Jump to content

crowded quantum information


hoola
 Share

Recommended Posts

16 hours ago, joigus said:

But now I think it's obvious why I'm annoyed. If, for some reason, you don't like the maths, or you find its sheer mention annoying, or you don't think it's part of the argument, just tell me and I will try to re-phrase in some other way, because it is. It is an essential part of the argument. Don't just dismiss it or ignore it.

Non-local interactions have been demonstrated as “real” in both theory and practice so I don’t understand the futility of explaining why there is no such thing.

That reminds me of the mathematician long ago who published his calculations about the very minimum size for a functional radio coil. Unknown to him, a radio experimenter had already patented a working radio coil that was far smaller than his theoretical limit.

This is still happens now. Mathematicians calculate the minimum size of an IC junction but the manufacturers don’t care. They they keep designing working chips that are smaller and better than theory allows. As Feynman said about IC’s, “There is room at the bottom”. 

You and others may have equations where what appears to be non-locality is really local but there are others such as John Cramer who showed how the mathematical formalism of QM can be interpreted in terms of direct interaction (non-local) between emitter and absorber. Hugo Tetrode did the same in 1922.

If you can site some physical experiments that demonstrate what you are saying, you have my attention. I don’t know of any such experiments but there are many that demonstrate non-locality.

10 minutes ago, swansont said:

TIQM uses, as far as I understand, an interaction between the particles

Yes, it does but the interaction is not physical. In TIQM a "photon" is not a space traveling, energy carrying particle. A 'photon' is Cramer's name for the single quantum of energy involved in the transaction.

Link to comment
Share on other sites

2 minutes ago, bangstrom said:

Non-local interactions have been demonstrated as “real” in both theory and practice so I don’t understand the futility of explaining why there is no such thing.

This is simply false. There is no such thing as non-local interactions. Please give references or stop repeating things you think you've heard or read. Your argument is logically indistinguishable from accounts that bigfoot is real...

I'm sorry... "real."

4 minutes ago, bangstrom said:

That reminds me of the mathematician long ago who published his calculations about the very minimum size for a functional radio coil. Unknown to him, a radio experimenter had already patented a working radio coil that was far smaller than his theoretical limit.

This reminds me of someone who once said something that was totally wrong. :rolleyes:

Come on. You can do better than this. Oh, wait... No, you can't.

Link to comment
Share on other sites

23 hours ago, joigus said:

Please, use the quote function --as I did-- to direct me to your definition of non-locality, as I seem to have missed it.

 Underlined in the quote below was my definition of non-locality:

On 9/15/2022 at 4:35 AM, joigus said:

So now I think it's your turn. What is non-locality?

(my reply below)

You never responded when I asked you the question… so now its my turn?

Einstein’s view of non-locality works for me. “Spooky action at a distance.”

Non-locality is a non-observable time interval between an action and a reaction because the timing is either instant or far too fast to measure. It is instant action at a distance.

This is a quote from wiki:

"In theoretical physics, quantum nonlocality refers to the phenomenon by which the measurement statistics of a multipartite quantum system do not admit an interpretation in terms of a local realistic theory. Quantum nonlocality has been experimentally verified under different physical assumptions.[1][2][3][4][5] Any physical theory that aims at superseding or replacing quantum theory should account for such experiments and therefore cannot fulfill local realism; quantum nonlocality is a property of the universe that is independent of our description of nature.

Quantum nonlocality does not allow for faster-than-light communication,[6] and hence is compatible with special relativity and its universal speed limit of objects. Thus, quantum theory is local in the strict sense defined by special relativity and, as such, the term "quantum nonlocality" is sometimes considered a misnomer. Still, it prompts many of the foundational discussions concerning quantum theory."

https://en.wikipedia.org/wiki/Quantum_nonlocality

I am still waiting for your definition of non-locality.
 

Edited by bangstrom
Added a quote from wiki.
Link to comment
Share on other sites

4 hours ago, bangstrom said:

Einstein’s view of non-locality works for me. “Spooky action at a distance.”

This is not a definition. It works for you just because --no offence-- you seem to have very low standards on what constitutes a definition. "Spooky" is not a physical term. If you paid even the slightest attention to the mathematical formalism of quantum mechanics, you would understand this perfectly, as both any "blips" of information, or any "blips" of energy would have to travel in the form of "blips" in the square of the absolute value of the wave function --or the square of the gradient too, in the case of energy. That's what the quantum dynamics doesn't allow to do superluminally.

4 hours ago, bangstrom said:

Quantum nonlocality does not allow for faster-than-light communication,[6] and hence is compatible with special relativity and its universal speed limit of objects. Thus, quantum theory is local in the strict sense defined by special relativity and, as such, the term "quantum nonlocality" is sometimes considered a misnomer. Still, it prompts many of the foundational discussions concerning quantum theory."

(quoting your quote)

Yes. Therefore => there can be no non-local interactions. Maybe we would have to go a step down and discuss what an interaction is. You say things like,

10 hours ago, bangstrom said:

Yes, it does but the interaction is not physical.

What? The interaction is not physical? What is it then? Metaphysical?

Because I'm keenly aware of the dangers of letting hidden assumptions slip into your arguments, I've found that it may be useful to strip the ideas to their bare minimum, and say only what they say, and nothing more. What comes next is a sketch of the history of these ideas. This is in order to satisfy @Eise's demands that we be clear.

EPR: If you can predict with absolute certainty the result of an experiment without in any way disturbing the system, there must be some element of reality underlying it. Quantum mechanics says that certain pairings of observables are incompatible, say A and B. If I can exploit a conservation law that's valid for at least one of them, say A, in a bipartite system (A1+A= constant) and measure A in part 1, and B in part 2, I can infer what the value of A2 is without actually measuring it. I can, at the same time (within a space-like interval) measure B for 2, that is B2, with as much precision as desired, and I would have proven that quantum description of reality is incomplete, because I would have the values of A2 and B2, which quantum mechanics declares as incompatible. In a nutshell: Either quantum mechanics is incomplete, or your wave function would have to be updated superluminally, to make this incompatible character of A and B persist. 

I hope that is clear. If it is, we can all jump to the same page and proceed to Bohm, CHSH-Bell, Aspect.

That means: why Bohm shifted the discussion to spin, what do the CHSHB correlations say and don't say, and what Aspect actually found.

Then, perhaps, a discussion of science as perceived by the masses as well as relatively learned non-experts, and why this non-locality nonsense proves to be so persistent, the very same way that thousands and thousands of claims of possibilities for perpetual motion kept coming long after the question of its impossibility was perfectly understood by the theorists.

 

Edited by joigus
minor addition
Link to comment
Share on other sites

6 hours ago, bangstrom said:

Non-locality is a non-observable time interval between an action and a reaction

Action and reaction implies causality, which implies information transfer.
Which is impossible.
Correlations, OTOH, have no such limitations.

Your definition is a non-starter.
Maybe we need to  define 'action/reaction' and 'correlation' as well, as we seem to be confusing their meanings/implications.

Edited by MigL
Link to comment
Share on other sites

5 minutes ago, MigL said:

Action and reaction implies causality, which implies information transfer.
Which is impossible.

Your definition is a non-starter.

Not to mention that, according to @bangstrom, non-locality is.

(drums for dramatic effect...)

...

...

A non-observable time!!

Ta da!!

I would add, if it's non-observable, why bother with it at all?

Again, let's strip it to its bare minimum:

Bangstrom says:

1) Non-locality is a time

2) It cannot be observed

Could it be that we agree in the end? Even, in a Donald Rumsfeld way, we may propose that we:

a) Agree to agree

b) Agree to disagree

c) Disagree to agree

d) Disagree to disagree

Let them do their cleaning up their own house a little.

 

Link to comment
Share on other sites

Perhaps I can quote Markus, from another thread, which, although dealing with quantum gravity, seems very appropriate for quantum systems in general

"I completely agree, especially since we already know that our usual paradigms don’t work for this. In particular, I suspect that any notions of smooth and regular space, time, spacetime with well-defined causal structures, and fields on spacetime will become meaningless in the realm of quantum gravity. Physics there will deal with dynamical quantities that are very different from those of ordinary classical physics, or even those of quantum physics, which will likely change the way we think about reality in very fundamental ways."

Note, in particular, the bolded part.
Quantum systems play 'fast and loose' with causal structures, simply because they are probabilistic.

Link to comment
Share on other sites

27 minutes ago, MigL said:

Quantum systems play 'fast and loose' with causal structures, simply because they are probabilistic.

Agreed. I would only add that, on top of all that, quantum systems force us to think in terms of amplitudes, which are meta-probabilistic, if I may be allowed to use the term. And we don't exactly know what amplitudes objectively represent. Behind all this confusion, lies the question of the interpretation of quantum mechanics, ie, the several implementations of the principles of quantum mechanics that make no difference as to the experimental results, while at the same time seem to have completely irreconcilable ontologies underlying them.

I think the confusion of many people with such issues as "non-locality," "collapse of the wave function," "Schrödinger cats" (macroscopic superpositions, etc.) comes from the fact that we haven't, as yet, totally understood what amplitudes are representing, how to implement measurements in a non-ambiguous way, etc.

If I may be allowed to present a contention here --after all we are on the Speculations section-- is that we haven't totally understood the objective role that the gauge principle plays in all of this, but that's a topic for another --hopefully engaging-- thread.

Please, mind my use of "objectively represent" instead of "is."

Edited by joigus
minor addition
Link to comment
Share on other sites

9 hours ago, joigus said:

What? The interaction is not physical? What is it then? Metaphysical?

All I see here is a lot of unsupported personal opinions. Ernst Mach was opposed to the use of “metaphysicals” to explain physical phenomenon and high on his list of metaphysicals was the assumption that light energy exists in the space between a signal and receiver.

If non-locality is impossible, then what are quantum experimenters examining that looks like ‘non-local’ interaction?

And, is the Newtonian view of time, where instant action-at-a-distance does not exist, still valid in QM?

You said,”I hope that is clear. If it is, we can all jump to the same page and proceed to Bohm, CHSH-Bell, Aspect.”

Can you give us a quote of what either Bell or Aspect had to say about the implication behind the non-existence of ‘hidden variables’?

You claim I said, “Non-locality is a time.”

OK, I did say that but the timing of events between the emission and absorption of a light signal is zero but we can never observe the time between two simultaneous events as zero because our observation is ‘space like’ where every measurement of space includes a measurement of time (spacetime).

For light, the proper relativistic timing is zero time. Emission and absorption are simultaneous events from the perspective of a light signal but we can never observe two events separated by distance as instantaneous. Our observation of two simultaneous events separated by distance is always ‘space-like’ where the observed time is equal to d/c for all observers. That does not imply that the timing of events when measured at the individual particle level is necessarily ‘space like’.

I have a definition for 'non-locality'. Do you?

Link to comment
Share on other sites

1 hour ago, bangstrom said:

I did say that but the timing of events between the emission and absorption of a light signal is zero but we can never observe the time between two simultaneous events as zero

Mostly because a valid frame of reference for a photon ( emission/ absorption ) does not exist.
Much like non-locality involving superluminal communication/interaction.

Link to comment
Share on other sites

1 hour ago, bangstrom said:

All I see here is a lot of unsupported personal opinions.

I agree, and they're all yours.

1 hour ago, bangstrom said:

Ernst Mach was opposed to the use of “metaphysicals” to explain physical phenomenon and high on his list of metaphysicals was the assumption that light energy exists in the space between a signal and receiver.

What Mach thought about anything that can be applied to the interpretation of quantum mechanics interests me about as much as Heraclitus's views on the imac. You, as always, choose not to address any criticism. If this interaction that you claim is not physical, what is it? Metaphysical? Does it belong to an alternate reality? Is it the result of a midsummer's night dream?

Will you finally answer at least to that?

1 hour ago, bangstrom said:

If non-locality is impossible, then what are quantum experimenters examining that looks like ‘non-local’ interaction?

Quantum correlations that reflect non-separability. @MigL has told you, I have told you, @swansont has told you, Alain Aspect has told you, Murray Gell-Mann has told you, Sidney Coleman has told you. Will you finally take it home?

The only thing that looks non-local is Copenhagen's old projection postulate, that require you to kill off all the components of the wave function that are ruled out by a measurement. But it is incompatible with the Schrödinger equation. So people don't believe it anymore.

1 hour ago, bangstrom said:

And, is the Newtonian view of time, where instant action-at-a-distance does not exist, still valid in QM?

And again you're wrong. Newton did postulate an action at a distance. Newtonian physics has action at a distance written all over it. He did find it weird, and tried to defend himself from possible philosophical criticism with his famous hypotheses non fingo.

1 hour ago, bangstrom said:

Can you give us a quote of what either Bell or Aspect had to say about the implication behind the non-existence of ‘hidden variables’?

I already did. Now you go back and read. I don't want this to be me doing all the work, while you dash off a note declaring your incredulity and proving to everybody that you haven't read anything. However, you should notice that physics is not resolved in quotes by famous people. It's more complicated.

1 hour ago, bangstrom said:

For light, the proper relativistic timing is zero time. Emission and absorption are simultaneous events from the perspective of a light signal but we can never observe two events separated by distance as instantaneous. Our observation of two simultaneous events separated by distance is always ‘space-like’ where the observed time is equal to d/c for all observers. That does not imply that the timing of events when measured at the individual particle level is necessarily ‘space like’.

What are you saying? A photon is not a valid observer. The proper time of a photon is not a valid observable. The observed time is different for different inertial observers..., etc. If you ignore basic physical laws, I have no business with you anymore. I'm wasting my time, and I am no photon.

1 hour ago, bangstrom said:

I have a definition for 'non-locality'. Do you?

Again? Really? How stupid do you think I am? I've given you the definition, and you've done nothing but dismiss it from an argument of incredulity. And you've done nothing but mumble something about a non-observable time.

 I'm not going to address any of your questions again. You stick with your unsupported unscientific incredulity. I'm trying just to honour @Eise's more than reasonable request to make the main points clear.

Is this some kind of social experiment?

Link to comment
Share on other sites

2 hours ago, joigus said:

If this interaction that you claim is not physical, what is it? Metaphysical? Does it belong to an alternate reality? Is it the result of a midsummer's night dream?

It is non-local interaction at a distance without a direct physical contact.

 

2 hours ago, joigus said:

Quantum correlations that reflect non-separability. @MigL has told you, I have told you, @swansont has told you, Alain Aspect has told you, Murray Gell-Mann has told you, Sidney Coleman has told you. Will you finally take it home?

I have never disputed that quantum correlations reflect non-separability. When the common wave function between remote particles is lost, the loss is instant (non-local) on both ends no matter how far apart the particles may be. When entanglement is lost, the identities of the particles become determinate and they are also anti-coordinated. The simultaneous loss of entanglement on both ends is the non-local part of this scenario.

 

2 hours ago, joigus said:

The only thing that looks non-local is Copenhagen's old projection postulate, that require you to kill off all the components of the wave function that are ruled out by a measurement. But it is incompatible with the Schrödinger equation. So people don't believe it anymore.

Now I understand! Generally speaking, non-locality is like a ‘big foot’ that some claim to see but no one believes anymore.

Since when was this true, and why wasn’t I informed?


 

Link to comment
Share on other sites

4 hours ago, joigus said:
6 hours ago, bangstrom said:

Can you give us a quote of what either Bell or Aspect had to say about the implication behind the non-existence of ‘hidden variables’?

I already did. Now you go back and read. I don't want this to be me doing all the work, while you dash off a note declaring your incredulity and proving to everybody that you haven't read anything.

As I recall I did read your quote by John Bell somewhere else but I recall that he got to the point about non-locality in the next paragraph which went something like this: “If the hidden variable extension is local it will not agree with quantum mechanics, and if it agrees with quantum mechanics it will not be local." John Bell

 

5 hours ago, joigus said:

So people don't believe it anymore.

 I find this to be a misrepresentation of the current condition. Check it out.

"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."-  Anton Zeilinger

“Dance of the Photons” by Anton Zeilinger 2010 p. 286

Link to comment
Share on other sites

Hui, Joigus, now you have fallen into a trap. If it is your own, or the 'Journal de physique' (or some other source) I don't know, but Bell is citing Einstein in your highlighted passages:

image.png.aa46138ce8e9be3861735e19d2287334.png

 

Here Bell is speaking for himself:

image.png.c76276dd4dfa9737a746ec2bd0429306.png

And after his argument:

image.png.409adc249b607762f2ec9cfc631bea53.png

It is obvious that Bell doesn't like this conclusion, and discusses 4 ways out:

  • QM is wrong, at least in the case of such situations
  • Superdeterminism (he doesn't name it like that, but is clear that he is pointing at that)
  • Lorentz transformations are not valid
  • There is no reality below some "classical" "macroscopic" level (quotation marks from the original)

Concerning the first point: Aspect was still working on his experiments, and Bell refers to that. His comment:

image.png.a390772023ecfafd62887eb73fb0754f.png

We know how the experiment went out...

From other articles, I have reason to believe that he was going for the first point, i.e. that QM is incomplete. He was puzzled by the results of the Clauser and Aspect experiments.

Bell says exactly the opposite of what you are saying.

I think it is important that you all, discutants (my word creation?), are very clear with the words you are using. I give a few proposals:

  1. action (or interaction): a physical process, where energy and momentum are exchanged, and so special relativity applies
  2. correlation: as in the example of the shoes in the boxes

To 1: even Bell is confusing here, because he says "They cannot be explained, that is to say, without action at a distance." (Bold by me)

To 2: I would say that the Bell inequalities, together with the confirmation that they do not hold in QM in experiments, show that QM has stronger correlations than local realistic theories allow.

For me, I go with Bell's 4th 'way out', at least for now. The wave function is part of a calculation recipe. Why it works, we simply don't know. Why it leads to non-local correlations, we don't know either.  But the formalism of QM simply leads to the conclusion that non-local correlations are possible.

 

 

Edited by Eise
Added "or interaction"
Link to comment
Share on other sites

I certainly haven't quoted Bell, Aspect, Einstein, et al.
I'm not even sure of the timeline without researching it.

I do have a problem with superluminal tranfer of information, and the definition Bangstrom has provided for 'non'locality' does just that.
So that definition doesn't fly.

Perhaps we are forgetting that we are dealing with models of the undelying reality, and while we can construct physical models of macroscopic processess and events, we are forever relegated to using only mathematical models of quantum processess and events.
They cannot be described in terms of 'everyday', common physicality.
We are, in effect, seeing something happen, mathematically, in one place, and again, in another place, at great separation, and concluding that something must be communicating between these two mathematical expressions.
We are certainly not dealing with placing a weight on one end of a fulcrum and causing the other end to rise, even though that can also be explained with a ( classical ) mathematical model.

We need a better understanding of what 'non-locality' means in a probabilistic mathematical model.

And thanks for keeping us honest, Eise.

Link to comment
Share on other sites

  

33 minutes ago, Eise said:

Hui, Joigus, now you have fallen into a trap. If it is your own, or the 'Journal de physique' (or some other source) I don't know, but Bell is citing Einstein in your highlighted passages:

image.png.aa46138ce8e9be3861735e19d2287334.png

 

Here Bell is speaking for himself:

image.png.c76276dd4dfa9737a746ec2bd0429306.png

And after his argument:

image.png.409adc249b607762f2ec9cfc631bea53.png

It is obvious that Bell doesn't like this conclusion, and discusses 4 ways out:

  • QM is wrong, at least in the case of such situations
  • Superdeterminism (he doesn't name it like that, but is clear that he is pointing at that)
  • Lorentz transformations are not valid
  • There is no reality below some "classical" "macroscopic" level (quotation marks from the original)

Concerning the first point: Aspect was still working on his experiments, and Bell refers to that. His comment:

image.png.a390772023ecfafd62887eb73fb0754f.png

We know how the experiment went out...

From other articles, I have reason to believe that he was going for the first point, i.e. that QM is incomplete. He was puzzled by the results of the Clauser and Aspect experiments.

Bell says exactly the opposite of what you are saying.

I think it is important that you all, discutants (my word creation?), are very clear with the words you are using. I give a few proposals:

  1. action: a physical process, where energy and momentum are exchanged, and so special relativity applies
  2. correlation: as in the example of the shoes in the boxes

To 1: even Bell is confusing here, because he says "They cannot be explained, that is to say, without action at a distance." (Bold by me)

To 2: I would say that the Bell inequalities, together with the confirmation that they do not hold in QM in experiments, show that QM has stronger correlations than local realistic theories allow.

For me, I go with Bell's 4th 'way out', at least for now. The wave function is part of a calculation recipe. Why it works, we simply don't know. Why it leads to non-local correlations, we don't know either.

 

 

You caught me. It's Einstein speaking there. +1

My only excuse is that I was pressed to answer to a rather "entangled" physical question in terms of quotes of famous people, a field in which I'm anything but confortable. I'd rather discuss things in terms of mathematical statements under premises that have passed the test of time, both because they've been analysed by many competent people --theorists and experimentalists alike--, and because they've passed the experimental tests themselves.

It is clear to me though that Bell --especially in his last years-- preferred to save locality and work instead on alternative extensions of quantum mechanics. I also know that from biographical testimonies that attest to the fact that Bell was very ambivalent about the interpretation of his famous theorem. Feynman and Gell-Mann, for example, shared the view that quantum correlations express nothing peculiarly non-local, but only carry with them a version of non-separability that's intrinsically quantum, and cannot be reproduced by any classical model. Most other important people in the field of theoretical physics, TBH, look at this with an absolute lack of interest.

The reason why I cannot accept that this problem can be ascertained in terms of celebrity-quotes is, of course, that the views of different experts do not completely overlap, that sometimes they are ambiguous when in the process of understanding a particularly confusing topic, and that, perhaps as a consequence of that, their opinions end up changing with time.

Because I'm not allowed to use mathematics, apparently, I will try to work on diagrams and logical outlines to further clarify my points.

I do agree with your definitions 1 and 2 of --respectively-- action and correlation.

My main point is that the implications of quantum correlations say nothing about locality, as they are encapsulated in the quantum state at t=0, when the singlet state was prepared, so they were there all along, and that I will stand by no matter what Bell, or anybody else, said at a particular time in history.

What happens to the wave function after we make a measurement? We can discuss that if you, or anybody else, want. But that's a different matter.

Let me add something else: Only people who adhere to the projection postulate of Copenhagen have this problem. That's where the fiction of non-locality arises.

Why Bell might have been "fooled" by that at some point? --if that's the case--. I don't know. My best guess is that he was a pioneer in these things and he was still in two minds about some aspects.

Do you agree with my statement summarising the EPR argument? If you do, we can go to the next step: Why David Bohm took the discussion to the case of spin, because in its original formulation in terms of position-momentum, the argument is flawed:

On 9/24/2022 at 1:01 PM, joigus said:

EPR: If you can predict with absolute certainty the result of an experiment without in any way disturbing the system, there must be some element of reality underlying it. Quantum mechanics says that certain pairings of observables are incompatible, say A and B. If I can exploit a conservation law that's valid for at least one of them, say A, in a bipartite system (A1+A= constant) and measure A in part 1, and B in part 2, I can infer what the value of A2 is without actually measuring it. I can, at the same time (within a space-like interval) measure B for 2, that is B2, with as much precision as desired, and I would have proven that quantum description of reality is incomplete, because I would have the values of A2 and B2, which quantum mechanics declares as incompatible. In a nutshell: Either quantum mechanics is incomplete, or your wave function would have to be updated superluminally, to make this incompatible character of A and B persist. 

Link to comment
Share on other sites

3 hours ago, joigus said:

or your wave function would have to be updated superluminally,

CAVEAT: These words are absolutely key. Copenhagen's prescription that we do a normalised projection of the amplitude that's valid in all of space at one particular time --so that components of the wave function that were propagating away have to be killed off instantly or die down quickly enough-- is why the illusion of non-locality persists.

It has no observable consequences for obvious reasons: The components that die down don't carry any observable consequence, as zero times anything gives zero.

Now, we can say infinitely many things* about those components, that essentially are the same in minimal semantic terms.

A very popular one is MWI. Those components are taken to an alternative universe.

Bohm's double solution: Those components propagate away, like lost astronauts, without ever being seen again --empty waves.

Let me give you another one:

Those components become "transparent." "Transparent" being another fancy meta-variable that tells you they can never be measured.

Etc.

You can invent your own.

That's what we call "the many interpretations of quantum mechanics."

* If we want to save unitarity, linearity, and unblemished locality = Schrödinger equation

Edited by joigus
minor addition
Link to comment
Share on other sites

8 hours ago, MigL said:

Perhaps we are forgetting that we are dealing with models of the undelying reality, and while we can construct physical models of macroscopic processess and events, we are forever relegated to using only mathematical models of quantum processess and events.
They cannot be described in terms of 'everyday', common physicality.

We are not just dealing with “models” we are dealing with actual physical experiments and the physical measurements describe events that defy our ‘common sense’ classical view of physicality. That doesn’t mean they are not real.

8 hours ago, MigL said:

We are, in effect, seeing something happen, mathematically, in one place, and again, in another place, at great separation, and concluding that something must be communicating between these two mathematical expressions.

The mathematics is used to describe what we are first observing with physical measurements of reproducible quantum experiments suggesting a non-local connection but not necessarily a communication. The conflict we observe is primarily physical and the mathematics follows from that

 

8 hours ago, MigL said:

We are certainly not dealing with placing a weight on one end of a fulcrum and causing the other end to rise, even though that can also be explained with a ( classical ) mathematical model.

The main difference between QM and classical physics is that classical physics requires a physical connection between a cause and effect while QM does not.

8 hours ago, MigL said:

We are certainly not dealing with placing a weight on one end of a fulcrum and causing the other end to rise, even though that can also be explained with a ( classical ) mathematical model.

The main difference between QM and classical physics is that the classical physics requires a physical connection between a cause and effect while QM does not.


 

Edited by bangstrom
Added the last sentence that failed to come through.
Link to comment
Share on other sites

18 hours ago, joigus said:

My only excuse is that I was pressed to answer to a rather "entangled" physical question in terms of quotes of famous people, a field in which I'm anything but confortable. I'd rather discuss things in terms of mathematical statements under premises that have passed the test of time, both because they've been analysed by many competent people --theorists and experimentalists alike--, and because they've passed the experimental tests themselves.

I understand that. For me however the mathematics of QM is a book with about 5 seals (if you know what I mean). What I am interested in is how physicists came to their hypotheses, and how these were empirically underpinned. (And of course the methodological and philosophical assumptions that go into these hypotheses). I always felt a bit disturbed by the lectures at university because physics was always presented as a ready made building. History of physics was one of my favourite subjects (and still is). And in my philosophy study, I was trained in reading (old) texts.

I notice a few ambiguities in your position. First you said:

On 9/21/2022 at 5:22 PM, joigus said:

Bell finally sets the record straight and publishes his famous paper on Bertlemann's socks and the nature of reality.

I took this as 'final statement of Bell in this matter', but you reacted on it as if you read 'final statement in this matter' (in general). And now you are saying:

18 hours ago, joigus said:

It is clear to me though that Bell --especially in his last years-- preferred to save locality and work instead on alternative extensions of quantum mechanics.

Wouldn't be 'final' in his last years?

Sorry for the ant fucking, but hey, I am a philosopher by education. ;) (Not profession...)

18 hours ago, joigus said:

Feynman and Gell-Mann, for example, shared the view that quantum correlations express nothing peculiarly non-local, but only carry with them a version of non-separability that's intrinsically quantum, and cannot be reproduced by any classical model.

What is non-separability when a spacelike distance is involved other than non-locality? (Beware: correlation, not causation.)

19 hours ago, joigus said:

Do you agree with my statement summarising the EPR argument?

More or less.

19 hours ago, joigus said:

If you can predict with absolute certainty the result of an experiment without in any way disturbing the system, there must be some element of reality underlying it.

"Some element", yes. But we have no idea what this element is.

Another problem I think I have is with:

19 hours ago, joigus said:

Either quantum mechanics is incomplete, or your wave function would have to be updated superluminally

As for me the wave function is not a physical object, there is nothing physically updated. The wave function is an idea, and there is no problem for ideas to be superluminal (now I think about the war in the Ukraine, and now I am thinking about the Andromeda galaxy. Wow, 2 million lightyears in less than a second!)

I know that the violations of Bell's inequalities roll out of the math of QM. You know the story that Feynman threw Clauser out of his office, because implicitly he was doubting QM? We know that QM predictions are empirically valid. But we don't know why. And my guess is we never will.

19 hours ago, MigL said:

I do have a problem with superluminal tranfer of information, and the definition Bangstrom has provided for 'non'locality' does just that.

I agree with that; however I am not so sure if it is Bangstrom's imprecise language (but he is not the only one guilty of that..). I however suppose that Bangstrom agrees that no information is transferred, and that the correlation between the remote measurements is not a causal relationship. @bangstrom: could you clarify, please, as precise as you can?

19 hours ago, MigL said:

Perhaps we are forgetting that we are dealing with models of the undelying reality, and while we can construct physical models of macroscopic processess and events, we are forever relegated to using only mathematical models of quantum processess and events.

I agree. But it is surprising that nature does something we can derive mathematically only, without knowing the ontological status of the wave function. I think I more or less agree with Bangstrom here:

11 hours ago, bangstrom said:

We are not just dealing with “models” we are dealing with actual physical experiments and the physical measurements describe events that defy our ‘common sense’ classical view of physicality. That doesn’t mean they are not real.

New word alert!

11 hours ago, bangstrom said:

The mathematics is used to describe what we are first observing with physical measurements of reproducible quantum experiments suggesting a non-local connection but not necessarily a communication.

Try to define these words, or try to say what you want to say without them.

11 hours ago, bangstrom said:

The main difference between QM and classical physics is that the classical physics requires a physical connection between a cause and effect while QM does not.

Nope. The correlation is not causal, as with the shoes in the boxes. The correlation however is stronger than we classically expect.

Link to comment
Share on other sites

Now I got confused in my reading myself: Bangstrom is saying that the 'connection' (whatever that may be) is not causal. I must add that we have to torture nature to the limit, to empirically observe these correlations.

Link to comment
Share on other sites

Fair enough, @Eise. If not satisfy, I will try to answer to all your concerns. But 1st of all let me tell you that there are two statements of yours that worry me a bit, as they seem to "protect" some kind of future dismissal on your part of anything I can say. I'm sure that's not what you meant, because of your proven intellectual honesty:

1)

3 hours ago, Eise said:

For me however the mathematics of QM is a book with about 5 seals (if you know what I mean).

and 2)

23 hours ago, joigus said:

Do you agree with my statement summarising the EPR argument?

 

3 hours ago, Eise said:

More or less.

You clarify the second point later, but I hope that doesn't mean 1) I cannot refer to quantum mechanics itself, in its closed mathematical form, in order to argue about what quantum mechanics itself means or implies. And 2) There's something about my statement of the EPR argument you don't agree with, but you reserve the right to bring it up later. Again, I'm sure that's not what you mean, but I need to be sure. Nothing would give me more intellectual satisfaction than giving someone like you full intellectual satisfaction.

Then you go on to say,

3 hours ago, Eise said:

I took this as 'final statement of Bell in this matter', but you reacted on it as if you read 'final statement in this matter' (in general). And now you are saying: [...]

3 hours ago, Eise said:

Wouldn't be 'final' in his last years?

Sorry for the ant fucking, but hey, I am a philosopher by education. ;) (Not profession...)

Sorry, bad choice of idiom on my part. "Sets the record straight" is too strong a statement if we want to be historically accurate. The reason is that Bell's observation on Bertlmann's socks whas a real epiphany for my own understanding, but I assume it's not necessarily so for everybody else, perhaps not even for Bell himself. Although it was for Murray Gell-Mann, as I think I've proven with the posting of the interview. It's only 4' 44'' and worth every second in diamond's carats. Particularly revealing is what he says at 3' 00'':

Quote

"People say loosely, crudely, wrongly, that when you measure one of the photons it does something to the other one. It doesn't!! All that happens is you measure a property of one and you learn the corresponding property of the other one." 

This completely coincides with what @swansont has manifested elsewhere on these forums. It also agrees with my understanding of the question. And Bell's example of the socks personally was my wake-up call --or bell, if I may be allowed the pun. ;) 

In my life, I've gone through two major epiphanies concerning these matters:

E1) I was trying to explain quantum mechanics to my little sister circa 1995 when I suddenly realised you don't need to have any reduction of the wave packet if the wave function objectively represents infinitely many electrons from the get-go. I went to my trusty QM teacher and he told me Leslie Ballentine had already thought of that. Bummer, but nice.

E2) I realised John Bell's observation on Bertlmann's socks clearly suggested/implied that the correlations --potentially, if you will-- say nothing whatsoever about locality or the lack of it. Was John S. Bell aware of it? I don't know, and I don't have access to his deathbed words, so...

Then you say,

3 hours ago, Eise said:

"Some element", yes. But we have no idea what this element is.

 

This seems to be the subject of your "misgivings" concerning my statement of EPR.

Well, Clause, Horne, Shimony, Bell, Von Neumann, Gleason, Kochen, and Specker, at the very least, took care of that. And that's because they assume a dependence of definite variables of any kind of which the all the possible observed values (eigenvalues) may be a function of. A local (meaning numeric value to numeric value) function (not involving non-commuting stuff amongst each other of any kind). In such a way that you can map hidden variable to eigenvalue point-to-point; value-to-value.

The irrefutable consequence is that you can't. You need non-commutativity from the beginning.

Von Neumann understood this. Coleman understood this. Gell-Mann understood this.

But the message is sooooo incredibly difficult to get across, as Gell-Mann shrewdly points out.

Let's call those quantum correlations colourful correlations if you will, just in order to see they imply nothing about spacetime.

Colourful correlations are colourful at t=0 when the singlet state is prepared at one point in space.

Colourful correlations are colourful at t=1 when the singlet state has evolved 1 light-second apart.

Colourful correlations are colourful at t=2 when the singlet state has evolved 2 light-seconds apart.

...

Etc.

Are we there yet? Because if we are, we can proceed from there.

Now we perfom a measurement, and all hell breaks loose, the worms get out of the can, and Alice's rabbit is deep down the hole. It's then when your comment about what the wave function objectively represents or to what extent it does is invested with the utmost relevance, and we may never be able to agree on what happens to the wave function, especially if you stick to your guns that the wave function objectively represents just a human idea, and nothing more. I do not hold that view, for reasons I may be able to explain later.

It's such a pleasure to discuss the matter with you, @Eise.

 

Edited by joigus
minor addition
Link to comment
Share on other sites

On 9/25/2022 at 8:39 AM, joigus said:

Feynman and Gell-Mann, for example, shared the view that quantum correlations express nothing peculiarly non-local, but only carry with them a version of non-separability that's intrinsically quantum, and cannot be reproduced by any classical model.

Separability in space but not time is what makes the connection non-local. This is impossible in the classical model but possible for quantum correlations.

I do read your what you write and try to follow the math but I find it unconvincing because your views are contrary to nearly everything I read from reliable outside sources often including ones whose names you drop as having the same views as yours.

What you say may be true for Gell-Mann and Kracklauer to name one other claiming that QM is non-local but I don’t think that applies to Feynman. The Wheeler-Feynman Absorber theory had instant, non-local connections going both forward and backward in time preceding an actual EM transfer of energy. Feynman interpreted the transaction as a direct action between emitter and absorber.

As John Wheeler said, “I have always believed that electrodynamics is completely symmetric between events running both forward and backward in time. There is nothing fundamental in the laws that makes things run in only one direction. The one-way flow of events that is observed is of statistical origin. It comes about because of the large number of particles in the universe that can interact with each other.”

The W-F absorber theory never caught traction likely because they explained their theory by inventing swarms of photons moving at every possible speed, including all speeds in reverse, and taking every possible path between the sender and absorber of an EM signal.

The W-F Absorber theory survives today as John Cramer’s scrubbed clean version of the old theory.

On 9/25/2022 at 8:39 AM, joigus said:

Because I'm not allowed to use mathematics, apparently, I will try to work on diagrams and logical outlines to further clarify my points.

 

Your saying you are not allowed to use math is like me claiming I am not allowed to use quotes. I am not the only audience here and this is not my forum.

On 9/25/2022 at 11:40 AM, joigus said:

CAVEAT: These words are absolutely key. Copenhagen's prescription that we do a normalised projection of the amplitude that's valid in all of space at one particular time --so that components of the wave function that were propagating away have to be killed off instantly or die down quickly enough-- is why the illusion of non-locality persists.

 A wave function does not carry signals that “propagate’ in any direction.

On 9/25/2022 at 11:40 AM, joigus said:

It has no observable consequences for obvious reasons: The components that die down don't carry any observable consequence, as zero times anything gives zero.

A time zero between remote events can’t be measured but the timing of decoherence can be measured up to technical limits and it has been measured to be far faster than ‘light speed’.

 

On 9/25/2022 at 11:40 AM, joigus said:

A very popular one is MWI. Those components are taken to an alternative universe.

Bohm's double solution: Those components propagate away, like lost astronauts, without ever being seen again --empty waves.

The MWI and SD and likely Bohm’s double solution are not scientific in that they eliminate Popper’s “falsifiability” by vanishing any contrary evidence.

On 9/25/2022 at 11:40 AM, joigus said:

* If we want to save unitarity, linearity, and unblemished locality = Schrödinger equation

Unblemished locality of the wave function? The S. wave function itself functions non-locally.

The theoretical physicist Hugo Tetrode demonstrated the non-locality of the wave function with several pages of math explaining how the wave function applies simultaneously over any possible distance and that it extends both forward and backward in time.

Tetrode published this in 1921 in Zeitschrift fur Physik, volume 6 as I recall. He later marred is good work by trying to make the wave function sound local in volume 10 as did Wheeler and Feynman much later.

Link to comment
Share on other sites

On 9/25/2022 at 5:54 PM, bangstrom said:

We are not just dealing with “models” we are dealing with actual physical experiments and the physical measurements describe events that defy our ‘common sense’ classical view of physicality. That doesn’t mean they are not real.

On the contrary, the only place we are dealing with actual physical experiments is at either end, where the observations are made; and the two observations are perfectly explainable by correlation.
At any point in between we have a mathematical abstraction that says the states are undefined, until said observations are made;  and that throws a wrench into the works.
Where is the reality in that intervening space ?
For all intents and purposes, there is no reality until those observations are made.

If you want to argue that mathematical expresiions can be non-local, I could be persuaded to agree.
Just as Eise's thinking can be non-local by thinking about war in the Ukraine and the Andromeda galaxy in the next instant, the probability of a coin flip showing heads is exactly the same in Ukraine as in Andromeda.

Is that your definition of non-locality ?

2 hours ago, bangstrom said:

Hugo Tetrode demonstrated the non-locality of the wave function ... explaining how the wave function applies simultaneously over any possible distance and that it extends both forward and backward in time.

Is that what you would mean by the probabilities described by the mathematical wave function being non-local ?

Edited by MigL
Link to comment
Share on other sites

51 minutes ago, bangstrom said:

Separability in space but not time is what makes the connection non-local. This is impossible in the classical model but possible for quantum correlations.

I think you mean non-separability in space. I haven't the foggiest idea what separability in time means, as separable or not is an attribute of the state that depends on how it factorises --or not-- in the particle-identity tags* (state)12=(state)1(state)2 --separable-- or, as is the case for the singlet state (state)12=(state)1(state)2-(state)2(state)1 --non-separable.

Once an inertial system is chosen, there's only one coordinate time.

On the other hand, it's perfectly possible to make a classical-mechanical model of interaction non-local. Newtonian interactions at a distance are a perfect example. So no, it's not a discriminating attribute between classical and quantum. It's just an artifact of the approximation. If someone removed the Sun from its place, it would take us a little over 8 minutes to be able to tell. We have no experiment that says that, but we're pretty sure it's true.

* Even though particle identity doesn't really mean "identity" as we understand it in the classical world. It's a dummy tag, really, a labelling artifact.

1 hour ago, bangstrom said:

What you say may be true for Gell-Mann and Kracklauer to name one other claiming that QM is non-local but I don’t think that applies to Feynman. The Wheeler-Feynman Absorber theory had instant, non-local connections going both forward and backward in time preceding an actual EM transfer of energy. Feynman interpreted the transaction as a direct action between emitter and absorber.

(My emphasis.)

I think you mean local, but that's probably a typo.

FW theory. This is a theory of classical (not quantum) electrodynamics in which Feynman, for reasons that were purely heuristic --see below--, wanted to dispose of the field altogether, and assume a direct interaction between charged particles that gave rise to a completely local, relativistically causal electrodynamics.

Quote
Quote
A heuristic hypothesis is the temporary prediction of an unknown which is made to simplify the solution phase. It is made during a certain part of the calculation phase, it is valid only if the results it yields are coherent with it and it can be refined in a later stage after it has helped to find a solution.
 

 

Google: "Heuristic hypothesis"

In this method Feynman, after a suggestion from Wheeler, imposed the condition that the force per unit charge (the field in disguise) be half-retarded and half-advanced. But of course, the final constriction is that the total solution from all the electrons in the universe propagated in a retarded way and be totally causal and local. Feynman found that he had to impose the condition that spatial infinity be a perfect absorber of EM radiation. Pretty weird, but it worked mathematically.

Observation: You can perhaps always introduce an interaction between pairs ab initio that is formally non-local, and then impose boundary conditions that restore locality --in this case, the perfect absorber at infinity. You can always have an infinite expansion in spatial derivatives of the interaction (and therefore, non-local) but you impose that the sum of all the infinitely many terms be local. You can play with that ad infinitum. It's just a change of variables.

In fact, I know of another perfect example in which the separation of variables makes locality non-manifest. The so-called MHV approach to solve quantum field theories.

The reason that we today do not believe that the WF model is telling us anything significant about non-locality is, of course, that we happen to know that the world is quantum, and not classical, on the one hand; and on the other hand, that the alleged non-locality has no observable consequences, because of reasons I've just explained. When you study quantum electrodynamics, you see very clearly that the advanced waves correspond to antiparticles, not to any bizarre waves propagating backwards in time.

If you're surprised by this mathematical fact, it's very understandable: In quantum field theory, if you want to have field variables that commute at space-like intervals --and therefore have a theory that preserves causality, and forbids superluminal propagation-- you actually need positrons. These are not actually waves propagating backwards in time, they're only degrees of freedom of the field for which the amplitudes have to be "interpreted" backwards, so to speak.

This is key to the Feynman prescription for the propagator. Feynman explains this point --not very clearly, I must say-- in this famous Dirac-Memorial conference --he starts at 10' 35'' with the words "now, here's a surprise":

Here's the most revealing part of the transcript. Pay attention, please, to the words "apparently moving backwards in time."

image.thumb.png.526fb4c743312b58956d58a18dafdc37.png

So that's all there is to it in the quantum version. You need antiparticles if you want to guarantee locality and causality. Feynman, of course, never doubted locality and relativistic causality.

2 hours ago, bangstrom said:

A wave function does not carry signals that “propagate’ in any direction.

Well, I'm sorry. It does. They all are quadratic expressions in the wave function, and satisfy local conservation law of energy, momentum, and angular momentum (both orbital and spin.) This is all mainstream. See below for local conservation of probability density and continuity equation, plus Wiki reference added.

2 hours ago, bangstrom said:

A time zero between remote events can’t be measured but the timing of decoherence can be measured up to technical limits and it has been measured to be far faster than ‘light speed’.

 

What you're measuring there is a correlation that was there from the get-go. No wonder it "is superluminal" to you --and perhaps others who don't understand this particular point--, as it is not the speed of anything. I've told you before. The Book of Psalms is the same everywhere, not because different versions of it are communicating telepathically with each other, but because they were written long before the present time. Correlation is not causation, nor necessarily interaction.

2 hours ago, bangstrom said:

The MWI and SD and likely Bohm’s double solution are not scientific in that they eliminate Popper’s “falsifiability” by vanishing any contrary evidence.

You've got a point there, but that's not totally true. We always have our reliable good old Ockam's razor.

There are also TIQM (transactional interpretation of quantum mechanics), DH (decoherent histories approach), Nelson's SQM (stochastic quantum mechanics), etc. None of these models have been proven falsifiable, which is not the same as saying they are not falsifiable.

What's SD?

2 hours ago, bangstrom said:

Unblemished locality of the wave function? The S. wave function itself functions non-locally.

That is not correct. So local it is that a simple calculation from the Schrödinger equation allows you to derive the continuity equation for the square of the absolute value of the wave function. Probability satisfies the accepted paradigm of a local conservation law.

Probability flux getting out of surface = - time rate of variation of probability inside the surface

Totally dumbed down: No probability can get out of a volume without going through its surface. This is a theorem you can prove from the Schrödinger equation. Here it is:

https://en.wikipedia.org/wiki/Schrödinger_equation#Probability_current

I've tried to simplify the maths, but I can provide you a complete and detailed proof, if you're interested.

If you sample the web for opinions on this, you will find lots of confusion. For example:

Quote

Yes, the Schrodinger equation and the evolution of the wavefunction that follows from it is local and unitary. Unitary means that the time evolution of the wavefunction is unique and completely determined by the initial conditions. It is therefore deterministic.

Reference: https://www.physicsforums.com/threads/schroedinger-local-and-deterministic.387951/

Quote

But what's wrong about saying the Schrödinger equation is local and deterministic? Mathematically it does look so.

Reference: https://www.physicsforums.com/threads/schroedinger-local-and-deterministic.387951/

And more high-level:

https://physics.stackexchange.com/questions/18762/locality-in-quantum-mechanics

Etc. Even if you don't understand the maths, quickly skimming through the previous forums will help you size up the level of confusion.

...

...

And finally, Hugo Tetrode, 1921-22? Well, yeah. Quantum mechanics was completed around 1926. So I'm gonna pass on that.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.