  Optical switch fabric plays an important role in building multiple-user
optical quantum communication networks. Owing to its self-routing property and
low complexity, Banyan network is widely used for building switch fabric.
While, there is no efficient way to remove internal blocking in Banyan network
by classical way. Quantum state fusion, by which the two-dimensional internal
quantum state of two photons could be combined into four-dimensional internal
state of a single photon, makes it possible to solve this problem. In this
paper, we convert the output mode of quantum state fusion from
spatial-polarization mode to time-polarization mode. By combining modified
quantum state fusion, quantum state fission with quantum Fredkin gate, we
propose a practical scheme to build an optical quantum switch unit which is
block free. The scheme can be extended to build more complex units, four of
which are shown in this paper.
