~e; electromagnetic teleportation
Mon, 11 Feb 2002 14:49:22 -0600
Teleporting larger objects becomes real possibility
19:00 06 February 02
NewScientist.com article. link for full story:
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
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
"One of the advances we have made is that these two particles could
be from completely independent sources," says Bose.
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
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
"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)
(fair-use for EM education, 2oo2, ~e.org)
electromagnetism / infrastructure / civilization