Generation of macroscopic superposition states in ring superlattices

Ultracold bosons in rotating ring lattices have previously been shown to form macroscopic superpositions of different quasimomentum states. We demonstrate that the generation of this kind of state using slightly nonuniform ring lattices has several advantages: the energy gap decreases less severely with increasing number of particles, the sensitivity to detunings from the critical rotation frequency is reduced, and the scheme is not limited to commensurate filling. We show that different quasimomentum 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.