Manipulating the quantum properties of continuous laser beams

The quantum properties of light play an ever increasing role in optics. Thanks to the ability to generate and use special light with modified quantum noise and to the generation of optical entanglement, we can now avoid the conventional limits imposed by the shot noise. In addition, we can create new quantum information protocols. This article concentrates on the case of continuous laser beams, which are used in many precision measurements and applications. The article summarizes some of the concepts, reviews the technical development, provides a simple and reliable model and shows some of the current directions of using optical quantum correlations, such as for the storage of quantum information.