Harvard Physicists Create New Phase of Matter, Advance Field of Quantum Computing

A team of Harvard researchers working with the quantum computing company Quantinuum announced the creation of a new phase of matter in a research paper last month.

Harvard Physics professor Ashvin Vishwanath — along with Graduate School of Arts and Sciences alum Nathanan “Nat” Tantivasadakarn and physics postdoctoral fellow Ruben Verresen — detailed the creation of a new phase of matter called non-Abelian topological order in a paper in Nature.

Vishwanath said his team’s research brought together the traditionally disparate fields of condensed matter physics, information theory, and the physics of high energy particles.

“There’s been a very fruitful interaction between these three areas,” Vishwanath said in an interview with The Crimson.

Tantivasadarkarn added that a “huge area” of research in condensed matter physics centers around researchers trying to find candidates or materials suitable for performing quantum computation — which uses quantum mechanics to create computer hardware and algorithms that can solve problems classical computers cannot — but this has proved extremely difficult.

Instead of searching for the material, he said his team decided to make one using a trapped-ion quantum processor owned by Quantinuum.

Tantivasadarkarn described their research as the culmination of a series of papers exploring particles in condensed matter physics.

“There has been a lot of search in the condensed matter community looking for exotic materials which host some interesting particles called anyons,” Tantivasadarkarn said.

“In our universe, there are usually two types of particles,” he added: bosons, which include photons, and fermions, which include electrons and protons.

“The fermion has something called the Pauli exclusion principle,” Tantivasadarkarn said, which prevents two particles from occuping the same quantum state.

“People have actually proven that in three dimensional space, you can only have bosons and fermions. Those are the only two possibilities,” Tantivasadarkarn said. “But if you restrict yourself into a two dimensional plane, then people are showing that there are much more possibilities.”

Non-Abelian anyons, the type of quasi-particles Tantivasadarkarn’s research deals with, are only mathematically possible in a two-dimensional plane and can be used to store quantum information.

According to Vishwanath, 50 percent of the challenge in quantum computing is keeping memories in quantum computers from degrading due to the environment, while the other half of the challenge involves processing stored information.

“There seems to be one way to really get around it — to actually have your cake and eat it too, which is if you were to encode this memory in a non-Abelian quasi-particle, then it turns out that the memory is, at least in theory, very well protected, and you can act on it,” Vishwanath said.

“That’s sort of the holy grail in the field of quantum computing,” Vishwanath said.

—Staff writer Adina R. Lippman contributed reporting.

—Staff writer Angelina J. Parker can be reached at angelina.parker@thecrimson.com. Follow her on X @angelinajparker.