Entanglement witnesses form an effective method to locally detect entanglement in the laboratory without having the prior knowledge of the full density matrix. However, separable states can be erroneously indicated as entangled in such detections in the presence of wrong measurements or loss in detectors. Measurement-device-independent entanglement witnesses (MDI-EWs) never detect fake entanglement even under wrong measurements and for a particular kind of lossy detectors. A crucial assumption in the case of faithful detection of entanglement employing MDI-EWs is that the preparation devices producing “quantum inputs”—which are inputs additional to the quantum state whose entanglement is to be detected—are perfect and there is no noise during their transmission. Here we relax these assumptions and provide a general framework for studying the effect of noise on the quantum inputs, invoking uniform and nonuniform noise models. We derive sufficient conditions on the uniform noisy map for retaining the characteristic of MDI-EWs. We find that in the context of nonuniform and entangling noise, fake entanglement detection is possible even by MDI-EWs. We also investigate various paradigmatic models of local noise and find conditions of revealing entanglement in the class of Werner states.

中文翻译：

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与测量设备无关的纠缠见证中的噪声量子输入漏洞

纠缠见证形成了一种有效的方法，可以在实验室中局部检测纠缠，而无需事先了解全密度矩阵。然而，在存在错误测量或检测器丢失的情况下，可分离状态可能被错误地指示为纠缠在此类检测中。与测量设备无关的纠缠见证 (MDI-EW) 即使在错误的测量和特定类型的有损检测器下也永远不会检测到假纠缠。在使用 MDI-EW 准确检测纠缠的情况下，一个关键假设是，产生“量子输入”的准备设备是完美的，并且在它们的过程中没有噪音。传送。在这里，我们放宽了这些假设，并提供了一个通用框架来研究噪声对量子输入的影响，调用均匀和非均匀噪声模型。我们在均匀噪声图上推导出充分条件以保留 MDI-EW 的特征。我们发现，在不均匀和纠缠噪声的情况下，即使通过 MDI-EW 也可以进行假纠缠检测。我们还研究了局部噪声的各种范式模型，并找到了揭示 Werner 状态类中纠缠的条件。