I Find your ideal quantum interpretation

[Demystifier]

Find the interpretation of QM that best suits your personality. You don't need to think much about quantum interpretations to decide which one is the best for you. Just choose one of the offered answers to a couple of questions on the graph. You don't need to think much about the offered answers, just choose the one that feels right intuitively, in your guts.

 

[A. Neumaier]

Find the interpretation of QM that best suits your personality. You don't need to think much about quantum interpretations to decide which one is the best for you. Just choose one of the offered answers to a couple of questions. You don't need to think much about the offered answers, just choose the one that feels right intuitively, in your guts.

You decision tree is not good: I ended up with Bohmian mechanics, though I find this a very poor interpretation. My thermal interpretation is far better! (The state is not in Hilbert space but a density operator operating on it.)

 

[Demystifier]

Well, I couldn't put all the existing interpretations to the graph, so I put only the most popular ones.

If you had to choose one from the graph, which one would that be?

 

[A. Neumaier]

Well, I couldn't put all the existing interpretations to the graph, so I put only the most popular ones.

If you had to choose one from the graph, which one would that be?

Neither; they are all heavily deficient, though in different ways. That's why the interpretation problem is still unsettled.

How did you decide on popularity?

 

[Demystifier]

How did you decide on popularity?

By experience (which I have a lot on this matter, but I may be biased).

 

[A. Neumaier]

By experience (which I have a lot on this matter, but I may be biased).

Please add to your figure your subjective probabilities of popularity of each case (nonnegative, sum to 1, as you had stipulated)! For example, I wonder why GRW/Penrose is in...

 

[DennisN]

Find the interpretation of QM that best suits your personality.

Wow, it worked for me . I ended up at the statistical ensemble interpretation, which I do feel closest to. But nevertheless I'm trying to keep my mind open regarding interpretations.

 

[Spinnor]

I am in a superposition of the statistical ensemble interpretation and the Nelson stochastic interpretation. I think the choices in the first box are both equally important. I wanted to end up in Bohmian mechanics but I don't think the world is deterministic due to some intrinsic randomness that we will never be able to know. I would like to think a photon "really" goes via one path or another in an interferometer, the energy of a photon is "localized" and remains so until it is annihilated.

Thanks.

 

[microsansfil]

Find the interpretation of QM that best suits your personality :

if I'm interested in epistemological questions: Qbims
On the other hand, if I'm interested in physics issues: "shut up and calculated",but not for the reason of the decision tree. Just for the interest of understanding the modeling of a physical phenomenon through the language of mathematics.

Now, is "shut up and calculated" an interpretation of Quantum Mechanics !?

I would have put "Is the Moon there when conscious being observe it ?" before 'Is the Moon there when nothing measure it ?" because for us human beings “Lived experience is where we start from and where all must link back to, like a guiding thread”. Accepting the fact that there is something rather than nothing, this does not mean that this something would be such as our consciences present it to us (e.g the Moon).

/Patrick

 

[StevieTNZ]

Ewww, I got 'shut up and calculate'. That is FAR from the interpretation I adhere to.

 

[AlexCaledin]

Shut Up And Calculate is in the very center because the Moon question can be made meaningless only by means of a very meaningful philosophy!

 

[DarMM]

Consistent Histories is usually presented as a Copenhagen style interpretation, explicitly so in the books of Griffiths and Omnès. Also in both it and QBism the Moon is there when nobody looks.

I'd say at the Moon question QBism, Statistical Ensemble, Consistent Histories and Neo-Copenhagen views (e.g. Bub, Healey, Brukner) all branch off from Relational. You'd then need a set of precise questions to separate them.

I think the first one to ask would be:
"Do Probability 1 events represent a sure occurrence?" or something similar like "Given a set of experimental conditions is there a single rational probability assignment?" or even more briefly "Are you a Subjective Bayesian?". That would separate QBism from the others, with QBism being a "No" answer.

EDIT: I actually think "Are experimental outcomes objective facts?" is a better selector for QBism

After that a similar question asking whether you hold a Frequentist view of probability will pull out the Statistical Ensemble view.

Finally "Can Classical Mechanics be derived from QM?" with "No" giving Neo-Copenhagen and "Yes" giving Consistent Histories.

I'm still holding out for my "I wish I could shut up and calculate" interpretation swinging the hearts of the physics community.

 

[julcab12]

If you follow along the path of clean QM formalism. I would say you would likely end up with Many World on face value. Simply because it is simple. The ontology is simple: all that exists is the wavefunction. The dynamics are simple: the wavefunction obeys unitary evolution according to the Schrodinger equation. Measurement problem is simple: decoherence selects a basis, and the relative state gives you definiteness; both of these are natural quantum processes and don't have to be added in. The derivation of the Born rule for probability is -- well maybe not simple -- but it is elegant: proceeding in analogy to classical Savage decision theory. It is an entirely local theory. It generalizes straightforwardly to quantum field theories... Ok I get it. But my personal bias led me to Relational bec of my GR mentality-- Mirages and Gravitational Effect produces illusions.

 

[DarMM]

Measurement problem is simple: decoherence selects a basis, and the relative state gives you definiteness; both of these are natural quantum processes and don't have to be added in. The derivation of the Born rule for probability is -- well maybe not simple -- but it is elegant: proceeding in analogy to classical Savage decision theory. It is an entirely local theory

It really isn't that simple, Wallace's proof is a bit odd defining rationality as almost equivalent to thinking you live in a single world and having a bunch of strange, almost self-contradictory hypotheses about the set of "Quantum Actions" such as irreversibility. This is ignoring the issue that even if it all panned out it's circular. He assumes a branching structure for the proof to work, but branching requires decoherence which requires the Born rule which his proof is attempting to demonstrate, so it's quite circular.

Also as for the "locality" of Many-Worlds, I've never seen a convincing demonstration of this. Even Many-Worlds advocates don't agree on this. Wallace says it is nonlocal, Deutsch says it is local, but like many I don't accept Deutsch's "proof" of this. @Demystifier uses a phrase "alocal" which seems closer to what Many-Worlds is like.

 

[vanhees71]

Well, I ended in two steps at the statistical ensemble interpretation. That's not a big surprise ;-)).

 

[julcab12]

It really isn't that simple, Wallace's proof is a bit odd defining rationality as almost equivalent to thinking you live in a single world and having a bunch of strange, almost self-contradictory hypotheses about the set of "Quantum Actions" such as irreversibility. This is ignoring the issue that even if it all panned out it's circular. He assumes a branching structure for the proof to work, but branching requires decoherence which requires the Born rule which his proof is attempting to demonstrate, so it's quite circular.

That's the reason i say face value, Outside of what is known--Ignoring any philosophical implication(For now). I shouldn't have said "end up". Its the nearest conjecture applying our known contemporary mathematics or dear within the standard formalism of quantum mechanics.

 

[Demystifier]

Also in both it and QBism the Moon is there when nobody looks.

It depends on which QBist do you ask. Mermin is a QBist that says that the Moon is not there when nobody looks. Fuchs sometimes says that it is and sometimes (especially when defends locality) that it isn't.

 

[DarMM]

It depends on which QBist do you ask. Mermin is a QBist that says that the Moon is not there when nobody looks. Fuchs sometimes says that it is and sometimes (especially when defends locality) that it isn't.

Do you have a link? As that seems different from what Fuchs says in most of what I've read.

As far as I've seen Fuchs says there is an Moon when nobody looks, it just isn't fully mathematically comprehensible (like all things in his view).

 

[Demystifier]

Ewww, I got 'shut up and calculate'. That is FAR from the interpretation I adhere to.

So what's the interpretation you adhere to?

 

[Demystifier]

Consistent Histories is usually presented as a Copenhagen style interpretation

Perhaps, but it is more ontological than any other Copenhagen style interpretation.

 

[Demystifier]

Do you have a link? As that seems different from what Fuchs says in most of what I've read.

https://www.quantamagazine.org/quantum-bayesianism-explained-by-its-founder-20150604/

"My fellow QBists and I instead think that what Bell’s theorem really indicates is that the outcomes of measurements are experiences, not revelations of something that’s already there."

 

[DarMM]

Perhaps, but it is more ontological than any other Copenhagen style interpretation.

Genuinely I don't see it as too different from Bub, Haag, Brukner and Healey in how much ontology it gives, at least from Griffith's and Omnès's books. Omnès for example says Quantum Mechanics doesn't directly model the world as it is, he also describes it as simply an extended form of Copenhagen. I think the real difference between it and other Neo-Copenhagen views is that it supposes Classical Mechanics can be derived from QM rather than that it is more ontological.

 

[DennisN]

Wow, it worked for me . I ended up at the statistical ensemble interpretation, which I do feel closest to. But nevertheless I'm trying to keep my mind open regarding interpretations.

I tried the ontological branch too, but interestingly I found it very hard to answer the questions;

Is the world completely described by the state in the Hilbert space?
Here I would probably say "no", since I feel answering "yes" would feel a bit like hubris .

Is the world fundamentally deterministic?
This question I find very hard to answer. Very hard. Because on the one hand the physical world very much appear to follow the rules of causes and effects, but on the other hand we are still stuck with this randomness in QM. But if I really force myself to answer, I'll probably answer "yes", which would make me end up at Bohmian mechanics.

 

[A. Neumaier]

It depends on which QBist do you ask. Mermin is a QBist that says that the Moon is not there when nobody looks. Fuchs sometimes says that it is and sometimes (especially when defends locality) that it isn't.

I guess to handle that you need to draw a quantum picture, with an irreducible uncertainty about which interpretation belongs where!

 

[DarMM]

https://www.quantamagazine.org/quantum-bayesianism-explained-by-its-founder-20150604/

"My fellow QBists and I instead think that what Bell’s theorem really indicates is that the outcomes of measurements are experiences, not revelations of something that’s already there."

I don't think that's saying there's no external world or that things aren't there when not observed, it's just the standard "measurement creates measurement outcomes" you have in Copenhagen views like Haag's, i.e. the measurement results don't follow predictably from something prior they're a creation of the measurement or Peres's "Unperformed experiments have no results".

I think this paper is fairly clear on laying out that there is an external world out there in QBism:
https://arxiv.org/abs/1601.04360

It's just that world has non-deteministic interactions, i.e. some interactions between the Moon and my equipment are purely associated with that interaction event and not determined prior to it.

 

[Demystifier]

I don't think that's saying there's no external world or that things aren't there when not observed

I think they are saying that such things (which are there when not observed) are not physical. Assuming that the Moon is physical, it follows that the Moon is not there when not observed.

 

[A. Neumaier]

I think they are saying that such things (which are there when not observed) are not physical. Assuming that the Moon is physical, it follows that the Moon is not there when not observed.

So in their interpretation, the Moon is physical when observed, and nonphysical otherwise?

 

[DarMM]

I think they are saying that such things (which are there when not observed) are not physical. Assuming that the Moon is physical, it follows that the Moon is not there when not observed.

I guess all I can say is from reading their papers I disagree, Fuchs explicitly says that the view is not instrumentalist, i.e. he disagrees that only that which is observed is real, see this talk:

See around 16:20 for comments on external reality and around 30:10 for a clearer statement of the view of measurements. They simply think that interactions provoke events and values that are entirely "new" and don't follow directly from the previous state of objects, not that nothing exists outside measurement or is unphysical.

This video is a clear rejection of instrumentalism by Fuchs:


My own issue with QBism is I don't think that if one is Copenhagenist¹ that one is compelled to a perspectival view as of yet, i.e. that measurement outcomes aren't objective. This is actually in light of the thread with you and @atyy on the Frauchiger-Renner paper.

¹Copenhagenist meaning QM is not representational of nature, it only discusses measurement outcome statistics or similar.

 

[DarMM]

So in their interpretation, the Moon is physical when observed, and nonphysical otherwise?

As I above I would say no. From my reading of their papers the Moon is always physical, just that the results of certain interactions with the Moon don't follow from the preceding state of the world.

 

[vanhees71]

It depends on which QBist do you ask. Mermin is a QBist that says that the Moon is not there when nobody looks. Fuchs sometimes says that it is and sometimes (especially when defends locality) that it isn't.

It's utter nonsense. Already the conservation laws prevent the moon from vanishing when nobody looks at it. This is really superfluous philosophical gibberish!

 

[DarMM]

It's utter nonsense. Already the conservation laws prevent the moon from vanishing when nobody looks at it. This is really superfluous philosophical gibberish!

I don't think that's what they say as I mentioned above, just that certain interactions results don't pre-exist in the sense of being determined from the prior state. It isn't even a particularly unique element of the interpretation, other Copenhagen views would say similar things.

 

[Demystifier]

Already the conservation laws prevent the moon from vanishing when nobody looks at it.

Unless the conservation laws refer only to the observed phenomena.

 

[Demystifier]

just that certain interactions results don't pre-exist in the sense of being determined from the prior state.

Then I don't understand what QBist's say about the following. Consider an EPR pair. Suppose that Alice measures one member of the pair at time $t_{\rm meas}$ (in the laboratory frame) and Bob measures the other member of the pair at the same time $t_{\rm meas}$. Latter Charlie at time $t_{\rm comp}>t_{\rm meas}$ compares the results of Alice and Bob and finds out that their results are correlated. At the time $t_{\rm meas}$ Alice and Bob know their measurement results, but they don't know that their results are correlated. Are the results correlated already at time $t_{\rm meas}$? I think the QBists insist that they are not correlated already at $t_{\rm meas}$, which is how they save locality.

 

[DarMM]

Then I don't understand what QBist's say about the following. Consider an EPR pair. Suppose that Alice measures one member of the pair at time $t_{\rm meas}$ (in the laboratory frame) and Bob measures the other member of the pair at the same time $t_{\rm meas}$. Latter Charlie at time $t_{\rm comp}>t_{\rm meas}$ compares the results of Alice and Bob and finds out that their results are correlated. At the time $t_{\rm meas}$ Alice and Bob know their measurement results, but they don't know that their results are correlated. Are the results correlated already at time $t_{\rm meas}$? I think the QBists insist that they are not correlated already at $t_{\rm meas}$, which is how they save locality.

Well Alice and Bob would assign a state that models the particles as being correlated or not and then afterward look at the statistics when they compare them, at which point they'd discover whether that is the correct state to be using for particles produced in this manner or not via De Finetti's theorem. QBism uses De Finetti's view of probability theory, i.e. Subjective Bayesianism. I won't go into this too much as their view in this regard isn't really much beyond the Subjective Bayesian view of correlations in completely classical cases and it'll be hard to describe Subjective Bayesianism and QBism in one go.

How they save locality is in a way unrelated to this, but is basically the same as other views that see the core¹ of QM as little more than an extension of probability theory. That is the outcomes pairs don't exist on the same sample space, so there is no requirement for consistency with a counterfactual. If you measure angles $a,c$ in a Bell experiment there is no need to be consistent with counterfactual outcomes associated with separate angles $b,d$ and hence the expectation value $E(a,c)$ is less constrained than in the Classical case. There simply is no value for $b,d$ as they don't arise in that experimental context. This would be shared among QBism, Healey, many Neo-Copenhagen views, Consistent Histories, @RUTA 's acausal view and perhaps the Ensemble view, maybe @bhobba or @vanhees71 can say more.

¹ By the core of QM I mean the basic machinery of Hilbert Spaces and Operators, one can view this as purely an extension of probability without all of QM being so.

 

[AlexCaledin]

Consistent Histories is usually presented as a Copenhagen style interpretation, explicitly so in the books of Griffiths and Omnès. Also in both it and QBism the Moon is there when nobody looks.

Griffiths ends his book with "...quantum theory indicates that the nature of this independent reality is in some respects quite different from what was earlier thought to be the case."

 

[bhobba]

It's utter nonsense. Already the conservation laws prevent the moon from vanishing when nobody looks at it. This is really superfluous philosophical gibberish!

Indeed. It's caused by not being careful about what you mean by observation. The moon is observed all the time by the environment so is never not observed.

Thanks
Bill

 

[bhobba]

Griffiths ends his book with "...quantum theory indicates that the nature of this independent reality is in some respects quite different from what was earlier thought to be the case."

Well probably - but things are not quite as simple as a quote like that would indicate:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Note the above just uses the formalism of QM - no interpretation. You can take questions like that a long way without an actual interpretation. Maybe, just maybe, when all the issues of the above are sorted out we will not really need an interpretation other than something minimal like the Ensemble. Fingers crossed.

Thanks
Bill

 

[A. Neumaier]

The moon is observed all the time by the environment so is never not observed.

This is a quite nonstandard view. What then do you call an observation?

 

[bhobba]

This is a quite nonstandard view. What then do you call an observation?

An example would be a dust particle. A few stray photons from the CBMR is enough to give the dust particle an exact position. And since it's bombarded all the time by such the wave-packet will not spread. I consider the photons an observer.

Thanks
Bill

 

[A. Neumaier]

I consider the photons an observer.

Where are its observation records?

 

[DarMM]

Well probably - but things are not quite as simple as a quote like that would indicate:
https://www.sciencenews.org/blog/context/gell-mann-hartle-spin-quantum-narrative-about-reality

Note the above just uses the formalism of QM - no interpretation. You can take questions like that a long way without an actual interpretation. Maybe, just maybe, when all the issues of the above are sorted out we will not really need an interpretation other than something minimal like the Ensemble. Fingers crossed.

Thanks
Bill

I always found this an interesting view, in some ways you can't say much else if you go Copenhagen/Ensemble or any of the other non-representational views. QM doesn't talk about the microscopic world as it is, only its statistics, but you can prove in some regimes those statistics become/are compatible with Kolmogorov probability and thus in that regime you're fine to think about objects with comprehensible properties.

It's like "The world is fundamentally ineffable, but you can track when it becomes effable". Perhaps there is nothing more than this (combined with ones favorite view on probabilities) as you say.

 

[Lord Jestocost]

Just choose one of the offered answers to a couple of questions on the graph.

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

 

[martinbn]

I am stuck on the first question.

The ontology is simple: all that exists is the wavefunction.

To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

 

[DarMM]

To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

I think it's just shorthand for the wavefunction represents an actual "field" or "fluid" rather than representing the observer's knowledge. Like how $\textbf{B}(x)$ is meant to represent the Magnetic field in Maxwellian electromagnetism.

 

[martinbn]

I think it's just shorthand for the wavefunction represents an actual "field" or "fluid" rather than representing the observer's knowledge. Like how $\textbf{B}(x)$ is meant to represent the Magnetic field in Maxwellian electromagnetism.

But if you have more than one particle, this doesn't work.

 

[julcab12]

I am stuck on the first question.
To me this makes absolutely no sense. The verb exist cannot be applied to the wavefunction.

I'm(They) referring to the wavefunction treated as a classical field (i.e. a field that actually exists, despite being complex valued and of indefinite dimension) which obeys causal, local, relativistic laws and so never collapses. In the purest form, the universal wavefunction encodes a surfeit of splitting timelines, one for each possible history. No filler just a straight on "take something at face value" but that is a natural direction given of what we have. Whether it is true, intuitive or not. It's an honest approach. But for me, I'm a bit squeamish. It would be funny if interpreting it like Einstien ring or any extended images.

 

[DarMM]

But if you have more than one particle, this doesn't work.

How so? Are you referring to the wave function being a function on configuration space?

 

[George Jones]

I am stuck on the first question.

I, too, am stuck on the first question, but possibly for a different reason.

My answer to the first question is "a) and b)."

 

[Mentz114]

If you follow along the path of clean QM formalism. I would say you would likely end up with Many World on face value. Simply because it is simple. The ontology is simple: all that exists is the wavefunction. The dynamics are simple: the wavefunction obeys unitary evolution according to the Schrodinger equation. Measurement problem is simple: decoherence selects a basis, and the relative state gives you definiteness; both of these are natural quantum processes and don't have to be added in. The derivation of the Born rule for probability is -- well maybe not simple -- but it is elegant: proceeding in analogy to classical Savage decision theory. It is an entirely local theory. It generalizes straightforwardly to quantum field theories... Ok I get it. But my personal bias led me to Relational bec of my GR mentality-- Mirages and Gravitational Effect produces illusions.

Probability (nor amplitude) is not stuff. How can the universe be made of something that is not energy/matter or anything detectable ?

 

[julcab12]

Probability (nor amplitude) is not stuff. How can the universe be made of something that is not energy/matter or anything detectable ?

Please read post 46.