EPR-Bell Correlations in Particle Physics

Research project P 14143 EPR-Bell Correlations in Particle Physics Reinhold Anton BERTLMANN 24.01.2000 There is especially in the 90ties enormous interest in testing entangled quantum systems which exhibit Einstein-Po dolsky-Rosen-B ell correlations. Such correlations point to a fundamental nonlocal aspect of quantum physics. In quantum optics the fast development led to a new discipline: quantum information technology. Similar research is certainly of high interest in particle physics, ideal massive quantum systems are the entangled K0 K0 pairs produced at the -factory DANE and the very heavy B0 B0 pairs produced at the B-factories, e.g. at SLAC and KEK. We want to contribute with our research project to this new and fascinating development in physics. Basically, we intend to investigate the following aspects of the quantum system. * Bell inequalities and nonlocality: Several types of Bell inequalities are constructed and applied to the K0 K0- systems and B0 B0 -systems. * Violation of CP-symmetry and Bell`s locality hypothesis: CP-violation is related to a violation of a Bell inequality, the case of the B-mesons is studied in detail. * Time evolution of the quantum system: A modified von Neumann equation for the density matrix is investigated that allows for dissipative effects, specific models are considered. The time evolution of an entangled state is studied close to the measurement process. * Interference effects and deviations from quantum mechanics: The decoherence parameter method is used to measure deviations from quantum mechanics, a bridge to specific local realistic models is constructed. We perform a kind of interdisciplinary research of quantum mechanics and particle physics. The new and innovative aspects can be seen in our systematic appproach to investigate EPR-Bell correlations for massive quantum systems, to discover their general features and to find their relevance to physics.

Quantum phenomena can not be explained by the conceptions of classical physics. They are radically different. Especially, the discussion of Einstein-Podolsky-Rosen about the features of an entangled two-particle system points to the paradoxical features - EPR paradox - of quantum mechanics. John Bell showed by his famous inequality how local realistic theories and quantum mechanics differ from each other and triggered in this way a whole series of theoretical and experimental investigations about entangled quantum systems. It has led to a new development in physics, namely to quantum information and quantum communication. We have investigated in our research project entangled systems in particle physics such as entangled K-meson or B-meson pairs which are produced at the big particle colliders. We have constructed general Bell inequalities showing the non local aspect of the quantum systems and we found a method to distinguish the entangled from the separable states. Furthermore, we could relate the CP symmetry of the K-mesons to Bell inequalities. One of our main tasks was concerned with the study of the time evolution of an entangled system. We allowed for dissipative effects leading to decoherence of the system, i.e. deviations of quantum mechanics. As a result we found a direct connection between the decoherence and the entanglement loss of the system and we also could derive bounds to the validity of quantum mechanics from the experimental data. With our research project we could contribute to the interplay between the phenomena of particle physics and the recent developments in quantum physics.