To the dismay of "Star Wars" fans everywhere, physicists have long cried foul about the science of building real-life lightsabers. According to conventional physics, photons don't behave like regular particles of matter. They are massless particles, and can't interact with one another. It's therefore impossible to build anything out of light with a solid structure, such as a lightsaber.
But a breakthrough new discovery from researchers at the Harvard-MIT Center for Ultracold Atoms could change everything, according to Phys.org. They have discovered how to make individual photons interact and bind together into molecular structures. Not only does this represent a whole new state of matter, but these light molecules can potentially be shaped to form solid structures — in other words, lightsabers!
"It's not an in-apt analogy to compare this to lightsabers," said Harvard physics professor Mikhail Lukin. "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."
While the discovery blows the roof off our traditional understanding of light, it's not out of nowhere. Theories have been proposed about the possibility for these strange types of bound photonic states before, but until now those theories have been impossible to test.
To get the photons to interact, researchers took atoms of rubidium and put them into a specialized vacuum chamber capable of cooling the atoms down to an ultra-cold temperature. They then used a laser to fire individual photons into the frozen cloud of atoms. As the photons passed through the medium, they slowed down. By the time they exited the medium, they had become bound together.
The reason they bind together while traveling through the cold atom medium is due to something called a Rydberg blockade. Basically, as the photons pass through the medium, they trade off exciting nearby atoms, effectively acting in tandem to clear a path through for one another.
"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."
The physics of how it works is complicated, but the potential applications for the discovery are downright mind-blowing. For instance, it could change the game in regards to quantum computing. Photons are the best possible means to carry quantum information, but until now it was unclear how to make photons interact.
A far more mesmerizing application for the discovery, however, is that it means light can be shaped into solid structures. Lukin suggested that the system might one day be used to create complex three-dimensional structures, such as crystals, wholly out of light.
Light crystals would be trippy, to be sure. But lightsabers — a very real potential application as well — would be even cooler.
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