Photon research has impact

Zane Johnson

“Star Wars” is a space fantasy, so it’s rare that legitimate scientific research bears any resemblance to its gadgets. However, researchers from Harvard University and the Massachusetts Institute of Technology have recently made a discovery about the most beloved “Star Wars” prop — the lightsaber.

Led by Mikhail Lukin, a physics professor at Harvard, and Vladan Vuleti, a physics professor at MIT, a group of researchers coaxed photons to bind into photonic molecules. Photons are discrete units of light.

“It sounds simple, you know, photons are little particles of light,” said Poul Jessen, a professor who specializes in optical physics at the UA, “but in reality, things are more complicated.”

Light bound in any sort of form is reminiscent of the most popular weapon in “Star Wars,” but not in a way that will put a lightsaber in fans’ hands any sooner.

“It’s not an inapt analogy to compare this to lightsabers,” Lukin told the Harvard Gazette. “When these photons interact with each other, they’re pushing against and deflecting each other. The physics of what’s happening in these molecules is similar to what we see in the movies.”

“What they have done in this experiment is that they have created a disturbance in the medium where the photon travels,” Jessen said, “and along with that photon travels an excitation where the atoms that make up the medium is put up into something called a Rydberg state.”

In a Rydberg atom, the electrons have been excited, making the atom huge.

“Now, this photon is traveling along and there’s this excitation bound to it. It’s called a polariton, the photon and its excitation,” Jessen said. “Now, if another one comes along, because these photons drag with them these very strong disturbances in the material, it’s those disturbances in the material that see each other.”

This research, published by the Center for Ultracold Atoms in Nature on Sept. 25, demonstrated behavior previously only described in theory. The findings are supported by their conformity to an equation derived by Austrian physicist Erwin Schrödinger, which describes the changing quantum (incredibly small) state of a physical system.

The existence of photonic molecules changes the way science perceives photons, and could change the way we think of computing.
“These photons are quantum objects,” Jessen said. “If you can use one photon to turn off and on another photon then, in principle, you have what you need to make something like a transistor for a quantum computer.”

A quantum computer also has the ability to create unbreakable codes.
“With quantum encryption systems, there’s no way you could eavesdrop. The laws of quantum physics prevent that,” Jessen said. “But to do that over long distances, you have to be able to do clever things with photons.”

Though we are still far from cutting the Thanksgiving turkey with lightsabers, the idea of impenetrable security is enough to get anyone excited these days, and optical physicists are no exception. With these come other anticipated advances in technology; quantum computing could someday be a very real and very accessible possibility, and not in a galaxy far, far away.