Entanglement swapping between photons that have never coexisted.

@article{Megidish2013EntanglementSB,
  title={Entanglement swapping between photons that have never coexisted.},
  author={Eli Megidish and A. Halevy and Tomer Shacham and Tom Dvir and L. Dovrat and H S Eisenberg},
  journal={Physical review letters},
  year={2013},
  volume={110 21},
  pages={
          210403
        }
}
The role of the timing and order of quantum measurements is not just a fundamental question of quantum mechanics, but also a puzzling one. Any part of a quantum system that has finished evolving can be measured immediately or saved for later, without affecting the final results, regardless of the continued evolution of the rest of the system. In addition, the nonlocality of quantum mechanics, as manifested by entanglement, does not apply only to particles with spacelike separation, but also to… 

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