Wringing out better Bell inequalities

Local realism implies constraints on the statistics of two physically separated systems. These constraints, known collectively as Bell inequalities, can be violated by quantum mechanics. We generalize the standard Bell inequalities in two ways: first, by 'chaining' the Clauser-Horne-Shimony-Holt Bell inequality for two-state systems and, second, by formulating information-theoretic Bell inequalities that apply to any pair of systems. (orig.)