混合态的量子精密测量：当恢复丢失的信息比永远不丢失信息更好时
Quantum metrology with mixed states: When recovering lost information is better than never losing it
摘要：
量子增强计量学可以通过使探针与辅助系统纠缠、使探针穿过干涉仪并且随后在探针和辅助系统两者上进行测量来实现。在概念上，这对应于执行具有（混合）探测状态的纯化的计量。我们通过量子费舍尔信息演示了如何设计混合态，其纯化是一个很好的量子资源。特别是，我们给出了混合状态的例子与纯化，允许（近）海森堡限制计量，并提供例子纠缠哈密顿可以产生这些状态。最后，我们提出了实现这些灵敏度所需的最佳测量和参数估计过程（即饱和量子Cramér-Rao界）。由于具有可比性的纯态通常很难产生，因此使用这种纠缠和测量辅助系统的方法可能会更容易。一个可能是这种情况的例子是原子干涉术，其中与光学系统的纠缠可能比产生非经典原子态所需的原子相互作用更容易工程化。
英文摘要：
Quantum-enhanced metrology can be achieved by entangling a probe with an auxiliary system, passing the probe through an interferometer, and subsequently making measurements on both the probe and auxiliary system. Conceptually, this corresponds to performing metrology with the purification of a (mixed) probe state. We demonstrate via the quantum Fisher information how to design mixed states whose purifications are an excellent metrological resource. In particular, we give examples of mixed states with purifications that allow (near) Heisenberg-limited metrology, and provide example entangling Hamiltonians that can generate these states. Finally, we present the optimal measurement and parameter-estimation procedure required to realize these sensitivities (i.e. that saturate the quantum Cramér-Rao bound). Since pure states of comparable metrological usefulness are typically challenging to generate, it may prove easier to use this approach of entanglement and measurement of an auxiliary system. An example where this may be the case is atom interferometry, where entanglement with optical systems is potentially easier to engineer than the atomic interactions required to produce nonclassical atomic states.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
