Efficient two-dimensional atom localization in a four-level atomic system beyond weak-probe approximation

We present a new scheme for high-efficiency two-dimensional (2D) atom localization in a four-level atomic system via measuring the populations in two excited states beyond weak-probe approximation. Owing to the space-dependent atom-field interaction, the position probability distribution of the atom passing through the standing waves can be directly determined by measuring the populations in two excited states. It is found that the phase-sensitive property of the atomic system significantly reduces the uncertainty in the position measurement of the atom. Especially the probability of finding the atom at a particular position can be almost 100% via properly varying the parameters of the system. The proposed scheme may open a promising way to achieve high-precision and high-efficiency 2D atom localization.