  Charge oscillations in certain nanodevices, more specifically the so-called
Superconducting Cooper Pair Boxes (SCB), are usually interpreted as an effect
of macroscopic quantum coherence; an alternative explanation is however
possible in terms of the Gross-Pitaewski equation for the classical order
parameter. These two explanations are based on different quantum states
assigned to the SCB, occupation number states in the first case, coherent-like
states in the second one. We show that, when the SCB is weakly coupled to an
external source of noise and dissipation, occupation number states are much
more unstable than coherent ones.
