Insider Brief<\/p>\n
Researchers from the University of Chicago, Harvard, Stony Brook University and Quantinuum demonstrated the first universal gate set using non-Abelian anyons on quantum hardware, showing the approach can in principle perform any quantum computation. <\/p>\n
Using Quantinuum\u2019s 54-qubit trapped-ion processor, the team combined anyon braiding and fusion to implement the operations needed for universal quantum computing, overcoming limitations of earlier anyon-based demonstrations. <\/p>\n
The work also showed that non-Abelian anyons can directly prepare a quantum \u201cmagic state\u201d through topological operations, suggesting a potential path to fault-tolerant quantum computing with less reliance on resource-intensive magic state distillation.<\/p>\n
PRESS RELEASE \u2014 A truly useful quantum computer must be able to run any algorithm at all, with the same versatility an ordinary laptop offers. Physicists have now shown a new way to give a quantum computer exactly that flexibility, harnessing the capabilities of exotic quantum particles called non-Abelian anyons.\u00a0<\/p>\n
A team of scientists from the University of Chicago Pritzker School of Molecular Engineering (UChicago PME), Harvard, Stony Brook University, and Quantinuum, built and tested a complete toolkit of operations using non-Abelian anyons, proving for the first time the broad utility of this approach.\u00a0<\/p>\n
\u201cWe demonstrated a so-called universal gate set\u2014meaning that if you store information in these emergent versions of quarks, and you move them around, you can do any quantum computation you might want to do,\u201d said\u00a0Ruben Verresen,<\/a>\u00a0assistant professor of molecular engineering at UChicago PME and a co-author of the\u00a0new study published in\u00a0Nature<\/a>.\u00a0<\/p>\n The approach not only has the potential to lead to a general-purpose quantum computer, but also suggests a path to reliability. Quantum computers generally depend on error correction techniques, spreading data across many physical qubits to guard against mistakes. But these error-correcting codes typically do not, on their own, provide all the operations needed for universal quantum computing on the protected data. Instead, engineers use specially prepared \u201cmagic states\u201d that are built through a resource-intensive distillation process, consuming a large share of the qubits in a machine. The new work suggests that non-Abelian anyons can sidestep that process.\u00a0<\/p>\n \u201cNon-Abelian codes are a dark horse in the race to quantum error correction,\u201d said Henrik Dreyer, managing director and scientific lead at Quantinuum\u2019s Munich office and a co-author of the study. \u201cIn this work we show the first universal gate set in a non-Abelian code, which demonstrates that fault-tolerant computations can in principle be done without resorting to magic state distillation or cultivation, which are the most expensive operations in standard quantum error correction codes.\u201d<\/p>\n Where braiding anyons fell short<\/p>\n Ordinary qubits store information in a binary on-or-off state, or some in-between combination of the two. Non-Abelian anyons are different. They don\u2019t exist as standalone particles in nature; researchers create them with quantum circuits that link many ordinary qubits into one large, entangled state that behaves like an entirely new kind of particle, with its own internal rules.<\/p>\n \u201cThe way I think about these codes is they\u2019re creating little universes\u2014alternative universes, but ones that reflect some of the properties of our own,\u201d Verresen said.<\/p>\n Non-Abelian anyons each carry an internal state that changes whenever two anyons are moved, or braided, around each other. The order you braid them in matters (that\u2019s what non-Abelian means), giving them the potential to encode quantum information in ways ordinary particles can\u2019t. Because their state is spread across many entangled qubits rather than sitting in any one place, these anyons are unusually well protected from the small disturbances that trip up ordinary qubits. In addition, their braiding can double as a computational gate.<\/p>\n In 2024, a team that included Verresen used a Quantinuum trapped-ion computer to create anyons based on a symmetry group called D4 \u2014 the rotations and reflections that leave a square unchanged \u2014 marking the first demonstration of this kind of non-Abelian order on quantum hardware. But braiding those anyons alone didn\u2019t allow every operation a computer needs.\u00a0<\/p>\n \u201cIn that work, we didn\u2019t demonstrate that those emergent forces were enough to do quantum computation,\u201d said Verresen. \u201cThat particular universe we created was not powerful enough.\u201d<\/p>\n Fusion makes the difference<\/p>\n In the new paper, the team turned to a different type of symmetry called S3\u2014the rotations and mirror-image flips that leave an equilateral triangle unchanged\u2014and built its anyons on Quantinuum\u2019s H2 trapped-ion processor, entangling 54 qubits. Unlike D4, S3\u2019s structure had the right properties for universal computation, but only if braiding was also paired with a second tool: fusion, where two anyons are merged together and the outcome read out as a measurement. The idea had been proposed theoretically in 2003 by Carlos Mochon, then a student of John Preskill at Caltech. However, turning that abstract proposal into a concrete protocol for quantum hardware required substantial further theoretical and experimental work.<\/p>\n The team used pairs of these anyons to encode \u201ctopological qutrits\u201d which have three levels of quantum information compared with the two levels encoded by standard qubits. By braiding and fusing these qutrits in different combinations, the researchers demonstrated three operations \u2014 one entangling gate from braiding, and two distinct types of measurement from fusion \u2014 that, combined, can in principle reach any quantum operation, including ones that weren\u2019t accessible through braiding alone. In addition to their potential applications, the new states can shed light on basic properties of physics.\u00a0<\/p>\n \u201cIt is gratifying to see ideas we have spent our PhD work thinking about realized in the lab, and it has been made possible by remarkable advances in quantum hardware over the past few years,\u201d said Anasuya Lyons and Chiu Fan Bowen Lo, graduate students at Harvard University in the group of Ashvin Vishwanath who helped lead the work.<\/p>\n Moving toward error correction<\/p>\n The team also showed that the non-Abelian anyons could be used to prepare a magic state directly, through topological operations \u2014 sidestepping the costly distillation process used in most quantum systems.<\/p>\n However, in the current paper, Verresen and colleagues didn\u2019t carry out active error correction. Instead, they tested individual computational building blocks to show they work and verified that they had created a magic state that matched theoretical predictions.\u00a0<\/p>\n \u201cSo far, we\u2019ve ignored the question of error correction. Here, it\u2019s more like a proof of principle,\u201d Verresen said.\u00a0<\/p>\n Combining this approach with error correction is the natural next step, he added \u2014 one that could eventually make non-Abelian anyons a practical foundation for large-scale, fault-tolerant quantum computers. Verresen is already collaborating with other PME researchers to develop new ways of stabilizing non-Abelian quantum memories.\u00a0<\/p>\n