Torque sensors such as the torsion balance enabled the first determination of the gravitational constant by Henri Cavendish¹ and the discovery of Coulomb’s law. Torque sensors are also widely used in studying small-scale magnetism^2,3, the Casimir effect⁴ and other applications⁵. Great effort has been made to improve the torque detection sensitivity by nanofabrication and cryogenic cooling. Until now, the most sensitive torque sensor has achieved a remarkable sensitivity of 2.9 × 10⁻²⁴ N m Hz^−1/2 at millikelvin temperatures in a dilution refrigerator⁶. Here, we show a torque sensor reaching sensitivity of (4.2 ± 1.2) × 10⁻²⁷ N m Hz^−1/2 at room temperature. It is created by an optically levitated nanoparticle in vacuum. Our system does not require complex nanofabrication. Moreover, we drive a nanoparticle to rotate at a record high speed beyond 5 GHz (300 billion r.p.m.). Our calculations show that this system will be able to detect the long sought after vacuum friction^7,8,9,10 near a surface under realistic conditions. The optically levitated nanorotor will also have applications in studying nanoscale magnetism^2,3 and the quantum geometric phase¹¹.

扭力天平等扭矩传感器使亨利卡文迪许^一号首次确定了引力常数并发现了库仑定律。扭矩传感器还广泛用于研究小规模磁性^2,3、卡西米尔效应⁴和其他应用⁵。通过纳米加工和低温冷却，人们已经做出了巨大的努力来提高扭矩检测灵敏度。迄今为止，最灵敏的扭矩传感器已在稀释制冷机^{6中的毫开尔文温度下实现了 2.9 × 10 -24}  N m Hz ^-1/2的卓越灵敏度。在这里，我们展示了一个扭矩传感器达到 (4.2 ± 1.2) × 10 ^-27  N m Hz的灵敏度^-1/2在室温下。它是由真空中的光学悬浮纳米粒子产生的。我们的系统不需要复杂的纳米加工。此外，我们驱动纳米粒子以超过 5 GHz（3000 亿转/分）的创纪录高速旋转。我们的计算表明，该系统将能够在现实条件下检测表面附近长期寻求的真空摩擦^{7、8、9、10 。}光学悬浮纳米转子也将应用于研究纳米级磁性^2,3和量子几何相¹¹。