A study of correlation properties of multiqubit states by using a characteristic function

We present calculations of the normally ordered characteristic function (NOCF) of Bose operators for the Greenberger–Horne–Zeilinger states and the Dicke ones. The NOCF is shown to contain information about two types of photon correlations: pseudoclassical and quantum ones. Quantum correlations are connected with interference terms of the NOCF, whereas pseudoclassical photon correlations and their cumulants satisfy the relations for classical random variables. We introduce a measure of the quantumness for entangled multimode states not related to the entropy approach. The maximum of the measure of quantumness is demonstrated to explain an intuitive choice of numeric values for the coefficients in a multiqubit state vector. (comment)