Bulletin of the American Physical Society
2005 Joint Spring Meeting of the Texas Sections of the APS, AAPT, and Zone 13 SPS
Thursday–Saturday, March 3–5, 2005; Nacogdoches, TX
Session AB: APS II |
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Sponsoring Units: TSF Chair: Don Bowen Room: Science Building Room 333 |
Friday, March 4, 2005 1:30PM - 1:54PM |
AB.00001: Euclidean, Lorentzian, and Physical Time Roland Allen, Zorawar Wadiasingh Lorentzian time is the time which occurs in the standard equations of physics, with a different status than a spatial coordinate x. Euclidean time is obtained from Lorentzian time by a Wick rotation in the complex t plane, and enters into the resulting equations exactly in the same way as a spatial coordinate x. It seems obvious that the physical time we experience must be Lorentzian time, and that Euclidean time is just a mathematical artifice which we employ for convenience in calculations. However, Hawking has suggested, in both his popular book (``A Brief History of Time'') and in a more technical context (``Euclidean Quantum Gravity'') that exactly the opposite may be true: Euclidean time may be more fundamental, making quantum mechanics formally identical to statistical mechanics, and Lorenzian time is introduced by human observers because it is more convenient for calculations. We present an argument, based on the path integral formulation of quantum mechanics, which supports this latter point of view. In addition, we propose that the breaking of the symmetry between space and time has a simple cosmological origin. [Preview Abstract] |
Friday, March 4, 2005 1:54PM - 2:06PM |
AB.00002: Temperature difference induced entanglement of a two-level atom and a thermal field Han Xiong, Fuli Li, M.S. Zubairy The interaction of a two-level atom and a field which are both initially prepared in thermal states has been studied by use of the Jaynes-Cummings model. We show that entanglement between the atom and the field can arise when the temperature difference between them are sufficiently large. This entanglement cannot be created when the atom and the field are in thermal equilibrium, however, a unitary transformation can always be applied on the atom to destroy the thermal equilibrium and thus create entanglement. [Preview Abstract] |
Friday, March 4, 2005 2:06PM - 2:18PM |
AB.00003: Cavity QED implementation of Three qubit quantum phase gate Juntao Chang, Suhail Zubairy We describe a three qubit quantum phase gate in which the three qubits are represented by the photons in a three-modes optical cavity. This gate is implemented by passing a four-level atom in a cascade configuration through the cavity. We shall discuss the application of such a quantum phase gate to quantum searching. [Preview Abstract] |
Friday, March 4, 2005 2:18PM - 2:30PM |
AB.00004: Generation of Arbitrary two-Qubit entangled States in Cavity QED Tiegang Di, M. Suhail Zubairy We propose how to prepare arbitrary two-mode entangled photon states using atomic interactions with classical fields and quantized cavity fields. [Preview Abstract] |
Friday, March 4, 2005 2:30PM - 2:42PM |
AB.00005: Propagation of Broad Spectrum Pulse in EIT Medium Qingqing Sun, Yuri Rostovtsev, Jonathan Dowling, M. Suhail Zubairy We investigate the possibility of broad spectrum pulse propagation in an electromagnetically induced transparency (EIT) medium without large distortion. The pulse is separated into different spectrum bands. Each band propagates in an EIT window whose center is adjusted to the band center. After proper phase compensations these bands are recombined. The outcoming pulse suffers little distortion and absorption, compared to the propagation in one EIT window. Using this method we can remove the restriction to pulse width in slow light experiments. [Preview Abstract] |
Friday, March 4, 2005 2:42PM - 2:54PM |
AB.00006: Preservation of non-classicality in the continuous-variable quantum teleportation FuLi Li, Tiegang Di, M. Suhail Zubairy The relation between the P-functions of the input and output states in the protocol of quantum teleportation of continuous variables of an optical field is established. Based on this relation, we find a condition involving the squeezing parameter and the detector efficiency, under which the P-function of the output state becomes the Q-function of the input state such that any non-classical features in the input state will be eliminated in the teleported state. In particular, we notice that if the homodyne detection efficiency is less than 0.5 the teleported field must be classical even if the entanglement in the quantum channel is perfect. [Preview Abstract] |
Friday, March 4, 2005 2:54PM - 3:06PM |
AB.00007: ``Magic-angle'' technique for suppression of inhomogeneous broadening of M\"{o}ssbauer spectra Petr Anisimov, Yury Rostovtsev, Olga Kocharovskaya In this work, we demonstrate ``magic-angle'' technique with respect to Mössbauer spectroscopy. The case of dipole interaction of 57Fe is analyzed. Floquet-state perturbation theory for the RF modulation of the Mössbauer resonance and the concept of effective magnetic field is used to calculate the spectra of the 14.4 keV 57Fe nuclear transition. Our analysis provides physical insight into the technique and defines necessary range of parameters for an experimental realization. [Preview Abstract] |
Friday, March 4, 2005 3:06PM - 3:30PM |
AB.00008: BREAK - AB
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Friday, March 4, 2005 3:30PM - 3:42PM |
AB.00009: Control of ionization rates of H2+ by single cycle pulses timed with respect to molecular motion Andrea Burzo, Alexei Sokolov Photo-ionization with single-cycle pulses is a first step toward studying atomic dynamics on the time scale of electronic motion. Previous work has shown that it is possible to produce a train of identical single cycle pulses, perfectly synchronized with molecular motion and separated by an integer (4 or 9) of molecular periods. These pulse trains can be used for studying multiphoton ionization on a few femtosecond timescale. If the input field frequencies are a multiple of their frequency difference, then processes of different order will interfere, leading to a complex dependence of ions signal for different sub-cycle pulse shapes. We are studying how the ionization probability will change as a result of different time delays between the laser pulses and molecular motion. As a result, one can control the ionization rates by adjusting the arrival of the pulses with respect to the molecular motion. [Preview Abstract] |
Friday, March 4, 2005 3:42PM - 3:54PM |
AB.00010: Ab Initio Calculations for the Structure, Vibrational Frequencies, and Barrier to Planarity of Cyclopentene Abdulaziz Al-Saadi, Jaan Laane Ab initio and DFT calculations have been carried out for the cyclopentene molecule in order to analyze its structure and vibrational frequencies. The structure was calculated with MP2/6-311++G** and MP2/cc-pVTZ basis sets and these predicted puckering angles of 27.1\r{ } and 26.1\r{ }, respectively, as compared to the experimental far-infrared value of 26\r{ }. The barrier to planarity was calculated to be 247 cm$^{-1}$, slightly higher than the 233 cm$^{-1}$ far-infrared value. The calculated vibrational frequencies from DFT-B3LYP/cc-pVTZ were compared to the experimental values for the d$_{0, }$d$_{1}$, d$_{4}$, and d$_{8}$ isotopomers and several vibrational reassignments were made. [Preview Abstract] |
Friday, March 4, 2005 3:54PM - 4:06PM |
AB.00011: Debye Model of Step Wandering Howard Richards, Amber Benson, T.L. Einstein The stiffness of steps on vicinal crystal surfaces is often detemined by fitting experimental step wandering functions to a theoretical form, which is based on a harmonic approximation to the potential experienced by the step. This approximation is analagous to the Einstein model of solids, and it can likewise be improved by a "Debye model" in which the spatial dependence is implicit through the relative positions of neighboring steps. The form of the resulting wandering function will be presented and compared with numerical simulations of the terrace-step-kink model for a range of step interactions. [Preview Abstract] |
Friday, March 4, 2005 4:06PM - 4:18PM |
AB.00012: Principle of Least Action and Gauge Compatibility for a Charged Particle in an Electromagnetic Field Donald H. Kobe The Principle of Least Action is used for a single nonrelativistic charged particle in an external electromagnetic field. The Hamiltonian used requires a choice of gauge for the vector and scalar potentials. The trial wave function used requires a choice of a space- and time-dependent phase that is a gauge choice for the wave function. These two gauge choices may not be compatible. We generalize the original trial function by multiplying it by an arbitrary space- and time-dependent phase factor. When this generalized wave function is used in the principle of least action and the action is varied with respect to the phase, we obtain an equation of continuity. From this equation of continuity we can determine the new phase that is compatible with the gauge of the Hamiltonian. Equivalently, we can determine a new gauge for the potentials in the Hamiltonian that is compatible with the gauge of the original wave function. We apply the method to a charge particle in the electric dipole approximation with a real trial wave function and a Hamiltonian in the Coulomb gauge. For a real trial wave function, the Hamiltonian must have new potentials that are in the electric field gauge. For a Hamiltonian in the Coulomb gauge, the phase of the trial wave function is determined. When the Hamiltonian is time independent and the trial wave function has only time dependence Et in its phase, the principle of least action reduces to the energy variational principle. [Preview Abstract] |
Friday, March 4, 2005 4:18PM - 4:30PM |
AB.00013: Kink Stability of Isothermal Spherical Self-Similar Flow Anzhong Wang, Yumei Wu The problem of kink stability of isothermal spherical self-similar flow in newtonian gravity is revisited. Using distribution theory we first develop a general formula of perturbations, linear or non-linear, which consists of three sets of differential equations, one is in each side of the sonic line, and the other is along it. By solving the equations along the sonic line we find explicitly the stability criterion for the self-similar solutions. When the solutions are smoothly across the sonic line, our results reduce to those of Ori and Piran. To show such obtained perturbations can be matched to the ones in other regions, we study the linear perturbations outside of the sonic line, by taking the solutions obtained along the line as the boundary conditions. After properly imposing other boundary conditions in the space, we are able to show that linear perturbations outside the sonic line, satisfying all the boundary conditions, exist for any given $k$, where $k$ denotes the spectrum of the perturbations obtained along the sonic line. As a result, the complete treatment of perturbations in the whole space does not alter the spectrum obtained by considering only the perturbations along the sonic line. [Preview Abstract] |
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