QM & Consciousness: Has Theory Been Disproven?

[maline]

There is a place that's different - just after decoherence

When you say it's "different", do you mean in an ontological sense, or just in the practical sense- that that's the point beyond which we can forget about interference effects?

 

[bhobba]

When you say it's "different", do you mean in an ontological sense, or just in the practical sense- that that's the point beyond which we can forget about interference effects?

I mean it in the sense that just after decoherence is a defined point in time. That was the issue that worried Von-Neumann. The only place that was different is the conciousness of a conscious observer that why he introduced the concept - we now know different.

Thanks
Bill

 

[Fredrik]

I think what all these replies assume is that the measurement problem has at least one solution, ie. Bohmian Mechanics or MWI can be considered "consensus" quantum mechanics.

My view on the "measurement problem" is that it's partially answered by decoherence calculations, and that the rest of it consists of misguided expectations about what a theory is supposed to do.

As long as the measurement problem has not been solved or is asserted not to matter, the observer retains fundamental status. One may argue whether the observer is the same as consciousness, but that is semantics. Neither are explained in terms of more fundamental things, so they are just names for objects that fundamentally postulated, so one can call it the "observer" or "consciousness" or "pink fairies". "Consciousness" is not a terrible term, because bhobba and Weinberg's preferred term is "common sense", and Witten calls it "consciousness".

Yes, of course the observer is consciousness. Science requires theories to be falsifiable. A theory is falsified by verifying that the relative frequency of a specific outcome is different from what the theory has predicted. "Outcomes" are by definition states (of some object) that can easily be distinguished by a human observer. So the "fundamental status" of consciousness/observers is a rather trivial consequence of the fact that the rules of science have been chosen by humans who are conscious when they make their observations.

 

[bhobba]

My view on the "measurement problem" is that it's partially answered by decoherence calculations, and that the rest of it consists of misguided expectations about what a theory is supposed to do.

Well said.

Thanks
Bill

 

[stevendaryl]

My view on the "measurement problem" is that it's partially answered by decoherence calculations, and that the rest of it consists of misguided expectations about what a theory is supposed to do.

Well, the notion of what a scientific theory is supposed to do has shifted over time. Once upon a time, it was about understanding the world. Later, this shifted to modeling the world (and the models themselves might be mathematically complex, so they don't necessarily help much when it comes to "understanding" in the psychological sense). But after QM, the goals shifted once again to merely being able to make quantitative predictions about experiments, and forget about modeling the world.

A lot of people act as if it were unreasonable to ever want more than that, but I think that's a matter of making lemonade out of lemons. If the best you can do is make quantitative predictions, then you convince yourself that you never wanted anything else. But people don't go into science to make predictions. They go into science to understand the world.

 

[bhobba]

A lot of people act as if it were unreasonable to ever want more than that,

Of course its not unreasonable. Its just unreasonable to demand there MUST be more.

Thanks
Bill

 

[stevendaryl]

Of course its not unreasonable. Its just unreasonable to demand there MUST be more.

Well, you could say it's unreasonable to demand that the world be comprehensible, at all. Why should it be?

 

[tom aaron]

Of course its not unreasonable. Its just unreasonable to demand there MUST be more.

Yes. This is difficult for humans to accept. We always assume there is something still hidden behind the curtain. If not a god then some balanced equation that all the variables plug into.

 

[craigi]

Well, you could say it's unreasonable to demand that the world be comprehensible, at all. Why should it be?

Because as sentient beings we require comprehensibility. What would we be if the world weren't comprehensible? We certainly wouldn't be having this discussion.

 

[atyy]

My view on the "measurement problem" is that it's partially answered by decoherence calculations, and that the rest of it consists of misguided expectations about what a theory is supposed to do.

That's fine and reasonable. But I would ask, what happens if experiment does verify that Bohmian mechanics is a more accurate description of reality? Would your position then be that all theories are falsifiable anyway, and the motivation for looking for solutions to the measurement problem like Bohmian mechanics were misguided?

Yes, of course the observer is consciousness. Science requires theories to be falsifiable. A theory is falsified by verifying that the relative frequency of a specific outcome is different from what the theory has predicted. "Outcomes" are by definition states (of some object) that can easily be distinguished by a human observer. So the "fundamental status" of consciousness/observers is a rather trivial consequence of the fact that the rules of science have been chosen by humans who are conscious when they make their observations.

But the interesting thing is that the outcome is not the quantum state of an object. That is why quantum mechanics is different from classical physics.

 

[Derek Potter]

That's another thing that isn't going to fly well here. We don't discuss personal theories. That isn't to say thst we can't discuss what you are curious about, every physicist has ideas. The key is to be careful to phrase things in the appropriate way.

Sometimes this goes too far though. Debating the onticity of the wavefunction, for example, is something which in any other science would be laughed out of the room "If your fossils, Mr Paleontogist, are not something to do with real animals, what is the point in digging them up and arranging them to look like skeletons? Why not just say the little bits of mineral that happen to look like bones are the only reality?" But here it tends to be regarded with great suspicion and discussing whether one should abandon realism or merely adapt what one believes to be real is labelled "philosophy" and off-topic. I do not like the heavy-handed moderation but I do understand that Admin wants to keep the forum productive. In their eyes!

 

[Derek Potter]

...the rules of science have been chosen by humans who are conscious when they make their observations.

An assertion which, I feel, lacks compelling evidence :)

 

[atyy]

I mean it in the sense that just after decoherence is a defined point in time. That was the issue that worried Von-Neumann. The only place that was different is the conciousness of a conscious observer that why he introduced the concept - we now know different.

I don't think von Neumann made a mistake there. In decoherence you still have to choose the factorization, so who is choosing the factorization? If it is not subjective ocnsciousness, can the factorization be chosen objectively and consistently? In fact, there are strong arguments that a factorization can be chosen objectively and consistently - that is what the hidden variables of Bohmian Mechanics do - they choose a finest factorization and compose all other factorization from the finest factorization. So Bohmian Mechanics solves (in all test cases to date) the factorization problem.

Basically, I don't think your emphasis on decoherence without explicit mention of the additional assumptions like hidden variables or Many-Worlds can justify saying that von Neumann was in error. His error was not the von Neumann chain, that was simply one way of stating the measurement problem that exists if hidden variables are not possible, which was certainly a positive contribution.

 

[Derek Potter]

Because as sentient beings we require comprehensibility. What would we be if the world weren't comprehensible? We certainly wouldn't be having this discussion.

Sure we would. The Lizard people - in whose computer we are merely simulations - live in a vastly more complex world totally incomprehensible to us. But for fun they feed us data taht make us think we understand stuff - and then throw a curved ball, like the PE effect, to make us think again.

 

[craigi]

Sometimes this goes too far though. Debating the onticity of the wavefunction, for example, is something which in any other science would be laughed out of the room "If your fossils, Mr Paleontogist, are not something to do with real animals, what is the point in digging them up and arranging them to look like skeletons? Why not just say the little bits of mineral that happen to look like bones are the only reality?" But here it tends to be regarded with great suspicion and discussing whether one should abandon realism or merely adapt what one believes to be real is labelled "philosophy" and off-topic. I do not like the heavy-handed moderation but I do understand that Admin wants to keep the forum productive. In their eyes!

There's a problem here in that "real" means many different things in physics. This leads to prescisely the problem which you're talking about. When the ontology of the wavefunction is debated, it's not comparable to whether fossils are real, but it's easy to see how the confusion arises. I'd recommend staying away from the word "real" altogether, unless it's for well defined and acknowleged concept.

 

[atyy]

Sometimes this goes too far though. Debating the onticity of the wavefunction, for example, is something which in any other science would be laughed out of the room "If your fossils, Mr Paleontogist, are not something to do with real animals, what is the point in digging them up and arranging them to look like skeletons? Why not just say the little bits of mineral that happen to look like bones are the only reality?" But here it tends to be regarded with great suspicion and discussing whether one should abandon realism or merely adapt what one believes to be real is labelled "philosophy" and off-topic. I do not like the heavy-handed moderation but I do understand that Admin wants to keep the forum productive. In their eyes!

Reality is not real. Reality is just a tool to predict the outcomes of observations :)

 

[Derek Potter]

There's a problem here in that "real" means many different things in physics. This leads to prescisely the problem which you're talking about. When the ontology of the wavefunction is debate, it's not comparable to whether fossils are real. I'd recommend staying away from the word "real" altogether, unless it's for well defined and acknowleged concept.

If you can give a couple of examples of what "reality" means then I might agree with you. As far as I know, none of them deviate from "reality = that which exists", the debate is totally to do with what exists, not its manner of existing.

 

[Derek Potter]

Reality is not real. Reality is just a tool to predict the outcomes of observations :)

Wonderful. All the most difficult problems of (the forbidden p-word) solved by physicists who refuse to say what their symbols mean.

 

[atyy]

Wonderful. All the most difficult problems of (the forbidden p-word) solved by physicists who refuse to say what their symbols mean.

Physicists are not real. Physicists are just a tool to predict the outcomes of measurements. P = Physics :)

 

[craigi]

Real means "exists".

In the english language yes, but let me give you a non-exhaustive list of the ways it's used in QM. The real part of a complex number, objectively real, subjectively real, ontologically real, counterfactual definite, a measurable property.

And then people like yourself use the word loosely to mean "exists".

Can you see why it causes confusion?

 

[maline]

I'd say that this confusion arises mainly from the nonacceptance of "reality" as a respectable topic for discussion. This makes it very difficult to develop a common language, so each person uses words his or her own way- and then this becomes a further reason to delegitimize the conversation.

 

[rkastner]

Concerning an earlier comment about decoherence providing the measurement basis:
Decoherence alone does not provide the measurement basis--arguments to that effect implicitly assume a preferred basis from the beginning via designated subsystems for which there is no support from within the theory itself. See e.g. http://philsci-archive.pitt.edu/10757/
For a more elementary discussion see http://transactionalinterpretation....ally-split-in-the-many-worlds-interpretation/
The transactional interpretation gives an observer-independent account of measurement. To get this one must take absorption into account in a direct-action theory. In such a theory, absorption is a physical process: quantum state annihilation (just as emission is quantum state creation). The direct action theory restores symmetry between emission and absorption which are both crucial processes.
For details see e.g. http://fmoldove.blogspot.com/2014/02/the-transactional-interpretation-of.html
[BTW the prohibition on 'philosophy' here is unfortunate, since physics started out as 'natural philosophy' and you can't make much progress in physics research--especially quantum theory--unless you know what your philosophical assumptions are. Disallowing philosophy in favor of 'only what we can measure' is in fact adopting a particular philosophical position: empiricism or positivism. There is no such thing as physics without philosophy. Trying to do it is to adopt unacknowledged philosophical positions. Einstein and Bohr and Heisenberg and Wheeler did philosophy.]

 

[craigi]

I'd say that this confusion arises mainly from the nonacceptance of "reality" as a respectable topic for discussion. This makes it very difficult to develop a common language, so each person uses words his or her own way- and then this becomes a further reason to delegitimize the conversation.

Certainly the discourse on QM Foundations suffers from the issue of a lack of common language. The world "real" being a primary example. The discussion is legitimate and in my opinion it is very much a part of physics, since QM leaves important fundamental questions unanswered, though there are many who, for various reasons, push it into the realms of philosophy. There are many misconceptions that various QM interpretations don't lead to distinct testable predictions or ways to create a theory with broader scope.

Personally, I'd be very suprised if quantum foundations turns out to be an unrelated topic to a sucessful theory of quantum gravity. Many leading QG researchers have a similar viewpoint. It's not mainstream in the sense that it's not taught as part of a core undergrad syllabus, but it is taught.

 

[Derek Potter]

In the english language yes, but let me give you a non-exhaustive list of the ways it's used in QM. The real part of a complex number, objectively real, subjectively real, ontologically real, counterfactual definite, a measurable property.
And then people like yourself use the word loosely to mean "exists".
Can you see why it causes confusion?

No I can't because apart from the first meaning - which is a bit of mathematical history, and the last which is a positivist metaphysical assertion, the rest are simply phrases which couple the plain meaning of real with a context.

 

[craigi]

No I can't because apart from the first meaning - which is a bit of mathematical history, and the last which is a positivist metaphysical assertion, the rest are simply phrases which couple the plain meaning of real with a context.

Beyond the disparate meanings, "real" is often used in an honorific sense. For example, is it important that the inacessible worlds of MWI are real? What advantage does it afford us to describe them as real? If we take your literal english language usage of the term. Then we say that they 'exist', but do they actually exist in any meaningful sense comparable to that of your Paleontologist's fossils?

From my perspective, I don't care if they're real or not, but it causes problems for those new to the subject matter, because the word "real" comes with so many presumptions. I'd rather not use the word, other than in reference to how it appears in the literature.

 

[Derek Potter]

[BTW the prohibition on 'philosophy' here is unfortunate, since physics started out as 'natural philosophy' and you can't make much progress in physics research--especially quantum theory--unless you know what your philosophical assumptions are. Disallowing philosophy in favor of 'only what we can measure' is in fact adopting a particular philosophical position: empiricism or positivism. There is no such thing as physics without philosophy. Trying to do it is to adopt unacknowledged philosophical positions. Einstein and Bohr and Heisenberg and Wheeler did philosophy.]

AFAIK, there is no requirement to stick to empiricism here. Officially at least, the ban is on philosophy. I would quite like to see positivism despatched as ruthlessly as other paradigms but positivism goes hand in hand with "shut up and calculate" which suits the majority of physicists. Or so I'm told.

One day soon I hope to grapple properly with your objections to MWI. That should be interesting :)

 

[Derek Potter]

Beyond the disparate meanings, "real" is often used in an honorific sense. For example, is it important that the inacessible worlds of MWI are real? What advantage does it afford us to describe them as real? If we take your literal english language usage of the term. Then we say that they 'exist', but do they really exist in any meaningful sense comparable to that of your Paleontologist's fossils?

Absolutely. In MWI probability is emergent (pace Ruth Kastner!) and depends on all "branches" existing so that a probability measure (defined by Gleason's Theorem) can be applied on the principle that we do not know what branch we are in. If only one branch existed this would be impossible and MWI would just be sci-fi. Furthermore, if we eschew the childish idea of universe splitting in favour of decomposition, which is a mathematical trick, not a physical event, the "other worlds" are necessarily as existent as ours.

 

[rootone]

My personal objection to MWI as being literally physically real is that it presumes that an infinite amount of physically 'real' stuff' exists.
Many possible worlds of which some become actually real is more persuasive, (to me).

 

[Derek Potter]

My personal objection to MWI as being literally physically real is that it presumes that an infinite amount of physically 'real' stuff' exists.
Many possible worlds of which some become actually real is more persuasive, (to me).

The different worlds are different states of the one universe co-existing in superposition. There is no more an infinity of universes than there is an everlasting blaze of light when a single photon bounces around your room, partially reflected here, diffracted there ad infinitum.

 

[craigi]

My personal objection to MWI as being literally physically real is that it presumes that an infinite amount of physically 'real' stuff' exists.
Many possible worlds of which some become actually real is more persuasive, (to me).

This is an excellent example of what I've just been talking about. If you approach the MWI from the Relative State Forumlation, as Everett initially proposed it, you won't get thrown off before you've even started. If you start by worrying what's "real" and what isn't, you'll doubt it before you even know what it is.

 

[rootone]

The different worlds are different states of the one universe co-existing in superposition. There is no more an infinity of universes than there is an everlasting blaze of light when a single photon bounces around your room, partially reflected here, diffracted there ad infinitum.

A single photon with an infinite number of potential states?
Well I won't rule it out, my math is OK, but not the best.

 

[atyy]

My view on the "measurement problem" is that it's partially answered by decoherence calculations, and that the rest of it consists of misguided expectations about what a theory is supposed to do.

Yes, of course the observer is consciousness. Science requires theories to be falsifiable. A theory is falsified by verifying that the relative frequency of a specific outcome is different from what the theory has predicted. "Outcomes" are by definition states (of some object) that can easily be distinguished by a human observer. So the "fundamental status" of consciousness/observers is a rather trivial consequence of the fact that the rules of science have been chosen by humans who are conscious when they make their observations.

I replied a bit to this in post #60, so am adding some thoughts here.

I don't think what you are saying makes sense.

I think it would make sense if you said there is no measurement problem, by philosophical assertion.

I don't think it makes sense to say decoherence partially solves the measurement problem, and the rest of it is taken care of by philosophical assertion. If one makes the philosophical assertion, there is simply no measurement problem, so there is nothing to solve.

If we don't make the philosophical assertion that there is no measurement problem, then saying decoherence partially solves it is not really helpful. Decoherence is simply a part of Copenhagen, and is a requirement of Copenhagen, since it is what makes the classical/quantum cut consistently shiftable. Saying that decoherence partially solves the measurement problem makes as much sense as saying that Copenhagen partially solves the measurement problem - technically true, but not helpful.

 

[Nugatory]

I think it scares physicists to think of the implications of consciousness being fundamental, because this worldview implies that there is no 'real world' out there,

The idea that consciousness is fundamental to quantum mechanics was first introduced by physicists, so I find myself utterly unconvinced by a bit sceptical of your hypothesis that physicists are frightened by the idea.

Physicists raised the possibility (thereby demonstrating that it didn't "scare" them) to address a particular problem during the early development of QM, and then abandoned it when they found a more satisfactory answer to this problem. There are some serious interpretational questions at the heart of quantum mechanics, and it is impossible to prove that consciousness is no part of the answer to these problems - but that discussion is a completely different discussion happening at a completely different level of subtlety than the pop-sci "consciousness causes collapse" stuff that we're talking about here.

 

[bhobba]

I don't think von Neumann made a mistake there. In decoherence you still have to choose the factorization, so who is choosing the factorization?

This has nothing to do with the factorisation issue - it purely if there is a place that's different in the chain. There is - and obviously so.

Of course all theories are mental constructs and a human is required to interpret it and decide where the decoherence occurs.

He didn't make a mistake - at the time there wasn't as much known about decoherence.

Thanks
Bill

 

[bhobba]

Decoherence alone does not provide the measurement basis--arguments to that effect implicitly assume a preferred basis from the beginning via designated subsystems for which there is no support from within the theory itself

The factorisation issue is well known on this forum. It is one of a number of caveats and going over it here again will serve no purpose - there have been many threads on it. Suffice to say the issue is controversial. That however does not change the fact decoherence does exist, and it has been experimentally confirmed to exist. This breaks the von-Neumann chain by giving a natural place to put the cut.

Thanks
Bill

 

[Dale]

Closed pending moderation.

Edit: this thread will remain closed. I encourage all participants to review the rules regarding philosophy and speculation.