ScienceDaily (Nov. 12, 2007); The big world
of classical physics mostly seems sensible: waves are waves and
particles are particles, and the moon rises whether anyone watches or
not. The tiny quantum world is different: particles are waves (and vice
versa), and quantum systems remain in a state of multiple possibilities
until they are measured — which amounts to an intrusion by an observer
from the big world — and forced to choose: the exact position or
momentum of an electron, say.
On what scale do the quantum world and the classical world begin to
cross into each other? How big does an "observer" have to be? It's a
long-argued question of fundamental scientific interest and practical
importance as well, with significant implications for attempts to build
solid-state quantum computers.
Researchers at the Department of Energy's Lawrence Berkeley National
Laboratory and their collaborators at the University of Frankfurt,
Germany; Kansas State University; and Auburn University have now
established that quantum particles start behaving in a classical way on
a scale as small as a single hydrogen molecule. They reached this
conclusion after performing what they call the world's simplest — and
certainly its smallest — double slit experiment, using as their two
"slits" the two proton nuclei of a hydrogen molecule, only 1.4 atomic
units apart (a few ten-billionths of a meter). Their results appear in
the November 9, 2007 issue of Science.
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Full story: http://www.sciencedaily.com/releases/2007/11/071109090639.htm