Optoelectronics in Suppression Noise of Light

High quality light, whenever coherent light and nonclassical light, is more and more widely used in many filed. The coherent state behave minimum classical noise and better coherence, is mostly important light in quantum information, precise measurement and quantum metrology etc. In quantum information and quantum optics, a coherent light is used to entanglement generation (Ou, Z. et al. 1992), quantum teleportation (Furusawa, A. et al. 1998), quantum computation (Menicucci, N. et al. 2006) and quantum secret sharing (Lance, A. et al. 2004). The quiet laser beam, shot noise limited laser beam is important in above application. In the past 20 years there has been much interest in the generation and application of various nonclassical light sources, such as squeezed-state entanglement, quantum-correlated twin beams, and sub-poissonian light, for which improved signal-to-noise ratios and measurement precision beyond the quantum-noise limit are anticipated. In particular, subpoissonian light is a promising light source in quantum information and optical communication because of its communication capacity (Tapster, P. et al. 1988; Teich, M. & Saleh, B. 1985; Machida, S. et al. 1987,1989; Richardson, W. et al. 1991; Li, R. et al. 1995). In 1990 Mertz et al. (Mertz, J. et al. 1990) obtained sub-Poissonian light by using the feedforward technique, and in the year of 1997, P. K. Lam et al. (Lam, P. et al. 1997) experimental demonstrate noiseless signal amplification of using positive optoelectronic feed forward. The technique of optoelectronics is applied into noise suppression of light and noiseless signal amplification, and it is extended to other displacement transformation, such as quantum teleportation (Furusawa, A. et al. 1998), quantum cloning (Andersen, U. 2005; Braunstein, S. et al. 2001); furthermore, the purification of nonclassical light recently (Hage, B. et al. 2008; Dong, R. et al. 2008). In this paper, we introduce the application of opto-electronics in noise suppression. It includes two parts, section II is noise suppression of fiber laser to SNL by optoelectronic feed forward and section III is preparation of sub-poissonian state by opto-electronic feedforward.