  There has been considerable recent interest in matterwave interferometry with
bright solitons in quantum gases with attractive interactions, for applications
such as rotation sensing. We model the quantum dynamics of these systems and
find that the attractive interactions required for the presence of bright
solitons causes quantum phase-diffusion, which severely impairs the
sensitivity. We propose a scheme that partially restores the sensitivity, but
find that in the case of rotation sensing, it is still better to work in a
regime with minimal interactions if possible.
