Kaonic Qubits
  Quantum mechanics can also be tested in high energy physics; in particular, the neutral kaon system is very well suited. We show that these massive particles can be considered as qubits --kaonic qubits-- in the very same way as spin-1/2 particles or polarized photons. But they also have other important properties, namely they are instable particles and they violate the CP symmetry (C...charge conjugation, P...parity). We consider a Bell inequality and, surprisingly, the premises of local realistic theories require strict CP conservation, in contradiction to experiment. Furthermore we investigate Bohr's complementary relation in order to describe the physics of the time evolution of kaons. Finally, we discuss quantum marking and eraser experiments with kaons, which prove in a new way the very concept of a quantum eraser. 
Reinhold A. Bertlmann and Beatrix C. Hiesmayr