A A stronger proof of nonlocality, or what?

[PeterDonis]

An experiment has been performed in which a true measuring apparatus is replaced with a single qubit, obviously because a single qubit is much easier to manipulate in a way needed for the experiment.

And just as obviously, makes the experiment irrelevant to the question such experiments are supposed to address, since you can't make a measuring apparatus out of a single qubit.

 

[Fra]

because actual realization of such experiments, involving fine manipulations of quantum properties of the measuring apparatus, would be terribly difficult.

If the difficulty is due to the requirements of information processing capacity, and at some point it simply exceeds what we have at hand, would we still call it just a difficulty, or would be call it not possible in principle?

/Fredrik

 

[Demystifier]

If the difficulty is due to the requirements of information processing capacity, and at some point it simply exceeds what we have at hand, would we still call it just a difficulty, or would be call it not possible in principle?

To say what is possible or impossible in principle, one must first specify - the principle. The principle is a theoretical concept, not an experimental one. The formulation of a principle may be guided by experiments, but it becomes a principle only when we give it a theoretical formulation, either as an axiom of a given theory, or something derived from more fundamental axioms. But our theories, and hence the principles, change and evolve as our knowledge develops. For example, consider the 2nd law of thermodynamics. According to the thermodynamic theory (as formulated before the Boltzmann's statistical mechanics), it is impossible in principle to violate the 2nd law. But according to statistical mechanics, it's possible in principle, but very difficult in practice.

 

[Fra]

To say what is possible or impossible in principle, one must first specify - the principle. The principle is a theoretical concept, not an experimental one. The formulation of a principle may be guided by experiments, but it becomes a principle only when we give it a theoretical formulation, either as an axiom of a given theory, or something derived from more fundamental axioms. But our theories, and hence the principles, change and evolve as our knowledge develops. For example, consider the 2nd law of thermodynamics. According to the thermodynamic theory (as formulated before the Boltzmann's statistical mechanics), it is impossible in principle to violate the 2nd law. But according to statistical mechanics, it's possible in principle, but very difficult in practice.

Yes, the principle I had in mind was what I take implicit to the whole standard paradigm of QM: That inferences are made from experiments in the form of statistics of preparation procedures and detections. Somehow, I think it seems fair to say that it's how it's done, regardless of "interpretations"? Modulo observer equivalence transformations, all observers must be able to agree on the statistics, which is why some says it's on the "classical side".

For example, an experiment with a measurement device that isn't as reliable as "classical record" isn't just difficult, I think it doesn't qualify as a measurement, and thus invalid to use in the QM paradigm?

I agree this is a big problem. But I don't think the problem can be analyzed within QM itself, as it entertains for good reasons "measurements" that should make sense, but are somehow generalisations of the more constrained "quantum measurements", so we can't handle them as per the QM paradigm.

The question then was, is it possible in principle to infer the mentioned problems of QM itself, using its own "inference system" and experimental protocol (without bending the presumed rules)?

/Fredrik

 

[Demystifier]

But I don't think the problem can be analyzed within QM itself, as it entertains for good reasons "measurements" that should make sense, but are somehow generalisations of the more constrained "quantum measurements", so we can't handle them as per the QM paradigm.

The question then was, is it possible in principle to infer the mentioned problems of QM itself, using its own "inference system" and experimental protocol (without bending the presumed rules)?

Is the first quote your answer to your question in the second quote?

 

[Fra]

Is the first quote your answer to your question in the second quote?

Yes. Its my strong hunch. I havent contempled ny proofs though.

/Fredrik

 

[Fra]

This was highlighted earlier in the thread...

1. When someone observes an event happening, it really happened.

To me this is essentially what it means for an observer to be in the "classical world" - where "real" is define as whatever the consensus is among observers, via equivalence transformations.

Without this, I agree as hinted by others that QM paradigm makes no sense, as QM is built on this solid ground.

If we widen our views however, I would of course expect the QM to break down at some point anyway, so this assumption is pretty much the first I would do away with from an agent-centered stance. After all, as I mentioned before, there is a difference between the principle of "no preferred observer", (which seems easy to accept as anybodys views is as right asn anyones elses) and the much stronger "all observers are equivalent". The former does not exclude disagreements, and there is thus perhaps no solid ground? And therefore QM may have limited validity only to the extent that the classical backround IS stable enough, and the more general framework to describe this in, is still missing. This is what I meant with that, in the paradigm of QM, I think (1) must hold. IF we relax it, we leave the QM paradigm?

/Fredrik

 

[Demystifier]

To me this is essentially what it means for an observer to be in the "classical world" - where "real" is define as whatever the consensus is among observers, via equivalence transformations.

I think that reality has nothing to do with classicality. For instance, dreams and hallucinations, which are not real, are equally classical.

 

[martinbn]

I think that reality has nothing to do with classicality. For instance, dreams and hallucinations, which are not real, are equally classical.

Reality of position is related to classicality. But in a non-classical theory why should position be real? Or more generaly why should there be an observable with a classical analog/limit which is real?

 

[Demystifier]

Reality of position is related to classicality. But in a non-classical theory why should position be real? Or more generaly why should there be an observable with a classical analog/limit which is real?

I believe I answered such questions in my "Bohmian mechanics for instrumentalists".

 

[martinbn]

I believe I answered such questions in my "Bohmian mechanics for instrumentalists".

Yes, but my impression is that you argue that there has to be something real that is classical like position. Then you cannot say that reality and classicality have nothing to do with each other.

 

[Fra]

I think that reality has nothing to do with classicality. For instance, dreams and hallucinations, which are not real, are equally classical.

It seems we get into discussions on definition of real. Then what does " classical mean"? classical mechanics?

Id say my dreams are real experiences realized by the physics of my brain, but they often violate classical mechanics. So in what sense are dreams classical?

/Fredrik

 

[Fra]

Trying to calibrate terms...

in my "Bohmian mechanics for instrumentalists".

Do you take the "non-perceptible" items that are "thinking tools" and provides explanatory value within a theoey as what is real?

/Fredrik

 

[Demystifier]

Yes, but my impression is that you argue that there has to be something real that is classical like position. Then you cannot say that reality and classicality have nothing to do with each other.

Impression is the key word.

 

[Demystifier]

Do you take the "non-perceptible" items that are "thinking tools" and provides explanatory value within a theoey

Yes.

as what is real?

Not necessarily.

 

[Demystifier]

It seems we get into discussions on definition of real. Then what does " classical mean"? classical mechanics?

Id say my dreams are real experiences realized by the physics of my brain, but they often violate classical mechanics. So in what sense are dreams classical?

By classical I mean not quantum. To explain dreams in terms of physical processes in the brain, one does not need quantum physics.

 

[Fra]

Are your solipsist HV "classical", but "not real" by that terminology?

And not observable(in QM terminology)?

/Fredrik

 

[Morbert]

The one referred to in the first post of this thread. It discusses a thought experiment of the Wigner-friend type, which manipulates the quantum state of the measuring apparatus and concludes that, if quantum mechanics is applicable to the measuring apparatus as to any other quantum object, then the minimal purely instrumental interpretation of QM is wrong. But the actual experiment has not been performed(*), and probably will not be in a near future, so a pure instrumentalist, like you, does not need to worry.

(*) An experiment has been performed in which a true measuring apparatus is replaced with a single qubit, obviously because a single qubit is much easier to manipulate in a way needed for the experiment.

The implication in bold is too strong for a takedown of instrumentalism, as instrumentalists can readily describe a measurement apparatus quantum mechanically. A better statement would be something like: If measurement data are not sufficiently classical, then the purely instrumental interpretation of QM is wrong.

I.e. We can reject the notion that there are superobservers, but still be fine with describing the measurement apparatus quantum mechanically. QM descriptions don't entail superobservers, and it's the superobservers that would cause an issue for instrumentalists.

 

[Demystifier]

Are your solipsist HV "classical", but "not real" by that terminology?

Just the opposite, it is quantum and real, in the same sense in which particle trajectories in Bohmian interpretation are quantum and real.

And not observable(in QM terminology)?

It's not an observable, in the sense that it is not described by an operator in the (rigged) Hilbert space, if that's what you meant.

 

[Fra]

Just the opposite, it is quantum and real, in the same sense in which particle trajectories in Bohmian interpretation are quantum and real.

Are you thus conceptually "ok" with considering something "real" that different observers fail to agree upon, because its "solipsistic" in nature?

/Fredrik

 

[Fra]

If the presumed map of reality "explains" why perceptables like detctor clicks happen?

Then what motivates/infers this map of reality in the first place? Isnt that inferred FROM detector clicks? thus arent these indistinguiahable events quite primary? Rather begging to be explained in terms of something else?

What is it we should explain, and in terms of what? For me the heart of the empirical meaauremnt thery is that the map should be "constructable" from pereceptables witha minimum of ad hoc structures

/Fredrik

 

[Demystifier]

Are you thus conceptually "ok" with considering something "real" that different observers fail to agree upon, because its "solipsistic" in nature?

Yes. For example, if I dream that I can fly, then my ability to fly is not real, but the fact that I have this dream is real.

 

[Demystifier]

If the presumed map of reality "explains" why perceptables like detctor clicks happen?

Then what motivates/infers this map of reality in the first place? Isnt that inferred FROM detector clicks? thus arent these indistinguiahable events quite primary? Rather begging to be explained in terms of something else?

What is it we should explain, and in terms of what? For me the heart of the empirical meaauremnt thery is that the map should be "constructable" from perceptables with a minimum of ad hoc structures

In principle, I could agree. But the history of physics teaches us that non-perceptibles can have a strong explanatory power. For example, Boltzmann explained thermodynamics in terms of non-percetible atoms. Denying atoms by Mach made sense at that time, but denying atoms today would seem too radical.

 

[vanhees71]

Just the opposite, it is quantum and real, in the same sense in which particle trajectories in Bohmian interpretation are quantum and real.It's not an observable, in the sense that it is not described by an operator in the (rigged) Hilbert space, if that's what you meant.

Now we are back at this endless debate, what's "real". You have to define, what you mean by the term "realism", so that one can know what you are talking about. Obviously, since Bohmian trajectories are not observable, for you something non-observable can be real. That's a very strange notion of "real" for me ;-).

 

[gentzen]

Now we are back at this endless debate, what's "real". You have to define, what you mean by the term "realism", so that one can know what you are talking about. Obviously, since Bohmian trajectories are not observable, for you something non-observable can be real. That's a very strange notion of "real" for me ;-).

No, we are not, because Demystifier just clarified that his "solipsist HV" are just as real or unreal as Bohmian trajectories. And saying that Bohmian trajectories are real is independent of that endless debate too, because that is also just a clarification on the level of the theory, similar to saying that electric fields are real, but vector potentials are not.

 

[Demystifier]

Now we are back at this endless debate, what's "real". You have to define, what you mean by the term "realism", so that one can know what you are talking about. Obviously, since Bohmian trajectories are not observable, for you something non-observable can be real. That's a very strange notion of "real" for me ;-).

In realistic interpretations, the word "real" (or ontic) is a primitive notion, its meaning is taken intuitively and cannot be precisely defined in terms of something more elementary.

Likewise, in instrumental interpretations, the word "instrument" (or measuring apparatus) is a primitive notion, its meaning is taken intuitively and cannot be precisely defined in terms of something more elementary.

Some physicists, like me, don't like the idea that measuring apparatus is primitive, so they replace it with another primitive notion that seems more acceptable to them. Different interpretations take different concepts as primitive. It's a matter of personal preference which concept makes more sense as a primitive concept that will not be defined precisely.

It is logically impossible to completely remove primitive concepts. Any definition of a concept uses some words, which one may want to define in terms or other words, which one may want to define in terms of other other words, which ..., but eventually this has to stop somewhere and leave some words undefined. The words that are left undefined are called primitive.

 

[Fra]

In principle, I could agree. But the history of physics teaches us that non-perceptibles can have a strong explanatory power. For example, Boltzmann explained thermodynamics in terms of non-percetible atoms. Denying atoms by Mach made sense at that time, but denying atoms today would seem too radical.

The flow I entertain is

(1) perceptibles -> abduction of best explanation = non-perceptibles ~ agents map of reality

(2) The map of reality guesses the future has as a guiding value to the agents actions. So the agents follows the map... wether right or wrong. This means noone denies the map, or questions the map as its already by construction optimal. A variant of your "non-perceptibles have strong explanatory power. It explains litteraly at least the agenta actions. To thate tent i can agree.

The question is... what is the process by which the input evolves the map. This for me the heart of the matter.how the map evolves in reaponse to percetiples. And that different have slightly different maps are not one bit strange. Their maps are "real" in your sense..

So of the bohmian picture of HV and whatever deteemines their evolution is to be associated to the observers "map" then its getting in harmony with how i view the agents microstructure [which encodes the"map"]

/Fredrik