• #### Nobel price physics 2022.

From Nicolaas Vroom@21:1/5 to All on Mon Oct 10 10:20:38 2022
(1) https://www.nobelprize.org/uploads/2022/10/advanced-physicsprize2022.pdf One of the best documents, mentioned in this document, is the document
(2) https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher in 1967. This brilliant Ph. D. Thesis clearly explains the reaction involved how to produce entangled photons. What this document indirect shows, is that to demonstrate polarization correlation, no thought experiment can be used.
This document states: "A measurement made on one particle can affect the
result of a subsequent measurement on another particle of the same system,
even though the particles may be non-interacting and separated in space."
The question is if that is correct.
The point is, first you have to establish this correlation by performing
1000 experiments on both particles. The result will be that this reaction produces 'always' 2 correlated photons. That does not mean that the
measurement of one affects the other. It is the specific reaction which
causes this correlation.

In document (1) at page 5 is written: "Schroedinger's cat is bizarre".
My first remark is that you can't do this experiment as a thought experiment, but besides that you should try to perform this experiment as simple as possible. This is a description:
Take a wooden box and place a cat, alive, in that box. Close the box.
After 5 minutes you open the box, and observe the state of the cat.
But before you open the box, the experimenter declares that the cat
is both alive and dead. It is not clear what he means. Because the state
of the cat is determined by the physical condition of the cat and how long
the cat is in the box. But not by any human involvement.
You can repeat this experiment 1000 times and observe the state of the cat after 5 minutes, (or any duration) but always is the cat either alive or dead. You can also replace the wooden box by box made from glass, but that makes
no difference for the final outcome. The only difference is when the cat
dies, you can establish the moment when this happens.
You can also make what happens inside the box more complex, but that does
not make any difference; you can't claim that the cat is in two states simultaneous.
It also does not make sense to claim, that Schroedinger's cat would be
alive in one world and dead in another. See page 3. Such a statement can't
be tested by means of any experiment.

Nicolaas Vroom
https://www.nicvroom.be/

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• From Austin Fearnley@21:1/5 to All on Thu Oct 13 12:59:03 2022
On Monday, October 10, 2022 at 6:20:43 PM UTC+1, nicolaa... wrote:
[[Mod. note -- 40 excessively-quoted lines snipped here. -- jt]]

I am an amateur physicist, just at the point of calling it a day. I have
a few days ago put online my final physics paper: on preons and Bell's experiment. So I hope you allow this post as a swan song.

Of course the experimentalists have worked well for their prizes. But the theoreticians still have work to do on this topic.

In the late 1960s I read a book about quantum particles on the magical
world of Mr Tomkins. It was very exciting at the time but I now believe
it is very wrong physics. Particle entanglement of states is merely a sign
that calculations and observations cannot separate two items of raw data, instead only the average is available. The raw data are not available for entanglement, only the statistical, average value data are available.
Forget dead/alive cats as that is a distraction (and a waste of time).
Consider particles entangled with one another and with unknown spin
states. The most believable assumption in my opinion is that nothing
travels faster than light. Associated with this assumption is that retrocausality is the key to this problem.

The implication of retrocausality is that quantum computers have no
foundation in physics as particle always have local hidden variables.
Also that time is two-way at the microscopic level. It is possible that quantum cryptography is supported by retrocausality as there is an
apparent action at a distance despite nothing physically travelling faster
than light locally.

Austin Fearnley

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• From Richard Livingston@21:1/5 to Austin Fearnley on Sun Oct 16 13:09:01 2022
On Thursday, October 13, 2022 at 2:59:07 PM UTC-5, Austin Fearnley wrote:
...
...The most believable assumption in my opinion is that nothing
travels faster than light. Associated with this assumption is that retrocausality is the key to this problem.

The implication of retrocausality is that quantum computers have no foundation in physics as particle always have local hidden variables.
Also that time is two-way at the microscopic level. It is possible that quantum cryptography is supported by retrocausality as there is an
apparent action at a distance despite nothing physically travelling faster than light locally.

Austin Fearnley

Austin,

I think I am in general agreement with you. If you assume no
communication of any kind faster than the speed of light then
"retrocausality" or "superdeterminism" are the natural conclusions. If,
on the other hand you accept faster than light coordination between two
distant detection events you necessarily have an ambiguous causality
sequence, which I don't like.

It appears to me that while there are a significant number of physicists
that accept, or are willing to consider, retrocausality, it is still not
a mainstream concept among physicists. I think the hesitation is
related to the idea of free will and the ability to determine your own
future. Unfortunately this is probably on the boarder of proper science
since it may be untestable and unfalsifiable. I would be very
interested in an idea for testing these ideas experimentally in a more transparent way than the entanglement experiments.

Rich L.

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• From Julio Di Egidio@21:1/5 to nicolaa...@pandora.be on Sun Oct 16 23:11:27 2022
On Monday, 10 October 2022 at 19:20:43 UTC+2, nicolaa...@pandora.be wrote: <snipped>
But before you open the box, the experimenter declares that the cat
is both alive and dead. It is not clear what he means.

That is not what "the experimenter declares", that is
rather the gist of Schroedinger's paradox, that *the
theory* says the cat *is in a superposition of states*,
and what the "paradoxical" consequences of taking
the theory at face value, i.e. for serious, may be.

So, it is not clear what *the theory* means: which,
as I have been explaining in another recent thread,
overall is a question and an issue of ontology...

Julio

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• From Tom Roberts@21:1/5 to Richard Livingston on Mon Oct 17 07:10:35 2022
On 10/16/22 7:09 AM, Richard Livingston wrote:
On Thursday, October 13, 2022 at 2:59:07 PM UTC-5, Austin Fearnley
wrote:
[...]

You are both overthinking this.

Consider a generic experiment on quantum entanglement: Two particles are created at event A in an entangled state, they are separated and
transported to events B and C, where their individual properties are
measured; B and C are spacelike-separated events.

It is observed that:
a) one cannot predict the outcome of either measurement
b) when the results of the two measurements are brought together
and compared, they are found to have the same correlation as
when the particles remain at A and are measured there
simultaneously.

Why would anyone think "retrocausality" is involved here? The path of
causality is quite clear: from A to B and independently from A to C --
there is no causal link between B and C. The fact that the particles at
B and C have a property that is correlated is curious, and violates
classical notions of locality, but is not any sort of refutation of
causality.

The source of this confusion is clear: thinking these are "individual properties", when in fact such ENTANGLED properties are not individual
to the two particles.

Tom Roberts

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• From Richard Livingston@21:1/5 to Tom Roberts on Mon Oct 17 15:20:27 2022
On Monday, October 17, 2022 at 2:10:38 AM UTC-5, Tom Roberts wrote:
On 10/16/22 7:09 AM, Richard Livingston wrote:
On Thursday, October 13, 2022 at 2:59:07 PM UTC-5, Austin Fearnley
wrote:
[...]

You are both overthinking this.
...
The source of this confusion is clear: thinking these are "individual properties", when in fact such ENTANGLED properties are not individual
to the two particles.

Tom Roberts

I disagree, I believe there is something to understand about how these correlations are maintained over such space-time separations.

I believe the point of view of QM is that the two "entangled" particles are
in effect a single thing. Certainly the math treats it that way. Suskind et al. have speculated that the two particles are connected by a wormhole,
and thus they are able to coordinate their behaviors over spatially
separated space-time distances. I'm skeptical of this idea for several reasons: 1) wormholes have never been observed, 2) wormholes are
a speculated GR effect and it isn't clear to me that photons can have
the energy density to warp space-time as required, and 3) it treats
photons as localized particles, which I think is a big misconception.

But I don't know, nobody does yet.

The reason I think there is something to understand here is that the coordination of results is clearly not a local effect. The state of the detectors have been changed randomly and rapidly in some
experiments and still the required correlations observed. Some
how the correlations were preserved even when the detection
conditions changed after emission. This requires either that the
detection events coordinated their response (at faster than the
speed of light) or that the detection events somehow affected the
properties of the emitted photons (i.e. retro-causality).

These ideas are controversial because they are so counter
to our everyday experience. Just saying that the correlations
happen is ignoring the question of how they happen. While it
appears that many physicists choose to not question the mysteries
of QM, I think that is ignoring the possibility of discovering new
physics. It might be like saying Newtonian gravity is the final
law and ignoring the small unexplained precision of Mercury.
We should ALWAYS wonder if there is another layer to be
discovered.

Rich L.

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• From Austin Fearnley@21:1/5 to All on Tue Oct 18 07:30:32 2022
On Monday, October 17, 2022 at 4:20:30 PM UTC+1, richali... wrote:
...
Richard wrote:
" .... I think the hesitation is related to the idea of free will
and the ability to determine your own future. Unfortunately
this is probably on the border of proper science since it
may be untestable and unfalsifiable. I would be very
interested in an idea for testing these ideas experimentally
in a more transparent way than the entanglement experiments. "

I have no ideas about how to introduce free will into a
framework of deterministic calculations that the universe
appears to need. Chaos can be introduced into calculations
using non linear equations but chaos is not free will? One
would need guided-by-free-will use of non-linear equations.
Anyway, I am hanging up my Physics hat and at 73 years
of age feel that I am now too old to work hard enough on physics.

You mention testing. I have obviously thought, but without
success, about how to test whether antiparticles are
travelling backwards in time. For an antiparticle, under my
assumption, the polarisation vector changes from a random
vector to vector d or -d (= detector setting vector) at
measurement, in the antiparticle's own, reversed time
direction. This appears to be a change from vector d or -d
to a random polarisation in the forward time direction.
Adding extra test measurements before or after the main
measurement would always seem to me to interfere too
much and ruin the test.

I am glad you responded to Tom as I could not have
responded so well.

Tom: "The fact that the particles at B and C have a
property that is correlated is curious"

Alice: curiouser and curiouser
Bob: seems darned well spooky to me

My own speculation about Susskind's wormhole
connection is that particles are in dS while antiparticles
are in AdS. This is complicated in my preon model
where each and every particle has both forwards and
backwards-in-time preons within it. Entanglement
(of particle and antiparticle) is probably involved in
construction of spacetime metrics as the metric forms
in the zone where both dS and AdS meet which has
minimal curvature. But that speculation is probably
rubbish. Although most particles are matter, they
overall have an equal number of (my) preons and
antipreons within them. So the loss of antimatter is
caused by spontaneous symmetry breaking in forming
elementary particles from preons.

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• From Stefan Ram@21:1/5 to Austin Fearnley on Tue Oct 18 12:00:33 2022
Austin Fearnley <ben6993@hotmail.com> writes:
I have no ideas about how to introduce free will into a

What do you mean by "free will"?

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• From Nicolaas Vroom@21:1/5 to All on Fri Oct 21 13:12:12 2022
Op maandag 17 oktober 2022 om 09:10:38 UTC+2 schreef Tom Roberts:

Consider a generic experiment on quantum entanglement: Two particles
are created at event A in an entangled state, they are separated and transported to events B and C, where their individual properties are measured; B and C are spacelike-separated events.

What I understand is that you perform an experiment which involves
entangeled particles in two ways:
(See https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher in
1967. This thesis explains the reaction involved how to produce
entangled photons.)
First local. The two particles are created as event A and local
measured as event A1 and A2. Both particles are correlated in the sense
when event A1 indicates up, event A2 indicates down.
Secondly more global. The two particles are created as event A and
measured at a certain distance as event B and C. Both particles are
correlated in the sense when event B indicates up, event C indicates
down.

It is observed that:
b) when the results of the two measurements are brought together
and compared, they are found to have the same correlation as
when the particles remain at A and are measured there
simultaneously.
In short there is no difference if the particles are measured at
a distance of 1m or 100m

Why would anyone think "retrocausality" is involved here? The path of causality is quite clear: from A to B and independently from A to C --
there is no causal link between B and C.
The cause of the the correlation is in the process at A. That is all
what is important.

The fact that the particles at
B and C have a property that is correlated is curious, and violates
classical notions of locality, but is not any sort of refutation of causality.
To mention the concepts locality and causality is not relevent.

The source of this confusion is clear: thinking these are "individual properties", when in fact such ENTANGLED properties are not
individual to the two particles.
The only thing that is important that both particles, in this special
case, have a spin, and that the spins are correlated.
It is also important to understand that as a result of this specific
reaction, it is not required to perform any measurement to assume that
the two particles are correlated. Based on this concept, when any
particle is measured the spin of the other particle is known.
No physical process, or action, or link is involved.

https://www.nicvroom.be/

Nicolaas Vroom

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• From Sylvia Else@21:1/5 to Nicolaas Vroom on Mon Oct 24 07:20:25 2022
On 22-Oct-22 7:12 am, Nicolaas Vroom wrote:
Op maandag 17 oktober 2022 om 09:10:38 UTC+2 schreef Tom Roberts:

Consider a generic experiment on quantum entanglement: Two particles
are created at event A in an entangled state, they are separated and
transported to events B and C, where their individual properties are
measured; B and C are spacelike-separated events.

What I understand is that you perform an experiment which involves
entangeled particles in two ways:
(See https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher in
1967. This thesis explains the reaction involved how to produce
entangled photons.)
First local. The two particles are created as event A and local
measured as event A1 and A2. Both particles are correlated in the sense
when event A1 indicates up, event A2 indicates down.
Secondly more global. The two particles are created as event A and
measured at a certain distance as event B and C. Both particles are correlated in the sense when event B indicates up, event C indicates
down.

It is observed that:
b) when the results of the two measurements are brought together
and compared, they are found to have the same correlation as
when the particles remain at A and are measured there
simultaneously.
In short there is no difference if the particles are measured at
a distance of 1m or 100m

Why would anyone think "retrocausality" is involved here? The path of
causality is quite clear: from A to B and independently from A to C --
there is no causal link between B and C.
The cause of the the correlation is in the process at A. That is all
what is important.

The fact that the particles at
B and C have a property that is correlated is curious, and violates
classical notions of locality, but is not any sort of refutation of
causality.
To mention the concepts locality and causality is not relevent.

The source of this confusion is clear: thinking these are "individual
properties", when in fact such ENTANGLED properties are not
individual to the two particles.
The only thing that is important that both particles, in this special
case, have a spin, and that the spins are correlated.
It is also important to understand that as a result of this specific reaction, it is not required to perform any measurement to assume that
the two particles are correlated. Based on this concept, when any
particle is measured the spin of the other particle is known.
No physical process, or action, or link is involved.

https://www.nicvroom.be/

Nicolaas Vroom

You've assumed that the only situations of interest are the cases where
the measurement of spin are in the same axis or perpendicular axes. The
results of such measurements can be explained by a simple hidden
variable model.

However, once measurements are made on axes at other angles to each
other, the correlations are no longer explainable that way, and locality
is brought into question.

Sylvia.

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• From Nicolaas Vroom@21:1/5 to All on Mon Oct 24 16:05:08 2022
Op maandag 17 oktober 2022 om 17:20:30 UTC+2 schreef richali.@gmail.com:
I disagree, I believe there is something to understand about how these correlations are maintained over such space-time separations.
These correlations are not maintained.
There is also something what is called decoherence

I believe the point of view of QM is that the two "entangled"
particles are in effect a single thing.
That can never be part of the QM, because the concept 'a single thing'
is not clear.
Certainly, the math treats it that way.
Mathematics can consider the two particles as correlated, but that
does not explain any physical interpretation.
Suskind et al. have speculated that the two particles are connected
by a wormhole, and thus they are able to coordinate their behaviours
over spatially separated space-time distances.
Suskind could have introduced a new concept: wormhole. But that
by itself creates only a new problem i.e., what is a wormhole?

I'm sceptical of this idea for several reasons:
okay.

The reason I think there is something to understand here is that the coordination of results is clearly not a local effect.
The cause of the correlations is a local effect.

These ideas are controversial because they are so counter
to our everyday experience. Just saying that the correlations
happen is ignoring the question of how they happen.
https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher in 1967.
What this reaction does: it creates two photons which are correlated.
This raises certain philosophical thoughts.
Suppose that nobody knows that the two particles are correlated.
1)Suppose that the experiment is performed for the first time and that
one photon is observed.
2)Suppose that the experiment for a second time is performed and that
it is observed that not one but two photons are created and observed.
3) suppose that the experiment is performed for a third (and fourth)
time and now it is established that the two photons are correlated.
The question is now: when any photon is measured, does that measurement influence the measurement of the other photon?
Suppose in case 2 the experiment is surrounded by a sphere of CCD's.
In that case in each experiment two of these CCD's will be triggered.
I doubt if any of these two events will influence the other one.
IMO there exist no physical link.

In case 3 the measurement equipment is more complex to establish the correlation between the photons. That means you both have to measure
the fact that there are photons involved and the direction of the spin
in either the x, y or z direction.
Also, in this case there is no reason to assume that the measurement
of the spin-direction of one photon influences the spin-direction
of the other photon.

Suppose, (1) based on multiple experiments, that the direction of the
two photons created is always in one line, but in opposite directions.
Do you think, that (2) when a mirror is placed in one path and the
photon will be reflected, that (3) the direction, of an other photon
(without a mirror) also will be 'reflected'.

https://wwww.nicvroom.be/

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• From Nicolaas Vroom@21:1/5 to All on Sat Oct 29 13:49:48 2022
Nobel price physics 2022.

Op maandag 24 oktober 2022 om 09:20:29 UTC+2 schreef Sylvia Else:
On 22-Oct-22 7:12 am, Nicolaas Vroom wrote:
Op maandag 17 oktober 2022 om 09:10:38 UTC+2 schreef Tom Roberts:

Consider a generic experiment on quantum entanglement: Two
particles are created at event A in an entangled state, they are
separated and transported to events B and C, where their
individual properties are measured.

What I understand is that you perform an experiment which involves entangled particles in two ways:
(See https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher
in 1967. This thesis explains the reaction involved how to produce entangled photons.)

You've assumed that the only situations of interest are the cases where
the measurement of spin are in the same axis or perpendicular axes. The results of such measurements can be explained by a simple hidden
variable model.
My main interest is the document mentioned above and to test the reaction,
if spins in the same axis are correlated.
The correlation is such when the spin of one particle in the x direction
is up the spin in the other particle (in the x direction) is down.
That being the case the explanation of the correlation is part of the
reaction as explained in the thesis.
No hidden variable model if required.
Anyway the correlation is not caused by the measurement.
If you think a hidden variable model is required than please explain
what that means for this specific reaction.

However, once measurements are made on axes at other angles to each
other, the correlations are no longer explainable that way, and
locality is brought into question.

In case one particle is measured in the x-direction and the other particle
in the y-direction (or z-direction) there is no correlation in the results.

Please explain when locality is required.

Nicolaas Vroom
https://www.nicvroom.be/

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• From Phillip Helbig (undress to reply@21:1/5 to sylvia@email.invalid on Mon Oct 31 17:08:31 2022
In article <jrlronFkietU1@mid.individual.net>, Sylvia Else <sylvia@email.invalid> writes:

On 22-Oct-22 7:12 am, Nicolaas Vroom wrote:
Op maandag 17 oktober 2022 om 09:10:38 UTC+2 schreef Tom Roberts:

Consider a generic experiment on quantum entanglement: Two particles
are created at event A in an entangled state, they are separated and
transported to events B and C, where their individual properties are
measured; B and C are spacelike-separated events.

It is also important to understand that as a result of this specific
reaction, it is not required to perform any measurement to assume that
the two particles are correlated. Based on this concept, when any
particle is measured the spin of the other particle is known.
No physical process, or action, or link is involved.

You've assumed that the only situations of interest are the cases where
the measurement of spin are in the same axis or perpendicular axes. The results of such measurements can be explained by a simple hidden
variable model.

However, once measurements are made on axes at other angles to each
other, the correlations are no longer explainable that way, and locality
is brought into question.

Reality is complex, but examples---sometimes even from professional physicists---such as a disk broken in a "random" way (the jagged edges
of each are "correlated"---yes, I really did see that used as an
example) are too simple and misleading and don't grasp the essential
concept.

Here is something in-between. It's wrong, but more involved than the
simple examples. Showing why real correlation is "more" than this might
help to understand it.

Imagine that a vector can have any orientation between 0 and 360
degrees. If it is between 270 and 90, the measurement result is "up".
If between 0 and 180, "right", 90 and 270 "down" and 180 and 360 "left".

Two correlated vectors have opposite directions.

If I measure one to have "up", then I know that the other is "down", but
can't say whether it is "left" or "right". And so on. But if I measure
it to be "right", I know that the other is "left", but can't say whether
it is "up" or "down". I am also free to choose which 90 degrees
correspond to, say, "up".

That model explains many popular presentations of quantum correlation,
but what is the "more" which is actually observed? Is such a model the
simple hidden-variable model mentioned above?

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• From Austin Fearnley@21:1/5 to All on Tue Nov 1 12:04:25 2022
On Tuesday, November 1, 2022 at 8:15:51 AM UTC, Phillip Helbig (undress to reply) wrote: <snip>

Phillip wrote that: "Two correlated vectors have opposite directions".

In classical calculations the exact correlation between any two vectors
is the cosine of the angle between the two vectors. In a Bell
experiment the angle (between the two detector settings) could be say 45 degrees leading to an expected classical correlation of -0.707. In a
large scale [hidden variables] computer simulation in 2017 based on one
million pairs of particles, I found the correlation to be
[-]0.499454164. So so why did I not obtain the larger correlation of
0.707 rather than the attenuated correlation of 0.5?

The attenuated correlation is caused by the quantised input values of +1
or -1 for the particle pairs orientations which are caused by the QM
nature of the particle measurements. Say the first particle pair had the electron oriented along 5 degrees and the positron orient along 185
degrees. Then if Alice measures along her detector setting of zero
degrees, her measurement of the electron is exactly +1. But the exact classical correlation would require an exact measurement or projection
of 5 degrees onto zero degrees. That is near 1.000 but not exactly so
and its exact value is a little less. Using the exact values in 2017
for a million particle pairs gave a correlation of 0.707258632 whereas
using the integer values had given 0.499454164. The exact values are
never known except in a simulation, so in the simulation trying to
reflect a real experiment by using integer measurements the correlation
is attenuated to 0.500.

The real experiments of 2015 however produce correlations significantly
greater than 0.5. That is the 'more' and it does look spooky. I have

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• From Hendrik van Hees@21:1/5 to All on Tue Nov 1 07:24:45 2022
On 31/10/2022 18:08, Phillip Helbig (undress to reply) wrote:

Reality is complex, but examples---sometimes even from professional physicists---such as a disk broken in a "random" way (the jagged edges
of each are "correlated"---yes, I really did see that used as an
example) are too simple and misleading and don't grasp the essential
concept.

Here is something in-between. It's wrong, but more involved than the
simple examples. Showing why real correlation is "more" than this might
help to understand it.

Imagine that a vector can have any orientation between 0 and 360
degrees. If it is between 270 and 90, the measurement result is "up".
If between 0 and 180, "right", 90 and 270 "down" and 180 and 360 "left".

Two correlated vectors have opposite directions.

If I measure one to have "up", then I know that the other is "down", but can't say whether it is "left" or "right". And so on. But if I measure
it to be "right", I know that the other is "left", but can't say whether
it is "up" or "down". I am also free to choose which 90 degrees
correspond to, say, "up".

That model explains many popular presentations of quantum correlation,
but what is the "more" which is actually observed? Is such a model the simple hidden-variable model mentioned above?

In a way it is. You only have to specify a probability distribution of
the hidden variables as Bell did in his famous paper in Physica and
assume "locality". Then you have what he calls a "local realistic hidden-variable theory".

The point of all the debates on the EPR paper, which is just
philosophical and not science, be cause it doesn't provide any
quantitative prediction which can be tested empirically. This has been
achieved by Bell with his inequality based on a set of spin measurements
on a system of two entangled spins 1/2.

The point, which distinguishes QT from any such "local realistic
theories" is that the measured single-particle spin components are not
taking determined values due to the preparation of the two-particle
system in an entangled "Bell state", which is a pure state such that the single-particle spin components are maximally uncertain, i.e., the
reduced statistical oparator of each single-particle spin is simply
describing ideally unpolarized particles, i.e., the single-spin density
matrix is 1/2 \hat{1}. Nevertheless the measurement of any combination
of spin components is strongly correlated. If you measure both spin
components in the same direction it's (for the singlet Bell state) 100%
sure that if you measure "spin up" for one particle, the other must come
upt with "spin down" and vice versa.

Choosing a set of measurements of spin components in different
well-chosen directions you find violations of Bell's inequalities and
thus disprove local realistic theories.

My interpretation is that, what you have to give up is "realism", i.e.,
the assumption that there are hidden variables which make all
observables determined no matter in which state the observed system is
prepared in.

On the other hand locality is obeyed by relativistic quantum field
theory. In fact it's one of the important fundamental building blocks underlying such QFTs, i.e., the assumption that operators that represent
local observables must commute at space-like separation of their
arguments. Particularly all local observables must commute with the
Hamilton density at space-like separation of their arguments and thus
there cannot be any causal connection between space-like separated
events. Particularly if the spin measurements on entangled particles
discussed above are made at space-like separated "measurement events" ("detector clicks") one can be sure that, within local relativistic QFT,
there cannot have been any causal influence of one measurement on the other.

--
Hendrik van Hees
Goethe University (Institute for Theoretical Physics)
D-60438 Frankfurt am Main
http://itp.uni-frankfurt.de/~hees/

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• From Nicolaas Vroom@21:1/5 to All on Tue Nov 8 08:35:15 2022
Op dinsdag 1 november 2022 om 15:24:49 UTC+1 schreef Hendrik van Hees:
On 31/10/2022 18:08, Phillip Helbig (undress to reply) wrote:

Here is something in-between. It's wrong, but more involved than
the simple examples. Showing why real correlation is "more" than
this might help to understand it.

Imagine that a vector can have any orientation between 0 and 360
degrees. If it is between 270 and 90, the measurement result is
"up". If between 0 and 180, "right", 90 and 270 "down" and 180
and 360 "left".

Two correlated vectors have opposite directions.

That model explains many popular presentations of quantum
correlation, but what is the "more" which is actually observed?
Is such a model the simple hidden-variable model mentioned above?

In a way it is. You only have to specify a probability distribution
of the hidden variables as Bell did in his famous paper in Physica
and assume "locality". Then you have what he calls a "local realistic hidden-variable theory".
1 2 3 4 5 6 7 8

IMO the central question to answer is: what is the cause, that in
certain chemical reactions, the two photons, which as part of the
reaction are created, are correlated. That means that the vectors
(or spins) of both 'particles' are in opposite direction.

IMO the most important document to study is this: https://escholarship.org/uc/item/1kb7660q by Carl Alvin Kocher
The article describes (4 items) at page 1:
1. A measurement made on one particle can affect the result of a
subsequent measurement on another particle of the same system, even
though the particles may be non-interacting and separated in space.
2. The experiment described in this thesis is an attempt to observe a
photon polarization correlation in a two-stage atomic cascade.
3. An isolated atom, optically excited, returns to the ground state
by way of an intermediate state, with the spontaneous emission of
two successive photons.
4. Quantum theory predicts that a measurement of the linear
polarization of one photon can determine precisely the linear
polarization of the other photon.

The most important part is item #3, which at the pages 1-4 describes
the details involved. Specific fig 1 which shows Level scheme for

The question to ask, if fig 1 is not enough to describe the physical
process involved to create the two correlated photons?
This correlation is part of the moment when the two photons are created.
The most critical item is #1. Because how can one measurement affect (Simultaneous?) the physical state of the other particle, which are not physical connected? What is a measurement? It is in general a physical disturbance. It also happens when a photon hits my eye. This photon
produces certain changes in the nerves of my brain.
But that is something local not global.

What I want to say is that before any measurement is made the state
of both photons is completely determined as described in fig 1.
The only thing that the first measurement will establish is which
photon it is: 5513A or 4227A
To claim that each photon is in a certain type of superposition
of both 5513A and 4227A does not physical make sense.
This claim only describes lack of human information before the
measurement.

Nicolaas Vroom
http://www.nicvroom.be

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