The Discussion Of Superposition Coherent States

The development of quantumtheory of light has deepened our understanding of nonclassical properties of optical fields.Recently,superpositions of coherent states have attracted special attention due to their remarkable usefulness. When we come to search the microscopic particles, we usually consider in the way of quantum mechanics ,and the states superposition is an important principle which distinguishes quantum mechanics from classical mechnics .The cat in macro-state adapts to the states superposition principle or not is the difference between macro and micro ,and the difference in use between classical mechnics and quantum mechnics .therefore,the schrodinger cat states can be seen to be a divide between classical and quantum.This paper discusses mainly about the schrodinger cat states and the property of excited even/odd cat state.And it also discusses in detail that arbitrary photon subtraction from a squeezed vacuum state has good similarity with squeezed schrodinger cat states or not and the fidelity will tend to 1 or not under certain limitation ,which based on that two-photon subtraction from a squeezed vacuum state has good similarity with squeezed cat states. The result of research shows that whether the photon added or photon subtracted, the maximum fidelity is going to increase with the increase of the change of photon's number, and the amplitude of the superposition state to the maximum fidelity also increases. In addition, for the same number of subtracted or added photon, the amplitude of the superposition state to the maximum fidelity in the case of added photon is larger than in the case of subtracted photon, but the maximum fidelity in the case is smaller. Although it is more difficult to get photon added than to get photon subtracted, as a important method, photon added can be used to obtain cat state of large amplitude.