Entropic and information inequality for nonlinearly transformed two-qubit X-states

¹ P.N. Lebedev Physical Institute, Russian Academy of Science - Moscow 119991, Russia
² Moscow Institute of Physics and Technology (State University) - Dolgoprudny 117303, Russia

Received: 18 October 2014
Accepted: 23 February 2015

Abstract

The entropic and information inequalities for two-qubit X-states transformed by the nonlinear channels are given in explicit form. The subadditivity condition and non-negativity of the von Neumann quantum information are studied for both the initial X-state and the state after the action of the nonlinear channel. The partial case of the Werner state is considered in detail. We show that the von Neumann information increases due to the action of the nonlinear channel. We generalize the results obtained for the Werner state given in our earlier article (J. Russ. Laser Res., 35 (2014) 362) to the case of a X-state of a two-qubit system. We study the influence of a nonlinear channel acting on the X-state of a two-qubit system onto the von Neumann mutual information.