Is Relational Quantum Mechanics the Key to Understanding Quantum Interactions?

[EPR]

Big objects have vanishingly small interference traces due to scale and average probabilities. My guess is we have to go small, lower than 1mm to have a noticeable pattern. Classicality is a law of this reality. If it was possible or easy to avoid it, billions of people before us would have noticed it and the quantum nature of the Universe would have been known earlier.

 

[Marek Domanski]

Big objects have vanishingly small interference traces due to scale and average probabilities. My guess is we have to go small, lower than 1mm to have a noticeable pattern. Classicality is a law of this reality. If it was possible or easy to avoid it, billions of people before us would have noticed it and the quantum nature of the Universe would have been known earlier.

That is roughly what I thought, but Rovelli in his popular books is very confusing. I am waiting for a negative review.
You could of course have quantum effects have a real purely objective probabalistic effect on the world by putting the likes of Donald Trump in Schrodinger's box instead of a cat.

 

[AlexCaledin]

...quantum systems... really only exist as they relate to another system. The interaction between systems is the “real” entity.

- do we then come to the Process Philosophy as opposed to the Substance metaphysics?

https://plato.stanford.edu/entries/process-philosophy/

Indeed, then the fundamental entities are psychophysical events as interactions between the psychical and physical side of reality.

 

[PeterDonis]

do we then come to the Process Philosophy as opposed to the Substance metaphysics?

Philosophy is off topic in this forum. Please keep discussion focused on RQM considered as a QM interpretation.

 

[Sunil]

Please let us know why you are not a fan of RQM.

Such relativization is cheap and gives nothing new. Whenever you have some reasonable realistic interpretation, you can relativize it without having to add something new at all. All you have to do is to relativize all the absolute things. So all what is reached is that we have, after relativization, less valuable information than before.

 

[Demystifier]

Philosophy is off topic in this forum. Please keep discussion focused on RQM considered as a QM interpretation.

Where exactly is the borderline between interpretations of QM and philosophy of QM? And it's not just a rhetorical question (even though partly it is). Even though there is obviously no sharp borderline, it would be great to have at least some vague guide that can help to distinguish the two.

 

[Demystifier]

Today appeared a paper that claims to make no-go theorems against the relational interpretation. I haven't read it yet, but it could be interesting. https://arxiv.org/abs/2107.00670

 

[martinbn]

Such relativization is cheap and gives nothing new. Whenever you have some reasonable realistic interpretation, you can relativize it without having to add something new at all. All you have to do is to relativize all the absolute things. So all what is reached is that we have, after relativization, less valuable information than before.

If you change relativization with interpretation the same thing can be siad about any interpretation.

 

[PeterDonis]

Where exactly is the borderline between interpretations of QM and philosophy of QM?

The post I responded to isn't even about "philosophy of QM". It's just philosophy, period--not even specific to QM.

 

[*now*]

Today appeared a paper that claims to make no-go theorems against the relational interpretation. I haven't read it yet, but it could be interesting. https://arxiv.org/abs/2107.00670

?
Is there anything aside from the abstract?
I get, “Our automated source to PDF conversion system has failed to produce PDF for the paper: 2107.00670.”

 

[Demystifier]

?
Is there anything aside from the abstract?
I get, “Our automated source to PDF conversion system has failed to produce PDF for the paper: 2107.00670.”

PDF format does not work, but POSTCRIPT (.ps) format does. So click postscript! If on your computer you don't have a tool for reading postscript files and you don't want to install one, you can convert ps file to pdf file, e.g. here https://online2pdf.com/convert-ps-to-pdf .

 

[AlexCaledin]

... It's just philosophy, period--not even specific to QM.

- well, of course, it's just that the very fact of the Process philosophy being a valid philosophical variant seems reconciling all the QM interpretations as useful thinking tools, the Copenhagen pragmatic interpretation being the most useful one. (edit: because the quest for substance becomes unscientific)

 

[*now*]

PDF format does not work, but POSTCRIPT (.ps) format does. So click postscript! If on your computer you don't have a tool for reading postscript files and you don't want to install one, you can convert ps file to pdf file, e.g. here https://online2pdf.com/convert-ps-to-pdf .

thanks, I think that article is unhelpful and admits their argument does not agree with RQM primary literature and acknowledges succumbing to the temptation of entertaining such position anyway. The article, however, does refer to a recent paper that does seem helpful for a thread about RQM criticism. This recent paper referred to addresses a different article’s invalid criticism, suggesting improvement-

“As mentioned in the introduction, every interpretation of QM includes conceptual steps hard to digest. The exercise of criticising the details of an interpretation without accepting these conceptual steps is futile. I am sure we can do better, in articulating a fruitful conversation between different ways of making sense of quantum theory”. This quote is from the conclusion of that paper-

[2106.03205] A response to the Mucino-Okon-Sudarsky's Assessment of Relational Quantum Mechanics (arxiv.org)

A response to the Muciño-Okon-Sudarsky’s Assessment of Relational Quantum mechanics Carlo Rovelli (Dated: June 8, 2021)

 

[Fra]

Rovellis writes in that paper

"Even if The problem of quantum physics is not that we have no way of making sense of it. The problem is that we have many ways of making sense of it. But each of these comes with a high conceptual price. Each interpretation of quantum mechanics demand us to accept conceptual steps that for many are hard to digest"
-- https://arxiv.org/pdf/2106.03205.pdf

This is true I think, and it's the reason why i am not overly interested in "pure interpretations". Instead, if a research program "implied by one interpretation" is able to come up with new progress on open problems, then there is something to discuss. But even until we get there it's interesting to learn how other reason about the matter but not more than that.

I am also aware of the "hard to digest" points, on my own interpretation as well. I always felt that each interpretation pushes the trouble into different corners, which reveals how you think you are best equipped to finding a solution and what starting points you find minimally disturbing.

There first reason I originally started to look into Rovelli, was that. As he has many original ideas on gravity (LQG) I assumed that his interpretation of QM ought to be designed for progress in that direction.

/Fredrik

 

[EPR]

Rovellis writes in that paper

"Even if The problem of quantum physics is not that we have no way of making sense of it. The problem is that we have many ways of making sense of it. But each of these comes with a high conceptual price. Each interpretation of quantum mechanics demand us to accept conceptual steps that for many are hard to digest"
-- https://arxiv.org/pdf/2106.03205.pdf
/Fredrik

Rovelli is right, but only if one insists that the reality must be a Newtonian world. It appears to be a deeply rooted assumption that is just barely true in a very specific case. It's true, but is not the fundamental truth. Nor is it how the world works in its entirety.
There's big potential to answer some age old questions about how the world works. And maybe how we function. The parting with the Newtonian paradigm will not be painless and obviously not to everyone's taste but it's not up to us to decide what is true and what isn't. Is it? Nature doesn't care either way about what Rovelli thinks is a high conceptual price.

 

[Fra]

Rovelli is right, but only if one insists that the reality must be a Newtonian world.

I don't follow. What does the diversity of interpretations has todo with Newtona world?

It appears to be a deeply rooted assumption that is just barely true in a very specific case. It's true, but is not the fundamental truth. Nor is it how the world works in its entirety.
There's big potential to answer some age old questions about how the world works. And maybe how we function. The parting with the Newtonian paradigm will not be painless and obviously not to everyone's taste but it's not up to us to decide what is true and what isn't. Is it? Nature doesn't care either way about what Rovelli thinks is a high conceptual price.

Do you by newtomian paradigm here mean the same aa smolin as he argues for evolution of laws?

I think newtomian paradigm needs tp go out, but the alternative is not exactly smooth either. Law without metalaw? That is hard to digest for many.

/Fredrik

 

[EPR]

I meant there will necessarily be a conceptual price to pay, if one insists the reality is Newtonian. If one were to address the interpretational issue with this preconceived notion in mind.

As for the law without a metalaw - I think emergence is key here. Different organizational structures acting according to laws of particular scales. There are obviously laws and they do not necessarily amount to or refer to laws of lower scales. It could be that the fundamental laws are inaccessible and incomprehensible.

 

[EPR]

It is not even a scientific question what exists between measurements, as all our evidence comes from measurements and observations. We make necessary inferences and build models like we always do and sometimes they fail. Like the current Newtonian model.
When the model fails, we get better opportunities to learn new things about the reality.

 

[Fra]

I meant there will necessarily be a conceptual price to pay, if one insists the reality is Newtonian. If one were to address the interpretational issue with this preconceived notion in mind.

I think we arent talking about the same thing?

I do not insist on Newtonian reality, but I still see the headache.

My point was rather that, for example abandoning the Newtonian paradigm (ie. smolins definition) does causes trouble, because there are no meta laws, all there likely is, is principles or organisation or evolution, that are more fundamental than the laws of physics. Sticking to Newtonian paradigm seems easier, but instead leaves us with a unreasonable fine tuning problem, that may not even have a final solution in the first place if the paradigm is wrong.

Im not saying there is no solution to either way, I just say that with our without Newtonian paradigm we have things to mentally accept.

/Fredrik

 

[Demystifier]

[2106.03205] A response to the Mucino-Okon-Sudarsky's Assessment of Relational Quantum Mechanics (arxiv.org)

A response to the Muciño-Okon-Sudarsky’s Assessment of Relational Quantum mechanics Carlo Rovelli (Dated: June 8, 2021)

Today Muciño-Okon-Sudarsky replied:
https://arxiv.org/abs/2107.05817

 

[*now*]

Today Muciño-Okon-Sudarsky replied:
https://arxiv.org/abs/2107.05817

I don’t see any improvement on the article that has already been addressed.

 

[CarlB]

Today Muciño-Okon-Sudarsky replied:
https://arxiv.org/abs/2107.05817

Sadly the Muciño-Okon-Sudarsky paper only has two equations (1) and (2) which differ in defining the particle in the z-basis or x-basis of spin-1/2. Aren't these identical when converted into density matrices?

[edit] Oh I see, they're already identical as state vectors. Very late at night here.[/edit]Meanwhile, my paper on density matrices, RQM, quantum symmetry and the Standard Model is still under review at Foundations of Physics, most recently with "Reviewers Assigned" with a date of July 6. I'm guessing that they're getting wildly divergent reviews on it and are sending it out for more reviews in an attempt to find two that say the same thing.

 

[*now*]

I'll add the strong no-go theorem here that was mentioned in the earlier paper linked (Di Biagio, A., Rovelli, C. Stable Facts, Relative Facts. Found Phys 51, 30 (2021). https://doi.org/10.1007/s10701-021-00429-w, “Relative facts, stable facts”), and is in the following paper-

https://www.nature.com/articles/s41567-020-0990-x
Nat. phys 2020

Testing the reality of Wigner's friend's observations​

Kok-Wei Bong, Aníbal Utreras-Alarcón, Farzad Ghafari, Yeong-Cherng Liang, Nora Tischler, Eric G. Cavalcanti, Geoff J. Pryde, Howard M. Wiseman

Abstract

Does quantum theory apply at all scales, including that of observers? A resurgence of interest in the long-standing Wigner's friend paradox has shed new light on this fundamental question. Here---building on a scenario with two separated but entangled "friends" introduced by Brukner---we rigorously prove that if quantum evolution is controllable on the scale of an observer, then one of the following three assumptions must be false: "No-Superdeterminism", "Locality", or "Absoluteness of Observed Events" (i.e. that every observed event exists absolutely, not relatively). We show that although the violation of Bell-type inequalities in such scenarios is not in general sufficient to demonstrate the contradiction between those assumptions, new inequalities can be derived, in a theory-independent manner, which are violated by quantum correlations. We demonstrate this in a proof-of-principle experiment where a photon's path is deemed an observer. We discuss how this new theorem places strictly stronger constraints on quantum reality than Bell's theorem.
https://arxiv.org/abs/1907.05607
https://www.quantamagazine.org/a-new-theorem-maps-out-the-limits-of-quantum-physics-20201203/

 

[AndreiB]

Does quantum theory apply at all scales, including that of observers?

It does, but not as presented in Wigner's friend thought experiment. QM gives a simple formula for the uncertainty regarding the measured properties of various systems. For macroscopic systems, such as Wigner's friend, the uncertainty is practically 0. This means that macroscopic objects cannot be in any kind of relevant superposition. Their states can always be known with certainty by any observer.

Presumably, the uncertainty is preserved by isolating the system in a lab or a box. In order for such a lab/box to do its job it needs to stop its contents from interacting with the exterior. That means that the mass or charge of an "isolated" object is "deleted" from the universe once the lab/box is closed. This violates mass-energy or charge conservation so we can conclude that such a lab/box cannot exist.

 

[PeterDonis]

It does

More precisely, according to some physicists, it does. But according to other physicists, it does not. We do not have any conclusive experimental evidence either way. The question is open.

QM gives a simple formula for the uncertainty regarding the measured properties of various systems. For macroscopic systems, such as Wigner's friend, the uncertainty is practically 0. This means that macroscopic objects cannot be in any kind of relevant superposition.

Not in a "Schrodinger's cat" type scenario, i.e., where a macroscopic property of a macroscopic system is set up to depend on a single microscopic quantum event. For such a scenario, QM predicts a superposition of macroscopically distinct states (such as "live cat" and "dead cat"). One reason some physicists do not think QM applies at all scales is that such states do not seem physically reasonable.

 

[AlexCaledin]

QM predicts the probabilities! The superposition is a thinking/calculating tool.

 

[PeterDonis]

QM predicts the probabilities! The superposition is a thinking/calculating tool.

Under certain interpretations, yes. But not others.

 

[AndreiB]

Not in a "Schrodinger's cat" type scenario, i.e., where a macroscopic property of a macroscopic system is set up to depend on a single microscopic quantum event. For such a scenario, QM predicts a superposition of macroscopically distinct states (such as "live cat" and "dead cat"). One reason some physicists do not think QM applies at all scales is that such states do not seem physically reasonable.

The underlying assumption is that it is possible, at least in principle, to isolate the cat. It's easy to see that it cannot be done.

Let's say that a live cat moves inside the box. I can detect this motion, from outside the box, by using a torsion balance. The only way to counter that would be to build a box that can stop gravity. Such a box would, from the point of view of the outside, delete the mass of the cat from the universe, violating the mass/conservation principle. So, such a box cannot exist.

We can also notice that a live cat would have electric currents flowing in its brain. I can also detect the (static) electric field associated with those currents from outside the box, otherwise the box would violate charge conservation.

So, a cat, or any other object that has charge and mass (which includes pretty much everything) cannot be isolated from the exterior. It always interacts with the exterior. The state of such an object is knowable by any observer within the limits of the uncertainty principle.

 

[PeterDonis]

The underlying assumption is that it is possible, at least in principle, to isolate the cat. It's easy to see that it cannot be done.

The cat doesn't have to be isolated indefinitely, only long enough for the experiment to run. That might only be a few seconds if the quantum system is chosen appropriately.

Let's say that a live cat moves inside the box.

And if it doesn't, for the duration of the experiment, you can't detect the cat inside the box by this means. Or you could isolate the box from anything like a torsion balance that would allow detection of motion inside it. For example, you could have the box in free fall in deep space, not connected to anything else, for the duration of the experiment.

We can also notice that a live cat would have electric currents flowing in its brain.

Which can be isolated by making the box a Faraday cage.

a cat, or any other object that has charge and mass (which includes pretty much everything) cannot be isolated from the exterior.

If this argument were true, it would apply to electrons, since they have both charge and mass. But we know we can run experiments on electrons that show superpositions. So this argument cannot be true.

You could try to argue that a macroscopic object cannot be isolated from its environment due to its mass, or electric currents inside it, or something like that. But, as I noted above, the object would not need to be isolated forever, just long enough to run a Schrodinger's cat-type experiment. Your arguments do not show that that is impossible.

 

[AndreiB]

The cat doesn't have to be isolated indefinitely, only long enough for the experiment to run. That might only be a few seconds if the quantum system is chosen appropriately.

Sure, but the cannot be isolated for any amount of time.

Or you could isolate the box from anything like a torsion balance that would allow detection of motion inside it. For example, you could have the box in free fall in deep space, not connected to anything else, for the duration of the experiment.

This does not solve the problem. As long as there is some motion (like a beating heart) you have a change of the mass distribution. Such a change is measurable by its gravitational effects. One or more torsion balances could resolve the mass distribution inside the box. By placing the box in space you only keep its center of mass in the same place.

Which can be isolated by making the box a Faraday cage.

Such a cage cannot shield static electric or magnetic fields, only EM waves. If one could shield a charge, a violation of charge conservation would occur. So it has to be impossible.

If this argument were true, it would apply to electrons, since they have both charge and mass. But we know we can run experiments on electrons that show superpositions. So this argument cannot be true.

The electrons can be in superpositions because of the uncertainty principle, not because you isolate them in a box. The uncertainty principle applies for all observers equally, inside or outside the box. The uncertainty principle is not relevant for macroscopic objects, this is why they cannot be superposed. Sure, uncertainty applies to all objects, but for macroscopic ones it's not observable. The cat could be in a position superposition with a separation of a Planck unit or so, but this is not what is claimed here.

You could try to argue that a macroscopic object cannot be isolated from its environment due to its mass, or electric currents inside it, or something like that.

Exactly. The only limitation is the uncertainty principle. In fact microscopic objects, like electrons cannot be isolated either, for the same reason - mass and charge conservation. The mass and charge of the electron is measurable from outside the box. It's just that the measurements show the expected deviations so you gain nothing from placing the electron in a box.

But, as I noted above, the object would not need to be isolated forever, just long enough to run a Schrodinger's cat-type experiment. Your arguments do not show that that is impossible.

Time is not an issue here. The object cannot be isolated for any time, no matter how small.