Re: Two EPR questions

From: Thomas Trotter (thomastrotter2005_at_juno.com)
Date: 11/12/04 

Date: Fri, 12 Nov 2004 19:07:47 +0000 (UTC)

Oz <oz@farmeroz.port995.com> wrote in message news:<T$Q7nbQaXIkBFw$T@farmeroz.port995.com>...
> Patrick Van Esch <vanesch@ill.fr> writes
> >Bell is making up a "local realistic" model of the entangled pair. If
> >you say that the photons HAD a specific polarisation direction lambda,
> >then you have to be able to write it down (even if you don't know what
> >it is). That's what he does.
>
> I have terrible trouble getting anyone to actually answer my question on
> this clearly. The question is:
>
> Is lambda wrt some apparatus, or wrt the other photon?

Lambda is the common emission-produced polarization
*direction* of a pair of photons emitted by the same
atom wrt the setting of some apparatus -- specifically,
the transmission axes of the crossed linear polarizers.

>
> This is a critical difference. The former says the angle is fixed from
> the start as seen by the rest of the universe, the latter simply says
> they always have a set relationship.

Exactly.

>
> >Quantum mechanics doesn't take this approach. It writes down that the
> >state is:
> >
> >|psi> = 1/sqrt(2) { |n+>|n-> - |n->|n+ }
> >
> >with n just any direction. So our state is completely "unoriented"
> >which is not possible in a realistic model.
>
> Isn't this simply saying that we cannot know the absolute orientation,
> but do know the relative orientation?

Yes.

>
> I'm not sure I can see why this is 'unrealistic'.
>

It isn't, necessarily. It's just all that can be said about
what's relevant in the experimental context wrt the light -- in
terms that are circumscribed by the limitations of the current
state of the art.

The relationship between the emission-produced polarization
of polarizer-incident photons is what's important -- not the
specific polarization direction. That much seems clear.

And qm embraces this, but it doesn't specify where the
relationship is created. The simplest approach is that
the emission model is, more or less, ok, and the correlation
in polarization is produced via emission. If one takes
this approach, then there is something about Bell's
formulation other than the assumptions of locality and
reality which cause it to fail the tests of comparison
with qm and experimental results. (Maybe it has something
to do with the implicit assumption that direction of
polarization is a factor in determining coincidental
detection.) Also, if one takes this approach, then
there is evidently more to polarization than is currently
known.

> >Now the locality resides in the fact that we have the SAME lambda for
> >A and for B, in that there cannot be an extra variable at B that is a
> >function of a.
> >The photons had to take all their realistic description at their
> >creation and then nothing else for one photon can be dependent on what
> >happens to the other photon.
>
> Ok. But then you immediately remove any entanglement.
> You effectively say these are two isolated and unconnected
> photons, which they cannot be, don't you?

If the entanglement demonstrated in the Bell tests is due
to an emission-produced common property, then what happens at
A really is physically isolated from what happens at B.
It's just that when the common property is observed in some
common context (ie., wrt theta), then the results are predictable.
Entanglement is a correlational, not a causal, relationship.

However, there is apparently no way, given the current state of
physical knowledge, to precisely formulate this in a non-contradictory
fashion.

There are, of course, alternatives which present other
problems.

Relevant Pages

  • Re: I dont understand EPR
    ... which says that paired photons ... thing (lambda) that determines the results in individual ... polarization of the photons incident on the polarizers ... rates of coincidental detection, ie., that lambda is ...
    (sci.physics.research)
  • Re: A Look at Quantum "Spookiness"
    ... The results of quantum theory were described as "spooky" by Drs. ... polarization angle of one of the "paired photons" were changed, ... not in any individual measurement. ...
    (sci.physics.particle)
  • Re: A Look at Quantum "Spookiness"
    ... The results of quantum theory were described as "spooky" by Drs. ... polarization angle of one of the "paired photons" were changed, ... not in any individual measurement. ...
    (sci.physics.particle)
  • Re: I dont understand EPR
    ... I am uncomfortable about two separate particles ... The paired photons produced by Aspect via ... The correlations in the combined context ... is related to its polarization state. ...
    (sci.physics.research)
  • Re: Can isolation break entanglement?
    ... Wrt, for example, experiments that analyze photon pairs produced ... emission process. ... paired photons and theta. ... polarized identically (though the polarization of any pair varies ...
    (sci.physics)
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