Shooting photons through a rubidium gas cloud has some surprising results: photonic molecules. Are we one step closer to light crystals?

SeekerPublished: July 10, 2018Updated: July 11, 2018
Published: July 10, 2018Updated: July 11, 2018

Photons are unusual. When they’re not waves, they are massless particles that can travel at light speed. For decades it was also thought photons didn’t interact with each other, but recently researchers have discovered how to bind photons together as though they were molecules.

With flashlights you can cross the streams all you want. They don’t bounce off each other or cause every molecule in your body to explode because photons don’t much care for one another. Unless, they are fired through a ultracold cloud of rubidium atoms. When scientists from Harvard and MIT fired a weak laser through a rubidium cloud, they observed photons coming out the other side in pairs and triples.

They could also tell from how much the photons were oscillating that they weren’t just bunched up together coming out of the cloud -- they were bonded, like molecules. Making them photonic molecules. They could even tell how strong the bond was based on their oscillation frequencies. However, not all of this is breaking news. Back in 2013, scientists fired a blue laser at ultracold rubidium gas and observed the photons forming pairs when they came out the other side.

What’s new this time are that the photons formed the trios. Scientists weren’t sure if it was even possible to form groups of three interacting photons. It’s not only possible, but three photons interact even more strongly than pairs of photons. To explain how this happens, researchers believe that as the photons travel through the rubidium cloud, they’re briefly captured by the atoms to form an atom-photon hybrid called a Rydberg polariton.

This video, "Shooting photons through a rubidium gas cloud has some surprising results: photonic molecules. Are we one step closer to light crystals?", first appeared on seeker.com.

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