20 research outputs found
Realization of GHZ States and the GHZ Test via Cavity QED
In this article we discuss the realization of atomic GHZ states involving
three-level atoms and we show explicitly how to use this state to perform the
GHZ test in which it is possible to decide between local realism theories and
quantum mechanics. The experimental realizations proposed makes use of the
interaction of Rydberg atoms with a cavity prepared in a coherent state.Comment: 16 pages and 3 figures. submitted to J. Mod. Op
Selective Absorption Processes as the Origin of Puzzling Spectral Line Polarization from the Sun
Magnetic fields play a key role in most astrophysical systems, from the Sun
to active galactic nuclei. They can be studied through their effects on atomic
energy levels, which produce polarized spectral lines. In particular,
anisotropic radiation pumping processes (which send electrons to higher atomic
levels) induce population imbalances that are modified by weak magnetic fields.
Here we report peculiarly polarized light in the He I 10830-\AA multiplet
observed in a coronal filament located at the centre of the solar disk. We show
that the polarized light arises from selective absorption from the ground level
of the triplet system of helium, and that it implies the presence of magnetic
fields of the order of a few gauss that are highly inclined with respect to the
solar radius vector. This disproves the common belief that population
imbalances in long-lived atomic levels are insignificant in the presence of
inclined fields with strengths in the gauss range, and demonstrates the
operation of the ground-level Hanle effect in an astrophysical plasma.Comment: 22 pages and 4 figure