  Mesoscopic mechanical oscillators can be prepared in quantum states and
coherently manipulated using the optomechanical interaction. This has recently
been used to prepare squeezed mechanical states. However, the scheme used in
these experiments relies on slow, dissipative evolution that destroys the
system's memory of its initial state. In this paper we propose a protocol based
on a sequence of four pulsed optomechanical interactions. In addition to being
coherent, our scheme executes in a time much shorter than a mechanical period.
We analyse applications in impulsive force sensing and preservation of
continuous-variable quantum information.
