Analysis of critical parameters in the scheme of Bj\"ork, Jonsson, and   S\'anchez-Soto
  Bj\"ork, Jonsson, and S\'anchez-Soto describe an interesting (gedanken-)experiment which demonstrates that single photons can indeed lead to effects which have no local realistic description. %It is one of few cases where the experimental falsification of the conjecture of local realism has been done with use of the CH inequality, rather that the CHSH inequality. We study the critical values of parameters of some possible features of a non-perfect realisation of the experiment (especially photon loss, which could be looked at as the detection efficiency), that need to be satisfied so that the experiment can be considered as a valid test of quantum mechanics versus local realism. Interestingly, the scheme turns out to be robust against photon loss. 
Marcin Wiesniak, Marek Zukowski