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Post by mrsonde on Nov 7, 2013 19:50:10 GMT 1
Seems a little slow around here. I've been recently discussing the subject I was discussing before my sabbatical (I can't be bothered to dig it out) on another board. Someone mentioned this experiment, which is one of a large variety now of such experiments, all confirming the original conjecture - Bell's - but this one has the merit of being particularly clear and, more to the point, fruitful for the superluminal communication idea I mentioned earlier. There are a couple of minor errors in this exposition; but no matter, in this context, because they're not really germane. The salient thing is that "which-path" information can potentially be obtained and erased without collapsing the wave function. That is to say, it is now demonstrated beyond any question that it is not the detecting apparatus that collapses the probability amplitude distribution into actuality, as has often been argued in explications of the standard double-split experiment, for example. This would have astonished even Bohr. It's worth emphasising this point. In the experiment above an interference pattern is registered at Ds, even though the photons concerned have passed through macroscopic apparatus that, potentially at least, is able to give information on which slit they have passed through. According to Bohr, this shouldn't be possible - the passing through the quarter wave plates would necessarily collapse the wave function, and therefore no interference pattern would appear. But it does, (unless we actually obtain information about the photons' polarisation before hitting the QWPs.) Rather than the rather confused exposition linked to above, consider that the polariser on path p is oriented fully to completely block a left or right polarisation. We now potentially know the orientations of the s photons, and therefore which slit they will pass through. The interference pattern at Ds will disappear, therefore. As this exposition points out, it is not necessary to actually know which photons have been blocked and which passed by the polariser for this to occur - the mere potentiality of being able to find out if we wanted to is enough. The s photons are "marked". The other essential aspect to this set-up to point out is that the coincidence counter plays no effective role in the apparatus. It's there purely to solve the almost insuperable technical problem of eliminating extraneous electromagnetic pollution in the laboratory. Suppose this technical problem is overcome, as it surely can be with adequate resources, labour, and conditions. Now, if we cut the coincidence counter out, and instead of the laborious method of detection described we simply use photosensitive screens as our detectors Ds and Dp, so that a photon "hit" permanently lights up its incident pixel, we would see the interference pattern at Ds appear in situ (or not, as the case might be.) So - without the polariser on path p, we see an interference pattern on Ds. Put the full polariser in position, and the interference pattern disappears, as we now have available information on which slit the s photons must pass through. This is the case whether the path to the polariser is shorter or longer than the path to the QWPs. The s photons seemingly change their behaviour - pass through both slits, or only one slit - according to what we decide to do "in the future". It could be any number of years in the future, if we made the paths long enough. Now suppose that Ds and Dp are separated by light years - say, Ds is on a distant planet, Dp is here on Earth. We generate our entangled photons and send one (the idler) around a circular or back-and-forth mirrored path, while its pair, (the signal), gets sent off to the receiving planet. On that planet is an identical apparatus doing exactly the same, sending a signal entangled with its own home idlers in our direction. After the required amount of time needed for these photons to arrive - here and there - we interrupt our idlers' roundabout path and place our polariser in its way. As conclusively proven in the above experiment, this will give accessible which-path information (it is irrelevant whether this has been actually determined or not, as observation - the potential, its observability, is all that is required) when our interlocutor on the distant planet passes our signal through the QWP and double-slit apparatus described above. In turn, we pass the signal that we receive from the planet through our own QWP and double-slit apparatus; and our interlocutors similarly place a polariser of their own in the path of their idlers to reduce our detected interference pattern. This appearance and reappearance of the interference pattern on our detecting screen happens instantaneously - the moment the distant planet operators put the polariser in place. Whatever the distance involved. We can communicate instantaneously, faster than light. Interference pattern = 1. Clump pattern = 0. We can of course send and receive any information in this manner - text, pictures, video, holograms. Potentially, one distant day, the information necessary to construct a clone - Star Trek teleportation (as has already been done with Cesium and Rubidium atoms, incidentally.) So - what is wrong with this? The standard objection in the literature is that such signalling is not information: for it to be so, we would have to also communicate which photons we have measured (determined the polarisation of, in this example) and which we haven't, and we can only do that by the usual means of light-speed signalling. But clearly in this set-up this is not necessary at all. This post is long enough, so I'll leave the mind-boggling implications of this vis-a-vis Relativity until later. For the moment, consider this: if this superluminal communication device is possible, what would happen if the distant planet was in, say, Andromeda, and hurtling towards us with a constant relative velocity? Always has been, mind - no one's accelerated. We can talk instantaneously. We can see a video image, in "real time" so to speak, of their clock, and they can see our clock. We can see a video of them seeing a video of our clock, alongside their clock, and vice versa. Relativity theory demands that both our clocks are running slow in respect to the other. What sort of video image would that be?
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Post by mrsonde on Nov 21, 2013 1:58:33 GMT 1
I'm a little disappointed that no one seems interested in this topic. Perhaps we should change the title of this board, in case we mislead any newcomers. Then again, I'm not too surprised - the same thing happened on a very well-populated Physics board I frequent, and on another board which is more philosophically oriented, and hence considerably more intelligent and well-informed.
Let me briefly outline the objections that were raised there, then, in case you're thinking there must be some catch here. It was asserted that my claim that the coincidence counter plays no effective role is mistaken - it was asserted in both places that this instrument is indeed crucial, and that without it the interference pattern would never disappear. Hence superluminal communication is impossible, because both transmitter and receiver would have to collate their signal and idler photons, and the only way they can do that is by light transmission in the usual manner.
The response to that is simple. If knowledge of the correspondence between the entangled pairs of particles is the crucial issue, place the coincidence counter halfway between the communicators, and let them transmit the necessary information. There is now absolutely no difference between this situation and the experiment conducted, as described. Thus the interference pattern will appear immediately (or not) long before the light signal conveying the information of which photons are which have ever arrived at the counter.
I say this with a little hesitamcy, I admit, because I don;t think any experiment has ever been conducted to confirm it - due to the photon pollution already mentioned. And we are, after all, in very bizarre territory, where we can no longer trust intuition.
But if we suppose that the interference pattern would only appear, or disappear, once the two communicating planets had sent information about the detected photons to the halfway counter, then we would have to suppose that an interference pattern we observed, say, a couple of years ago (if, say, the halfway counter was two light-years away), would suddenly change to a clump pattern - or vice versa. And that surely is too fantastical. Isn't it? A photo you took two years ago suddenly changes because of a calculation made two light-years away? That's not physics, it's magic.
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Post by principled on Nov 21, 2013 3:40:24 GMT 1
Mr S I have to admit that things have been a bit slow on this board since the summer and the number of science issues very small. However, I think you should carry on posting. I intend to respond once I've had time to study your posts in more detail (ie after I return from my grandparent duties overseas!) P
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Post by mrsonde on Nov 21, 2013 20:44:11 GMT 1
Mr S I have to admit that things have been a bit slow on this board since the summer and the number of science issues very small. Ahhh, nanotechnology eh? Verrrrimteresting. I try, mr.p. I try. Sometimes the struggle and the terrible responsibility is soooo heavy and wearing, though...sometimes I think, why not just let you all cary on vegging out to your Brittany Spears albums and Miley Cyrus videos? Who am I to interfere with your harmless pleasures? Well, it better be good then, that's all I can say, after a build-up like that. I wasn't really asking anyone to cross the Atlantic to talk to me, even though, you know, you really should. Get your priorities straight before you spoil those ghastly grandchildren any further.
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Post by abacus9900 on Nov 28, 2013 10:49:08 GMT 1
mrsonde, I agree that this experiment challenges our conventional ideas about time and space and probably indicates that there is another level of reality underlying our spacetime model, which is the orthodox position of the current scientific establishment, but having said that, how does one not only produce a theoretical framework within which to accommodate such experimental results but also, and more crucially, produce laboratory tests that are repeatable confirmation of such a paradigm? Anything less than this is philosophy, not science.
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Post by abacus9900 on Nov 28, 2013 11:23:38 GMT 1
principled, the experiment that mrsonde is referring to seems to indicate that, within the special experimental set-up in question, an 'observer' seems to be able to affect the outcome of an event in the present by effectively "going back in time" by making a conscious decision to erase the history of a sub-atomic particle. To me, this seems to indicate that it is observers that partly, at least, construct what we would colloquially call "the here and now." Of course, it is a very big leap to translate what has been found to be the case in a special experimental situation using quantum objects directly to the macro world of objects such as beach balls, people, planets, stars and so on, but, nevertheless, theses bizarre results have yet to be satisfactorily understood.
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Post by principled on Nov 28, 2013 19:37:25 GMT 1
Abacus, thanks for your enlightening post. At the moment you could say that I am in an area built entirely on the effects of Quantum Mechanics...Silicon Valley. But my sojourn ends tomorrow, so I'll soon be back home looking out of my window and seeing rain rather than sun. That'll give me the incentive I need to stay inside and study the experiment Mr S posted. I suspect, though, that I'll have more questions than answers! Or as Johnny Nash sang ... www.youtube.com/watch?v=GEstgTAXyecP
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Post by abacus9900 on Nov 28, 2013 20:25:31 GMT 1
Abacus, thanks for your enlightening post. At the moment you could say that I am in an area built entirely on the effects of Quantum Mechanics...Silicon Valley. But my sojourn ends tomorrow, so I'll soon be back home looking out of my window and seeing rain rather than sun. That'll give me the incentive I need to stay inside and study the experiment Mr S posted. I suspect, though, that I'll have more questions than answers! Or as Johnny Nash sang ... www.youtube.com/watch?v=GEstgTAXyecP You are welcome, principled, and what a delightful coincidence we are discussing the physics of the incredibly small and you are in an area that happens to be one of the main centres that that makes practical use of the weird and wonderful world of the sub-atomic. Hope you return refreshed.
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Post by mrsonde on Nov 30, 2013 5:25:29 GMT 1
mrsonde, I agree that this experiment challenges our conventional ideas about time and space and probably indicates that there is another level of reality underlying our spacetime model, which is the orthodox position of the current scientific establishment, but having said that, how does one not only produce a theoretical framework within which to accommodate such experimental results but also, and more crucially, produce laboratory tests that are repeatable confirmation of such a paradigm? Anything less than this is philosophy, not science. I find this post somewhat confusing, abacus. Could you help me out a little by explicating what you mean in a little more detail? Are you saying that the standard model demands something underlying space-time? Or you're referring to the extra dimensions of string theories, perhaps? Well, these experimental results are of course entirely predicted by the standard interpretation of quantum mechanics - Copenhagen plus Bell. The theoretical framework is there already. Not my elaboration described - that's emphatically denied, in every formulation I've ever seen at any rate (I believe the scenario I've described avoids all objections so far put forward on theoretical (mathematical) grounds - AFAIK of course) principally because it contravenes (seemingly at least) a fundamental axiom of relativity theory. The paradigm you mean is...? The standard interpretation of QM? Many laboratory tests have confirmed this, as I'm sure you know. The one linked to above is merely one of at least a dozen or so, as far as Bell's Theorem goes. I suspect you must mean an interpretation of QM that would explain these results, rather than merely predict them as a mathematically necessary consequence of the "theoretical framework." That is, you're asking for a philosophical explication of the mathematics and what they mean in terms of the way the world works, rather than merely their descriptive implications which is all that physics demands. Is that right? Fine by me, if so - but just so we're clear and on the same page.
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Post by mrsonde on Nov 30, 2013 5:45:19 GMT 1
principled, the experiment that mrsonde is referring to seems to indicate that, within the special experimental set-up in question, an 'observer' seems to be able to affect the outcome of an event in the present by effectively "going back in time" by making a conscious decision to erase the history of a sub-atomic particle. To me, this seems to indicate that it is observers that partly, at least, construct what we would colloquially call "the here and now." That's a very interesting way of putting it. The standard (the physics community's) way of phrasing it would be that the "history of the sub-atomic particle" didn't exist until it was observed. Not erased - created. Also - consider that another way of formulating the result would be the reverse of your construction: not the observer affecting the present by "going back in time" but the particles "being aware" of what happens "in the future". But note my parenthetical remark in my post - these results have been achieved in the laboratory with Cesium and Rubidium atoms - certain properties of such, at any rate. These aren't sub-atomic particles. They are, however, "quantum objects", as far as the "theoretical framework" of QM goes: as, indeed, are beach balls, people, planets, and the entire universe. If the scenario I've outlined is indeed implied by this experiment (and I cannot see how it cannot be: it's an identical scenario, in effect and construction) then it's not just these results that need a philosophical explanation. It means the standard philosophical explanation of Special Relativity (as given explicitly by Einstein) is fundamentally wrong. The standard model is wrong - not just lacking a philosophical explanation (giving a "satisfactory understanding"), but scientifically misinterpreted. Time is constant and absolute, simultaneity is constant and absolute, and not determined by inertial reference frames at all (except in the appearances necessarily limited by the speed of light signals.)
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Post by mrsonde on Nov 30, 2013 6:11:58 GMT 1
I'm not quibbling here. The two formulations are fundamentally different, metaphysically - and, as I've described above, would lead to very different observational results. You take a photo of your pixel screen at Ds, recording either an interference or a clump pattern, depending on how you orientate your polariser before Dp. That photograph exists, in the form of silver chloride particles or whatever. Then, in the suggested scenario I've outlined above, you send your photon arrival information to your coincidence counter, halfway between the two planets, so you can compare which particles are entangled with each other. According to the standard objections to superluminal communication by this method published so far, this information is supposedly required before your interference pattern can disappear. But once you have it, it will - as proven by this and other experiments. The theoretical framework demands, therefore, if these objections are correct, that your photograph - taken years before, perhaps - must change from interference pattern to a clump. As I say, I'm almost certain that these objections therefore can't be right. But it is my intuition that makes me feel so sure; and that is no longer any guide to certainty at all, if it ever was. In case you're thinking: obviously, it's not the photo taken years ago that would change, nor the appearance of the screen photographed at the time; it's merely the appearance of the screen in the present, once the information from the coincidence counter has been received: this is not what this and other experiments like it show. Or, at any rate, it is not how they are always interpreted - because they are of course always interpreted a la Copenhagen. Knowledge or as in this experiment the availability of knowledge of the state of the entangled particle collapses the state of its pair. Either this is wrong, or SR is wrong. As I say, the experiment to determine absolutely which has yet to be conducted - but it can only be a matter of time.
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Post by mrsonde on Nov 30, 2013 6:24:59 GMT 1
Let me anticipate the obvious objection to this either-or: SR can't be wrong, because it's been confirmed experimentally. We know that a moving clock will run slower when in relative motion to a "stationary" one: we've confirmed it over and over, in jet aircraft flying around the Earth, in particle colliders, and so on. Haven't we?
No, we haven't. All these experiments have always confirmed the time dilation effects of accelerated motion. General, not Special, Relativity.
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Post by abacus9900 on Nov 30, 2013 10:26:02 GMT 1
I tend to lean towards the idea that experiments are really an interaction between mind and matter and that the only reality is that who's potential has been 'crystallised' by some observer, whether at the level of an amoeba or human being or beyond. I think this is why quantum processes seem so strange to us - they are completely novel situations that have been designed by scientific researchers, so that we have to confront the possibility that such experimental results do not show us a pre-existing reality that is simply sitting there waiting for us to stumble across it, no, I think we actually create novel realities via our ideas. It is because of this that the various interpretations surrounding experiments like the EPR or double slit have been so contentious, i.e. that there is no pre-existing reason to account for them since they are essentially artifacts of human intellectual activity. When Galileo looked through his telescope, all he had to assist him was his own perceptions with which to make observations but nowadays science has to use special instruments to serve as an extension of our senses and it is this that has given rise to a new level of organisation of what we term "reality." The conclusion I take from all this, then, is that it is not so much what is passively waiting "out there" for mankind to discover but more that it is a dynamic process between mind and matter that discovers organizations that "work" and it is, therefore, futile to keep speculating about "hidden" realities that give rise to such organizations. For example, who can show me a bit of "curved space?" Curved space is not like a piece of rock in the sense you can touch it or weigh it or feel it; curved space is a concept that has been constructed in order to make mathematical equations work and so, in the same manner, the world of the incredibly small is only real insofar as it adheres to our mathematical patterns of thinking about it, which brings us back to "mind" and matter.
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Post by mrsonde on Dec 1, 2013 15:41:45 GMT 1
I tend to lean towards the idea that experiments are really an interaction between mind and matter and that the only reality is that who's potential has been 'crystallised' by some observer, whether at the level of an amoeba or human being or beyond. The obvious objection to that interpretation of QM is: what constitutes an "observer"? Some level of sense registration is clearly implied by this term, if not "consciousness". That being so - how does such a sensory registration apparatus arise, if nothing exists prior to its creative capability? Historically, that isn't true. There was nothing novel about an oven, and no one designed black-body radiation. Can you think of a single piece of evidence to support this idea? How do you account for the element of surprise - of falsification - if this idea were true? But those previous contentions have now been settled, haven't they? By experiments. By objective data. Then you need to account for how such "objective data" arise, or seem to arise. Ermmmm...okay, sort of. But it's no longer a purely mathematical curiosity, is it? Applying it to objective reality leads to definite material implications, which can be confirmed or falsified by actual observation - the orbital perturbation from Euclidean flat space of the orbit of Mercury, for eaxample, or the deviation from straight of light passing the Sun as observed by Eddington in 1919. Objective data, no? I think there'd be more traction in this suppostition had it been what actually happened, historically. But in actual fact - an important notion your philosophy entirely overlooks, it seems to me - the observations came first, then the mathematical patterns.
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Post by abacus9900 on Dec 1, 2013 18:58:28 GMT 1
In a word: complexity.
Clearly, an earthworm hasn't got the mental capacity to grasp a scientific theory, although is does have the ability to sense certain aspects of its environment developed by evolutionary processes.
Well, here again, would an earthworth or, indeed, a dog be able to be aware of this observation? Obviously, the answer is no, so when you use the term "novel" it is only because human thought has the capability to create patterns of thought that seem to be consistent and predictable to human perceptions that we no longer consider such things as novel. Perhaps some other creatures who have evolved in a drastically different environment from us would look at the same phenomena differently.
Falsification is the process of discovering new patterns of thought that appear to "work" better than the prevailing paradigm but you could argue these would never actually come into being without human cogitation.
Well, if you mean the formal way experiments are conducted to reproduce consistent outcomes, yes, however, it is the deeper meaning of such outcomes that are subject to various implications, none of which are currently verifiable and I fully accept that we are currently at the stage of philosophising about such matters, but everything begins with philosophy.
The question is: can we really say objective data has an existence completely independent of conscious observers!
Indeed, and I fully admit that the concept of curved space, gravity, and so on, are labels used for our consistent experience of interacting with the observable universe. Having said that, one can always argue that something else exists behind it all that we have yet to discover, so inevitably, all our scientific theories about reality are necessarily out of date.
Of course. Observations were happening long before formal mathematics came about.
As a footnote, I don't wish to convey the impression the the intellectual achievements of mankind are trivial, far from it, however, we must always bear in mind that the way humans think is determined by the architecture of a biological brain that has been shaped by the powerful pressures of evolutionary survival so we are compelled to model what we perceive in our environment on the way our brain's biochemical processes dictate, albeit within a very flexible platform.
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