“…The problems of quantum filtering for systems driven by Gaussian states, including vacuum state, thermal state, coherent state, and squeezed state, have been well studied, see, e.g., [17,12,34,18]. On the other hand, as single-and multi-photon states can nowadays be generated in real experiments [39,49,51,31,29,36,32,47], more and more research has been concentrated on atomic excitation [49,4,43,40] and quantum filter design [28,26,45,14,20,3] for systems driven by single or multiple photons.…”