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 circluar polarization; equations here are (their (2) and (3): [ʘR=right-handed circular polarization, etc.] 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). (I spread it out into 4 lines to make it easier to read.) My question: How did they get to (4)? What vector-algebraic (? or other) steps did they use? I'm guessing it's some form of substitution. I know a little about Dirac notation, wave functions, polarization, etc, but not enough to see how equation (4) was derived. Please help if you can!