  For the time development of a single system in the quantum jump approach or
for quantum trajectories one requires the conditional (reduced) Hamiltonian
between jumps and the reset operator after a jump. Explicit expressions for
them are derived for a general N-level system by employing the same assumptions
as in the usual derivation of the Bloch equations. We discuss a possible minor
problem with positivity for these expressions as well as for the corresponding
Bloch equations.
