Star Wars fans take note: Researchers at Harvard University and MIT have outshined the "force" by discovering a previously unobserved state of matter by binding photons together into molecules – the result of which is basically a real-life lightsaber similar to what was used in the epic film series.
The discovery -- which until now has only been imagined in the realms of science fiction – goes against what scientists previously understood of photons: that elementary light particles are massless loners that do not interact with each other.
"Most of the properties of light we know about originate from the fact that photons are massless, and that they do not interact with each other," said Harvard professor of physics Mikhail Lukin in a statement earlier this week.
To create the never-before-seen state of matter, researchers fired a couple of photons into a cloud of rubidium – a chemical element belonging to the metal group – in a vacuum chamber cooled to just a few degrees above absolute zero.
When the photons exited the other side of the cloud of atoms, Lukin and his colleagues were surprised to see the pair emerge as a single molecule.
"What we have done is create a special type of medium in which photons interact with each other so strongly that they begin to act as though they have mass, and they bind together to form molecules," explained Lukin.
He said this type of "photonic" brotherhood is a result of a phenomenon called the Rydberg blockade, which states that when an atom has energy imparted to it, nearby atoms cannot be excited to the same degree.
This means that as the pair of photons moved through the cloud of atoms, the first photon excited atoms, but had to move forward before the second photon could do the same.
In essence, the pair of photons pushed and pulled each other through the cloud.
"It's a photonic interaction that's mediated by the atomic interaction," Lukin said. "That makes these two photons behave like a molecule, and when they exit the medium they're much more likely to do so together than as single photons."
But despite the discovery's obvious applications for Hollywood, Lukin says his team is hoping to use their newly discovered state of matter in the advancement of quantum computing.
"It feeds into the bigger picture of what we're doing because photons remain the best possible means to carry quantum information."
