Yet another additivity conjecture

In quantum information theory, there are several important open problems which center around whether certain quantities are additive or not. Especially, additivity conjecture about Holevo capacity and additivity/strong superadditivity conjecture about entanglement of formation have been attracting many researchers. It recently turned out that these are equivalent to the additivity of the minimum output entropy of quantum channels, which is mathematically simpler. This Letter suggests yet another additivity conjecture which is equivalent to those, and is mathematically simple. This conjecture might be easier than other conjectures to solve, for this can be proven for almost all the examples where one of these conjectures are proven. (c) 2005 Elsevier B.V. All rights reserved.