Nie Xinfang, Huang Jiahao, Li Zhaokai, Zheng Wenqiang, Lee Chaohong, Peng Xinhua, Du Jiangfeng
CAS Key Laboratory of Microscale Magnetic Resonance and Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China; Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei 230036, China; Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China.
Laboratory of Quantum Engineering and Quantum Metrology, School of Physics and Astronomy, Sun Yat-sen University (Zhuhai Campus), Zhuhai 519082, China.
Sci Bull (Beijing). 2018 Apr 30;63(8):469-476. doi: 10.1016/j.scib.2018.03.007. Epub 2018 Mar 20.
Nonlinear quantum metrology may exhibit better precision scalings. For example, the uncertainty of an estimated phase may scale as Δϕ∝1/N under quadratic phase accumulation, which is 1/N times smaller than the linear counterpart, where N is probe number. Here, we experimentally demonstrate the nonlinear quantum metrology by using a spin-I (I>1/2) nuclear magnetic resonance (NMR) ensemble that can be mapped into a system of N=2I spin-1/2 particles and the quadratic interaction can be utilized for the quadratic phase accumulation. Our experimental results show that the phase uncertainty can scale as Δϕ∝1/(N-1) by optimizing the input states, when N is an odd number. In addition, the interferometric measurement with quadratic interaction provides a new way for estimating the quadrupolar coupling strength in an NMR system. Our system may be further extended to exotic nonlinear quantum metrology with higher order many-body interactions.
非线性量子计量学可能展现出更好的精度标度。例如，在二次相位积累下，估计相位的不确定性可能按Δϕ∝1/N标度，这比线性情况小1/N倍，其中N是探测数。在此，我们通过使用一个自旋I（I>1/2）核磁共振（NMR）系综来实验演示非线性量子计量学，该系综可映射到一个由N = 2I个自旋1/2粒子组成的系统，且二次相互作用可用于二次相位积累。我们的实验结果表明，当N为奇数时，通过优化输入态，相位不确定性可按Δϕ∝1/(N - 1)标度。此外，具有二次相互作用的干涉测量为估计NMR系统中的四极耦合强度提供了一种新方法。我们的系统可进一步扩展到具有高阶多体相互作用的奇异非线性量子计量学。
