Scientists at the University of Innsbruck under the leadership of Hanns-Christoph Nägerl have successfully observed anyons, exotic quasiparticles distinct from the well-known fermions and bosons, within a one-dimensional quantum system. The study was published in the journal Nature.
Researchers inject an impurity into a one-dimensional ultracold gas, thereby generating a quasiparticle with exotic properties. Image Credit: University of Innsbruck
Particles are fundamentally classified as either fermions or bosons. Fermions, such as quarks and electrons, are the building blocks of matter, while bosons, like photons (mediating electromagnetic forces) and gluons (governing nuclear forces), typically carry fundamental interactions.
A key distinction lies in their quantum behavior upon exchange: swapping two fermions results in a phase shift of pi in their quantum wave function (a mathematical minus sign), whereas bosons exhibit no such phase change (a phase of zero). This quantum statistical property profoundly influences the behavior of many-body quantum systems, explaining the structure of the periodic table and underlying the phenomenon of superconductivity.
However, in systems confined to low dimensions, an intriguing intermediate class of particles emerges: anyons. These are neither purely fermions nor bosons, exhibiting exchange phases between zero and pi. Unlike conventional particles, anyons are not fundamental entities but arise as emergent excitations within certain quantum states of matter, similar to how phonons (vibrations in a string) behave as "particles of sound." While anyons have been observed in two-dimensional systems, their existence in one-dimensional (1D) systems has remained unconfirmed until now.
The study reports the first experimental observation of emergent anyonic behavior in a 1D ultracold gas of bosons. This research is a collaborative effort involving Hanns-Christoph Nägerl's experimental group at the University of Innsbruck (Austria), theorist Mikhail Zvonarev at Université Paris-Saclay, and Nathan Goldman's theory group at Université Libre de Bruxelles (Belgium) & Collège de France (Paris).
The research team achieved this significant milestone by introducing and accelerating a mobile impurity within a strongly interacting bosonic gas and carefully analyzing its momentum distribution. The study demonstrates that the presence of the impurity facilitates the emergence of anyons within the one-dimensional system.
What's remarkable is that we can dial in the statistical phase continuously, allowing us to smoothly transition from bosonic to fermionic behavior. This represents a fundamental advance in our ability to engineer exotic quantum states.
Sudipta Dhar, Study Lead Author, University of Innsbruck
The theorist Botao Wang agrees, “Our modeling directly reflects this phase and allows us to capture the experimental results very well in our computer simulations.”
This remarkably straightforward experimental setup creates new opportunities to investigate anyons within precisely controlled quantum gases. Beyond fundamental scientific inquiry, these studies are particularly exciting due to predictions that specific types of anyons could enable topological quantum computing – a groundbreaking method that has the potential to overcome significant limitations of current quantum processors.
This discovery represents a crucial advancement in the exploration of quantum matter, providing new insights into the behavior of these exotic quasiparticles, which may play a significant role in the future of quantum technologies.
Journal Reference:
Dhar, S., et al. (2025) Observing anyonization of bosons in a quantum gas. Nature. doi.org/10.1038/s41586-025-09016-9