  Through exact numerical diagonalization for small numbers of atoms, we show
that it is possible to access quantum Hall states in harmonically confined Bose
gases at rotation frequencies well below the centrifugal limit by applying a
repulsive Gaussian potential at the trap center. The main idea is to reduce or
eliminate the effective trapping frequency in regions where the particle
density is appreciable. The critical rotation frequency required to obtain the
bosonic Laughlin state can be fixed at an experimentally accessible value by
choosing an applied Gaussian whose amplitude increases linearly with the number
of atoms while its width increases as the square root.
