January 13, 2025
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Exotic “paraparticles” that defy classification may exist in many dimensions
Theoretical physicists predict the existence of exotic ‘paraparticles’ that defy classification and could have applications in quantum computing

Particles known as fermions (Shown in this figure) cannot share the same state.
Roman Andrade 3Dcienca/Science Photo Library
Theoretical physicists have proposed the existence of a new type of particle that does not fit into the traditional classification of fermions and bosons. Regarding those “paraparticles”, nature Although it is not the first to be proposed on January 8, the detailed mathematical model that characterizes it could lead to experiments created using quantum computers. This research also suggests that undiscovered elementary particles may exist in nature.
In another development result released at the end of last year, sciencePhysicists have experimentally demonstrated for the first time in a hypothetical one-dimensional universe another type of particle that is neither a boson nor a fermion: an anion. Anyons have previously only been created in 2D systems.
Due to their unusual behavior, both paraparticles and anyons may one day help reduce error rates in quantum computers.
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Particle properties
A century ago, when physicists were just beginning to understand the structure of atoms, the Austrian-born theorist Wolfgang Pauli proposed that two electrons cannot occupy the same state, and that when two electrons approach the same state, There will be a repulsive force between them. This “Pauli exclusion principle” is important for the way the electrons orbiting the nucleus are arranged in shells, rather than all falling into the lowest energy state.
Pauli and his colleagues soon realized that this empirical exclusion law applied not only to electrons but also to a wider class of particles, including protons and neutrons called fermions. Conversely, particles that prefer to share the same state (including, for example, photons in a laser beam) became known as bosons. (Pauli and his collaborators also discovered why being a fermion or a boson appears to be related to the particle’s intrinsic angular momentum, or “spin.”)
Mathematically speaking, the fundamental property of fermions is that when two of the fermions swap positions, the “wave function” representing their collective quantum state changes sign, or is multiplied by -1. That’s what it means. For bosons, the wave function does not change. Early quantum theorists knew that, in principle, there could be other kinds of particles whose wave functions change more complexly when they swap positions. In the 1970s, researchers discovered anyons that can only exist in a one- or two-dimensional universe.
Now Zhiyuan Wang, a physicist at the Max Planck Institute for Quantum Optics in Garching, Germany, and Kaden Hazzard of Rice University in Houston, Texas, have discovered that physicists can exist in any dimension and have the following properties: We have constructed a quasiparticle model. It is different from either fermions or bosons. In particular, these paraparticles are subject to a unique type of Pauli exclusion. “It’s not surprising at all that it’s possible,” says Kasia Rezner, a mathematical physicist at the University of York in the UK. “But it’s still cool.”
Wang said he came up with the exotic swapping rules by accident in 2021 while he was a doctoral student. “That was the most exciting moment of my life,” he says. Wang adds that realizing these quasiparticle states on a quantum computer should be difficult but possible.
1D someone
Paraparticles share properties with fermions. That is, if you swap two particles and then put them back together, they return to their original state. Anyon is generally not classified as a paraparticle because it has a different quantum state even after being restored to its original position.
in science According to the study, physicists Joyce Kwan and Marcus Greiner of Harvard University in Cambridge, Massachusetts, and their colleagues used light waves to suspend atoms of the isotope rubidium-87 in a vacuum. The atoms tended to stop in the troughs of the waves, only occasionally jumping from one atom to the next over distances of less than a micrometer. In this situation, rubidium-87 atoms typically behave like bosons, so it is okay for two of them to share the same valley. But by periodically tweaking the intensity of the light, researchers can change the behavior of the atoms so that when two atoms swap positions, their wavefunctions are twisted by a predetermined angle. Ta. This is a characteristic property of anyon. To study the wavefunction, Kwan said, researchers had to repeat the experiment many times by moving the atoms, then freezing them, and then imaging each atom’s position.
“We’re very excited that the Greiner group has brought everything one-dimensional to life,” said Martin Greiter, a theoretical physicist at Julius Maximilian University in Wurzburg, Germany.
Anyons wavefunctions can provide a robust way to encode information because they “remember” how two of them were exchanged. This property of memory is already being exploited in the virtual 2D Anyon, built by Google physicists and other teams.
Although paraparticles are unlikely to be as robust as other particles, they could also be useful in quantum computations, Wang said. Interestingly, they can exist in 3D. In principle, some undiscovered elementary particles could be paraparticles, he added.
This article is reprinted with permission. first published January 8, 2025.