We show that a anti-correlation of a Stokes parameter implies polarization entanglement according to the PPT criterion and analyze an experiment underway to make a bright source of entangled photons using polarization squeezed light. The polarization of light can be analyzed by using either the continuous variable (CV) or the discrete variable (DV) formalism. We demonstrate that it is possible to develop both approaches by using the second order correlation tensor Rkl;nm(2)(τ) = 〈âk†(t)âl†(t + τ)âm(t + τ)ân(t)〉, where âj (with j ={H, V}) are the operators associated to orthogonal polarization modes. Considering continuous variables, one can express the correlation function of one of the Stokes parameters in terms of Rkl;nm(2)(τ). On the other hand, we show that, if we extract two photons from the investigated state, the density matrix associated to them will be proportional to the second order correlation tensor.
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机译：我们表明，斯托克斯参数的反相关性意味着根据PPT准则偏振纠缠，并分析了正在进行的一项实验，该实验使用偏振压缩光使纠缠光子成为明亮的光源。可以通过使用连续变量（CV）或离散变量（DV）形式主义来分析光的偏振。我们证明可以通过使用二阶相关张量R kl; nm （2）（τ）= 〈â k †（t）â l †（t +τ）â m （t +τ）â n （t）>，其中Â j （其中j = {H，V}）是与正交偏振模相关的算符。考虑连续变量，可以用R kl; nm （2）（τ）表示斯托克斯参数之一的相关函数。另一方面，我们表明，如果我们从研究状态中提取两个光子，则与它们关联的密度矩阵将与二阶相关张量成比例。
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