  We study a quantum many-body system of attracting bosons confined in a
ring-shaped potential and interrupted by a weak link. With such architecture,
the system defines atomtronic quantum interference devices harnessing quantum
solitonic currents. We demonstrate that the system is characterized by specific
interplay between the interaction and the strength of the weak link. In
particular, we find that, depending on the operating conditions, the current
can be a universal function of the relative size between the strength of the
impurity and interaction. The low lying many-body states are studied through a
quench dynamical protocol that is the atomtronic counterpart of the Ramsey
interferometry. With this approach, we demonstrate how our system defines a
qubit. The current states are addressed through the analysis of the momentum
distribution.
