Nonadditive entropies and quantum entanglement

Generalized quantum information theory is developed based on the nonadditive Tsallis entropy indexed by q. To see how this formalism is superior to the ordinary additive theory with the von Neumann entropy realized in the limit q-->1, the problem of quantum entanglement of mixed states is discussed. It is shown that, for the parameterized Werner-Popescu-type state of a general N-n-system (i.e., an n-partite N-level system), the present approach leads to the limitation on validity of local realism, which is stronger than that derived from the additive theory. (C) 2002 Elsevier Science B.V. All rights reserved.