Experimental Preparation Of A Two-mode Squeezed Optical Field With Higher Purity

Squeezed optical field has a wide range of applications in frontiers of research,such as quantum information processing and quantum measurement.Using the squeezed optical field,we can realize the preparation of EPR entangled states,quantum measurement with high precision,preparation of multipartite entangled states,detection of gravitational waves and generation of an optical Schr?dinger cat state,et al.Experimental preparation of squeezed optical field is important in the fundamental and application research of quantum optics.For a long time,scientists have been devoted to how to improve the squeezing degree of the squeezed light and find the generated method of squeezed optical field.Along with the development of quantum optics and quantum information,scientists find that simply raising the squeezing level of the squeezed light is not enough in some cases.We also need to pay attention to the purity of the squeezed state for the achievement of some complex works.An efficient method for preparing an optical Schr?dinger cat state is subtracting a photon from a squeezed vacuum state.It has been shown that the fidelity of Schr?dinger cat state based on photon subtraction depends on the purity of squeezed vacuum state.A two-mode squeezed state of light with a purity of 0.993 is experimentally produced by a non-degenerate optical parametric amplifier,where the pump beam is partially oscillating in the cavity.Especially,we find that two-mode squeezed states with high purity can be obtained by our non-degenerate optical parametric amplifier(NOPA)in a wide range of pump power due to the presence of thermal effect.The result of this experiment provides a technical reference for obtaining an optical Schr?dinger cat state with high fidelity.In this thesis,the main research contents include:1.We theoretically calculate the squeezing level and purity of the squeezed state of light,and analyze the various parameters.We also discuss the noise deviation of NOPA,as well as the theoretical model of the thermal effect.2.We experimentally prepare a two-mode squeezed state of light with a purity of 0.993 with the partly-resonant NOPA system,reconstruct the Wigner function of the pure squeezed state,and analyze the result of the experiment.