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Entanglement in scattering processes

  1. Nov 18, 2009 #1
    Dear participants of a forum.

    The phenomenon of quantum entanglement arises only when there is the INTERACTION between two objects of a microcosm.

    However there is a question:

    What is such INTERACTION?

    Whether the scattering matrix is the key moment in such interaction?:

    http://en.wikipedia.org/wiki/S-matrix

    Or the main thing is something another?

    Whether spins of particles should be bindingly antiparallel?

    How I must understand the situation when the both particles have a zero spin ?

    Whether it is bindingly to regard spins of particles in situation of quantum entanglement ?

    Here some resources:

    http://www.iwce.org/fileadmin/IWCE_...nanohub.org/papers/posters/P02-04-Bordone.pdf

    http://arxiv.org/PS_cache/arxiv/pdf/0810/0810.4093v3.pdf

    http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503183v1.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0109/0109045v2.pdf
    http://users.aber.ac.uk/rog/scat.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0506/0506212v1.pdf
    http://arxiv.org/PS_cache/arxiv/pdf/0710/0710.5776v1.pdf
    http://arxiv.org/PS_cache/arxiv/pdf/0712/0712.0014v2.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0607/0607181v3.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0509/0509013v3.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0611/0611230v2.pdf
    http://arxiv.org/PS_cache/arxiv/pdf/0708/0708.2388v1.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0601/0601177v1.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0503/0503131v1.pdf
    http://arxiv.org/PS_cache/quant-ph/pdf/0609/0609217v1.pdf

    Also, dear participants and visitors of a forum, I ask that you excused me - my English is bad. I am from Ukraine.
     
  2. jcsd
  3. Nov 18, 2009 #2

    DrChinese

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    Well, you know that entanglement arises in conjunction with the conservation laws. I.e. conservation of quantum observables. Total momentum, spin, charge, etc. Conservation of these is critical to scattering analysis. So you would expect entanglement in a scattering event, although you won't get the same types of particles out in all cases. The particle count may differ as well. Because of these, your state will have a lot of terms corresponding to the possible outcomes. Trying to actually observe entanglement in that situation is very difficult and in some cases, impossible.
     
  4. Nov 18, 2009 #3
    First of all I should thank you that you have answered my post.

    If you allow, I would like to ask to you some questions.

    You write:

    If it is possible, explain in more details that you have in view of, please.

    Further you write:

    Also I would be very grateful to you if you have explained in more details this moment. What do you mean when you write "particle count"?

    I ask you to excuse me in that case if my questions are naive or I badly translate from English.

    Thanks.
     
  5. Nov 18, 2009 #4

    DrChinese

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    It depends on whether we are talking about high energy or low energy scattering. As the input energy goes up, the output particles can be all kinds of things, as you might expect in a particle accelerator.

    You may have intended to refer to low energy scattering only, in which the scattering is electron-electron or similar. In those cases, there is still conservation so there can be degrees of entanglement. The nature of the entanglement will be a function of what you know about the particles to begin with. If you know starting momentum, you will know ending momentum too (since it is the same) and there will be momentum entanglement.
     
  6. Nov 18, 2009 #5
    Thanks. I figure that your answer is clear for me.

    Now, if you will allow, I would like to ask following questions:

    Whether spins of particles should be bindingly antiparallel?

    How I must understand the situation when the both particles, which are interacting, have a zero spin ?

    Whether it is bindingly to regard spins of particles in situation of quantum entanglement ?
     
  7. Nov 18, 2009 #6

    DrChinese

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    Gold Member

    In scattering, maybe they are always anti-parallel - not really certain as this is not my strong side. They are conserved so the question will usually be: what do you know about input spin?

    As to quantum entanglement: there are situations in which spin is not entangled even though there are other observables which are entangled. So the answer is no. Spin is still conserved.
     
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