Fidelity of the photon subtracted (or added) squeezed vacuum state and squeezed cat state

In this paper, the fidelity of photon subtracted (or added) squeezed vacuum state with arbitrary number of photons and squeezed cat state is derived analytically. The result shows that whether the photon is added or subtracted, the maximum fidelity increases with the increase of the change of photon number, and the amplitude of the superposition state corresponding to the maximum fidelity also increases. In addition, for the same number of subtracted or added photons, the amplitude of the superposition state corresponding 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 make photon added than photon subtracted the photon added can be used as an important method to obtain cat state of large amplitude.