In entanglement swapping: If we detect photons 2 and 3 in the following states |135>|45> or |45>|135> (accompanied by the appropriate coincidence counts), do we project photons 1 and 4 into the same bell-state (so photons 1 and 4 are also found in either |135>|45> or |45>|135>)? How would we write this four photon GHZ state in terms of |V> and |H> polarisation? Would it be |H>|V>|H>|V> (+ OR -?) |V>|H>|V>|H>? http://en.wikipedia.org/wiki/Bell_state We have a list of the four bell states. Taking the first, do we expand as: |A>|B> = |0>|1> + |1>|0> ? Which would be |H>|V> + |V>|H>?