title: Low-light-level photon switching by quantum interference.
abstract: We report an experimental demonstration of low-light-level photon switching by quantum interference in laser-cooled 87Rb atoms. A resonant probe pulse with an energy per unit area of one photon per lambda2/2pi propagates through the optically thick atoms. Its energy transmittance is greater than 63%, or a loss of less than e(-1), because of the effect of electromagnetically induced transparency. In the presence of a switching pulse with an energy per unit area of 1.4 photons per lambda2/2pi, the energy transmittance of the same probe pulse becomes less than 37%, or e(-1). This substantial reduction of probe transmittance caused by switching photons may lead to potential applications in single-photon-level nonlinear optics and manipulation of quantum information.
authors.affiliation: Department of Physics, National Tsing Hua University, Hsinchu, Taiwan.
authors.forename: Yong-Fan
authors.initials: YF
authors.lastname: Chen
authors.forename: Zen-Hsiang
authors.initials: ZH
authors.lastname: Tsai
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Liu
authors.forename: Ite A
authors.initials: IA
authors.lastname: Yu