Non-classical correlation in a multipartite quantum system reconsidered

There is a commonly recognized paradigm in which a quantum multipartite system described by a density operator having no product eigenbasis is considered to be non- classically correlated. Supporting this paradigm, we define an entropic measure of non- classical correlation derived from a minimum uncertainty for a person about the system after receiving outcomes of certain local measurements. It is similar to but different from the measure of quantumness defined in [B. Groisman, D. Kenigsberg, and T. Mor, quant-ph/0703103]. Numerical computation of the measure of non-classical correlation for several examples is performed using random search methods. (The details are found in our preliminary manuscript [A. SaiToh, R. Rahimi, and M. Nakahara, quant- ph/0703133].) We also show an enhancement of the computer algorithm for this computation as well as an analytical calculation of the measure for a certain two-qubit system.