Maybe this has already been worked out for me - and you - and everyone else. Personally, I suspect there exists some kind of ‘unification’ of all the universe. This might act through entanglement, but it’s hard to now.
Delayed Choice Quantum Eraser Experiment.
A special crystal, placed just behind the double slits, is used to absorb an incoming photon from each slit, which then creates two new photons, each with half the energy of the original. So each photon that goes through each slit has a ‘twin’ of itself created, called an ‘entangled pair.’
The special crystal is designed to maintain the coherence of the wave so as not to disrupt and collapse it.
One photon of each entangled pair of photons is sent to the screen. This will produce an interference pattern because no particles have been detected yet.
The other ‘twin’ photon of each pair is sent to a detector which registers which slit the photon went through. This is ‘which way’ information.
Call the detectors A & B.
If detector A lights up a photon passed through slit A. If detector B lights up a photon passed through slit B.
After some time, two piles of photons build up on the screen. This is because knowledge of which way the photons went through the slits is known due to the detectors A & B.
The experiment is set up to ensure the set of ‘twin’ photons that are detected by the detectos A & B reach them AFTER their counterparts reach the screen.
So initially, photons reach the screen causing an interference pattern but when registered by the detectors A & B, a ‘particle-like’ pattern is seen. This is because ‘which-way’ information is now known.
So the reality of the interference pattern is now replaced by the reality of the particle patterns retroactively! The future has changed the past!
Since entangled pairs are used, using one of the pair should not effect the other and ruin its coherence (i.e. the ‘sameness’ of the wave.)
When a quantum eraser element is introduced into the experiment, any information about ‘which-way’ is destroyed.
Beam-splitters are attatched to each of the detectors A & B. (A beam splitter is a half-silvered mirror which allows 50% of the photons to reach the detectors, 50% to reach two further detectors, C & D.)
In this arrangement if detectors C or D light up we have no ‘which-way’ information because, again, half-silvered mirrors are used to send 50% of the photons coming from detectors A & B to detector C, 50% to detector D at random. So which-way information is now scrambled.
If the screen is now looked at an interfrence pattern is seen because which-way information is not now available.
The strength of the Copenhagen Interpretation is that it avoids any ‘physical’ interaction that moves faster than the speed of light.
Any physical interpretation of the wave function, like, for example, the De Broglie-Bohm Pilot Wave Theory requires an underlying physicality, i.e., a set of defined properties that evolve with the wavefunction. In other words, ‘hidden variables’. The problem with this approach is that such physical properties need to act and change instantly over any distance or, put another way, have ‘non-locality.’
This tells us that any metaphysical interpretation of QM is no less crazy than a physical one.
The answer might be in entanglement.
Entangled particles are able to ‘connect’ instantaneously and do not violate causality. They might be able to affect coherence/decoherence retroactively and physically without violating causality. ‘Observation’ could just be an entanglement between observer and experiment.
[off topic]
Is there any evidence though, that ‘mind’ is anything more than just very complex processing? - that is, that semantic understanding is not just highly-complex sets of syntactic processing?
Here’s an example of semantic ‘mind’ stuff that can be actually demonstrated to be made up of a very large and complex arrangement of simple switches:
Well, it’s tempting to think of the mind, the universe, as essentially a set of simple switches but that is probably because we have become accustomed to thinking in terms of the way digital computers work which is just the* current* way of looking at intelligence/consciousness.
I think when we talk about ‘mind’ it is as well to remember that we too are a part of the universe and evolved out of the basic constituents of the big band and the way the universe evolved after that. There are probably ‘connections’ that we don’t understand at the moment that exist between particles and forces which include our consciousness, although traditionally, it has been the practice of science to regard a separation between us and the rest of the universe and to look at things ‘objectively’ as if we had no influence or connection at all to whatever it is we are studying.
Personally, I think it will eventually be realized that ‘mind’ is more than an individual brain and body and that it is a composite of biology, physics and so on connected on a universal level. This might be something like entanglement which suggests that everything is, at some fundamental level connected, so that it then becomes impossible to really separate an observer from the observed. This could be why QM seems very weird. It might be that our participation in any experiment has an input which effects the outcome in unpredictable ways. Why should mere inanimate stuff behave in ways that defy classical behaviour? Because in classical experiments our ‘mental’ effect is too small to be noticed but on the quantum level has a significant effect. People like Newton wouldn’t have known about this which led him to describe the universe in terms of a clockwork mechanism. Quite understandable. Where do we really get our ideas from? From the brain alone? Possibly, but we might also be able to ‘plug in’ to a kind of ‘universal internet’ - a kind of ‘quantum computer’, connected, via entanglement, to a form of universal processing system. None of this can be proved, of course, but intuitively it is an appealing idea.
Not to me it isn’t. Intuitively and analytically it has all the hallmarks of quasi-philosophical wishful thinking.
Now if you took some time developing the very interesting hypothesis about us all being evolved from the constituents of a big band, which you snuck into this post, I would enjoy reading about it.
That ignoring the experts on this thread who are trying to teach you something because their “worldview” is unwise.
I didn’t really ‘snuck’ it into my post. I was just suggesting we are part of the universe and the 'stuff 'we are made of is fundamental, therefore, there could (and in fact should) be some kind of connection. How do you think progress is made in science? By speculating based on general observations and also experimentation. It’s called philosophy. You seem to be ignoring the striking data we have gained from quantum experiments and the apparent connection there seems to be between us and the experiment. Anyone can be dismissive when they have nothing more helpful to say.
Oh, haven’t you heard? The experts don’t agree. Well, the experts that count, anyway. 
I’m probably older than you are, so before you were born, did I only exist as a probability which didn’t become a reality until you were born?
And you honestly don’t see that this might be a problem with your approach? I mean, all you’re really ever get about quantum mechanics is third-hand accounts, at best. And like a copy of a copy, such accounts will inevitably lack fine detail; which you then attempt to fill in—to the best of your abilities, I’m sure. But in the end, you’ve got something that doesn’t bear all that much similarity to actual quantum mechanics.
Furthermore, all of the information you need is out there, most of the time for free. There’s lots of MOOCs covering the basics of QM; or, get a book, like the one from Albert I mentioned before, or something like Susskind’s Theoretical Minimum, which is a bit more up to date (although I haven’t read that one). Because honestly, you’re depriving yourself of genuine insight if you just stick to YouTube videos employing dubious analogies.
No, I fully acknowledge that models depend on the existence of human beings. But you’re arguing for the opposite: that the way nature works depends on our models. That, there’s no rational grounds for.
This is false. If you’re just looking at the screen in the delayed choice experiment, you won’t see any interference pattern. It’s only after you weed out some subset of events that an interference pattern becomes visible.
In the setup you describe, there will be an interference pattern visible if you only take those photons whose ‘twin’ was detected at detector C, or those whose ‘twin’ was detected at detector D. These patterns are phase-shifted with respect to one another, so that their sum is exactly equivalent to no interference pattern at all.
Otherwise, you could use this setup to send a message with faster-than-light speed. But it’s simple to prove that quantum mechanics doesn’t allow for such messages (the so-called ‘no-communication theorem’).
So, what actually happens in the delayed-choice experiment is that you’ll get the same pattern of dots on the screen either way. Now, if which-path information has been collected, and you weed out those photons whose twins have been detected at A (or at B), you’ll get the qualitatively same pattern of less intensity—i.e. no interference.
If, however, no which-path information has been collected, and you throw out those photons whose twins were detected at C (or D), you’ll get a nice interference pattern.
But, and that’s the crucial part, you always need to know what was detected at the detectors A-D before the absence or presence of interference can be ascertained. And with this, it becomes just a more elaborate version of the analysis I presented above: if there’s some large system that’s changed its state based on which way the photon took, and consequently, became entangled with it, there won’t be interference, due to decoherence; if there are no correlations between the photon path and some detector, there will be interference.
Bohmian mechanics at least has a well-defined mechanism as to how it works—how all those counter-intuitive phenomena actually come about. That’s leaving it in a better state than simply saying, ‘consciousness is just magical, and poof! Reality!’.
In other words, Bohmian mechanics and other interpretations actually do provide an explanation, rather than substituting another (and possibly even greater) mystery.
Every interpretation of physics is metaphysical. Metaphysics simply is the study of how the world actually works, or consistently might work, and what its fundamental nature is; physics is merely concerned with its description.
Entanglement is not some spooky influence wildly doing whatever it wants to; its effects and properties are well studied. It’s not some instantaneous connection—not anymore than classical probabilities are, at any rate.
Say I have to cards, a red one and a green one. I put each in an envelope, shuffle the envelopes, give one to you, and keep the other for myself. Each of our envelopes then is in a state of ‘containing red card’ with 50% probability, and ‘containing green card’ with 50% probability.
Now, no matter where I am, be it in China or on the moon, if I open up my envelope, my description of it suddenly changes—from ‘50% red, 50% green’ to ‘100% green’, say. That’s nothing surprising; I made an experiment, learned the outcome, thereby reducing my uncertainty about the world.
However, instantaneously, my description of your envelope also changes—to ‘100% red’; no matter how far apart you and your envelope are. Would you say that in this case, too, there is some ‘instantaneous connection’?
Now, it’s true that entanglement can’t be explained by such a simple model. The reason for this is the existence of non-simultaneously measurable properties, which do not admit a joint probability distribution. But in the end, things are, conceptually, not necessarily any different.
Of course, you can introduce a dynamics that actually goes and changes the state to fix observations, as is done in Bohm’s theory; but you can also do that in classical mechanics. The point is, nothing is forcing you to do so.
Why shouldn’t it? Why should it behave in ways that are in accord with classical behavior? Who’s told you how stuff should or shouldn’t behave?
Well, that’s a whole other debate. I’m not sure about evidence—indeed, I’m not sure what evidence of this kind would look like—but I do think that there’s good conceptual arguments that imply computation simply isn’t the right notion to explain mind.
One argument essentially is that computation is always already mind-dependent: whatever computes, does so by virtue of being interpreted as realizing some formal structure. Without this interpretation, there’s no computation; but then, trying to use computation to explain the mind—and thus, interpretation—will be inevitably circular.
One can make this argument more formal. What’s a computation? Well, it’s a mapping between certain physical states of a system, and states of a formal object—the program, calculation, or algorithm. That’s how a light coming on may stand for a truth value, for instance.
But such a mapping is semantic. Without such semantics, the light would just be a light, nothing more.
Now, of course, it might be argued that this semantics can itself be analyzed in terms of computation—that whatever we do when we interpret a system state as a logical state, could be done just as well by a machine. But then, how would that machine do it? By computation?
Then we’re back to square one: because that computation will be a system traversing a sequence of physical states, mapped to states of some formally defined object. And this mapping is semantics. Now, of course, we might try and realize that semantics by means of some computation. But then, well…
So, we enter into something like the homunculus problem: inadvertently, we always have to introduce some ‘meaner’ into the description, some entity that maps symbols to their meanings (physical states to formal ones). But when we try to analyze that entity, we find it’s turtles all the way down.
Now, while I do think that this sort of thing is fatal to traditional computationalist accounts, this doesn’t mean we need to introduce anything mysterious at all. The world is completely natural, but computation is just a gloss; just a certain way of interpreting the world, nothing fundamental. That doesn’t mean that meaning can’t be naturalized. Indeed, I’ve just won a prize for a proposal of how this might come about. Alas, the margins of this post are a bit too small to contain it… 
Well, yes…and no. Those pixels and bits correspond to airplanes in flight, crates in the warehouse, and naked people making whoopee. You might argue that only human minds make the final result meaningful…but the intermediate results are remarkably concrete. Computers move crates around in warehouses, without any human intervention or perception at all. Computers do real work.
I think it’s going too far to say that a human mind is necessary for anything to have “meaning.”
(And, after all, our brains are made up of neurons, so that ultimate “meaning” is also just fibers, chemicals, switches and pixels.)
Well, if you look at it from the point of view that you I, my mother, my father, et al, is basically* information *, then the question then becomes: did information about you exist before I was born? I think we can clearly see the answer is YES. Information does not suddenly disappear like that. You would have to somehow completely and utterly destroyed all traces of information about you existing in the world and this would be very hard to achieve.
Fine detail is one thing but are you honestly suggesting the people who present these YouTube guides are going to overlook glaring errors in their descriptions? I appreciate they have to ‘dumb down’ to some extent the ideas for popular consumption but many of these people are supposed to be experts in their own right and would probably not want to look like idiots by giving out false information. It seems to me you are completely disagreeing with many interpretations and even some of the technical details of these experiments, so I have to ask myself why you would do that.
The team that conducted the 1999 delayed quantum eraser experiment seem to think something very strange is going on and they seem eminently qualified to do so. It is your right to disagree but why would you completely dismiss these results?
BTW, why would Richard Feynman (and others) say ‘nobody understands quantum mechanics?’ Do you know something he and others don’t? You seem to have discovered some answer others have missed.
In a way, yes. Remember any model is just an interpretation which is always a subjective process.
You see, this is the trouble. You cannot accept that these effects happen instantaneously which implies non-locality. You keep trying to base these results on some kind of ‘physical’ theory and it just doesn’t work. You want to bring in ‘hidden variables’ but no evidence of these has ever been found, yet you cling on to the hope that a metaphysical model of QM is impossible. Just examine the evidence.
You see, to me, what all this discussion and disagreement demonstrates quite clearly (and I’m not just referring to this *particular * discussion, as I’m no expert and there are plenty of really clever and qualified people out there who still disagree with one another) is that scientific models are highly subjective depending on how they can be interpreted. Now, you have your views and that’s fine but unless you can show there is a general consensus among similarly expert opinions how can we assume one idea is better than another? I don’t pretend to understand the mathematics but you can ‘prove’ anything with mathematics. What you need is a repeatable model of reality that accounts for the behaviour of the phenomenon. Now, with something like Relativity this can be done, at least for now, but regarding QM, although the computational ability of the modern era is something the early twentieth century physicists would have died for, the ‘meaning’ of what these results show us still seems to elude people. It’s like I said: models of reality are subjective and the more elusive the phenomenon the more subjective ideas will proliferate. If your model was correct how come it has not been accepted by the scientific community as being the best answer to the big question? Doesn’t this all point to the conclusion that consciousness creates reality and different kinds of consciousness creates different kinds of reality?
Are any particular members of the band important? The percussionist, right? Or anyone playing a string instrument perhaps …
Quite often they do, yes. After all, there are very many videos on YouTube arguing for chemtrails, the moon hoax, or the flat Earth. Expecting that everything you watch on there about quantum mechanics must be right thus isn’t a very reasonable thing to do.
But even if they’re broadly accurate, they have to employ metaphor and analogy to talk about quantum mechanics, and while these metaphors can be highly informative if you know their limits of accuracy, they can also be highly misleading if you don’t.
Take, for instance, the classical ‘rubber-sheet’ analogy to demonstrate how gravity works in general relativity. I’ve actually seen people make the argument that this implies that GR must be circular—since which force holds the little balls on the rubber sheet in the first place? What allows them to make dents in the rubber? That’s right, gravity! So, the explanation GR gives for gravity appeals to gravity, which is circular. Einstein was wrong!
Except of course it’s not like that at all, but what it’s actually like is hard to explain without knowing how general relativity really works. So what happens is that science communicators employ analogies that are perfectly fine if you know what you’re talking about, but that can be stretched to absurdity; however, that absurdity does not carry over to the actual theory.
That’s essentially what you’re doing, as well. You don’t know how quantum mechanics actually works, so you take reasonable popularizations and simplifications and twist them far beyond what they can bear to arrive at interpretations that simply have no grounds in actual quantum mechanics. The only remedy for that is, I’m afraid, to learn actual quantum mechanics.
There’s also the point that doing science is something very different from science communication. The former has to conform to standards of objectivity, repeatability, falsifiability and the like; the latter has to be popular with the audience, or nobody’s gonna watch. So those that can produce the bigger show are going to attract the bigger audience; but it’s not always the case that this goal aligns with that of factual accuracy. In other words, cool and mysterious half-truths are always going to be more popular than boring truths.
Another point is that proper research into the foundations of quantum mechanics is really quite a young discipline—or maybe, a recently revived one. It used to be the case—thanks in part to luminaries like Richard Feynman—that such research was viewed as enormously suspect, and basically career suicide. It’s really only in the last ten to fifteen years that, thanks in some part to the flourishing of quantum information theory (and I don’t just say this because that’s what I’ve got my PhD in), we’ve gotten some respectable research in quantum foundations (again).
Before, the prevailing attitude was one of ‘shut up and calculate’, or in the words of Feynman:
[QUOTE=Richard Feynman]
Do not keep saying to yourself, if you can possibly avoid it, “But how can it be like that?” because you will get “down the drain”, into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.
[/QUOTE]
I’m not, though. If you’re referring to the delayed-choice experiment, and my claim that you’ll never see interference if you don’t post-select on what was detected at the far-away detector, then that’s just what you’ll actually see in the experiment. Just look at the wikipedia article, figures 4 and 5. As it says there:
[QUOTE=wiki]
The total pattern of all signal photons at D[sub]0[/sub], whose entangled idlers went to multiple different detectors, will never show interference regardless of what happens to the idler photons.
[/QUOTE]
Also, the calculations I presented, and their interpretation, is just bog-standard QM.
Note that all of this doesn’t mean that quantum mechanics is essentially fully explained, that there’s no problems anymore at all. Decoherence doesn’t solve the measurement problem: while it can explain the classical statistical distribution of events, it does not tell us how the individual events come about—and that’s where wave-function reduction happens. In other words, the question of how a given element from a superposition is suddenly chosen as the actual state of a quantum system is still a puzzle—but not (and here I again state the opinion of the vast majority of researchers in the foundations of quantum mechanics) one where appeal to consciousness is likely to be of any help at all.
The answers I’ve produced here come straight from textbooks. I’m not claiming any originality.
Yes. But that doesn’t mean there is no objective nature out there to which our subjective models are at least approximations of ever increasing exactness. And indeed, this is the simplest explanation for why we are able to find successful models at all.
I do not accept this because it’s not true. Quantum mechanics can be interpreted in ways such that there is no non-locality.
I’ve spent quite some time doing so—and I mean actually doing so, not merely watching dubious YouTube-videos.
And I’m not actually a fan of hidden variable theories. Indeed, I’ve published a theorem excluding certain kinds of hidden variable theories. But that doesn’t mean such interpretations are inconsistent. However, the mere possibility of such interpretations means that the consequences you want to draw simply do not follow from quantum mechanics.
As I’ve said, I haven’t really presented you with anything but vanilla quantum mechanics so far, which would for the most part be completely noncontroversial (of course, there’s always a curmudgeon in the room). The problem is simply that you erect conclusions upon popularizations of quantum mechanics that are not supported by actual quantum mechanics (and for the most part, aren’t supported by the popularizations either).
I’m not sure how to show there’s a general consensus, but by way of some data points, look to Scott Aaronson’s answer to the question “Does the delayed-choice quantum eraser experiment imply that conscious awareness collapses the quantum wave function?” on Quora:
[QUOTE=Scott Aaronson]
No.
In general, if someone asks, “Does experiment X imply that conscious awareness collapses the quantum wave function?”, then the answer is no.
[/QUOTE]
He goes on to make exactly the points I’ve made.
Aaronson, by the way, is a noted expert on quantum computation, and author of the very informative and highly entertaining introduction to quantum computation, Quantum Computing since Democritus.
Furthermore, as a sort of snapshot of attitudes among working physicists, take this poll: regarding the importance of the observer, only 6% proposed a distinguished physical role, e.g. as collapsing the wave function.
So you see, the vast majority of physicists agree that there’s no special role for the observer to play.
The opposite is true. Mathematics is a tool to derive those conclusions from your assumptions that are actually warranted, that the assumptions logically support. Of course, nobody guarantees you that your assumptions are right: that’s when you derive a consequence that happens to be false in the real world, which you notice through experiment (which is another thing arguing against your idea that our models are just subjectively shaping reality, or whatever it actually is you want to argue—if that were the case, then how come that our models turn out to be wrong, if they’re not confronted with truths independent of them?). Then, you’ll have to re-examine your assumptions, and let go of those responsible for the conflict, and come up with a new model.
Lacking mathematics, however, it is much harder to rigorously derive conclusions; instead, you end up with vague statements that could be interpreted any which way.
I take it you’ve never read a defense of manifold substantivalism against the hole argument…
I’m not sure how far to carry this side-issue here, but I want to note that quite a lot hides in the ‘correspond to’. It’s in fact highly non-trivial how even pictures, or statues, or otherwise ‘direct’ descriptions ‘correspond to’ their subjects. There’s a lot you have to abstract away: material, dimensionality, properties… Where on the one hand, you have a two-dimensional array of tiny semiconductor elements emitting light of various frequencies, on the other, you have a breathing, barking, living being made of blood, bone, muscle and fur. These two things are not terribly alike at all!
It’s just that all of this abstracting away is done on the fly, such that we’re never really aware of it; and it takes some training to notice it at all. But once you do, the question really becomes unavoidable: just how is it that this array of colored dots is so readily interpreted as a dog by us?
This is a hard question, and one where I think that computation isn’t going to give us a satisfying answer. But that’s really probably going to be a leap too far.
That’s another thing entirely, though: performing work in the world isn’t a computational notion, and on the face of it seems much more likely to give us a good notion of how meaning comes into the world. If food makes a dog salivate, and a bell does, too, then it seems just natural that in some way, to the dog, the bell symbolizes food; even more simply, if you hear the word ‘lion’, and it makes you run away, then it seems that in some way the word meant ‘danger’ to you. So maybe meaning is just what symbols make us do? How they make us behave?
It’s an appealing notion, I think, but it’s really hard to keep it from not collapsing into mere physical causality: you end up with the hand tipping over the stone meaning ‘fall over’ to the stone, with the key meaning ‘open’ to the lock. But I find it really hard to believe that stones and locks are the right sort of things to be properly considered as being capable of symbols having any meaning to them.
Furthermore, it’s really hard to explain how we could ever be wrong on such a theory: each of our reactions just is directly caused by a symbol, and if this causation is all there is to meaning, then whatever a symbol causes us to do would be the proper meaning of that symbol. But we’ve all misinterpreted symbols before, i.e. reacted in an inappropriate way to them, so how does that work? What decides which reactions are appropriate?
I’m little bit surprised by that. Obviously the explanations that require a conscious observer for a non-unitary change in wavefunction, whilst technically not disproven are pretty absurd. However it seems to me that in something like MWI it’s difficult to recover classical physics without the observer shaping their own observations in some way.