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Is entanglement swapping instantaneous? Suppose photons 1 and 2 are entangled. And, 3 and 4 are entangled. A Bell-state measurement (BSM) is performed on photons 2 and 3 to cause entanglement swapping so 1 and 4 are now entangled. Was the entanglement of 1 and 4 instantaneous (right when the BSM was performed)?

I believe this question is different than others like Does entanglement have a speed or is it instantaneous. I am asking about the swapping action.

glS
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user3141592
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    There's no need to mention entanglement here. You can ask the more general question: in quantum mechanics, does a measurement cause an instantaneous change of state? The answer is yes. – WillO Jan 02 '21 at 20:34
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    Swapping is just teleportation of one half of an entangled state. So the samw story applies as for teleportation. – Norbert Schuch Jan 02 '21 at 21:09

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