Conventional classical sensors are approaching their maximum sensitivity levels in many areas. Yet these levels are still far from the ultimate limits dictated by quantum mechanics. Quantum sensors promise a substantial step ahead by taking advantage of the salient sensitivity of quantum states to the environment. Here, we focus on sensing rotations, a topic of broad application. By resorting to the basic tools of estimation theory, we derive states that achieve the ultimate sensitivities in estimating both the orientation of an unknown rotation axis and the angle rotated about it. The critical enhancement obtained with these optimal states should make of them an indispensable ingredient in the next generation of rotation sensors that is now blossoming.

传统的经典传感器在许多领域都接近其最大灵敏度水平。然而，这些水平仍远未达到量子力学所规定的最终极限。通过利用量子态对环境的显着敏感性，量子传感器有望向前迈出实质性的一步。在这里，我们专注于传感旋转，这是一个广泛应用的主题。通过使用估计理论的基本工具，我们推导出在估计未知旋转轴的方向和围绕它旋转的角度时达到最终灵敏度的状态。通过这些最佳状态获得的关键增强应该使它们成为现在正在蓬勃发展的下一代旋转传感器中不可或缺的组成部分。