Photons Led Astray: Experiment Investigates Random Motion of Quantum Particles Science Daily (press release)
— Life would sometimes be so much easier if we were quantum particles. For example, if we were trying to find our way out of a strange town allowing chance telling us which way to go at every intersection. As objects of classical physics, this would mean becoming more and more lost in the centre of the road network. If we were particles that obeyed the laws of quantum mechanics, we would sooner or later find our way to the edge of town on the randomly-chosen route.
An international team headed by researchers at the Max Planck Institute for the Science of Light has now proven this experimentally. They have used polarized light -- light waves which oscillate in a particular plane -- to design a simple model for a quantum physical random walk. Their experiments could provide new insights into statistical processes such as photosynthesis, and help to accelerate search algorithms.
An experiment with a Galton board -- a board containing vertical pins arranged in a triangular pattern -- can demonstrate what a human would experience when wandering through a town on a path determined by chance. When a ball rolls over the board and strikes a pin positioned at a corner of the triangle, its path through the labyrinth of pins is determined by chance until it arrives at the triangle's base: At every step it takes through the labyrinth it is deflected by a pin to either the left or the right. Since it takes each of the two directions an equal number of times on average, it usually arrives in the centre of the base. Wandering through a labyrinth of streets, chance would similarly bring us to the centre of a town.
