Pristine quantum light source created at the edge of silicon chip
(PHYSorg.com Physics)

The smallest amount of light you can have is one photon, so dim that it`s pretty much invisible to humans. While imperceptible, these tiny blips of energy are useful for carrying quantum information around. Ideally, every quantum courier would be the same, but there isn`t a straightforward way to produce a stream of identical photons. This is particularly challenging when individual photons come from fabricated chips.