Phase Controlling Sub-half-wavelength Localization Of Moving Atom

Precise measurement of position of a microcosmic particle is a fundamental and important problem in physics.Measurement of the position of an atom passing through a standing-wave field has attracted considerable attention in recent years, because optical methods such as sub-half-wavelength atom localization can provide high spatial resolution and have potential applications to many areas of optical manipulations of atomic degrees of freedom. Recently, probing the absorption spectrum, spontaneous spectrum or resonance fluorescence spectrum by using the atom coherent and quantum interference effects can realize the localization of moving atoms. In this article, we present a scheme of sub-half-wavelength localization of moving atoms, basing on the phase-dependent electromagnetically induced transparency in a four-level system in the double-A configuration. A weak bichromatic field is used as the probe components and a strong bichromatic field is used as the driving components, one component of which is standing-wave field. The four components couple to the four electronic transitions of the four level double-A atom, which form a closed transition loop. Probing the absorption of the probe fields can localize the atom in the half wave regime by properly choosing the detunings and collective phase of the four applied components. The detecting probability can reach 50%. The position of the localization peaks can be changed in a wide regime by properly changing the de-tunings of the fields. This scheme is the experimental accessibility and controllability.