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  1. Feb 23, 2012 #1
    My first use of Physics Forums.
    I have a question not addressed so far, as far as I can tell.
    It's in the area of quantum math for entangled state.

    But I cannot figure out how to ask it!
    Is there a "new thread" or "new question" tab anyplace?
    Is there a menu item for new threads or new questions? If so, where.

    In case this is the place, here is my question.
    Interested in recent tests of quantum nonlocality in 3-photon GHZ entanglement.
    Looking at key paper by Pan, Bouwmeester, Daniell, Weinfurter & Zeilinger in Nature, 403, 2 Feb 2000, p. 515-518.
    Key equation is for entangled 3-photon GHZ state; their equation (1):
    |Ψ⟩=1/√2 〖(|H⟩〗_1 |H⟩_2 |H⟩_3+|V⟩_1 |V⟩_2 |V⟩_3); no problem here.
    Then the experiments introduce optical devices to rotate polarization and induce circlual polarization; equations here are (their (2) and (3):
    Pair (2): |H/⟩ =1/√2 |H⟩+|V⟩) and |V/⟩ =1/√2 |H⟩+|V⟩)
    Pair (3): |ʘR⟩ =1/√2 |H⟩+i|V⟩) and |ʘL⟩ =1/√2 |H⟩-i|V⟩)
    This looks like simple vector trig in a unit circle.
    Now they solve (1) above with (2) and (3), and they arrive at their equation (4):
    |Ψ⟩=1/2 〖(|ʘR⟩〗_1 |ʘL⟩_2 |H/⟩_3+|ʘL⟩_1 |ʘR⟩_2 |H/⟩_3 +|ʘR⟩_1 |ʘR⟩_2 |V/⟩_3+|ʘL⟩_1 |ʘL⟩_2 |V/⟩_3).
    My question: How did they get to (4)? What vector-algebraic (?) steps did they use?
    I know a little about Dirac notation, wave functions, etc, but not enough to see how equation (4) was derived.
    Please help if you can!

  2. jcsd
  3. Feb 23, 2012 #2
    It's the same process in every forum. You found how to do it in the Feedback forum. Replicate that process in another.
  4. Feb 23, 2012 #3
    Got it: So now it's in 2 places, but I guess not harm. Please see in Physics, Quantum mech. area
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