Counterfactual communication protocols are analyzed using three approaches: a classical argument, the weak trace criterion, and the Fisher information criterion. It is argued that the classical analysis leads to contradiction and should therefore be abandoned. The weak trace and Fisher information criteria are shown to agree about the degree of counterfactuality of communication protocols involving postselection. It is argued that postselection is a necessary ingredient of counterfactual communication protocols. Coherent interaction experiments, as well as a recently introduced modification of counterfactual communication setups which eliminates the weak trace, are discussed.

中文翻译：

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分析反事实协议的反事实性的三种方法

使用三种方法分析反事实通信协议：经典论证、弱跟踪标准和 Fisher 信息标准。有人认为，经典分析会导致矛盾，因此应该放弃。弱跟踪和 Fisher 信息标准被证明在涉及后选择的通信协议的反事实程度方面是一致的。有人认为后选择是反事实通信协议的必要组成部分。讨论了相干交互实验，以及最近引入的消除弱跟踪的反事实通信设置的修改。