~e; electromagnetic teleportation

[bc <human@electronetwork.org>]

Teleporting larger objects becomes real possibility

19:00 06 February 02
Anil Ananthaswamy

NewScientist.com article.  link for full story:
http://www.newscientist.com/news/news.jsp?id=ns99991888

 
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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