Abstract: A scheme for generating spin squeezed state with Mach-Zehnder interferometer was presented and the influence of the phase difference between two interfere paths on spin squeezing parameter was also investigated. It’s shown that spin squeezing occurs at the direction normal to mean spin direction and axis and the spin squeezed state can be effectively generated by adjusting the phase difference between two interfere paths and decreasing the population difference between two interfere paths.

Key words: quantum optics, spin squeezed state, Mach-Zehnder interferometer, phase difference