Quantum breakthrough: Non-Abelian anyons created for the first time

What if the world we live in was not three-dimensional but two-dimensional? How would the basic building blocks of matter behave in such a flat world? This question drives the research of Ashvin Vishwanath, a theoretical physicist at Harvard University.In our 3D world, there are only two types of particles: bosons and fermions. Bosons are the particles of light and force, such as the famous Higgs boson that gives mass to other particles. Fermions are matter particles, such as protons, neutrons, and electrons, that make up everything we see and touch.But in a 2D world, things get more interesting. Other types of particles can exist, which are neither bosons nor fermions but something in between. These particles are called non-Abelian anyons and have some very strange and fascinating properties.Quantum magic with Non-Abelian anyonsNon-Abelian anyons are not particles, but rather collective excitations of a special phase of matter, like ripples on the surface of water. They can only exist in a 2D plane, where they can move around each other in a way that is impossible in 3D.What makes non-Abelian anyons so special is that they have a kind of memory. When they swap places, they remember their previous positions and orientations, and this affects their future behavior. This is like a magic trick: the magician moves some cups around and reveals a hidden ball under one of them.This memory also makes non-Abelian anyons topological, meaning they are immune to small deformations and disturbances. They can be stretched, twisted, or bent but will not lose their identity or information.These properties make non-Abelian anyons very attractive for quantum computing, the next frontier of information technology. Quantum computing uses quantum bits, or qubits, which can store and process information in a much more powerful way than classical bits. However, qubits are fragile and prone to errors, limiting their practical use.On the other hand, non-Abelian anyons could be used as robust qubits, which can preserve and manipulate information without losing it to noise or interference. This could enable quantum computing to reach its full potential and solve impossible problems for classical computers.Creating and controlling non-Abelian wavefunctions.Nature Creating Non-Abelian anyons for the first timeNon-Abelian anyons have been predicted by theory for decades but have never been observed or created in the laboratory, until now.In collaboration with researchers at the quantum computing company Quantinuum, Vishwanath and his team have achieved a breakthrough in creating and controlling non-Abelian anyons for the first time. Their results are published in the journal Nature.The team used a powerful device called a quantum processor, a machine that can manipulate quantum states of matter. They started with a lattice of 27 trapped ions, atoms that have lost or gained an electron. They then used a clever technique of partial and targeted measurements to shape the system's quantum state until they obtained the desired state of non-Abelian topological order.The team demonstrated the synthesis and control of non-Abelian anyons and verified their properties and behavior. They also showed that their system could be scaled up to larger sizes, which is crucial for quantum computing applications.“This is a remarkable achievement in quantum physics and engineering,” Vishwanath said. “We have not only realized a new phase of matter, but also demonstrated its potential for quantum computing.”Vishwanath, a theorist by training, said he was thrilled to see his ideas come to life in the experiment. He also said he was excited to celebrate the 100th anniversary of quantum mechanics, the branch of physics that describes the nature of matter and energy at the smallest scales.“We are living in a golden age of quantum science and technology,” he said. “There is still so much to discover and explore.”Study abstract:Non-Abelian topological order is a coveted state of matter with remarkable properties, including quasiparticles that can remember the sequence in which they are exchanged. These anyonic excitations are promising building blocks of fault-tolerant quantum computers. However, despite extensive efforts, non-Abelian topological order and its excitations have remained elusive, unlike the simpler quasiparticles or defects in Abelian topological order. Here we present the realization of non-Abelian topological order in the wavefunction prepared in a quantum processor and demonstrate control of its anyons. Using an adaptive circuit on Quantinuum’s H2 trapped-ion quantum processor, we create the ground-state wavefunction of D4 topological order on a kagome lattice of 27 qubits, with fidelity per site exceeding 98.4 per cent. By creating and moving anyons along Borromean rings in spacetime, anyon interferometry detects an intrinsically non-Abelian braiding process. Furthermore, tunnelling non-Abelions around a torus creates all 22 ground states, as well as an excited state with a single anyon—a peculiar feature of non-Abelian topological order. This work illustrates the counterintuitive nature of non-Abelions and enables their study in quantum devices.