Coupled cavities for enhancing the cross-phase-modulation in electromagnetically induced transparency - art. no. 023805

We propose an optical double-cavity resonator whose response to a signal is similar to that of an electromagnetically induced transparency (EIT) mediu m. A combination of such a device with a four-level EIT medium can serve fo r achieving large cross-Kerr modulation of a probe field by a signal field. This would offer the possibility of building a quantum logic gate based on photonic qubits. We discuss the technical requirements that are necessary for realizing a probe-photon phase shift of pi caused by a single-photon si gnal. The main difficulty is the requirement of an ultralow reflectivity be am splitter, and we must be able to operate a sufficiently dense cool EIT m edium in a cavity.