We show that multipartite quantum states that have a positive partial transpose with respect to all bipartitions of the particles can outperform separable states in linear interferometers. We introduce a powerful iterative method to find such states. We present some examples for multipartite states and examine the scaling of the precision with the particle number. Some bipartite examples are also shown that possess an entanglement very robust to noise. We also discuss the relation of metrological usefulness to Bell inequality violation. We find that quantum states that do not violate any Bell inequality can outperform separable states metrologically. We present such states with a positive partial transpose, as well as with a nonpositive partial transpose.

中文翻译：

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具有部分正转置的量子态可用于计量学

我们表明，相对于粒子的所有二分相而言，具有正的部分转置的多部分量子态可以胜过线性干涉仪中的可分离态。我们介绍了一种强大的迭代方法来查找此类状态。我们给出了多部分状态的一些示例，并检查了精度与粒子数的比例关系。还显示了一些二分实例，它们具有对噪声非常强的纠缠。我们还将讨论计量有用性与贝尔不等式违背的关系。我们发现，不违反任何贝尔不等式的量子态在计量上可以胜过可分离态。我们用积极的部分转置以及非积极的部分转置来呈现这样的状态。