http://www.wired.com/2014/06/the-new-quantum-reality/
Have We Been Interpreting Quantum Mechanics Wrong This Whole Time?
265 thoughts on “Bohm Lives Again–(aka was Krishnamurti right? ;>} )”
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The Skeptical Zone
"I beseech you, in the bowels of Christ, think it possible that you may be mistaken."
SophistiCat,
I’d say it leaks into our interpretation of everyday experience. E.g., it distinguishes phenomenalists from (common-sense) realists.
No difference at all, as far as I can tell.
I don’t understand that. Obviously ontology alone–a categorial matter–can’t make any instrumental difference. But it makes a difference to accounts of what there is in the world–that’s all it’s supposed to do. It neither can nor should do more.
Edit: I probably shouldn’t have said “obviously.” I guess that’s actually somewhat controversial. But it’s my view, anyhow.
That’s only because philosophers give it a false importance, as best I can tell.
As a mathematician, I’m a fictionalist. I see mathematical platonism is silly. Of course mathematical objects, such as numbers, are no more than useful fictions.
I’ve had people (presumably professional philosopher) tell me why fictionalism cannot work, and why I should become a platonist. But I cannot see that it makes any difference. The way that I do mathematics is about the same way that platonist mathematicians do mathematics. The ontological theses have little relevance.
SophistiCat,
Well, it kind of does, in the unaddressed way that ‘worlds’ separate into multiple concurrent realities, complete with branching consequents.
I wonder why multiverse rather than the still-more-parsimonious Single Inevitable Universe? There is no parallel universe with the electron going through the left slit; the slit it went through is the one it was always going to go through – on that occasion. We build up a probabilistic picture because the slit-it-was-always-going-to-go-through is not invariably the left one!
Are you accusing me of being the instrumentalist? That’s not my position. Rather, it’s because I want physics to say something about unobservables in the real world that I think interpreting QM is important.
Now my knowledge of the philosophy of truth/language is pretty rudimentary, but I understand that for a proposition about the real world to be true or false it must be connectable to the real world, eg through some kind of correspondence or through scientific testing and eventual consensus (depending on your approach to truth, I think).
If you want to adopt scientific realism about the things QM addresses, I think you are stuck with either hidden variables or accepting that the quantum state is what the world is at that level of description.
You may find MW weird, but Bohm’s implicate order philosophy of reality which he derives follows from his physics is also quite strange. (Interestingly enough, WJM once said in this forum that there are elements of it in his philosophy of well.)
I understand this as claiming that the MW people start by assuming many worlds. In fact what they do is start by taking the QM formalism literally as reality and then understanding the consequences. I don;t see how “reifying” applies. MWists also see additions like hidden variables as violations of Occam’s razor.
Well, I suspect a lot of scientists would not bother getting up in the morning if they thought all they were engaged in was predicting the results of future experiments.
So there would be much less science done, much less to be published, and so you’d put of a lot of scientific journals out of business in that scenario.
And not only that, you’d also jeopardize the whole future of human progress.
Surely that is a difference?
Among those “experiments” would be useful products, the kinds of things which lead to investment in research in the first place.
Corporations and nations invest in basic research because it has a history of paying off in the long run.
As to what researchers desire, I suspect they desire nice, neat, regular phenomena that can eventually connect families of phenomena. The rest is metaphor.
If you want to adopt scientific realism about the things QM addresses, I think you are stuck with either hidden variables or accepting that the quantum state is what the world is at that level of description.
I think that’s right.
In fact what they do is start by taking the QM formalism literally as reality and then understanding the consequences.
That there must be worlds to explain the fact that we don’t know this or that, seems like reification to me. Frankly, it even seems akin to what theists do on this very site with respect to areas of incomplete knowledge in the evolutionary arena.
I don;t see how “reifying” applies. MWists also see additions like hidden variables as violations of Occam’s razor.
To get from “can’t successfully predict up-spin or down-spin; can’t successfully predict left slit or right slit” to “There exist worlds where each is true.” seems to me almost a paradigm example of reification. Anyhow, I really don’t think those who claim the reality of zillions of worlds are in a position to preach about parsimony.
I don’t think “metaphor” is quite the right word. I’d say that the rest is categorial. Do we see chairs or percepts? Do we hear sounds or ideas? The choice of answers to those are philosophical, categorial, and, I believe, not subject to proof. But the answers are nevertheless different. And while I don’t think one can DEMONSTRATE the truth of one set over the other, one can try to make it reasonable by, e.g., showing consistency with common-sense, language acquisition, comportment with modern science, comprehensiveness, coherence, etc. In other words, they indicate different worldviews.
walto,
I’m with you!
Whew! That’s a hard read.
I know why I’m neither a physicist nor a philosopher.
Fun to try to follow a bit of it, though.
Have you seen the documentary Particle fever? If not, it’s well worth it. I’ve heard it is available on iTunes and I guess it will be available on DVD at some point, if it is not already.
It’s the story of researchers, both junior and senior, who are involved in the search for the Higgs boson at the LHC. I came away with the impression that the reason they were involved is that they wanted to know if the Higgs boson existed and what some of its properties were.
I’ve used this example before but I still think it is telling: paleontologists postulate ancient dinosaurs because they think they existed, not because they want to develop some regularities to predict where they will find fossils.
Yes, I agree that that is one of the blogs best appreciated by professionals. But still, I give it to old (and I do mean old) college try. But my reaction to some of his previous posts mirrors yours.
Parsimony of the worlds versus parsimony of the theory is the issue…
I don’t actually see the relevance.
Incidentally, the example I gave was for mathematics. And, in mathematics, we are not even predicting the results of future experiments.
I would agree that one hunts fossils because they are believed to exist.
But particles are a bit different. It may just be me, but I don’t believe particles exist in the same way that bones or fossils exist. And I’m not sure exactly what I mean by that.
Parsimony of the words versus parsimony of the theory is the issue….
I don’t think anyone is saying we can’t predict things with QM. The problem is having a complete theory that tells us something about the world and is not just good for predicting.
I understand reification as referring to a false attribution of concrete reality to something that is abstract. That is not what MW does. Rather, it takes the QM formalism, which applies to this world as much as to other worlds, and takes it literally.
You make an analogy to an IDists complaint about a evolution. I think a better analogy is to the prediction of other worlds in a multiverse: they exist because they are a necessary consequence of our best scientific theory. (Now that analogy is not perfect, I’ll admit; I am just saying it is better than the evolution one in your note).
My position comes down to this: if arm chair philosophy contradicts physics, then it’s the arm chair philosophy that has to go.
BruceS,
Well – as I wondered above – why is it not more parsimonious to say that there is only one world, and everything that happens in it is inevitable? It would look the same as if we were but one realised reality among many, every one of which is (in its own timeline) ‘inevitable’.
The splitting of worlds is something extra, just as wave collapse or pilot wave.
We see chairs and hear sounds. But so what?
Is there any more to seeing chairs than that we find it useful to name them and describe them? And don’t we name them and describe them, because we find that useful as part of our knowledge?
As I see it, this should be part of epistemology rather than part of metaphysics.
Maybe fairies actually exist, even though I cannot see them. And maybe hamburgers don’t actually exist. But I’m still going to eat hamburgers, and I’m still not going to concern myself with fairies.
Neil, I’m responding to this as best I can in a separate post.
From what I can see, saying “it looks as if” does not address the issue of providing an interpretation of QM that fixes the incompleteness of the Copenhagen approach.
But I am far from an expert on this stuff — I know the names of other interpretations like many-minds or consistent histories but not enough to know how they compare.
FWIW, the World Science Fair videos I linked to concentrated on QBism, Bohm, spontaneous collapse, and MW, so I am taking those as the big 4. But there are also surveys out there, such as this one and this one. Copenhagen wins but is not the majority; further, its winning may just reflect the prevalence of the shut-up-and-calculate (instrumentalist) approach of working physicists.
BruceS,
No, but the MW approach hinges upon a proposed actuality – all quantum possibilities are realised. An alternative, and identical (for any observer) actuality is that there is only one timeline, and everything that happens in it was, from the very start, ‘bound to happen’ within that timeline. We do not, after all repeat specific observations. We build a statistical viewpoint because independent observations can go different ways. So I’m just wondering what would persuade us that MW was ‘probably correct’, in preference to what I will dub SIW – the Single Inevitable World. Any observer – including one who fed his/her observations into the equations of QM – would inevitably be constructing his/her hypotheses on the basis of multiple independent observations of separate quantum occurrences. You can never repeat a specific observation. A particular timeline in MW can not be ‘more’ correct than the One True Timeline in SIW. One could be fooled by the apparent indeterminacy of separate observations in SIW into thinking that the equations derived therefrom mandated separate simultaneous realities in which all outcomes happen.
Is it not just a metaphysical preference, to assume all outcomes, and avoid the implication of absolute determinism? Or is it necessary that the two worlds continue to interact for a period in order to create an interference pattern? That’s where MW becomes as flaky, and ad hoc, as its rivals. All require physics to do something somewhat mysterious.
I’m afraid I don’t understand what you are getting at. Are you saying that the world of any given observer is completely deterministic? How is that compatible with QM (unless you are referring to the determinism of hidden variables?).
I do agree that physics is mysterious from the perspective of the arm chair. But that is not an argument against the physics.
BruceS,
In the MW interpretation, all possible outcomes of an ‘indeterminate’ choice occur. One can imagine this building into a set of infinitely branching timelines. In any one such path, an observer sits at the end of a particular set of occurrences, with no access to the assumed parallel worlds. But what is the difference (not just for that observer, but for physics) if we say that the other paths aren’t even there?
We add these extra worlds to deal with the indeterminacy of a single timeline, but the indeterminacy we wish to account for is serial. If you do a measurement one time, and then at another, you get a different result. But you can’t do the original measurement again. So MW is saying that, because serial measurements are indeterminate, each individual measurement’s possible outcomes actually occur – in parallel. It is unverifiably possible that any given measurement simply had to be like that.
Perhaps determinacy is a red herring. Say it’s a Single Indeterminate World instead. The role of MW is not just to allow for all outcomes in reality, but to thereby provide something for ‘left-right’ photons to interfere with, as the worlds decouple.
No-one’s arguing against the physics. We are arguing about what unverifiable unknowns (hidden variables, many worlds, wave collapse) best satisfy the desire that it make some kind of sense.
I understand this as saying that you think the problem to be solved is the indeterminancy.
But I don’t think that is the problem QM interpreations are trying to solve. Instead, they are trying to explain why we don’t see superpositions. Superstitions is what the theory predicts. Copenhagen is incomplete because it relies on the collapse process, an unexplained ad hoc addition, to get rid of the superpositions.
(Decoherence is sometimes thought to solve this issue for Copenhagen, but it does not.)
This is a common misconception among the laypeople (philosophers included). Standard quantum mechanics (a.k.a. the Copenhagen “interpretation”) does not try to get rid of superposition states.
This mistaken point of view is based on the notion that there are some fundamental states that are not superpositions of other states. But there are no such privileged states. In linear algebra (the language of quantum mechanics) any vector can be written as a superposition of other vectors. E.g., (1,0,0) can be written as (1/2,1/2,0) + (1/2,−1/2,0). If our apparatus measures the coordinate of a particle, the measured states with a given coordinate x are superposition of states with many different momenta p. Or if we measure the spin component along z, a state with s_z = +1/2 is a superposition of states with s_x = +1/2 and s_x = −1/2.
I am not impressed by the Stanford Encyclopedia’s treatment of decoherence. We can discuss this, but that would require more than a paragraph or two.
But don’t we need to add the collapse to Copenhagen to get to the state that does not involve superposition of possibilities for the measuring device and the entity being observed? I understand that even this collapsed state is still a quantum state, but my understanding is that the problem is that it is not one that has evolved in line with the rest of the theory (ie the Schrodinger equation).
I don’t know how much I can offer for a two-way discussion, but if you wanted to explain your concerns, I would certain be interested in them to help me understand decoherence better. My currently understanding is basically at the Sean C popularization level (although I did study math many years ago and am not put off by vector space references).
The SEP link was really a way for me to avoid trying to post something explicit, since I don’t understand the details of the issue that well. With only a rudimentary grasp of decoherence, I am relying more on the impression that so many informed people seem to think the measurement problem is unsolved under Copenhagen, even though decoherence has been around for some time, that the SEP’s point of view must be basically right.
BruceS,
No – later in the post I suggested that indeterminacy per se is perhaps a red herring. I am questioning what the ‘other worlds’ are doing in the MW explanation. To dismiss wave function collapse in favour of all possibilities being realised does not seem to leave one any better off – something ad hoc has still been imported, to serve some purpose. So why not as readily say that it was ‘bound to happen’ the way it did, on that specific occasion? As I say, the need for a parallel split – or for observational ‘wave function collapse’ – are actually due to a picture of weirdness determined from serial observations. Perhaps you don’t see superposition because there is no alternative in any given instance.
Of course, you do build an intereference pattern from single electrons, provided you don’t monitor their slit. In MW, this is taken to mean that the left and right worlds continue to interact prior to complete unzipping – as with the split itself, rather ad hoc.
Let’s try this approach. When someone complains about additions to “this world”, I’d ask: starting from the Schrodinger equation, where does “this world” come from?
1. You can say there is a collapse. That’s adding something new that the theory does not account for. You’ve got a quantum state evolving according to the rules, and then this unexplained collapse occurs. Adding something as a brute fact, ie the collapse process, to the theory to make it conform what we see is ad hoc.
2. You can add something new to the Schrodinger equation itself: a stochastic element which builds collapse right into the theory. Those types of theories are out there (eg GRW), but they are not technically complete (eg wrt SR) and have the unappealing aspect of adding something to a working theory of physics for metaphysical reasons.
3. You can add something to the quantum state. That’s hidden variables. Then decoherence can be used to explain the appearance of those hidden variables (positions, possibly of measurement instruments) in our classical world (but don’t ask me for the details of that statement!). But that also means you are adding something to a working theory of physics. I also understand that hidden variable theories are also not technically complete, possible wrt SR again, although I am not sure about that.
4. You can add nothing and say that the reason we see a classical reality is that the physical basis of our consciousness has become entangled with the superimposed system and so in some sense our consciousness has split and each aspect of the split sees one classical aspect of the superimposition. Nothing is added to the existing QM formalism. It’s definitely weird, and there are technical issues, but it is not ad hoc in any way that I can see (nor have seen any informed commentator make that complaint.)
I don’t understand why you think collapse requires serial observations. As I understand it, even a single interaction between a measurement device and an entity which is in a superposition state wrt the aspect to be measured extends the superposition to the measurement device, since it too is subject to quantum rules. That is what It happens according to the theory unless you add something as per 1-3 above.
I’m afraid I don’t see how the phrase “no alternative” can help in an explanation.
I don’t really see how the idea of Quantum mechanics is much different than the notion that if you look closely enough at the tip of your finger, there is nowhere, where it ends and the empty space around it begins. Or if an arrow is flying through the sky, where is the tip, and where is the air it is moving through. In essence the tip doesn’t really exist except in our perception of it.
If we could look closely enough at anything, the definition of its existence always would disappear. I don’t think that reality suggest other worlds must exist.
You have to separate QM the science from the philosophy that I take this thread to be about.
QM is the most successful science in terms of prediction accuracy. That’s all a scientist needs.
If your philosophy of science leans to scientific realism, then you will want to see how you can develop an ontology based solely on the science in QM.
But I suspect that you are right that many scientists would see this type of exercise as pointless.
BruceS,
I don’t know what you mean by scientific realism.
Are you talking about the realism that we perceive or a realism that exists independent of our perception?
If its the latter, what is the realism of a distinct object? Does any object exist independent of other objects?
Jesus dun it!
OMagain,
Are you scared to death of the concept, or simply obsessed with it?
You must have had some scary experiences with Priests in your childhood or something, because you can’t seem to get it out of your mind. The scars must be deep, I never met someone so guided by religion.
Realism: we should believe the unobservables that are part of our best scientific theories refer to things that exist. Anti-realism (of one type): we should only believe in things we can observe; we should evaluate the truth of scientific theories by how well they predict those observables. Statements involving unobservables are true if they predict observables well but we don’t need to believe in the existence of any unobservables the theory refers to.
Higgs Bosons and ancient dinosaurs would be two examples of unobservables, I think. We can observe their effects on scientific instruments or even directly (eg fossils) but we cannot observe them directly.
ETA: dinosaurs may be a poor example for this type of anti-realism. For they can be observed today (birds), so maybe just believing in evolution commits you to treating ancient dinosaurs as observables (like last year’s swallows).
More here if you are really interested in pursuing this. Fair warning: I’m not interested in spending effort in exchanges with those who don’t have an interest in coming to grips with what the philosophers say on this topic.
Walt might be interested in that type of philosophy, but me, not so much. No doubt a failing on my part.
BruceS,
Bruce,
Sorry, but I don’t really see this philosophy-science dichotomy you are inferring.
I am asking scientifically if a distinct object exists, and if so how do we define that.
You may want to call it scientific, but it’s philosophy to me, namely metaphysics. Especially when it comes to unobservables. I’ve basically gone down this path already with WJM, so I think I’ll let it go this time.
Again, regarding the existence of everyday objects, sorry, just not interested.
Bruce,
And is this not the fundamental problem of QM? QM says we can not define an object if we look closely enough.
I don’t think this is a philosophy question per se. If we can never get to the level of distinctiveness of an object, how can we claim to be measuring that? What are we claiming we can’t measure without the act of measuring affecting the position of the object?
What is the thing QM can’t measure?
Bruce,
So what you are saying is that everything in QM is metaphysics, because we can’t observe it?
And I will just say this Bruce. What I am suggesting is not philosophical at all, I am suggesting the reason we can’t understand QM is because we can not determine what we are measuring.
The whole idea that the act of measuring something effects its position, is based on reasoning which is not solid. If an object has wavelike properties, then it is impossible to measure it completely because we don’t know where the wave begins and where it ends. It like saying how long is a piece of heat.
I bet Jesus understands it!
You are definitely correct that QM does not agree with common sense.
So much the worse for common sense.
What is this question supposed to mean? If there is more than one object in the world, does that mean that at least one object exists independently of other objects, or do you means something by “independently” other than separately exist at the same time? (In philosophy, unlike in prayer or religious talk generally, it’s important to say what you mean and mean what you say. In those other areas speaking in tongues is OK.)
This is actually a cogent question in the current context. What is the criterion of existence of a physical property, in particular, does it “belong” to the object in question?
In undadulterated quantum physics (without the metaphysical baggage of “wave function collapse” [not a part of the original Copenhagen view e.g Bohr], “pilot waves” or “many worlds” etc) a physical property exists to the extent that it can be inferred from actual goings on in the world. For historical reasons those goings on are called measurements, actual events that warrant inferences to the possession of physical properties and the values of physical observables.
This is where I came in. Back to Bohr:”any attempt to more closely follow the course of events (find values for observables conjugate to those measured by a particular experiment) requires a change in the experiment [b]incompatible[/b] with the original phenomenon (what your current experiments measures).. Let me translate this into English: The contingent properties of a physical system “belong” to the experimental situation (emprical context) not just to the object of investigation, the existence of physical properties depends upon what happens in the rest of the world. In general there is no such thing as “what is real for the object”.
Bohr believed that this was the basic “epistemologicl lesson” of quantum theory, yet he argued strenuously for the completeness of QM against the “proof” by Einstein, Podalsky and Rosen(1935) that quantum theory must be incomplete. (as it is according to [b]their[/b] criterion of “reality”. which was”
” If it its possible to predict with certainty or at least with probability one. the value of a physical quantity, then there exists an element of physical reality corresponding to that quantity”.
Bohrs and my criterion of reality is this: what can be inferred from actual events and state of affairs in the real world…full stop. These constittue the facfs that can attributed to a quantum or any other physical system. In QM those facts depend not only for their values,( if they have any), but for their existence upon the “whole experimental arrangement” i.e. the rest of the world in the relevant context. If there isn’t any matter of fact that can be inferred about a property there isn’t any property to discuss, physically or philosophically. What BruseS owes us and has not supplied is what is his criterion of “reality”
Bohr said chillingly that : “there is no quantum world!”. I would say that there is no unmeasured world which is why I think the so-called “measurement problem” at least in its cruder forms is a red herring. The problem of “interpretation” in the contxt of QM is not to try to read of from the formalism of the theory an “ontology” of the world, but the much more difficult and subtle issue of what must the world be like if this theory is correct. Not the same problem by a longshot!
“Inferred” would seem to me to be open to a range of interpretations. The formalism of QM is inferred from events in the world and interpretations at least partly inferred from it. So in that sense your definition seems compatible with what I was trying to say.
But what is measurement? Don’t you need to understand that to talk about a measured versus unmeasured world?
I’m missing the the difference in meaning between “ontology” of the world and what the world must be like, a difference which you seem to be emphasizing. Also, why the scare quotes in “ontology”. Am I misusing the word?
That’s way beyond my pay grade. I’d probably grope towards saying it is something that is based on/compatible with/extracted from the entities in our best scientific theory of the domain under study. When the domain is the fundamental constituents of reality, that science would be QM. Given that approach, it seems to me you have to start by moving beyond the QM formalism to work with an interpretation.
Question: Is “empaist” somehow a play on words of the name of the physicist/biographer Abraham Pais?
empaist,
Indeed!
When Bruce says he is not interested in the philosophy of science but simply the reality of it, the real world of science says “I don’t care what you are interested in, I am what I am.”
If as you say we measure events instead of objects, then measuring something is necessarily part of the event.
If you want to make guess about what it is, you can’t say this part is the science and this part is the philosophy, they are all both.
If one says they are not interested in what we call real, then they are simply saying they are not interested in science. Fair enough.
Can one imagine Einstein saying he was not interested in philosophy? I don’t think relativity would have gotten very far.
Another very important matter in philosophy is not to confuse being with being known, ratio essendi with ratio cognoscendi. The experience of X –whether X is an object or event–is not itself X. Experiences are had by people. Oranges (e.g.) are not had by people. Your experience of an orange may take place over a period of a couple of minutes, but the orange doesn’t take place over a couple of minutes. Our knowledge of objects and events depends on experiences of them, but that doesn’t make them identical to experiences of them. Failure to make that fairly simple distinction has led to all kinds of ridiculous philosophies, most notably Hegelian idealism.
Similarly the science of X is not X. It is one way–perhaps the most important way–we come to understand X. But, e.g., there was weather, long before the science of meteorology. Thus, while one who is interested in X is making a terrible mistake in saying they aren’t interested in the science of X (or vice versa), to say one thing is NOT simply to say the other.
Again, the importance of being able to consistently make this distinction is nearly paramount in philosophy. Even if it could be shown that experiences of things always affect those things, that would not make the experience the thing. Take another example. Murder trials may require experiences of events to proceed but their focus is the alleged killing. Exactly the same experiences may occur whether or not anybody was actually killed. That’s how experiences work: they can be deceiving in a particular way that events (other than experiential events and events/items that are derivative–like stories) cannot. That’s because they are what philosophers call “intentional.”
The moral is, phoodoo, nearly every word in your post above is confused.
empaist,
empaist, what I take you to be saying in your post is that you prefer a commitment-free instrumentalism to scientific realism. You’re not alone in that. I don’t think it’s the majority position either among scientists or philosophers (though I could be wrong) but it has long been popular nevertheless. I personally take a realist view, largely because I think the instrumentalist position cannot be confined to “science” but dribbles into everyday life. And the view that tables and sunsets are useful theoretical entities not is not only inconsistent with what these terms mean given how we learn language, but is a view that almost no one in the world has actually ever held except when doing philosophy. Those seem to me to be very big strikes against that position.
I wanted to tell phoodoo that he cannot goad me into a reply by putting words in my mouth.
But of course I’d be contradicting myself if I did that.
Thanks for giving me the opportunity to vent without contradiction.