For systems consisting of distinguishable particles, there exists an agreed upon notion of entanglement which is fundamentally based on the possibility of addressing individually each one of the constituent parties. Instead, the indistinguishability of identical particles hinders their individual addressability and has prompted diverse, sometimes discordant definitions of entanglement. In the present review, we provide a comparative analysis of the relevant existing approaches, which is based on the characterization of bipartite entanglement in terms of the behaviour of correlation functions. Such a a point of view provides a fairly general setting where to discuss the presence of non-local effects; it is performed in the light of the following general consistency criteria: i) entanglement corresponds to non-local correlations and cannot be generated by local operations; ii) when, by "freezing" suitable degrees of freedom, identical particles can be effectively distinguished, their entanglement must reduce to the one that holds for distinguishable particles; iii) in absence of other quantum resources, only entanglement can outperform classical information protocols. These three requests provide a setting that allows to evaluate strengths and weaknesses of the existing approaches to indistinguishable particle entanglement and to contribute to the current understanding of such a crucial issue. Indeed, they can be classified into five different classes: four hinging on the notion of particle and one based on that of physical modes. We show that only the latter approach is consistent with all three criteria, each of the others indeed violating at least one of them.

中文翻译：

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无法区分的粒子系统中的纠缠

对于由可区分粒子组成的系统，存在一种公认的纠缠概念，该概念基本上基于单独处理每个组成方的可能性。相反，相同粒子的不可区分性阻碍了它们各自的可寻址性，并引发了对纠缠的不同定义，有时甚至是不一致的定义。在本综述中，我们对现有的相关方法进行了比较分析，该方法基于相关函数行为方面的二分纠缠特征。这种观点为讨论非局部效应的存在提供了一个相当普遍的环境；它是根据以下一般一致性标准执行的：i) 纠缠对应于非局部相关性，不能由局部操作产生；ii) 当通过“冻结”合适的自由度，可以有效区分相同粒子时，它们的纠缠必须减少到可区分粒子的纠缠；iii) 在没有其他量子资源的情况下，只有纠缠才能胜过经典信息协议。这三个请求提供了一个设置，可以评估现有方法的优缺点，以促进难以区分的粒子纠缠，并有助于当前对这一关键问题的理解。事实上，它们可以分为五种不同的类别：四种基于粒子的概念，一种基于物理模式的概念。我们表明只有后一种方法符合所有三个标准，