Unified scheme for correlations using linear relative entropy

• We propose a unified view of correlations in a two qubit system.
• The linear relative entropy is used to quantify total, quantum and classical correlations.
• We discuss the relationship among the different types of correlations in a two qubit system.

A linearized variant of relative entropy is used to quantify in a unified scheme the different kinds of correlations in a bipartite quantum system. As illustration, we consider a two-qubit state with parity and exchange symmetries for which we determine the total, classical and quantum correlations. We also give the explicit expressions of its closest product state, closest classical state and the corresponding closest product state. A closed additive relation, involving the various correlations quantified by linear relative entropy, is derived.