We analyse the recent claim that a violation of a Bell's inequality has been observed in the $B$--meson system [A. Go, { \em Journal of Modern Optics} { \bf 51} (2004) 991]. The results of this experiment are a convincing proof of quantum entanglement in $B$--meson pairs similar to that shown by polarization entangled photon pairs. However, we conclude that the tested inequality is not a genuine Bell's inequality and thus cannot discriminate between quantum mechanics and local realistic approaches.
Categories: quant-ph hep-ph physics.optics