Quantum quasiparticle could make future quantum computers more reliable

Supported by the U.S. National Science Foundation, physicists have revealed the presence of a previously unobserved type of subatomic phenomenon called a fractional exciton. Their findings confirm theoretical predictions of a quasiparticle with unique quantum properties that behaves as though it is made of equal fractions of opposite electric charges bound together by mutual attraction.

The discovery was supported by NSF through multiple grants and laboratory work performed at the NSF National High Magnetic Field Laboratory in Tallahassee, Florida. The results are published in Nature and show potential for developing new ways to improve how information is stored and manipulated at the quantum level, which could lead to faster and more reliable quantum computers.

"Our findings point toward an entirely new class of quantum particles that carry no overall charge but follow unique quantum statistics," says Jia Li, leader of the research team and associate professor of physics at Brown University. "The most exciting part is that this discovery unlocks a range of novel quantum phases of matter, presenting a new frontier for future research, deepening our understanding of fundamental physics and even opening up new possibilities in quantum computation."

Li and his team were able to observe fractional excitons by using a phenomenon known as the fractional quantum Hall effect, which occurs when a strong magnetic field is applied to layers of atomically thin materials at very low temperatures. Under these conditions, the electrons flowing through the layers behave as though they have broken up into fractions of a single electron, containing only a portion of a single electron's negative charge. Identical but opposite fractional amounts of positive charge, called "holes," were also observed in adjacent layers within the material. 

The researchers found that the attraction between the two oppositely charged fractional particles creates the predicted fractional exciton.

"We've essentially unlocked a new dimension for exploring and manipulating this phenomenon, and we're only beginning to scratch the surface," says Li. "This is the first time we've shown that these types of particles exist experimentally, and now we are delving deeper into what might come from them."

The team's next steps will involve studying how fractional excitons interact and whether their behavior can be controlled.