of the American Physical Society
2006 37th Meeting of the Division of Atomic, Molecular and Optical Physics
Tuesday–Saturday, May 16–20, 2006; Knoxville, TN
Session S5: Nonlinear Optics and Special Topics |
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Chair: Ray Garrett, University of Tennessee Room: Knoxville Convention Center 301AB |
Friday, May 19, 2006 8:00AM - 8:12AM |
S5.00001: Three body recombination for electrons in a strong magnetic field: magnetic moment Francis Robicheaux Using a classical Monte Carlo method, we have computed the three body recombination (two free electrons and a proton scattering into one free electron and a Hydrogen atom: $\rm e+e+p\rightarrow H+e$) in strong magnetic fields. The proton is fixed in space but the electrons are allowed their full, 3-dimensional motion. We investigate recombination for temperatures and fields similar to those used in recent experiments that generated anti- Hydrogen. The present rate is compared to that when the electrons' motion is given by the guiding center approximation, validating previous results at low temperature and demonstrating the breakdown of this approximation at higher temperature. Unlike the $B=0$ case, strong $B$ gives preferential recombination to atoms with positive magnetic moment. Also, the canonical angular momentum in the field direction is often negative even when the magnetic moment is negative. Both results affect the trapping of anti-Hydrogen using spatially dependent magnetic fields. [Preview Abstract] |
Friday, May 19, 2006 8:12AM - 8:24AM |
S5.00002: Defect dynamics in nonlinear photonic quasicrystals Barak Freedman, Guy Bartal, Mordechai Segev, Ron Lifshitz, Demetrios N. Christodoulides, Jason W. Fleischer Quasicrystals are structures with long-range order and no periodicity, with unique properties that arise from their broken-symmetry state. These include a hierarchy of effective Brillouin (Jones) zones, yielding a fractal-like band structure, and the existence of Goldstone-mode ``phason'' degrees of freedom. Here, we examine these features using optically-induced quasicrystals in nonlinear photorefractive media, taking advantage of the fact that internal wave dynamics can be locally excited and directly imaged. In particular, we report the direct observation of dislocation dynamics in a deformable quasicrystal (one whose sites interact with each other): creation, healing, and local structural rearrangement due to phason flips. Our experiments show that photonic quasicrystals are excellent model systems for studying universal features of wave dynamics in quasiperiodic structures, not only in optics but also in other systems, e.g. matter waves in quasiperiodic traps, parametrically-driven pattern-forming systems, and liquid and atomic quasicrystals. [Preview Abstract] |
Friday, May 19, 2006 8:24AM - 8:36AM |
S5.00003: Coupled dynamics of atoms and a radiation pressure driven interferometer Dominic Meiser, Pierre Meystre We consider the motion of the end mirror of a cavity that traps atoms in its standing wave intensity pattern. The mirror is subject to a harmonic restoring force as well as the radiation pressure force due to the light field inside the cavity. The atoms experience the optical dipole potential and collectively act back on the light field through their polarizability. This system is interesting, among other things, due to its inherent nonlinearities and retardation, the possibility of creating mesoscopic nonclassical states of motion and cooling of mirror and atoms through radiation pressure. In this talk we present a basic model for the coupled system. We analyze how the dipole potential is modified due to the back action of the atoms and we show that the position of the atoms can become bistable. We present results of simulations of the dynamics of the coupled system in the adiabatic regime. From these simulations we obtain sideband spectra of the light transmitted through the cavity and we show that these spectra can be used to identify and study the coupled motion in experiments. [Preview Abstract] |
Friday, May 19, 2006 8:36AM - 8:48AM |
S5.00004: Study of decoherence and dynamical decoupling in an optical lattice S. Maneshi, J.F. Kanem, C. Zhuang, M. Partlow, A.M. Steinberg Optimizing quantum error correction protocols in the presence of real-world experimental constraints is a major problem along the path to quantum-information implementations.~We present work on this problem in the context of an optical-lattice system. Cold $^{85}$Rb atoms are held in shallow optical lattices supporting only 1-3 bound states. We create superposition of vibrational states, and observe decoherence in the form of decay of oscillations. Quantum Process Tomography (QPT) is used to characterize decoherence and to study various pulses used to preserve the atomic coherence.~These control pulses are limited to manipulations of the lattice potential itself. We optimize simple and compound pulses, and use QPT to quantitatively compare loss of coherence and loss of atoms due to each pulse. A Gaussian shaped pulse is found to be superior to hard pulses in both parameters. We then apply a series of optimized pulses, and observe second and third order echo signals. By confining atoms in a 3D lattice, we study the effect of transverse motion of atoms on the coherence time of the system and compare it to a 1D lattice. The 3D lattice makes it possible to characterize decoherence due to tunneling as a homogeneous or inhomogeneous broadening effect. With our methods, we are able to characterize decoherence processes, implement dynamical decoupling schemes, and study the role of tunneling on decoherence. [Preview Abstract] |
Friday, May 19, 2006 8:48AM - 9:00AM |
S5.00005: Physics collaboration and communication through emerging media: *odcasts, blogs and wikis Charles W. Clark, Jamie Williams The entertainment and news industries are being transformed by the emergence of innovative, internet-based media tools. Audio and video downloads are beginning to compete with traditional entertainment distribution channels, and the blogosphere has become an alternative press with demonstrated news-making power of its own. The scientific community, and physics in particular, is just beginning to experiment with these tools. We believe that they have great potential for enhancing the quality and effectiveness of collaboration and communication, and that the coming generation of physicists will expect them to be used creatively. We will report on our experience in producing seminar podcasts (google ``QIBEC'' or search ``quantum'' on Apple iTunes), and on operating a distributed research institute using a group-based blog. [Preview Abstract] |
Friday, May 19, 2006 9:00AM - 9:12AM |
S5.00006: Storage and retrieval of single photons transmitted between remote quantum memories Stewart D. Jenkins, Thierry Chaneli\`{e}re, Dzmitry Matsukevich, Shau-Yu Lan, Odell A. Collins, Alex Kuzmich, T.A. Brian Kennedy We report the generation, transmission, storage, and retrieval of single photons using two remote atomic ensembles. A single photon is generated from a cold atomic ensemble at one site [1], and is redirected through an optical fiber to another site. The photon is then converted into a single collective atomic excitation using the dark-state polariton approach [2]. After a programmable storage time, the excitation is converted back into a single photon. A reduction in retrieval efficiency is observed as the storage time as increased. This can be understood by generalizing the dark-state polariton theory to account for Zeeman degeneracy and the presence of an ambient magnetic field. During the storage process, the atomic hyperfine coherences rotate, leading to a variation in the dark- state polariton number. For uniform magnetic fields, we predicted and later observed collapses and revivals in the retrieval efficiency for varying storage times. \newline \newline [1] L.-M. Duan, M. D. Lukin, J. I. Cirac, and P. Zoller, Nature \textbf{414}, 413 (2001) \newline [2] M. Fleischhauer and M. D. Lukin, Phys. Rev. Lett. \textbf {84}, 5094 (2000) [Preview Abstract] |
Friday, May 19, 2006 9:12AM - 9:24AM |
S5.00007: Up-Conversion Methods for Multi-dimensional Infrared Spectroscopy Kent Meyer Heterodyned detection methods for recently developed non-linear multi-dimensional infrared ultrafast spectroscopic techniques can provide substantial sensitivity over homodyne methods, but restrictions on phase stability currently only allow this technique to be used with single infrared laser sources and modest pulse widths. For a dual infrared experiment, a frequency-scanned homodyne method was instead performed where this phase restriction is removed. An up-conversion method for the homodyne infrared source using three and four-wave mixing crystals was considered, where surprisingly it was found that sensitivities even higher than the heterodyne method may be achievable. Experimental up-conversion spectra on a model tricarbonylnickel compound show the feasibility of this method and also show a change in cross-peak intensities that is uninterpretable with computer fitting algorithms. [Preview Abstract] |
Friday, May 19, 2006 9:24AM - 9:36AM |
S5.00008: Ultrafast Optical Rabi Oscillations on a Single Ion Martin Madsen, Peter Maunz, David Moehring, Rudy Kohn, Chris Monroe Ultrafast laser interactions with trapped ions open up the possibility to realize scalable, fast quantum logic gates for quantum information applications. In addition, the possibility for fast and efficient excitations from the ground to excited states of trapped ions will benefit probabilistic ion-photon and ion-ion entanglement experiments. We report the measurement of picosecond optical Rabi oscillations, coherently driving the optical S to P transition in a single trapped cadmium ion with near unitary probability. In a microwave Ramsey experiment, two ground state hyperfine levels in a coherent superposition are each driven to unique excited hyperfine levels by an ultrafast laser pulse. Upon spontaneous emission the hyperfine coherence is lost because the frequency of the emitted photon could potentially be measured. However, when a second pulse, delayed by a time shorter than the excited state lifetime, drives the population back towards the ground state, the phase information is preserved. Here, the phase is shifted by the phase accumulated during the time the ion spent in the excited state, evidence for entanglement between the atomic (hyperfine) qubit and the photonic (frequency) qubit. [Preview Abstract] |
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