All-Optical Switch and Transistor Gated by One Stored Photon

Abstract
A Single-Photon Gate: A long-standing goal in optics is to produce an all-optical transistor, in which the transmission of a light beam can be controlled by a single photon. Using a system in which a cloud of cesium atoms is coupled to an optical cavity, Chen et al. (p. 768 , published online 4 July; see the Perspective by Volz and Rauschenbeutel ) were able to control transmission through the optical cavity by exciting the atomic ensemble using a “gate” laser pulse. Just one gate photon stored was sufficient to detune the system and switch the transmission of source photons through the cavity.