CONDITIONAL HAMILTONIAN AND RESET OPERATOR IN THE QUANTUM JUMP APPROACH

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