The first ghost image using sun as a light source

This article reports first experimental demonstration on two-photon ghost imaging using the sun as a light source. This experimental results raises a fundamentally important question about whether the nonlocal ghost-imaging effect of classical thermal light is caused by quantum-mechanical two-photon interference. Ghost imaging using the Sun as a light source could also achieve spatial resolution equivalent to that of a classical imaging system taking pictures at a distance of 10km with a 92m-diameter lens.