  We show how to calculate the first- and second-order statistics of the
scattered fields for an arbitrary intensity coherent state light field
interacting with a two-level system in a waveguide geometry. Specifically, we
calculate the resonance fluorescence from the qubit, using input-output
formalism. We derive the transmission and reflection coefficients, and
illustrate the bunching and anti-bunching of light that is scattered in the
forward and backward directions, respectively. Our results agree with previous
calculations on one- and two-photon scattering as well as those that are based
on the master equation approach.
