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QUANTUM TELEPORTATION
has been experimentally demonstrated by physicists at the University of
Innsbruck (Anton Zeilinger, 011-43-676-305-8608, anton.zeilinger@ uibk.ac.at;
Dik Bouwmeester, Dik.Bouwmeester@uibk.ac.at). First proposed in 1993 by
Charles Bennett of IBM (914-945-3118), quantum teleportation allow physicists
to take a photon (or any other quantum-scale particle, such as an atom),
and transfer its properties (such as its polarization) to another photon--even
if the two photons are on opposite sides of the galaxy. Note that this
scheme transports the particle's properties to the remote location and
not the particle itself. And as with Star Trek's Captain Kirk, whose body
is destroyed at the teleporter and reconstructed at his destination, the
state of the original photon must be destroyed to create an exact reconstruction
at the other end. In the Innsbruck experiment, the researchers create
a pair of photons A and B that are quantum mechanically "entangled": the
polarization of each photon is in a fuzzy, undetermined state, yet the
two photons have a precisely defined interrelationship. If one photon
is later measured to have, say, a horizontal polarization, then the other
photon must "collapse" into the complementary state of vertical polarization.
In the experiment, one of the entangled photons A arrives at an optical
device at the exact time as a "message" photon M whose polarization state
is to be teleported. These two photons enter a device where they become
indistinguishable, thus effacing our knowledge of M's polarization (the
equivalent of destroying Kirk).What the researchers have verified is that
by ensuring that M's polarization is complementary to A's, then B's polarization
would now have to assume the same value as M's. In other words, although
M and B have never been in contact, B has been imprinted with M's polarization
value, across the whole galaxy, instantaneously. This does not mean that
faster-than-light information transfer has occurred. The people at the
sending station must still convey the fact that teleportation had been
successful by making a phone call or using some other light-speed or sub-light-speed
means of communication. While physicists don't foresee the possibility
of teleporting large-scale objects like humans, this scheme will have
uses in quantum computing and cryptography. (D. Bouwmeester et al., Nature,
11 Dec 1997; see also www.aip.org/physnews/graphics)
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DO EARTHQUAKES
HAVE ELECTRICAL PRECURSORS?
The elastic waves measured by seismometers are transmitted by the flexing
crust while an earthquake is doing its worst. But some scientists believe
that flexing also goes on in the hours and even weeks before a quake.
Too small to be detected seismically, the flexing might well be sensed
electrically. As underground strata rearrange themselves before a quake,
the thinking goes, pockets of water are squeezed into new configurations,
changing local conduction properties, which can be monitored with buried
electrodes. On this basis Panayiotis Varotsos at the University of Athens
(011-30-1-894-9849, pvaro@leon.nrcps.ariadne-t.gr), has reportedly predicted
certain quakes in Greece weeks ahead of time by triangulating voltage
differentials at the level of 10 millivolts/km over distances of 100 km.
(Some skeptics dispute this assertion.) In new research, Varotsos buttresses
his claims with laboratory studies of another system under pressure which
puts out transient electrical signals before it fractures, namely a crystal
containing a variety of dislocations and defects. Conductivity patterns
in the crystal convince Varotsos that analogous patterns (although on
a much bigger distance scale) observed in the buried electrode arrays
constitute a true earthquake precursor. (Varotsos et al., Journal of Applied
Physics, 1 Jan, 1998; journalists can obtain the paper from physnews@aip.org.)
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