The quantum Hall effect arises when a two-dimensional electron gas, typically formed at the interface of a semiconductor heterostructure, is cooled to cryogenic temperatures and subjected to a strong perpendicular magnetic field. Under these conditions the electronic spectrum collapses into highly degenerate Landau levels, and the Hall conductance becomes quantized. At fractional filling factors, interactions among electrons dominate and produce the fractional quantum Hall regime, in which the fundamental excitations carry fractions of the elementary charge, such as e/3 or e/5. Detecting these fractional charges directly has long been a challenge, because conventional electrometers and charge sensors are designed around ordinary electrons and often lack the sensitivity, bandwidth, or back-action characteristics needed for quasiparticle experiments.

The new device takes the form of an antidot: a small hole etched into the two-dimensional electron gas that acts as an artificial impurity in the surrounding quantum Hall fluid. Instead of passing straight through the sample, the quantized Hall current must circulate around the antidot along narrow edge channels. Crucially, the antidot region itself can trap a small, countable number of quasiparticles. Each time a quasiparticle tunnels onto or off the antidot island, the electrostatic potential of the island shifts, and this shift modulates the tunneling of quasiparticles around the perimeter. The result is a characteristic periodic oscillation in the measured conductance, with a period set by the ratio of the applied voltage to the quasiparticle charge. By reading out these oscillations, the researchers can convert voltage changes into charge changes—performing the function of a coulombmeter, but one calibrated in fractional units of e.

In their measurements, the team fabricated the antidot in a high-mobility gallium arsenide–based two-dimensional electron gas and tuned the filling factor of the surrounding fluid into a fractional quantum Hall state. By driving a radio-frequency excitation and monitoring the reflected signal, they performed a form of radio-frequency reflectometry, a technique borrowed from quantum-dot charge sensing that allows charge changes to be detected with microsecond-scale temporal resolution and exquisite charge sensitivity. The periodic conductance oscillations they observed directly reflected the accumulation of quasiparticles of definite fractional charge on the antidot, confirming that the device operates as a genuine fractional coulombmeter rather than merely as a sensitive conventional electrometer.

A key advantage of the antidot architecture is its versatility. The device can be operated in several distinct regimes simply by adjusting gate voltages and the magnetic field. In one regime it behaves as a precise charge meter, resolving individual tunneling events of fractionally charged quasiparticles. In another, it can act as a tunable source and detector of quasiparticles, injecting them into edge channels at controllable rates. This dual functionality is significant for the growing experimental program aimed at anyon interferometry, in which quasiparticles are made to travel around closed loops and acquire statistical phases that reveal their exotic quantum statistics. A device that both generates and senses single fractional quasiparticles greatly simplifies such experiments, which traditionally require multiple separately calibrated components.

The researchers also characterized the device’s sensitivity and back-action in detail. Charge sensitivity reached levels comparable to the best radio-frequency single-electron transistors and quantum-point-contact charge sensors, but with the crucial difference that the detected object carries a fraction of the electron charge. This means the effective resolving power with respect to quasiparticles is even more impressive, since the signal per tunneling event is proportionally smaller. Moreover, the coupling between the antidot and the surrounding edge channels can be tuned, allowing the experimenters to balance measurement strength against the disturbance introduced into the quantum Hall fluid—a critical consideration when the goal is to observe delicate interference phenomena or to preserve fragile quasiparticle states over extended periods.

Beyond its immediate utility for fundamental physics, the fractional coulombmeter addresses a pressing need in the emerging field of topological quantum computation. Certain fractional quantum Hall states, most famously the so-called 5/2 state, are predicted to host non-Abelian anyons—quasiparticles whose braiding operations act on a degenerate quantum state space and could therefore encode quantum information in a form intrinsically protected from local noise. Reading out the outcome of a braid operation typically amounts to detecting a change in quasiparticle number or charge on a localized island. An antidot-based fractional coulombmeter provides exactly this capability, offering a path toward the single-shot, high-fidelity readout that any practical topological qubit architecture will demand.

The work also refines our understanding of antidot physics itself. Decades of study have revealed that antidots host a rich variety of phenomena, including Coulomb-blockade-like charge quantization, resonant tunneling through localized states, and complex dynamics of quasiparticle exchange with the edge. By operating the antidot explicitly as a metrological device, the team has turned what was previously a source of experimental complications into a resource. The periodic charge oscillations serve as an in situ calibration of the quasiparticle charge, and the device could even be used to compare effective charges in different fractional states, testing theoretical predictions about the internal structure of the quantum Hall fluid and the nature of its quasiparticle excitations.

The demonstration is likely to stimulate a wave of follow-up experiments across several laboratories worldwide. Natural next steps include integrating the fractional coulombmeter with interferometric structures to perform single-quasiparticle statistics measurements, extending the technique to fractional states with even smaller quasiparticle charges, and translating the platform into materials such as graphene, where exceptionally clean fractional quantum Hall states—including even-denominator states—are now routinely observed. There are also longer-term ambitions: coupling the antidot detector to microwave resonators to reach quantum-limited sensing, and using arrays of antidots to build quasiparticle-based circuits that manipulate fractional charges with the same control that conventional electronics exercises over electrons.

What makes the result especially compelling is its conceptual simplicity. The coulombmeter, one of the oldest instruments in physics, has been reborn in a regime its inventors could scarcely have imagined: a device that measures charge in thirds and fifths of an electron, etched into a frozen quantum fluid and read out through the quantum interference of quasiparticles. As experiments on anyons and topological matter move from proof-of-principle demonstrations toward genuine quantum technologies, tools of this kind—sensitive, tunable, and natively fluent in the language of fractional charge—are likely to become as fundamental to quasiparticle physics as the electrometer once was to the study of the electron itself.

The work brings together teams from the University of Chicago Pritzker School of Molecular Engineering, Harvard, Stony Brook University, and Quantinuum. Using non-Abelian anyons encoded across multiple qubits, the researchers show that by moving (braiding) these excitations in carefully chosen patterns—and combining that with additional operations—they can implement the full range of gates needed for arbitrary quantum algorithms.

“We demonstrated a universal gate set,” said Ruben Verresen of UChicago PME, explaining that storing information in these emergent quark-like degrees of freedom and then manipulating them enables essentially any quantum computation. The goal is not just proof that quantum effects can be controlled, but that the control is broad enough to scale into general-purpose computing.

A central motivation is fault tolerance. Conventional quantum error correction protects qubits by spreading information across many physical qubits, but universal gate sets usually require resource-heavy “magic states.” Building those states typically involves distillation procedures that consume significant machine time and qubits—one of the biggest practical costs in leading architectures.

Non-Abelian anyons are naturally attractive because their information is distributed across entangled degrees of freedom, making them comparatively resilient to local noise. Just as importantly, their braiding can function as computation. Yet prior demonstrations using the D4 symmetry group—based on rotations and reflections of a square—showed that braiding alone was not enough to reach full universality.

The new study targets a different symmetry, S3, associated with rotations and mirror flips of an equilateral triangle. On Quantinuum’s H2 trapped-ion processor, the team entangled 54 qubits to realize S3-based anyons. Crucially, the researchers show that universality emerges only when braiding is paired with fusion, a measurement-like operation where two anyons are merged and the outcome is read out.

To benchmark the approach, the team encoded information in “topological qutrits,” which use three quantum levels rather than the two levels of ordinary qubits. Braiding produced an entangling operation, while fusion generated distinct measurement operations; together, these components can in principle synthesize any quantum transformation, including gates unreachable by braiding alone. The protocol also enables preparation of a magic state directly via topological operations, potentially avoiding expensive distillation.

In the current results, the researchers did not perform active error correction. Instead, they verified key building blocks and confirmed that a magic state produced through anyon-based procedures matches theoretical expectations. “So far, we’ve ignored the question of error correction,” Verresen said—framing the work as a proof of principle.

The next step is to integrate this anyon-based approach with error correction to move from demonstrated primitives to scalable, fault-tolerant computation. Verresen and collaborators are already exploring methods to stabilize non-Abelian quantum memories, aiming to make this “dark horse” architecture practical for large-scale quantum machines.

Subject of Research: Universal quantum computation with non-Abelian anyons (braiding and fusion) and implications for fault-tolerant quantum error correction
Article Title: Universal gates from braiding and fusing anyons on quantum hardware
News Publication Date: 15-Jul-2026
Web References: https://www.nature.com/articles/s41586-026-10709-y
References: Lo et al., Nature (July 15, 2026). DOI: 10.1038/s41586-026-10709-y
Image Credits:
Keywords: quantum computing; non-Abelian anyons; topological qutrits; universal gate set; quantum error correction; braiding and fusion; trapped-ion processor

Topological quantum computation offers a different vision: implement logic by braiding non-Abelian anyons, whose exchanges enact transformations on a degenerate Hilbert space. Yet for the simplest non-Abelian extensions of the toric code, braiding alone has long been known to be insufficient for universal quantum computation. The missing ingredient is not more braiding, but an additional primitive that leverages the internal structure of anyons—namely, fusion.

In a new hardware demonstration, researchers show that anyon fusion, when combined with braiding, can supply the missing universality. Working with a quantum double model based on the smallest non-Abelian group, (S_3), they focus on encoding information in the global fusion space of non-Abelian anyons. Instead of relying solely on exchange operations, they treat fusion as an active computational step, enabling a richer set of logical transformations.

The team prepares a 54-qubit ground state of the (S_3) quantum double on Quantinuum’s H2 processor. This matters because creating a specific topological phase is not just a theoretical construction—it requires carefully engineering the many-body constraints that define the fusion rules and anyonic structure. Their experiment operationalizes those constraints so that logical degrees of freedom live in the anyon fusion space.

By integrating braiding with fusion operations, the researchers implement a universal topological gate set. They also perform read-out in the same topological framework, ensuring that measurement respects the global nature of the encoded information. Crucially, they validate the computational power by topologically preparing a magic state, an essential resource for achieving universal quantum computation under fault-tolerant schemes.

Taken together, the work argues that minimally non-Abelian topological states can be both scalably preparable and computationally powerful—if fusion is used as a primitive rather than treated as a passive property. That shift reframes what is required for universality: not just non-Abelian statistics, but the ability to control how anyons combine.

Beyond this specific model, the results suggest broader pathways for harnessing the intrinsic properties of quantum matter. If fusion-controlled universality can be extended to other quantum double phases and hardware platforms, topological codes may become not only robust memories but practical computational substrates. For viral science news, the headline is simple: the path to universal, fault-tolerant quantum computing just gained a crucial new lever—anyon fusion on real hardware.

Subject of Research: Topological quantum computation using non-Abelian anyons; universality via braiding and fusion
Article Title: Universal gates from braiding and fusing anyons on quantum hardware
Article References: Lo, C.F.B., Lyons, A., Gresh, D. et al. Universal gates from braiding and fusing anyons on quantum hardware. Nature 655, 591–597 (2026). https://doi.org/10.1038/s41586-026-10709-y
Image Credits: AI Generated
DOI: 10.1038/s41586-026-10709-y
Keywords: topological quantum computation; non-Abelian anyons; fusion and braiding; quantum double; (S_3); magic state; fault tolerance

Majorana zero modes are theoretical quasiparticles predicted to emerge at the edges of topological superconductors. They are particularly noteworthy because of their anticipated non-Abelian exchange statistics, which are a cornerstone for the realization of topological quantum computation. This makes topological superconductors a compelling candidate in the quest for decoherence-free quantum computing, which aims to facilitate stable and high-fidelity quantum gates essential for future quantum computers.

The Kitaev model plays a pivotal role in the understanding of one-dimensional topological superconductors. It introduces a chain of spinless fermions that are coupled through p-wave superconductivity and electron hopping. The transition to a topological state becomes possible with the presence of longer chains. Researchers focused on enhancing the scope of their work by realizing a three-site Kitaev chain that not only supports MZMs but also demonstrates increased stability compared to previous two-site configurations.

The construction of this three-site Kitaev chain is part of a broader effort to explore the applications of topological superconductivity. Over the past decade, multiple experimental platforms have emerged as possible candidates for this field. A minimal Kitaev chain, which was previously established by QuTech, consisted of two quantum dots linked through superconducting pairing. Although this two-site chain did support MZMs, their low stability became a point of concern, leading researchers to refer to them as “poor man’s MZMs.” The transition to three sites aims to mitigate the impact of local noise and chemical potential variations that have plagued earlier models.

Notable contributions to this research initiative came from various experts within QuTech, including Leo Kouwenhoven and Grzegorz Mazur, as well as first authors Alberto Bordin and Chun-Xiao Liu. They collaborated closely with Erik Bakkers’ team at the Technical University of Eindhoven to develop the three-site Kitaev chain, which consists of three semiconducting quantum dots connected by superconducting segments. The team’s efforts were focused on enhancing the stability of Majorana zero modes by optimizing the configuration of the quantum dots and superconducting materials.

The findings indicate that as the Kitaev chain lengthens from two to three sites, MZMs show increased stability in the new configuration. This observation provides a hopeful outlook for scaling the device further, allowing for the potential creation of longer chains that maintain robustness against perturbations. The researchers are optimistic about the implications of their findings regarding the scalability of Kitaev chains, which could significantly enhance the prospects for stable Majorana zero modes in quantum computing applications.

Mazur expressed the excitement of the team regarding their findings, noting the clear advancement from two-site to three-site chains. The improved stability of Majorana zero modes in these extended configurations not only opens doors for theoretical applications but also holds promise for technological advancements in quantum computing. Moving forward, the research team aims to expand the Kitaev chains even further, potentially incorporating five or six sites, and explore their implications for next-generation quantum technologies.

As part of an ongoing research endeavor at QuTech, the goal encompasses not just the creation of functional devices but also understanding and demonstrating how these Kitaev chains can serve as qubit candidates in quantum information experiments. The researchers are particularly keen to study how the lengths of the Kitaev chains influence qubit lifetimes. Responses to electrical noise are foundational in this discussion since two-site chains have displayed concerning levels of instability, while the stabilized three-site chains seem to pave the way for more reliable quantum operations.

Lengthening the Kitaev chain configuration presents unique research opportunities, especially as the quest for topological protection unfolds. Bordin mentioned the potential use of machine learning techniques to assist in fine-tuning these chains towards achieving topological protection. The research team is strategically laying the groundwork that could lead to the first practical quantum computing techniques, illustrating the slow yet steady progress toward more advanced quantum architectures.

In addition to understanding the electrical characteristics and behavior of these new chains, the QuTech researchers are planning to conduct quantum information experiments to explore the performance of these Kitaev chains under various scenarios. The team is eager to gain insights into how factors such as noise and operational conditions might impact qubit performance and to ascertain whether these chains can be reliably utilized as qubits in complex quantum systems.

As they continue their progress, Kouwenhoven and his colleagues have plans to investigate additional configurations, potentially coupling the three-site Kitaev chains with further quantum dots to elevate their functional capabilities. Their ongoing research reflects a robust commitment to advancing the understanding of topological superconductors and their real-world applications in quantum technology.

Through these explorations, the research team envisions a future where scalable topological qubits could revolutionize quantum computing methodologies, achieving the long-desired goal of fault-tolerant quantum computation. Their work thus represents a critical step forward in harnessing the power of quantum mechanics to potentially transform how computations are carried out on a fundamental level.

Coupling these findings with upcoming research could inspire novel experimental designs, ultimately propelling the field of quantum computing into new realms of stability and scalability. As the scientific community closely watches these developments, the implications of such breakthroughs may redefine the landscape of quantum technologies in the years to come.

Subject of Research: Three-site Kitaev chain using semiconducting quantum dots and superconducting segments.
Article Title: Enhancing Majorana stability with a three-site Kitaev chain
News Publication Date: 31-Mar-2025
Web References: Nature Nanotechnology
References: DOI: 10.1038/s41565-025-01894-4
Image Credits: QuTech
Keywords: Quantum computing, Kitaev chain, Majorana zero modes, Topological superconductors, Quantum dots.