We present, experimentally and theoretically, nonlinear magneto-optical rotation (NMOR) using two spatially separated laser beams, the pump laser beam for creation and the probe laser beam for detection of the coherence between ground Zeeman sublevels. Both pump and probe lasers are tuned to ${F}_{g}=2\ensuremath{\rightarrow}{F}_{e}=1$ transition in
87Rb. With the specially designed spatial configuration of the pump and the probe beams we were able to obtain dispersively shaped probe laser NMOR resonances in the Rb vacuum gas cell. The theory indicates that the obtained line shapes are due to the interference between prepared atomic states and the probe laser field. The interference nature of the resonances is supported by narrowing of NMOR resonances with increased separation between laser beams, and by the shift of the central fringe from the zero magnetic field with increased angle between initial orientation of electric vectors of linearly polarized pump and probe beams.
This paper studies quantum entanglement between two spatially separated atoms driven by a coherent laser field in the dissipative process of spontaneous emission. It is shown that the entanglement strongly depends on the detuning of the laser frequency from atomic transition frequency, the interatomic separation and the Rabi frequency of the coherent laser field. A considerable amount of steady state entanglement can be obtained near Δ = —α (i.e., the dipole-dipole interaction and the detuning cancel out mutually) for small atomic separation and large Rabi frequency of the coherent laser field.
The authors report the observation of narrow Ramsey-type fringes in a caesium beam by applying two spatially separated resonant laser fields. Zeeman coherences created by the first laser evolve in a constant magnetic field and are probed by the second laser. The fluorescence of the atoms in the probe light is recorded as a function of the magnetic field, showing a Ramsey-type interference pattern. Linewidths of the central valley of 0.5 mG are obtained when the distance between the two lasers is 34.5 cm. The influence of the thermal beam velocity distribution is discussed.