Bulletin of the American Physical Society
2011 Annual Meeting of the Four Corners Section of the APS
Volume 56, Number 11
Friday–Saturday, October 21–22, 2011; Tuscon, Arizona
Session K1: AMO II: Cold Atoms, Quantum Information |
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Chair: Alex Cronin, University of Arizona Room: UA Student Union South Ballroom |
Saturday, October 22, 2011 8:30AM - 8:42AM |
K1.00001: Generation and pinning of high winding-number vortices in Bose-Einstein condensates E. Carlo Samson, Kali Wilson, Zachary Newman, Ewan Wright, Brian P. Anderson We demonstrate the creation of pinned vortices with high winding number (up to 11) in Bose-Einstein condensates (BECs) held in high oblate traps. In our method, a pancake-shaped BEC is initially produced in a combined magnetic and optical trap. Using time-varying magnetic fields to translate the location of the BEC with respect to a focused blue-detuned laser beam, we allow the BEC to spiral around the optical barrier until the barrier ends up at the BEC center. We explore the variation of the net winding of the pinned vortices with the duration of spiral trajectory. This procedure may be scaled to larger numbers of pinned vortices and will be useful in studies of superfluid dynamics and vortex interactions. [Preview Abstract] |
Saturday, October 22, 2011 8:42AM - 8:54AM |
K1.00002: Resonance Imaging and Coherent Transport of Atoms in an Optical Lattice Jae Hoon Lee, Enrique Montano, Daniel Hemmer, Ivan Deutsch, Poul Jessen We describe experimental progress towards a resonance imaging protocol for optical lattices, aimed at robust preparation, addressing and transport of atoms with sub-wavelength resolution. Our setup consists of a 3D optical lattice, and a superimposed long-period (40 lattice sites) 1D superlattice that creates a position dependent shift of the transition frequency between two spin states in the ground manifold. We show that isolated planes of atoms can be prepared by flipping resonant spins with a microwave pulse and removing the remaining non-resonant spins. A second microwave pulse in a translated superlattice subsequently allows us to probe these planes with a resolution of better than 270nm. We further show that composite pulse techniques can reduce the sensitivity of the preparation to small variations in the relative position and intensity of the lattices. Finally, we explore the use of microwave pulses to drive coherent motion between lattice sites. [Preview Abstract] |
Saturday, October 22, 2011 8:54AM - 9:06AM |
K1.00003: Quantum State Tomography via Continuous Measurement of Laser Cooled Cesium Atoms Aaron Smith, Brian Anderson, Hector Sosa, Poul Jessen, Carlos Riofrio, Ivan Deutsch Quantum State Tomography (QST) is the process of reconstructing an unknown quantum state from the outcomes of a sufficiently complete series of measurements. To improve the speed and accuracy of QST, we have developed and implemented a new protocol based on weak continuous measurement and dynamical control. In our experiment, an ensemble of Cs atoms are prepared in identical quantum states within the ground hyperfine manifold, driven by a combination of static, rf and $\mu$w magnetic fields, and simultaneously probed by coupling the atomic spin to the polarization of a near-resonant optical probe field. A continuous measurement of the probe polarization yields an informationally complete measurement record that can be inverted to obtain an estimate of the unknown hyperfine state. We have reconstructed the full density matrix for a number of randomly chosen test states, using computer algorithms based either on least squares fitting or compressed sensing. Both approaches perform similarly and reconstruct our test states with an average fidelity around 90\%, limited primarily by errors in the applied drive fields. [Preview Abstract] |
Saturday, October 22, 2011 9:06AM - 9:18AM |
K1.00004: Polarizability measurements of the alkalis using an atom interferometer Ivan Hromada, William Holmgren, Raisa Trubko, Joseph Ronan, Alexander Cronin We discuss our latest static DC polarizability measurements of the alkalis: Li through Cs. Our Mach-Zehnder atom interferometer uses nanogratings to diffract and recombine any atom or molecular beam. Because we use the same machine to measure polarizability of different atoms, we are able to report polarizability ratios (e.g., $\alpha_{Na}/\alpha_{Li}$) with 0.1\% precision. To achieve this precision, we also describe a novel technique called phase chopping to measure the atom beam velocity with 0.05\% precision. [Preview Abstract] |
Saturday, October 22, 2011 9:18AM - 9:30AM |
K1.00005: Quantum Control of the 133Cs Full Hyperfine Ground Manifold Brian Anderson, Aaron Smith, Hector Sosa, Poul Jessen, Carlos Riofrio, Ivan Deutsch Quantum systems with Hilbert space dimension greater than two (qudits) are often considered as carriers of quantum information. The use of qudit systems could prove advantageous for information processing tasks, provided that good laboratory tools for robust qubit manipulation and readout can be developed. We have successfully implemented a protocol for arbitrary state mapping in the 16-dimensional hyperfine ground manifold of the Cesium 133 atom, using only DC, rf and microwave magnetic fields and thus avoiding the photon scattering and decoherence characteristic of schemes that rely on optical fields. Our control waveforms are designed to provide robustness against errors and inhomogeneities in the control fields, and this has allowed us to achieve state mapping fidelities of 98\% or better in the laboratory. We have developed a procedure involving successive applications of state mapping waveforms, allowing us to separate qudit initialization and readout errors from state mapping errors, and thus to reliably measure state mapping fidelities in excess of 99\%. [Preview Abstract] |
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