A tiny switch for a few particles of light

The Jedi knights of the Star Wars saga are engaged in an impossible fight. This does not result from the superiority of the enemy empire, but from physics because laser swords cannot be used for fighting like metallic blades: beams of light don't feel each other. Until now, for a light beam to perceive another one, it has required a large chunk of material as intermediary, and very intense light. A team at the Max Planck Institute for the Science of Light has demonstrated for the first time a me