Maximal mutual correlation: an algebraic measure of correlations in   bipartite quantum systems
  We introduce an algebraic measure of correlations in bipartite quantum systems. The proposed quantity, called maximal mutual correlation, provides the information how much a given state differs from the product state of its marginals. In contrast to the entanglement or quantum discord, maximal mutual correlation can be non - zero for some classically correlated quantum states. 
Lech Jakobczyk
quant-ph