Sunlight Sparks Laser-Free Quantum Ghost Imaging
First demonstration of sunlight-pumped spontaneous parametric down-conversion (SPDC) paired with ghost imaging, producing quantum-correlated photons with a passive, sunlight-powered source. The setup achieved about 90.7% ghost-imaging visibility (near 95.5% with a 405 nm laser) and used a sun-tracking system and nonlinear crystal, suggesting potential for quantum imaging in remote or space environments while highlighting future gains from improved collection, crystal design, and reconstruction methods.