  We investigate the effects of rotation on one-dimensional ultracold bosons
confined to optical ring lattices. First, we show that there exists a critical
rotation frequency at which the ground state of a weakly-interacting and
integer-filled atomic gas is fragmented into a macroscopic superposition state
with different circulation. Second, we point out several advantages of using
slightly non-uniform ring lattices. Finally, we demonstrate that different
quasi-momentum states can be distinguished in time-of-flight absorption imaging
and propose to probe correlations via the many-body oscillations induced by a
sudden change in the rotation frequency.
