Darren New <dne### [at] sanrrcom> wrote:
> In this case, not *quite*, I think. (Again, you're skirting the edges of my 
> understanding... :-)  There have been other experiments proposed (by 
> Wheeler, for example) that don't involve a second entangled photon at all, 
> but are hard to set up because you need devices that are light-seconds long 
> to make them work. :-)

  Btw, I don't understand why the double slit experiment cannot be used to
send information faster than c.

  Suppose you set up the delayed-choice experiment on orbit around Alpha
Centauri such that you simply shoot a beam of light towards the slits,
behind which there's a detector surface which can be used to see if there's
an interference pattern or not. Then you put the photon splitters at the
slits and send the secondary light particles created this way towards Earth.

  On earth we receive these two secondary beams, and here we make a delayed
choice of whether to merge them or not before measurement. If we merge them,
then the interference pattern appears at Alpha Centauri, and if we don't
merge them (but measure which slit the photons went through) the interference
pattern disappears. This way we can send binary data from Earth to Alpha
centauri: To send a 0 we eg. merge the paths, and to send a 1 we don't.
The guys at Alpha Centauri can then read this info by seeing when the
interference pattern appears and when it doesn't.

  Since the particles are entangled, this happens without any delay.
(The secondary beams my take 4 light years to arrive here, but once they
do, we can send data back immediately, without another 4 ly delay. If the
streams are kept constantly on, after the initial 4 ly delay information
can be send continuously from Earth to Alpha Centauri with zero delay.)

  But apparently this is not possible. Why not?

-- 
                                                          - Warp

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