Single-Atom Detection

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Abstract
An overview is presented of the principles and achievements of various laser-assisted detection techniques that have been developed to observe a single or a small number of neutral atoms in the gaseous state. Possible applications of these single-atom detection (SAD) techniques and their significance for the improvement of analytical detection limits are mentioned. Section I describes the general implications of SAD techniques and contains statistical expressions for the mean and the fluctuation of the signal. An intrinsic limit of detection is defined that relates to the statistical fluctuation of the number of registered atoms in the observation volume. Section II gives a classification and a more detailed description of reported techniques. Experimental detection limits are compared with the intrinsic limits predicted by theory. In Section III, conclusions are drawn about the state-of-the-art and suggestions are made for further improvements, including the lowering of the analytical detection limit.