Entanglement between photons that never co-existed
E. Megidish, A. Halevy, Tomer Shacham, Tom Dvir, Liat Dovrat, H. S. Eisenberg · 2012
We entangle two photons, with the first detected even before the other is created, by using entanglement swapping between temporally-separated polarization-entangled photon pairs. This result shows the nonlocality of quantum mechanics in spacetime.