Spooky or not spooky, that is the question.

Discussion in 'Physics & Math' started by quantum_wave, Jan 27, 2016.

  1. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Thanks. The issue of "spooky" that is often interpreted as part of the laws of Quantum Mechanics, leaves one wondering if we have to say that there is no mechanistic explanation? Or instead, are there natural laws that govern the mechanics of how everything works together?

    I suggest you watch the video I posted in another thread.
     
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  3. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    I linked the Intro to Superposition lecture because in the second half of the video, the instructor shows an experiment that is the quantum superposition of paths of a single electron. This is definitely spooky and I don't see how anyone can deny that. Quantum superposition is a very different beast than our normal ideas of superposition.

    From http://ocw.mit.edu/courses/physics/...pring-2013/lecture-notes/MIT8_04S13_Lec01.pdf:

    Did it take the hard or soft path individually?
    That cannot be, as the output in either case is half white and half black.
    Did it take both?
    That cannot be, because the electron can always be measured to travel on one path or another and not on both at the same time.
    Did it take no path at all?
    That cannot be, because putting in both walls removes all output.
    What the heck is going on? What we are facing is that for all electrons in the apparatus, the route they take is not an individual path, not both paths, and not no path at all. There do not appear to be any other logical possibilities, so what are they doing anyway?

    If the experiments are accurate and the arguments correct, the electrons are in fact doing something we have never dreamed of before and for which we do not at the moment have any words. Electrons have modes of moving or modes of being, which are unlike anything we have discussed thus far. This is also true of molecules, bacteria, and other macroscopic objects, though the effects are harder to detect. Physicists call such modes as being defined by superposition, which for now means “we have no clue what is going on”.

    If the experiments are accurate and the arguments correct, the electrons are in fact doing something we have never dreamed of before and for which we do not at the moment have any words. Electrons have modes of moving or modes of being, which are unlike anything we have discussed thus far. This is also true of molecules, bacteria, and other macroscopic objects, though the effects are harder to detect. Physicists call such modes as being defined by superposition, which for now means “we have no clue what is going on”.
     
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  5. brucep Valued Senior Member

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    Thanks for that link. I remember when I was reading QED, by Richard Feynman, he said you can derive QED from the results of the two slit experiment. QED models the superposition as a sum over all paths.
     
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  7. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    745
    Feynman was a great educator as well as a scientist. I have not read QED since when it was a new book. I should go back and read it again. I got the impression from his video lectures that he had some small skepticism that this sum over paths mechanic (as QW calls things) was what was really happening, and that it was only a method that worked. I could be wrong about that.

    The experiment with the color and hardness boxes is I think called the Mach-Zehnder Interferometer, in case you want to look it up.

    David Deutsch has a very good explanation of the experiment from the quantum computing viewpoint. Most people don't like his Many Worlds interpretation, but this video (horrible quality) is very well done explanation for laymen and goes through the math involved. The most interesting statement in the video is where he explains that there is no classical computation that can replicate the results of the experiment. There is no classical analog of the process. And therefore we can't really understand it except as mathematics involving complex numbers.

     
  8. brucep Valued Senior Member

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    I should watch all the videos. Seems like I do better reading. Probably because I like to stop constantly and make sure I'm getting it. LOL. He may have said that in the book also. Most likely I'd guess. I'll link this project that Professor Edwin F. Taylor put together to teach Feynman's QED model as an introduction to QM. It's pretty cool but when I downloaded it we were still using floppy discs. There's a workbook plus all the software for analyzing paths. The last time he updated the software download was in 2000 but it looks like you download and then can run it from your desktop. I think LOL.
    http://www.eftaylor.com/quantum.html
    Did you ever read the three posts, written by mr_homm [Professor Stuart Anderson], on the the choices of Heisenberg and Bohr? I learned so much from those three posts. Especially about choosing coordinates to do the analysis. For QM. And how the Hilbert space is used to model the physics on. But I have no real training on QM. LOL. I remember having an epiphany over some of the details of his discussion. Professor Anderson must be a wonderful teacher. That's the 'deal' with Professor Taylor also. He told me he was'nt an authority on General Relativity. I didn't get it then but later I realized that his mentor on gravitational physics was Professor John A. Wheeler and the other great gravitational physicists who have written text on the subject. The only reason, I can think of, is that his commitment to intellectual honesty guides him. When he told me that I couldn't find my ass with either hand. As far as I was concerned, then and now, is he is an authority. LOL.
     
  9. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    745
    David Deutsch has written a popular science book called The Fabric Of Reality, but I have not read it. Also, it seems that many people are put off by his belief in the Many Worlds model of QM. I can understand why that is. But to me Many Worlds is just another way of saying we don't really know or understand what is going on. David Deutsch's main area of expertise is quantum computing. He has a website where you can find links to his papers, articles and multimedia presentations. I am not promoting his ideas but I do find them interesting.
    http://www.daviddeutsch.org.uk/

    Thanks for the EFTaylor QM link, I will check that out. I found the link to the mr_homm posts and will add those to my TODO pile. Sounds interesting. I may print them so I am read them on the commute tomorrow.
     
  10. brucep Valued Senior Member

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    mr_homms posts are basically the best interpretation I've come across. He doesn't call it an interpretation or intimate it might be. That's how I interprete it. LOL. He just wanted to share his thoughts with other posters. Wished he was still available to read. I kinda view the interpretations somewhat like I view choice of coordinates for doing the analysis. So I imagine Professor Deutsch is using the Many Worlds interpretation to help us understand the physics he's trying to teach us.
     
    Last edited: Feb 3, 2016
  11. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    I agreed that it was spooky. Every paper, article, and video on the topic includes some acknowledgement of the fact that quantum mechanics is spooky, and/or that we don't understand the mechanics of it. In the introductory lecture, which is a link you gave me a few years ago, btw, he talks about two independent properties of electrons and refers to them as color and hardness. What he doesn't tell the class at the time, is that the measurements are done with Stern-Gerlach devices which measure the spin of an electron along one axis, with the result being either up or down.

    In the experiments that he describes in terms of color and hardness, if you reference the Stern-Gerlach experiments associated with each property, you are measuring spin up or spin down along one or the other of two different axes. On one axis, call it the color axis, spin up is white and spin down is designated black. On the other axis, call it the hardness axis, spin up is hard and spin down is soft.

    The spooky thing is that an electron has two independent states when it comes to spin on an axis. The details of his experiments demonstrate those experimental results, confirming the spookiness of two independent properties of spin along two different axes; most people agree that it is "spooky".

    If we knew the natural laws in effect, and the mechanics at work that result in the dual spins, it wouldn't be spooky, it would be understood quantum physics.

    Do you agree that there are might be invariant natural laws that govern the mechanics of how all things work, and that if we knew the proper laws and their mechanisms we would be able explain away the spookiness?
     
  12. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    Something along those lines. Maybe QM is entirely correct and it's a matter of finding the right mathematical techniques for renormalizing General Relativity within the given framework, in which case you can readily add gravitons to the picture without any fuss. Maybe QM is only an approximation and there's a more detailed underlying set of physical laws such as those described by String Theory, which could have implications for all the particles we do and don't know about in practice. Whatever theory replaces QM however will have to look virtually identical to it at the appropriate scales, just as Quantum Field Theory can be used to recover Schrodinger's mechanics, Special Relativity and Newtonian mechanics at the appropriate scales.
     
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  13. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    745
    To your first question I would say yes. There MIGHT be "invariant natural laws that govern the mechanics of how all things work." But that does not mean we can know or understand them. And of course there MIGHT not be. My mind is open on the subject but for right now I am highly skeptical.

    To your second question I would say not necessarily. For instance, the Many Worlds model can be an explanation but that does not explain away the spookiness. All of the current explanations seem to remain spooky. Spookiness is just the idea that the way things work do not match to how our experience teaches us how things work. To some extent spookiness can be educated away. For instance at one time the idea that the Earth is spherical was unacceptable and spooky. But to day we deal with the fact in our everyday lives and it is no longer spooky. The spherical earth is now part of our experience. The theories of SR and GR are still spooky to many, but many others have accepted them through education (or maybe they learned to ignore the spooky nature). Whether the spookiness of Quantum Mechanics can be educated away is a question I can't answer. My suspicion is that it can't be because it is just so very different than anything we can ever directly experience. It even has its own separate logic. That is very far away from our experience.

    My question to you is, do you believe that these invariant laws of nature that cause the spookiness to disappear, will reveal a deterministic world where free will is a lie? If we know how these currently hidden variables processes work, does that lead to the idea determinism? Just curious.
     
  14. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    No, I don't. Here is why. The "deterministic universe" solution to QM is an alternative that I most often see offered from the Copenhagen Interpretation perspective. It says that you cannot have local reality unless either you accept FTL, or perfect determinism at the expense of free will. It ignores the solution that I am talking about which we can call the "incompleteness solution" of the Hidden Variables Interpretation. "Determinism" with its no-free will conclusion doesn't seem to be offered as a viable alternative, but instead, offered because no free willed individual would accept that alternative, leaving only the two other proposed solutions, non-locality or FTL communication between particles. They want you to pick one of those. I prefer to go with the HVI concept that QM is incomplete.

    In regard to the content I have posted about the actual experiments and devices, did you understand what I was saying in the OP, about if Alice always chose the vertical orientation for testing, and how that would establish complete accuracy in her prediction of the orientation of Bob's particle polarization, each time she got a particle to pass her filter?

    Also, did you agree with my description of the "boxes" in the video you posted, i.e. that they contain Stern-Gerlach type devices set to measure the spin of each particle on one of two axes? On one axis, up and down are given colors white and black, and on the other axis, right and left are given hardness as in hard and soft? Did you understand that was the means of measurement when you viewed the video? Would you agree then that the physics at work is what ever causes the independence of two spin axes, and what causes the electron on a given axis to respond in a specific way, up/down for example, to a focused magnetic field?
     
  15. CptBork Robbing the Shalebridge Cradle Valued Senior Member

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    No, you're getting completely mixed up here. The Bell experiments show that you can't have "local reality", period. Nonlocality is now a demonstrable feature of nature, which means the universe is either a deterministic one where faster than light signals are exchanged, or a non-deterministic one where long-distance spacelike correlations are possible without violating Relativity.

    Physicists don't care much about free will one way or the other when drawing their conclusions. Determinism eliminates free will by postulating that everything that will ever happen has already been pre-determined by events of the past. Quantum mechanics and other probabilistic theories eliminate free will by requiring that every event occurs with a frequency that matches some well-defined probability distribution. Adding more variables and postulates to quantum mechanics will neither rescue free will nor local reality unless they come at the expense of correctly predicting the results in Bell experiments.

    Electrons only have one physically meaningful axis of spin at any given moment. Whatever you do to measure an electron on one axis will affect the results when subsequently measured on any other axis, which is what makes Bell experiments possible in the first place.
     
  16. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    Yeah I understand how the experiment works. I am not sure you do. If you take an electron and detect it in the magnetic field, you don't really measure the spin. What you are doing is setting the spin to the orientation of the detector. The electron may of may not emit a photon. So rather than measuring the spin of the electron all you are doing is extracting a single bit of information, emission or non-emission. For instance, if the electron emits a photon, then all you can really say is that the electron was not aligned exactly with the detector. It might have been anything from 180 degrees off to off by 1 millionth of a degree (if you were really unlucky). The probability that an electron will emit a photon depends on the angle, where zero probability is exactly aligned, a probability of 1 is exactly 180 degrees out, and 0.5 (aka uncorrelated) is at 90 degrees, etc. If you take a large number of electrons an prepare them by detecting them in the detector, then if you detect them all in a detector of the same orientation, you will detect zero photons. If you reverse the magnetic field, you will detect 100% of the electrons emitting photons, and if you change the detector to be at 90 degrees, you will detect a half of the electrons emitting photons. Detecting a large number of electrons that were all prepared in an single orientation unknown to you would give you as much info info as you could ask for statistically about how far off they were in that one axis. The angle you are off in that one axes is encoded in the number of photon over the number of electrons detected. It tells you nothing about the other 2 axes. But detecting one electrons does not really give you much info, almost none. You get a single bit but it does not convey hardly any real info about the orientation of spin.

    Also interesting is that if you entangle 2 electrons and detect them, then one will emit a photon and the other won't. You still don't know much about the electrons. In fact, if you were lied to and told the electrons were entangled but they were not, then you only have a 50% chance of telling that the electrons were not entangled (up up or down down). If one emitted and the other didn't (up down or down up) then you would not be the wiser. Its just chance. But the most interesting thing about entangled electrons (for me anyway) is that in order to try the famous experiment where you show the complimentary spin for entangled electrons with detectors far away from each other, you have to first exchange the info of what the orientation of the detectors is. You want them to be in the same direction to the smallest error you can get. So a 3D vector has to be first agreed upon though a back channel of classical information. The actual measurement gives you hardly any spin info at all. You don't know what the spin was, but you know that one emits and the other does not. So all this talk about FTL communication is mostly wrong. The only spookiness is that the spin is always correlated when the way it works looks mostly random.

    I did not understand you argument against determinism. But lets drop that, it is not relevant. Sorry for mentioning it.
     
  17. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    The context of my statement was a response to the question posed by Cheezle, i.e., "My question to you is, do you believe that these invariant laws of nature that cause the spookiness to disappear, will reveal a deterministic world where free will is a lie? If we know how these currently hidden variables processes work, does that lead to the idea determinism? Just curious."

    But I hear you, and are you forgetting that there is a difference between a Hidden Variables Theory, and the Hidden Variables Interpretation of QM? The Bell experiments only exclude hidden variables theories that can be tested under the postulates of QM. A Hidden Variables Interpretation (HVI) says that those postulates are incomplete.
    There in lies the bone of contention. If the postulates are changed and presumably made more complete, it would be a different set of postulates. Then the hidden variables theories that would be testable given the newly established postulates might include local relativistic causality without determinism.
    The experiments described in the video show that there are independent measurable states that they called "color" and "hardness", where the spin will be up or down, or right or left, depending on the orientation of the measurement device. If you measure the spin on one axis, it is repeatable, and if you then measure the spin of the same electron on a different axis, the result of the second measurement will always be random.

    The Hidden Variables Interpretation comes from the position that what you may think is the end of the story, is in fact incomplete. If you disregard that possibility, we may never agree about the possible future of QM. Exploring the possible nature of particles, internal composition, wave-particle duality, new theory, etc. is in the future that I envision.

    I have no reason to believe that there aren't invariant natural laws that govern it all, and that would make it all explainable mechanistically. Do you have any reason to believe that is not true?
     
  18. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Please note that the electron can be measured with the device in any orientation, and the magnitude up or down, or any detection at all, will vary with how dead-on the orientation is to the actual axis of spin and magnetic moment producing the measurement. The lecture you posted refers to just two axes that are perpendicular to each other, giving rise to my understanding of there being two independent properties, one for each of the two axes of spin being measured, i.e. color and hardness.

    I think that the talk about white and black, and hard and soft, all centers on how the electron acts when measured by being passed through the "box", which I understand is equivalent to the Stern-Gerlach measuring device. It acts by being deflected up or down by the magnetic field; or left or right, depending on the axis and orientation. That Is my take on what the video says, but you and others may have a more complete understanding.
     
  19. Cheezle Hab SoSlI' Quch! Registered Senior Member

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    745
    The MIT lecture is using an analogy of course. There are (I suspect) a few reason for this. One is that he did not want the students bogs down by the language used in quantum mechanics which can be confusing. For instance quantum spin is not the same as the spin of a top or a ball. There are some similarities, but the ideas should not be confused. He chose color because black and white are binary where spin is a more analog type idea.

    Also he did (I suspect) not want to have to go into the differences between photon polarity and electron up/down. The two different detectors give different information about spin. Polarity is vertical vs horizontal, and up/down is ... well, up/down. A polarizing filter is a sheet with (obviously) 2 dimensions, say X and Y. The electron detector uses a magnetic field which is oriented in one dimension, call it Z. This means that the polarizing filter transmits a photon (1) at an orientation of 0 or 180 degrees, and blocks transmission (0) at 90 and 270 degrees. At 45 degrees it transmits 50%. The electron detector detects up (0) at 0 degrees, and down (1) at 180 degrees and 50% at 90 degrees.

    It is important to realize that detecting a single photon or electron does not give vert/horz or up/down info in a binary sense. It only gives a binary 0/1. The photon could be polarized at 89.99 degrees almost exactly horz and pass through giving a "measurement" of vertical even though it was almost exactly horz. And the electron likewise can give a down "measurement" even though it is almost but not quite exactly up. The results involve probability which is what the quantum realm is all about. And hence Einstein's frustration, "God does not play dice."

    So these detectors are not going to give you much information about spin from a single detection. But if you take a large number of electrons with the same spin, and detect them singly or all at once, you can get a fairly definite idea of their orientation Z vs XY. It does not give you any X vs Y info. But this aggregate information being more useful is related to why in everyday life the quantum information is rendered as real information. A basketball's position and momentum are much better defined than a photon or electron. Basket balls are composed of large numbers of particles and therefore render into our reality with (almost) definite properties.

    Also important, when you detect a particle it becomes what David Deutsch called sharp. It is less spooky. When you detect the electron you set it to "up", and it is then definitely up. You can run the detector over and an over on that electron and it will always give an up result (no emission). If you then allow the electron to interact with other matter it will become not sharp and more spooky again. In the Deutsch experiment the beam splitter takes a sharp or well defined photon and changes it to an unsharp single photon that is traveling through the device in a way that is not to the right, and not up, and not both and not neither. It is very spooky. But the second beam splitter makes it sharp again and no longer as spooky. The mirrors in the device are quantum logical NOT transformations. So the system is B*NOT*B = I and no real world classical B has this property. Beam splitters are spooky devices.
     
  20. PhysBang Valued Senior Member

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    Classical systems can reproduce quantum logic using hidden variables.
     
  21. Fednis48 Registered Senior Member

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    This is a common misconception, and it's worth correcting. Bell's theorem, in and of itself, has nothing to do with quantum mechanics. It takes none of the postulates of QM as assumptions, and its implications are not restricted to "hidden variable theories that can be tested under the postulates of QM." Bell's theorem basically takes three postulates: 1. causality is local (usually in the relativistic sense, although this is not required), 2. the universe is describable in terms of real properties that obey the rules of cause and effect, and 3. scientists can choose measurement settings in a way that is uncorrelated with the properties of the objects they're measuring. From these postulates and a bit of math, Bell's theorem puts a limit on the correlations between spacelike-separated measurements. Experiments show correlations that exceed these limits, so one of the three postulates must be wrong. Bell's theorem is generally associated with QM because QM inspired these experiments, but the conclusion can be reached without ever invoking QM.

    Any one of the three postulates of Bell's theorem can be dropped, and physicists have considered all three:

    1. Maybe FTL causality is possible in certain, restricted ways. This is the idea behind such hidden variable theories as pilot wave theory, in which every particle has an instantaneous, causal connection with its spatially extensive pilot wave.
    2. Maybe the underlying features of the universe are so exotic that they don't even fit our usual definition of "real properties". This is the essence of the "shut up and calculate" Copenhagen interpretation.
    3. Maybe even pseudo-random measurements of particles are necessarily correlated with the states of the particles. This is superdeterminism, and it's a very extreme form of denying free will; I'm not sure if Cheezle's discussion of free will was related to this.

    The most important part, though, is what's not one of the options: "The postulates of quantum mechanics are incomplete." Even if true, that would not help us get around Bell's theorem, because nothing about Bell's theorem relies on QM being correct. That's my biggest objection to your models, as I understand them; they seem to be both local and realistic, which makes them necessarily wrong regardless of whether they go beyond QM.
     
  22. quantum_wave Contemplating the "as yet" unknown Valued Senior Member

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    Thank you for correcting that, and for refuting everything I have always believed in, lol. I like to keep working on my layman level understanding, and to overcome a natural resistance to FTL "communication" between particles, while discounting the possibility of the kind of super-determinism sometimes mentioned as an alternative.

    As I stated in post #3, I believe that there are many invariant natural laws that are as yet unknown, or unexplained, and that there are natural mechanistic explanations that make everything work together without anything that is supernatural or inexplicable in the end. I wouldn't expect such a set of laws to be so exotic that they can't be thought of as real properties though.

    According to the rules, it has not been quite appropriate for me develop my layman level, science enthusiast model of cosmology here in the Science section. Nevertheless, sometimes a thread like this, about some particular interesting aspect of it, helps toward evolving my personal views out on in the Fringe.

    You are right, that my model does feature local relativistic causality, a mechanistic view where nothing is ultimately spooky. I find that many members hold a different view, not embracing the idea of an invariant set of natural laws that all work in unison, and instead accepting a natural inexplicability. To my way of thinking, that just means that something supernatural is invoked instead, though it might be that their opinion is simply that the human mind cannot grasp the nature of reality. What do you think?

    It is also not encouraging to hear you refute the Hidden Variables Interpretation which is based on the laws of quantum mechanics being incomplete, but I have always been aware that there are many who agree with you, and I rarely find someone who agrees with me. Thanks for your learned views, and your opinions.
     
    Last edited: Feb 4, 2016
  23. PhysBang Valued Senior Member

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    SR & GR do not forbid spacelike correlations.
     

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