745 research outputs found
Basis-dependent dynamics of trapped Bose-Einstein condensates and analogies with semi-classical laser theory
We present a consistent second order perturbation theory for the lowest-lying
condensed modes of very small, weakly-interacting Bose-Einstein condensates in
terms of bare particle eigenstates in a harmonic trap. After presenting our
general approach, we focus on explicit expressions for a simple three-level
system, mainly in order to discuss the analogy of a single condensate occupying
two modes of a trap with the semi-classical theory for two-mode photon lasers.
A subsequent renormalization of the single-particle energies to include the
dressing imposed by mean fields demonstrates clearly the consistency of our
treatment with other kinetic approaches.Comment: 2 Modified Sections: (i) Analogy between 2-mode BEC and
Semi-classical laser theory (ii) Links to other kinetic theories made more
explicit. European Physical Journal D (accepted for publication): Laser
Cooling and Quantum Gas Sectio
Multiple Ionization under Strong XUV to X-ray Radiation
We review the main aspects of multiple photoionization processes in atoms
exposed to intense, short wavelength radiation. The main focus is the
theoretical framework for the description of such processes as well as the
conditions under which direct multiphoton multiple ionization processes can
dominate over the sequential ones. We discuss in detail the mechanisms
available in different wavelength ranges from the infrared to the hard X-rays.
The effect of field fluctuations, present at this stage in all SASE
free-electron-laser (FEL) facilities, as well as the effect of the interaction
volume integration, are also discussed
Quantum Zeno effect by indirect measurement: The effect of the detector
We study the quantum Zeno effect in the case of indirect measurement, where
the detector does not interact directly with the unstable system. Expanding on
the model of Koshino and Shimizu [Phys. Rev. Lett., 92, 030401, (2004)] we
consider a realistic Hamiltonian for the detector with a finite bandwidth. We
also take explicitly into account the position, the dimensions and the
uncertainty in the measurement of the detector. Our results show that the
quantum Zeno effect is not expected to occur, except for the unphysical case
where the detector and the unstable system overlap.Comment: 4 pages, 4 figure
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