Affolter M, Gilmore K A, Jordan J E, Bollinger J J
National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
Department of Physics, University of Colorado, Boulder, Colorado 80309, USA.
Phys Rev A (Coll Park). 2020 Nov;102(5). doi: 10.1103/PhysRevA.102.052609.
Trapped ions are sensitive detectors of weak forces and electric fields that excite ion motion. Here measurements of the center-of-mass motion of a trapped-ion crystal that are phase coherent with an applied weak external force are reported. These experiments are conducted far from the trap motional frequency on a two-dimensional trapped-ion crystal of approximately 100 ions, and determine the fundamental measurement imprecision of our protocol free from noise associated with the center-of-mass mode. The driven sinusoidal displacement of the crystal is detected by coupling the ion crystal motion to the internal spin degree of freedom of the ions using an oscillating spin-dependent optical dipole force. The resulting induced spin precession is proportional to the displacement amplitude of the crystal, and is measured with near-projection-noise-limited resolution. A 49 pm displacement is detected with a signal-to-noise ratio of 1 in a single experimental determination, which is an order-of-magnitude improvement over prior phase-incoherent experiments. This displacement amplitude is 40 times smaller than the zero-point fluctuations. With our repetition rate, an displacement sensitivity is achieved, which implies and sensitivities to forces and electric fields, respectively. This displacement sensitivity, when applied on-resonance with the center-of-mass mode, indicates the possibility of weak force and electric field detection below 10 yNion and 1 nVm, respectively.
囚禁离子是激发离子运动的弱力和电场的灵敏探测器。本文报道了与外加弱外力相位相干的囚禁离子晶体质心运动的测量结果。这些实验是在远离陷阱运动频率的情况下，在一个由大约100个离子组成的二维囚禁离子晶体上进行的，并且确定了我们的协议中与质心模式相关的无噪声基本测量精度。通过使用振荡的自旋相关光偶极力将离子晶体运动耦合到离子的内部自旋自由度，来检测晶体的驱动正弦位移。由此产生的诱导自旋进动与晶体的位移幅度成正比，并以接近投影噪声极限的分辨率进行测量。在单次实验测定中，以1的信噪比检测到49皮米的位移，这比之前的非相位相干实验有了一个数量级的提高。这个位移幅度比零点涨落小40倍。以我们的重复率，实现了位移灵敏度，这分别意味着对力和电场的灵敏度为 和 。当与质心模式共振应用时，这种位移灵敏度表明分别在低于10 yN/离子和1 nV/m的情况下检测弱力和电场的可能性。
