The suspended nanoparticle can spin more than 300 billion times a minute. ie. 5 GHz.

A twirling nanoparticle, suspended in a laser beam inside of a vacuum, can measure tiny twisting forces, making it the most sensitive detector of torque yet created. Researchers say the device could one day detect an elusive quantum effect called vacuum friction.

When operated for 100 seconds, the sensor could measure torques as small as about 0.4 trillionths of a quadrillionth of a Newton-meter. For comparison, one Newton-meter is the approximate amount of torque needed to twist a cap off a soda bottle. The device is around 700 times as sensitive as the previous best torque sensor.

An object spinning rapidly in empty space feels drag — despite being surrounded by nothingness. The effect is predicted to arise from interactions of the spinning object with electromagnetic fields that, according to quantum mechanics, appear and disappear constantly, even in empty space.

https://www.sciencenews.org/article/new-torque-detector-could-spot-quantum-friction-vacuum

Looks like a great way to test the quantum vacuum. The torque effect due to virtual particles in a vacuum is expected to affect magnetars.

https://www.nature.com/articles/s41565-019-0605-9

Torque sensors such as the torsion balance enabled the first determination of the gravitational constant by Henri Cavendish and the discovery of Coulomb’s law. Torque sensors are also widely used in studying small-scale magnetism, the Casimir effect and other applications.

The previously best torque detector required temperatures of millikelvin. This one operates at room temperature.

In this experiment, we optically trap a silica nanoparticle (a nanosphere or a nanodumbbell consisting of two spheres attached together) in a vacuum chamber using a tightly focused 1,550-nm laser. The polarization of the trapping laser is controlled with a quarter waveplate. The modulation of an additional 1,020-nm laser is used to apply an external torque that will be measured. When the nanoparticle rotates, it changes the polarization of the trapping laser slightly.

So far, the relationship between frictional torque has been measured over a wide range of air pressures. down to 5 millionths of a Torr.(3 billionths of an atmosphere).

Here’s a weird one. The strength of the torque due to the quantum vacuum is predicted to increase with temperature. I wasn’t expecting that. To measure the torque due to the quantum vacuum, we want close proxumity of the spinner (200 to 300 nm) to an electrically conducting surface at room temperature or hotter, depending on the strength of the vacuum.