Metasurfaces forge new paths in quantum spaces

The notion of a path in quantum mechanics has fuelled many debates on the very nature of what quantumness is. Although traditionally associated with physical paths, such as double slits, it can be far more abstract. Now Yan Wang and colleagues demonstrate exotic trajectories in an abstract quantum space built from the Bloch sphere of a locally entangled photon, while shaping the path using its non-local entangled partner as a control. The steering and directing along these new paths is enabled by cascaded metasurfaces, demonstrating the myriad of possibilities that emerge when structured matter meets quantum structured light.