Bulletin of the American Physical Society
40th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 54, Number 7
Tuesday–Saturday, May 19–23, 2009; Charlottesville, Virginia
Session X5: Atoms and QED |
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Chair: Irina Novikova, College of William and Mary Room: Clark Hall 107 |
Saturday, May 23, 2009 10:30AM - 10:42AM |
X5.00001: Photon-Photon Entanglement with an Atom-Cavity System Joerg Bochmann, Bernhard Weber, Holger Specht, Martin Muecke, Christian Noelleke, Stephan Ritter, Eden Figueroa, David Moehring, Gerhard Rempe We report on the implementation of a deterministic protocol where a single rubidium atom trapped within a high-finesse optical cavity mediates entanglement between two subsequent photons [1]. First, the atom is entangled with an emitted single photon. After a chosen time, the atomic state is mapped onto a second photon, thus generating an entangled photon pair. The cavity ensures controlled photon generation and high photon collection efficiencies. Compared to previous experiments [2], our single atom trapping scheme allows for the generation of 10$^{5}$ times more entangled photons per atom. We analyze the entanglement and coherence time of the atomic qubit using a Bell inequality measurement and quantum state tomography. A promising application of trapped atom-cavity systems is deterministic photonic coupling of distant atomic qubits [3]. We report on recent progress towards two-photon interference from two independent systems. \newline \newline [1] B. Weber et al., PRL \textbf{102}, 030501 (2009) \newline [2] T. Wilk et al., Science \textbf{317}, 488 (2007) \newline [3] J.I. Cirac et al., PRL \textbf{78}, 3221 (1997) [Preview Abstract] |
Saturday, May 23, 2009 10:42AM - 10:54AM |
X5.00002: Bloch-Zener oscillations of atoms inside an optical cavity Prasanna Venkatesh Balasubramanian, Michael Trupke, Edward Hinds, Duncan O'Dell Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated. We investigate the corresponding behavior of the atoms and the light when the optical lattice is provided by the intra-cavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that their back-action modulates the phase and intensity of the light transmitted through the cavity. We solve the coupled atom-light equations self-consistently and show that, remarkably, the Bloch period is unaffected by this back-action. The transmitted light provides a way to observe the atomic oscillation continuously, allowing very high precision measurements to be derived from a single cloud of atoms. [Preview Abstract] |
Saturday, May 23, 2009 10:54AM - 11:06AM |
X5.00003: Quantum phase transitions, fluctuations, and stripe ordering in many-body cavity QED Benjamin Lev, Sarang Gopalakrishnan, Paul Goldbart An ultracold bosonic gas of atoms, trapped in an optical cavity, crystallizes at either the even or the odd antinodes of the cavity mode if the atoms are pumped with a laser oriented transverse to the cavity axis. For a single-mode cavity, the transition to a crystalline state has been observed [1] and is well described by mean-field theory [2]. However, in multimode cavities, i.e., ring, confocal, and concentric, fluctuations and geometrical effects change the character of the transition and of the ordered state. If the atoms are confined to a quasi-two-dimensional (pancake-shaped) cloud transverse to the pump laser, the ordering transition is a version of Brazovskii's layering transition; since the threshold persists to zero temperature, it is a quantum phase transition of this unusual universality class. We calculate the pump threshold for the single-mode, ring, and concentric cases, and show how the effects of mode structure along the pump direction lead to the formation of domains even at the level of mean field theory. We discuss these phenomena as well as possibilities for detecting a smectic superfluid phase. [1] A.T. Black et al, Phys. Rev. Lett. 91, 203001 (2003). [2] J.K. Asboth et al, Phys. Rev. A 72, 053417 (2005). [Preview Abstract] |
Saturday, May 23, 2009 11:06AM - 11:18AM |
X5.00004: Positioning and measuring atomic gases in a Atom Chip/Cavity QED apparatus Daniel Brooks, Thomas Purdy, Thierry Botter, Dan Stamper-Kurn A Fabry-Perot cavity QED system exhibits a standing-wave cavity mode resulting in spatially-varying atom-light interactions. By confining atoms to less than a half wavelength of the mode, in the Lamb-Dicke regime, the effects of spatially-dependent coupling can be mapped out. For example, measurement backaction induced heating is minimized at anti-nodes whereas position sensitivity is greatest at the maximal gradient of the standing wave. These effects are of interest in contexts of cavity Optomechanics and squeezed interferometry. Here we present our experimental results on long-distance transport of atoms on chips and on measuring quantum motion of atoms strongly coupled to cavities. [Preview Abstract] |
Saturday, May 23, 2009 11:18AM - 11:30AM |
X5.00005: ABSTRACT WITHDRAWN |
Saturday, May 23, 2009 11:30AM - 11:42AM |
X5.00006: Bistable Mott insulator to superfluid phase transition in cavity optomechanics W. Chen, K. Zhang, M. Bhattacharya, D.S. Goldbaum, P. Meystre The central element of most cavity optomechanical systems is a Fabry-P\'{e}rot type cavity with one end-mirror allowed to vibrate about its equilibrium position under the effect of radiation pressure. It has recently been demonstrated that one or more modes of vibration of that mirror can be laser-cooled, and it is expected that cooling to the ground state of vibrational motion will be achieved in the near future. It is also known that these resonators can exhibit radiation-pressure induced optical multistability, whereby a given input intensity can result in two or more values of the output intensity, depending upon the history of the system. In this contribution we show that these combined effects can lead to the realization of opto-mechanically-induced multistable quantum phase transitions between superfluid and Mott insulator states of an ultracold bosonic sample trapped inside the resonator. We discuss experimental conditions under which this effect can be observed. [Preview Abstract] |
Saturday, May 23, 2009 11:42AM - 11:54AM |
X5.00007: Cavity Optomechanics with a Bose-Einstein Condensate Kristian Baumann, Ferdinand Brennecke, Stephan Ritter, Tobias Donner, Christine Guerlin, Tilman Esslinger In our experiment we couple a Bose-Einstein condensate with an ultrahigh-finesse optical cavity. The tremendous degree of control over atomic gases achieved in Bose-Einstein condensates combined with the rich field of cavity quantum electrodynamics opens access to a wealth of new physics. In the dispersive regime, our system realizes a model of cavity optomechanics. This research field typically studies the coupling of the mechanical motion of one of the cavity mirrors to the light field. In our case, the mechanical oscillator is given by a coherent density modulation of the atomic cloud. We have observed this density modulation and strong optical nonlinearities, present at the single photon level. Furthermore our mechanical oscillator naturally starts in its ground state, from which a single motional excitation can cause a shift of the cavity resonance on the order of the cavity linewidth. Our system is promising to study the quantum regime of cavity optomechanics. [Preview Abstract] |
Saturday, May 23, 2009 11:54AM - 12:06PM |
X5.00008: On the Direction of the Casimir Force due to a Dirichlet Scalar Martin Schaden I present a geometrical subtraction scheme for physical and manifestly finite vacuum energy differences. The procedure does not require intermediate regularization and is well suited for numerical studies since it only a good numerical description of the spectral function at low temperatures is needed. This subtraction method combined with the world-line formalism is used to prove that depending on the geometry, the Casimir force due to a massless scalar field satisfying Dirichlet boundary conditions will draw a piston into the neck or toward the bulb of a flask. This is due to competing contributions to the interaction energy from two types of Brownian bridges. The analysis is robust with respect to variations in the shape of both piston and flask. It depends only on differences of finite positive transition probabilities and extends results obtained by reflection positivity to rather involved geometries. In the limit of a flask with a bulb that is large compared the diameter of the neck, the example suggests that atoms are drawn into metallic micro-pores. This can also be qualitatively understood as the net effect of Van der Waals forces on an atom, but the attraction here is related to the change in zero-point energy with boundary conditions. [Preview Abstract] |
Saturday, May 23, 2009 12:06PM - 12:18PM |
X5.00009: Phase Shift of a Weak Coherent Beam by a Single Atom Syed Abdullah Aljunid, Meng Khoon Tey, Brenda Chng, Jianwei Lee, Gleb Maslennikov, Christian Kurtsiefer We report the direct measurement of a phase shift induced by single $^{87}$Rb atom on a focused coherent light field. The atom is localized in an optical tweezer between two confocal ashpheric lenses in one arm of a balanced Mach-Zehnder interferometer. In this arrangement, the light beam passes only once through the atom localization volume. We observe a maximum phase shift of 1$^\circ$ for near-resonant light passing through the interferometer. [Preview Abstract] |
Saturday, May 23, 2009 12:18PM - 12:30PM |
X5.00010: Dispersion Forces and Boundary Effects on Spontaneous Emission Rates of a Harmonic Oscillator Felipe Da Rosa, Tarciro Mendes, Andre Tenorio, Carlos Farina We consider the interaction between a small system modeled by a simple harmonic oscillator (SHO) with a wedge constituted by two semi-infinite perfectly conducting plates and also with a perfect conducting cyllinder. Using a formalism based on a master equation, we compute the van der Waals force on the SHO and also the spontaneous emission rates, for zero and nonzero temperatures. We then discuss some of the consequences of our results and also possible extensions for this work. [Preview Abstract] |
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