  Enss (1983) proved a propagation estimate for the usual free Schroedinger
operator that turned out later to be very useful for inverse scattering in the
work of Enss--Weder (1995). Since then, this method has been called the
Enss--Weder time-dependent method. We study the same type of propagation
estimate for the fractional powers of the negative Laplacian and, as with the
Enss--Weder method, we apply our estimate to inverse scattering. We find that
the high-velocity limit of the scattering operator uniquely determines the
short-range interactions.
