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Entanglement between particles that did not coexist (at the same time)

  1. Jun 24, 2013 #1
    entanglement between particles that do not coexist (at the same time)

    In the paper by eisenberg et. el.


    Photon 1 and 2 are entangled.
    Then 1 is measured, say spin up. The measurement, naturally, "destroys" photon 1.

    Then at a (slightly) later time an entangled pair of 3 & 4 is created.

    Then photon 2 is entangled with photon 3.

    Photon 1 and 4 are considered to be entangled when 2 is entangled with 3. This is known as entanglement swapping.

    However 1 was destroyed. Thus it became determinate (say spin up) at the time of destruction.

    In entanglement, as we know, the particles are in an indeterminate state (before measurement).

    Question 1: Is 4 in an indeterminate state (while assumed entangled with the destroyed 1) when 2 and 3 are entangled?

    Question 2: if we did a separate experiment where photon 2 was measured and lets say it came spin up. (and there was/is no photon 1 in this experiment).

    Then 2 was entangled with 3 (which is currently entangled with 4),

    what would the spin of 4 turn out to be on measurement? .......in this case/experiement
    Last edited: Jun 24, 2013
  2. jcsd
  3. Jul 4, 2013 #2
    information on destruction of a photon

    is information, not-necessarily, considered extracted/gleaned/taken when a photon is destroyed?

    ....in the case of standard entanglement or entanglement swapping or any kind of entanglement....
    Last edited: Jul 4, 2013
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