19:00 06 February 02
Anil Ananthaswamy
The dream of teleporting atoms and molecules - and maybe even larger objects
- has become a real possibility for the first time. The advance is thanks to
physicists who have suggested a method that in theory could be used to
"entangle" absolutely any kind of particle.
Quantum entanglement is the bizarre property that allows two particles to
behave as one, no matter how far apart they are. If you measure the state of
one particle, you instantly determine the state of the other. This could one
day allow us to teleport objects by transferring their properties instantly
from one place to another.
Until now, physicists have only been able to entangle photons, electrons and
atoms, using different methods in each case. For instance, atoms are
entangled by forcing them to interact inside an optical trap, while photons
are made to interact with a crystal.
"These schemes are very specific," says Sougato Bose of the University of
Oxford. But Bose and Dipankar Home, of the Bose Institute in Calcutta, have
now demonstrated a single mechanism that could be used to entangle any
particles, even atoms or large molecules.
Beam splitter
To see how it works, consider the angular momentum or "spin" of an electron.
To entangle the spins of two electrons, you first need to make sure they're
identical in all respects but their spin. Then you shoot the electrons
simultaneously into a beam splitter.
This device "splits" each electron into a quantum state called a
superposition, which gives it an equal probability of travelling down either
of two paths. Only when you try to detect the electron do you know which
path it took. If you split two electrons simultaneously, both paths could
have one electron each (which will happen half of the time) or either path
could have both.
Bose and Home show mathematically that whenever one electron is detected in
each path, they will be entangled. While a similar effect has been
demonstrated before for photons, the photons used were already entangled in
another way, even before they reached the beam splitter.
"One of the advances we have made is that these two particles could be from
completely independent sources," says Bose.
Massive particles
The technique should work for any objects - atoms, molecules and who knows
what else - as long as you can split the beam into a quantum superposition.
Anton Zeilinger, a quantum physicist at the University of Vienna in Austria,
has already shown that this quantum state is possible with buckyballs -
football-shaped molecules of C60. Although entangling such large objects is
beyond our technical abilities at the moment, this is the first technique
that might one day make it possible.
Any scheme that expands the range of particles that can be entangled is
important, says Zeilinger. Entangling massive particles would mean they
could then be used for quantum cryptography, computing and even
teleportation.
"It would be fascinating," he says. "The possibility that you can teleport
not just quantum states of photons, but also of more massive particles, that
in itself is an interesting goal."
Journal reference: Physical Review Letters (vol 88, article 05401)
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I find it staggering the way science is leaping forward all the time. So the research that is going on now into teleportation, may one day result in large object / human teleportation. Incredible. The view of Gerry Anderson in Star Trek might one day turn out to be true. Has anyone else noticed that the views of science fiction writers, no matter how unbelievable, might well become reality?
