Classical entanglement refers to non-separable correlations between the polarization direction and the polarization amplitude of a light field. The degree of entanglement is quantified by the Schmidt number, taking the value of unity for a separable state and two for a maximally entangled state. We propose two detection methods to determine this number based on the distinguishable patterns of interference between four light sources derived from the unknown laser beam to be detected. The second method, being a modification of the first one, has interference fringes with discernable angles uniquely related to the entangled state. The maximally entangled state corresponds to fringes symmetric about the diagonal axis at either a 45° or a 135° direction, while the separable state corresponds to fringes symmetric about either the $X$ or $Y$ axis, or both simultaneously. States with Schmidt number between unity and two have fringes of symmetric angles between these two extremes. We believe these detection methods would be beneficial in both computation and communications applications of the classically entangled states.

中文翻译：

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使用干涉条纹测量经典纠缠

经典纠缠是指偏振方向和光场的偏振幅度之间不可分离的相关性。纠缠程度由施密特数量化，可分离状态取值为 1，最大纠缠状态取值为 2。我们提出了两种检测方法，根据从待检测的未知激光束衍生的四个光源之间可区分的干涉模式来确定该数字。第二种方法是第一种方法的改进，具有干涉条纹，其角度与纠缠态唯一相关。最大纠缠状态对应于在 45° 或 135° 方向上关于对角轴对称的条纹，而可分离状态对应于关于任何一个方向对称的条纹$X$或$Y$轴，或同时进行。施密特数介于 1 和 2 之间的状态在这两个极端之间具有对称角的边缘。我们相信这些检测方法将有益于经典纠缠态的计算和通信应用。