Quantum correlated light beams from nondegenerate four-wave mixing in an atomic vapor: The D1 and D2 lines of⁸⁵Rb and⁸⁷Rb

We present experimental results showing that quantum correlated light can be produced using non-degenerate, off-resonant, four-wave mixing (4WM) on both the D1 (795 nm) and D2 (780 nm) lines of ⁸⁵Rb and ⁸⁷Rb, extending earlier work on the D1 line of ⁸⁵Rb. Using this 4WM process in a hot vapor cell to produce bright twin beams, we characterize the degree of intensity-difference noise reduction below the standard quantum limit for each of the four systems. Although each system approximates a doublelambda configuration, differences in details of the actual level structure lead to varying degrees of noise reduction. The observation of quantum correlations on light produced using all four of these systems, regardless of their substructure, suggests that it should be possible to use other systems with similar level structures in order to produce narrow frequency, nonclassical beams at a particular wavelength.