Find your ideal quantum interpretation

[bhobba]

As an experimental physicist, I would say - using Adan Cabello's words: A map of madness

As I have said before - Dirac and possibly Feynman would be proud of you. But some theorists find such questions interesting. Of value? That's a matter of opinion. Still I enjoy the counter argument which is basically - who cares.

Thanks
Bill

 

[A. Neumaier]

So I would say observation by the environment on a system means we know its properties to a high degree of accuracy regardless of if it is actually recorded or not

This is usually called a preparation, not a measurement. If you prepare a spin up state, you know that the system has spin up, whether measured/recorded or not. But if you measure the spin in another direction (neither parallel nor orthogonal to it), you know nothing.

How would the environment achieve the feat of making the properties of a quantum system known to a high degree of accuracy if it is prepared in an unknown state? Decoherence only changes the pure state into a mixture, but does not reduce the uncertainty about the result obtainable by measurement.

 

[akvadrako]

So is mine. And if I just go ahead and follow both answer trees, I end up with the statistical ensemble interpretation and the Nelson stochastic interpretation. So now I have the problem of interpreting what this means: does it mean I have some probability of using one or the other of these interpretations, or does it mean I'm in a superposition of using both?

I'd say if they are completely orthogonal it wouldn't matter much. Otherwise, you should be most convinced where they agree and most unsure where they disagree. [more]

 

[Demystifier]

So is mine. And if I just go ahead and follow both answer trees, I end up with the statistical ensemble interpretation and the Nelson stochastic interpretation. So now I have the problem of interpreting what this means: does it mean I have some probability of using one or the other of these interpretations, or does it mean I'm in a superposition of using both?

In your case, I would recommend to use statistical ensemble for practical purposes and Nelson for the conceptual/philosophic ones. That would be quite close to my own practice, as I use statistical ensemble for practical purposes and Bohm for the conceptual/philosophic ones. Essentially, Nelson is just Bohm with an additional stochastic force on particles.

 

[Demystifier]

I am stuck on the first question.

Why?

 

[martinbn]

Will it's not intended as an "or" choice. I'm saying the "Wavefunction is physically real" is a shorthand for the more explicit expression, it's not an alternative to it, i.e. "The wavefunction is physically real" is a shorthand for "There is a physical object that acts exactly like the wavefunction describes". This is no different from saying "$\textbf{B}(x)$ is real/ontological" in electromagnetism, it's just a shorthand for "The magnetic field exists and behaves as described by the vector field $\textbf{B}(x)$"

Post #66 states things about as succinctly as I can. Take that post, what isn't clear?

This is perfectly clear. But I don't see how saying " the wave function is the only real thing" is a short hand for "there is a physical object described by the wavefunction". It isn't shorter and the meaning is very different. Also it is not specific to MWI.

 

[martinbn]

Why?

Both answers are equally important, I cannot say which one I consider the main.

 

[bhobba]

How would the environment achieve the feat of making the properties of a quantum system known to a high degree of accuracy if it is prepared in an unknown state? Decoherence only changes the pure state into a mixture, but does not reduce the uncertainty about the result obtainable by measurement.

The detail can be found in Schlosshauer and has to do with the radial nature of most interactions. I have posted it before many times. If you are interested I can dig up a previous thread.

Thanks
Bill

 

[DarMM]

This is perfectly clear. But I don't see how saying " the wave function is the only real thing" is a short hand for "there is a physical object described by the wavefunction". It isn't shorter and the meaning is very different. Also it is not specific to MWI.

It'd be standard enough usage in papers on MWI and many papers on interpretations in general. I'm not going to claim one can derive standard phraseology from first principles logically, it's just the type of phrase that's ended up being used.

Also it is short in full for "There is a physical object described by the wavefunction with each component of the wavefunction corresponding to an aspect of that object, furthermore there are no more objects in existence aside from this"

It's certainly shorter than that.

How would you phrase it?

 

[A. Neumaier]

How would the environment achieve the feat of making the properties of a quantum system known to a high degree of accuracy if it is prepared in an unknown state? Decoherence only changes the pure state into a mixture, but does not reduce the uncertainty about the result obtainable by measurement.

The detail can be found in Schlosshauer and has to do with the radial nature of most interactions. I have posted it before many times. If you are interested I can dig up a previous thread.

Please dig it up. As I recall, Schlosshauer does not claim to have a solution for the problem of unique outcomes - which is the only way uncertainty in a superposition is reduced.

 

[DarMM]

Qbism is about the interpretation of QM and, therefore, examines the epistemic foundation of quantum mechanics, placing the subject at the heart of the construction of our knowledge.
/Patrick

Sorry only saw this now. I don't disagree at all, QBism has the subject directly because it takes a De Finetti/Subjective Bayesian view of probability. That's a separate issue to what I was discussing with @Demystifier however.

 

[Demystifier]

Both answers are equally important, I cannot say which one I consider the main.

I understand. But if you force yourself to chose one of the answers, can you then answer the other questions? And if you can, what are the two interpretations (one Copenhagenish and one ontological) that you finally arrive at?

 

[stevendaryl]

So we are back to the beginning. To me it seems meaningless to say that configuration space is real.

Okay, to get an idea about your notion of "real", in General Relativity, is the spacetime manifold "real"? What's an example of something that it is meaningful to say is "real"?

 

[*now*]

Of a and b, I think if a is more concerned about epistemic book keeping and less about extra ontology, then a.

However, regarding the question of the moon vanishing, I don’t think a relational view would agree with a vanishing moon. Anything we have info about like the moon would involve physical regularities, e.g. energy conservation that we have info about too. Despite these problems I think Bhobba’s post is interesting from this view. It could be like asking to extricate an entity from all associated consistent, coherent physical information, and that doesn’t sound like that view.

If “observation” or having information is like frames of reference in relativity possibly these just seem part and parcel.

Probabilities involved with possible physical observational frames of reference would involve physical effects (physically registered effects).

 

[AlexCaledin]

Let us agree, together with Feynman, that we are merely participating in Nature's self-observing!

 

[microsansfil]

That's a separate issue to what I was discussing with @Demystifier however.

Following your remark, I was just trying to point out that QBism personalizes the famous dictum of Asher Peres : Unperformed experiments have no results and thus experience do not "exist" prior to being experienced.

https://arxiv.org/pdf/1311.5253.pdf

The outcome of an experiment is the experience it elicits in an agent. If an agent experiences no outcome, then for that agent there is no outcome. Experiments are not floating in the void, independent of human agency. They are actions taken by an agent to elicit an outcome. And an outcome does not become an outcome until it is experienced by the agent. That experience is the outcome.

Many seem to have forgotten (Or have not yet fully realized this) that any scientific investigation, among other things, begins with our awareness. The "qbism" reminds us in a clear way, for those who manage to become aware of it and recalls the scaffolding that is used in our objectification processes.

https://arxiv.org/pdf/1311.5253.pdf

What is "real" for an agent rests entirely on what that agent experiences, and different agents have different experiences. An agent-dependent reality is constrained by the fact that different agents can communicate their experience to each other, limited only by the extent that personal experience can be expressed in ordinary language. Bob’s verbal representation of his own experience can enter Alice’s, and vice-versa. In this way a common body of reality can be constructed, limited only by the inability of language to represent the full flavor — the “qualia” — of personal experience.

/Patrick

 

[bhobba]

Please dig it up. As I recall, Schlosshauer does not claim to have a solution for the problem of unique outcomes - which is the only way uncertainty in a superposition is reduced.

I will dig it up. You are of course correct - he does not claim that, nor do I, but we will be in a better position to discuss what exactly is being said when it is spelled out. I will get it from the textbook. On reflection that would be a better source than past threads.

Thanks
Bill

 

[vanhees71]

In your case, I would recommend to use statistical ensemble for practical purposes and Nelson for the conceptual/philosophic ones. That would be quite close to my own practice, as I use statistical ensemble for practical purposes and Bohm for the conceptual/philosophic ones. Essentially, Nelson is just Bohm with an additional stochastic force on particles.

Hm, isn't Nelson himself now convinced that the stochastic interpretation is flawed? I'm not sure, where I read something along these lines of arguments...

 

[Demystifier]

Hm, isn't Nelson himself now convinced that the stochastic interpretation is flawed? I'm not sure, where I read something along these lines of arguments...

The Nelson stochastic interpretation has some internal problems (which interpretation doesn't?), but people are working on it. See e.g. https://lanl.arxiv.org/abs/1510.06391

 

[vanhees71]

The Nelson stochastic interpretation has some internal problems (which interpretation doesn't?)

Which internal problems does the minimal statistical interpretation have, despite the fact that some philosophers cannot accept that nature doesn't behave as the wishful thinking from their macroscopic experience based prejudices suggest?

The more I think about it the more I get convinced that the minimal statistical interpretation is all there is to QM. The question, whether or not QM is the last word on the most fundamental theory we can ever discover, is of course an open one.

 

[Demystifier]

Which internal problems does the minimal statistical interpretation have

The minimal statistical interpretation (MSI) is incomplete in the sense that individual measurement outcomes exist, but MSI says almost nothing about them. It talks only about statistics when measurement is repeated many times. The fact that proponents of MSI do not mutually agree whether the Bell theorem implies non-locality (Ballentine thinks that it does, you think that it doesn't) shows that this incompleteness has consequences on conceptual understanding. Of course, this is not of much relevance for practical applications, but the point of interpretations is not to be relevant for practical applications.

 

[stevendaryl]

The minimal statistical interpretation (MSI) is incomplete in the sense that individual measurement outcomes exist, but MSI says almost nothing about them. It talks only about statistics when measurement is repeated many times. The fact that proponents of MSI do not mutually agree whether the Bell theorem implies non-locality (Ballentine thinks that it does, you think that it doesn't) implies this incompleteness has consequences on conceptual understanding. Of course, this is not of much relevance for practical applications, but the point of interpretations is not to be relevant for practical applications.

To me, the issue with the minimal interpretation is that it relies on a distinction between measurements and other interactions. To me, if measurement is definable in terms of more basic interactions, then claims about measurements are either redundant (since they're derivable from claims about the other interactions) or inconsistent. If measurement is not definable in terms of more basic interactions, then it seems to me that the minimal interpretation is incomplete, unless you add a separate theory of measurement.

 

[martinbn]

It'd be standard enough usage in papers on MWI and many papers on interpretations in general. I'm not going to claim one can derive standard phraseology from first principles logically, it's just the type of phrase that's ended up being used.

Also it is short in full for "There is a physical object described by the wavefunction with each component of the wavefunction corresponding to an aspect of that object, furthermore there are no more objects in existence aside from this"

It's certainly shorter than that.

How would you phrase it?

That is perfectly fine. Now you've added the part about the components, that makes it MWI specific. But to me it has a different meaning from "the wave function is the only thing that exists".

 

[martinbn]

I understand. But if you force yourself to chose one of the answers, can you then answer the other questions? And if you can, what are the two interpretations (one Copenhagenish and one ontological) that you finally arrive at?

I get consistent histories and shut up and calculate. But I have interpreted some of the questions in a way that may be different from what is intended.

 

[vanhees71]

The minimal statistical interpretation (MSI) is incomplete in the sense that individual measurement outcomes exist, but MSI says almost nothing about them. It talks only about statistics when measurement is repeated many times. The fact that proponents of MSI do not mutually agree whether the Bell theorem implies non-locality (Ballentine thinks that it does, you think that it doesn't) implies this incompleteness has consequences on conceptual understanding. Of course, this is not of much relevance for practical applications, but the point of interpretations is not to be relevant for practical applications.

Well, that individual measurement outcomes exist is an empirical fact, upon which all our physics is based. Since the "randomness" of these outcomes are also an empirical fact and QT describes the corresponding statistics with astonishing accuracy, I don't see, where QT in the minimal interpretation should be incomplete. Measurements are defined by the apparati constructed to perform them. These devices are constructed using the known physics. Since the oustcomes of measurements are as expected (up to now) there's no additional theory of measurement necessary.

 

[martinbn]

Okay, to get an idea about your notion of "real", in General Relativity, is the spacetime manifold "real"? What's an example of something that it is meaningful to say is "real"?

No, the manifold is not real. The fields (the physical ones, not the mathematical ones) in the theory are real. For example the electromagnetic field, or dust, or fluids ect.

 

[A. Neumaier]

I don't see, where QT in the minimal interpretation should be incomplete.

How does QT in the minimal interpretation describe the state of the solar system?

We only have a single realization of the solar system, which has been prepared once in ancient times.
Hence we cannot apply rules that require a large ensemble of similarly prepared systems.

 

[Demystifier]

I get consistent histories and shut up and calculate. But I have interpreted some of the questions in a way that may be different from what is intended.

Maybe this means that you should not worry about interpretations of those questions. Maybe this means that you should shut up and calculate consistent histories.

 

[A. Neumaier]

has some internal problems (which interpretation doesn't?)

Mine!

 

[Lord Jestocost]

Which internal problems does the minimal statistical interpretation have, despite...

Stephen L. Adler remarks in “Quantum Theory as an Emergent Phenomenon”:

“There are two conventional ways to try to avoid the measurement dilemma just stated. The first is to assert that quantum mechanics has only a statistical interpretation, and should only be applied to describe the statistical properties of multiple repetitions of an experiment, but not to any individual run. However, with the advent of our ability to trap individual particles for long periods, and to manipulate their quantum states (e.g., the particle emerging from the "up" beam in Fig. l d could be run into a trap, and manipulated there), this interpretation of quantum mechanics becomes dubious.”

 

[Lord Jestocost]

@Demystifier

To avoid any "bias" regarding the "existence of the moon", there are two questions which should be asked:

- Is the moon there when nobody looks?

- Is the moon there even when somebody does look?

 

[stevendaryl]

No, the manifold is not real. The fields (the physical ones, not the mathematical ones) in the theory are real. For example the electromagnetic field, or dust, or fluids ect.

Well, I don't understand the criterion for considering something real or not from that. I would say that the spacetime manifold is as real as fields are.

 

[stevendaryl]

Stephen L. Adler remarks in “Quantum Theory as an Emergent Phenomenon”:

“There are two conventional ways to try to avoid the measurement dilemma just stated. The first is to assert that quantum mechanics has only a statistical interpretation, and should only be applied to describe the statistical properties of multiple repetitions of an experiment, but not to any individual run. However, with the advent of our ability to trap individual particles for long periods, and to manipulate their quantum states (e.g., the particle emerging from the "up" beam in Fig. l d could be run into a trap, and manipulated there), this interpretation of quantum mechanics becomes dubious.”

I don't think that asserting that "quantum mechanics has only a statistic interpretation" helps to avoid the measurement problem. The statistics predicted by quantum mechanics are statistics for measurement results.

 

[Demystifier]

@Demystifier

To avoid any "bias" regarding the "existence of the moon", there are two questions which should be asked:

- Is the moon there when nobody looks?

- Is the moon there even when somebody does look?

If the answer to the second question is "no", what would be the corresponding interpretation of QM?

 

[Lord Jestocost]

If the answer to the second question is "no", what would be the corresponding interpretation of QM?

Let me answer using Arthur Stanley Eddington’s words:
“It is difficult for the matter-of-fact physicist to accept the view that the substratum of everything is of mental character. But no one can deny that mind is the first and most direct thing in our experience, and all else is remote inference ⎯ inference either intuitive or deliberate.”