  If a quantum channel or process cannot be described by any
measure-and-prepare scheme, we may say the channel is in \textit{quantum
domain} (QD) since it can transmit quantum correlations. The concept of QD
clarifies the role of quantum channel in quantum information theory based on
the local-operation-and-classical-communication (LOCC) paradigm: The quantum
channel is only useful if it cannot be simulated by LOCC. We construct a simple
scheme to verify that a given physical process or channel is in QD by using two
non-orthogonal states. We also consider the application for the experiments
such as the transmission or storage of quantum optical coherent states,
single-photon polarization states, and squeezed vacuum states.
