CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, 230026, China.
Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, 230026, China.
Nat Commun. 2018 Jan 8;9(1):93. doi: 10.1038/s41467-017-02487-z.
Improving the precision of measurements is a significant scientific challenge. Previous works suggest that in a photon-coupling scenario the quantum fisher information shows a quantum-enhanced scaling of N, which in theory allows a better-than-classical scaling in practical measurements. In this work, utilizing mixed states with a large uncertainty and a post-selection of an additional pure system, we present a scheme to extract this amount of quantum fisher information and experimentally attain a practical Heisenberg scaling. We performed a measurement of a single-photon's Kerr non-linearity with a Heisenberg scaling, where an ultra-small Kerr phase of ≃6 × 10 rad was observed with a precision of ≃3.6 × 10 rad. From the use of mixed states, the upper bound of quantum fisher information is improved to 2N. Moreover, by using an imaginary weak-value the scheme is robust to noise originating from the self-phase modulation.
提高测量精度是一个重大的科学挑战。先前的工作表明，在光子耦合情况下，量子 Fisher 信息显示出 N 的量子增强缩放，这在理论上允许在实际测量中实现优于经典的缩放。在这项工作中，我们利用具有较大不确定性的混合态和对附加纯系统的后选择，提出了一种提取这种量子 Fisher 信息的方案，并在实验中实现了实际的海森堡缩放。我们进行了单次光子 Kerr 非线性的测量，实现了海森堡缩放，其中观察到超小的 Kerr 相位 ≃6×10 rad，精度 ≃3.6×10 rad。通过使用混合态，将量子 Fisher 信息的上限提高到 2N。此外，通过使用虚弱值，该方案对源自自相位调制的噪声具有鲁棒性。
