Subadditivity condition for spin-tomograms and density matrices of   arbitrary composite and noncomposite qudit systems
  New quantum entropic inequality for states of system of n >_ 1 qudits is obtained. The inequality has the form of quantum subadditivity condition of bipartite qudit system and coincides with this subadditivity condition for the system of two qudits. The general statement on existence of the subadditivity condition for arbitrary probability distribution and arbitrary qudit-system tomogram is formulated. The nonlinear quantum channels creating the entangled states from separable ones are discussed. 
V. N. Chernega, O. V. Man'ko, V. I. Man'ko
quant-ph