Researchers from the Department of Physics at the University of Warsaw (UW) have made a discovery that could have implications for research into the interaction of light with matter. It is a step towards the observation of quantum backflow. The researchers’ findings have been published in the journal Optica.

The UW researchers superposed two beams of light ‘twisted’ in a clockwise direction, creating counterclockwise twists in small areas. 

“In classical mechanics, an object has a fixed position. Meanwhile, in quantum mechanics and optics, it can be in the so-called superposition of states, which means that a given object can be in two or more positions at the same time”, explains Dr Radek Łapkiewicz, head of the Quantum Imaging Laboratory at the UW Department of Physics.

It happens that particles in superposition may suddenly change direction and move backwards for a while or temporarily spin in the opposite direction. Physicists call such a phenomenon backward flow.

The researchers observed linear backflow in a very simple case, i.e. by superimposing two beams of light. 

Read more: 

https://opg.optica.org/optica/fulltext.cfm?uri=optica-10-9-1217&id=537322