Abstract
Faraday rotation, being a dispersive effect, is commonly considered as the method of choice for nondestructive detection of spin states. Nevertheless Faraday rotation is inevitably accompanied by spin flips induced by Raman scattering, which compromises nondestructive detection. Here, we derive an explicit general relation relating the Faraday rotation and the spin-flip Raman scattering cross sections, from which precise criteria for nondestructive detection are established. It is shown that, even in ideal conditions, nondestructive measurement of a single spin can be achieved only in anisotropic media. Monolayers of transitions metal dichalcogenides are shown to be promising candidates for this purpose.