  Realizing highly sensitive interferometry is essential to accurate
observation of quantum properties. Here we study two kinds of Ramsey
interference fringes in a whispering-gallery resonator, where the coherent
phonons for free evolution can be achieved by stimulated Brillouin scattering.
These two different fringes appear, respectively, in the regimes of rotating
wave approximation (RWA) and anti-RWA. Our work shows particularly that the
anti-RWA Ramsey interference takes some quantum properties of squeezing, which
enhances the strength and visibility of the fringes and shows robustness
against the system's decay. In application, our proposal, feasible with current
laboratory techniques, provides a practical idea for building better quantum
interferometers.
