Lasers are no longer required to produce quantum entanglement, physicists say, after achieving the state using sunlight. In a laboratory experiment, an international team of researchers demonstrated that natural sunlight can produce quantum-entangled photon pairs.
The researchers recently published their quantum entanglement study in Optica, showing that lasers aren’t the only game in town. The work could herald a new energy-efficient approach to sustainable quantum technologies, both on Earth and in space.
Quantum technologies such as computing, communications, and sensing rely on the strange principles of quantum mechanics, which often defy explanations rooted in classical physics. Typically, quantum technologies use lasers to convert photons inside a nonlinear crystal into entangled pairs through a process called spontaneous parametric down-conversion (SPDC).
Prior to this work, using sunlight to produce quantum entanglement in photons was largely considered impractical. Researchers had assumed that SPDC depended heavily on phase-stable electromagnetic fields, requiring the high coherence of laser beams. Scientists also believed that the intense power of lasers was crucial to the nonlinear processes that produce entanglement. By contrast, sunlight’s relative weakness and incoherence left it largely overlooked as a viable source for generating entangled photons.
Earlier work may have dismissed sunlight too readily because scientists had not fully considered the different dimensions of coherence. Across different parameters, sunlight can exhibit varying degrees of coherence. This means that while a beam of sunlight may be coherent in a particular property, such as polarization, it can still generate quantum entanglement along that parameter.
“As long as the pump beam is perfectly polarized, its spatial or temporal incoherence should not preclude the generation of polarization entanglement,” said lead author Cheng Li in a statement.
“The trick to harnessing sunlight is to keep different degrees of freedom of light from influencing each other during the process,” Li added. “This means that sunlight is perfectly capable of generating entangled photons, as long as one can concentrate enough sunlight into a nonlinear crystal to induce SPDC.”
In a natural environment, sunlight spreads across a broad area rather than remaining tightly focused like a laser beam. Efficiently directing it through a nonlinear optical crystal, only a few millimeters wide, therefore presents a significant challenge.
To overcome this obstacle, the researchers constructed a sunlight concentration system that collects light across a 1.4-square-meter surface and focuses it down to approximately the width of a human hair. The specialized solar concentrator is conical rather than flat and is constructed from glass. As sunlight reflects repeatedly across the interior surface on its way toward the cone’s tip, it becomes progressively concentrated and intensified before traveling through a single optical fiber to drive the SPDC process that generates quantum entanglement.
In laboratory tests, the researchers found that their sunlight-driven SPDC system produced performance comparable to that of a laser, achieving 94% fidelity. The efficiency of the entanglement process was also similar to that achieved with laser-based systems. Together, these findings challenge previous assumptions that SPDC requires highly coherent laser light to operate effectively.
The approach also eliminates the need to first convert electrical energy into optical energy, potentially reducing system complexity, heat generation, and points of failure.
“Sunlight is an abundant and reliable resource in many environments, especially in space. Being able to generate quantum-entangled photons directly from sunlight could enable simpler and more resilient quantum systems for satellites and future deep-space missions,” said Hanieh Fattahi, the study’s co-author, in a statement.
“We believe this work can inspire much new research in nonlinear and quantum optics,” Fattahi said, adding that this research “may in turn make sunlight-driven quantum technology more practical.”
The paper, “Generating Quantum Entanglement from Sunlight,” appeared in Science Advances on August 5, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.
When a team of physicists in Paris fabricated the world’s first temporal photonic crystal, they added a new dimension to humanity’s quest to control light: time. From lighting our homes to advanced fiber optics and lasers, humans have long worked to control light, and now researchers say that can be achieved in a fourth dimension.
Yannis Laplace led the team at the Laboratory of Irradiated Solids (LSI) in demonstrating the temporal photonic crystal, with the help of other European institutions, which was revealed in a recent paper published in Nature.
As light hits the crystal, a terahertz electromagnetic wave rapidly modulates its optical properties, producing a device that controls light over time without expending energy.
Controlling the properties of light for applications in telecommunications, sensors, and light sources is an active research field and is often reliant on crystals. In technical terms, a crystal is simply a regularly and periodically organized system. While we primarily think of translucent, shining crystals, they can be constructed of other forms of matter, such as gas or liquids, so long as their atoms arrange into regular, well-defined intervals.
How atoms arrange to form crystals grants their electrons and the photons they emit unique properties, including color and energy. Targeting photons specifically became an interest of scientists in the 1980s, with the development of photonic crystals, whose alternating materials each had unique effects on photons. These photonics gave rise to modern lasers, optical fibers, and photodetectors, technologies that have advanced considerably in recent decades.
In the last decade, researchers have experimented with a new kind of crystal: the time crystal. They are comprised of a unique form of matter in which particles repeat a continuous sequence—not just in the three physical dimensions, but also in time, without expending any energy.
The LSI team sought to combine photonic crystals with time crystals to develop a temporal photonic crystal that would control a light-matter interaction by alternating over time. Their work represents the first time such an idea has moved from the theoretical realm into the physical.
The device the researchers constructed operates in the high terahertz range, pushing light to oscillate 1000 billion times a second. It consists of micrometer-scale gold structures, shaped like battlements, leaving open cavities separated from an indium-antimony semiconductor by an insulating layer. The cavities between the gold structures trap light photons.
To demonstrate their device in the real world, the LSI team bombarded it with terahertz laser pulses and recorded the material’s optical properties, modulating light over time. The effect was incredibly powerful, creating a strong modulation that alternated one billionth of a billionth of a second.
At the semiconductor layer, the researchers observed electrons forming from the light waves in what are called “surface plasmons,” oscillating with their effective mass. The greater their speed, the heavier these electrons become, producing the device’s optical modulations.
Beyond this observed phenomenon, the researchers suspect other interesting conditions may be occurring within the crystal. Some indirect evidence suggests that photons trapped inside the structure are amplified, although presently no direct observations have confirmed this. The team is continuing with experiments in hopes of eventually capturing this photon trapping phenomenon.
Laplace and his colleagues see these unique time crystals as eventually being a pathway toward the creation of terahertz-scale light sources and detectors, which would fit between those of electronics and visible light frequencies.
The paper, “Plasmonic Metamaterial Time Crystal,” appeared in Nature on July 29, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org.
A marine biologist studying the photophores of a bioluminescent fish species found needle-shaped guanine crystals that scatter and redirect light instead of merely reflecting it, a discovery that could inspire more efficient biomedical and optical devices.
The post Bioluminescent Deep-Sea Fish Use Crystal ‘Prisms’ to Recycle Their Own Glow appeared first on Sci.News: Breaking Science News.
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