Abstract
Quadrature squeezed states of light are important resources for continuous-variable quantum inforamtion protocols. Squeezing level or purity of the states often dominate the performances of such protocols. In this article, I review our experiment which generates the quadrature squeezed state of light at 860nm with high squeezing level and purity. The generated state has been improved in its squeezing level and purity by using a periodically-poled KTiOPO4 (PPKTP) crystal as a nonlinear optical medium in a sub-threshold cw pumped optical parametric oscillator.
