Various inequalities (Boole inequality, Chung-Erdös inequality, Frechet inequality) for Kolmogorov (classical) probabilities are considered. Quantum counterparts of these inequalities are introduced, which have an extra 'quantum correction' term, and which hold for all quantum states. When certain sufficient conditions are satisfied, the quantum correction term is zero, and the classical version of these inequalities holds for all states. But in general, the classical version of these inequalities is violated by some of the quantum states. For example in bipartite systems, classical Boole inequalities hold for all rank one (factorizable) states, and are violated by some rank two (entangled) states. A logical approach to CHSH inequalities (which are related to the Frechet inequalities), is studied in this context. It is shown that CHSH inequalities hold for all rank one (factorizable) states, and are violated by some rank two (entangled) states. The reduction of the rank of a pure state by a quantum measurement with both orthogonal and coherent projectors, is studied. Bounds for the average rank reduction are given.
I. INTRODUCTIONEntanglement is an important feature of quantum mechanics. After the fundamental work by Einstein, Podolsky and Rosen[1] and also Schrödinger[2] it has been studied extensively in the literature [3]. It leads to strong correlations between various parties, which have been studied within the general area of Bell inequalities and contextuality [4][5][6][7][8][9][10][11][12][13][14][15].Kolmogorov (classical) probabilities obey many inequalities, and in this paper we are interested in Boole inequalities, Chung-Erdös inequalities [16] and Frechet inequalities [17,18]. Quantum probabilities are different from Kolmogorov probabilities, and we show in this paper that they obey quantum versions of these inequalities, that contain extra 'quantum correction' terms. This is related to the fact that Kolmogorov probabilities are intimately connected to Boolean (classical) logic formalized with set theory, while quantum probabilities are related to the Birkhoff-von Neumann (quantum) logic [21,22] formalized with subspaces of a Hilbert space.We will use the terms quantum (classical) probabilistic inequalities, for those that contain (do not contain) quantum corrections. Then:• By definition all quantum states obey the quantum probabilistic inequalities.• We give sufficient conditions for the quantum corrections to be zero, in which case the quantum probabilistic inequalities reduce to the usual classical probabilistic inequalities.• In general, classical probabilistic inequalities are violated by some quantum states. It is interesting to study such cases, because this highlights the difference between quantum and classical (Kolmogorov) probabilities.