A University of Ottawa-Max Planck team produced entangled photon pairs directly from sunlight, marking a proof-of-principle alternative to the laser-driven setups that usually power quantum optics experiments.
Using a window-sized Fresnel lens, a funnel and a hair-width optical fiber, the researchers concentrated sunlight onto a crystal and isolated polarization so the light's messy colors and directions did not disrupt entanglement.
The photon pairs reached about 94% similarity to a perfectly entangled state and violated Bell's inequality, showing correlations that classical physics cannot explain.
The result could lower energy and hardware demands for quantum communication, sensing and computing, with researchers pointing to remote stations and satellites that could use abundant sunlight instead of onboard lasers.
The team said brightness and entanglement quality still need improvement before practical deployment, but the Optica study opens a new pump source for scalable quantum technologies.