Testing foundations of Quantum Mechanics in Particle Physics

Full text: Particle physics has become an interesting testing ground for questions of foundations of quantum mechanics. Entangled massive meson-antimeson systems are specially suitable as they offer a unique laboratory to test various aspects of particle physics (CP violation, CPT violation,...) as well to test foundations of quantum mechanics, e.g. Bell inequalities, decoherence effects, quantum marking and erasure concepts, Bohr's complementary relation. The main aim of this talk is to show that these systems not consisting of ordinary matter and light provide novel insights into quantum theory. Particularly, we show that a certain Bell inequality is related to the observed tiny difference between matter and antimatter, the so called CP violation explored in particle physics. Herewith two different powerful concepts in physics, entanglement or its manifestation and symmetry, become related. Then we show a Bell inequality sensitive to the quantum number strangeness, which is not violated for the maximally entangled spin singlet state, but surprisingly for a non-maximally entangled state. This opens for the first time the possibility of a direct experimental. We will shortly discuss the status quo of the realization with the upgraded KLOE detector (DAPHNE machine, Italy). In summary, understanding the nature of entanglement and its manifestation needs also studies of entanglement at different energy scales and as recent works show there are still many open questions concerning entanglement, e.g. about high dimensional genuine multipartite entanglement or of relativistic entanglement of massive spin 1/2 particles. (author)