crowded quantum information

[Eise]

13 hours ago, bangstrom said:

Why do you say they did not demonstrate non-locality.

Because, obviously, most specialists on fundamentals of QM today say that of the two different assumptions behind Bell like inequalities, locality and realism, the most tend to give up on realism. I am not interested in QM of 50 years ago.

Because @joigus, and @MigL quite convincingly explain why.

Because of the no-communication theorem.

Because Bell's theorem only says it is impossible to simulate entanglement with classically devices. With classically working devices, but only then, you would need FTL communication. Using QM, you do not need FTL signals to explain entanglement.

13 hours ago, bangstrom said:

If you have read and understood Zeilinger you should know that he did not support realism but he strongly supports non-locality.

A blatant lie.

Your out of context citation of Zeilinger:  

On 10/6/2022 at 7:01 AM, bangstrom said:

Here is a quote from Anton Zeilinger's book.

" Nearly all physicists agree that the experiments have shown that local realism is an untenable position. The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is nonlocal. This nonlocality is exactly what Albert Einstein called "spooky"; it seems eerie that the act of measuring one particle could instantly influence the other one." From "Dance of the Photons" p. 286

And the next paragraph in Zeilinger's book: 

On 10/6/2022 at 7:43 PM, Eise said:

Ok, back to business: I found a pdf of Zeilinger's book. This is the paragraph immediately after the paragraph bangstrom cited:

Quote

The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.There are indeed hints that this might be the message we have to accept. The most significant result in that connection is the so-called Kochen-Specker paradox.It would go too far to explain it in detail here. A brief mention of the result must suffice. The Kochen-Specker paradox can be stated rather easily. It says that even for individual quantum systems, if they are sufficiently complex, it is not possible to assign to them elements of reality that explain all possible experimental results independent of the full experimental context, i.e. which measurement is performed at the same time on the same system. Now, since Kochen and Specker only considered measurements on single quantum particles, the locality hypothesis does not come into play.

 

Italics by me.

13 hours ago, bangstrom said:

Non-locality violates realism and I think that should be obvious.

We are full circle.

Groundhog Day: you are caught in a loop, bangstrom.

Edited October 26, 2022 by Eise

[bangstrom]

13 hours ago, Ghideon said:

I can't find support for that in official statements*; can you provide a link? Or is it your interpretation of the experimental results?

(The short official reason* is: "for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science")

I am sure the statement from the Royal Swedish Academy is as good as it gets for information but why, except for the experimental observation of non-locality, is anything the prize winners discovered worthy of a Nobel?

Entangled photons demonstrate, as described in John Cramer’s transactional interpretation, that two photons are part of the same direct interaction between emitter and absorber moving both forward and backward in time as described by Wheeler and Feynman. Their transactions are non-local at the quantum particle level but local in our space-time view of the same events.

The violation of Bell’s inequalities demonstrates the reality of the non-local interactions among remote particles having no direct physical contact between them. This is what Einstein called ,”Spooky action”. The violation of Bell’s inequalities also ruled out the possibility hidden variables in the environment that might serve as an alternate explanation for non-locality.

As for pioneering quantum information science, the instant, non-local nature of signals among electrons holds promise for smaller and much faster computers as well as secure means for encryption of EM signals and instant detection if a signal has been hacked.

The one thing that all three of these discoveries have in common is that non-locality sets their experimental results apart from the classical physics of EM signals. Take away the non-locality and they have discovered nothing new.

[bangstrom]

1 hour ago, Eise said:

14 hours ago, bangstrom said:

If you have read and understood Zeilinger you should know that he did not support realism but he strongly supports non-locality.

A blatant lie.

Your out of context citation of Zeilinger:  

Zeilinger is a strong supporter of non-locality and he also rejects local realism. You won't find any quotes in your book to the contrary. On p. 60, Zeilinger says his Ph. D. dissertation was about testing non-locality over large distances.

 

2 hours ago, Eise said:

Here is a quote from Anton Zeilinger's book.

" Nearly all physicists agree that the experiments have shown that local realism is an untenable position. The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is nonlocal. This nonlocality is exactly what Albert Einstein called "spooky"; it seems eerie that the act of measuring one particle could instantly influence the other one." From "Dance of the Photons" p. 286

Take time to read your quote. The first sentence says,"Nearly all physicists agree that the experiments have shown that local realism is an untenable position."

OK, local realism is untenable and you can include Zeilinger as one of the,"Nearly all physicists."

Next part:

"The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is nonlocal. This nonlocality is exactly what Albert Einstein called "spooky"; it seems eerie that the act of measuring one particle could instantly influence the other one."

Here Zeilinger says, the viewpoint of most physicists is that QM is non-local. I am sure Zeilinger includes himself among the "most physicists".  Zeilinger rejects local-realism but accepts non-locality just as I have been claiming. Nicht wahr?

2 hours ago, Eise said:

On 10/6/2022 at 12:43 PM, Eise said:

Ok, back to business: I found a pdf of Zeilinger's book. This is the paragraph immediately after the paragraph bangstrom cited:

Quote

The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.There are indeed hints that this might be the message we have to accept. The most significant result in that connection is the so-called Kochen-Specker paradox.It would go too far to explain it in detail here. A brief mention of the result must suffice. The Kochen-Specker paradox can be stated rather easily. It says that even for individual quantum systems, if they are sufficiently complex, it is not possible to assign to them elements of reality that explain all possible experimental results independent of the full experimental context, i.e. which measurement is performed at the same time on the same system. Now, since Kochen and Specker only considered measurements on single quantum particles, the locality hypothesis does not come into play.

Expand  

In the latter part of the book Zeilinger listed several alternative views to his own that could explain the results of his experiments. Your quote above is one of those alternative views. To quote,"The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform."

This possibility has a recent history. Zeilinger et al. devised an experiment to test the possibility that an experimenter's choice of which measurements to perform could affect the results of an experiment as if by 'wishful thinking'.

As I recall, they decided upon some types of Wheeler's delayed choice experiments and let a computer randomly decide which one to run. Someone complained that a computer could also be responding an experimenter's 'wishful thinking' so they decided to let the colors of the first photons from an extremely distant galaxy tell the computer which tests to run. The galaxy would decide which measurements to be made at one end of the experiment and another galaxy far from the first would decide which measurements would be made at the end.

They found statistically that choices made by distant galaxies gave the same results as when the choices were made by the experimenters so the hypothesis above was busted.

 

 

[Eise]

23 minutes ago, bangstrom said:

Here Zeilinger says, the viewpoint of most physicists is that QM is non-local. I am sure Zeilinger includes himself among the "most physicists". 

Nope. You cannot read. Or intentionally interpret it wrong. He is very clear about it, that his stance is another one than 'most physicists' (in 2010), again the same citation:

Quote

The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.There are indeed hints that this might be the message we have to accept. The most significant result in that connection is the so-called Kochen-Specker paradox.It would go too far to explain it in detail here. A brief mention of the result must suffice. The Kochen-Specker paradox can be stated rather easily. It says that even for individual quantum systems, if they are sufficiently complex, it is not possible to assign to them elements of reality that explain all possible experimental results independent of the full experimental context, i.e. which measurement is performed at the same time on the same system. Now, since Kochen and Specker only considered measurements on single quantum particles, the locality hypothesis does not come into play.

In clear text for you: it is not possible to speak about all properties of a particle, or a pair of entangled particles, before they are measured. That is what is meant by realism. And if we give up on realism, we do not have to give up on locality. And QM does not need none-localism.

26 minutes ago, bangstrom said:

This possibility has a recent history. Zeilinger et al. devised an experiment to test the possibility that an experimenter's choice of which measurements to perform could affect the results of an experiment as if by 'wishful thinking'.

This has nothing to do with locality and/or realism. This is to make the freedom-of-choice loophole (AKA superdetermism) less probable. By using quasars 7.8 Billion lightyears from here, and in opposite direction, it would mean that already 7.8 billion years ago it was determined in which direction the polarizers would be set. From here:

Quote

In this Letter, we present a cosmic Bell experiment with polarization-entangled photons, in which measurement settings were determined based on real-time measurements of the wavelength of photons from high-redshift quasars, whose light was emitted billions of years ago, the experiment simultaneously ensures locality. Assuming fair sampling for all detected photons and that the wavelength of the quasar photons had not been selectively altered or previewed between emission and detection, we observe statistically significant violation of Bell's inequality by 9.3 standard deviations, corresponding to an estimated p value of ≲7.4×10⁻²¹. This experiment pushes back to at least ∼7.8 Gyr ago the most recent time by which any local-realist influences could have exploited the "freedom-of-choice" loophole to engineer the observed Bell violation, excluding any such mechanism from 96% of the space-time volume of the past light cone of our experiment, extending from the big bang to today.

Why going on a side track? We are not discussing superdeterminism here. 

[Ghideon]

Thanks for the answer.

9 hours ago, bangstrom said:

I am sure the statement from the Royal Swedish Academy is as good as it gets for information but why, except for the experimental observation of non-locality, is anything the prize winners discovered worthy of a Nobel?

(Bold by me).
As far as I can tell experimental observation of non-locality is not part of the motivation of the prize*, I do not understand the question, sorry. I do not see the reference I asked for so I assume it's your personal interpretations. 

 

*) Also, it is not part of the scientific background I linked to.

[bangstrom]

1 hour ago, Ghideon said:

As far as I can tell experimental observation of non-locality is not part of the motivation of the prize*, I do not understand the question, sorry. I do not see the reference I asked for so I assume it's your personal interpretations. 

Yes, it is my very own personal opinion that the one thing behind the experimental observations that sets them apart from the ordinary is their application of non-local entanglement in all of their experiments. That is what made them Nobel winners.

[joigus]

10 minutes ago, bangstrom said:

Yes, it is my very own personal opinion [...]

(boldness by you, boldfacedness by me.)

Exactly!

Thank you.

Edited October 26, 2022 by joigus
minor typographical edition

[bangstrom]

8 hours ago, Eise said:

Nope. You cannot read. Or intentionally interpret it wrong. He is very clear about it, that his stance is another one than 'most physicists' (in 2010), again the same citation:

What a mess, we both read the same thing and come up with opposite interpretations. Just for clarification, you are saying here that Zeilinger is not with "most physicists" in saying QM is non-local.

"The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is non-local."

So your claim is that Zeilinger considers QM to be local. My claim is the opposite.

8 hours ago, Eise said:

In clear text for you: it is not possible to speak about all properties of a particle, or a pair of entangled particles, before they are measured. That is what is meant by realism. And if we give up on realism, we do not have to give up on locality. And QM does not need none-localism.

l agree it is not possible to speak about the properties of particles before they are measured. Minor point, the properties are not a part of our 'reality' until they are measured.  And again you are saying QM is local. " does not need none-localism."

9 hours ago, Eise said:

Why going on a side track? We are not discussing superdeterminism here. 

I see the main disagreement here to be about Zeilinger's, and "most physicists" view about QM. You say the views are that QM is local and I say the views are that QM is non-local. Does that simplify it?

Also everyone agrees that realism. local or not, is violated.

[MigL]

Non-realism and non-locality achieve the same results in explaining QM effects like entanglement.
Yet you agree that we have no realism.
So why do we need non-locality, if we already have non realism to explain the behavior ?

If you wish to pursue the non-locality idea, you had better come up with a solid theory as to what this non-local signaling' entails.
How it is transmitted superluminally.
How it violates relativity, especially SR, in deciding which interaction comes first to cause the other.
And many more.
( haven't heard these kinds of arguments since discussing the aether )

I await your explanations and evidence, not just repeats of your previous posts.

 

Edited October 26, 2022 by MigL

[bangstrom]

8 minutes ago, MigL said:

Non-realism and non-locality achieve the same results in explaining QM effects like entanglement.
Yet you agree that we have no realism.
So why do we need non-locality, if we already have non realism to explain the behavior ?

This is an excellent two-part question, one part of which I have explained again and again because it was ignored again and again. I can explain it later...again if anyone cares... except to add that non-locality violates realism. Non-locality is an exception to realism since it is something we never observe at the macro level which is why we have magic shows.

Non-locality itself is a violation of realism so we have no need for non-realism as an explanation for the effects of entanglement.

The second half of the question is for someone else to answer. If we have non-realism as an explanation for QM effects how does that work without non-locality?

 

 

 

[joigus]

8 minutes ago, bangstrom said:

Non-locality itself is a violation of realism so we have no need for non-realism as an explanation for the effects of entanglement.

Non-realism is just the character of QM. So it's not "we don't need it." It's what it's like.

 |electron> = |electron here> + |electron there>

|vacuum> = |particle> + |antiparticle>

Etc.

It's what it is. A non-realistic theory out and out. OK?

It's not "we don't need it" or "maybe tomorrow" or "I don't like it" or "we can do without."

Well, maybe you don't need it, but it's what it is. That's factual. The double-slit experiment has no entanglement, and already tells you that much.

I know you don't like my objections, but I'm here again.

[bangstrom]

1 hour ago, MigL said:

If you wish to pursue the non-locality idea, you had better come up with a solid theory as to what this non-local signaling' entails.
How it is transmitted superluminally.
How it violates relativity, especially SR, in deciding which interaction comes first to cause the other.
And many more.

The 'signal', for the lack of a better word, is measured by clocks synchronized as closely as possible, and the times are observed to be much to fast to measure and far in excess of luminal speed. The explanation is as someone once said, Einstein does not tell God what to do.

I don't find that it violates SR except for the second postulate and possibly not even that.

If it is possible to choose or determine which action came first- then we know which action came first. If we don't know which came first, we simply don't know or usually even care which came first. In SR, if two cars collide is it necessary to know which collided first? Can you explain why this is a even a problem?

[MigL]

Sorry, but that doesn't cut it, and I have to agree with Joigus ( and Eise and Swansont ).
A single quantum particle is neither here nor there, nor anything at all 'realistic' until a measurement/interaction is made.
Where is the 'realism' ?
But more importantly, in regards to your assertion, where is the non-locality for that single quantum particle, which you claim produces the non-realism ????

Edited October 27, 2022 by MigL

[joigus]

28 minutes ago, bangstrom said:

If it is possible to choose or determine which action came first- then we know which action came first. If we don't know which came first, we simply don't know or usually even care which came first.

Here's a riddle for you: If there's no way to know which "action" came first --in a given frame of reference--, how do you know the time interval between the "actions" can be tagged as FTL?

Edited October 27, 2022 by joigus
minor correction

[bangstrom]

31 minutes ago, joigus said:

Non-realism is just the character of QM. So it's not "we don't need it." It's what it's like.

That is right, but for me, non-locality is what makes realism a -non.

 

35 minutes ago, joigus said:

It's what it is. A non-realistic theory out and out. OK?

OK, by me.

 

37 minutes ago, joigus said:

The double-slit experiment has no entanglement, and already tells you that much.

I would disagree but what is that 'something in the environment' that tells the photon how many slits to respond to and where to land. As Wheeler and Feynman and later Cramer concluded, there must be a signal propagating forward and backward in time to initiate the transition of energy.

 

48 minutes ago, joigus said:

I know you don't like my objections, but I'm here again.

A day without your objections is like a day without sunshine. I am worried when we agree.

[joigus]

2 minutes ago, bangstrom said:

A day without your objections is like a day without sunshine. I am worried when we agree.

LOL.

You've made a good point before, and something deep inside of me tells me you're about to understand an important part of this problem. Maybe tomorrow.

Hint:

You said "minor point."

It's not minor at all. It's the key to all the confusion.

[swansont]

1 hour ago, bangstrom said:

The 'signal', for the lack of a better word, is measured by clocks synchronized as closely as possible, and the times are observed to be much to fast to measure and far in excess of luminal speed.

The correlations are confirmed, but you have presented no evidence of a signal. You just assume it’s there. But repetition of the claim is not evidence.

[bangstrom]

4 minutes ago, joigus said:

Here's a riddle for you: If there's no way to know which "action" came first --in a given frame of reference--, how do you know the time interval between the "actions" can tagged as FTL?

That is how it is done. Make the measurements to the far left and far right so close together that there is no way of knowing which came first and see if they are still anti-coordinated. If one particle is measured as spin up, how long does it take for the other particle to 'know' it should be measured as spin down. There is no need to know which came first when measuring just the times.

Tests such as Bell's and other experiments have determined that a single observed quantum property of either member of an entangled pair is random before observed, and when observed, the particles are anti-coordinated. 

If the quantum properties are not fixed from the start but always anti-coordinated, that implies that there must be a signal between the particles that keeps them anti-coordinated either at all times or at the instant of the first observation.

Keeping the measurements short and the distance between measurements great allows a comparison between the signaling speed and light speed. The speeds have been measured to be far in excess of light speed. 

The most dubious part of this experiment is that it assumes that the particles have not kept their same anti-coordinated quantum properties since the start, in which case, no signaling would be required.

This is where Zeilinger's experiments with teleportation become important. Zeilinger demonstrated that a second pair of entangled particles can be generated and entangled with the first pair creating a three way entanglement. By measuring the identity of the free particle from the second entanglement, this instantly fixes the properties of all the entangled particles including the first pair. 

Zeilinger's set-up is not complicated but it is hard to explain. It demonstrates that a single observation of a second entanglement can instantly swap the quantum properties of the first entanglement, in which case, the assumption is valid that the quantum properties need not be fixed from the start and they can change in an instant while remaining anti-correlated. This requires some form of instant signaling among entangled particles.

55 minutes ago, swansont said:

The correlations are confirmed, but you have presented no evidence of a signal. You just assume it’s there. But repetition of the claim is not evidence.

Observing a single property of one particle of an entangled pair instantly fixes the same property of the entangled partner.

This is evidence of some form of signaling.

The possibility that the properties were necessarily the same from the start has been ruled out as I just explained...again.

 

[MigL]

1 hour ago, bangstrom said:

that a single observed quantum property of either member of an entangled pair is random before observed, and when observed, the particles are anti-coordinated. 

If the quantum properties are not fixed from the start but always anti-coordinated, that implies that there must be a signal between the particles that keeps them anti-coordinated either at all times or at the instant of the first observation.

You do understand that entangled systems of quantum particles are solely represented by one common wave function, don't you ?
That is what non-realism means.
They are simply a probability distribution, until the entanglement is broken by observation/interaction.
No signal is required; the quantum particles simply take the states predicted by the collapsed wave function.
That is where the correlation 'resides; no need to transmit anything.

Statements like the one you made above, lead me to believe you don't really have a grasp of QM.
And you certainly don't have a grasp of SR.

Stop re-posting the same quotes over and over, and repeating the same assertions. Present some evidence.

 

Edited October 27, 2022 by MigL

[Eise]

8 hours ago, bangstrom said:

"The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is non-local."

So your claim is that Zeilinger considers QM to be local. My claim is the opposite.

Yep. Read, and understand the paragraph after the one where your citation comes from. Your claim is false.

9 hours ago, bangstrom said:

Yes, it is my very own personal opinion that the one thing behind the experimental observations that sets them apart from the ordinary is their application of non-local entanglement in all of their experiments. That is what made them Nobel winners.

And as @Ghideon clearly has shown to you, in none of the explanations the motivation 'non-locality' is mentioned. 'Local realism', yes, but in its technical meaning: locality and realism, as two distinct assumptions on which CHSH is based. You are subsuming 'locality' under 'realism', which is simply not the way these are used for CHSH.

8 hours ago, bangstrom said:

I see the main disagreement here to be about Zeilinger's, and "most physicists" view about QM. You say the views are that QM is local and I say the views are that QM is non-local.

And still you have not been able to cite even one recent text, where a QM specialist argues that we must give up on locality. Yes, you'll find popular science books in which such is stated, and, even worse, standard QM text books that say such things (read the Coleman article again, and try to understand it!). 

8 hours ago, bangstrom said:

Does that simplify it?

If you need that simplification, then I am glad for you. Close reading of Zeilinger's book, would have solved this from the beginning. 

8 hours ago, bangstrom said:

Also everyone agrees that realism. local or not, is violated.

And what do you mean with 'realism' this time?

5 hours ago, bangstrom said:

non-locality violates realism

And what concept of realism your are meaning here? It cannot be the one of CHSH.

5 hours ago, bangstrom said:

Non-locality itself is a violation of realism

Aha, so not what is the basis of CHSH. 

6 hours ago, bangstrom said:

The second half of the question is for someone else to answer. If we have non-realism as an explanation for QM effects how does that work without non-locality?

I would say "Shut up and calculate". Read Susskind's book, and it is all explained in mathematical detail. 

5 hours ago, bangstrom said:

The 'signal', for the lack of a better word,

There is a better word: correlation!

5 hours ago, bangstrom said:

If it is possible to choose or determine which action came first- then we know which action came first. If we don't know which came first, we simply don't know or usually even care which came first. In SR, if two cars collide is it necessary to know which collided first? Can you explain why this is a even a problem?

OMG! Two cars colliding is a single event. Two measurements are two events. Two measurements that are space-like separated do not have the same timely order in all inertial frames. This comparison is BS.

4 hours ago, bangstrom said:

5 hours ago, joigus said:

It's what it is. A non-realistic theory out and out. OK?

OK, by me.

Psssst.... @joigus uses 'realism' in the same meaning as CHSH does. Not your obfuscating meaning.

[bangstrom]

2 hours ago, Eise said:

10 hours ago, bangstrom said:

"The viewpoint of most physicists is that the violation of Bell's inequality shows us that quantum mechanics is non-local."

So your claim is that Zeilinger considers QM to be local. My claim is the opposite.

Yep. Read, and understand the paragraph after the one where your citation comes from. Your claim is false.

Your interpretation may be correct but the paragraph itself is false. Look at the context from which it came.

Both of our quotes come from a part of the book where Zeilinger is speculating about different possibilities listing the pros and cons of each one without really taking sides so it is hard to tell which of the mentioned views he favors.

Read the introductions.

Zeilinger says,“We now discuss some of the possible conceptual consequences of the breakdown of local realism.”

Here are the intros,

“One possibility is that the reality assumption is not correct.”

“Another possibility would be that the locality hypothesis is not correct.”

My quote in the series began, “ Nearly all physicists agree that the experiments have shown that local realism is an untenable position.”

Your quote began, “The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.”

As I said, Zeilinger later tested the above possibility with his two quasar experiment and found it to be false so I don’t consider that paragraph to be an indicator of Zeilinger’s views no matter how it is interpreted.

2 hours ago, Eise said:

There is a better word: correlation!

Correlation between distant points and under varying conditions requires some form of signaling. Violations of Bell's ineqalities and Zeilinger's teleportation rule out the possibility that particle's quantum properties are not unchanged from the start.

2 hours ago, Eise said:

OMG! Two cars colliding is a single event. Two measurements are two events. Two measurements that are space-like separated do not have the same timely order in all inertial frames. This comparison is BS.

Entangled particles act as if they are side-by-side so any action on one end instantly affects the other as a single event. There is no space-like separation at the particle level, in the way there is at the macro level, so all interactions are essentially instant at the particle level for entangled particles. 

In answer to your question, this is my view of realism:

Realism accepts that the cause of a physical change must be local in that it requires a physical interaction between a cause and effect. It also accepts that objects are real and exist in our physical universe independent of our minds. We live in an objective reality, not one which exists only in our minds or which takes form only upon our looking at it.

3 hours ago, Eise said:

And still you have not been able to cite even one recent text, where a QM specialist argues that we must give up on locality. Yes, you'll find popular science books in which such is stated, and, even worse, standard QM text books that say such things (read the Coleman article again, and try to understand it!). 

On further reading I am open to the possibility that instant action at a distance is 'local' since everything is instant and local for entangled particles and there is no space-like timing between them. I have always considered the emission and absorption of light to be simultaneous events from the perspective of light itself.

As Carver Mead explains, every electron, when the resonant conditions between permit, is capable of a direct interaction with any other electron on the same Minkowski light cone. I can understand that kind of locality but I don't recognize it as the same locality discussed here.                                                                                                                                                                                                                          
 

 

[joigus]

  

15 hours ago, bangstrom said:

What a mess, we both read the same thing and come up with opposite interpretations. Just for clarification, you are saying here that Zeilinger is not with "most physicists" in saying QM is non-local.

Exactly. It's clarified in the next paragraphs. Zeilinger does not endorse "spooky action at a distance":

On 10/26/2022 at 1:27 PM, Eise said:

The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.There are indeed hints that this might be the message we have to accept. The most significant result in that connection is the so-called Kochen-Specker paradox.It would go too far to explain it in detail here. A brief mention of the result must suffice. The Kochen-Specker paradox can be stated rather easily. It says that even for individual quantum systems, if they are sufficiently complex, it is not possible to assign to them elements of reality that explain all possible experimental results independent of the full experimental context, i.e. which measurement is performed at the same time on the same system. Now, since Kochen and Specker only considered measurements on single quantum particles, the locality hypothesis does not come into play.

(quoting Zeilinger.)

The part highlighted in red seems to be implying superdeterminism. I would postpone that, because you have a dangerous tendency to mix up different topics. Suffice it to say that superdeterminism is just one loophole for someone who wants to save some kind of determinism at all costs. People who are familiar with mathematical proofs know very well that finding a counterexample does not necessarily imply the counterexample is unique.

The part highlighted in boldface black is the most important one, which ratifies what @Eise is saying.

15 hours ago, bangstrom said:

l agree it is not possible to speak about the properties of particles before they are measured. Minor point, the properties are not a part of our 'reality' until they are measured.  And again you are saying QM is local. " does not need none-localism."

Good. If you understand what you've said, you could be on the verge of understanding your own confusion. It's not a minor point. It's very important.

It's the essence of the projection postulate, which is deeply non-local, but has no non-local consequences. Only problem: It's just a convention. It's not an evolution law for the state, and certainly not a law of physics. And most importantly, it has no experimental consequences. It was theoretically designed to do exactly that. Go back to my comment on FAPP's Bell's comment.

Most physicists that contributed to the formulation of QM had no problem in seeing the state vector as just an epistemic book-keeping device, reflecting our knowledge. That's why they had no problem in introducing a non-local, non-unitary mathematical convention of which no non-local consequences could be derived.

And last, but not least, as Eise has said above: No. Non-locality does not imply non-realism. They are very different assumptions. Example: Plane waves propagate in a totally local way. Yet, by virtue of selecting the momentum, the position is totally undetermined. That's local non-realism at its simplest, even before we start talking about entanglement.

 

@bangstrom. You also said this in answer to @MigL:

12 hours ago, bangstrom said:

The 'signal', for the lack of a better word, is measured by clocks synchronized as closely as possible, and the times are observed to be much to fast to measure and far in excess of luminal speed. The explanation is as someone once said, Einstein does not tell God what to do.

The quote is from Bohr, in answer to Einstein's famous "God does not play dice" --a colourful way of saying he didn't accept indeterminism at that point. But, really, is that "the explanation" of everything we're talking about here?

 

Edited October 27, 2022 by joigus
correction

[studiot]

1 hour ago, bangstrom said:

My quote in the series began, “ Nearly all physicists agree that the experiments have shown that local realism is an untenable position.”

My local public library is very good at offering new books.

You might like to take a look at this one that has just been published.

https://www.amazon.co.uk/Impossible-Possible-Improbable-Science-Stranger/dp/1785788825

 

The book is divided into the sections, as per the title.
The first section deals with QM and in particular interpretations of QM from Copenhagen right up to the present day.
Localism, realism, Bells, Hidden variables and many famous names are all discussed.
Of particular interest are six different interpretations of QM, superposition, entanglement, etc.
Here is the expanded contents list for this first section.

[swansont]

9 hours ago, bangstrom said:

Observing a single property of one particle of an entangled pair instantly fixes the same property of the entangled partner.

This is evidence of some form of signaling.

No, it’s not. It’s assumed by you, but it’s not a falsifiable assumption. Much like EM waves were not evidence of an aether. Science requires evidence to back up such claims.

There is no interaction in the theory. It’s assumed because of classical physics preconceptions

 

9 hours ago, bangstrom said:

The possibility that the properties were necessarily the same from the start has been ruled out as I just explained...again.

Nobody has disagreed that the states are undetermined. Everyone has confirmed it.

[Eise]

Sigh...

Again you are interpreting Zeilinger wrong. And, framed by your interpretation, even @joigus gets it wrong here:

19 hours ago, bangstrom said:

Your quote began, “The other possibility would be for us to give up the picture of a world that exists in all its properties independent of us. That would mean that we have a very essential influence on reality just by deciding which measurement to perform.”

As I said, Zeilinger later tested the above possibility with his two quasar experiment and found it to be false so I don’t consider that paragraph to be an indicator of Zeilinger’s views no matter how it is interpreted.

18 hours ago, joigus said:

The part highlighted in red seems to be implying superdeterminism.

No, you are reading it 'backwards'. Read precisely what Zeilinger is saying:

Quote

That would mean that we have a very essential influence on reality just by deciding which measurement to perform.

Superdeterminism would be (reshuffling above sentence):

That would mean that reality (even in the far past) has a very essential influence on our deciding which measurement to perform.

Read closely, so that you see the difference. If necessary, repeat in your own words, so that we can check that you really understand that you read the original sentence backwards.

In Zeilinger's own words, in its own paragraph about superdeterminism (calling it 'total determinism'):

Quote

Just for completeness, let us mention that some other positions are also possible, at least in principle.  One is the  assumption of total determinism.  In that case, everything is predetermined, including the decision of the observer about what he wants to measure. Thus, the question of what property the particle would carry if he were to measure something else would not come up at all, and therefore, the logical line of reasoning that led to Bell’s inequality could not be carried out. It is obvious that such a position would completely pull the rug out from underneath science. What would it mean to  do an experiment if that were the case? After all, an experiment is asking nature a question. If nature itself determines  the question, then we might as well not ask that question at all.

Bold by me.

I mentioned that already here:

And this is what the 'quasar-driven' experiment is about. Not about the choice of locality on one side, and realism on the other. Again, bangstrom, in their technical meanings as used in CHSH, not in what you would like to see as realism (non-locality implies non-realism). Zeilinger and co are very clear in their article: it is about closing the free-choice loophole, not about locality or realism.

Just in case you do not notice: I boldface words in my own texts, that use these words as they are meant in their precise meanings as used by all QM authors, especially CHSH.

19 hours ago, bangstrom said:

Correlation between distant points and under varying conditions requires some form of signaling.

Nope. Correlation (consistently, not accidentally) means that the events share a common history. And that is the moment that the entangled particle were produced.

Edited October 28, 2022 by Eise