Variance 〈(δX+)2〉 versus r1 for the fixed collective phase Φ = 0
Figure 5. Variance 〈(δX+)2〉 versus r1 for the fixed collective phase Φ = 0. The other parameters are q = (0, 0.2, 0.5, 1, 5, 10). (a) s = 0.5, (b) s = 1, (c) s = 2, and (d) s = 5. The curves for q = (1, 5, 10) can hardly be distinguished. The variance drops below the standard quantum limit 1 in a wide range of parameters. This indicates the existence of the two-mode squeezing and entanglement under loose conditions.
We show that it is possible to use an atom–cavity reservoir to prepare the two-mode squeezed and entangled states of a hybrid system of an atomic ensemble and an optical field, which do not directly interact with each other. The essential mechanism is based on the combined effect of a two-mode squeezing interaction and a beam–splitter interaction between the system and the reservoir. The reservoir mechanism is important for quantum networking in that it allows an interface between a localized matter-based memory and an optical carrier of quantum information without direct interaction.