1,641 research outputs found

    Cavity atom optics and the `free atom laser'

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    The trap environment in which Bose-Einstein condensates are generated and/or stored strongly influences the way they interact with light. The situation is analogous to cavity QED in quantum optics, except that in the present case, one tailors the matter-wave mode density rather than the density of modes of the optical field. Just as in QED, for short times, the atoms do not sense the trap and propagate as in free space. After times long enough that recoiling atoms can probe the trap environment, however, the way condensates and light fields are mutually influenced differs significantly from the free-space situation. We use as an example the condensate collective atomic recoil laser, which is the atomic matter-wave analog of the free-electron laser.Comment: To be published in a special edition of Optics Communications in honor of the 60th birthday of Marlan Scull

    The Seasonal Nutrient Density of Country Food Harvested in Makkovik, Labrador

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    The contribution of country food to the diets of residents of Makkovik, Labrador, reflects the seasonal availability of different species on the northern Labrador coast. The nutrient density of the wild food component of the food supply varies from season to season according to the relative contribution of the various species harvested. In the summer, the level of calcium is somewhat higher than in most other seasons, reflecting the large contribution of fish. In early fall, the nutrient density for iron is the lowest for all seasons, and the level of calcium decreases to about half of that of summer. In late fall, the nutrient density of the country food harvested for household use has the highest density of thiamin, reflecting the contribution from the migratory birds, and the second highest density of iron, reflecting the increase in percentage contribution of seals. In winter the iron density is approximately twice that of other seasons. The level of calcium increases, reflecting the contribution from partridge and ptarmigan. In early spring the large contribution of caribou provides a high protein content, while for riboflavin it is the highest of any season. In late spring the nutrient density reflects the large percentage of fish. Dietary patterns of a population depending on country food for much of its food supply change from one season to another, and nutrient intakes also vary from season to season. These factors must be considered when evaluating dietary intakes and making nutritional inferences.Key words: country food, nutrient density, nutrition, Subarctic, LabradorMot clés: denrées locales, composition nutritive, nutrition, subarctique, Labrado

    Atomic interaction effects in the superradiant light scattering from a Bose-Einstein condensate

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    We investigate the effects of the atomic interaction in the Superradiant Rayleigh scattering from a Bose-Einstein condensate driven by a far-detuned laser beam. We show that for a homogeneous atomic sample the atomic interaction has only a dispersive effect, whereas in the inhomogeneous case it may increase the decay of the matter-wave grating.Comment: 12 pages, 4 figures, presented to the XII International Laser Physics Workshop, August 24-29, Hamburg, to be published in Laser Physic

    Creating Bell states and decoherence effects in quantum dots system

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    We show how to improve the efficiency for preparing Bell states in coupled two quantum dots system. A measurement to the state of driven quantum laser field leads to wave function collapse. This results in highly efficiency preparation of Bell states. The effect of decoherence on the efficiency of generating Bell states is also discussed in this paper. The results show that the decoherence does not affect the relative weight of 00>|00> and 11>|11> in the output state, but the efficiency of finding Bell states.Comment: 4 pages, 2figures, corrected some typo

    Recoil-Induced-Resonances in Nonlinear, Ground-State, Pump-Probe Spectroscopy

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    A theory of pump-probe spectroscopy is developed in which optical fields drive two-photon Raman transitions between ground states of an ensemble of three-level Λ\Lambda atoms. Effects related to the recoil the atoms undergo as a result of their interactions with the fields are fully accounted for in this theory. The linear absorption coefficient of a weak probe field in the presence of two pump fields of arbitrary strength is calculated. For subrecoil cooled atoms, the spectrum consists of eight absorption lines and eight emission lines. In the limit that χ1χ2\chi_{1}\ll \chi_{2}, where χ1\chi_{1} and χ2\chi_{2} are the Rabi frequencies of the two pump fields, one recovers the absorption spectrum for a probe field interacting with an effective two-level atom in the presence of a single pump field. However when χ1χ2\chi_{1}\gtrsim \chi_{2}, new interference effects arise that allow one to selectively turn on and off some of these recoil induced resonances.Comment: 30 pages, 8 figures. RevTex. Submitted to Phys. Rev. A, Revised versio

    Higher-order mutual coherence of optical and matter waves

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    We use an operational approach to discuss ways to measure the higher-order cross-correlations between optical and matter-wave fields. We pay particular attention to the fact that atomic fields actually consist of composite particles that can easily be separated into their basic constituents by a detection process such as photoionization. In the case of bosonic fields, that we specifically consider here, this leads to the appearance in the detection signal of exchange contributions due to both the composite bosonic field and its individual fermionic constituents. We also show how time-gated counting schemes allow to isolate specific contributions to the signal, in particular involving different orderings of the Schr\"odinger and Maxwell fields.Comment: 11 pages, 2 figure

    Input-output theory for fermions in an atom cavity

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    We generalize the quantum optical input-output theory developed for optical cavities to ultracold fermionic atoms confined in a trapping potential, which forms an "atom cavity". In order to account for the Pauli exclusion principle, quantum Langevin equations for all cavity modes are derived. The dissipative part of these multi-mode Langevin equations includes a coupling between cavity modes. We also derive a set of boundary conditions for the Fermi field that relate the output fields to the input fields and the field radiated by the cavity. Starting from a constant uniform current of fermions incident on one side of the cavity, we use the boundary conditions to calculate the occupation numbers and current density for the fermions that are reflected and transmitted by the cavity

    1000-MWe LMFBR ACCIDENT ANALYSIS AND SAFETY SYSTEM DESIGN STUDY. TOPICAL REPORT. ACCIDENT ANALYSIS METHODS.

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    Effects of finite arm-length of LISA on analysis of gravitational waves from MBH binaries

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    Response of an interferometer becomes complicated for gravitational wave shorter than the arm-length of the detector, as nature of wave appears strongly. We have studied how parameter estimation for merging massive black hole binaries are affected by this complicated effect in the case of LISA. It is shown that three dimensional positions of some binaries might be determined much better than the past estimations that use the long wave approximation. For equal mass binaries this improvement is most prominent at \sim 10^5\sol.Comment: 10 pages, 3 figures, to appear in Phys.Rev.

    A lower limit on the dark particle mass from dSphs

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    We use dwarf spheroidal galaxies as a tool to attempt to put precise lower limits on the mass of the dark matter particle, assuming it is a sterile neutrino. We begin by making cored dark halo fits to the line of sight velocity dispersions as a function of projected radius (taken from Walker et al. 2007) for six of the Milky Way's dwarf spheroidal galaxies. We test Osipkov-Merritt velocity anisotropy profiles, but find that no benefit is gained over constant velocity anisotropy. In contrast to previous attempts, we do not assume any relation between the stellar velocity dispersions and the dark matter ones, but instead we solve directly for the sterile neutrino velocity dispersion at all radii by using the equation of state for a partially degenerate neutrino gas (which ensures hydrostatic equilibrium of the sterile neutrino halo). This yields a 1:1 relation between the sterile neutrino density and velocity dispersion, and therefore gives us an accurate estimate of the Tremaine-Gunn limit at all radii. By varying the sterile neutrino particle mass, we locate the minimum mass for all six dwarf spheroidals such that the Tremaine-Gunn limit is not exceeded at any radius (in particular at the centre). We find sizeable differences between the ranges of feasible sterile neutrino particle mass for each dwarf, but interestingly there exists a small range 270-280eV which is consistent with all dSphs at the 1-σ\sigma level.Comment: 13 pages, 2 figures, 1 tabl
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