Entanglement is one of the best tricks in the magic box of quantum physics: two particles that are inextricably linked when measured, a key component of potential advances in computing, communication and sensing technologies. Scientists have a variety of methods to create entangled particles, often using light particles (photons). The standard way to entangle photons is to fire a high-energy laser into a specially configured crystal. It is a reliable and well-established method, and also requires power and, of course, access to an advanced laser. Now researchers at the University of Ottawa in Canada and the Max Planck Institute for the Science of Light in Germany have done what some had considered impossible: generate entangled photons from sunlight. (Li et al., Optica, 2026) Publishing their work in Optica, the team says the innovation could lead to entanglement technology that is cheaper and easier to deploy in “resource-constrained environments,” from remote research stations to orbiting satellites. that LED light could produce entangled photons, suggesting that incoherent light (light without the synchronicity and uniformity of lasers) had the potential to trigger this process. “Some world-renowned researchers in this field even wondered if this would be possible.” – Physicist Cheng Li The experimental setup included a window-sized Fresnel lens and a funnel that concentrated the collected sunlight into an optical fiber the width of a human hair. The focused light was then directed toward a crystal to perform the actual entanglement. frameborder=”0″ enable=”accelerometer; autoplay; writing on clipboard; encrypted media; gyroscope; picture in picture; web-share” referrerpolicy=”strict-origin-when-cross-origin” enablefullscreen> To address the incoherent (or ‘disordered’) characteristics of sunlight, including its direction and wavelength, the team focused on its polarization: the orientation of its oscillating electromagnetic field. By entanglement of this particular characteristic, the device ensured that the surrounding disorder of the light did not fundamentally prevent polarization entanglement. “We designed our experimental setup to So the differences introduced by different “colors and propagation directions did not influence the polarization of the photons,” Li says. “As our theory predicts, if entanglement occurs only in polarization, then it should only depend on the order of the pump in its direction of oscillation and not on its direction or color.” This allowed us to produce high-quality polarization entanglement from highly spatially and temporally incoherent sunlight. The particles were about 94 percent similar to a perfectly entangled state and violated Bell’s inequality, a standard sign that their correlations could not be explained by classical physics. Once entangled photons are created, they can retain their intrinsic bond even when separated by enormous distances. In principle, that could mean connecting giant telescopes, for example, or communications that can’t be intercepted. “This technology could one day allow satellites to create secure encryption keys using the sunlight already abundant in space, reducing the need for onboard lasers and much of the supporting hardware,” Li says. “Sunlight-driven entanglement generation could also provide the crucial ingredient needed to scale up quantum computing without increasing the energy burden.” entangled photons. (Florian Sterl) The researchers call this a “proof-of-principle demonstration”: We still don’t have a fully functioning sunlight-powered quantum entangler that can be shipped around the world or packaged into other technology. However, it is a promising development as a completely new type of pump source for photon entanglement. The quality of entanglement can be improved further, the researchers say, as can the brightness, essentially the rate at which entangled photons are produced. Related: We may already have the first hints of quantum gravity: hidden in plain sight. Breakthroughs can often be theorized long before practical tests arrive. “Some world-renowned researchers in this field even wondered whether it would be possible to detect photons (not to mention entangled photons) from nonlinear optical processes driven by sunlight,” Li says. “We were confident in our calculations, continued to improve the experimental setup, and finally showed that it was possible.” The research was published in Optica. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we take pride in our process, we are human. If you spot an error, please let us know.
