University of Ottawa researchers made entangled photons skipping the laser
Scientists at the University of Ottawa, collaborating with researchers from the Max Planck Institute for the Science of Light and the Max Planck Center for Extreme and Quantum Photonics, have achieved quantum entanglement using sunlight for the first time. The team challenges the decades-long assumption that lasers are essential for creating correlated photon pairs, a key resource for quantum technologies. “As long as the pump beam is perfectly polarized, its spatial or temporal incoherence should not preclude the generation of polarization entanglement,” explains Dr. Cheng Li, a PhD graduate from the University of Ottawa. This breakthrough demonstrates that even the lower intensity and incoherence of sunlight can efficiently drive the necessary nonlinear optical processes, potentially leading to more sustainable photonic quantum systems. Sunlight Challenges Laser Dominance in SPDC Entanglement Achieving 94% fidelity, researchers have, for the first time, successfully generated quantum-entangled photons using only sunlight as a pump source, a result that challenges the decades-long reliance on lasers for this process. This breakthrough, detailed recently in Optica, demonstrates that the high optical coherence traditionally considered essential for spontaneous parametric down-conversion (SPDC) is not, in fact, indispensable, opening avenues for more sustainable quantum technologies. Previously, scientists believed that the intense, coherent beams produced by lasers were uniquely capable of driving the nonlinear optical processes necessary for efficient SPDC, where photons from the pump beam are converted into entangled pairs within a nonlinear crystal. However, the team’s work reveals that sunlight, despite being significantly less intense and inherently incoherent, can achieve comparable results when properly harnessed. The researchers focused on maintaining polarization while accommodating the inherent incoherence of sunlight in other degrees of freedom. To overcom
