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More entanglement fun

  1. Aug 30, 2012 #1
    Q1: If every atom has to adjust their energy levels according to every other atom in the universe, does that mean that any given single atom has its interior invaded by a catalog of energy states from every other atom in the universe? And only after accounting for all the energy states that have already been taken, then find a unique one?

    Q2: How can the spin states of two particles be measured 100's of miles apart when they trypically will interact with other particles almost immediately, for example in the pair creation of an electron and positron for the test system?
  2. jcsd
  3. Aug 30, 2012 #2
    Is Q1 inspired by the statements in Brian Cox's book and tv lecturs? If so, there is some relevant discussion here and on the physics stackexchange here
  4. Aug 30, 2012 #3


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    Particles can easily remain entangled even after interacting with other particles or fields. The question is whether the interaction collapses the state (at least in some basis) and in many cases that answer is no. For example, a magnetic field can alter the path of a charged particle without affecting its spin. If it was spin entangled before, it would remain spin entangled.

    For photons: they can go through fiber cable and be twisted and turned without yielding any information about their polarization. Again, if it was polarizationentangled before, it would remain polarization entangled.
  5. Aug 30, 2012 #4


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    You'll notice they don't do this, of course. Every hydrogen atom in the universe has the same ground state energy, and each electron happily occupies its ground state without obtaining permission from the other ones! That's because they are different states: (ground state in atom 1) is a different state from (ground state in atom 2), and so the overall wavefunction has no trouble being antisymmetric.
  6. Aug 30, 2012 #5
    Thanks for the reply's gang.

    That makes more sense to me, and yes I was talking about the Brian Cox show but I also found it here: http://www.youtube.com/watch?v=0x9AgZASQ4k&list=PL04722FAFB07E38E1&index=16&feature=plpp_video
    These guys, though, seem to be saying explicitly that each atom has an entire catalog of every atoms energy state in the universe, and there's no budging on that. Am I reading this wrong?
  7. Aug 30, 2012 #6
    I guess my confusion is well-shared. I've been reading the Brian Cox thread. Very animated. Thanks for the lead Sheaf.
  8. Aug 30, 2012 #7


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    Confusion can be contagious.

    Regarding the youtube video, note that "DrPhysicsA" is a professional musician, whose only current involvement in physics is producing this series of videos. The present one is legit until the 10 minute mark, at which point it takes off.

    Try looking up "EPR Paradox" in Wikipedia. DrPhysicsA follows this discussion word for word, but then arrives at the wrong conclusion. Scroll down to where the article says "Here is the crux of the matter" and see if you can spot the difference.
  9. Aug 31, 2012 #8
    Really? Brian Cox is a professional musician too! Maybe they should start a band called "the disentanglements" and write a song that clears up their shared miscommunications. I sure would like to hear it.:tongue:Yuk Yuk
  10. Aug 31, 2012 #9
    in what way are the ground states different? .....even though they have same energy levels....
  11. Aug 31, 2012 #10


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    They're located in different places. A state is characterized by its wavefunction ψ(x,t), and this is different depending on where the atom is.
  12. Sep 1, 2012 #11

    ....lol... good joke !
    The Dissentanglements !!!
  13. Sep 3, 2012 #12
    Thanks, physics humor doesn't get any nerdier than that.
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