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The discussion revolves around a user's inquiry on how to start a new thread on Physics Forums, specifically regarding quantum math for entangled states. The user seeks guidance on the platform's interface for posting questions, mentioning a specific interest in quantum nonlocality and a key paper on 3-photon GHZ entanglement. They express confusion about the derivation of a particular equation related to the paper and request assistance with the vector-algebraic steps involved. The user has already found the process to create a thread in the Feedback forum and aims to replicate it in the appropriate section for physics discussions. The thread highlights the importance of clear navigation for new users on academic forums.
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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!

Thanks!
 
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It's the same process in every forum. You found how to do it in the Feedback forum. Replicate that process in another.
 
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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