Abstract
We experimentally demonstrate a low-light-level cross-phase-modulation (XPM) scheme based on the light-storage technique in laser-cooled Rb87 atoms. The proposed scheme can achieve a similar phase shift and has the same figure of merit as one using static electromagnetically induced transparency under the constant coupling field. Nevertheless, the phase shift and the energy loss of a probe pulse induced by a signal pulse are neither influenced by the coupling intensity nor by the atomic optical density in the light-storage XPM scheme. This scheme enhances the flexibility of the experiment and makes possible conditional phase shifts on the order of π with single photons. © 2006 The American Physical Society.