  We show that the description of light in terms of Stokes operators in
combination with the assumption of Gaussian statistics results in a dramatic
simplification of the experimental study of fluctuations in the light
transmitted through an atomic vapor: no local oscillator is required, the
detected quadrature is easily selected by a wave-plate angle and the complete
noise ellipsis reconstruction is obtained via matrix diagonalization. We
provide empirical support for the assumption of Gaussian statistics in
quasi-resonant light transmitted through an $^{87}$Rb vapor cell and we
illustrate the suggested approach by studying the evolution of the fluctuation
ellipsis as a function of laser detuning. Applying the method to two light
beams obtained by parting squeezed light in a beamsplitter, we have measured
entanglement and quantum discord.
