  I present a technical report indicating that the two methods used for
calculating characteristic functions for the work distribution in weakly driven
quantum master equations are equivalent. One involves applying the notion of
quantum jump trajectory [Phys. Rev. E 89, 042122 (2014)], while the other is
based on two energy measurements on the combined system and reservoir [Silaev,
et al., Phys. Rev. E 90, 022103 (2014)]. These represent backward and forward
methods, respectively, which adopt a very similar approach to that of the
Kolmogorov backward and forward equations used in classical stochastic theory.
The microscopic basis for the former method is also clarified. In addition, a
previously unnoticed equality related to the heat is also revealed.
