Theoretical Discovery Shines Photons in New Light

A study from Dartmouth College and SUNY Polytechnic suggests that split photons, called Majorana bosons, exist. The finding advances the fundamental understanding of light, and how it behaves, thanks to the proposed theory that relies on energy-leaking dissipating cavities that are coupled and filled with quantum packets of light. The research predicts that particle halves appear at the edges of such a synthetic platform.

“This is a major paradigm change of how we understand light in a way that was not believed to be possible,” said Lorenza Viola, the James Frank Family Professor of Physics at Dartmouth and the study’s senior researcher. “Not only did we find a new physical entity, but it was one that nobody believed could exist.”

Similar to how liquid water can change into ice or vapor under specific conditions, the research indicates that light can also exist in a different phase, one in which photons appear as two distinct halves.

“Water is water regardless of its liquid or solid form. It just behaves differently depending on physical conditions,” Viola said. “This is how we need to approach our understanding of light — like matter, it can exist in different phases.”

The photon halves are more like the two sides of a coin than pieces that can be physically pulled apart. The two parts make up a whole, yet they can be described and function as separate units.

“Every photon can be thought of as the sum of two distinct halves,” said Vincent Flynn, a Ph.D. candidate at Dartmouth and first author of the paper. “We were able to identify conditions for isolating these halves from one another.”

Particles come in two different types: fermions and bosons. Fermions, such as electrons, tend to be solitary, avoiding one another at all costs. Bosons, such as photons, tend to bunch together. It was therefore a long-standing assumption that splitting bosons would be an insurmountable task.

“Our discovery provides the first hint that a previously unknown, topological phase of light and matter which hosts Majorana bosons may exist,” Flynn said. The theoretical advancement builds upon the prediction of neutral, electron-like particles known as Majorana fermions. In 2001, researchers suggested a specific process for how electrons could actually be halved in certain superconductors. But the photon remained indivisible.

According to the research team, Majorana bosons can be viewed as distant relatives to Majorana fermions.

“Fermions and bosons are as different as two things can be in physics,” said Emilio Cobanera, assistant professor of physics at SUNY Polytechnic Institute and co-author of the study. “In effect, the particles are distorted images of each other. The existence of the Majorana fermions was our main clue that the Majorana boson was hiding somewhere in the funhouse mirror.”

Confirmation of the Majorana boson would still require a laboratory experiment that observes the photon halves. Unlike the massive structures built to detect the Higgs boson, an experiment to detect photon halves could be done on a tabletop using existing or near-term technologies.

The team found that Majorana bosons are robust against experimental imperfections and identifiable by distinct signatures. While it’s difficult to predict how the findings may be applied, those characteristics could support the development of new types of quantum information processors, optical sensors, and light amplifiers. The research also points the way toward uncovering a new exotic phase of matter and light.

“In order to make this discovery, we had to challenge long-held beliefs and really think outside the box,” Viola said. “We have split something previously thought to be unsplittable, and we’ll never look at light the same way.”

The research was published in Physical Review Letters (www.doi.org/10.1103/PhysRevLett.127.245701).