Bulletin of the American Physical Society
APS March Meeting 2016
Volume 61, Number 2
Monday–Friday, March 14–18, 2016; Baltimore, Maryland
Session X52: Atomic Physics: New Frontiers I 
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Sponsoring Units: DAMOP Room: Hilton Baltimore Holiday Ballroom 3 
Friday, March 18, 2016 8:00AM  8:12AM 
X52.00001: Comparison between two models of timedependent absorption of matter waves Maximilien Barbier, Mathieu Beau, Arseni Goussev The interaction between an atom and a laser might give rise to transitions between two, or more, internal states of the atom. Such processes can be efficiently described within the framework of matter wave absorption, in which the laser beam is mimicked by an absorbing barrier. In this talk we present a quantitative comparison between two models describing the interaction between a nonrelativistic quantum particle and a thin timedependent absorbing barrier. The first model represents the barrier by timedependent discontinuous matching conditions imposed on both the wave function of the particle and its spatial derivative. The second model treats the particle as a spinor submitted to a timedependent offdiagonal $\delta$potential. We show the two models to be in excellent agreement in a semiclassical regime. Reference: M. Barbier, M. Beau, A. Goussev, arXiv:1510.06996, \textit{Phys. Rev. A} (in press). [Preview Abstract] 
Friday, March 18, 2016 8:12AM  8:24AM 
X52.00002: Bell Experiment with Classical Optical Fields Bethany Little, XiaoFeng Qian, John Howell, J. H. Eberly We theoretically and experimentally explore the implications of entanglement in statistically classical optical fields \footnote{X.F. Qian, Bethany Little, John Howell, and J. H. Eberly, Optica {\bf 2}, 611615 (2015).}. The description of these fields in terms of polarization and amplitude degrees of freedom can take a nonseparable form which employs a mathematical description of entanglement often associated with quantum phenomena. By subjecting these optical fields to a Bell analysis, we examine the role of entanglement in marking the quantumclassical boundary. We report a value of the Bell parameter greater than $\cal B$ $ = 2.54$, many standard deviations outside the limit $\cal B$ $ = 2$ established by the ClauserHorneShimonyHolt Bell inequality \footnote{John F. Clauser, Michael A. Horne, Abner Shimony, and Richard Holt. Phys. Rev. Lett. {\bf 23}, 880884 (1969)}. This suggests that Bell violation has less to do with quantum theory than previously thought, but everything to do with entanglement. [Preview Abstract] 
Friday, March 18, 2016 8:24AM  8:36AM 
X52.00003: Nonequilibrium Transport of Light ChiaoHsuan Wang, Jacob Taylor Nonequilibrium Transport of Light The thermalization of light under conditions of parametric coupling to a bath provides a robust chemical potential for light [1]. We study nonequilibrium transport of light using nonequilibrium Green's function approach under the parametric coupling scheme, and explore a potential photonic analogue to the Landauer transport equation. Our results provide understandings of manybody states of photonic matter with chemical potential imbalances. The transport theory of light paves the way for quantum simulation and even practical applications of diodelike circuits using quantum photonic sources in the microwave and optical domain. \\ $[1]$ M. Hafezi, P. Adhikari, J. M. Taylor, arXiv:1405.5821v2 (2014) [Preview Abstract] 
Friday, March 18, 2016 8:36AM  8:48AM 
X52.00004: Determination of Zak phase by reflection phase in 1D photonic crystals Wensheng Gao For a onedimensional (1D) periodic system with inherent mirror symmetry, the value of the geometric ``Zak'' phase in a bulk band is related to the sign of reflection phase for wavelengths inside the bandgaps sandwiching the bulk band. We designed an interference setup which allows us to measure the reflection phase of 1D phonic crystal fabricated for the optical range, and this in turn enabled us to determine the Zak phases of the bands. We then found interface states whose existence can be traced to the topological properties of the bandgaps and the geometric phases of the bulk bands. (accepted by optics letters) [Preview Abstract] 
Friday, March 18, 2016 8:48AM  9:00AM 
X52.00005: Experimental Apparatus for the Observation of the Topological Change Associated with Dynamical Monodromy Daniel Salmon, M. Perry Nerem, Seth Aubin, John Delos Monodromy means “once around a path,” therefore systems that have nontrivial monodromy are systems such that, when taken around a closed circuit in some space, the system has changed state in some way. Classical systems that exhibit nontrivial Hamiltonian monodromy have action and angle variables that are multivalued functions. A family, or loop, of trajectories of this system has a topological change upon traversing a monodromy circuit. We present an experimental apparatus for observing this topological change. A family of particles moving in a cylindrically symmetric champagnebottle potential exhibits nontrivial Hamiltonian monodromy. At the center of this system is a classically forbidden region. By following a monodromy circuit, a loop of initial conditions on one side of the forbidden region can be made to evolve continuously into a loop that surrounds the forbidden region. We realize this system using a spherical pendulum, having at its end a permanent magnet. Magnetic fields generated by coils can then be used to create the champagnebottle potential, as well as drive the pendulum through the monodromy circuit. [Preview Abstract] 
(Author Not Attending)

X52.00006: Topological Charge Screening in Disordered AharonovBohm Wavefunctions Alexander Houston, John Hannay, Alexander Taylor, Mark Dennis Free electrical charges are typically subject to screening relations. For example, in ionic fluids and Coulomb gases there is screening (both global and local) of the electrical charges, described by the first and second StillingerLovett sum rules [1]. A topological analogy governs the statistical behaviour of the nodal points in Gaussian random superpositions of plane waves. These nodal points are integer topological charges, i.e. vortices and antivortices of the complex wavefunction, whose sign is that of the phase circulation. Such superpositions are known to model high energy eigenfunctions in the presence of wave chaos [2], and display topological charge screening in the bulk [3]. We investigate how these screening relations are affected by the introduction of a magnetic flux line [4], which may be fractional in strength. We find that the global screening relation is broken, with the average total topological charge of the vortices given by the flux strength, and that the local screening of the flux itself shows unexpected features. [1] F. H. Stillinger and R. Lovett, J. Chem. Phys. 49, 199194 (1968) [2] M. V. Berry, J. Phys. A 10, 208391 (1977) [3] M. V. Berry and M. R. Dennis, Proc. R. Soc. A 456, 205979 (2000) [4] Y. Aharonov and D. Bohm, Phys. Rev. 115, 48591 (1959) [Preview Abstract] 
Friday, March 18, 2016 9:12AM  9:24AM 
X52.00007: Synthetic gauge flux and Weyl points in acoustic systems. Meng Xiao, Wenjie Chen, WenYu He, C. T. Chan We consider acoustic systems comprising a honeycomb lattice in the xy plane and periodic along the z direction. As kz is a good quantum number here, for each fixed kz, this system can be treated as a reduced twodimensional system. By engineering the interlayer coupling in the zdirection, we show that we can realize effective inversion symmetry breaking and synthetic staggered gauge flux in the reduced twodimensional system. The realizations of chiral edge states for fixed values of kz are direct consequences of the staggered gauge flux. And we then show that the synthetic gauge flux is closely related to the Weyl points in the threedimensional band structure. [Preview Abstract] 
Friday, March 18, 2016 9:24AM  9:36AM 
X52.00008: Atomic collisions, inelastic indeed. Herve Bercegol, Gwenael Ferrando, Roland Lehoucq At the turn of the twentieth century, a hot controversy raged about the ability of Boltzmann's framework to take care of irreversibility. The socalled Loschmidt's paradox progressively faded with time during the last hundred years, due to the predictive efficiency of statistical mechanics. However, one detail at the origin of the controversy  the elasticity of atomic collisions  was not completely challenged. A semiclassical treatment of two atoms interacting with the vacuum zeropoint field permits to predict a friction force acting against the rotation of the pair of atoms [Bercegol H. {\&} Lehoucq R., \textit{Phys. Rev. Lett.} \textbf{115}, 090402 (2015)]. By its form and its level, the calculated torque is a candidate as a physical cause for diffusion of energy and angular momentum, and consequently for entropy growth. It opens the way to a revision of the standard vision of irreversibility. This presentation will focus on two points. First we will discuss the recent result in a broader context of electromagnetic interactions during microscopic collisions. The predicted friction phenomenon can be compared to and distinguished from CollisionInduced Emission and other types of inelastic collisions. Second we will investigate the consequences of the friction torque on calculated trajectories of colliding atoms, quantifying the generation of dimers linked by dispersion forces. [Preview Abstract] 
Friday, March 18, 2016 9:36AM  9:48AM 
X52.00009: Hydrogen Dissociation in Generalized HartreeFock Theory: Breaking the diatomic bond Jonathan Jerke, Samina Masood, CJ Tymczak Generalized Hartree Fock theory predicts molecular Hydrogen dissociation without correlation. A variational GaussianSinc linear superposition is the basis of 50 calculations with 34 significant digits of quality. The spin singlet covalent bond spontaneously breaks into a pair of uncorrelated doublets at atomic separation of 1.22 Angstroms. Quantum spin numbers and energetic comparison with Configuration Interaction theorycorrelationpoint to a first order phase transition in the molecular Hydrogen bond without correlation. [Preview Abstract] 
Friday, March 18, 2016 9:48AM  10:00AM 
X52.00010: Stretching of Picosecond Laser Pulses with Uniform Reflecting Volume Bragg Gratings. Sergiy Mokhov It is shown that a uniform reflecting volume Bragg grating (VBG) can be used as a compact monolithic stretcher of highpower picosecond laser pulses in cases when chirped Bragg gratings with an appropriate chirp rate are difficult to fabricate. A chirpfree reflected stretched pulse is generated of almost rectangular shape when incident short pulse propagates along a grating and experiences local Bragg diffraction. The increase in duration of the reflected pulse is approximately equal to twice the propagation times along the grating. We derived the analytic expression for diffraction efficiency, which incorporates incident pulse duration, grating thickness, and amplitude of refractive index modulation, enabling an optimum selection of the grating for pulse stretching. The typical expected theoretical value of diffraction efficiency is about 10{\%} after taking into account the spectral narrowing of the reflected emission. We believe that the relatively low energy efficiency of the proposed method is more than offset by a number of advantages, which are chirpfree spectrum of a stretched pulse, compactness, robustness, preservation of setup alignment and beam quality, and tolerance to high power. Obtained pulses of several tens of picoseconds can be amplified by standard methods which are not requiring special measures to avoid undesirable nonlinear effects. We propose a simple and reliable method to control the temporal parameters of the highpower picosecond pulses using the same laser source and the VGB of variable thickness that can significantly simplify the experiments requiring different pulse durations. [Preview Abstract] 
Friday, March 18, 2016 10:00AM  10:12AM 
X52.00011: Ablationcooled material removal with ultrafast bursts of pulses F. Ömer Ilday, C. Kerse, H. Kalaycioglu, P. Elahi, S. Yavas, D. Kesim, Ö. Akçaalan, B. Çetin, B. Öktem, M. Asik, H. Hoogland, R. Holzwarth Use of femtosecond pulses allows precise and thermaldamagefree material removal with broad applications. However, its potential is limited by low material removal speeds and complexity of the required lasers. The laser complexity arises from the high pulse energy threshold for ablation. Physics of the lasermaterial interaction precludes a straightforward scaling up of the removal rate by using more powerful lasers due to shielding and collateral damage from heat accumulation. Here, we exploit ablation cooling, a technique used in aerospace engineering since 1950’s, to circumvent this limitation. We apply rapid successions of pulses from specially developed lasers to ablate the target material before the residual heat deposited by previous pulses diffuse away from the interaction region. This constitutes a new physical regime of lasermaterial interactions, where heat removal due to ablation is comparable to conduction. Proofofprinciple experiments demonstrate reduction of required pulse energies by ~1000x, while simultaneously increasing efficiency and speed by ~10x. [Preview Abstract] 
Friday, March 18, 2016 10:12AM  10:24AM 
X52.00012: Formation of ultrashort pulses from monochromatic XUV radiation via interaction with a medium of IRdressed He atoms. Timur Akhmedzhanov, Vladimir Antonov, Olga Kocharovskaya Trains of high intensity ultrashort XUV pulses could find a lot of applications. Recently, a mechanism of high efficiency formation of a train of XUV pulses from quasimonochromatic XUV field was suggested [Opt. Lett. 36, 2296 (2011)]. XUV field propagates through the medium of atoms, which are spacetime modulated by IR field. The field scattered by modulated atoms contains sidebands of incident XUV field frequency and, for properly chosen parameters, train of ultrashort pulses is formed at the output of the medium. In this contribution, we study formation of ultrashort pulses in the medium of He atoms. Contrary to our recent work [Phys. Rev. A 91, 023830 (2015)], IR field is chosen to be weak enough, so that pulses are formed due to modulation of excited atomic levels, rather than tunnel ionization. The suggested method allows to form train of pulses with high efficiency and can be scaled to Helike ions in order to get even shorter pulses. [Preview Abstract] 
Friday, March 18, 2016 10:24AM  10:36AM 
X52.00013: Chiral Molecular Optical Response to NanoShaped Light Prasoon Saurabh, Vladimir Chernyak, Jeremy Rouxel, Shaul Mukamel Chiral linear optical signals are an important spectroscopic tool for biomolecules and chemical sensing applications. Exact expressions are derived which express these signals as a convolution of a nonlocal linear susceptibility of matter with a nonlocal intrinsic property of the electric field. The chiral response can be enhanced and optimized using nanooptical fields with strong spatial variation. The approach is based on a gauge invariant calculation using the minimal coupling Hamiltonian. The multipolar expansion is avoided and all multipoles are naturally incorporated. We apply these expression to achiral (planar) and chiral (dihedral angle of $45^{\circ}$) biphenyl as a physically intuitive illustration. [Preview Abstract] 
Friday, March 18, 2016 10:36AM  10:48AM 
X52.00014: Study of Rydberg blockade mediated optical nonlinearity in thermal vapor Arup Bhowmick, Ashok Mohapatra We demonstrate Rydberg blockade by coupling to Rydberg state via twophoton excitation in rubidium thermal vapor. The probe beam coupling to the $D2$ transition was blue detuned by $1.3$ GHz and a coupling beam was scanned to excite the atoms to Rydberg state via twophoton transition (5s$_{1/2}\longrightarrow n$s$_{1/2}$). The dispersion of the probe beam is modified due to the 2photon excitation and is measured using an optical heterodyne detection technique in the experiment. We have observed that the dispersion of the probe beam depends linearly on atomic vapor density while coupling to a Rydberg state with principal quantum number, $n=30$. However, density dependent suppression of the dispersion is observed while coupling to the Rydberg state with $n = 60$. Since the dispersion of the probe beam due to 2photon excitation depends on the Rydberg population, the density dependent suppression is explained by introducing the concept of blockade. The blockade radius is measured to be about 2.2 $\mu$m which is consistent with the scaling due to Doppler width of the 2photon resonance in thermal vapor. Our result promises the realization of single photon source and strong single photon nonlinearity based on Rydberg blockade in thermal vapor. [Preview Abstract] 
Friday, March 18, 2016 10:48AM  11:00AM 
X52.00015: 'Relativistic' corrections to the mass of a plucked guitar string Michael Kolodrubetz, Anatoli Polkovnikov Quantum systems respond nonadiabaticity when parameters controlling them are ramped at a finite rate. If the parameters themselves are dynamical – for instance the position of a box that defines the boundary of a quantum field – the feedback of these excitations gives rise to effective Newtonian equations of motion for the parameter. For the age old problem of photons in a box, this correction gives rise to a mass proportional to the energy of the photons. We show that a similar correction arises for a classical guitar string plucked with energy $E$; moving clamps at the ends of the string requires inertial mass $m=2 E/c_s^2$, where $c_s$ is the speed of sound. This quasirelativistic effect should be observable in freshman physics level experiments. We then comment on how these simple methods have been readily extended to treat problems such as ramps and quenches of stronglyinteracting superconductors and dynamical trapping near a quantum critical point. [Preview Abstract] 
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