They've done it.

They've finally worked out how to make a lightsaber. Kind of.

Physicists at Harvard and MIT have discovered a way of binding photons together in such a way they behave like the legendary Star Wars weapons.

lightsaber

The stuff of dreams

When blasting photons through a cloud of rubidium atoms, Harvard physics professor Mikhail Lukin and MIT physics professor Vladan Vuletic noticed they stuck together and formed a molecule.

Lukin said: "It's not an in-apt analogy to compare this to lightsabers.

"When these photons interact with each other, they're pushing against and deflect each other. The physics of what's happening in these molecules is similar to what we see in the movies."

The results have surprised the physicists as accepted wisdom states photons are massless particles that don't interact with each other.

The effect is due to something called the Rydberg Blockade which states when an atom is excited, atoms nearby cannot be excited to the same degree.

As a pair of photons move through the super-cooled rubidium cloud, the first excites an atom but has to move forward before the second can do the same.

This results in the two photons both pushing and pulling each other through the cloud. The scientists hope to use the discovery to further knowledge of quantum physics.

Lukin said: "We do this for fun, and because we're pushing the frontiers of science. But it feeds into the bigger picture of what we're doing because photons remain the best possible means to carry quantum information.

"The handicap, though, has been that photons don't interact with each other."

The end result? Possibly not cool, luminous and deadly hand-held weapons but a quantum supercomputer.