  In a recent paper [Phys. Rev. A 82, 063623 (2010)] Hallwood et al. argued
that it is feasible to create large superposition states with strongly
interacting bosons in rotating rings. Here we investigate in detail how the
superposition states in rotating-ring lattices depend on interaction strength
and barrier height. With respect to the latter we find a trade-off between
large energy gaps and high cat quality. Most importantly, we go beyond the
\delta-function approximation for the barrier potential and show that the
energy gap decreases exponentially with the number of particles for weak
barrier potentials of finite width. These are crucial issues in the design of
experiments to realize superposition states.
