26,031 research outputs found
Ramsey fringes in a Bose-Einstein condensate between atoms and molecules
In a recent experiment, a Feshbach scattering resonance was exploited to
observe Ramsey fringes in a Rb Bose-Einstein condensate. The oscillation
frequency corresponded to the binding energy of the molecular state. We show
that the observations are remarkably consistent with predictions of a resonance
field theory in which the fringes arise from oscillations between atoms and
molecules.Comment: 5 pages, 5 figure
Some initial results and observations from a series of trials within the Ofcom TV White Spaces pilot
Reversible and irreversible evolution of a condensed bosonic gas
We have formulated a kinetic theory for a condensed atomic gas in a trap,
i.e., a generalized Gross-Pitaevskii equation, as well as a quantum-Boltzmann
equation for the normal and anomalous fluctuations [R. Walser et al., Phys.
Rev. A, 59, 3878 (1999)]. In this article, the theory is applied to the case of
an isotropic configuration and we present numerical and analytical results for
the reversible real-time propagation, as well as irreversible evolution towards
equilibrium.Comment: 15 pages RevTeX, 8 figures, reviewed PRA resubmissio
Quantum Kinetic Theory for a Condensed Bosonic Gas
We present a kinetic theory for Bose-Einstein condensation of a weakly
interacting atomic gas in a trap. Starting from first principles, we establish
a Markovian kinetic description for the evolution towards equilibrium. In
particular, we obtain a set of self-consistent master equations for mean
fields, normal densities, and anomalous fluctuations. These kinetic equations
generalize the Gross-Pitaevskii mean-field equations, and merge them
consistently with a quantum-Boltzmann equation approach.Comment: 15 pages, no figures; reviewed version; to be published in PR
Direct combination: a new user interaction principle for mobile and ubiquitous HCI
Direct Combination (DC) is a recently introduced user interaction principle. The principle (previously applied to desktop computing) can greatly reduce the degree of search, time, and attention required to operate user interfaces. We argue that Direct Combination applies particularly aptly to mobile computing devices, given appropriate interaction techniques, examples of which are presented here. The reduction in search afforded to users can be applied to address several issues in mobile and ubiquitous user interaction including: limited feedback bandwidth; minimal attention situations; and the need for ad-hoc spontaneous interoperation and dynamic reconfiguration of multiple devices. When Direct Combination is extended and adapted to fit the demands of mobile and ubiquitous HCI, we refer to it as Ambient Combination (AC) . Direct Combination allows the user to exploit objects in the environment to narrow down the range of interactions that need be considered (by system and user). When the DC technique of pairwise or n-fold combination is applicable, it can greatly lessen the demands on users for memorisation and interface navigation. Direct Combination also appears to offers a new way of applying context-aware information. In this paper, we present Direct Combination as applied ambiently through a series of interaction scenarios, using an implemented prototype system
Unraveling quantum dissipation in the frequency domain
We present a quantum Monte Carlo method for solving the evolution of an open
quantum system. In our approach, the density operator evolution is unraveled in
the frequency domain. Significant advantages of this approach arise when the
frequency of each dissipative event conveys information about the state of the
system.Comment: 4 pages, 4 Postscript figures, uses RevTe
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