Quantum state discrimination via linear optics and continuous photon counting

In this paper, an expansion of the formulae to check whether one can implement a step via linear optics and photon counting was derived, to the limit of continuous photon counting, The limit that the coupling between the signal and measurement apparatus is infinitesimal at each step and the number of the step is infinitely large was discussed. As an example, a specific case where the states to be discriminated are single-mode states and any nonclassical ancillas are excluded.