 Historically, the efforts toward a detection loophole-free experiment followed two main paths, though a few other possibilities were also explored. One of these other possibilities involved K,B mesons (Selleri 1983, Go 2004), where the detection loophole reappears in another form (Genovese, Novero, and Predazzi 2001); and another involved solid state systems (Ansmann et al. 2009).