For BoseEinstein condensates in double wells, N-particle Rabi-like oscillations often seem to be damped. Far from being a decoherence effect, the apparent damping can indicate the emergence of quantum superpositions in the many-particle quantum dynamics. However, in an experiment it would be difficult to distinguish the apparent damping from decoherence effects. This paper suggests using controlled periodic shaking to quasi-instantaneously switch the sign of an effective Hamiltonian, thus implementing an echo technique which distinguishes quantum superpositions from statistical mixtures. The scheme for the effective time reversal is tested by numerically solving the time-dependent N-particle Schr?dinger equation.
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