Fast, all-optical, zero to π continuously controllable Kerr phase gate.

We demonstrate a fast Kerr phase gate in a room-temperature (85)Rb vapor using a Raman gain method where the probe wave travels "superluminally". Continuously variable, zero to π radian nonlinear Kerr phase shifts of the probe wave relative to a reference wave have been observed at 333 K. We show rapid manipulation of digitally encoded probe waves using a digitally encoded phase-control light field, demonstrating the capability of the system in information science and telecommunication applications.