We observe violation of a Bell inequality between the quantum states of two remote Yb ions separated by a distance of about one meter with the detection loophole closed. The heralded entanglement of two ions is established via interference and joint detection of two emitted photons, whose polarization is entangled with each ion. The entanglement of remote qubits is also characterized by full quantum state tomography.
@article{arxiv.0801.2184,
title = {Bell inequality violation with two remote atomic qubits},
author = {D. N. Matsukevich and P. Maunz and D. L. Moehring and S. Olmschenk and C. Monroe},
journal= {arXiv preprint arXiv:0801.2184},
year = {2008}
}