PRESS RELEASE \u2014 Scientists have demonstrated that sunlight, as a natural light source, can generate quantum-entangled photon pairs. With their findings, the international research team challenges the long-held assumption that lasers are indispensable for preparing quantum states of light. The study recently published in Optica opens a path toward new sustainable and energy-efficient photonic quantum technologies.<\/p>\n
Entangled photons are pairs of light particles that remain correlated in ways no classical physics can explain. They are a key resource for quantum communication, computing, and sensing. Such photon pairs are routinely produced through a process called spontaneous parametric down-conversion (SPDC), in which photons from a pump beam are converted inside a nonlinear crystal into pairs of daughter photons.<\/p>\n
Laser loses its distinctiveness<\/p>\n
For decades, lasers have been considered the only suitable pump source for this process, while sunlight was regarded an unviable source. This belief was rooted in two fundamental assumptions. First, the high optical coherence of lasers was considered essential. Optical coherence means that the light waves are in a fixed, synchronized temporal or spatial relationship to one another. It was assumed that the phase-stable electromagnetic fields are required for generating quantum correlations through SPDC. Second, it was assumed that lasers are the only light sources capable of delivering the optical power densities needed to drive nonlinear optical processes efficiently. Natural sunlight, however, is incoherent and much less intense than laser light. Due to these features, many scientists had dismissed sunlight as a viable pump for entanglement generation.\u00a0 Incoherence leaves room for entanglement<\/p>\n In optics, \u2018coherence\u2019 is not a single property. Light can be described by various defined physical parameters, known as degrees of freedom. Thus, light can act regularly in one degree of freedom while remaining disordered in another. For instance, a beam can be perfectly polarized yet completely incoherent in space and time. For SPDC, the pump\u2019s incoherence in one degree of freedom only limits entanglement in that same degree of freedom. For instance, position-momentum entanglement \u2013 a type of spatial entanglement \u2013 is known to vanish when the pump beam loses its spatial coherence. Such a relation does not hold when the targeted entanglement is found in a different degree of freedom than that of the pump beam\u2019s incoherence.<\/p>\n
In a collaborative research project by the Max Planck Institute<\/a> for the Science of Light (MPL), Max<\/a> Planck Center for Extreme and Quantum Photonics (MPC) and the University of Ottawa<\/a>, scientists have demonstrated for the first time that, contrary to the previously held scientific view, entangled photons can be generated from solar light.<\/p>\n![\"\"](\"https:\/\/www.newsbeep.com\/il\/wp-content\/uploads\/2026\/08\/Screenshot-2026-08-07-at-9.01.47-AM-1024x552.png\")
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