Bulletin of the American Physical Society
2007 Joint Fall Meeting of the Texas Sections of the APS and AAPT; Zone 13 of SPS
Volume 52, Number 16
Thursday–Saturday, October 18–20, 2007; College Station, Texas
Session B2: AMO1: Atomic, Molecular and Optical Physics |
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Chair: Olga Kocharovskaya, Texas A&M University Room: Rudder Tower 501 |
Friday, October 19, 2007 10:40AM - 10:52AM |
B2.00001: Coherent Control of Trapped Bosons Analabha Roy, Linda Reichl We investigate the quantum behavior of a mesoscopic two-boson system produced by number-squeezing ultracold gases of alkali metal atoms. The quantum Poincare maps of the wavefunctions are affected by chaos in those regions of the phase space where the classical dynamics produces features that are comparable to $\hbar$. We also investigate the possibility for quantum control in the dynamics of excitations in these systems. Controlled excitations are mediated by pulsed signals that cause Stimulated Raman Adiabatic passage (STIRAP) from the ground state to a state of higher energy. The dynamics of this transition is affected by chaos caused by the pulses in certain regions of the phase space. A transition to chaos can thus provide a method of controlling STIRAP. [Preview Abstract] |
Friday, October 19, 2007 10:52AM - 11:04AM |
B2.00002: Fluorescence Spectroscopy and Self-similar Expansion Studies in Ultracold Neutral Plasmas Jose Castro, Hong Gao, Priya Gupta, Sampad Laha, Clayton Simien, Thomas Killian Ultracold Neutral Plasmas (UNP's) are created by photoionizing laser-cooled atoms; the resulting plasma expands due to the thermal pressure of the electrons. Powerful optical diagnostics are available to study these systems where the initial density profiles, energies, and ionization states are accurately known and controllable. Fluorescence imaging of UNP's produces a spatially-resolved spectrum that is Doppler-broadened due to thermal ion velocity and shifted due to ion expansion velocity. Using this technique, measurements of the ion kinetic energy and plasma size show that the expansion is self-similar, following an analytic solution of the Vlasov equations, the central equations in the kinetic theory of plasmas. [Preview Abstract] |
Friday, October 19, 2007 11:04AM - 11:16AM |
B2.00003: Coherent Slowing of a Pulsed Supersonic Beam with an Atomic Paddle Isaac Chavez, Edvardas Narevicius, Adam Libson, Max Riedel, Christian Parthey, Uzi Even, Mark Raizen We report the slowing of a supersonic beam by elastic reflection from a receding atomic mirror. Supersonic beams, formed by the adiabatic expansion of high pressure gas through an aperture, are currently the highest brightness sources available and have a high degree of monochromaticity. We use a pulsed supersonic nozzle to generate a 511 $\pm $ 9 m/s beam of helium that we slow by reflection from a Si(111)-H(1x1) crystal placed on the tip of a spinning rotor. We are able to continuously reduce the velocity of helium by 246 m/s and show that the temperature of the slowed beam is lower than 250 mK in the co-moving frame. We plan to use this beam as a probe for surface science studies and as the source for atom optics and interferometry experiments. The slow, cold, and intense nature of the beam should open new energy ranges and resolutions, allowing higher precision measurements. [Preview Abstract] |
Friday, October 19, 2007 11:16AM - 11:28AM |
B2.00004: Fluctuations of Particle Number in Two-component Interacting Bose-Einstein Condensate. Andrii Sizhuk, Anatoly Svidzinsky, Marlan Scully We study equilibrium fluctuations of particle number in the two-component weakly interacting Bose-Einstein condensate (BEC). Using Bogoliubov theory we obtain analytical expressions for the particle distribution function and fluctuations. We discuss several particular cases, namely, zero-temperature limit and the Thomas-Fermi regime. We study in detail the vicinity of the quantum phase separation transition where fluctuations undergo dramatic variation. We plot the temperature dependence of the first central moments of the condensate distribution function for the two-component interacting BEC and compare it with the one-component condensate. [Preview Abstract] |
Friday, October 19, 2007 11:28AM - 11:40AM |
B2.00005: Single-Photon Atomic Cooling Travis Bannerman, Gabriel Price, Kirsten Viering, Ed Narevicius, Mark Raizen We report on a new method of laser cooling and phase space compression which does not rely on the momentum transfer between many photons and an atom. Whereas most laser cooling techniques (e.g. Doppler cooling, optical molasses, Raman cooling) require a cycling transition to allow for the scattering of many photons, our technique scatters on average only one photon from each atom. This is advantageous because the technique is not limited to the small subset of atoms in the periodic table which possess a cycling transition. The technique may potentially be extended to the cooling of polar molecules and atomic hydrogen. [Preview Abstract] |
Friday, October 19, 2007 11:40AM - 11:52AM |
B2.00006: Optical Pumping in Ultracold Neutral Plasma. Hong Gao, Jose Castro, Clayton E. Simien, Sampad Laha, Thomas C. Killian We have studied the optical pumping by using fluorescence imaging in an ultracold neutral plasma (UNP). Velocity-changing collisions (VCC) have been observed during the optical pumping process. The collision causes the ions to quickly exchange momenta with their neighborhood and are optically pumped from ground state. We present our experimental data and discuss the VCC effect implications for laser cooling of a UNP. [Preview Abstract] |
Friday, October 19, 2007 11:52AM - 12:04PM |
B2.00007: Phase Diagram of a Polarized Fermi Gas Across a Feshbach Wenhui Li, Yean-an Liao, Guthrie B. Partridge, R.G. Hulet We investigate a Fermi gas of $^6$Li atoms with unbalanced populations in two spin states, whose interactions are tuned by a Feshbach resonance. At the unitarity limit, we observe three distinct phases connected by a tricritical point on a polarization vs. temperature (\textit{P}-\textit{T}) phase diagram: a phase-separated state at low \textit{T}, a polarized superfluid and a polarized normal gas at higher \textit{T}. We are currently mapping out the phase diagram as a function of \textit{P}, \textit{T} and interaction. At \textit{T} = 0, as the interaction strength is tuned toward the BEC side of the resonance, we expect to encounter a phase boundary between the phase-separated state and the polarized superfluid. Conversely, on the BCS side, for finite \textit{P}, a transition to the polarized normal gas is expected. We will present our latest results. [Preview Abstract] |
Friday, October 19, 2007 12:04PM - 12:16PM |
B2.00008: Pulsed Magnetic Slowing of Atoms and Molecules Christian G. Parthey, Edvardas Narevicius, Adam Libson, Julia Narevicius, Isaac Chavez, Uzi Even, Mark G. Raizen Supersonic beams are a high brightness source of atoms and molecules. Although the atoms' temperature in the co-moving frame is in the sub-kelvin range their velocity is on the order of several hundreds of meters per second. We report the experimental demonstration of a novel method to slow atoms and molecules with permanent magnetic moments using pulsed magnetic fields. The method is suitable for most atoms since most elements are paramagnetic, and can also be applied to certain molecules as well as electronically excited metastable states. We show the feasibility of this technique by slowing a supersonic beam of metastable neon from (461.0 $\pm $ 7.7) m/s to (403 $\pm $ 16) m/s in 18 stages. [Preview Abstract] |
Friday, October 19, 2007 12:16PM - 12:28PM |
B2.00009: Quantum Contextuality and Einsteinian Realism Brian La Cour Contextuality is a phenomenon predicted to be exhibited by quantum systems and at variance with Einsteinian realism, which is said to be noncontextual. The Kochen-Specker theorem, and its many variants, purports to prove this inconsistency. Recently, the question has been put to experiment [e.g., Hasegawa et al., PRL 97, 230401 (2006)], and the findings are consistent with quantum theoretic predictions. I will argue that, in fact, there is no such inconsistency. Specifically, a proof is offered which demonstrates that quantum mechanics is consistent with a noncontextual hidden variable theory, thus refuting the Kochen-Specker theorem. (For simplicity, the proof is restricted to a four-dimensional Hilbert space but is expected to generalize.) The key to the proof is the recognition of a subtle but fundamentally important assumption regarding the dependence of the hidden variable probability distribution on the particular set of mutually commuting observables chosen for measurement. [Preview Abstract] |
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