Bulletin of the American Physical Society
2013 Joint Meeting of the APS Division of Atomic, Molecular & Optical Physics and the CAP Division of Atomic, Molecular & Optical Physics, Canada
Volume 58, Number 6
Monday–Friday, June 3–7, 2013; Quebec City, Canada
Session M4: Atom Optics |
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Chair: Mark Edwards, Georgia Southern University Room: 204 |
Thursday, June 6, 2013 8:00AM - 8:12AM |
M4.00001: Capacitor-resisitor neutral-atom circuits with Bose-Einstein condensates Mark Edwards, Noel Murray, Charles W. Clark Recently the realization of a neutral-atom circuit analogous to an electronic capacitor discharged through a resistor and implemented in a thermal-gas system was reported.\footnote{J.G.\ Lee, et al., {\em Scientific Reports} {\bf 3}, article 1034 (2013).} We present a theoretical study of this system where the ideal gas is replaced with a Bose--Einstein condensate. The condensate dynamics is assumed to obey the Gross--Pitaevskii equation (GPE) and we assume that the condensate is initially trapped in a ring-shaped potential that fits into one well of a ``dumbell''--shaped potential. The dumbell potential consists of two wells connected to each via a rectangular channel. We have investigated the dynamics of the condensate upon its release from the ring--shaped trap. We followed the populations of the right--hand and left--hand wells as functions of time after release. We have carried out these studies for dumbell potentials of various channel lengths and widths. The dynamics were then compared with an analogous electronic circuit model, suggested in Ref. [2], consisting of a capacitor discharging through a resistor. We find good agreement between the circuit model and the GPE dynamics. [Preview Abstract] |
Thursday, June 6, 2013 8:12AM - 8:24AM |
M4.00002: A miniaturized, high flux BEC source for precision atom interferometry Waldemar Herr, Jan Rudolph, Manuel Popp, Ernst M. Rasel Atom chips have proven to be excellent sources for the fast production of ultra-cold gases due to their outstanding performance in evaporative cooling. However, the total number of atoms has previously been limited by the small volume of their magnetic traps. To overcome this restriction, we have developed a novel loading scheme that allows us to produce Bose-Einstein condensates of a few 10$^5$ $^{87}$Rb atoms every two seconds. The apparatus is designed to be operated in microgravity at the drop tower in Bremen, where even higher numbers of atoms can be achieved in the absence of any gravitational sag. Using the drop tower's catapult mode, our setup will perform atom interferometry during nine seconds in free fall. Thus, the fast loading scheme allows for interferometer sequences of up to seven seconds -- interrogation times which are inaccessible for ground based devices. The QUANTUS project is supported by the German Space Agency DLR with funds provided by the Federal Ministry of Economics and Technology (BMWi) under grant number DLR 50WM1131. [Preview Abstract] |
Thursday, June 6, 2013 8:24AM - 8:36AM |
M4.00003: Interferometry with Bose-Einstein condensates in microgravity Ernst Maria Rasel A new field in matter wave optics is emerging, which is based on very long baseline atom interferometry (VLBAI). These interferometers strive to increase the sensitivity by coherently spitting and separating wave packets over macroscopic spatial and temporal scales. Bose-Einstein condensates are the ideal source for performing this kind of interferometry and were exploited for the first time in the extended free fall with a chip-based atom laser for Rubidium. Combining delta kick cooling with BEC we can produce ensembles with energies equal to temperatures falling below one nK. Employing an asymmetric Mach-Zehnder type interferometer we could study over hundreds of milliseconds the coherent evolution of a wave-packet and analyse delta kick cooling with the help of the observed interference fringes. A novel generation of atom chips allows to the fast generation of large condensates of more than 100000 atoms in a shoebox sized setup. This project is supported by DLR 50 WM 0346) and DFG-QUEST. [Preview Abstract] |
Thursday, June 6, 2013 8:36AM - 8:48AM |
M4.00004: Experimental Study of a Bose Superfluid ``Battery'' for Atomtronics Dana Z. Anderson, Seth C. Caliga, Cameron J.E. Straatsma The two component model of superfluids describes a thermo-mechanical force in which a thermal gradient across the fluid causes a counter-propagating flow of the normal and superfluid components, with the superfluid current propagating toward the ``hot'' portion of the container and the normal component towards the ``cold.'' We observe the energy and flux of a Bose-condensed gas flowing over a barrier in a hybrid magnetic and optical trap using a high-resolution atom chip projection and in-trap imaging system. We introduce a thermal gradient using asymmetric cooling of the condensed gas and the resulting thermo-mechanical force induces a supercurrent flow over the barrier. We observe, as expected, that the energy of the atoms emerging from the barrier is determined by the barrier height. We show that, like the ``fountain effect'' seen in liquid helium-4, the energy of the emerging atoms can be many times higher than the chemical potential as well as the thermal energy of the condensate. Through these experiments we establish that a reservoir of Bose-condensed atoms combined with a cooling mechanism can serve as a ``battery'' to drive the current in an atomtronic circuit. [Preview Abstract] |
Thursday, June 6, 2013 8:48AM - 9:00AM |
M4.00005: Interactions of Bright Matter-Wave Solitons with a Barrier Potential Paul Dyke, Jason Nguyen, David Tam, Randall Hulet We study the interaction of a bright matter-wave soliton with a tunnel-barrier. In our experiments, bright matter-wave solitons are formed from Bose-Einstein condensates in a gas of ultracold $^7$Li atoms. We use the broad Feshbach resonance of $^7$Li in the $|1,1\rangle$ state and tune the scattering length through zero to small negative values to form a single bright matter-wave soliton close to the critical number for collapse. We excite the collective dipole mode of a soliton confined to a quasi-1D potential which is formed from a single focused laser beam, with a ratio of radial to axial harmonic frequencies of 60. The soliton interacts with a thin potential barrier formed by a near-resonant, blue detuned, cylindrically focused laser beam that perpendicularly bisects the trapping beam at its focus. Through adjustment of the barrier potential height, the soliton can either be split in two, transmitted or reflected. When the barrier produces splitting, the fragments will undergo a second interaction at the barrier thus realizing the ingredients of a Mach-Zender type interferometer in an attempt to observe coherent recombination. [Preview Abstract] |
Thursday, June 6, 2013 9:00AM - 9:12AM |
M4.00006: Ideal Classical Solitons as a Limit to a Quantum Many-Body System Simon Gardiner, Tom Billam, John Helm, David Holdaway, Christoph Weiss Classical solitons arise as solutions to the one-dimensional nonlinear Schrodinger equation $$ i\frac{\partial}{\partial t}\psi(x,t) = -\frac{1}{2}\frac{\partial^{2}}{\partial x^{2}} \psi(x,t) - |\psi(x,t)|^{2}\psi(x,t), $$ which can be seen as a one-dimensional limiting case of the Gross-Pitaevskii equation, that has been so successful in describing the collective properties and dynamics of atomic Bose-Einstein condensates, for attractively interacting atoms. Solitons are robust to collisions, which makes them of significant interest for matter wave interferometry. We will examine how closely one can approach the one-dimensional, unconfined, classical field description assumed by exact classical soliton solutions, when the physical system exists in three spatial dimensions, and is an interacting quantum many-body system. [Preview Abstract] |
Thursday, June 6, 2013 9:12AM - 9:24AM |
M4.00007: Bose-Einstein condensation of atoms in a uniform potential Robert Smith, Alexander Gaunt, Tobias Schmidutz, Igor Gotlibovych, Zoran Hadzibabic We have observed Bose-Einstein condensation of an atomic gas in the (quasi-)uniform three-dimensional potential of an optical box trap. Condensation is seen in the bimodal momentum distribution and the anisotropic time-of-flight expansion of the condensate. The critical temperature agrees with the theoretical prediction for a uniform Bose gas. The momentum distribution of our non-condensed quantum-degenerate gas is also clearly distinct from the conventional case of a harmonically trapped sample and close to the expected distribution in a uniform system. We confirm the coherence of our condensate in a matter-wave interference experiment. Our experiments open many new possibilities for fundamental studies of many-body physics. [Preview Abstract] |
Thursday, June 6, 2013 9:24AM - 9:36AM |
M4.00008: Exploring the thermodynamics of Bose-Einstein condensation in a homogeneous atomic gas Tobias Schmidutz, Igor Gotlibovych, Alexander Gaunt, Robert Smith, Zoran Hadzibabic Atomic Bose-Einstein condensates have traditionally been produced in harmonic traps and only very recently it became possible to attain condensation in a homogeneous gas [A.L. Gaunt et al., arXiv:1212.4453]. In this talk we will present our new experimental results on the thermodynamics of condensation in a homogeneous weakly interacting Bose gas. We perform a systematic study of the tuning of the critical temperature with system parameters, the saturation of the thermal components in a partially condensed sample, and the total energy of the gas. We also study the dynamics of cooling in a uniform gas. [Preview Abstract] |
Thursday, June 6, 2013 9:36AM - 9:48AM |
M4.00009: Violation of Cauchy-Schwarz inequalities by spontaneous Hawking radiation in resonant boson structures Fernando Sols, Juan R.M. de Nova, Ivar Zapata The violation of a classical Cauchy-Schwarz (CS) inequality is identified as an unequivocal signature of spontaneous Hawking radiation (HR) in sonic black holes. This violation can be particularly large near the nonzero frequency peaks in the radiation spectrum emitted from a resonant boson structure forming a sonic horizon. As a function of the frequency-dependent HR intensity, we analyze the degree of CS violation and the maximum violation temperature for a double barrier structure separating two regions of subsonic and supersonic condensate flow. We also consider the case where the resonant sonic horizon is produced by a space-dependent contact interaction. In some cases, CS violation can be observed by direct atom counting in a time-of-flight experiment. The decisive CS violation cannot occur near the zero-frequency HR peak universally shown by one-dimensional black-hole structures. [Preview Abstract] |
Thursday, June 6, 2013 9:48AM - 10:00AM |
M4.00010: Proposal for demonstrating a Bell inequality violation using condensate collisions Karen Kheruntsyan, Robert Lewis-Swan We propose and theoretically simulate an experiment for demonstrating a Bell inequality violation for massive particles in the matter-wave regime. The proposal is based on realizing an atom-optics analog of the Rarity-Tapster optical experiment: We use entangled atom pairs produced via atomic four-wave mixing in the collision of two dilute-gas Bose-Einstein condensates of metastable helium. This can be regarded as an extension of a recent successful experimental demonstration of violation of the Cauchy-Schwartz inequality in the same process [1]; the extension to a Bell-test is realized via an additional application of a sequence of two laser-induced Bragg pulses acting as a mirror ($\pi$-pulse) and a 50:50 beam splitter ($\pi/2$-pulse). The Bragg pulses implement a two-particle interferometry on the underlying Bell-state involving two pairs of correlated atoms with equal but opposite momenta. The collision dynamics and the sequence of Bragg pulses is simulated using a stochastic (positive-$P$) formulation of the Bogoliubov approach, and we predict the value of the CSHS-Bell parameter $S\simeq2.5$, showing a clear violation of the CSHS-Bell inequality bounded classically by $S\leq2$.\\[4pt] [1] K.V. Kheruntsyan \emph{et al.}, Phys. Rev. Lett. \textbf{108}, 260401 (2012). [Preview Abstract] |
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