Re: TECH: Quantum Head Job

From: Adrian Tymes (
Date: Wed Oct 10 2001 - 21:00:10 MDT

"Smigrodzki, Rafal" wrote:
> Adrian Tymes wrote:
> A lot of the apps I've seen suggested by communicating through
> entangled pairs can also be done with lower-tech data communication.
> All this does is make the communication instantaneous, but speed of
> light is often fast enough for short-range versions of the same.
> ### Correct me if I am wrong but I thought that quantum entanglement
> can be used for quantum encryption but the actual sending of
> information has to occur via a classical channel and is limited by
> light speed.

Well, here's how I understand it:

The entangled two particles have a property, spin, that is guaranteed
to be opposite. Whatever the one particle's spin is or becomes, the
other is immediately the opposite. If all you do is measure it, then
that's like picking one ball out of a bag that has a white and a black
ball, then being able to instantly determine from your ball what the
other ball's color is, no matter how far away it is.

*But*, if you *alter* the shared property, then the alteration also
happens immediately...or so I've been told. Measuring that property
from moment to moment to see if it changed would be the communication
channel in that case. I don't know exactly what the alteration process
is, but it's similar to what goes on in quantum computers, to force
several initially equally likely outcomes to change their
probabilities, until the single correct solution has probability 1 and
everything else has probability 0. (That is, there is some method of
affecting the spin of a particle...)

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