A scheme for achieving atom localization in the noise spectrum in phase quadrature of resonance fluorescence from a three-level A atom is suggested. We add a microwave field to the lower energy states in the three-level A atom localization scheme, and form a three-level loop atom system.
When spontaneous emission photons are detected, by changing the relative phase between the three nonresonant fields, the atom is located in one of two half wavelengths, so the probability of atomic localization is 50%. We also see that the intensity and the detuning of the microwave field
affect intensively localization probability. Compared with the scheme based on electromagnetically induced transparency, the detection probability of atoms in the sub wavelength range is only 25%, and the resonance condition is useless.
Distinction of electromagnetically induced transparency and Autler-Towners splitting in a Rydberg-involved ladder-type cold atom system