英国苏塞克斯大学Hensinger, W. K.团队近日研究了磁场梯度下的超灵敏单离子电测法。这一研究成果发表在2025年6月11日出版的《自然—物理学》杂志上。

被捕获离子中的超精细能级提供了长寿命的自旋态。此外，这些带电粒子的运动与电场扰动强烈耦合。这些特性使捕获离子成为电场量子传感的有吸引力的平台。然而，自旋态与电场没有很强的内在耦合，限制了可实现的灵敏度。研究组通过使用静磁场梯度来放大电场扰动和自旋态之间的耦合。 

由此，由施加的电场扰动引起的被捕获离子的位移被映射到内部自旋态能级分裂的瞬时变化。电场与自旋的这种梯度介导耦合使得能够使用成熟的磁测协议进行电测法，从而可以实现对直流和交流电场的极其灵敏的测量。研究组还采用了旋转框架弛豫技术，并演示了该量子传感器作为电场噪声频谱分析仪的使用。最后，他们描述了一组硬件修改，能够将灵敏度进一步提高六个数量级。

附：英文原文

Title: Ultrasensitive single-ion electrometry in a magnetic field gradient

Author: Bonus, F., Knapp, C., Valahu, C. H., Mironiuc, M., Weidt, S., Hensinger, W. K.

Issue&Volume: 2025-06-11

Abstract: Hyperfine energy levels in trapped ions offer long-lived spin states. In addition, the motion of these charged particles couples strongly to electric field perturbations. These characteristics make trapped ions attractive platforms for the quantum sensing of electric fields. However, the spin states do not exhibit a strong intrinsic coupling to electric fields, lim iting the achievable sensitivity. Here, we amplify the coupling between electric field perturbations and the spin states by using a static magnetic field gradient. Displacements of the trapped ion resulting from the applied electric field perturbations are thereby mapped to an instantaneous change in the energy-level splitting of the internal spin states. This gradient-mediated coupling of the electric field to the spin enables the use of well-established magnetometry protocols for electrometry, making it possible to achieve extremely sensitive measurements of d.c. and a.c. electric fields. We also employ a rotating-frame relaxometry technique and demonstrate the use of our quantum sensor as an electric field noise spectrum analyser. Finally, we describe a set of hardware modifications that are capable of achieving a further improvement in sensitivity by up to six orders of magnitude.

DOI: 10.1038/s41567-025-02887-9

Source: https://www.nature.com/articles/s41567-025-02887-9