标题： 量子计量学：具有束缚纠缠的海森堡极限 显示英文标题

标题： Quantum metrology: Heisenberg limit with bound entanglement

摘要： 量子计量学可以极大地提高参数估计的精度。 然而，它似乎对噪声极其敏感。 束缚纠缠态是含有大量噪声的态，这使得它们几乎无法用于所有量子信息任务。 在这里，我们提供了一个反直觉的例子，即一类可以用于量子增强计量学的束缚纠缠态。 我们证明这些态提供的优势与最大纠缠态一样大，并且渐近地达到海森堡极限。 此外，所用态的纠缠非常微弱，这反映在其所谓的可解锁性特性上。 最后，我们发现了一些情况，量子费舍尔信息的行为表明存在束缚纠缠，而一个著名的强相关贝尔不等式类却未能检测到。 这就提出了一个问题：在量子计量学中，亚光子噪声精度是否需要（如果需要的话，程度如何）违反局域实在论。 显示英文摘要

摘要： Quantum metrology allows for a huge boost in the precision of parameters estimation. However, it seems to be extremely sensitive on the noise. Bound entangled states are states with large amount of noise what makes them unusable for almost all quantum informational tasks. Here we provide a counterintuitive example of a family of bound entangled states which can be used in quantum enhanced metrology. We show that these states give advantage as big as maximally entangled states and asymptotically reach the Heisenberg limit. Moreover, entanglement of the applied states is very weak which is reflected by its so called unlockability poperty. Finally, we find instances where behaviour of Quantum Fisher Information reports presence of bound entanglement while a well-known class of strong correlation Bell inequality does not. The question rises of whether (and if so, then to what degree) violation of local realism is required for the sub-shot noise precision in quantum metrology.