Interpreting photon correlations from independent sources

[javisot20]

A question,

1- We start from 4 photons totally independent of each other, respecting MoE we entangle 1&2 and 3&4

2- We perform a swap between 2&3 producing non-local entanglement between 1&4, which also respects MoE

3-We delete all the information from the process


Can we know the entanglements now?
Can we know the entanglements at the beginning?

(I ask if by making new swaps and entanglements we can answer those 2 questions)

 

[Morbert]

A question,

1- We start from 4 photons totally independent of each other, respecting MoE we entangle 1&2 and 3&4

2- We perform a swap between 2&3 producing non-local entanglement between 1&4, which also respects MoE

3-We delete all the information from the process


Can we know the entanglements now?
Can we know the entanglements at the beginning?

(I ask if by making new swaps and entanglements we can answer those 2 questions)

Not sure what you mean by delete all information from the process. If you mean some quantum eraser event, that would be impossible as the registering of coincidences is irreversible. If you mean we throw away/don't look at the 4-fold coincidence result and hence don't discard any runs, then no correlations will be observed whether or not the quarter-wave plate was on or off.

 

[javisot20]

If you mean we throw away/don't look at the 4-fold coincidence result and hence don't discard any runs, then no correlations will be observed whether or not the quarter-wave plate was on or off.

In that context. The experimenter loses all data (and memory). Could I get that information with new swaps/entanglements?

 

[PeterDonis]

In that context. The experimenter loses all data (and memory). Could I get that information with new swaps/entanglements?

No, because all of the photons no longer exist after they are measured. If you throw away the information from those measurements, you've thrown away all the information there is about those photons.