We report an experimental demonstration of single-photon switching in laser-cooled 87Rb atoms. A resonant probe pulse with an energy per unit area of one photon per λ2/2π propagates through the optically thick atoms. Its energy transmittance is greater than 63% or loss is less than e−1 due to the effect of electromagnetically induced transparency. In the presence of a switching pulse with an energy per unit area of 1.4 photons per λ2/2π, the energy transmittance of the same probe pulse becomes less than 37% or e−1. This substantial reduction of the probe transmittance caused by single switching photons has potential applications in single-photon-level nonlinear optics and the manipulation of quantum information.
@article{arxiv.physics/0501155,
title = {Observation of Single-Photon Switching},
author = {Yong-Fan Chen and Zen-Hsiang Tsai and Yu-Chen Liu and Ite A. Yu},
journal= {arXiv preprint arXiv:physics/0501155},
year = {2007}
}