Operator reaction field theory in quantum optics: a study of one two-levelatom in a broad-band squeezed vacuum without rotating wave approximation

We review the use of operator reaction field theory in quantum optics by co nsidering the problem of one atom in an isotropic three-dimensional broad-b and squeezed vacuum. In these terms we give a quantum electrodynamical anal ysis of this system exact up to all contributions of order one in the ratio gamma omega(0)(-1), the ratio of the A-coefficient to the atomic resonance frequency. These terms include all of the counter-rotating terms at this o rder. At zero order, namely in the usual rotating wave approximation, we fi nd the usual Einstein rate equation while we confirm that the fluorescence spectrum consists of two Lorentzian peaks. However, at order one we find an additional oscillating term in the rate equation and additional resonant d ispersive terms correct for each of the two Lorentzian peaks in the fluores cence spectrum. Similar results are expected for broad-band correlated sque ezed vacua of arbitrary, rather than isotropic, geometry.