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Non-local effects and information

  1. Feb 28, 2007 #1
    Please clarify the following view:
    An EPR-Bell experiment - when one particle in a Bell correlation is measured, this instantaneously affects the properties of the second particle. To me this seems as if information concerning the measured particle has "arrived without travelling" to the second particle. Has an exchange of information occurred in these experiments? ["exchange" may be the wrong word as the information seems to be directed in only one way, however, words like "transmission" or "transfer" imply a movement which does not take place (ie: instantaneous)]
    If all defintions of 'information' imply a "materialistic" cause it may be that the definition has to be changed.
    PS: I must stipulate my layman status so try and keep it "real".
    Last edited: Feb 28, 2007
  2. jcsd
  3. Mar 1, 2007 #2
    Well, where should I begin...

    No one really knows what is happening in those experiments. There are many models (interpretations) that offer their own explanation; some explain it via spacetime (transactional interpretation), some explain it via multiverse (MWI) and so on.

    In some views it would be proper to say "exchange" and "instantaneous", in some it would not.

    For example, when we talk about it in terms of relativistic spacetime, the particle measurement events are separated by a space-like distance. In other words there is no telling which particle was measured first, and the particles don't really move when viewed from spacetime.

    I think it is helpful to look at all the different ways people have explained this phenomenon in their minds, and perhaps try to invent own ways to explain it. At this time it is impossible to choose between different paradigms.

    For one, take a look at:
    and as a related note:

    As you probably know, I don't really believe into the models I am talking about above. But that doesn't mean they aren't true. Suffice to say, Bell correlation is one of the trickiest things to explain in terms of "real motion", while in terms of "static spacetime" it is actually quite trivial.

    (I.e. we should ask ourselves, since when is locality required for realism? This is so only in terms of relativisticspacetime, and if we use relativistic spacetime, Bell correlation is trivially explained without non-local effects)

    I hope this is helpful.

    EDIT: Changed "spacetime" to "relativistic spacetime" to avoid confusion

    Last edited: Mar 1, 2007
  4. Mar 1, 2007 #3
    The Rational Mind seems to work in a 'Newtonian way' (ie:Reductionism may not be a 'discovered' method but a reflection of the properties of Rational Mind), this may be why QM can be so difficult to fathom, because QM does seem to be reaching for the Unified Whole that exists beyond the scope of Rational Mind.
    Once again, thanks for the clarity of the posts you directed me to (although I'm still wallowing out of my depth). In trying to get a handle on non-locality I am going to stick with the Unified Whole view as I find it very helpful. For instance, lets say that in the Unified Whole view, not only do all "things" exist but also all trajectories/connections/relationships (TCR's) between all things. I can now view the two particles in an EPR-Bell type experiment as part of a single system. All information concerning the two particles exists as part of their TCR (their "information thread"). In a Newtonian sense, when the properties of one particle are measured, information concerning these properties "instantly arrives" at the second particle, thus transforming its properties. In a Unified Whole sense, the information exists as part of a single system, so no "travelling" or "arriving" is necessary. The properties noted in the second particle depend solely on which specific aspect on the information thread we have chosen to measure in the first particle.
    Obviously, the system (particles and TCR) does not exist separately from the Unified Whole, this separation occurs when the Rational Mind "decides" to measure (ie: fracture the Unified Whole).
    Please clarify any erroneous thinking on my behalf and forgive any enthusiam I have for the Unified Whole/Fallacy of Identity. I'll be careful not to turn it into dogma.:bugeye:
  5. Mar 1, 2007 #4
    my take on the subject is that the wave function of the two particles exists not only over an amount of space but also over an amount of time. So if you draw a world line of the problem, using the y axis as time and the x axis as space, you'd see a "V" shape as the two particles move away from each other over time. This shape is the wave function I'm talking about. When you make a measurement on one side of the V, the whole wave function collapses and you can know an aspect of the other side of the V. The entanglement spans both time and space, but I've read that you can't send information in this way.
  6. Mar 2, 2007 #5


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    You seem to have introduced something "Unified whole" without defining what it is. Considering that this isn't part of physics, then don't you think it is prudent for you to clarify what you are using?

    Furthermore, your efforts in trying to get a handle on quantum mechanics based on your "familiarity" of classical physics may be futile, especially without understanding the mathematical formalism of it.

    This is rather puzzling. You DO know, of course, that there is a time-independent Schrodinger equation, and a time dependent Schrodinger equation. There is no ambiguity on how the solution to such equations evolve with time.

    Still, this has no relevance to the issue at hand. The world line that is obtained from Special Relativity "appears" to not be relevant in the entanglement phenomenon. That is the whole point of the Bell-type experiments.

  7. Mar 2, 2007 #6
    My definition, such as it may be, can be found on the "Solipsism redefined" thread, post #46.

    I am an out and out layman, and as distasteful as you may find this, am concerned with the philosophical outcomes of QM. My "familiarity" of classical physics pretty much ends with the notion that everything works like a machine and can be broken down to its constituent parts to provide an overview of how the whole works. A view that sadly lacks any capacity to describe such trivial things as "Life" or "Consciousness". As a living, conscious entity, I find myself fascinated by the possibilities, philosophically speaking of course, that QM has opened up. Particularly Uncertainty, as I suspect, philosophically speaking, that this reflects the true nature of the human condition. Aristotle's either/or, true/false paradigm may well be coming to and end, and with it the ability of classical physics to speak of "reality".
    But I may be wrong :bugeye:
    PS: What did you think of the Unified Whole explanation I presented (obviously one of numerous models and without the necessary mathematics). Please try and keep your criticism constructive.:tongue2:
  8. Mar 2, 2007 #7


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    There is a serious problem (and often, absurdity), in any attempt to applying principles of QM into human and social interactions. Postmodernists have tried it with hilarious outcome. It was so bad, that Alan Sokal decided to demonstrate how ridiculous it is using his infamous hoax.

    In all of this, the central message has always been: don't try to applying something that one doesn't understand.

    And with respect to QM (assuming you did not want to read the link I gave you), my assertion has always been that unless one is willing to live by with understanding something just superficially, one will never understand even the fundamentals of QM without actually studying it, and that means the mathematical formalism. There's no shortcut here. "God is in the details", and never more so for QM. In fact, in many academic institutions, majoring in philosophy of science actually requires a candidate to actually take classes in physics, including quantum mechanics. I knew personally of a philosophy major at Columbia University who had to take some of the same undergraduate physics classes as other physics majors. There is just no way around it.

    But again, if you are comfortable with simply applying something that you don't quite understand, or only have a superficial knowledge of it, into other parts, then that's a different matter and it is entirely your business. However, if it is done on PF and you are applying something that is erroneous, then it is still subjected to our global guidelines.

    I personally do not care about yours or anyone else's philosophical beliefs or arguments in here. I do care, however, when physics principles and ideas have be bastardized and chopped up into unrecognizable pieces, which is why I and other mentors have to come in to the Philosophy forums lately and do a major clean up. So I am definitely not here to discuss with you your philosophical ideology.

    Last edited: Mar 2, 2007
  9. Mar 2, 2007 #8

    I have studied Intro to Quantum Mechanics 2nd by David Griffiths in my senior QM course up through ch. 7 (time-independant perturbation theory). I haven't studied this problem since I haven't taken a graduate level QM course. You can solve for the time independant wave function between the origin of the two correlated particles and where they are detected. When you measure one of the particles, you collapse the wave function, and you can know something about the other particle, because the wave function describes the whole system. So far so good?

    What I was trying to explain is that the particles move through space over a period of time, and I intuitively think of them as tracing out a wave function through this span of space and time. If you imagine the wave function collapsing at a finite "speed" (just as to illustrate), you'd see it start to collapse where you made a measurement, and it would collapse down the "V" world line, and back up to the other side, sort of moving back in time to where the two particles are linked and back forward in time (only this time arriving at where the other particle is) to the time where you made a measurement of the first particle. Of course this is very hand waving and intuitive on my part. But that is what I mean when I mention time dependance, I know it's wrong to say they are at specific locations at certain times when you know where they are going to be detected, since that is a bound state, not a scattering state (I think).
  10. Mar 2, 2007 #9


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    Come again? What "wavefunction" is this? From the way I am reading this, you somehow are giving the "wavefuction" a property as if it is a "wake" in response to the motion of the particle. This is not right.

    There's a very simple way to solve this ambiguity. Could you write down the exact wavefunction that you are thinking of that clearly is applicable to this very situation that you are describing?

    But there is no such time dependence! So isn't this all rather moot?

  11. Mar 2, 2007 #10
    It's hard for me to understand without time dependence. For example, suppose you seperated the origin of the particles a half an astronomical unit away from detector a, and an astronomical unit away from detector b. You then solve the wavefunction of the system. Then you do the experiment. You will detect an aspect of the state of the particle heading to detector b before it gets there, since the measurement at detector a collapses the wave function. So in the experiment, the wave function isn't paragmatically time independant is it?
  12. Mar 2, 2007 #11


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    Not in the entangled properties. That's the whole point of the EPR paper and the whole point of the Bell-type experiments! Look at the entanglement of a bipartite system. Do you see any time "evolution" of any kind?

  13. Mar 5, 2007 #12
    Well that would have been my first warning to you :)
    I guess it is easier to remember the dangers of dogmas with this view since it explicitly states all views are just semantically different and none can be considered true to reality.

    There are many ways to understand QM systems, and QM behaviour certainly seems to imply that some particularly sticky assumptions we have intuitively made about reality are false. We just don't know which ones (note how different interpretations each assume a different assumption as the false one... MWI; the assumption that there is just one universe. Transactional interpretation; the assumption that motion is real, etc...)

    Another thing I'd like to note is:

    This sounds like an assumption about consciousness having an effect to the QM system. It is assuming a lot larger role to the rational mind than just to break reality into "sensible components". In fact it is assuming more than the modern version of copenhagen interpretation. Remember that there are some very strange time-wise aspects on quantum systems, regardless of the identity of the "components" we imagine in our minds.

    So if you are saying what I think you are saying, I'd advice to take a good hard look at various quantum systems and thinking about the different views people have taken on those systems, and in particular how certain assumptions about reality constrain the nature of other things (like time) in that particular paradigm.

    Like is the case with time or with any ontological question, there are no trivial answers to be found here I'm afraid...
  14. Mar 5, 2007 #13
    That is very true.
    I'm also thinking that perhaps we should require physicists to take some courses in philosophy... It could make these two fields understand each others better. Right now they are just too far apart for much of a synergy to occur.

    I can totally understand why physicists feel the problem is that philosophers don't understand enough physics, while philosophers feel physicists don't understand enough philosophy.

  15. Mar 5, 2007 #14
    There is no instantanious transfer of information and/or energy.

    If there would have been an instantanious transfer of information, this would logically also mean instantanious transfer of energy (else, how would information be transfered?).

    It is however sufficient to show that no information in the real sense gets transfered, since only after both observers compare notes, they can discover that a change in the measurement apparatus at A correlates to a change in the measurement at B. In the real sense so, no information can be transfered in this way.
    Since you can not compare those notes at superluminal speeds, no real instantanious transfer of information needs to take place.

    What one however needs to "give up" is local realism.
    Local realism is the idea that the full identity (property) of the local particle is somehow "fixed" (ie independend of the other particle of the entangled pair's state). The outcomes of the EPR experiments however mean that no local "hidden variable" theory can explain it.
    Last edited: Mar 5, 2007
  16. Mar 5, 2007 #15


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    Except there is a difference, and this is where I always get into trouble, especially in here.

    Physicists do not need to know any formal knowledge of philosophy to do physics. Philosophers of science DO! In fact, many advances in physics in turn influences many aspect of philosophy, whereas today, physicists can be completely ignorant of what is going on in the formal study of philosophy without making a single dent on their ability to be a physicist.

    So yes, I fully agree that physicists don't understand many aspect of philosophy, or even the philosophy of what they are doing. This is because they don't have to. But can a philosopher afford to be ignorant of physics and about physics?

  17. Mar 5, 2007 #16
    The most obvious assumption to me must be the unified whole/fallacy of identity itself, but only when I try to communicate it. As a personal experience it seems beyond doubt but as soon as I try to define it, it "disappears". Also, I feel that "breaking reality into "sensible components"' does have a genuine effect on the QM system, that it is more than just semantics. I have heard that in some interpretations of QM, when one takes a measurement of a system, that measurement "collapses the wavefunction".
    Is this not a genuine effect of the rational mind on a QM system?
    At the moment I am grappling with 'entanglement' as I intuitively feel this may be the key to 'communicating' the unified whole. Does entanglement exist when we are not measuring a QM system? If so, to what extent?
  18. Mar 5, 2007 #17
    Maybe I'm wrong, but it seems to me that Einstein, Bohr and all the early pioneers of QM became more engrossed with the philosophical implications of QM than anything else, and it was in delving into these philosophical issues that allowed them to come to the understandings they did. Their initial source of confusion seemed to be the fact they were physicists and not philosophers. I doubt that any out and out physicist would have made any headway in the Alice in Wonderland world of QM. You must surely agree that any interpretation given in QM can be considered fundamentally philosophical in nature.
  19. Mar 6, 2007 #18
    Of course not. I am referring to the way some physicists tend to make rather shaky philosophical assertions about reality/ontology. Like assertions about the reality of MWI. Some physicists have a better grasp at philosophy (at epistemology, making them able to see the difference between mental/physical models and reality), and this often makes them able to also formulate new and potentially more accurate models.

    Einstein, for example, needed fairly good grasp at philosophy before he could toy with the idea that simultaneity may not be objectively "real" phenomenon, but just something we tacitly assume to be so. He was probably helped a lot by having read Hume.

    And also the same grasp at philosophy makes you able to see that relativity of simultaneity is also a way to handle the situation in one's own mind, in that it includes assumptions that are not observable. What we do observe is such a topology of spacetime (events) that would be explainable by relativity of simultaneity, but nothing says this is ontologically correct; i.e. nothing says if in reality there are such things as "simultaneity planes" in any sense or if they are only abstractions.

    So, you are quite right in that a physicist doesn't need much philosophy to be able to make their job, but then they must also remember that their job is not so much to produce ontological assumptions about reality, but rather to produce valid models (valid in that they make correct predictions). Ontological interpretation of that model cannot be done with shaky understanding of philosophy (each interpretation of QM is ontological claim), yet too many physicist do. See what I mean?

    Most certainly not.

  20. Mar 6, 2007 #19
    This is just one way to express the situation. It should not be taken as an ontological claim. Bohr and Heisenberg were necessarily vague about what it means to measure the quantum system. It should not be taken as a literal claim about consciousness collapsing the wave function (although you can interpret it that way and people tend to; too readily in my opinion).

    What "collapses the wave function" has been developed further since but we don't have any final answers; different paradigms don't even talk about it in terms of wave functions.

    If you are toying with the idea that when the mind classifies reality into sensible objects it changes the system that is being observed, you must be able to explain how and why we should expect it to be so. There exists some material about this, but it is problematic view because we don't know what consciousness is.

    It depends on what is meant with entanglement. Usually it is just referring to the way some part of the system is affected by earlier state of another part of the system (and vice versa), and if you look at that in terms of "wave collapse", it makes quantum systems seem pretty strange indeed.

    In my opinion it is precisely the bell correlation that needs to be explained first, and its explanation will naturally also say something about the reality of "wave functions".

  21. Mar 6, 2007 #20


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    But you seem to be forgetting that they were physicist first, and then, after QM came into existence, they battle the meaning of it. No one would accuse any of them of not knowing the physics they were discussing intimately.

    On the other hand, many philosophers, and certainly those who want to discuss these stuff on here, only know of the physics they're discussing superficially. There's a big difference.

    Finally, practicing physicists do not need to go into "Alice in Wonderland" world at all to function and make progress in physics. Even Feynman would say "Shut Up And Calculate". For the majority of physicists, the philosophical interpretation or implication doesn't even come into play at all. Just go, for example to the APS March Meeting that is going on right now this week. It is the largest yearly gathering of physicists anywhere in the world. I will put it to you that 99% of the presentations there (and there are thousands of presentations at one of these) have absolutely nothing to do with anything dealing with philosophy.

    The mathematical formulation will be the same whether you call it Blue, Green, Indigo, etc... The problem here is that people who want to talk and discuss it in here, don't even know the mathematical formulation. They only know about the Blue, Green, and Indigo.

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