Entanglement, Bell Inequalities and Decoherence in Particle Physics

Abstract

We demonstrate the relevance of entanglement, Bell inequalities and decoherence in particle physics. In particular, we study in detail the features of the ``strange'' $K^0{\bar{K}}^0$ system as an example of entangled meson--antimeson systems. The analogies and differences to entangled spin--1/2 or photon systems are worked, the effects of a unitary time evolution of the meson system is demonstrated explicitly. After an introduction we present several types of Bell inequalities and show a remarkable connection to CP violation. We investigate the stability of entangled quantum systems pursuing the question how possible decoherence might arise due to the interaction of the system with its ``environment''. The decoherence is strikingly connected to the entanglement loss of common entanglement measures. Finally, some outlook of the field is presented.

Comments: Lectures given at Quantum Coherence in Matter: from Quarks to Solids, 42. Internationale Universitätswochen für Theoretische Physik, Schladming, Austria, Feb. 28 -- March 6, 2004, submitted to Lecture Notes in Physics, Springer Verlag, 45 pages