Re: Physics News Update 660 (fwd from

From: Hal Finney <>
Date: Tue, 4 Nov 2003 08:51:20 -0800

Eugen Leitl forwards:

> (Paul Alsing, University of New Mexico, 505-277-9094,
> In quantum teleportation (see
> researchers create a pair of particles (such as photons) and cause
> them to interact so their properties become interrelated (a process
> called "entanglement"). Subsequently, after the particles go their
> separate ways, one can measure the first particle's properties (such
> as the direction its electric field is wiggling), destroy the
> particle (a requirement), and then instantly transmit (or
> "teleport") its exact properties to the second particle, even if it
> ends up being light years away.

I guess this result is not too surprising, although I don't claim to
understand the details. QT requires great delicacy in handling the
particle states involved and no doubt a great many outside influences
could disrupt the effect.

BTW the description above for QT is not quite right,
at least it is not the way it is normally presented. See for another
presentation. Usually the two entangled particles serve as a channel
or conduit by which the information from yet a third particle is

> Quantum teleportation is different
> from Star Trek teleportation in that real-life physicists are only
> teleporting a particle's properties, rather than the particle
> itself.

By most interpretations of QM, a particle is defined by its properties,
so teleporting those is the same as teleporting the particle.

One point to keep in mind with QT is that there must be a transfer of
"classical" information from the source to the destination. Deutsch has
argued that from a certain perspective, the quantum information can
be viewed as "piggybacking" on this classical information transfer.
This is hard to understand, but it is perhaps less problematic than
alternatives such as information travelling backwards in time.

Hal Finney
Received on Tue Nov 04 2003 - 12:07:02 PST

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