1,105 research outputs found
An Effective Strong Gravity induced by QCD
We show that, when quantized on a curved ``intra-hadronic background'', QCD
induces an effective pseudo gravitational interaction with gravitational and
cosmological constants in the GeV range.Comment: 9 pages, latex, no figures; to appear in Mod.Phys.Lett.
Decoherence in quantum dots due to real and virtual transitions: a non-perturbative calculation
We investigate theoretically acoustic phonon induced decoherence in quantum
dots. We calculate the dephasing of fundamental (interband or intraband)
optical transitions due to real and virtual transitions with higher energy
levels. Up to two acoustic phonon processes (absorption and/or emission) are
taken into account simultaneously in a non-perturbative manner. An analytic
expression of acoustic phonon induced broadening is given as a function of the
electron-phonon matrix elements and is physically interpreted. The theory is
applied to the dephasing of intersublevel transitions in self-assembled quantum
dots.Comment: 8 pages, 4 figure
Parton-Hadron duality in event generators
The validity of local parton-hadron duality within the framework of HERWIG
and JETSET event generators is investigated. We concentrate on annihilations in LEP 2 energy range as these interactions provide
theoretically the cleanest condition for the discussion of this concept.Comment: PRA-HEP-92/14, 10 pages and 7 PS figures obtainable upon request,
LATEX. email transmission errors corrected. Requests for figures can be sent
on the above ID or to CHYLA@CSPGAS1
The effect of extreme confinement on the nonlinear-optical response of quantum wires
This work focuses on understanding the nonlinear-optical response of a 1-D
quantum wire embedded in 2-D space when quantum-size effects in the transverse
direction are minimized using an extremely weighted delta function potential.
Our aim is to establish the fundamental basis for understanding the effect of
geometry on the nonlinear-optical response of quantum loops that are formed
into a network of quantum wires. Using the concept of leaky quantum wires, it
is shown that in the limit of full confinement, the sum rules are obeyed when
the transverse infinite-energy continuum states are included. While the
continuum states associated with the transverse wavefunction do not contribute
to the nonlinear optical response, they are essential to preserving the
validity of the sum rules. This work is a building block for future studies of
nonlinear-optical enhancement of quantum graphs (which include loops and bent
wires) based on their geometry. These properties are important in quantum
mechanical modeling of any response function of quantum-confined systems,
including the nonlinear-optical response of any system in which there is
confinement in at leat one dimension, such as nanowires, which provide
confinement in two dimensions
Thermal breakdown of coherent backscattering: a case study of quantum duality
We investigate coherent backscattering of light by two harmonically trapped
atoms in the light of quantitative quantum duality. Including recoil and
Doppler shift close to an optical resonance, we calculate the interference
visibility as well as the amount of which-path information, both for zero and
finite temperature.Comment: published version with minor changes and an added figur
Achieving ground-state polar molecular condensates by chainwise atom-molecule adiabatic passage
We generalize the idea of chainwise stimulated Raman adiabatic passage
(STIRAP) [Kuznetsova \textit{et al.} Phys. Rev. A \textbf{78}, 021402(R)
(2008)] to a photoassociation-based chainwise atom-molecule system, with the
goal of directly converting two-species atomic Bose-Einstein condensates (BEC)
into a ground polar molecular BEC. We pay particular attention to the
intermediate Raman laser fields, a control knob inaccessible to the usual
three-level model. We find that an appropriate exploration of both the
intermediate laser fields and the stability property of the atom-molecule
STIRAP can greatly reduce the power demand on the photoassociation laser, a key
concern for STIRAPs starting from free atoms due to the small Franck-Condon
factor in the free-bound transition.Comment: 8 pages, 2 figures, to appear in Phy. Rev.
The non dissipative damping of the Rabi oscillations as a "which-path" information
Rabi oscillations may be viewed as an interference phenomenon due to a
coherent superposition of different quantum paths, like in the Young's two-slit
experiment. The inclusion of the atomic external variables causes a non
dissipative damping of the Rabi oscillations. More generally, the atomic
translational dynamics induces damping in the correlation functions which
describe non classical behaviors of the field and internal atomic variables,
leading to the separability of these two subsystems. We discuss on the
possibility of interpreting this intrinsic decoherence as a "which-way"
information effect and we apply to this case a quantitative analysis of the
complementarity relation as introduced by Englert [Phys. Rev. Lett.
\textbf{77}, 2154 (1996)].Comment: 5 pages, 2 figure
Probe spectroscopy in an operating magneto-optical trap: the role of Raman transitions between discrete and continuum atomic states
We report on cw measurements of probe beam absorption and four-wave-mixing
spectra in a Rb magneto-optical trap taken while the trap is in
operation. The trapping beams are used as pump light. We concentrate on the
central feature of the spectra at small pump-probe detuning and attribute its
narrow resonant structures to the superposition of Raman transitions between
light-shifted sublevels of the ground atomic state and to atomic recoil
processes. These two contributions have different dependencies on trap
parameters and we show that the former is inhomogeneously broadened. The strong
dependence of the spectra on the probe-beam polarization indicates the
existence of large optical anisotropy of the cold-atom sample, which is
attributed to the recoil effects. We point out that the recoil-induced
resonances can be isolated from other contributions, making pump-probe
spectroscopy a highly sensitive diagnostic tool for atoms in a working MOT.Comment: 9 pages, 8 figure
Double barrier potentials for matter-wave gap solitons
We investigate collisions of solitons of the gap type, supported by a lattice
potential in repulsive Bose-Einstein condensates, with an effective
double-barrier potential that resembles a Fabry-Perot cavity. We identify
conditions under which the trapping of the entire incident soliton in the
cavity is possible. Collisions of the incident soliton with an earlier trapped
one are considered too. In the latter case, many outcomes of the collisions are
identified, including merging, release of the trapped soliton with or without
being replaced by the incoming one, and trapping of both solitons.Comment: 5 pages, 4 figure
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