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

1. Jun 24, 2013

San K

entanglement between particles that do not coexist (at the same time)

In the paper by eisenberg et. el.

http://arxiv.org/abs/1209.4191

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. Jul 4, 2013

San K

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