  We employ the supernova fallback disk model to simulate the spin evolution of
isolated young neutron stars (NSs). We consider the submergence of the NS
magnetic fields during the supercritical accretion stage and its succeeding
reemergence. It is shown that the evolution of the spin periods and the
magnetic fields in this model is able to account for the relatively weak
magnetic fields of central compact objects and the measured braking indices of
young pulsars. For a range of initial parameters, evolutionary links can be
established among various kinds of NS sub-populations including magnetars,
central compact objects and young pulsars. Thus, the diversity of young NSs
could be unified in the framework of the supernova fallback accretion model.
