A novel description of the interaction of quantum optical systems with
a single one-photon wave packet in terms of a generalized master equa
tion is introduced. A corresponding quantum Monte-Carlo wavefunction s
imulation algorithm can be obtained from the driven system approach [H
. J. Carmichael, Phys. Rev. Lett. 70, 2273 (1993); C. W. Gardiner, ibi
d. 2269 (1993)].