Taylor, M.A. et al. Nat. Photonics 7, 229–233 (2013).

Laser-based particle tracking enables high-precision biological studies. Often it is used in combination with optical tweezers to trap a molecule and study its dynamics. The sensitivity of optical tracking experiments such as these is limited by noise because of the uncertainty in the number of photons, or shot noise. Increasing the intensity of the light can help but is not an ideal approach when dealing with biological specimens that can be damaged by high light levels. Taylor et al. report the use of a 'nonclassical' form of light called 'squeezed' light, which enabled tracking lipid granules in yeast cells with higher sensitivity by surpassing the quantum-noise limit. This approach provides a way to improve measurement sensitivity without increasing the risk of optical damage to the sample