Ray Dillinger wrote, quoting me:
> >Another idea would be for the stations to actually absorb the photon
> >in some manner that preserved its polarization, and then to re-emit it.
> >These could be primed to pass only a single photon.
> Now you are talking serious voodoo.  I don't think that this 
> can be done this year.  Maybe not this decade. 

Actually there is a report out just today that could be a big step towards
this capability.  From http://www.aip.org/physnews/update/521-1.html:

   For the first time, physicists in two separate laboratories
   have effectively brought a light pulse to a stop. In the process,
   physicists have accomplished another first: the non-destructive and
   reversible conversion of the information carried by light into a
   coherent atomic form.

This experiment captures light and transforms it into an excited gas
state, in a reversible way, so that the original light pulse can restored
at a later time:

   Usually photons (the quanta of light) are absorbed by atoms, destroying
   the information carried by the light. With the present method, in
   principle, no information in the light pulse is lost.

If this applies to the polarization information as well then it would be
close to what I called for above.

Then you'd still need some way to be able to distinguish how many photons'
worth of energy you'd caught in your gas, or to limit the emission to
only a single photon.  If so then this would be a "single photon" filter.
So perhaps the idea is not as far-fetched as it sounds.


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