Comment on Quantum discord through the generalized entropy in bipartite quantum states

Abstract

In [X.-W. Hou, Z.-P. Huang, S. Chen, Eur. Phys. J. D 68, 87 (2014)], Hou etal. present, using Tsallis' entropy, possible generalizations of the quantum discord measure, finding original results. As for the mutual informations and discord, we show here that these two types of quantifiers can take negative values. In the two qubits instance we further determine in which regions they are non-negative. Additionally, we study alternative generalizations on the basis of Rényi entropies.