Quatum entanglement and FTL

On Oct 2, 2008, at 9:06 PM, Ian Woollard wrote:

> > According to quantum mechanics and the Bell experiment, two
> photons can
> > get theirs quantum states entangled. If they are sent light years
> > appart and the quantum state of the first changes, immediately the
> > second will also change.
>

That's one way to look at it, and but it's not the only way. The
other way to look at it is this: when the two photons get their
quantum states entangled, the universe splits, and we find ourselves
in a universe where (say) photon A is "up" and photon B is "down".
But we don't know this yet, because we're sending them on their long
journey. All we know is that their states must be opposite. So,
light years later, we measure photon A and discover that it's "up," so
we instantly know that the other is "down". But it doesn't mean that
anything in photon B has suddenly changed, and we obviously can't use
this to send any information.

Now, what's really going to make your brain hurt is working out why
it's not possible to get around the Heisenberg Uncertainty Principle
this way...

Best,
- Joe