 One of the main avenues of approach employed entangled ions. The use of ions looked very promising, since for such experiments detection efficiency is very high. The experiment of Rowe et al. (2001) employed beryllium ions, observing a CHSH inequality violation \(S = 2.25 \pm 0.03\) with a total detection efficiency of about 98%. Nevertheless, in this set-up the measurements on two ions not only were not space-like separated; there was a common measurement on the two ions. More recently, the distance between ions was increased. For instance, Matsukevich et al. (2008) entangled two ytterbium ions via interference and joint detection of two emitted photons, with the distance between the ions set to 1 meter. However, a conclusive experiment of this sort that eliminated also the communication loophole would require a separation of kilometers.