Searching for Evolutions of Pure States into Mixed States in the Two-State System ${\mathit{K}}^0{\overline{\mathit{K}}}^0$

Oscillations between two quantum states may be a sensitive probe for a loss of quantum coherence due to possible violations of quantum mechanics, e.g., caused by gravitation. We show, for the strangeness oscillations in the neutral kaon system, that there exist four experiments which uniquely determine all nine non-quantum-mechanical parameters that occur in a density matrix description using the Pauli matrix basis.