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crowded quantum information


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2 hours ago, Mitcher said:

Didn't they already conduct real experiments in the lab about this ?

I'd like to hear about it.

11 minutes ago, bangstrom said:

The cat is a macro object so QM does not apply but something similar happens at the particle level.

The contingency was there is a potentially decaying radioisotope in the box, no?

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18 minutes ago, bangstrom said:

Does the word "projection" sound familiar?

Sure. It's the main theme of my cover photo. Not that you noticed, I know. I've spent a great deal of time thinking about spectral analysis.

22 minutes ago, bangstrom said:

Where were you when we discussed this before?

 

I must have been half awake, half asleep, like a Schrödinger's sleepy cat. In any case, I cannot be held accountable for not having been here when the discussion surfaced before.

Here's the argument for you (again!!):

Einstein: 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 (the foreshadowing of hidden variables.)

Bohm: Let's take that to the case of spin, and see what happens. (Bohm had already invented a quite alright --but not totally satisfactory on many levels-- set of hidden variables for position-momentum.)

Clauser-Horne-Holt-Shimoni-Bell: If there were some "hidden variables" associated to spin there would have to be a non-local interaction explaining the correlations. If quantum mechanical spin-factor of the state is all there is to it (spin eigenvalues as results of experiments,) there wouldn't.

Repeat:

wouldn't

wouldn't

wouldn't

This is a case of there isn't, so there wouldn't.

Aspect: quantum mechanical correlations are correct within the allowance of detector noise.

Conclusion: Quantum mechanics is correct, so there needn't be any non-local interactions.

You see? It's a little bit involved, but it's not foggy or difficult at all.

Let me guess: No. You don't want to accept it. You don't want anything to do with it. Don't worry. You're not alone. For all you've told me, Neadau and Kafattose haven't understood it either. Or just won't accept it. Or want to sell some more books, or... I don't know and, quite frankly, I don't care.

19 minutes ago, bangstrom said:

You got it. Are you saying that entanglement where two remote particle are connected as if they were side so that an action upon one instantly affects the other, is not a superluminal connection?

Yes, I got it, but you still didn't. No. Nothing you do on one affects the other. If you think about Jennifer Aniston* now, and I do too, at the same time --on the same inertial system--, it's just because we've both learnt about Jennifer Aniston before, not because our neurons have communicated "telepathically."

The funny thing about quantum mechanics is that, all along, assuming that my Jennifer Aniston version is a brunette, and yours is a blonde, cannot be assumed to be in a definite state of blondness or brunetteness without incurring contradiction, non-locality, negative probabilities, etc.

You need at least 3 observables concerning Jennifer Aniston to prove that this is the case if Jennifer Aniston were a quantum object. No pair of gloves, or Jennifer Aniston, can tell you that. That's what John Bell's brilliance was about.

And the test that will stand the (experimental) test of time, I'm sure:

Show me the superluminal signal.

Show me the superluminal signal.

Show me the superluminal signal.

Show me the superluminal signal.

Again?

Show me the superluminal signal.

Show me the superluminal signal.

...

*This example is in jest. Some neuroscientists thought they had found "Jennifer Aniston's neuron" in some neurosurgery patients because the same neuron got excited whenever they showed them a picture of J.A.

14 minutes ago, joigus said:

3 observables

3 non-commuting observables, and not just any old pair. Some triplets fall within the domain that classical thinking can explain.

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7 hours ago, NTuft said:

You propose that the act of measurement caused the spin state of the unmeasured particle? Talk about anthropometry. It was spinning down before that.

Not exactly, the act of measurement caused the instant (superluminal) loss of entanglement between the particles (decoherence) and the particles emerged with identifiable spins. The spins were indeterminate prior to the first measurement and became determinate, instantly, and at both ends, with the loss of entanglement.

The conventional explanation is that they were in a state of “superposition” prior to observation.

I suspect the particles were spinning before entanglement but one question is, ‘Are the spins after entanglement the same as they were at the beginning or was their emergence anti-correlated but random? I favor the random interpretation.

There is always something anthropometric about our observations of quantum events. We can not measure an event without disturbing the quantum status quo and one observation initiates changes.

 

1 hour ago, NTuft said:
3 hours ago, Mitcher said:

Didn't they already conduct real experiments in the lab about this ?

I'd like to hear about it.

Yes, they did test the dead/alive cat thought experiment but not with a cat or a radioactive isotope.

The first tests were statistical tests of Bell's inequality with anti-correlated photons. Instead of dead/alive cats they used entangled, this-way/that-way polarized photons. The results suggested that a photon is neither polarized one way or the other until first measured like Schroedinger's dead/alive cat and the quantum identities did not become fixed until the instant of the first observation.

 

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2 hours ago, joigus said:
3 hours ago, bangstrom said:

Does the word "projection" sound familiar?

Sure. It's the main theme of my cover photo. Not that you noticed, I know. I've spent a great deal of time thinking about spectral analysis.

There are two definitions of "projection". One is about light and another is the name of a defense mechanism.

2 hours ago, joigus said:

Clauser-Horne-Holt-Shimoni-Bell: If there were some "hidden variables" associated to spin there would have to be a non-local interaction explaining the correlations. If quantum mechanical spin-factor of the state is all there is to it (spin eigenvalues as results of experiments,) there wouldn't.

I find the first sentence is contrary to the conventional interpretation. If there ARE “hidden variables” we would need no non-local interaction to explain correlations. Hidden variables would provide the explanation.

Tests of Bell’s Inequalities ruled out the presence of hidden variables so non-local interaction became the default explanation.

The second sentence appears to assume that spin eigenvalues exist prior to observation but experiments suggest that they do not.

2 hours ago, joigus said:

Nothing you do on one affects the other.

This is classical physics and the now discredited assumption found in the EPR paper. Entanglement is an exception where what happens to one particle instantly affects its entangled partner no matter what the distance. They could be galaxies apart.

The second sentence appears to assume that spin eigenvalues exist prior to observation but experiments suggest that they do not.

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4 hours ago, bangstrom said:

There are two definitions of "projection". One is about light and another is the name of a defense mechanism.

Wrong. A projection, in the sense that it's used in quantum mechanics, is a linear operator P, such that P2=P. Projections are automatically Hermitian, and therefore their spectrum is real. In fact, any eigenvalue of a projector is either 1 or 0. That's why they are also sometimes called yes/no observables. There's nothing necessarily about light concerning projectors. They make sense for either fermions or bosons, massless or massive. In Dirac notation they're always of the form \( \left|q\right\rangle \left\langle q\right| \) or sums of similar orthogonal terms.

Here: https://quantummechanics.ucsd.edu/ph130a/130_notes/node185.html

 

4 hours ago, bangstrom said:

I find the first sentence is contrary to the conventional interpretation.

You find many things that are not there. It's what Murray Gell-Mann says in the video that I posted. It's also what Sidney Coleman says in this lecture:

The transcript:

https://arxiv.org/pdf/2011.12671.pdf

More in detail:

image.png.1f4a29c32b50cbaa5078d9ec7e6f0cc5.png

Sidney Coleman introduces this fictional character, Dr. Diehard, for the purposes of illustrating the classical thinking in terms of hidden variables. It is precisely because there can be no superluminal influence that we know that, if QM is correct --which it is--, there can be no hidden variables. You, and many other people who've run wild with this term "non-locality," have got the argument completely backwards.

4 hours ago, bangstrom said:

This is classical physics and the now discredited assumption found in the EPR paper. Entanglement is an exception where what happens to one particle instantly affects its entangled partner no matter what the distance. They could be galaxies apart.

Wrong again. It is standard quantum mechanics:

https://en.wikipedia.org/wiki/No-communication_theorem

Even people who are still thinking about teleportation --no experimental evidence, just exploring logical loopholes--, admit that quantum mechanics would have to be superseded with something else, if superluminal signals were to be accepted as a possibility:

https://plato.stanford.edu/entries/qm-action-distance/#NecSufConForSupSig

Quote

It is commonly agreed that in quantum phenomena, superluminal signaling is impossible in practice. Moreover, many believe that such signaling is excluded in principle by the so-called ‘no-signaling theorem’ (for proofs of this theorem, see Eberhard 1978, Ghirardi, Rimini and Weber 1980, Jordan 1983, Shimony 1984, Redhead 1987, pp. 113-116 and 118). It is thus frequently claimed with respect to EPR/B experiments that there is no such thing as a Bell telephone, namely a telephone that could exploit the violation of the Bell inequalities for superluminal signaling of information.[31]

The no-signaling theorem demonstrates that orthodox quantum mechanics excludes any possibility of superluminal signaling in the EPR/B experiment. According to this theory, no controllable physical factor in the L-wing, such as the setting of the L-measurement apparatus, can take advantage of the entanglement between the systems in the L- and the R-wing to influence the statistics of the measurement outcomes (or any other observable) in the R-wing. As we have seen in section 5.1.1, the orthodox theory is at best incomplete. Thus, the fact that it excludes superluminal signaling does not imply that other quantum theories or interpretations of the orthodox theory also exclude such signaling. Yet, if the orthodox theory is empirically adequate, as the consensus has it, its statistical predictions obtain, and accordingly superluminal signaling will be excluded as a matter of fact; for if this theory is empirically adequate, any quantum theory will have to reproduce its statistics, including the exclusion of any actual superluminal signaling.

But the no-signaling theorem does not demonstrate that superluminal signaling would be impossible if orthodox quantum mechanics were not empirically adequate. Furthermore, this theorem does not show that superluminal signaling is in principle impossible in the quantum realm as depicted by other theories, which actually reproduce the statistics of orthodox quantum mechanics but do not prohibit in theory the violation of this statistics. In sections 7.2-7.3, we shall consider the in-principle possibility of superluminal signaling in certain collapse and no-collapse interpretations of quantum mechanics. But, first, we need to consider the necessary and sufficient conditions for superluminal signaling.

(My emphasis in boldface characters.)

6 hours ago, bangstrom said:

There is always something anthropometric about our observations of quantum events. We can not measure an event without disturbing the quantum status quo and one observation initiates changes.

 

Absolutely not. It could be an octopus observing a photon, or no conscious being at all. Like, eg, a photodetector.

 

Edited by joigus
Latex editing
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11 hours ago, bangstrom said:

Yes, they did test the dead/alive cat thought experiment but not with a cat or a radioactive isotope.

The first tests were statistical tests of Bell's inequality with anti-correlated photons. Instead of dead/alive cats they used entangled, this-way/that-way polarized photons. The results suggested that a photon is neither polarized one way or the other until first measured like Schroedinger's dead/alive cat and the quantum identities did not become fixed until the instant of the first observation.

And again you are incorrect.

The so-called Schrödinger-cat experiments refer to producing quantum superpositions of mesoscopic systems (size bigger than a single elementary particle, but still not daily-life size). The results were published in 2018, it was made with microbeams of silicon 10 micrometers long and 1x0.25 micrometers across, keeping quantum coherence all along. This is the experiment:

https://www.nature.com/articles/s41586-018-0036-z

Not at all what the Aspect experiment was about:

https://journals.aps.org/prd/abstract/10.1103/PhysRevD.14.1944

This is the title:

Quote

Proposed experiment to test the nonseparability of quantum mechanics

Alain Aspect
Phys. Rev. D 14, 1944 – Published 15 October 1976

(My emphasis in colour.)

Still today, people misread what Alain Aspect set out to prove: The non-separability of quantum mechanics.

Both things (Schrödinger cats, in the sense of mesoscopic superpositions) and non-separability (Bell's inequalities, the GHZ test, etc.) are very different things. You've mistaken one for the other.

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WE are not considering particles, which exist in isolation, and must have something travel from one to the other in order to have an effect on each other. That is a CLASSICAL viewpoint.

The mathematical model we are using considers quantum particles as manifestations of their global QED fields.
These fields are not local to the manifested particle.
According to a 'subset' of this mathematical model, we can describe the evolution of this quantum particle with a wave equation, which, among other things will give an indication of the probability of finding this particle anywhere in the universe.
IOW, the wave equation is also global.

If we now consider two quantum particles, which we have managed to entangle, we can describe their behaviour with the same wave function.
This wave function 'contains' the correlation; the particles themselves are not in a state of flux, switching back and forth between possible states, as Bangstrom would like to believe. They are actually undefined !

Upon collapsing the wave function, both particles assume their observed states, and the correlation is evident, just as would happen for a single particle wave function.
The wave function, being a mathematical construct, collapses globally; there is no need for communication/interaction of any kind, sub-luminal or super-luminal.

Bell has proven the lack of 'hidden variables', and Einstein, of all people, would turn over in his grave at the thought of 'non-local information transfer'.

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5 hours ago, MigL said:

Bell has proven the lack of 'hidden variables', and Einstein, of all people, would turn over in his grave at the thought of 'non-local information transfer'.

This is a quote from Wiki,

“Physicists such as Alain Aspect and Paul Kwiat have performed experiments that have found violations of these inequalities up to 242 standard deviations.[20] This rules out local hidden-variable theories, but does not rule out non-local ones.”

https://en.wikipedia.org/wiki/Hidden-variable_theory

As I said earlier, ruling out “hidden variables” leaves non-locality as the default explanation. It also rules out and the determinate nature of entangled particles prior to observation. The quantum identities of entangled particles are random and indeterminate prior to their first observation. 'God roles the dice.'

Einstein et al. rejected the idea of “Spooky action at a distance” so they proposed the hypothesis of “hidden variables” to explain the apparent non-locality as a local interaction due to a "something" common to all local environments that affects the outcome of experiments in remote locations.

Now you and “joigus” appear to be saying that the absence of hidden variables rules out non-locality which is the opposite of the historical conclusion. How bizarre, how bizarre.

 

 

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You are the only one claiming that since there are no hidden variables, the only remaining choice is non-local communication/interaction.
It is NOT just one or the other.

We are saying that there is no communication/interaction, local or non-local, sub-luminal or super-luminal, real or imaginary; of any kind.

It is not just a lack of undestanding on your part, but a ( willful ? ) mischaracterization of other's positions on the matter.
And frankly, it's getting annoying.

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7 hours ago, MigL said:

 

If we now consider two quantum particles, which we have managed to entangle, we can describe their behaviour with the same wave function.
This wave function 'contains' the correlation; the particles themselves are not in a state of flux, switching back and forth between possible states, as Bangstrom would like to believe. They are actually undefined !

 

Do the particles  exist when their state is undefined?

Or do they only exist when there is an interaction?

 

I think this may have been answered earlier but if the state of one entangled particle is measured does it matter when the state of the other is measured?

 

Could it be  centuries later so long as there had been no other  interactions  in the meantime ?

 

Also you mentioned the global fields:

Would I be right to think that these global fields arose  at the earliest epochs that have been modeled and that they have been "evolving" ever since ,like some kind of  physical cosmic organisms ?

 

 

Edited by geordief
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1 hour ago, geordief said:

Do the particles  exist when their state is undefined?

Any 'state' defined by the wave function does not exist as what we would normally call 'real', before any collapse due to observation/interaction.
The 'existence' is defined as a probability distribution ( a mathematical concept; is thet 'real' ? ) prior to collapse.
Quantum mechanics is probabilistic in nature, not deterministic, like classical.
Until you wrap your head around this paradigm shift in your ( Bangstrom's ) thinking, your understanding of QM will be mired in misconceptions.

1 hour ago, geordief said:

Would I be right to think that these global fields arose  at the earliest epochs that have been modeled and that they have been "evolving" ever since ,like some kind of  physical cosmic organisms ?

Well QED/QCD posit that these fields have always existed.
( but obviously at the earliest times, there had to be some 'evolution', as combined fields split to other fields through symmetry breaks )
These fields on fields is all that exists, and particles are quantum excitations of these fields, 'real' if exceeding a threshold value, and virtual, if below that threshold.
A quantum field theory of gravity would have even space-time, the background 'stage' on which all other events take place, as a field ( currently in GR there is no background 'stage', it is already a geometric field ).
LQG attempts to do just that.


I recommend the pinned thread, "Matter is excitations in a field", in the Quantum Theory section of the Physics forum.

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6 minutes ago, MigL said:

Until you wrap your head around this paradigm shift in your ( Bangstrom's ) thinking, your understanding of QM will be mired in misconceptions

I

 

Thanks,I will take a look at that pinned thread as it does seem very much  a propos. 

 

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7 hours ago, MigL said:

The 'existence' is defined as a probability distribution ( a mathematical concept; is thet 'real' ? ) prior to collapse.
Quantum mechanics is probabilistic in nature, not deterministic, like classical.
Until you wrap your head around this paradigm shift in your ( Bangstrom's ) thinking, your understanding of QM will be mired in misconceptions.

This is absolutely not my understanding. I agree that QM is probabilistic and I have never claimed otherwise. ‘God roles the dice’.

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15 hours ago, bangstrom said:

Now you and “joigus” appear to be saying that the absence of hidden variables rules out non-locality which is the opposite of the historical conclusion. How bizarre, how bizarre.

 

Again, no. Nobody has definitely proved that non-locality is ruled out. If you had read what I posted before, you wouldn't be implying that I said what I didn't. In order to help you better understand the difference between what I "appear to be saying" and what I actually said:

On 9/19/2022 at 8:40 AM, joigus said:

Even people who are still thinking about teleportation --no experimental evidence, just exploring logical loopholes--, admit that quantum mechanics would have to be superseded with something else, if superluminal signals were to be accepted as a possibility:

https://plato.stanford.edu/entries/qm-action-distance/#NecSufConForSupSig

Quote

It is commonly agreed that in quantum phenomena, superluminal signaling is impossible in practice. Moreover, many believe that such signaling is excluded in principle by the so-called ‘no-signaling theorem’ (for proofs of this theorem, see Eberhard 1978, Ghirardi, Rimini and Weber 1980, Jordan 1983, Shimony 1984, Redhead 1987, pp. 113-116 and 118). It is thus frequently claimed with respect to EPR/B experiments that there is no such thing as a Bell telephone, namely a telephone that could exploit the violation of the Bell inequalities for superluminal signaling of information.[31]

The no-signaling theorem demonstrates that orthodox quantum mechanics excludes any possibility of superluminal signaling in the EPR/B experiment. According to this theory, no controllable physical factor in the L-wing, such as the setting of the L-measurement apparatus, can take advantage of the entanglement between the systems in the L- and the R-wing to influence the statistics of the measurement outcomes (or any other observable) in the R-wing. As we have seen in section 5.1.1, the orthodox theory is at best incomplete. Thus, the fact that it excludes superluminal signaling does not imply that other quantum theories or interpretations of the orthodox theory also exclude such signaling. Yet, if the orthodox theory is empirically adequate, as the consensus has it, its statistical predictions obtain, and accordingly superluminal signaling will be excluded as a matter of fact; for if this theory is empirically adequate, any quantum theory will have to reproduce its statistics, including the exclusion of any actual superluminal signaling.

But the no-signaling theorem does not demonstrate that superluminal signaling would be impossible if orthodox quantum mechanics were not empirically adequate. Furthermore, this theorem does not show that superluminal signaling is in principle impossible in the quantum realm as depicted by other theories, which actually reproduce the statistics of orthodox quantum mechanics but do not prohibit in theory the violation of this statistics. In sections 7.2-7.3, we shall consider the in-principle possibility of superluminal signaling in certain collapse and no-collapse interpretations of quantum mechanics. But, first, we need to consider the necessary and sufficient conditions for superluminal signaling.

Expand  

(My emphasis in boldface characters.)

It may well be the case that some day somebody comes up with a model that is non-local, and produces the quantum correlations, which give no clue of non-locality anywhere, because they are correlations built into the quantum state when it was prepared at, say, t=0, (x,y,z)=(0,0,0).

Of course, this person would be under the automatic obligation to explain why it is that no trace of this non-locality can be found in the real world.

Why would someone pursue something so incredibly silly? I don't know. You tell me.

A non-local field or particle theory of any kind would be very difficult to reconcile with relativistic causality. It would be miraculous that no non-local (and therefore relativistically non-causal) effect can be exploited, while all the while, the inner workings of the fields were non-local.

What the famous impossibility theorems tell you is:

If, for some reason, you wanted to assume that the eigenvalues (observed values) have been a function of some definite variables all the time, you would have to give up locality, or very deep principles of statistics (positivity of probabilities), or perhaps both.

What Aspect et al. proved is not that there are no hidden variables. How can you prove the non-existence of something you have no idea what it could be?

What Aspect et al. proved is that quantum mechanical probabilities give exactly what quantum mechanics --in its close mathematical form for angular momentum-- predicts. Even for the crucial case that Bell et al. proposed.

Because they were confirmed, and John Bell proved that quantum mechanics involves something other than classical logic, we believe quantum mechanics is correct (about angular momentum, anyway) and non-locality was never necessary in the first place.

Is that better?

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I will have to read this conversation at least a dozen more times to comprehend it further, however I always thought that 1) decoherence was globally instantaneous  2) no usable information could be forwarded through this mecanism 3) there is no hidden variables.

I'am struggling to sort that out because I quite not understand decoherence any more. Is it instantaneous or not ?

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50 minutes ago, Mitcher said:

I always thought that 1) decoherence was globally instantaneous 

This is, I think, a brilliant question. We've touched it laterally, but because there was disagreement on more basic aspects, I for one have dispatched it too quickly perhaps.

I'm aware that some people --who are not completely off their rocker-- say that. But,

Decoherence can only be ascertained only after a large-enough number of identically-prepared experiments is performed --ideally, infinitely many experiments. The state to account for is no longer a pure state, but a strict mixture. It cannot, and should not, be considered as representing one run of the experiment, but infinitely many runs of the experiment.

What does it even mean that decoherence is globally instantaneous in that case?

Mind you: Decoherence tells you that the different components of the wave function are no longer in phase --think about the double-slit experiment. How do you measure that with just one instance? How do you know there is no longer interference by shooting just one electron?

1 hour ago, Mitcher said:

2) no usable information could be forwarded through this mecanism

You can rest assured that's the case, otherwise relativistic causality would be violated.

1 hour ago, Mitcher said:

3) there is no hidden variables.

That's certainly the case for spin, for the very simple reason that experiments and mathematical theorems cannot deceive us. I don't think it's necessarily the case for position variables.

Caveats:

Keep in mind that the previous ones are my answers. As to the 1st one, it's possible that the view is not unanimous, but I think the argument I gave you is solid enough.

As to the second, I don't think anybody who's really a serious physicist would disagree with it.

The 3rd one is my opinion on the part that concerns position variables, but it's an opinion I can defend and I'm willing to discuss it with anybody who's interested.

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On 9/19/2022 at 11:21 AM, MigL said:

Bell has proven the lack of 'hidden variables', and Einstein, of all people, would turn over in his grave at the thought of 'non-local information transfer'.

From your statements, such as the one above, the implication appears to be that the lack of ‘hidden variables’ implies locality. Einstein et al. suggested the hypothesis of ‘hidden variables’ as an alternative explanation to his anathema of non-locality.

What significance do you find to the lack of ‘hidden variables’ if the conclusion is ‘locality’ either way. Or, is that not the way it works?

On 9/19/2022 at 11:21 AM, MigL said:

The mathematical model we are using considers quantum particles as manifestations of their global QED fields.
These fields are not local to the manifested particle.
According to a 'subset' of this mathematical model, we can describe the evolution of this quantum particle with a wave equation, which, among other things will give an indication of the probability of finding this particle anywhere in the universe.
IOW, the wave equation is also global.

This appears to a description of non-locality. How can the wavelike connection and transaction between entangled particles be something other than non-local if the timing of events is far less than space like (super-luminal).

 

On 9/19/2022 at 11:21 AM, MigL said:

 

On 9/19/2022 at 11:21 AM, MigL said:

Upon collapsing the wave function, both particles assume their observed states, and the correlation is evident, just as would happen for a single particle wave function.
The wave function, being a mathematical construct, collapses globally; there is no need for communication/interaction of any kind, sub-luminal or super-luminal

The interaction among entangled particles is a part of our material world and not just a wave function on paper. When the wave-like connection between entangled particles is lost the quantum identities of the particles involved become determinate at both ends of the connection simultaneously. There is no time interval between the events on both ends which is why I call the event non-local. Or, global if you will.

 

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On 9/20/2022 at 2:17 AM, MigL said:

 


I recommend the pinned thread, "Matter is excitations in a field", in the Quantum Theory section of the Physics forum.

Yes ,a great  entertaining lecture from Sean Carrol and most of it very new to me (some of it just providing "internal" context.

 

Amusing how he presents QFT as some kind of an ugly  duckling  of physics.It is indeed the last part of that  general area that I realized I should (could) look at.

 

"All the world's a Field"  could be a catchy tune

 I will have to play it a good few times more  now when I get the time

Edited by geordief
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It appears, Bangstrom, that you still think quantum particles have an observable state, before they are actually observed.
And that they need to communicate this state to their entangled partner.
They don't.
And they don't.

Our model says they are, at best, a probability distribution.
If you want to 'imagine' a different  underlying 'reality', you need to come up with a different model.

Edited by MigL
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0) Quantum mechanics (a totally local theory) predicts quantum correlations for spin

1) If some hidden variables explained quantum correlations for spin => they would contradict quantum mechanics (Bell)

2) quantum mechanical correlations for spin are experimentally confirmed (Aspect) => QM is correct even for these subtle cases.

Good! Let's go home --quoting M. Gell-Mann.

But no. Wait a minute. What if...? Here's where things get complicated. People go back to Bell's paper and notice he mentions something about non-locality. Bell was very ambivalent about this point for a while. Sometimes he thought his inequalities implied some kind of non-locality, and in a matter of weeks or months, he changed his mind about it, agreeing with Feynman that they only reflected the peculiar nature of quantum probabilities: Some propositions, that from a classical POV make perfect sense as independent propositions, do not behave like that at all in quantum mechanics. In QM you can have propositions that are either true, false, or neither true nor false (quantum superpositions.)

Bell finally sets the record straight and publishes his famous paper on Bertlemann's socks and the nature of reality. => You don't need any magical action at a distance to explain correlations based on a conservation principle. It happens classically all the time!

End of story.

Or is it? The jury is still out, only because they didn't, or wouldn't, hear the call to go back home.

People keep going back to those papers looking for a magical action at a distance for which there was no need at all in the first place. Why? Because:

Quantum mechanics (a totally local theory) predicts quantum correlations for spin

 

 

Edited by joigus
minor correction
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7 hours ago, bangstrom said:

How can the wavelike connection and transaction between entangled particles be something other than non-local if the timing of events is far less than space like (super-luminal).

There is no “transaction” or “connection” other than when the entanglement occurs.

I prefer the analogy of a coin flip or toss of a standard six-sided die vs the gloves, because while it is tumbling, the state is undetermined. But when it stops and you observe the side facing you, you instantly know what’s on the opposite side. The coin or die does not need to communicate any information, because that was encoded once the object was made.

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50 minutes ago, swansont said:

There is no “transaction” or “connection” other than when the entanglement occurs.

I prefer the analogy of a coin flip or toss of a standard six-sided die vs the gloves, because while it is tumbling, the state is undetermined. But when it stops and you observe the side facing you, you instantly know what’s on the opposite side. The coin or die does not need to communicate any information, because that was encoded once the object was made.

 Can it be said the the two subsequent objects were one (dynamic) object at the entaglement?

Edited by geordief
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1 hour ago, geordief said:

 Can it be said the the two subsequent objects were one (dynamic) object at the entaglement?

It’s QM, so “object” isn’t a description one would use. The system is described by a wave function that can’t be separated into two individual wave functions.

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45 minutes ago, swansont said:

It’s QM, so “object” isn’t a description one would use. The system is described by a wave function that can’t be separated into two individual wave functions.

Can   all systems be described by one wave function(as I think I may have heard)?

Can systems generally also be separated into separate wave functions so that the inseperability  you are talking of is really just specific to entangled particles?

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3 hours ago, swansont said:

I prefer the analogy of a coin flip or toss of a standard six-sided die vs the gloves, because while it is tumbling, the state is undetermined. But when it stops and you observe the side facing you, you instantly know what’s on the opposite side. The coin or die does not need to communicate any information, because that was encoded once the object was made.

This example illustrates very nicely an analogue for quantum superpositions, but as any other classical analogue of quantum systems, it only illustrates one particular aspect of them. But I'm sure you agree that no classical analogy can actually embody all the properties of a multipartite quantum system, or of any other quantum system for that matter.

The coin illustrates very well the indefinite nature of the intermediate states, but misses the correlations, and the fact that the state can be brought apart in the spatial components. The gloves cannot reproduce the total indefinition that characterises the state before a measurement is performed.

So we're at a loss for analogies really.

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