After accurate quantum momentum is generated by trajectory clustering, incorrect decoherence is still present in some cases. To illustrate this intrinsic problem of CTSH, we take a representative WP branching process as an example (see Figure ). When WP branching happens, the coherence between the two electronic states rapidly decays to zero. In the pure state description of nonadiabatic dynamics, the electronic subsystem should stochastically collapse to one of the eigenstates with incoherent superposition.