New light form could lead to better quantum computing

BY JOSEPH SCALISE
Posted on FEB 13, 2019

Researchers have used photon interactions to create a new form of light.

A group of researchers from the Massachusetts Institute of Technology and Harvard University have created a new form of light that shows photons are able to bind together, according to a studyin the journalScience.

Typically, photons -- the particles that make up light -- do not interact with each other. In fact, if scientists put two into each other's paths they will still find a way to pass by without touching. This new study changes that notion by revealing that photons can interact and bind together in groups of two or three.
To make this discovery, the team shone a weak laser beam through a dense cloud of the ultracold atoms, which then caused the photons to bind into either pairs or triplets.The photons attracted to each other, and the bound ones also appeared to acquire some mass during the process. That additional weight slowed down their speed by about 100,000 times.

Such interactions are completely new, and created a type of photonic matter previously unknown to science.

"The interaction of individual photons has been a very long dream for decades," said study co-author Vladan Vuletic, a researcher at the Massachusetts Institute of Technology, according toInternational Business Times. "Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers. If photons can influence one another, then if you can entangle these photons, and we've done that, you can use them to distribute quantum information in an interesting and useful way."

While the team is not exactly sure why the interaction occurred in the way that it did, they believe it might be because as a single photon moves through the cloud of rubidium atoms, it briefly lands on a nearby atom before skipping to another. However, if another photon is also moving through the cloud, it can sit on a rubidium atom as well.

That then forms a polariton, which is part photon and part atom. From there, two polaritons can interact through their atomic component. Not only does that work with two protons, it can also work with three to create an even stronger bond.

This new type of light has a lot of potential, especially in the world of quantum computing. The team hopes to expand on their research and see what other interactions they can find moving forward.

"It's completely novel in the sense that we don't even know sometimes qualitatively what to expect," added Vuletic, in a statement. "With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light? Or will something else happen? It's very uncharted territory.