An observable based approach to evaluating quantum coherence

We introduce a procedure based on quantum expectation values of measurement observables to characterize quantum coherence. In a bipartite system, the two-point correlation function is used in combination with the Schatten-1 norm to estimate the quantum coherence. This definition of coherence allows the decomposition into contributions corresponding to the non-classical correlations between the subsystems and localized on each subsystem. We illustrate the method for several bipartite systems, showing that an incomplete basis still gives a qualitative measure of the coherence.