Nearly deterministic Fredkin gate based on weak cross-Kerr nonlinearities

A Fredkin gate is an indispensable logic gate for the applications of the scalable quantum network. Weak cross-Kerr nonlinearities serve as the intermediary between photons and coherent states and thus provide the indirect interaction between photons. By means of weak cross-Kerr nonlinearities, we propose a construction scheme of a nearly deterministic Fredkin gate, where polarization modes of photons carry quantum bits. By virtue of an X homodyne measurement on the coherent state, the appropriate classical feed-forward operations are executed according to the different measurement outcomes. Applying one swap gate and two combination gates and other assistant simple optical elements, the nearly deterministic Fredkin gate is successfully constructed. The unique features of photons as quantum information carriers with high velocity and low decoherence, combined with simple elements and mature operation techniques, afford the possibility to the scheme proposed here which takes aim at feasible quantum logic circuits for practical and scalable quantum computation and quantum communication.