Quantum-mechanical description of polarized and unpolarized light

摘要

The restrictions for density operators of unpolarized quasiplane and quasimonochromatic two-mode light are determined by invariance with respect to SU(2) polarization transformations and it is shown that this leads only to the type of unpolarized light established in [6]. In this connection, it is clarified and underlined by group-theoretical considerations that the "type II of unpolarized light" derived in [8-11] is in reality a type of polarized light with second-order polarization (or hidden polarization in first order) and that it is obtained by invariance with respect to an axial subgroup C_(∞v) of SU(2) or of (2).