  The router is a key element for a network. We describe a scheme to realize
genuine quantum routing of single-photon pulses based on cascading of
conditional quantum gates in a Mach-Zehnder interferometer and report a
proof-of-principle experiment for its demonstration using linear optics quantum
gates. The polarization of the control photon routes in a coherent way the path
of the signal photon while preserving the qubit state of the signal photon
represented by its polarization. We demonstrate quantum nature of this router
by showing entanglement generated between the initially unentangled control and
signal photons, and confirm that the qubit state of the signal photon is well
preserved by the router through quantum process tomography.
