Bulletin of the American Physical Society
2009 APS March Meeting
Volume 54, Number 1
Monday–Friday, March 16–20, 2009; Pittsburgh, Pennsylvania
Session H16: Matter waves and Quantum Optics |
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Sponsoring Units: DAMOP Chair: Dan Goldbaum, Arizona Room: 317 |
Tuesday, March 17, 2009 8:00AM - 8:12AM |
H16.00001: Matter wave interferometry as a tool for molecule metrology Stefan Gerlich, Michael Gring, Hendrik Ulbricht, Klaus Hornberger, Jens Tuexen, Marcel Mayor, Markus Arndt Kapitza-Dirac-Talbot-Lau interferometry (KDTLI) has recently been established as an ideal method to perform quantum matter wave experiments with large, highly polarizable molecules in an unprecedented mass range of beyond 1000 atomic mass units [1]. Since the interference visibility reveals important information on the properties of the examined particles, such as their mass and polarizability, we identified KDTLI as a valuable tool for precision metrology. We demonstrate that quantum interferometry can therefore also serve as a powerful complement to mass spectrometry [2], in particular in cases where fragmentation may occur in the detector. Our new method is applicable to a wide range of molecules and is particularly valuable for characterizing neutral molecular beams.\\ ~[1] S. Gerlich, L. Hackerm\"uller, K. Hornberger, A. Stibor, H. Ulbricht, M. Gring, F. Goldfarb, T. Savas, M. M\"uri, M. Mayor, M. Arndt, Nat. Phys. 2007, 3, 711 – 715.\\ ~[2] Stefan Gerlich, Michael Gring, Hendrik Ulbricht, Klaus Hornberger, Jens T\"uxen, Marcel Mayor, and Markus Arndt, Angew. Chem. Int. Ed. 2008, 47, 6195 - 6198. [Preview Abstract] |
Tuesday, March 17, 2009 8:12AM - 8:24AM |
H16.00002: Poisson's Spot with Molecules Thomas Reisinger, Amil Patel, Herbert Reingruber, Katrin Fladischer, Wolfgang E. Ernst, Gianangelo Bracco, Henry I. Smith, Bodil Holst In the Poisson-Spot experiment, waves emanating from a source are blocked by a circular obstacle. Due to their positive on-axis interference an image of the source (the Poisson spot) is observed within the geometrical shadow of the obstacle. The Poisson spot is the last of the classical optics experiments to be realized with neutral matter waves. In this paper we report the observation of Poisson's Spot using a beam of neutral deuterium molecules. The wavelength-independence and the weak constraints on angular alignment and position of the circular obstacle make Poisson's spot a promising candidate for applications ranging from the study of large-molecule diffraction and coherence in atom-lasers to patterning with large molecules. [Preview Abstract] |
Tuesday, March 17, 2009 8:24AM - 8:36AM |
H16.00003: The Two-Mode Approximation in a Realistic Bose-Josephson Junction in a $^{85}$Rb/$^{87}$Rb BEC Mixture Jeffrey Heward, Mark Edwards, Charles Clark We have studied the behavior of an experimentally realistic Bose-Einstein condensate (BEC) mixture subjected to a double-well potential. The mixture studied consists of $^{87}$Rb and $^{85}$Rb held in an optical trap with an external magnetic field that enables tuning of the $^{85}$Rb--$^{85}$Rb scattering length. This system, without the external double--well potential, has been implemented at JILA [S.B.\ Papp, et al, Phys.Rev.Lett.\ {\bf 101}, 040402 (2008)]. A double--well potential can be added to this system by applying another pair of lasers as was done in a previous experiment for single condensates [M.\ Albiez, et al, Phys.\ Rev.\ Lett.\ {\bf 95}, 010402 (2005)]. We have used the Variable Tunneling Model (VTM) within the two--mode approximation to search for novel condensate mixture behavior in this experimentally accessible system. Possible behaviors include Bose--Josephson oscillations with both swapping and non--swapping modes and macroscopic quantum self--trapping with zero and pi modes as described in a recent paper [I.\ Satija, et al, arXiv:0811.1921v1 [quant-ph]]. We compare the behavior as predicted by the two--mode VTM with the solution obtained by integrating the coupled Gross--Pitaevskii equations. We propose some new experiments designed to observe these novel phenomena. [Preview Abstract] |
Tuesday, March 17, 2009 8:36AM - 8:48AM |
H16.00004: Spin-orbit coupled Bose-Einstein condensates Brandon Anderson, Tudor Stanescu, Victor Galitski We consider a Bose-Einstein condensate (BEC) of cold atoms with an internal pseudo-spin-1/2 degree of freedom that is coupled to momentum. The pseudo-spin degree of freedom emerges from the trapped multi-level atoms moving in the presence of spatially modulated laser fields. Within a so-called tripod scheme, the atom-laser interaction generates a pair of degenerate dark states. Upon adiabatically projecting onto the dark states subspace, an effective Hamiltonian emerges with a spin-orbit coupled pseudo-spin-1/2 degree of freedom. For a symmetric, Rashba-type spin orbit interaction the ground state of the pseudo-spin space is continuously degenerate along a circle in momentum space and may lead to many-body states with nontrivial topological properties. We investigate the Rashba-type spin-orbit BEC in the presence of weak density-density interactions. [Preview Abstract] |
Tuesday, March 17, 2009 8:48AM - 9:00AM |
H16.00005: Spin Squeezing in Spinor Condensates Sabrina Leslie, Jay Sau, Marvin Cohen, Dan Stamper-Kurn Spin squeezing in spinor condensates enables the control of quantum spin fluctuations in a fascinating multi-mode system. Further, it provides a coherent spin system characterized by sub-shot-noise spin fluctuations, with applications towards sensitive spatially-resolved magnetometry. With the application of appropriate unitary transformations, we show that one may manipulate the spin fluctuation modes atop an arbitrary F=1 coherent state, and in so doing prepare an arbitrary F=1 spin squeezed state. Taking into account experimental limitations to spin squeezing such as atom loss and nonlinear interactions in the condensate, we find that one may achieve roughly 17 dB of spin squeezing in the single mode regime and 10 dB of spin squeezing in the multi mode regime, for reasonable experimental parameters. [Preview Abstract] |
Tuesday, March 17, 2009 9:00AM - 9:12AM |
H16.00006: Squeezing and entanglement in a Bose-Einstein condensate Christian Gross, Jerome Esteve, Stefano Giovanazzi, Andreas Weller, Markus Oberthaler We report on the observation of spin squeezing and entanglement in a Bose-Einstein condensate trapped in double well and periodic potential [1]. The measurement of two conjugate variables - atom number difference and relative phase between adjacent sites - allows a direct connection to the presence of entanglement. The observations indeed confirm that entanglement is present even at finite temperature. The observed coherent spin squeezing of 3.8 dB implies that a usable quantum resource has been generated which is directly applicable to overcome the standard quantum limit of atom interferometry. The limitations due to experimental imperfections, finite temperature and three body loss will be discussed in detail. Latest results on spin squeezing using hamiltonian dynamics of internal states are presented. [1] J. Esteve, C. Gross, A. Weller, S. Giovanazzi and M. K. Oberthaler: Nature 455, 1216-1219 [Preview Abstract] |
Tuesday, March 17, 2009 9:12AM - 9:24AM |
H16.00007: Creation of resilient entangled states and a resource for measurement-based quantum computation with optical superlattices Andreas Nunnenkamp, Benoit Vaucher, Dieter Jaksch We investigate how to create entangled states with ultracold bosonic atoms trapped in optical lattices by dynamical manipulation of the shape of the lattice potential. We consider a period-two superlattice that allows both the splitting of each site into a double-well potential and also the variation of the height of the potential barrier between the sites. We show how to use this array of double-well potentials to entangle neighboring qubits encoded on the Zeeman levels of the atoms, without using the different vibrational states of the atoms. Finally, we present a method of realizing a Bell-pair encoded cluster state, a resource for measurement-based quantum computing which remains resilient to collective dephasing noise throughout the computation [NJP 10, 023005 (2008)]. [Preview Abstract] |
Tuesday, March 17, 2009 9:24AM - 9:36AM |
H16.00008: ABSTRACT WITHDRAWN |
Tuesday, March 17, 2009 9:36AM - 9:48AM |
H16.00009: Numerical Model of Polariton Dynamics in~GaAs Quantum Well-Microcavity Structures Vincent Hartwell, David Snoke, Ryan Balili Recent experimental results from GaAs quantum well-microcavity structures show evidence for Bose-Einstein condensation of polaritons. A main indicator of this is a large accumulation of polaritons near k=0 above a critical density threshold. The polariton gas is never in complete equilibrium, however. To model the system, we therefore cannot use an equilibrium model for the momentum distribution; instead, we have developed numerical methods for solving the quantum Boltzmann equation for the polariton momentum distribution, including the effects of polariton-polariton scattering, polariton-phonon scattering, and polariton scattering with free electrons. The model allows direct comparison to experimental results. An unexpected experimental result which we address in our modeling is that at very low densities, the polariton momentum distribution is invariant and independent of density. At high densities, our numerical model predicts the accumulation of polaritons at k=0 is indeed the result of the boson statistics of the particles, and though it is not in complete equilibrium, it has the characteristics of a ``quasicondensate.'' [Preview Abstract] |
Tuesday, March 17, 2009 9:48AM - 10:00AM |
H16.00010: Single vortex-antivortex pair in an exciton polariton condensate Georgios Roumpos, Sven Hoefling, Alfred Forchel, Yoshihisa Yamamoto We report the observation of a single vortex-antivortex pair in a two-dimensional exciton polariton condensate. The pairs are evidenced in the time-integrated phase maps acquired using Michelson interferometry. The striped pattern of the sample disorder potential prevents rotation of the pairs, but allows their translational movement. [Preview Abstract] |
Tuesday, March 17, 2009 10:00AM - 10:12AM |
H16.00011: Rabi oscillations in semiconductor multiwave response Mikhail Erementchouk, Michael Leuenberger We study the semiconductor response with respect to high intensity resonant excitation on short time scale when the contribution of the Fermi statistics of the electrons and holes prevails. Both the single and double pulse excitations are considered in the framework of asymptotically exact description. For the double pulse excitation we consider the time evolution of the multiwave mixing (MWM) exciton polarization. The main difference between the excitation by a single pulse or by two non-collinear pulses is that the Rabi oscillations of the MWM response are characterized by two harmonics. The operator dynamics governed by the external excitation exhibits three invariant spin classes, which do not mix with the evolution of the system. Two classes correspond to the bright exciton states and one contains all dark states. The dynamics of the classes turn is described by six characteristic frequencies and the Rabi frequencies (RF) are only two of them (one for each bright class). We show that if initially the system is in the ground state then the semiconductor Bloch equation preserves the invariant spin classes thus proving absence of the dark excitons in the framework of this description. We found that due to the mass difference between holes of different kind two additional RF's, presenting in the operator dynamics, should appear in the evolution of the exciton polarization. [Preview Abstract] |
Tuesday, March 17, 2009 10:12AM - 10:24AM |
H16.00012: Single-atom trajectories of intermittent fluorescence with quantum jumps Patrick Coles, Robert Griffiths Understanding the trajectories of single quantum systems is a modern theoretical challenge, given that experiments are no longer restricted to ensemble-averaged dynamics. Here, we present a model for a single 3-level atom driven resonantly on two transitions, resulting in intermittent fluorescence from one transition. The consistent histories formalism provides insight into the intermittent ``shelving'' process and predicts the distribution of dark periods for a given trajectory. We further predict quantum interference that leads to oscillations in the quantum-jump probability and discuss the possibility of observing these oscillations experimentally. [Preview Abstract] |
Tuesday, March 17, 2009 10:24AM - 10:36AM |
H16.00013: Dynamics and fidelity of entanglement of photons coupled to optical fibers and waveguides Bereket Berhane We investigate the time evolution of the quantum mechanical states of photon-modes in optical fibers and waveguides starting from a multipolar coupling of neutral atoms with a quantized electromagnetic field. We apply our results to the propagation of entangled photons in optical fibers and investigate the fidelity of entanglement for various optical fiber lengths. Furthermore, we obtain a quantum input-output formalism in three dimensions and investigate the dependence of coupling and transfer efficiency on the quantum state of the incident photons. We apply our results to the coupling and propagation of entangled photons for applications in quantum memory transfer over optical fibers and waveguides. [Preview Abstract] |
Tuesday, March 17, 2009 10:36AM - 10:48AM |
H16.00014: Quantum fluctuations in small lasers Kaushik Roy Choudhury, Stephan Haas, A.F.J Levi Master equations are used to demonstrate the dominant role of quantum fluctuations in determining the steady-state and transient response of a laser when there is a small number of particles in the system. In this regime, quantum fluctuations are found to suppress the lasing threshold and create a non-Poisson probability distribution for $n$ discrete excited electronic states and $s$ discrete photons. The correlation between $n$ and $s$ damps the averaged dynamic response of laser emission. Random walk calculations verify the master equation predictions and are used to connect to systems containing larger numbers of particles. [Preview Abstract] |
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