A highly compact, low-energy device capable of switching the paths taken by light within photonic systems has been unveiled by physicists in the US and Switzerland. The new switch could provide a basis for artificial-intelligence (AI) systems that mimic human decisions, allowing for a diverse range of applications. "All-optical computers" use light instead of electronic signals to process information. In principle, they could be faster and much more energy efficient than conventional computers. However, it is proving very difficult to create compact and energy efficient photonic devices that can switch and process optical signals at high speeds. The new device was created by Chris Haffner and colleagues at the National Institute of Standards and Technology (NIST), ETH Zurich and the University of Maryland.