Speeding particles in the sights of a laser
It might be easier to track tiny particles in the future – even when they hurtle along with the speed of a rifle bullet. This is thanks to researchers working with Christoph Marquardt and Gerd Leuchs at the Max Planck Institute for the Science of Light, who have discovered that these particles can be tracked with a radially polarized laser beam. In radially polarized light, the oscillation planes of the light waves arrange themselves like the spokes of a wheel. When the researchers cause a particle to fly through such a laser beam, they are able to determine its position several billion times per second by measuring the polarization of the beam. The physicists exploit the fact that the polarization of the laser beam and its spatial structure are classically entangled with each other. Up to now, the path of very fast objects, for example, can only be observed with...