"Bilge" wrote in message
...
Aidan Smoker:
Hi there all,

I found this discussion on Fermilab's web pages about the quantum
action-at-a-distance phenomena. Even as a scientist I find it an
unsatisfying explanation or resolution of the EPR paradox.

Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in an
envelope and a white card in another. We send each to a physicist who does
not know which one they receive. When say physicist A opens the envelope
and sees say a white card does this send an instantaneous message to the
envelope with the black card - of course not. Same with EPR - nothing about
measuring the polarization of a photon involves a signal propagating faster
than light.

Just for the record I side with the primary state diffusion interpretation
of QM (http://arxiv.org/abs/quant-ph/9508021) because it is experimentally
distinguishable from others - which is something I always find appealing.
It may have been experimentally refuted by now -in which case my support
goes down the drain - but such is life

Thanks
Bill

"Bill Hobba" schrieb
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in an
envelope and a white card in another. We send each to a physicist who
does
not know which one they receive. When say physicist A opens the envelope
and sees say a white card does this send an instantaneous message to the
envelope with the black card - of course not. Same with EPR - nothing
about
measuring the polarization of a photon involves a signal propagating
faster
than light.

You have not understood the problem with EPR-Bell. What you describe
here with cards in envelopes _is_ a local hidden variable explanation of the
correlation. But the correlations in Bell's inequality are of different
type -
an explanation in terms of envelopes and card does not exist, except you
assume that one of the envelopes may be send FTL.

Thus, "same with EPR" is clearly nonsense.

Ilja

"Bill Hobba" a écrit dans le message de
...

"Bilge" wrote in message
...

Aidan Smoker:
I found this discussion on Fermilab's web pages about the quantum
action-at-a-distance phenomena. Even as a scientist I find it an
unsatisfying explanation or resolution of the EPR paradox.

Bilge
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Bill Hobba
Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in an
envelope and a white card in another. We send each to a physicist
who does not know which one they receive. When say physicist A
opens the envelope and sees say a white card does this send an
instantaneous message to the envelope with the black card - of course not.
Same with EPR

Chaverondier
No. This explanation is a local Hidden variable
interpretation which has been discarded by the
violation of Bell's inequalities.

To better understand this point
* Let us consider a polarizer which is oriented at an angle alpha
* Let us label the measured polarisation +1 if the measured
polarization of a photon by this polarizer is alpha.
* Lets us label the measured polarisation -1
if the measured polarization is alpha+pi/2

Then, the probability to measure a polarization +1 on the
"far" side (if a -1 polarization has been observed on the
"local" side) depends on the orientation of the _"local"_
polarizer (with regard to orientation of the far one).

This probability is 100% only if the "far" polarizer
has same orientation than the "local" one.

So, the "far" photon behaviour depends on the orientation
of the "local" polarizer when the "local" photon polarization
is measured (with regard to the orientation of the "far"
polarizer when the far measurment is performed)

However, if quantum indeterminacy is assumed to
be fundamental, then the local observer cannot bias
quantum measurement statistics (Born rule) and
consequently cannot influence the statistics of the far
photons measurements. Hence, quantum indeterminacy
is a sufficient hypothesis to preserve the compatibility
of relativist locality with quantum no-locality.

An even better understanding of quantum non locality can
be achieved if you study the Greenberg, Horn and Zeilinger
thought experiment with three particules A, B and C
of spin 1/2 in maximal intrication state

ie |psi = (|++++|---)/2^(1/2)
where + and - denote spin along the z direction

In this experiment, there no inequalities are involved.
There are only equalities that prove a local spin
measurement to depend on the orientation of the
"far" polarizers.

Bill Hobba
Just for the record I side with the primary state diffusion interpretation
of QM (http://arxiv.org/abs/quant-ph/9508021) because it is experimentally
distinguishable from others - which is something I always find appealing.
It may have been experimentally refuted by now -in which case my support
goes down the drain - but such is life

Chaverondier
This proves your scientific curiosity to exeed
other motivations. I share this way of mind.

Bernard Chaverondier
http://perso.wanadoo.fr/lebigbang/epr.htm
Quantum determinacy or relativist locality.

"Ilja Schmelzer" wrote in message
...

"Bill Hobba" schrieb
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in an
envelope and a white card in another. We send each to a physicist who
does
not know which one they receive. When say physicist A opens the
envelope
and sees say a white card does this send an instantaneous message to the
envelope with the black card - of course not. Same with EPR - nothing
about
measuring the polarization of a photon involves a signal propagating
faster
than light.

You have not understood the problem with EPR-Bell.

Perhaps - but I have read quite a bit on it and worked through the
derivations myself.

What you describe
here with cards in envelopes _is_ a local hidden variable explanation of
the
correlation. But the correlations in Bell's inequality are of different
type -
an explanation in terms of envelopes and card does not exist, except you
assume that one of the envelopes may be send FTL.

Thus, "same with EPR" is clearly nonsense.

Not according to Griffith's who claims in the consistent histories
approach - an approach I have some aquatintance with - it is the exact
analogue of the card situation I describe. This is supposed to be detailed
in the paper 'Correlations in separated quantum systems: a consistent
history analysis of the EPR problem," Am. J. Phys. 55 (1987)' which does not
seem to be available online.

I will try and dig up some online reference that provides the detail of the
claim.

Thanks
Bill


Ilja

"bernard.chaverondier" wrote in message
...
"Bill Hobba" a écrit dans le message de
...

"Bilge" wrote in message
...

Aidan Smoker:
I found this discussion on Fermilab's web pages about the quantum
action-at-a-distance phenomena. Even as a scientist I find it an
unsatisfying explanation or resolution of the EPR paradox.

Bilge
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Bill Hobba
Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in an
envelope and a white card in another. We send each to a physicist
who does not know which one they receive. When say physicist A
opens the envelope and sees say a white card does this send an
instantaneous message to the envelope with the black card - of course
not.
Same with EPR

Chaverondier
No. This explanation is a local Hidden variable
interpretation which has been discarded by the
violation of Bell's inequalities.

See my response to Ilja - the claim is made that in the consistent histories
approach it is the exact analogue. The paper that is supposed to support it
is 'Correlations in separated quantum systems: a consistent history analysis
of the EPR problem," Am. J. Phys. 55 (1987) 11.'. It is not available
online but I will attempt to discover an online analysis.

Thanks
Bill


To better understand this point
* Let us consider a polarizer which is oriented at an angle alpha
* Let us label the measured polarisation +1 if the measured
polarization of a photon by this polarizer is alpha.
* Lets us label the measured polarisation -1
if the measured polarization is alpha+pi/2

Then, the probability to measure a polarization +1 on the
"far" side (if a -1 polarization has been observed on the
"local" side) depends on the orientation of the _"local"_
polarizer (with regard to orientation of the far one).

This probability is 100% only if the "far" polarizer
has same orientation than the "local" one.

So, the "far" photon behaviour depends on the orientation
of the "local" polarizer when the "local" photon polarization
is measured (with regard to the orientation of the "far"
polarizer when the far measurment is performed)

However, if quantum indeterminacy is assumed to
be fundamental, then the local observer cannot bias
quantum measurement statistics (Born rule) and
consequently cannot influence the statistics of the far
photons measurements. Hence, quantum indeterminacy
is a sufficient hypothesis to preserve the compatibility
of relativist locality with quantum no-locality.

An even better understanding of quantum non locality can
be achieved if you study the Greenberg, Horn and Zeilinger
thought experiment with three particules A, B and C
of spin 1/2 in maximal intrication state

ie |psi = (|++++|---)/2^(1/2)
where + and - denote spin along the z direction

In this experiment, there no inequalities are involved.
There are only equalities that prove a local spin
measurement to depend on the orientation of the
"far" polarizers.

Bill Hobba
Just for the record I side with the primary state diffusion
interpretation
of QM (http://arxiv.org/abs/quant-ph/9508021) because it is
experimentally
distinguishable from others - which is something I always find
appealing.
It may have been experimentally refuted by now -in which case my support
goes down the drain - but such is life

Chaverondier
This proves your scientific curiosity to exeed
other motivations. I share this way of mind.

Bernard Chaverondier
http://perso.wanadoo.fr/lebigbang/epr.htm
Quantum determinacy or relativist locality.

"Bill Hobba" wrote in message
...

"Ilja Schmelzer" wrote in message
...

"Bill Hobba" schrieb
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html); say we put a black card in
an
envelope and a white card in another. We send each to a physicist who
does
not know which one they receive. When say physicist A opens the
envelope
and sees say a white card does this send an instantaneous message to
the
envelope with the black card - of course not. Same with EPR - nothing
about
measuring the polarization of a photon involves a signal propagating
faster
than light.

You have not understood the problem with EPR-Bell.

Perhaps - but I have read quite a bit on it and worked through the
derivations myself.

What you describe
here with cards in envelopes _is_ a local hidden variable explanation of
the
correlation. But the correlations in Bell's inequality are of different
type -
an explanation in terms of envelopes and card does not exist, except you
assume that one of the envelopes may be send FTL.

Thus, "same with EPR" is clearly nonsense.

Not according to Griffith's who claims in the consistent histories
approach - an approach I have some aquatintance with - it is the exact
analogue of the card situation I describe. This is supposed to be
detailed
in the paper 'Correlations in separated quantum systems: a consistent
history analysis of the EPR problem," Am. J. Phys. 55 (1987)' which does
not
seem to be available online.

I will try and dig up some online reference that provides the detail of
the
claim.

Trying to locate the detail online for the above claim proved a total
failure. The best I could do is the information given in the link I had
already provided:

'Einstein, Podolsky, and Rosen (EPR) in a celebrated paper [2] showed that
by measuring the property of some system A located far away from another
system B one can, under suitable conditions, infer something about the
system B. By itself the possibility of such an indirect measurement is not
at all surprising, as one can see from the following example. Colored slips
of paper, one red and one green, are placed in two opaque envelopes, which
are then mailed to scientists in Atlanta and Boston. The scientist who opens
the envelope in Atlanta and finds a red slip of paper can immediately infer,
given the experimental protocol, the color of the slip of paper contained in
the envelope in Boston, whether or not it has already been opened. There is
nothing peculiar going on, and in particular there is no mysterious
influence of one "measurement" on the other slip of paper. The quantum
mechanical situation considered by EPR is more complicated than indicated by
this example in that one has the possibility of measuring more than one
property of system A and also considering more than one property of system
B. However, when one does a proper analysis [3], the conclusion is just the
same as in the "classical" case of the colored slips of paper.'

Thus I have to rely on my recollection of how consistent histories get
around it. So at the risk of totally stuffing it up here goes. In
consistent histories everything must be analyzed using the concept of
framework that is decided upon considering the context of the experimental
set up. For EPR type experiments the framework consists of a photon being
up and the other down and conversely - this is the only possible framework.
In the approach no wave function collapse is required - (an overview is
given here http://quantum.phys.cmu.edu/CQT/chap1.pdf):

'Wave function collapse or reduction, discussed in Sec. 18.2, is not needed
for a consistent quantum theory of measurement, as its role is taken over by
a suitable use of conditional probabilities. To put the matter in a
different way, wave function collapse is one method for computing
conditional probabilities that can be obtained equally well using other
methods. Various conceptual difficulties disappear when one realizes that
collapse is something which takes place in the theoretical
physicist's notebook and not in the experimental physicist's laboratory. In
particular, there is no physical process taking place instantaneously over a
long distance, in conflict with relativity theory.'

I recognize the above is very unsatisfactory support of my claim but it is
the best I can find. I am sorely tempted to get Griffith book on the matter
(it is a book I have been manning to get for a while - it is just so
expensive).

Thanks
Bill


Thanks
Bill


Ilja

"Bill Hobba" a écrit dans le message de
...
"Ilja Schmelzer" wrote in message
...

"Bill Hobba" schrieb
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html)

I had a look to that link. The idea of the author is that the
quantum measurement is a stochastic process (which I believe).
However, this doesn't contradict (in my opinion) the possibility
that it be nevertheless a (chaotic) deterministic process and
I don't see how it could discard the (at least) kinematical
non-local nature of Bell's inequalities violation.

The question of the Bell's inequalities is not talked about
into some details, so that it is not possible to see exactly
what is his interpretation of Bell's ineqalities violation.

Whatever this interpretation, the example of the black
and white card sent in two enveloppes is at least misleading
because it cancels the change of correlation induced
by the relative orientation of the two polarizers at the
moment of the measurement (the correlation between
the two measured polarizations is not 100% in any case.
This correlation depends on the relative orientation
of the polarizers at the moment when the polarization
is measured).

Trying to locate the detail online for the above claim proved
a total failure. The best I could do is the information given
in the link I had already provided

You need to provide a detailed analysis of Bell's inequalities
violation (denying them any non-locality and defining precisely
what means this assumed absence of non-locality)

Though I can hardly believe it, I would read such details with
care if you were to provide an other interpretation in the
framework of the decoherent histories interpretation of QM.

Moreover, you have to provide the same type of justification
in the case of the even more puzzling non-locality of the
Greenberg Horn and Zeilinger thought experiment which
needs no inequalities. In this experiment quantum non-locality
shows up in a deterministic manner (no statistical
considerations at all are needed so that I cannot see
where any stochastic justification can enter the play).

In that thought experiment spin 1/2 particles A, B and C are considered
in maximal spin entanglement state |psi = (|++++|---)/2^(1/2)
(where + and - denote spins along z direction).

The spin measurements Ax, Bx and Cx of particles A, B and C
along direction x depends in a deterministic manner on the direction
of the polarizers measuring the spin of the other particules, ie

* if Ax is measured simultaneously with By and Cy
* if Bx is measured simultaneously with Ay and Cy
* if Cx is measured simultaneously with Ay and By
then QM predicts that the product Ax Bx Cx = 1

On the contrary if Ax, Bx, Cx are simultaneously measured
then QM predicts that the product Ax Bx Cx = - 1

So, the measurements of the spins Ax, Bx, Cx
depends critically on the orientation of the measuring
apparatuses of the spin of the other particles when
these spin measurements along x are performed.

So I am waiting for a much more detailed definition of what you
mean by no QM non-locality and a detailed explanation of your
claim in the framework of decoherent history interpretation which
you seem to invoke to support your claim.

Bernard Chaverondier
http://perso.wanadoo.fr/lebigbang
Compatibility of Alain Aspect experiment interpretation as an action at
a distance with a formulation of relativist invariance (of phenomena that
actually satisfy this invariance) in the framework of Aristotle space-time.

"bernard.chaverondier" wrote in message
...
"Bill Hobba" a écrit dans le message de
...
"Ilja Schmelzer" wrote in
message
...

"Bill Hobba" schrieb
Think about what's happening. You measure a photon polarization.
In doing so, what have you discovered? Nothing apart from the
polarization you just measured. Nothing about that measurement
involves a signal propagating faster than light.

Exactly. As one article I read on it said
(http://quantum.phys.cmu.edu/quest.html)

I had a look to that link. The idea of the author is that the
quantum measurement is a stochastic process (which I believe).
However, this doesn't contradict (in my opinion) the possibility
that it be nevertheless a (chaotic) deterministic process and
I don't see how it could discard the (at least) kinematical
non-local nature of Bell's inequalities violation.

The question of the Bell's inequalities is not talked about
into some details, so that it is not possible to see exactly
what is his interpretation of Bell's ineqalities violation.

Whatever this interpretation, the example of the black
and white card sent in two enveloppes is at least misleading
because it cancels the change of correlation induced
by the relative orientation of the two polarizers at the
moment of the measurement (the correlation between
the two measured polarizations is not 100% in any case.
This correlation depends on the relative orientation
of the polarizers at the moment when the polarization
is measured).

Trying to locate the detail online for the above claim proved
a total failure. The best I could do is the information given
in the link I had already provided

You need to provide a detailed analysis of Bell's inequalities
violation (denying them any non-locality and defining precisely
what means this assumed absence of non-locality)

I agree entirely. I have been interested in the consistent histories
interpretation for a while and read some articles on it but could not locate
the one that details its EPR analysis. At this point the out I think it
uses has to do with the acceptance of a single framework to describe any
experimental situation. Under that assumption you have defined your set up
to be the analogue of the card situation. The heart of the consistent
histories approach would seem that such an assumption is allowable.


Though I can hardly believe it, I would read such details with
care if you were to provide an other interpretation in the
framework of the decoherent histories interpretation of QM.

I am afraid that would need for me to fork out the money for Griffiths book.
I am tempted, very tempted, but for personnel reasons that are not really in
scope for this newsgroup I do not want to make any major purchases at
present (its cheapest price is $88 US which would be about $130
Australian ).

I do intend to purchase a copy eventually so I think the best I can promise
is to post the exact analysis at that time.

Thanks
Bill


Moreover, you have to provide the same type of justification
in the case of the even more puzzling non-locality of the
Greenberg Horn and Zeilinger thought experiment which
needs no inequalities. In this experiment quantum non-locality
shows up in a deterministic manner (no statistical
considerations at all are needed so that I cannot see
where any stochastic justification can enter the play).

In that thought experiment spin 1/2 particles A, B and C are considered
in maximal spin entanglement state |psi = (|++++|---)/2^(1/2)
(where + and - denote spins along z direction).

The spin measurements Ax, Bx and Cx of particles A, B and C
along direction x depends in a deterministic manner on the direction
of the polarizers measuring the spin of the other particules, ie

* if Ax is measured simultaneously with By and Cy
* if Bx is measured simultaneously with Ay and Cy
* if Cx is measured simultaneously with Ay and By
then QM predicts that the product Ax Bx Cx = 1

On the contrary if Ax, Bx, Cx are simultaneously measured
then QM predicts that the product Ax Bx Cx = - 1

So, the measurements of the spins Ax, Bx, Cx
depends critically on the orientation of the measuring
apparatuses of the spin of the other particles when
these spin measurements along x are performed.

So I am waiting for a much more detailed definition of what you
mean by no QM non-locality and a detailed explanation of your
claim in the framework of decoherent history interpretation which
you seem to invoke to support your claim.

Bernard Chaverondier
http://perso.wanadoo.fr/lebigbang
Compatibility of Alain Aspect experiment interpretation as an action at
a distance with a formulation of relativist invariance (of phenomena that
actually satisfy this invariance) in the framework of Aristotle
space-time.

"Bill Hobba" schrieb
Thus, "same with EPR" is clearly nonsense.

Not according to Griffith's who claims in the consistent histories
approach - an approach I have some aquatintance with - it is the exact
analogue of the card situation I describe. This is supposed to be
detailed
in the paper 'Correlations in separated quantum systems: a consistent
history analysis of the EPR problem," Am. J. Phys. 55 (1987)' which does
not seem to be available online.
I will try and dig up some online reference that provides the detail of
the claim.

Trying to locate the detail online for the above claim proved a total
failure. The best I could do is the information given in the link I had
already provided:

"... The quantum
mechanical situation considered by EPR is more complicated than indicated
by
this example in that one has the possibility of measuring more than one
property of system A and also considering more than one property of system
B. However, when one does a proper analysis [3], the conclusion is just
the
same as in the "classical" case of the colored slips of paper.'

Behind such claims we usually find the conclusion that the correlation
cannot be used for information transfer. Moreover, there is a
lot of wrong papers written in this domain.

Thus I have to rely on my recollection of how consistent histories
get around it.

Coherent histories (AFAIK, but I have read some papers about it)
is an approach which is quite different from classical realism.
Thus, something accepted as an "explanation"
in consistent histories is not a valid explanation in the sense of
classical realism. It is only an incomplete description.

In the approach no wave function collapse is required - (an overview is
given here http://quantum.phys.cmu.edu/CQT/chap1.pdf):

'Wave function collapse or reduction, discussed in Sec. 18.2, is not
needed for a consistent quantum theory of measurement, as its role
is taken over by
a suitable use of conditional probabilities. To put the matter in a
different way, wave function collapse is one method for computing
conditional probabilities that can be obtained equally well using other
methods.

This already points to the problem. CH is about "suitable use"
of conditional probabilities. Not about explanation in the usual
(classical-realistic) sense.

Ilja

"Ilja Schmelzer" wrote in message
...

"Bill Hobba" schrieb
Thus, "same with EPR" is clearly nonsense.

Not according to Griffith's who claims in the consistent histories
approach - an approach I have some aquatintance with - it is the
exact
analogue of the card situation I describe. This is supposed to be
detailed
in the paper 'Correlations in separated quantum systems: a consistent
history analysis of the EPR problem," Am. J. Phys. 55 (1987)' which
does
not seem to be available online.
I will try and dig up some online reference that provides the detail
of
the claim.

Trying to locate the detail online for the above claim proved a total
failure. The best I could do is the information given in the link I had
already provided:

"... The quantum
mechanical situation considered by EPR is more complicated than
indicated
by
this example in that one has the possibility of measuring more than one
property of system A and also considering more than one property of
system
B. However, when one does a proper analysis [3], the conclusion is just
the
same as in the "classical" case of the colored slips of paper.'

Behind such claims we usually find the conclusion that the correlation
cannot be used for information transfer. Moreover, there is a
lot of wrong papers written in this domain.

I know you have mentioned this previously (with regard to supposed
experimental refutations of Bohm) which is why before discussing the detail
I want to examine the paper or standard text myself. I have decided to
actually purchase the book today (the Book on Consistent Histories by
Griffith) and hopefully will be in a position to post that analysis. BTW I
am not a proponent of consistent histories - I hold to primary state
diffusion (PSD). But what I like about consistent histories is it looks
like Copenhagen done right. If PSD is experimentally disproved then I
probably would revert to consistent histories. Indeed, for my posts to this
newsgroup, sticking to a specific standard treatment like consistent
histories rather than the less conventional PSD may be best.


Thus I have to rely on my recollection of how consistent histories
get around it.

Coherent histories (AFAIK, but I have read some papers about it)
is an approach which is quite different from classical realism.

It is.

Thus, something accepted as an "explanation"
in consistent histories is not a valid explanation in the sense of
classical realism. It is only an incomplete description.

In the approach no wave function collapse is required - (an overview is
given here http://quantum.phys.cmu.edu/CQT/chap1.pdf):

'Wave function collapse or reduction, discussed in Sec. 18.2, is not
needed for a consistent quantum theory of measurement, as its role
is taken over by
a suitable use of conditional probabilities. To put the matter in a
different way, wave function collapse is one method for computing
conditional probabilities that can be obtained equally well using other
methods.

This already points to the problem. CH is about "suitable use"
of conditional probabilities. Not about explanation in the usual
(classical-realistic) sense.

As I said above I will be purchasing the book today and will post its
analysis once I fully understand it. Your input in sorting out what is
happening would of course be appreciated.

Thanks
Bill


Ilja