What is angular momentum?

Simply put, angular momentum measures how much a beam of light is rotating.

“Angular momentum measures how much something is rotating,” physicist John Donegansaid. “For a beam of light, although traveling in a straight line it can also be rotating around its own axis. So when light from the mirror hits your eye in the morning, every photon twists your eye a little, one way or another.”

This is a well understood concept in physics, but until now, physicists didn’t think it was possible to have light with an angular momentum value less than Planck’s constant.

The experiment:

The researchers passed a beam of light through a set of crystals that compressed it into a rotating, hollow cylinder.

Usually a phenomenon called “quantum effects” causes angular momentum to fluctuate a little, but it always stays a whole number. So when the physicists measured the angular momentum of this beam of light, they were surprised to discover a value half that of Planck’s constant.

We’ll need more research before we can start harnessing this new form of light, but it might someday lead to faster and more secure internet connections.

“Our priority is to see what the implications of this are for the science — what else might light do that follows from this,” Eastham told Mic in an email. “It’s always hard to speculate about potential uses as they’re years away. But as almost all our telecommunications is based on light, and we’re exploring these basic properties of light, there could be uses there.”