Researchers generate quantum entanglement using sunlight
Using natural light to produce entangled photons offers potential route toward more energy-efficient quantum technologies
Optica
image:
Using a new cone-shaped solar concentrator, researchers showed that sunlight can be used to create entangled photons. This could one day enable satellites to create secure encryption keys using the sunlight already abundant in space
view moreCredit: Florian Sterl
WASHINGTON — Today’s quantum technologies rely on energy-intensive lasers, raising concerns that scaling them up could further increase energy demands. In new work, researchers have demonstrated that quantum entanglement between photons can be generated directly from sunlight, offering a potential alternative.
“Quantum entanglement is crucial for applications such as secure communication, ultra-precise sensing and high-performance computation,” said Cheng Li, a recent graduate of the University of Ottawa in Canada. “Our work shows that abundant natural light sources can be used for quantum entanglement, opening the possibility of more energy-efficient and accessible quantum technologies.”
In Optica, Optica Publishing Group’s journal for high-impact research, the researchers report that the entanglement they achieved using sunlight was comparable to laser-based approaches after accounting for differences in the bandwidth of the input light.. The advance combined theoretical advances from Robert Boyd’s team at the University of Ottawa with a new solar concentrator developed by Hanieh Fattahi’s team at the Max Planck Institute for the Science of Light (MPL) in Germany.
“This technology could one day enable 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,” said Li, first author of the paper. “Sunlight-driven entanglement generation could also provide the crucial ingredient needed to scale up quantum computing without adding to the energy burden.”
Rethinking quantum light sources
For some time, scientists have thought that the strong correlations required to achieve photon entanglement could only be achieved with coherent light — meaning that the light waves stay synchronized, with their peaks and valleys aligned in a predictable pattern. This is why lasers, which produce highly coherent light in a single color, are typically used to create entangled photons.
In earlier work, Boyd’s team theoretically predicted and experimentally observed that incoherent light can produce quantum entanglement. Their experiments used an LED, which produces incoherent light, to generate polarization-entangled photons. This laid an important foundation by showing that light can remain disordered in one property — such as the directions it travels — while still producing photons that are entangled in another property, such as their polarization.
The research reported in the Optica paper takes this idea a step further by using sunlight, which is highly divergent and encompasses a broad range of colors. To create entanglement, the researchers used spontaneous parametric down-conversion (SPDC), a well-known process in which a pump beam interacts with a nonlinear crystal, causing individual photons to split into pairs that can become quantum entangled.
Instead of the traditional laser-based pump beam, they used sunlight that was highly polarized but still highly incoherent in space and time. In other words, the overall field of sunlight oscillated in the same direction but contained different-colored photons that could propagate in various directions.
“We designed our experimental setup so that differences introduced by the different colors and propagation directions didn’t influence the photons' polarization,” said Li. “As our theory predicts, if the entanglement lives only in polarization, then it should only depend on the pump’s orderliness in its oscillation direction and not on its direction or color. This allowed us to produce high-quality polarization entanglement from highly spatially and temporally incoherent sunlight.”
Another challenge was how to focus sunlight onto a tiny millimeter-sized nonlinear crystal. To solve this problem, Fattahi's team at MPL developed an all-glass solar concentrator. The cone-shaped device concentrates sunlight collected by a household window-sized Fresnel lens into an optical fiber the width of a human hair, allowing it to be focused onto the tiny nonlinear crystal that drives entanglement generation.
Putting the theory to the test
To test their theory and the solar concentrator, the researchers conducted an outdoor experiment at MPL. Using quantum state tomography to characterize the resulting quantum state, they found that the entanglement generated from sunlight was about 94% similar to a perfectly entangled state. Additionally, the photons produced during the experiment were correlated in such a way that violates Bell's inequality, indicating that the correlation has no classical explanation and must be a result of quantum entanglement.
Now that the proof-of-principle demonstration is complete, the researchers are working toward a field-deployable product by making improvements in brightness and the quality of entanglement.
Although this work used SPDC, the researchers say that the approach could be extended to other nonlinear optical methods, such as four-wave mixing, potentially opening new directions in quantum photonics research.
“Since the inception of this project, our idea has met with repeated doubt and pushback,” said Li. “Some world-renowned researchers in the field even questioned whether it would be possible to detect any photons — not to mention entangled photons — from sunlight-driven nonlinear optical processes. However, we trusted our calculations, continued improving the experimental setup and eventually showed that it was possible.”
Cheng Li is shown with the outdoor experimental setup. The sunlight concentration module, including the Fresnel lens and the solar concentrator, is mounted on a solar-tracking motor to ensure stable power delivery. The entanglement generation and detection setup, including the nonlinear crystal and the single-photon detectors, are shielded in an optical enclosure placed inside a blackout tent.
Credit
Jasvinder Brar, Max Planck Institute for the Science of Light
Method of Research
Experimental study
Subject of Research
Not applicable
Article Publication Date
6-Aug-2026
Machine learning assists in carbon dots research
HEP Data Cooperation Journals
image:
Overview of ML-assisted CDs research
view moreCredit: HIGHER EDUCATION PRESS
Carbon dots, as an important type of luminescent nanomaterial, have been widely applied. However, the synthesis-structure-property relationship of carbon dots has long lacked a comprehensible framework, which has restricted the on-demand design and controllable preparation. In recent years, machine learning has provided a data-driven new paradigm for solving this complexity, but related research still faces challenges such as scattered data, unclear task boundaries, and insufficient model interpretability.
This review systematically examines recent key advances in machine learning for CDs research, focusing on three core tasks: property prediction, synthesis and inverse design, and mechanism analysis. Furthermore, from the perspective of CDs application systems, the review systematically evaluates the practical enabling role of machine learning in CDs-related applications such as sensing, biomedicine, optoelectronics, and information encryption, clearly distinguishing between its role as a tool for performance optimization and its function as a key means for rational design of CDs materials. Finally, a future-oriented pathway for machine learning-driven CDs research is proposed.
This work provides a forward-looking path for machine learning-driven CD research, facilitating the transition of this field from trial-and-error based on experience to a rational design. The work entitled “Machine Learning for Carbon Dots: Capabilities, Limitations, and the Path Toward Rational Design” was published in Advanced Powder Materials (Available online on 22 May 2026).
Journal
Advanced Powder Materials
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
Machine Learning for Carbon Dots: Capabilities, Limitations, and the Path Toward Rational Design
Charged defects reshape grain growth in oxide ceramics
HEP Data Cooperation Journals
image:
Phase-field simulation of grain growth and skewed grain-size distribution in Fe-doped SrTiO3 oxide ceramics.
view moreCredit: HIGHER EDUCATION PRESS
Oxide ceramics such as strontium titanate and barium titanate play key roles in capacitors, actuators, sensors, memristors, and fuel-cell technologies. Their performance is strongly influenced by microscopic structural features formed during processing, particularly grain boundaries—the interfaces between neighboring crystal grains.
In Fe-doped SrTiO₃, doping introduces charged point defects, including oxygen vacancies and acceptor dopants. These defects can segregate at grain boundaries and form space-charge layers, which are difficult to observe directly during high-temperature sintering but can strongly affect grain-growth behavior and charge transport in the final ceramic.
To better understand these hidden processes, the authors developed a phase-field grain-growth model explicitly informed by defect chemistry. The model distinguishes the segregation energies and available site densities of oxygen vacancies and acceptor dopants in grain interiors and grain-boundary cores, while also accounting for the competition between defect diffusion and grain-boundary migration.
The model was benchmarked against established bicrystal descriptions, including the Mott–Schottky and Gouy–Chapman models. Simulations then revealed how defect-chemistry parameters govern the formation of space-charge layers, grain-boundary potentials, and grain-size evolution during sintering.
One important finding is that solute drag alone can drive grain growth away from the conventional log-normal behavior. The simulations produced skewed grain-size distributions even without considering grain misorientation or anisotropic grain-boundary mobility. This result provides new insight into the origin of abnormal grain growth in doped oxide ceramics and highlights the critical role of defect segregation.
The simulations also suggest that grain-boundary potentials can vary substantially throughout a polycrystalline microstructure. At later stages of grain growth, smaller grains tend to exhibit higher grain-boundary potentials and stronger blocking effects on ionic transport, whereas larger grains tend to show lower potentials. This heterogeneity may offer opportunities for microstructure design: conductivity could be enhanced by promoting current pathways that bypass blocking boundaries, while applications such as capacitors may benefit from maintaining smaller grains and preserving blocking grain boundaries.
The work, titled “A defect-chemistry-informed phase-field model of grain growth in oxide ceramics: application to Fe-doped SrTiO₃”, was published in Advanced Powder Materials (Available online on 29 April 2026).
Journal
Advanced Powder Materials
Method of Research
Experimental study
Subject of Research
Not applicable
Article Title
A defect-chemistry-informed phase-field model of grain growth in oxide ceramics: application to Fe-doped SrTiO3
No comments:
Post a Comment