Can we change our concept of reality to better understand quantum theory?

[Simple question]

Moderator's note: this thread is a spin-off of https://www.physicsforums.com/threa...hat-hardware-is-to-computation-theory.1052331

If, in QM, the "hardware" really existed, I would be realist

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lightarrow

If you think we live in a un-realistic simulation, it is running on some hardware anyway.

 

[lightarrow]

If you think we live in a un-realistic simulation, it is running on some hardware anyway.

I don't think we live in a simulation at all. I think that some properties of the particles don't exist before having measured them.

 

[Simple question]

I don't think we live in a simulation at all. I think that some properties of the particles don't exist before having measured them.

"Some properties", given you recognize they exist "at some point", cannot go "in and out of existence".
Especially if they are conserved quantities, and furthermore conserved instantly across huge real-space-time volume. If you think so, this count as un-realistic thinking.

Yet if you also think those "properties" are completely defined by linear equations, those "properties" are perfectly hosted realistically and non-locally in the abstract mathematics of QM. You may not name this "a simulation", but those type of beable run only into physicists brains. I think this is equivalent to a simulation.

If you really think there is something else (than that simulation), this "else" is missing from QM recipe. You simply cannot reproduce all of reality with it.

You may not care, and that's fine. Other prefer to think of science as a way to explore reality, and not the other way around.

 

[lightarrow]

"Some properties", given you recognize they exist "at some point", cannot go "in and out of existence".
Especially if they are conserved quantities, and furthermore conserved instantly across huge real-space-time volume. If you think so, this count as un-realistic thinking.

Yet if you also think those "properties" are completely defined by linear equations, those "properties" are perfectly hosted realistically and non-locally in the abstract mathematics of QM. You may not name this "a simulation", but those type of beable run only into physicists brains. I think this is equivalent to a simulation.

If you really think there is something else (than that simulation), this "else" is missing from QM recipe. You simply cannot reproduce all of reality with it.

You may not care, and that's fine. Other prefer to think of science as a way to explore reality, and not the other way around.

Just to understand better what you think on this subject (I haven't read all your posts in this very long thread): do Ag atoms passing a Stern-Gerlach device with B field along Z axis "really" have a magnetic moment along Z axis?
Wich is the exact physical content of the word "real" in this case, according to your vision (and I don't mean it have to be different than mine)?
Edit. I mean: do the Ag atoms have that property before passing the magnet?

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Lightarrow

 

[Simple question]

Just to understand better what you think on this subject (I haven't read all your posts in this very long thread): do Ag atoms passing a Stern-Gerlach device with B field along Z axis "really" have a magnetic moment along Z axis?
Wich is the exact physical content of the word "real" in this case, according to your vision (and I don't mean it have to be different than mine)?

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Lightarrow

On the subject of ontology, I think it(they) define a kind of metric in the space of theories(map). It does not give you true or false statement, but direction and distance on where(and how) your maps should lead you. So, applying this to your question:

If after some haphazard observation of some weird magnetic force, I start testing reality, for those constant and predictable properties, I may try to formalize a beable named "magnetic moment". Then later on, I may build a apparatus to test it (named Stern-Gerlach in our multiverse). The same story goes for all observable properties.

So my understanding is quite simple, those thing are real by definition, they never are "not observed". Counterfactual claims about what they don't have between their not-measurement, are epistemological, thus not real. This does not means they are not useful, they are, but also made by "made up" physicists and "made up" mathematics.

So yes, spin is real, it is quantized, can be superposed and entangled. It obviously exist (really have), because everywhere we look we found it. Those beable will be "real" until I found another one that fit the bills even better (ie string or what not)

 

[lightarrow]

On the subject of ontology, I think it(they) define a kind of metric in the space of theories(map). It does not give you true or false statement, but direction and distance on where(and how) your maps should lead you. So, applying this to your question:

If after some haphazard observation of some weird magnetic force, I start testing reality, for those constant and predictable properties, I may try to formalize a beable named "magnetic moment". Then later on, I may build a apparatus to test it (named Stern-Gerlach in our multiverse). The same story goes for all observable properties.

So my understanding is quite simple, those thing are real by definition, they never are "not observed". Counterfactual claims about what they don't have between their not-measurement, are epistemological, thus not real. This does not means they are not useful, they are, but also made by "made up" physicists and "made up" mathematics.

So yes, spin is real, it is quantized, can be superposed and entangled. It obviously exist (really have), because everywhere we look we found it. Those beable will be "real" until I found another one that fit the bills even better (ie string or what not)

Ok, maybe we don't have a very different visions, but that spin component cannot be "real" in the sense Einstein, Podolsky, Rosen gave in their famous paper: as you know it's not a "hidden variable".
Furthermore, do you ascribe the "reality" of what you wrote to the Ag atoms only or to the set "Ag atoms + experimental setup" or something else?

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Lightarrow

 

[Simple question]

Ok, maybe we don't have a very different visions, but that spin component cannot be "real" in the sense Einstein, Podolsky, Rosen gave in their famous paper: as you know it's not a "hidden variable".
Furthermore, do you ascribe the "reality" of what you wrote to the Ag atoms only or to the set "Ag atoms + experimental setup" or something else?

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Lightarrow

Indeed it is certainly is not a "local hidden variable", although Bohmian's fellow try hard to safeguard this locality, at the expense of "uncalssical-unobservable-trajectories". I am not sure sure I subscribe to this, but as @Demistifier says often, that ontology is at least a good mental framework, to keep things as real as possible.

As for the second point, I would say properties of the Ag atoms belongs to the Ag atoms only.

 

[lightarrow]

Indeed it is certainly is not a "local hidden variable", although Bohmian's fellow try hard to safeguard this locality, at the expense of "uncalssical-unobservable-trajectories". I am not sure sure I subscribe to this, but as @Demistifier says often, that ontology is at least a good mental framework, to keep things as real as possible.

As for the second point, I would say properties of the Ag atoms belongs to the Ag atoms only.

So, in your vision, either the particles can exchange information faster than c, or they follow unobservable trajectories? This seems similar to the "virtual world" you were talking in your first reply to me ;-)
Concerning the properties measured, I can't understand how they can attain to the Ag atoms only when we know (at least) that a measurement apparatus, in general, changes the quantum system's state.

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Lightarrow

 

[Simple question]

So, in your vision, either the particles can exchange information faster than c, or they follow unobservable trajectories?

Yes, they share information instantaneously, or follow some trajectories, or collapse spontaneously (GRW), or other ontologies that I don't even understand (like TI, the Thermal Interpretation) seems to fall in the realist category
As I am not a fan of superderterminism, I think only the former and possibly TI can logically account for entanglement swapping in some realistic sense.

This seems similar to the "virtual world" you were talking in your first reply to me ;-)

Absolutely, for the former anyway, it is easy to "picture it" this way. The things that is important with ontology, is that was is "real" is what is probed, that virtual world "hardware".

Concerning the properties measured, I can't understand how they can attain to the Ag atoms only when we know (at least) that a measurement apparatus, in general, changes the quantum system's state.

Well, how could it be otherwise ? What is logically minimal is that the measuring apparatus will need to also contains/deal in the properties being measured (like spin), or else nothing will be able to "change" or be "exchanged". I don't think a measuring device "gives", or "create" spin of the Ag atoms.
Or maybe I misunderstood your question ?

 

[Fra]

So, in your vision, either the particles can exchange information faster than c, or they follow unobservable trajectories?

In what sense does "particles" exchange "information"?

Agents or observers exchange information (ie about each other), but for those into other interpretations, what exactly does "particles exchanging information" even mean?

/Fredrik

 

[lightarrow]

1) Yes, they share information instantaneously, or follow some trajectories, or collapse spontaneously (GRW), or other ontologies that I don't even understand (like TI, the Thermal Interpretation) seems to fall in the realist category
As I am not a fan of superderterminism, I think only the former and possibly TI can logically account for entanglement swapping in some realistic sense.2) Absolutely, for the former anyway, it is easy to "picture it" this way. The things that is important with ontology, is that was is "real" is what is probed, that virtual world "hardware".3) Well, how could it be otherwise ? What is logically minimal is that the measuring apparatus will need to also contains/deal in the properties being measured (like spin), or else nothing will be able to "change" or be "exchanged". I don't think a measuring device "gives", or "create" spin of the Ag atoms.
Or maybe I misunderstood your question ?

1) If we allow information to be shared instantaneously, everything can happen. It can't be.
2) I could accept this idea if you told me that "the hardware" is in the quantum system and in the measurement apparatus, but it seems you don't think in these terms.
3) The Ag atoms have a spin, but don't have a "z component of the spin", before passing the Stern-Gerlach magnet with B field along Z. They have such property only after passing the field, so it's the apparatus which creates it. But a subsequent measurement along the Y axis (orthogonal to Z axis and to the X axis along which is the beam) destroys the previous property. This is another clue that the measurement apparatus has a very active role in the creating what is "measured".
(All things we already know, of course).

Maybe you think the Ag's spin is "the hardware" and the apparatus is "the software"?

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Lightarrow

 

[lightarrow]

1) In what sense does "particles" exchange "information"?

2) Agents or observers exchange information (ie about each other), but for those into other interpretations, what exactly does "particles exchanging information" even mean?

/Fredrik

1) I wrote hidden variables don't exist, Simple question replied putting the accent on the non-existence of local hidden variables. For what I know, this opens the possibility that the first measurement of the property (e. g. the Sz) on one of a couple of entangled particles can transfer instantaneously the message to the other particle (or the other measuring apparatus) the information that the value it has to register is the opposite of the first (or whatever correlated value).
2) Sorry but I don't know what you mean with "for those into other interpretations". Who are you referring to? And which are the "other interpretations"? I'm not much aware of "interpretations" in QM in general (just read a little bit) so I couldn't even say which I am unconsciously following (if I'm following one or none or a mix among some).

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Lightarrow

 

[Simple question]

1) If we allow information to be shared instantaneously, everything can happen. It can't be.

In what sense "everything can happen" ? In computing we change pointer all the time, and in no sense "everything happen". Anyway that's what we seem to measure, so why would I deny experimental result ?

2) I could accept this idea if you told me that "the hardware" is in the quantum system and in the measurement apparatus, but it seems you don't think in these terms.

Well, the hardware, the beables, is the substrate for both Quantum system, and measurement apparatus. There is no point in thinking from an ontological point of view if not solving the measurement problem.

3) The Ag atoms have a spin, but don't have a "z component of the spin", before passing the Stern-Gerlach magnet with B field along Z.

You don't know that. That's the point of measuring it. BTW if it was already in a some spin eigenstate along the z component, you would probably disagree with yourself.

They have such property only after passing the field, so it's the apparatus which creates it.

This is a counterfactual claims. I don't know how this help to think in those term. It may be fine to think that abstractly, but the correct phrasing would be "They have a un-known(measured) property, before passing the field". Spin is conserved. Ag atom always have some, a magnet do not inject spin into a Ag atom, it interact with it (filter it).

But a subsequent measurement along the Y axis (orthogonal to Z axis and to the X axis along which is the beam) destroys the previous property.

It certainly scramble it. It does not make it disappear into the void.

This is another clue that the measurement apparatus has a very active role in the creating what is "measured".
(All things we already know, of course).

Yes, I agree with this. You seem to think that those apparatuses can synchronize themselves even though they belong to different separate space time cones (3 apparatuses in the context of entanglement sapping).
Well, it may be so, but I prefer the simpler explanation that the particles are the "carrier" of entanglement, after all they a prepared in this state, not the apparatuses.

Maybe you think the Ag's spin is "the hardware" and the apparatus is "the software"?

No, I think both have to run on the same hardware/beable. There is no point in separating them.
The software is what we are building on top of. QM in this case.

 

[Fra]

I didn't perhaps follow the exact discussion between you two, I justed wanted to question how we use the term information, and where it is encoded...

1) I wrote hidden variables don't exist, Simple question replied putting the accent on the non-existence of local hidden variables. For what I know, this opens the possibility that the first measurement of the property (e. g. the Sz) on one of a couple of entangled particles can transfer instantaneously the message to the other particle (or the other measuring apparatus) the information that the value it has to register is the opposite of the first (or whatever correlated value).
2) Sorry but I don't know what you mean with "for those into other interpretations". Who are you referring to? And which are the "other interpretations"? I'm not much aware of "interpretations" in QM in general (just read a little bit) so I couldn't even say which I am unconsciously following (if I'm following one or none or a mix among some).

By "those other" I meant all those (most) that does NOT think in terms of agents interacting.

I would say that in normal QM/QFT and some minimal interpretation or CI like interpreation, it is the macroscopic environment which is the "observer", and it's in there that information about "particles" is encoded. So when we observe TWO particles, information about BOTH particles are encoded in the environmnent. The notion that these two particles encode or exchange information about each other, is not well defined in MOST major interpretations such as CI etc.

In standard interpretations, one can OTOH consider that several classical obserers (Alice and Bob) exchange inforamtion about the experiment. But this is where the tension appears, becauase they are both supposed to be part of the classical domain; and the instant Alice and Bob interact with each other in a quantum way, relative to a third observer (which is also part to classical world) current theory runs into trouble; we aren't allowed to do that.

/Fredrik

 

[Simple question]

By "those other" I meant all those (most) that does NOT think in terms of agents interacting.

Maybe you can elucidate your position here. Are those agent 3D beable or not ? Are they ontological ?

I would say that in normal QM/QFT and some minimal interpretation or CI like interpreation, it is the macroscopic environment which is the "observer", and it's in there that information about "particles" is encoded.

If I were to take seriously the notion of agent, I would want to understand how it fundamentally differs from a "measuring device". Does it have agency ? Also, getting back to computer analogy, I would like to understand why you use "encoded"(uniquely stored in computing) instead of "recorded" (a cloned copy at that time)

So when we observe TWO particles, information about BOTH particles are encoded in the environment. The notion that these two particles encode or exchange information about each other, is not well defined in MOST major interpretations such as CI etc.

un-separability of state is pretty well defined in my book. Especially in CI where there is absolutely no bother on where and how this non-locality "is stored/realized". That is the cop-out of most "software guys", that "hardware guys" have a hard time with.

In standard interpretations, one can OTOH consider that several classical obserers (Alice and Bob) exchange inforamtion about the experiment. But this is where the tension appears, becauase they are both supposed to be part of the classical domain;

How is this relevant is the thing that keep eluding me. If all these "exchanges of information" are classical, none of it requires QM. Anyone doing those "standard interpretation" is talking from a classical-information-beadle-perspective that information "is real". Not that is only "become real" only when "meeting locally".

If I were take seriously the notion of macroscopic measuring device as "beable-of-information", I would trust my hardware guts, that is: it will stop being a measuring device at some point. Once the screen of a Stern-Gerlach is "burnout", does the magnetic field stop filtering Ag atoms ? Because we(or it) aren't going anymore to be able to "record/encode" anything anymore !
For me this clearly show that "the properties" belong to the particles, not the measuring device.

and the instant Alice and Bob interact with each other in a quantum way, relative to a third observer (which is also part to classical world) current theory runs into trouble; we aren't allowed to do that.

I don't think they run into trouble, everything is fine and classic hardware wise. There is simply no software that can explains this non-locality without hand-waving.
Also I am not sure what we "aren't allow to do". A hardware guy would say "hand-waving is not allowed", a software guy would say "declare the theory as incomplete/inconsistent is not allowed".

One of those attitude is not scientific.

 

[lightarrow]

1) In what sense "everything can happen" ? In computing we change pointer all the time, and in no sense "everything happen". Anyway that's what we seem to measure, so why would I deny experimental result ?

2) Well, the hardware, the beables, is the substrate for both Quantum system, and measurement apparatus. There is no point in thinking from an ontological point of view if not solving the measurement problem.

3) You don't know that. That's the point of measuring it. BTW if it was already in a some spin eigenstate along the z component, you would probably disagree with yourself.

4) This is a counterfactual claims. I don't know how this help to think in those term. It may be fine to think that abstractly, but the correct phrasing would be "They have a un-known(measured) property, before passing the field". Spin is conserved. Ag atom always have some, a magnet do not inject spin into a Ag atom, it interact with it (filter it).

5) It certainly scramble it. It does not make it disappear into the void.

6) Yes, I agree with this. You seem to think that those apparatuses can synchronize themselves even though they belong to different separate space time cones (3 apparatuses in the context of entanglement sapping).
Well, it may be so, but I prefer the simpler explanation that the particles are the "carrier" of entanglement, after all they a prepared in this state, not the apparatuses.

7) No, I think both have to run on the same hardware/beable. There is no point in separating them.
The software is what we are building on top of. QM in this case.

1) Don't know what you mean with "in computing we change the pointer", I am talking of physical objects or real information of a signal, not something "artefact" like phase velocity or moving fast a laser beam on the Moon's surface which image seems to move > c.
2) Ok.
3) I don't know, but you don't know the opposite either. And when I wrote "... in general..." I intended exactly that the measurement doesn't change the state when it's in an eigenstate of the observable. But this does not change the concept at all: the measurement do changes the state in a general case.
4) But "they have an unknown property" is a claim you have to prove too! Because it implies "it has" that property before the measurement.
5) "Scramble" doesn't mean much (if I understood correctly what you mean): we are not talkin of having a spin but of "having a precise component z of the spin" ("precise" in the sense that is 1/2 or -1/2, that is, that the Ag atoms forms two thin signs on the screen instead of a bigger pitch).
6) Ok, but the preparation doesn't encompass the fact A will be measured (e.g.) as 0 and B as 1 :-)
7) Ok.

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Lightarrow

 

[Fra]

Maybe you can elucidate your position here. Are those agent 3D beable or not ? Are they ontological ?

My specific stance is non-standard, but just to position it for discussion it is a qbist derivative, a gaming abstraction where the "players" are observers, agents. The "winners" get to play on, the others are eliminated from the game. And agents are made of normal matter. Nothing else of course.

Given that the agent is central, it's as ontological as anything gets. But there is no fundanetal reference to spacetime. Spacetime, and in parcticular it's dimensionality is expected to be emergent, perhaps a bit like the optimal embedding dimension where the has best stability.

If I were to take seriously the notion of agent, I would want to understand how it fundamentally differs from a "measuring device"

The main difference is that a "measuremen device" in QM is classical/macroscopical device. An agent does not need to be classical. So I would say it's a generalisation. A classical measurement device is envision as a limting case where the "agent" is dominant in terms of infomation capacitry and computational capacity, and the "system" is essentially "small".

Does it have agency ? Also, getting back to computer analogy, I would like to understand why you use "encoded"(uniquely stored in computing) instead of "recorded" (a cloned copy at that time)

Encoded because it's recorded in a volatile hardware, the agents microstate. A classical measurement device is imagined as able to make irreversible and permanent records, that can be copied. An agents information can't just be "copied", it has to be inferred by other agents, which is a physical interaction.

Also I am not sure what we "aren't allow to do". A hardware guy would say "hand-waving is not allowed", a software guy would say "declare the theory as incomplete/inconsistent is not allowed".

What I meant is that QM, applies to "classical measurement devices", not to agents. This doesn't please me.
So if one wants to generalise the notion of observables, one may need to generalize the theory as well.

/Fredrik

 

[lightarrow]

I didn't perhaps follow the exact discussion between you two, I justed wanted to question how we use the term information, and where it is encoded...By "those other" I meant all those (most) that does NOT think in terms of agents interacting.

I would say that in normal QM/QFT and some minimal interpretation or CI like interpreation, it is the macroscopic environment which is the "observer", and it's in there that information about "particles" is encoded. So when we observe TWO particles, information about BOTH particles are encoded in the environmnent. The notion that these two particles encode or exchange information about each other, is not well defined in MOST major interpretations such as CI etc.

In standard interpretations, one can OTOH consider that several classical obserers (Alice and Bob) exchange inforamtion about the experiment. But this is where the tension appears, becauase they are both supposed to be part of the classical domain; and the instant Alice and Bob interact with each other in a quantum way, relative to a third observer (which is also part to classical world) current theory runs into trouble; we aren't allowed to do that.

/Fredrik

Ah, where the "whole" information is encoded is another (or THE) mistery! Solving this is solving half the problem or most of it!
I only intended to say that it can't be encoded in the particles only, in my opinion. But you were talking about the information of the "measurements" only, weren't you? Then it's obviously in the environment, but after the interaction with the particle. So, the "whole" information is in both, isn't it?
Sorry if I use strange terms, I'm not used to the correct terminology.
Anyway I haven't understood much your last paragraph; probably you give for granted something I don't know ;-)

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Lightarrow

 

[Simple question]

1) Don't know what you mean with "in computing we change the pointer", I am talking of physical objects or real information of a signal, not something "artefact" like phase velocity or moving fast a laser beam on the Moon's surface which image seems to move > c.

I was looking for the justification of "anything can happens" if instantaneous correlation/collapse occurs. Because it does seems like it happens, in reality, not in some "epistemic update sense"

3) I don't know, but you don't know the opposite either.

No, that is not logical. I don't make claims about what does not exist, while you do.

And when I wrote "... in general..." I intended exactly that the measurement doesn't change the state when it's in an eigenstate of the observable. But this does not change the concept at all: the measurement do changes the state in a general case.

That is is up to you to justify why a measuring device does not work if the particle is in some eigenstate. A logical deduction is be-cause the tested property belong to the particle, not the measuring device. Any other rational should be stated more clearly.
BTW I am not saying the measuring device does not have any role. They obviously "change" things, even if only by revealing or collapsing properties... of quanta.

4) But "they have an unknown property" is a claim you have to prove too! Because it implies "it has" that property before the measurement.

Indeed, an that is Noether's theorem, conserved quantities, is some nice logical bedrock. Things pop'ing in and out of existence, conveniently, is not a realistic framework.
That's why the moon is there even when I stop looking at it. Nobody have to prove negatives in sound logic. It should be easy for anyone to show a single example of the opposite.

5) "Scramble" doesn't mean much (if I understood correctly what you mean): we are not talkin of having a spin but of "having a precise component z of the spin" ("precise" in the sense that is 1/2 or -1/2, that is, that the Ag atoms forms two thin signs on the screen instead of a bigger pitch).

One Ag atom do not form two thin signs. That's the point I am making. However you randomize (if you prefer) you next measure by changing the axis just add nothing to the analyses.
Some other un-realist escape to other fantasies like "ensemble of particle". Again, if you are a software guy, you don't really care about what nature is made of.

6) Ok, but the preparation doesn't encompass the fact A will be measured (e.g.) as 0 and B as 1 :-)

Indeed, but it shows clearly that measuring apparatus has NO active influence on the result (except filtering). If one happens to use the same angle then the other, they will always show perfectly correlated results.
So there is always the grand conspiration-theories like super-determinism, as a cop-out.
But I am under the impression that your explanation involves enormous ensemble of quantas (macroscopic devices), which then have to instantaneously conspire/communicate, to invent the right properties for some particles (and additionally know the history/preparation of all particles involved).

 

[lightarrow]

1) I was looking for the justification of "anything can happens" if instantaneous correlation/collapse occurs. Because it does seems like it happens, in reality, not in some "epistemic update sense"

2) No, that is not logical. I don't make claims about what does not exist, while you do.

3) That is is up to you to justify why a measuring device does not work if the particle is in some eigenstate. A logical deduction is be-cause the tested property belong to the particle, not the measuring device. Any other rational should be stated more clearly.
BTW I am not saying the measuring device does not have any role. They obviously "change" things, even if only by revealing or collapsing properties... of quanta.

4) Indeed, an that is Noether's theorem, conserved quantities, is some nice logical bedrock. Things pop'ing in and out of existence, conveniently, is not a realistic framework.
That's why the moon is there even when I stop looking at it. Nobody have to prove negatives in sound logic. It should be easy for anyone to show a single example of the opposite.

5) One Ag atom do not form two thin signs. That's the point I am making. However you randomize (if you prefer) you next measure by changing the axis just add nothing to the analyses.
Some other un-realist escape to other fantasies like "ensemble of particle". Again, if you are a software guy, you don't really care about what nature is made of.

6) Indeed, but it shows clearly that measuring apparatus has NO active influence on the result (except filtering). If one happens to use the same angle then the other, they will always show perfectly correlated results.
So there is always the grand conspiration-theories like super-determinism, as a cop-out.
But I am under the impression that your explanation involves enormous ensemble of quantas (macroscopic devices), which then have to instantaneously conspire/communicate, to invent the right properties for some particles (and additionally know the history/preparation of all particles involved).

1) Instantaneous correlations between entangled particles do happen. But this is not faster than c propagation of objects/signals/information.
2) What I intended is: I surely cannot prove my claim that property (value of Sz) does not exists before measurement, but we cannot even prove it does exist. An interpretation as: "existence of non local hidden variables" is not a prove. Is it?
3) Ah, yes, I agree, it's up to me. Not succeeded yet :-) Probably someone else, even here, has already done it.
4) Wait a moment! One thing is saying that if a particle has Sz = +1/2, then the other have to be Sz = -1/2 because of conservation laws, another thing is saying that "the particle A has Sz = +1/2" before its measurement.
5) Yes, one Ag atom doesn't form two thin signs. The same with a single photon passing the two slits: it forms a single point on the screen. But nonetheless it passes both slits at the same time. This is the standard description.
6) The "filtering" you are referring to, is an active influence. Furthermore, how does it do it?

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Lightarrow

 

[Simple question]

1) Instantaneous correlations between entangled particles do happen. But this is not faster than c propagation of objects/signals/information.

Nobody said that. Actually, if taken literally, QM entangled state (not the eventual beable) encode properties that are non-local. There is no logical issue here. How can 1 "thing" communicate or signal ? You need two ends for a communication, or a start and an end for a propagation.

2) What I intended is: I surely cannot prove my claim that property (value of Sz) does not exists before measurement, but we cannot even prove it does exist. An interpretation as: "existence of non local hidden variables" is not a prove. Is it?

If one decide to use ontologies, this issue resolve itself. Properties are observed, and are conserved. The software do not have to prove it, just to make those valid prediction. If many agree that QM does, the many interpretations about how that software could run are not in such agreement.
That is how I understand the OP analogy. So I agree that existence of non-local hidden variable is not a proof. But it is a necessary if you also want realistic beable like "properties". That's a logical conclusion of Bell's proof. The other is that everything is local, and God plays with Unitary dice.

4) Wait a moment! One thing is saying that if a particle has Sz = +1/2, then the other have to be Sz = -1/2 because of conservation laws, another thing is saying that "the particle A has Sz = +1/2" before its measurement.

But nobody said that ! You want to introduce the angle Z of the apparatus as a state preparation, it is not. I just said it has a spin. In your mind, using counterfactual reasoning, if you could re-run the same experiments on the same Ag atoms, just rotating it 180 degree, would the thin signs be inverted too, or just some other random distribution ?

5) Yes, one Ag atom doesn't form two thin signs. The same with a single photon passing the two slits: it forms a single point on the screen. But nonetheless it passes both slits at the same time. This is the standard description.

The wavy part is not the difficult thing to understand about the description. The strange thing is why we can not, ever, observe it. I consider the recourse to ontologies as a way to solve that issue (and maybe discover new things (not in the theory) in the process.

6) The "filtering" you are referring to, is an active influence. Furthermore, how does it do it?

Interacting with it. Measuring it. Using some of the forces/field of nature... which is difficult to do without big measurement device (the size of the LHC comes to mind)
There is no problem if you think in terms of those beable, but is indeed a complete mystery otherwise.

 

[lightarrow]

1) Nobody said that. Actually, if taken literally, QM entangled state (not the eventual beable) encode properties that are non-local. There is no logical issue here. How can 1 "thing" communicate or signal ? You need two ends for a communication, or a start and an end for a propagation.

2) If one decide to use ontologies, this issue resolve itself. Properties are observed, and are conserved. The software do not have to prove it, just to make those valid prediction. If many agree that QM does, the many interpretations about how that software could run are not in such agreement.
That is how I understand the OP analogy. So I agree that existence of non-local hidden variable is not a proof. But it is a necessary if you also want realistic beable like "properties". That's a logical conclusion of Bell's proof. The other is that everything is local, and God plays with Unitary dice.

3) But nobody said that ! You want to introduce the angle Z of the apparatus as a state preparation, it is not. I just said it has a spin. In your mind, using counterfactual reasoning, if you could re-run the same experiments on the same Ag atoms, just rotating it 180 degree, would the thin signs be inverted too, or just some other random distribution ?

4) The wavy part is not the difficult thing to understand about the description. The strange thing is why we can not, ever, observe it. I consider the recourse to ontologies as a way to solve that issue (and maybe discover new things (not in the theory) in the process.

5) Interacting with it. Measuring it. Using some of the forces/field of nature... which is difficult to do without big measurement device (the size of the LHC comes to mind)
There is no problem if you think in terms of those beable, but is indeed a complete mystery otherwise.

1) True, you didn't say that; then what are we talking about? I believed you were proposing a sort of "hidden variable" interpretation. By the way, what do you think of those who propose as interpretation the rejecting of dynamical separability?
See:
https://www.scientificamerican.com/...m-may-be-a-poison-pill-for-objective-reality/
2) Sorry, don't know what "beable" means (and so not even "realistic beable").
3) Ok, sorry, I explained very badly; I intended to select only those Ag atoms who goes up (z+), for example, and then measure to them the y component of spin with a device rotated of 90º.
4) What exactly do you mean here with "observe it"?
5) "Interacting" and "measuring" is not an answer, it's the same thing I have asked :-)
How does this interaction/measurement happen? Of course no one knows yet, so saying "the instrument filters those particles" doesn't say much.
I assumed, but now I'm not sure at all, for what you wrote here, that with "filtering" you intended: "Each Ag atoms had a magnetic moment, casually oriented, even before measurement, and the measuring device selected those oriented along Z. Did you intend this?

--
Lightarrow

 

[Simple question]

1) True, you didn't say that; then what are we talking about?

Ontologies, they pro & cons.

I believed you were proposing a sort of "hidden variable" interpretation.

Well, yes, the variable/properties are hidden. That's why we need to measure them.

By the way, what do you think of those who propose as interpretation the rejecting of dynamical separability?
See:
https://www.scientificamerican.com/...m-may-be-a-poison-pill-for-objective-reality/

Interesting, but I am not sure what "information preservation" means, in their assumption. It seems contradictory to both QM and the second law of thermodynamic.

2) Sorry, don't know what "beable" means (and so not even "realistic beable").

It means ontology. "Realitic beable" is kind of a tautology, sorry.

3) Ok, sorry, I explained very badly; I intended to select only those Ag atoms who goes up (z+), for example, and then measure to them the y component of spin with a device rotated of 90º

Yes, so before your second measurement, would you say that the particle is in some z+ eigenstate state (and measured property) ? It seems contradictory to me to also claim that before the first measurement, the particle has no property, just because the state is maximally unknown.

4) What exactly do you mean here with "observe it"?

Standard physics, you get some event. In QM you aditionally get a collapse/update of state, you cannot NOT collapse the wave function (weak measurement aside ?)

5) "Interacting" and "measuring" is not an answer, it's the same thing I have asked :-)
How does this interaction/measurement happen? Of course no one knows yet, so saying "the instrument filters those particles" doesn't say much.

Exactly, measurement "deus ex-machina" does not explain anything. But interacting locally trough force does. Remember that I don't want to solve the issue of non-realist. I can as well adopt some (possibly many, ontologies, where that issue is non-existent (like GRW))

I assumed, but now I'm not sure at all, for what you wrote here, that with "filtering" you intended: "Each Ag atoms had a magnetic moment, casually oriented, even before measurement, and the measuring device selected those oriented along Z. Did you intend this?

You assumed right, except the AG atom may also have many superposed magnetic moment, possibly shared with some entangle partner.
It may not be the right ontology, but I find it better (and possibly falsifiable) than "it is likely that some property will pop into existence"

 

[lightarrow]

1) Ontologies, they pro & cons.

2) Well, yes, the variable/properties are hidden. That's why we need to measure them.

3) It means ontology. "Realitic beable" is kind of a tautology, sorry.

4) Yes, so before your second measurement, would you say that the particle is in some z+ eigenstate state (and measured property) ? It seems contradictory to me to also claim that before the first measurement, the particle has no property, just because the state is maximally unknown.

5) Standard physics, you get some event. In QM you aditionally get a collapse/update of state, you cannot NOT collapse the wave function (weak measurement aside ?)

6) Exactly, measurement "deus ex-machina" does not explain anything. But interacting locally trough force does. Remember that I don't want to solve the issue of non-realist. I can as well adopt some (possibly many, ontologies, where that issue is non-existent (like GRW))

7) You assumed right, except the AG atom may also have many superposed magnetic moment, possibly shared with some entangle partner.
It may not be the right ontology, but I find it better (and possibly falsifiable) than "it is likely that some property will pop into existence"

1) Ok
2) "Hidden" in the sense of ontologies like De Broglie - Bohm interpretation?
3) Ok.
4) Of course after the first experiment, selecting the beam which goes up, the state goes in z+ eigenstate. By definition. If "the particle had no property" before this first measurement you can understand from the fact there is another beam which goes down. If there is an only beam which goes up, the system was already in an the z+ eigenstate of Sz. (In analogous way for an only beam going down). In this case the Sterng-Gerlach apparatus doesn't affect the system which really has that property *relatively to that apparatus aligned along Z*. But it doesn't have that property relatively to an appratus which is rotated 90º respect the first (that is, along Y). So, in my vision, the property attains to both the system and the measuring apparatus. Using a mataphore, it would be something like a body's velocity: it needs an "external" reference frame; it has no physical meaning without it. Or, using another one, it would be as the Alexandrite stone's colour: green if observed at the Sun's light, red under a conventional lamp's light. (But things are more complicated in the case we are discussing).
5) Ok. I intended that the pattern with many bands formed on the screen after many particles hit it would be an "observation" of the wave-like property of the system.
6) Ok
7) I don't understand well here. Let's make an example in a plane only: if, e. g., I superpose a magnetic of magnitude m oriented along +X with another with same magnitude oriented along +Y, don't you get a magnetic moment exactly oriented as the 45º bisector of the 1 and 3 quadrant?

--
Lightarrow

 

[Simple question]

If "the particle had no property" before this first measurement you can understand from the fact there is another beam which goes down.

If the particle had no property, there would be a central unique spot. We never observe that. You cannot measure something that does not exist previously.

So, in my vision, the property attains to both the system and the measuring apparatus

This is also tautological. If your throw banana at a Stern-Gerlach it won't work. I am not being facetious here.
If you use some other Stern-Gerlach (other dimension power), the spot will be differents. But the +-1/2 spin not. Really I think I am not going anywhere in trying to explain how some ontology can be useful on the bases of those logical ground.

Using a mataphore, it would be something like a body's velocity: it needs an "external" reference frame; it has no physical meaning without it.

Perfect metaphor. Speed is not conserved, it is not a ontological property of object (no physical meaning). Momentum is.

I don't understand well here. Let's make an example in a plane only: if, e. g., I superpose a magnetic of magnitude m oriented along +X with another with same magnitude oriented along +Y, don't you get a magnetic moment exactly oriented as the 45º bisector of the 1 and 3 quadrant?

Quantum superposition is more complex, there is a phase, and there is no classical equivalence for entanglement... but I am pretty sure you know that.

But there seems to be (postulated in theory and in practice) a size requirement on a measuring apparatus. That "Heisenberg cut" is still a mystery. It is not predicted in the theory.
How small can we made a Stern-Gerlach, before it stop being one ? This is also a question about the ontological nature of a measurement device. No that I know the answer, but I am not denying the question existence (addressed for example by decoherence)

AFAIK un-realist stances are more than un-interested at all by this, they have tie their hand behind their back (figuratively of course ;-)

 

[lightarrow]

1) If the particle had no property, there would be a central unique spot. We never observe that. You cannot measure something that does not exist previously.

2) This is also tautological. If your throw banana at a Stern-Gerlach it won't work. I am not being facetious here.
If you use some other Stern-Gerlach (other dimension power), the spot will be differents. But the +-1/2 spin not. Really I think I am not going anywhere in trying to explain how some ontology can be useful on the bases of those logical ground.

3) Perfect metaphor. Speed is not conserved, it is not a ontological property of object (no physical meaning). Momentum is.

4) Quantum superposition is more complex, there is a phase, and there is no classical equivalence for entanglement... but I am pretty sure you know that.

5) But there seems to be (postulated in theory and in practice) a size requirement on a measuring apparatus. That "Heisenberg cut" is still a mystery. It is not predicted in the theory.
How small can we made a Stern-Gerlach, before it stop being one ? This is also a question about the ontological nature of a measurement device. No that I know the answer, but I am not denying the question existence (addressed for example by decoherence)

6) AFAIK un-realist stances are more than un-interested at all by this, they have tie their hand behind their back (figuratively of course ;-)

1) No, with "had no property" I intended "had not z+ (or z-) magnetic moment".
2) "interaction with the instrument" is a thing, "instrument affecting the system so that it creates the measured property" is another. A photon which is in a 50/50 superposition of polarization states along x and along y is neither "x polarized" nor "y polarized", but a measure of its x polarization gives "yes" or "no" and not "half yes and half no". What I believe is that, in a sense, the "measurement" forces the system to have a property it actually hadn't.
3) You can take momentum instead of speed, if you prefer, but it would be the same: momentum is not frame invariant.
4) Ok.
5) I agree: the size requirement of the measuring apparatus is another mystery, related, I would add, with the issue of where is the quantum-classical border.
6) Why?

--
Lightarrow

 

[physika]

Moderator's note: this thread is a spin-off of https://www.physicsforums.com/threads/ontology-is-to-quantum-theory-what-hardware-is-to-computation-theory.1052

Or a Split off on MWI ?

 

[Simple question]

1) No, with "had no property" I intended "had not z+ (or z-) magnetic moment"

Something without magnetic moment (whatever the orientation) is of not use for a Stern-Gerlach.

2) "interaction with the instrument" is a thing, "instrument affecting the system so that it creates the measured property" is another.

The thing created, the records, are change affecting the measurement device only. That is what you read from, the macro-scope. Everything else is interpretation. But if you have realist ontologies, and even un-realist ones (like consciousness created ensemble), I've never heard that spin is created out of thin air.
Chosen(collapse), maybe, but not created(?).

A photon which is in a 50/50 superposition of polarization states along x and along y is neither "x polarized" nor "y polarized", but a measure of its x polarization gives "yes" or "no" and not "half yes and half no".

Yes. Again, "gives" equals "collapse" in my book. And in my book, like in your, we never observe photon with anything BUT clear YES/NO. For me this include all photon, in all the universe, before or after the measuring device.

What I believe is that, in a sense, the "measurement" forces the system to have a property it actually hadn't.

By you own logic, this is not possible. Photon do not have "half yes and half no". So they could not be "given" anything. I could understand you if you said the measurement "picked" on of those possible outcome.
Also Bell have shown that those measurements device must be spook'ly connected if they are supposed to "force system" according to QM.

momentum is not frame invariant.

What ?

Why?

Because you don't have to seek for an explanation if you are content with "my mind create results", or "it just is"

 

[lightarrow]

1) Something without magnetic moment (whatever the orientation) is of not use for a Stern-Gerlach.

2) The thing created, the records, are change affecting the measurement device only. That is what you read from, the macro-scope. Everything else is interpretation. But if you have realist ontologies, and even un-realist ones (like consciousness created ensemble), I've never heard that spin is created out of thin air.
Chosen(collapse), maybe, but not created(?).

3) Yes. Again, "gives" equals "collapse" in my book. And in my book, like in your, we never observe photon with anything BUT clear YES/NO. For me this include all photon, in all the universe, before or after the measuring device.

4) By you own logic, this is not possible. Photon do not have "half yes and half no". So they could not be "given" anything. I could understand you if you said the measurement "picked" on of those possible outcome.
Also Bell have shown that those measurements device must be spook'ly connected if they are supposed to "force system" according to QM.

5) What ?

6) Because you don't have to seek for an explanation if you are content with "my mind create results", or "it just is"

1) Never written "it has no magnetic moment". I've written, it has no magnetic moment "in the z+ direction" and "in the z_ direction" (unless the system is already in the up, or down, eigenstate of magnetic moment, of course).
2) Yes, the records are changes affecting the device only. *Everything* else is interpretation: both what I wrote about the device affecting the system's property (that is having or not z+ component of magnetic momentum) and the system already having that property before measurement (magnetic moments already z+ and z), and the device "only separating them".
Hope to be expressed better what I mean, sorry if it wasn't clear before.
3) Yes, collapse, of course, I just wrote it in a different way, hope it's not necessary to always repeat the same word to express a concept and certainly I didn't mean to express something weird.
4) We have photons which polarization state is in the plane orthogonal to the X-Y plane and which intersection with the last one is the straight line y = x, that is the 45º bisector of the first and third quadrant. Said with an analogy/metaphor: Does the vector xi+yj on the plane have "only x or only y components"? Certainly not. In the same way if a polarization state of the photon is at 45º, does the polarizing filter along X axis measures its x component? I would say no, since the subsequent detector register "yes" or "no" photn presence.
5) Don't understand your "what". Momentum p = γmv is not frame invariant.
*Four* momentum is frame invariant.
6) Then I don't belong to that class of thinkers.

--
Lightarrow

 

[lightarrow]

Hope to be expressed better what I mean

"to have" expressed...

*Four* momentum is frame invariant.

... "is frame invariant as magnitude".

--
Lightarrow

 

[Simple question]

1) Never written "it has no magnetic moment". I've written, it has no magnetic moment "in the z+ direction" and "in the z_ direction" (unless the system is already in the up, or down, eigenstate of magnetic moment, of course).

So are you saying that you choose some random z axis because you know in advance that the magnetic moments of the Ag atoms is orthogonal (not none, not zero) to that specific z direction only ?
That's not how the Ag atom are prepared, they are not in the X direction eigenstate.

2) Yes, the records are changes affecting the device only. *Everything* else is interpretation

This is perfectly fine and rational. I could also adopt such a viewpoint (measurement as beable ? QBism ?).

: both what I wrote about the device affecting the system's property (that is having or not z+ component of magnetic momentum) and the system already having that property before measurement (magnetic moments already z+ and z), and the device "only separating them".

OK, I agree that both cases are equivalent then.
Except my point is that each angle chosen (and measurement taken, if you made them in series), depends on the previous ones. Likewise, the first apparatus has to be aligned with the source output.
The link between those measurement are particle path. You cannot get those "magnetic moment" measurement otherwise. So if something is observed to be conserved, is it the apparatuses that "transfer spin" between themselves then ? How classical macroscopic object could do this ? What about nature in the absence of measuring devices ? Aren't measuring devices made of quantum particles themselves ?

3) Yes, collapse, of course, I just wrote it in a different way, hope it's not necessary to always repeat the same word to express a concept and certainly I didn't mean to express something weird.

So am I correct in thinking that you mean collapse of the measuring device only ?

4) We have photons which polarization state is in the plane orthogonal to the X-Y plane and which intersection with the last one is the straight line y = x, that is the 45º bisector of the first and third quadrant. Said with an analogy/metaphor: Does the vector xi+yj on the plane have "only x or only y components"? Certainly not. In the same way if a polarization state of the photon is at 45º, does the polarizing filter along X axis measures its x component? I would say no, since the subsequent detector register "yes" or "no" photn presence.

I don't understand the "since". How a "pass or not pass" would imply "has not X component" ? Actually the X and Y component are precisely equals. So it has 0.5 chances to pass. How could it be otherwise ? Which other value could it have ? a 1/2 frequency maybe ?
Even trying to adopt your point of view, if is is not based on the X component of the photon, how would a polarizing filter "decide" ?

5) Don't understand your "what". Momentum p = γmv is not frame invariant.
*Four* momentum is frame invariant.

Yes, but my point is that you don't "create" momentum by "changing frame". It is conversed, and all inertial frame agree. So it does not belong or depend-on any "frame"

6) Then I don't belong to that class of thinkers.

OK. But I have a hard time understanding your ontology. Do you have some reference to point me to ? Maybe it is something like Peter Morgan describe in this other thread ?

 

[weirdoguy]

It is conversed, and all inertial frame agree. So it does not belong or depend-on any "frame"

All inertial frames agree that momentum is conserved, but they do not agree on the "value" since it is frame dependent.

 

[lightarrow]

1) So are you saying that you choose some random z axis because you know in advance that the magnetic moments of the Ag atoms is orthogonal (not none, not zero) to that specific z direction only ?
That's not how the Ag atom are prepared, they are not in the X direction eigenstate.

2) OK, I agree that both cases are equivalent then.
Except my point is that each angle chosen (and measurement taken, if you made them in series), depends on the previous ones. Likewise, the first apparatus has to be aligned with the source output.
The link between those measurement are particle path. You cannot get those "magnetic moment" measurement otherwise. So if something is observed to be conserved, is it the apparatuses that "transfer spin" between themselves then ? How classical macroscopic object could do this ? What about nature in the absence of measuring devices ? Aren't measuring devices made of quantum particles themselves ?

3) So am I correct in thinking that you mean collapse of the measuring device only ?

4) I don't understand the "since". How a "pass or not pass" would imply "has not X component" ? Actually the X and Y component are precisely equals. So it has 0.5 chances to pass. How could it be otherwise ? Which other value could it have ? a 1/2 frequency maybe ?
Even trying to adopt your point of view, if is is not based on the X component of the photon, how would a polarizing filter "decide" ?

5) Yes, but my point is that you don't "create" momentum by "changing frame". It is conversed, and all inertial frame agree. So it does not belong or depend-on any "frame".

6) OK. But I have a hard time understanding your ontology. Do you have some reference to point me to ? Maybe it is something like Peter Morgan describe in this other thread ?

1) I know, but to me, the real mystery is (Sakurai's book on QM helped me understand this) when we measure the u component of spin after the system has been prepared in the v+ component orthogonal to u: if the system really has ("really" in the sense of "intrinsically" or in some other sense I can't name because I'm not experienced with terminology) the v+ component of spin, why does the magnet (u oriented) split the beam in two, equally distributed, different beams and, more important, why does subsequent magnets v oriented again, splits again each beam in other two equally distributed, different beams?
My intuition (don't know if it can be called "interpretation") is that the (gradient of) B field u oriented destroys the "v+" property of the quantum system (Ag beam) and creates the "u+" property in the first splitted beam and the "u-" property in the other; the field does not affect this if it's oriented along the same axis of which the system has been prepared.
So in my vision the magnet/field does 3 different things according to the experimental setting and the initial system's state:

a) if the system has been prepared in the v+ state and the magnet's field is along v, we could even avoid making the "measure" because the system's state after passing the magnet will be the same: v+: the apparatus doesn't affect the system's property.

b) if the system has been prepared in the v+ state and the magnet's field is along u, the "measurement" is, actually, a destruction of that v+ property: the apparatus destroyes the property.

c) In the last case, furthermore, the apparatus creates another property on two different, equally distributed, beams: the u+ property in one beam and the u- property in the other. Even if we don't know in which state the system was prepared, or not, before the "measurement", we know it couldn't be an eigenstate of the u observable (that is of the u component of the magnetic moment).

How can the system and the apparatus interact in such a way to give a), b), c)? Don't know.

2) The system's property is real but the measuring apparatus can: do nothing, destroy, create it, according to the situation. So the property doesn't belong on the system only or on the apparatus only, it depends on both, in general.

3) According to Copenhagen interpretation it's the system, but in my vision what is called "collapse" is something a bit more complicated and we should refer to the previous points 1), 2) ("fenomenology"?)

4) What I mean is that the measuring device is quite a rough one because, on a single photon, it doesn't give the value "x", component of the vector xi+yj, but only "yes" or "no". You would say "that's the way this kind of detector work". So the question is: does the system's property depend only on the system itself or in "how a detector works" too?

5) Don't understand. Momentum is frame dependent so, in a sense, you do create momentum (or energy, or velocity or acceleration, or position, or lenght, ...) by changing frame of reference.

6) Don't know if all this has a name, but it probably has (haven't read much about interpretations in literature), I find it difficult to believe I'm the first to think in these terms.

--
Lightarrow

 

[lodbrok]

All inertial frames agree that momentum is conserved, but they do not agree on the "value" since it is frame dependent.

This is an interesting statement, as unpacking it can illuminate the question of measurement and ontology.

Would you say momentum is a property of the system being observed or a property of the "system + observer"? The fact that the "value" varies based on the observer (since different observers may be in different inertial frames) is already a massive hint forcing the issue :
1. If you say it is a property of the system being observed only, then what is observed as different values can't be the same "thing" that is conserved. Then you must have (implicitly or explicitly) in your ontology the idea that there is a conserved "beable" associated with momentum, which manifests itself as different values ("observables") when observed from different inertial frames.
2. But if you say it is a property of the combined "system + observer" only, then, in this case, you do not assume the existence of any underlying "beable" associated with the "observable." This also restricts what you can say about the "system" based on this observed "value." The problem is many who will pick this option (quite reasonably so) go on to discuss and present "value" as though it applied just to the system. This is wrong and leads to more confusion.

Such conceptual clarity is badly needed in the foundations if any significant progress is going to be made.

 

[Simple question]

All inertial frames agree that momentum is conserved, but they do not agree on the "value" since it is frame dependent.

Nor the same frame will agree with its own previous value just by changing units.
Those "values" are not beable/ontologies in any sense, their usefulness is not to be denied, but they are just labels, not true statements about what is real.
The math actually tell us something important, especially if you think symmetries are real, not artifacts of "frames".
So if I take my navel as a frame, I don't change the momentum of a truck heading straight onto me by jumping out of its way. I know it "for real" because it does not require the same change in momentum.