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Does quantum entanglement allow information to travel faster than light?

  1. Jun 21, 2011 #1
  2. jcsd
  3. Jun 21, 2011 #2

    DrChinese

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    No. It "seems as if" random results (i.e. no useful information) are transmitted instantaneously, but this is not the only interpretation possible.
     
  4. Jun 21, 2011 #3
    even though no information is transmitted faster than light,something must be transmitted,what is it?
     
  5. Jun 21, 2011 #4

    DrChinese

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    The nature of the observation and the result.
     
  6. Jun 21, 2011 #5
    does that mean the observation and the result traveled backwards in time,because anything that travels faster than light has to deal with time travel backwards.
     
  7. Jun 21, 2011 #6

    DrChinese

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    If you say so. :smile:

    Actually the result can appear to travel backward in time. Still doesn't allow you to communicate any faster.
     
  8. Jun 21, 2011 #7

    Drakkith

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    That depends on your interpretation of quantum mechanics.
     
  9. Jun 21, 2011 #8
    so the result violates causality?from what i understand if something were to travel backwards in time it would violate causality,but i might be wrong and im all ears.
     
  10. Jun 21, 2011 #9
    are you talking about the copenhagen and many worlds interpretation?
     
  11. Jun 21, 2011 #10

    Drakkith

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    I'm not sure honestly.
     
  12. Jun 21, 2011 #11
    so does quantum entanglement travel faster than light or not?
     
  13. Jun 21, 2011 #12
    Nothing travels from A to B simultaneously over very large distances. The objects where already connected, even before anyone observation on its wave function. Determinism solves this EPR problem beautifully.
     
  14. Jun 22, 2011 #13
    at what point does the entanglement allow to travel backwards in time?
     
  15. Jun 22, 2011 #14
    Here's my take on the thing.

    A particle pair is created. The particles, according to a quantum description, have "opposite spin". According to "conceptions" of the particle description if you apply a magnetic field to one of the particles it will reverse it's spin. As particle pairs always have opposite spin we assume that the other particle will have opposite spin. No matter how many times we apply a field and "reverse" its spin the other particle will have opposite spin.

    No matter how far the two particles are from each other or how many times we hit one of them with a magnetic field they have opposite spin when we "observe" them. When we "make" a "particle pair" and "flip one of their spin" we actally do "observe" them both to have opposite spin"

    The reason I use quotation marks above is that those terms refer to analogies we use to describe activities of particles according to conceptions we have of them. They also refer to extentions of analogies to predict certain actions and the actions that are observed under the terms of the conceptions. This "particle pair spin" relationship results in extensions that imply somthing is happening that, according to some conceptions, is faster than light but according to others is not. But it's such a poorly understood field that we can't say or describe in conclusive or even consistant terms what is happening. Though not conclusive or consistant some are convincing. Convincing enough that the most advanced studies institutions fund hundreds of billions of dollars studies of them.

    To whit.

    Lets say that we make a pair and send one of the pair to Alpha Centari. At a time agreed upon by a person here and an observer there we apply a magnetic force to our particle of the pair and then check the spin. The observers can know the information of what the spin of the particle on earth is faster than light could send it. But it is not meaningful information because they didn't know what the spin was was before they observed it.

    Lets say they knew the spin before the test time. If the spin was left and it is still left after the test that would mean stay if it was right that would mean come back. The sender of the command would simply either apply a field to flip the spin or not depending on the information, the command, he wanted to send. That would be meaningful information. You could send billions of such particles and use it as a digital or even morse code transmitter. Can't do that unless you know what the spin was before the test.

    But something happened that sent "information", of a sort, that we can't access usefully. What could it be?

    Consider the conception that the particle pair is somehow connected. Say by a wire connected to both north poles. If you point both north poles up the particles are spinning in opposite directions. If you point the north poles towards each other they are spinning in the same direction. The wire between them is also spinning in the same direction. So the two particles and connecting wire can be taken as a single rotating unit. Like a pair of wheels with an axle between. If you rotate one wheel in one direction the other wheel rotates in the same direction. If you change the direction of rotation of one whele the rotation of the other changes too.

    But what is the nature of this "axle"? It can't be a connection in normal space abiding by rules we think are very iron clad. It wouldn't be able to transmit the rotation information faster than light. A normal axle couldn't do it with a normal set of wheels.

    Then we concieve of this "axle" or "wire" weaving "around" "space" somehow. It solves the problem. But then what is the nature of this "other space"? It is a conception to cover "observations" interpreted in the light of other "conceptions".

    That's not all that can be said about it. Some people are comming up with some interesting "conceptions" that treat for this and many other things. M theory for instance, multiverses, parallel universes and time travel of several flavors are some of the unconfirmed "implications" of some "conceptions".
     
    Last edited: Jun 22, 2011
  16. Jun 22, 2011 #15

    Drakkith

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    Entanglement only causes FTL if you take the view that the two particles communicate with each other instantly when they interact. In this view the entangled particles are not in a set state. When one is measured the other one instantly knows about it. Not only that, but it seems that even when one particle is measured AFTER another particle, it can still affect the other particle even though it was measured first. It seems that the particles communicate through time. However I must point out that all this is highly dependent on a specific interpretation of Quantum Physics.

    One of the other views is that the entangled particles are pre-set to their states upon being generated or initially interacting. In this case there is no communication between particles and no FTL. However, I believe that current evidence does not support this view very well.
     
  17. Jun 22, 2011 #16

    Drakkith

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    Are you sure about this? I thought that once you altered the state of one particle the two were no longer entangled. For example, if two electrons are generated and each must have opposite spins, then if you measure them you will find that they always do. But if you do something so that one of the particles gets their spin flipped, then the entanglement is broken. After the interaction both electrons could be spin up or spin down depending on what you did.
     
  18. Jun 22, 2011 #17

    DrChinese

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    Entangled particles remain so despite spacetime separation. When the entanglement collapses (whatever that is), it does so instantaneously and therefore defies normal spacetime constraints (i.e. c). So quantum collapse is FTL.

    It is not clear when collapse occurs. There is no observation possible to discern such state. Partial collapse is possible too.
     
  19. Jun 22, 2011 #18

    DrChinese

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    It is not possible to unambiguously interpret the situation as being "the future causes the past" but it is a possibility. I think a better description is: The results are randomly based on the context, and the context consists of both past and future components. It you can find causality in that statement, great, but I don't see it.
     
  20. Jun 22, 2011 #19
    Interesting...... can you please give an example (or link to a paper) of a partial entanglement collapse?

    I went through a previous discussion, on this forum, and papers cited however there was not much.
     
    Last edited: Jun 22, 2011
  21. Jun 22, 2011 #20
    Has this been experimentally verified? If so can you post a reference please.
     
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