wrote:
Alan Anderson wrote:
wrote:

Also, how does the receive location know that the sender has collapsed
the waveforms? Surely the only way to check is to observe the receive
particle, which would collapse it anyway... or is that the purpose of
the classical communications channel?

That's exactly the purpose of the channel, yes. Information about the
result of the sender's measurement is transmitted to the receiver, who
then arranges an interaction which yields a perfect copy of the sender's
particle.

Arranges an interaction... Isn't that kind of like saying "WOW! I've
discovered a way of turning my friend's house blue from the other side
of the world! AlI have to do is paint my own house house blue, then
email my friend and tell him to paint *his* house blue as well! It
works, look at that! It's blue! Isn't that incredible?"

OK, I've just read
http://pass.maths.org.uk/issue35/fea...ert/index.html and
(assuming it's accurate) that has helped a lot. I think I have a handle
on it now. you can pretty much ignore my previous post.

I can also see why entanglement would be useless for FTL comms - The
actual data communicated is random. You could collapse your waveforms
at points A and B simulateously and read the results, and even know (or
at least assume) that you have the exact same results as the person at
the other end, but all you're going to get is a string of utterly
random numbers - you can't stamp your own message on them, which makes
them pretty much useless for communication. The only reason this is
useful for cryptogrophers is that strings of utterly random numbers can
be used as crypto keys.

WRT crypto I also now appreciate that it's not the message that's
transmitted securely, just the key- and once the key is known to be
secure, you can make the (encrypted) message as public as you like.

Still not sure how it helps quantum computers, but maybe I'll be able
to figure it out for myself now that I've got this far.

Thanks for the answers everyone.

BTW, I have to say that now I have a rudimentary grasp of how it works,
I find the term "teleport" somewhat misleading. All that's happened is
that two particles have assigned the same property.