"What has Bell's theorem to do with the absence of antimatter in our universe?"

John Stewart Bell was known and hired as a "particle physicist" when he came up with his work on hidden parameters exactly 50 years ago. The aim of this talk is to discuss whether his theorem can be brought back to those systems that do not build up ordinary matter and light, i.e. to the domain of Particle Physics. Indeed, massive K-meson pairs are copiously produced at accelerator facilities that are entangled in their strangeness quantum number, i.e. being in the particle or antiparticle state.

Entanglement and its manifestations reveal differently than in quantum systems of low energy [1]. In particular, it turned out that there exists a connection between the violation of Bell's inequality and the tiny violation of the CP symmetry (C...charge conjugation, P...parity). The broken CP symmetry, verified in various accelerator facility experiments, shows a small difference between a world of matter and a world of antimatter. This relates two different powerful toolboxes in physics, entanglement and symmetries in Particle Physics. 

Moreover, the discovery of CP violation, also exactly 50 years old, can be attributed to the unsolved problem why we live in a universe dominated by matter, i.e. why has antimatter disappeared?

In the last part of the talk I show that these meson-antimeson systems are a unique laboratory to study foundations of quantum mechanics, e.g., for testing different kinds of quantum eraser schemes or decoherence models or collapse models [2].

[1] Hiesmayr et al., "/Revealing Bell's Nonlocality for Unstable Systems in High Energy Physics/", EPJ C, Vol. 72, 1856 (2012).

[2] Brahami et al., "/Are collapse models testable with quantum oscillating systems? The case of neutrinos, mesons, chiral molecules/", Nature: Scientific Reports 3, 1952 (2013).