Entanglement in Atomic Resonance Fluorescence

The resonance fluorescence from regular atomic systems is shown to represent a continuous source of non-Gaussian entangled radiation propagating in two different directions. For a single atom entanglement occurs under the same conditions as squeezing. For more atoms, the entanglement can be more robust against dephasing than squeezing, hence providing a useful continuous source for various applications of entangled radiation.

Figure 1

The normalized minor $\mu$ is shown, as a function of the angle ${\varphi }_2$, for a linear chain of atoms with $N=2$ (solid line), 3 (dashed line), and 4 (dotted line). The pumping strength yields ${\sigma }_{22}/|{\sigma }_{21}{|}^2=3.5$.