Science Now today reports on a transitive photon entanglement experiment by Eli Megidish, Hagai Eisenberg, and colleagues at the Hebrew University of Jerusalem in which they show that two photons can be entangled even when they do not exist at the same time. Entanglement is explained by the conservation of energy, and their experiment suggests that this conservation does not have to be in an instant point.
They first create a pair of entangled photons 1 and 2, then they produce a second pair 3 and 4. Then they perform a "projective measurement" on photons 2 and 3, which entangles them. The entanglement property (polarization) of photon 1 is measured, which destroys it. When the entanglement 2, 3 is created after 1 has been measured, 1 and 4 have never coexisted at the same time as an entangled pair. By later measuring 4, the experiment shows that 1 and 4 are entangled.
In the middle, the article states correctly, that entanglement cannot be used to transmit information faster than the speed of light, but in the last paragraph this fact is contradicted. In reality, entanglement can be used to determine if a cipher has been read, but it cannot be used to transmit ciphers.
Link to the article: Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time