Experimental characterization of the Gaussian state of squeezed light obtained via single-passage through an atomic vapor

TL;DR

This paper demonstrates a simplified method for characterizing the Gaussian state of squeezed light transmitted through atomic vapor, enabling easier noise analysis and entanglement measurement without a local oscillator.

Contribution

It introduces a Gaussian-based approach using Stokes operators for simplified noise ellipsis reconstruction and empirical validation in atomic vapor transmission.

Findings

Gaussian statistics accurately describe transmitted light fluctuations

Complete noise ellipsis can be reconstructed via matrix diagonalization

Entanglement and quantum discord are measurable with the proposed method

Abstract

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.