Limiting measurements in quantum and atomic optics: Localized mesoscopic polarization quantum states

In this paper, we discuss topical directions of modern quantum and atomic o ptics related to various limiting (in the level of noise) measurements in o ptical systems. The considered fundamental properties of polarization of li ght can be employed to prepare unique superposition macroscopic states of a quantum system (polarization-scalar light), which can be revealed a poster iori through measurements (reduction of a wave packet). The quantum interfe rence of such states gives rise to several fundamental physical effects, wh ich are manifested in the nonclassical behavior of distribution functions o f Hermitian quadratures of a light field, the number of photons, and/or Wig ner quasi-distribution functions and the entropy of quantum states. Such qu antum states of light, which are actively discussed at the moment in the sc ientific literature in Russia and abroad, may find extensive applications f or the development of new physical principles for quantum computations and a new generation of optical information processing (transmission) systems.