Feedback control of the fluorescence light squeezing
We consider a trapped two-level atom stimulated by a coherent monochromatic laser and we study how to enhance the squeezing
of the fluorescence light in the presence of a Wiseman-Milburn feedback mechanism, based on the homodyne detection of a fraction of the emitted light. We analyse the effect of the control parameters on the properties of the spectrum of the light. We also show that feedback can produce sub-natural line-narrowing of the fluorescence light, without the presence of squeezing in the stimulating light. The whole problem is tackled inside the framework of quantum trajectory theory.