How many interpretations of QM do you speak?

[Sambuco]

It is interesting that the first time we realized we don't live in a Kolmogorovian universe was 24 years before Kolmogorov formulated his axioms.

Nothing that can't be fixed with a pinch of retrocausality

Lucas.

 

[WernerQH]

Why is the electron forced to reappear with such frequency? Is it due to $\frac{\hbar}{mc^2} \sim 10^{-21} \text{ s}$?

Yes. In his book "The Road to Reality" Penrose offers a similar picture: a zig-zag-line. The velocity operator has eigenvalues $\pm c$. For an electron "at rest" the average speed is zero, but because spin is conserved its helicity is constantly flipping from right-handed to left-handed and vice versa. Was once known as "Zitterbewegung".

 

[A. Neumaier]

for practical purposes, "shut up and calculate" has proven extremely useful.

...because after calculation, every user (as long as shutting up = not using the word 'interpretation' ) is allowed to interpret the results as fits the context, unconstrained by the formal (and often too rigid) demands of an interpretation.

 

[Demystifier]

A particle is an irreducible representation of the Poincaré group
https://en.wikipedia.org/wiki/Particle_physics_and_representation_theory

No, a particle is a click in a particle detector.
Now seriously, the word "particle" has many different meanings in physics, so picking one of them and claiming that only this meaning is the "right" one is, well, rather narrow minded.

 

[javisot]

I still think that "shut up and calculate", following the language analogy, is more akin to communicating through noises and gestures than to English.

 

[martinbn]

I still think that "shut up and calculate", following the language analogy, is more akin to communicating through noises and gestures than to English.

I'd say it is just plain language without any similies, methaphors and other figures of speech. Say the way Dirac spoke English compare to the way a poet uses English.

 

[Lord Jestocost]

No, a particle is a click in a particle detector.
Now seriously, the word "particle" has many different meanings in physics, so picking one of them and claiming that only this meaning is the "right" one is, well, rather narrow minded.

In addition!

In their article “The concept of the photon - revisited”, Ashok Muthukishnan, Marlan O. Scully and M. Suhail Zubairy remark:

'In the final portions of the article, we return to the basic questions concerning the nature of light in the context of the wave-particle debate: What is a photon and where is it? To the first question, we answer in the words of Roy Glauber:

"A photon is what a photodetector detects."

To the second question (on the locality of the photon), the answer becomes: “A photon is where the photodetector detects it.”'

(in the book "The Nature of Light: What is a Photon?", edited by Chandra Roychoudhuri, A.F. Kracklauer, Kathy Creath, CRC Press)

 

[Demystifier]

Kolmogorov's axioms of probability are perfectly compatible with QM. In fact, I am not aware of any coherent interpretation of QM based on non-Kolmogorovian probability.

 

[Sambuco]

Kolmogorov's axioms of probability are perfectly compatible with QM. In fact, I am not aware of any coherent interpretation of QM based on non-Kolmogorovian probability.

Of course it is compatible. What the paper I shared aims to show is that if one accepts certain preconceptions from classical theories as true, it implies that the event space is broad enough to render Kolmogorov's axioms incompatible with quantum mechanics. Ultimately, it is a somewhat different way of analyzing issues such as the theory's contextuality.

Lucas.

 

[Morbert]

Kolmogorov's axioms of probability are perfectly compatible with QM. In fact, I am not aware of any coherent interpretation of QM based on non-Kolmogorovian probability.

The closest I could find https://arxiv.org/abs/quant-ph/0510095

[edit] - PS Jurg Froehlich gives a related view of quantum theory through the lens of probability https://arxiv.org/abs/1310.1484

PPS This is not to say that ordinary Kolmogorovian probability is incompatible with QM. It just exists in a larger non-Kolmogorovian context.

 

[RUTA]

I know, but I asked you because I have the impression that many of those reconstructions start from an operationalist perspective, e.g. Höhn starts assuming a kind of relational interpretation.

Yes, they start from an operationalist perspective exactly like Einstein did with his 1905 SR paper. Wiltsche, McDevitt and I are working to justify that by basing all of physics in phenomenology directly.

Yes, I’ve read the paper and that section in particular. I got the impression that your approach is similar to Grangier’s Contexts-Systems-Modalities.

Yes, in that same paper we wrote: [Grangier et al., 2024] reach a similar conclusion, “based on a century of theoretical and experimental progress, our conclusion is that classical physics and quantum physics can neither function nor even be conceived one without the other."

1. You equate "Locality" with "Local Agency," but they are not the same thing. Locality is the same assumption employed by Bell in his original 1964 formulation of Bell's theorem, it is Shimony's "parameter independence". Instead, Local agency is Locality + No-superdeterminism.
2. You state that the three assumptions are true, but the "local friendliness" (LF) no-go theorem demonstrates that QM is incompatible with the conjunction of those three assumptions. That's why I asked you about how your approach deals with LF no-go theorem.

I grabbed those from Google AI, but I should have simply referred you to: “The Completeness of Quantum Mechanics and the Determinateness and Consistency of Intersubjective Experience: Wigner’s Friend and Delayed Choice,” Michael Silberstein and W.M. Stuckey. In Consciousness and Quantum Mechanics, edited by Shan Gao (Oxford University Press, 2022) 198-259 http://arxiv.org/abs/1901.10825 for a complete answer. Here is an executive summary.

Start with these two excerpts from the paper:

and:

Next, locality and statistical independence (no superdeterminism) were assumptions for Bell. We do not violate these assumptions because they only apply to causal explanations. Remember, Bell wanted to find out if additional variables could be added to QM "to restore to the theory causality and locality."

According to our completion of the quantum reconstruction program, QM is as complete as possible and is a principle theory (formalism derived from an empirically discovered fact, i.e., observer-independence of h exactly like observer-independence of c for SR) that provides principle explanation (fundamental explanans is the principle that justifies the empirically discovered fact, i.e., relativity principle justifies observer-independence of h exactly like it justifies observer-independence of c for SR). For example, entanglement per the Mermin device is a conundrum ("A confusing and intricate problem" with no consensus solution) if you demand a causal account, but it is reduced to a paradox ("An assertion or condition that opposes common sense or logic yet turns out to be valid") when resolved in principle fashion. See my recent talk at Wright State University:



That's why we don't violate any of the assumptions in LF.

 

[.Scott]

I'd say it is just plain language without any similies, methaphors and other figures of speech. Say the way Dirac spoke English compare to the way a poet uses English.

I still think that "shut up and calculate", following the language analogy, is more akin to communicating through noises and gestures than to English.

That phrase ("shut up and calculate") is credited to Cornell's N. David Mermin (aged 91 and still calculating).
If you wish to understand what he meant by the phrase, he has already obliged us with the Physics Today article titled "Could Feynman Have Said This?"

I won't attempt to summarize the article, because a summary would provide a very lame explanation of the phrase's original meaning and origin. Besides, that article is short and largely quick and easy to read in whole.

But here is an interesting excerpt:

Although I didn’t say so in my old Reference-Frame article, what inspired this not so terribly bon mot were vivid memories of the responses my conceptual inquiries elicited from my professors—whom I viewed as agents of Copenhagen—when I was first learning quantum mechanics as a graduate student at Harvard, a mere 30 years after the birth of the subject. “You’ll never get a PhD if you allow yourself to be distracted by such frivolities,” they kept advising me, “so get back to serious business and produce some results.” “Shut up,” in other words, “and calculate.” And so I did, and probably turned out much the better for it. At Harvard, they knew how to administer tough love in those olden days.

 

[Matterwave]

@Sambuco I have not read the paper, just the abstract and some set up, but I did have some preliminary thoughts.

Of course it is compatible. What the paper I shared aims to show is that if one accepts certain preconceptions from classical theories as true, it implies that the event space is broad enough to render Kolmogorov's axioms incompatible with quantum mechanics.

From what I understand, the paper is saying that applying Kolmogorov axioms (and specifically the law of total probability, which is a consequence of the axioms) to the statistics of observables does not work.

The crux of the problem, though, it seems to me, is in defining how to apply Kolmogorov axioms of probability to QM situations and we have various no-go theorems saying how we can't do it. This "how" question informs the kinds of interpretations that make sense and are consistent with the QM formalism.

In other words, my feeling is that given how central the Kolmogorov axioms are to our understanding of probability, figuring out how to apply them is likely the more fruitful approach than saying something like:

...quantum matter can not be described by a Kolmogorovian probabilistic theory.

(What is quantum matter btw? Does it taste different than ordinary matter?)

Ultimately, it is a somewhat different way of analyzing issues such as the theory's contextuality.

Is it really different though? Or at least, different in a more elucidating way?

 

[javisot]

That phrase ("shut up and calculate") is credited to Cornell's N. David Mermin (aged 91 and still calculating).
If you wish to understand what he meant by the phrase, he has already obliged us with the Physics Today article titled "Could Feynman Have Said This?"

I won't attempt to summarize the article, because a summary would provide a very lame explanation of the phrase's original meaning and origin. Besides, that article is short and largely quick and easy to read in whole.

But here is an interesting excerpt:

Although I didn’t say so in my old Reference-Frame article, what inspired this not so terribly bon mot were vivid memories of the responses my conceptual inquiries elicited from my professors—whom I viewed as agents of Copenhagen—when I was first learning quantum mechanics as a graduate student at Harvard, a mere 30 years after the birth of the subject. “You’ll never get a PhD if you allow yourself to be distracted by such frivolities,” they kept advising me, “so get back to serious business and produce some results.” “Shut up,” in other words, “and calculate.” And so I did, and probably turned out much the better for it. At Harvard, they knew how to administer tough love in those olden days.

Agreed, and thanks for sharing the information. But you will have noticed that, over the course of this conversation, it doesn't matter who said "Shut up and calculate" or what they meant by it. We are using "Shut up and calculate" to refer to "the formalism", "the textbook", QM without interpretation, orthodox QM, etc. (various names are used)

 

[bhobba]

Now seriously, the word "particle" has many different meanings in physics, so picking one of them and claiming that only this meaning is the "right" one is, well, rather narrow minded.

My bad for implying that's the only possible definition.

Thanks
Bill

 

[gentzen]

We are using "Shut up and calculate" to refer to "the formalism", "the textbook", QM without interpretation, orthodox QM, etc. (various names are used)

No, we don‘t! Maybe „the formalism“, but all the other things you mentioned are unrelated.

 

[.Scott]

Agreed, and thanks for sharing the information. But you will have noticed that, over the course of this conversation, it doesn't matter who said "Shut up and calculate" or what they meant by it. We are using "Shut up and calculate" to refer to "the formalism", "the textbook", QM without interpretation, orthodox QM, etc. (various names are used)

Indeed I did - and it is well worth spending a moment to notice how our language is used at the "masters" level. So, in this case we have "Shut up and calculate" where the presumed author himself does not have a clear recollection of his full thoughts when he coined the phrase - but who can reconstruct, based on knowing his own personal history where it likely came from. Then we have an audience who picked it up and carried it to a different place - many thinking that it was likely a Feynman quote. And finally we have this thread where the phrase was resurrected for our more specific purposes. And what is key is that no one is "misusing" the phrase.

At the center of this is "ambiguity" - one phrase meaning several things and you get to pick. It's like a Swiss Army knife: What do you want it to be?

In that light, I give you Robert Frost's, "The Road Not Taken":

Two roads diverged in a yellow wood, And sorry I could not travel both And be one traveler, long I stood And looked down one as far as I could To where it bent in the undergrowth; Then took the other, as just as fair, And having perhaps the better claim, Because it was grassy and wanted wear; Though as for that the passing there Had worn them really about the same, And both that morning equally lay In leaves no step had trodden black. Oh, I kept the first for another day! Yet knowing how way leads on to way, I doubted if I should ever come back. I shall be telling this with a sigh Somewhere ages and ages hence: Two roads diverged in a wood, and I— I took the one less traveled by, And that has made all the difference.

This is a very well-known poem and poet. Frost died in 1963. I first heard this poem in grade school - and now I live about 12 miles from the poet's farm.
If you want to know what was on Robert's mind when he wrote it, it is explained in this link.
But clearly Mr. Frost knew from the start that his largest audience would take this "philosophically" and that was fully part of his intention.

 

[javisot]

No, we don‘t! Maybe „the formalism“, but all the other things you mentioned are unrelated.

Could you explain why you don't see those concepts as related in this discussion?

Are you saying that no one used "shut up and calculate" to mean "QM without interpretation"?, or was it that no one who mentioned a "QM textbook" was referring to books on the formalism of QM?

 

[Sambuco]

From what I understand, the paper is saying that applying Kolmogorov axioms (and specifically the law of total probability, which is a consequence of the axioms) to the statistics of observables does not work.

Yes, in a sense, the aim of the work is to find a common (interpretation-independent) way to define the measurement problem based on a intuitive/näive/classical notion of probability, starting from the premise that QM is a theory providing probabilities for the occurrence of specific events. Looking at the relation between the probabilities of different events, it is revealed that QM violates the law of total probability. According to the author, this suggests that the assumption of epistemic uncertainty might lie at the root of the problem. Consequently, the distinction between what exists and what we know becomes blurred in QM.

The crux of the problem, though, it seems to me, is in defining how to apply Kolmogorov axioms of probability to QM situations and we have various no-go theorems saying how we can't do it. This "how" question informs the kinds of interpretations that make sense and are consistent with the QM formalism.

Exactly!

In other words, my feeling is that given how central the Kolmogorov axioms are to our understanding of probability, figuring out how to apply them is likely the more fruitful approach than saying something like:
(What is quantum matter btw? Does it taste different than ordinary matter?)

I think the author uses "quantum matter" to refer to that somewhat näive notion of objects possessing observation-independent well-defined properties at every time.

Is it really different though? Or at least, different in a more elucidating way?

If they aren't the same thing, they are too closely related. In my opinion, the author is motivated to seek a more fundamental/direct definition of the measurement problem that avoids traditional approaches, which deals with the unitary/non-unitary wave function evolution, because such approaches place undue importance on a mathematical object whose role in the theory's interpretation is unclear. He is trying to build a narrative more like: "Well, okay, QM gives us probabilities, but probabilities of what? (classical) objects moving around? Well, it's not that simple, because the probabilities start to relate to one another in somewhat strange ways, so what do we do with it?"

Lucas.

 

[Sambuco]

I grabbed those from Google AI, but I should have simply referred you to: “The Completeness of Quantum Mechanics and the Determinateness and Consistency of Intersubjective Experience: Wigner’s Friend and Delayed Choice,” Michael Silberstein and W.M. Stuckey. In Consciousness and Quantum Mechanics, edited by Shan Gao (Oxford University Press, 2022) 198-259 http://arxiv.org/abs/1901.10825 for a complete answer.

Thanks again @RUTA for your reply!

I read the paper, but I still can't fully grasp how your approach overcome the local friendliness (LF) no-go theorem. In your paper, you rightly point out that the theorem is based on four assumptions: absoluteness of observed events (AOE), locality (L), non superdeterminism (NSD), and what you call "the completeness of QM", which is usually also referred to as universality. Then, you state that the latter assumption holds, placing us in the conditions under which the theorem demonstrates an inconsistency between AOE, L, and NSD. Later, you said:

Next, locality and statistical independence (no superdeterminism) were assumptions for Bell. We do not violate these assumptions because they only apply to causal explanations.

Well, the only remaining hypothesis is AOE, and one would think that would be, then, the assumption your approach/interpretation would violate. But in the paper you said:

"Assumption 1 is the Absoluteness of Observed Events (AOE)): An observed event is a real single event, and not relative to anything or anyone." As they point out, this is a tacit assumption made in deriving Bell inequalities, e.g., the CHSH inequality. And as we showed above, this assumption is necessary for using the formalism of QM, i.e., if one violates this assumption when using the formalism of QM, contradictions and absurdities can arise. So, while it may certainly be true that violating Assumption 1 leads to the violation of their LF inequality, one cannot use QM to check their LF inequality while violating Assumption 1."

I understand that the paper states that AOE also holds. However, in that case, there is an inconsistency between your approach/interpretation and QM, given that the latter violates the LF inequalities. I get the impression that what you are saying is that one can avoid "falling" into the LF no-go theorem by not asking for a causal explanation, but that there in no notion of causality in the assumptions of the theorem. In fact, the theorem deals only with correlations between measurements made by "super-observers."

Lucas.

 

[RUTA]

Thanks again @RUTA for your reply!

You're welcome :-)

I read the paper, but I still can't fully grasp how your approach overcome the local friendliness (LF) no-go theorem. In your paper, you rightly point out that the theorem is based on four assumptions: absoluteness of observed events (AOE), locality (L), non superdeterminism (NSD), and what you call "the completeness of QM", which is usually also referred to as universality. Then, you state that the latter assumption holds, placing us in the conditions under which the theorem demonstrates an inconsistency between AOE, L, and NSD. Later, you said:

Well, the only remaining hypothesis is AOE, and one would think that would be, then, the assumption your approach/interpretation would violate. But in the paper you said:

"Assumption 1 is the Absoluteness of Observed Events (AOE)): An observed event is a real single event, and not relative to anything or anyone." As they point out, this is a tacit assumption made in deriving Bell inequalities, e.g., the CHSH inequality. And as we showed above, this assumption is necessary for using the formalism of QM, i.e., if one violates this assumption when using the formalism of QM, contradictions and absurdities can arise. So, while it may certainly be true that violating Assumption 1 leads to the violation of their LF inequality, one cannot use QM to check their LF inequality while violating Assumption 1."

I understand that the paper states that AOE also holds. However, in that case, there is an inconsistency between your approach/interpretation and QM, given that the latter violates the LF inequalities. I get the impression that what you are saying is that one can avoid "falling" into the LF no-go theorem by not asking for a causal explanation, but that there in no notion of causality in the assumptions of the theorem. In fact, the theorem deals only with correlations between measurements made by "super-observers."

Lucas.

As we point out in the paper, LF doesn't get you anything new beyond Bell. We state for example:

NSD is statistical independence and L is locality exactly per Bell, so QM violating the LF inequality is the same as QM violating Bell's inequality. Both NSD and L involve hidden variables "to restore to the theory causality and locality" per Bell, so there is another assumption not listed so far, i.e., causality. That is the assumption we violate.