Resource-efficient linear-optical quantum router

All-linear-optical scheme for fully featured quantum router is presented. This device directs the signal photonic qubit according to the state of one control photonic qubit. In the introduction we formulate the list of requirements imposed on a fully quantum router. Then we describe our proposal showing the exact principle of operation on a linear-optical scheme. Subsequently we provide generalization of the scheme in order to optimize the success probability by means of a tunable controlled-phase gate. At the end, we show how one can modify the device to route multiple signal qubits using the same control qubit.