Information-theoretic aspects of quantum inseparability of mixed states
  Information-theoretic aspects of quantum inseparability of mixed states are investigated in terms of the $\alpha$-entropy inequalities and teleportation fidelity. Inseparability of mixed states is defined and a complete characterization of the inseparable $2\times2$ systems with maximally disordered subsystems is presented within the Hilbert-Schmidt space formalism. A connection between teleportation and negative conditional $\alpha$-entropy is also emphasized. 
Ryszard Horodecki and Michal Horodecki