Eur. Phys. J. D (2014) 68: 337
https://doi.org/10.1140/epjd/e2014-50474-x

Regular Article

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

¹ IFLP-CCT-CONICET, Universidad Nacional de La Plata, C.C. 727, 1900 La Plata, Argentina
² Instituto de Física, Universidade Federal do Rio de Janeiro, 21.942-972 Rio de Janeiro, Brazil
³ CeBio y Secretaria de Investigación, Universidad Nacional del Noroeste de la Provincia de Buenos Aires – UNNOBA and CONICET, R. Saenz Peña 456, Junin, Argentina

^a e-mail: plastino@fisica.unlp.edu.ar

Received: 24 June 2014
Received in final form: 7 September 2014
Published online: 4 November 2014

Abstract

In [X.-W. Hou, Z.-P. Huang, S. Chen, Eur. Phys. J. D 68, 87 (2014)], Hou et al. 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.