Ultra-low Velocity Measurement By Weak-value Amplification

The accurate measurement of ultra-low velocity plays an important role in scientific research and engineering applications. The velocity measurements using laser Doppler velocimetry nowadays. The principle is the movement of objects can produce Doppler frequency shift, we can measure the speed of the objects when we know the frequency shift. However, the current minimum speed which laser Doppler velocimetry measurements can be limited, about um/s level, for a smaller velocity which less than um/s, we have no effective means.This paper presents a ultra-low velocity measurement scheme based on quantum weak measurement theory. Specifically, we use quantum weak value amplification technology, via the laser Doppler effect and interferometer, to amplify the small Doppler shift caused by the ultra-low velocity moving objects, and to convert it to time interval in temporal to be measured. Thereby, to increase the accuracy of velocity measurement to um/s. In this paper, we use the Michelson interferometer to achieve the conversion between Doppler frequency shift caused by the movement of objects and the pulse time interval, and get the relationship between the moving velocity and the time interval theoretically. We built the experimental system and completed the experiment, and the lowest velocity we measured was 0.076um/s. This article provides a new method for ultra-low velocity measurements at a higher level, gives some reference theoretical and experimental design, expands the use of quantum weak measurement technology, and has great value in engineering applications and scientific research.