New State of Matter in Photons May Spur Quantum Computers, Lightsabers?

Scientists at MIT and Harvard have created a novel form of matter made from photons. Is that not exciting enough? Well, the new type of photonic molecule has been described by one of the researchers as similar to what you'd expect in light sabers.

A group of scientists at the Havard-MIT Center for Ultracold Atoms, led by MIT Professor of Physics Vladan Vuletic and Harvard Professor of Physics Mikhail Lukin, have created a state of matter out of photons that bind together. Photons are the elementary particles of light and electromagnetic radiation.

The team was experimenting with slowing photons down when they found they had gotten two photons to interact with each other in a push-pull nature.

This interaction is exciting because previously photons were thought to only be massless particles that did not interact like normal particles: Shoot two photons at each other (i.e., aim two beams of light down the same path) and you'll get nothing - the beams of light will just pass through one another. You can test it at home - just pay attention to the lack of collisions happening the next time you're driving at night with your headlights on.

"Most of the properties of light we know about originate from the fact that photons are massless, and they do not interact with each other," said Harvard's Mikhail Lukin to Phys.org. "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."

"Photonic molecules" is the term for the new form of light-matter created by the researchers, and, according to Lukin, it's not "an in-apt analogy to compare this to light sabers. 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."

Of course, don't expect the iSaber or Google Slash to be hitting store shelves in time for the holiday season. The research team achieved this photonic interaction in extreme lab conditions. Researchers took a vacuum chamber, filled it with rubidium atoms, and cooled the atomic cloud down to almost absolute zero. That's almost 459 degrees Fahrenheit below zero - a temperature at which particles slow down to an almost standstill.

Then they fired individual photons into the cloud of atoms. As a photon enters the cloud of (almost) frozen atoms, its energy passes along to nearby atoms, which slows the photon, but the photon still exits as a photon (this part, we already knew). But when two photons were fired into the cloud, Lukin and the research team were surprised to see that, instead of both photons exiting individually, they exited together as a single bound molecule.

Besides being an incredible demonstration of, until now, theoretical concepts of photon interaction - and a fun thing to think about with regard to light sabers - the discovery could have a big impact on quantum computing, which requires quantum particles to interact with each other.

"What we demonstrate with this process allows us to do that," Lukin said. "Before we make a useful, practical quantum switch or photonic logic gate we have to improve the performance, so it's still at the proof-of-concept level, but this is an important step. The physical principles we've established here are important."

Of course, the physical principles for a light saber have also been established by the discovery, so why not move ahead on both?

On second thought, maybe not.

The team published their findings in the September 25 issue of the journal Nature.