  The elastic scattering peak of a resonantly driven two-level system has been
argued to provide narrow-linewidth antibunched photons. Although independent
measurements of spectral width on the one hand and antibunching on the other
hand do seem to show that this is the case, a joint measurement reveals that
only one or the other of these attributes can be realised in the direct
emission. We discuss a scheme which interferes the emission with a laser to
produce simultaneously single photons of subnatural linewidth. In particular,
we consider the effect of dephasing and of the detuning between the driving
laser and/or the detector with the emitter. We find that also in presence of
dephasing, our scheme brings considerable improvement as compared to the
standard scheme.
