Интересная информация

Сообщение №5516 от rtf 29 сентября 2001 г. 22:24
Тема: Интересная информация

The American Institute of Physics Bulletin of Physics News
Number 558 September 26, 2001 by Phillip F. Schewe, Ben Stein,
and James Riordon

gas clouds containing a trillion atoms each, has been achieved by a
research team in Denmark (Eugene Polzik, University of Aarhus,
011-45-89423745, polzik@ifa.au.dk), constituting by far the
largest material objects entangled on demand and paving the way
for quantum teleportation between macroscopic objects. The
accomplishment, published in this week's issue of Nature
(Julsgaard et al., 27 September 2001), was announced in
preliminary form this June at the first International Conference on
Quantum Information, sponsored in part by the Optical Society of
America and the American Physical Society. One of the most
profound features of quantum mechanics, entanglement is a special
interrelationship between objects in which measuring one object
instantly influences the other, even if the two are completely
isolated from one another. No previous entanglement with atoms
has involved more than four particles. Furthermore, atoms have
only been entangled at close proximity, either as ions spaced
microns apart in a tiny trap (Update 475), or atoms flying over a
short range through narrowly spaced cavities (Hagley et al., Phys.
Rev. Lett., 7 July 1997). In the present experiment, researchers
sent a light beam through two cesium gas samples, each held in a
special paraffin-coated cell. The beam changed each sample's
"collective spin," which describes, in a sense, the net direction in
which all of the atoms' tiny magnets add up. First, the researchers
measured the sum of the two collective spins without knowing the
individual collective spin of each sample. A subsequent
measurement, nearly a millisecond later, showed that the sum
remained the same. This demonstrated that the two gas samples
maintained their special interrelationship and were entangled.
Although the two samples were just millimeters apart, they could
in principle be separated, and thereby entangled, at much longer
distances. Entanglement of such large objects enables "bulk"
properties, like collective spin, to be "teleported," or transferred,
from one gas cloud to another.

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