Multiport beam-splitter controlled transformations with postselection of superposition single-photon states

Two components of superposition single-photon state are entering into two different ports of multiport interferometer. Interference effects in which the inputs into the interferometer are controlling the outputs are studied. In particular we study a multiport beam-splitter (BS) configuration, in which eight input operators a₀, a₁, a₂…a₇ are mixed by 12 BS's to produce the output operators b₀, b₁, b₂…b₇. Multiport beam-splitter transformations of superposition single-photon states are analyzed with a possible use of postselection effects.