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 C1: DAMOP Thesis Prize |
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Chair: Alex Cronin, University of Arizona Room: Chemistry Building 402 |
Wednesday, May 20, 2009 2:00PM - 2:30PM |
C1.00001: Few-body physics in ultracold gases Invited Speaker: The physics of few body systems plays a fundamental role in the understanding of ultracold atoms loaded in traps or optical lattices. Whereas the ultracold three-body physics can be considered to a large extent as understood, the next step in complexity --four interacting particles-- remains largely unsolved. My talk presents new solutions of the challenging four-body problem, focusing mainly on the behavior of strongly interacting fermions and bosons. These accurate solutions are extended to different regimes and systems by combining a number of powerful numerical techniques: correlated -Gaussian basis-set expansion, diffusion Monte Carlo and the hyperspherical method. First, the spectrum and dynamics are analyzed for two spin-up and two spin-down fermions in the ``BCS-BEC'' crossover, which reveals the nature of dimer-dimer interactions. The calculations at unitarity show that systems with up to N=6 particles follow universal behavior that manifests in the spectrum and wave functions. The calculations are then extended to larger systems, which connects few- and many-body physics. Next, in the context of the four-boson problem, the four-body physics is shown to be intimately related to three-body Efimov physics, which leads to a universal picture for bosons and makes concrete predictions of dimer-dimer collisions and four-body recombination processes. [Preview Abstract] |
Wednesday, May 20, 2009 2:30PM - 3:00PM |
C1.00002: The Strontium Optical Lattice Clock: Optical Spectroscopy with Sub-Hertz Accuracy Invited Speaker: Atomic clocks find significant roles in a number of scientific and technological settings. One interesting approach to a next-generation clock based on an optical transition uses atomic strontium confined in an optical lattice. The tight atomic confinement eliminates motional effects which otherwise trouble the atomic interrogation. At the same time, the optical lattice is equally perturbs the two electronic clock states so that the confinement introduces a net zero shift of the natural transition frequency. Here I describe the design and realization of an optical frequency standard using $^{87}$Sr confined in a 1-D optical lattice. With an ultra-stable laser light source, atomic spectral linewidths of the optical clock transition are observed below 2 Hz. High accuracy spectroscopy of the clock transition is carried out utilizing a frequency comb referenced to the NIST-F1 Cs fountain. To explore the performance of an improved, spin-polarized Sr standard, a coherent optical phase transfer link is established between JILA and NIST. This enables remote comparison of the Sr standard against optical standards at NIST. The high frequency stability of a Sr-Ca comparison (3x10$^{-16}$ at 200 s) is used to make measurements of Sr transition frequency shifts at the fractional frequency level below 10$^{-16}$. These systematic shifts are discussed in detail, resulting in a total uncertainty of the Sr clock frequency at 1.5x10$^{-16}$, the smallest for a neutral atom system. [Preview Abstract] |
Wednesday, May 20, 2009 3:00PM - 3:30PM |
C1.00003: Pairing of Fermionic $^6$Li Throughout the BEC-BCS Crossover Invited Speaker: Studies of ultracold gases of fermionic atoms have led to discoveries that have exceeded even the high expectations that followed the creation of the first degenerate atomic Fermi gas ten years ago. One experimental tool in particular, the Feshbach resonance, has enabled much of this progress by providing an experimental means to tune interactions and facilitate pairing within gases of trapped atoms. In this talk, I will present an experiment that explores the underlying mechanisms behind such resonances as well as experiments that take advantage of their effects. First, I will describe a quantitative measurement of the closed-channel molecular state contribution to the many body state of paired $^6$Li atoms within a broad Feshbach resonance. This measurement, based upon optical molecular spectroscopy, refines the theoretical understanding of such resonances and, moreover, provides clear evidence for pairing across the BEC-BCS crossover and into BCS regime. Next, I will describe studies of polarized Fermi gases with unequal numbers of two pairing constituents. In this system, we find that the gas phase- separates into a uniformly paired superfluid core bordered by regions of normal, unpaired atoms. At the lowest temperatures, this separation is accompanied by a spatial deformation of the core that persists to large imbalance. In this case, we find that an elongated trap geometry appears to favor superfluidity. At higher temperature, the core remains unpolarized up to a critical polarization, but does not deform. Such measurements of pairing in a polarized Fermi gas may be relevant to predictions of exotic phases of quark matter and magnetized superconductors. [Preview Abstract] |
Wednesday, May 20, 2009 3:30PM - 4:00PM |
C1.00004: Quantum Noise and Radiation Pressure Effects in High Power Optical Interferometers Invited Speaker: Opto-mechanical coupling plays an important role in interferometric gravitational-wave detectors and other high-precision displacement and force measurements. In the work presented here, both theoretical and experimental studies of opto-mechanical effects and the quantum limits associated with them are performed in a variety of optical systems. Most notably, two optical fields are used to form a stable all-optical trap for a 1 gram mirror. The optical forces extract energy from the oscillator, and the oscillator is cooled to a greater degree than possible with cavity cooling or cold damping alone. The 1 gram mirror is cooled to $6.9$ mK, and using a similar technique, a $2.7$ kg oscillator from a LIGO interferometer is cooled to $1.4\mathrm{\mu K}$. The opto-mechanical techniques may also generate squeezed light, entanglement, and be used to approach the ground state of motion of the oscillator. With further improvements, these devices may allow the quantum-classical transition to be explored in macroscopic objects. [Preview Abstract] |
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