At the heart of quantum computing lies the quest for materials that can sustain and manipulate exotic quantum states. The so-called Kitaev materials, known for potentially hosting quantum spin liquids, are key in this pursuit. Spin liquids represent a remarkable state of matter where spin orientations fluctuate perpetually, defying the classical magnetic order even at temperatures near absolute zero. Materials with honeycomb-structured lattices are particularly promising in stabilizing these elusive states due to the intense and competing magnetic interactions between neighboring ions.

Until now, research into such phenomena has predominantly focused on metals with heavy atomic weights and strong spin-orbit coupling, such as ruthenium and iridium. These elements, however, are scarce and expensive, making the scale-up of quantum technologies economically challenging. The Osaka team, led by principal investigator Hidekazu Tanaka and lead author Hao-Bo Li, questioned whether cobalt — an element widely used and far less rare — could replicate or even surpass such behaviors when appropriately configured.

To test this, the researchers introduced approximately 4% cobalt into NaSbO₃, a compound that inherently exhibits a layered honeycomb crystal arrangement. Utilizing advanced microscopy techniques, they confirmed that cobalt atoms naturally coalesced into local CoO₆ edge-sharing motifs, forming stable honeycomb substructures within the larger matrix. This spontaneous formation is significant as it circumvents the need for complex synthesis protocols, suggesting potential scalability and reproducibility in material fabrication.

Extensive magnetic characterization experiments revealed a striking ferromagnetic-like ordering emerging at around 88 Kelvin. Such magnetism is both unexpected and exciting because it originates from the local arrangement of cobalt ions within the honeycomb lattice, offering a physical platform that aligns remarkably well with theoretical predictions for these systems. Intriguingly, the cobalt honeycombs exhibited antiferromagnetic interlayer coupling, indicating a delicate balance of magnetic interactions that might be harnessed for manipulating quantum states.

The implications of this discovery extend beyond mere material novelty. Cobalt’s attributes — its relative abundance, compatibility with existing semiconductor manufacturing, and cost efficiency — render it an exceptionally attractive candidate for quantum device engineering. This breakthrough could therefore alleviate some of the prominent bottlenecks stalling the transition from laboratory demonstrations to commercial quantum technologies.

Furthermore, the exploration of Co-doped NaSbO₃ thin films fosters a deeper understanding of spin liquid physics and Kitaev interactions in more accessible compounds. If these materials can be refined to exhibit robust and controllable quantum spin liquid behavior, they might become integral components in future quantum computing architectures, where coherence and error correction are paramount.

The research team is not resting on this breakthrough. Their next steps involve meticulous fine-tuning of the cobalt doping concentrations and layering parameters to optimize magnetic interactions. Additionally, they plan to probe the quantum mechanical properties of these structures, such as spin excitations and topological characteristics, through sophisticated spectroscopic and transport measurements.

This pioneering work also hints at broader possibilities in condensed matter physics and material science. By combining readily available elements into complex lattice topologies, scientists may unveil a new class of quantum materials that balance theoretical intrigue with practical viability. The Osaka group’s success underscores how material innovation remains a cornerstone of technological advancement in the quantum era.

In summary, the identification of ferromagnetic-like behavior driven by local cobalt-based honeycomb motifs within NaSbO₃ matrices heralds a promising leap towards scalable and economically viable quantum materials. As quantum computing endeavors intensify globally, such developments could play a critical role in realizing the next generation of quantum technologies, expanding access from elite laboratories to widespread industrial applications.

Subject of Research: Quantum magnetic materials and ferromagnetic behavior in cobalt-doped NaSbO₃ thin films.

Article Title: Ferromagnetic-like behavior emerging from local CoO₆ honeycomb motifs in Co-doped NaSbO₃ thin films.

News Publication Date: 22-May-2026.

Web References: http://dx.doi.org/10.1103/54cx-6r5s

References: Li, H.-B., Tanaka, H., et al. Ferromagnetic-like behavior emerging from local CoO₆ honeycomb motifs in Co-doped NaSbO₃ thin films. Physical Review Materials, 10, 054418 (2026). https://doi.org/10.1103/54cx-6r5s

Image Credits: Reprinted with permission from H.-B. Li, et al. Ferromagnetic-like behavior emerging from local CoO6 honeycomb motifs in Co-doped NaSbO3 thin films. Phys. Rev. M 10, 054418 (2026). © 2026 American Physical Society.

Keywords

Quantum computing, honeycomb lattice, cobalt doping, sodium antimonate, ferromagnetic behavior, spin liquids, Kitaev materials, thin films, quantum magnetism, condensed matter physics, scalable quantum materials, semiconductor-compatible materials.

The structural complexity of the QARPET chip, viewed under a scanning electron microscope, resembles an intricate woven fabric. This unique form results from an extraordinary engineering challenge: interlacing a dense network of crossing electrodes at the nanoscale. The fabrication process pushed the boundaries of nanotechnology, demanding extreme precision and durability. Alberto Tosato, the lead engineer behind the layout designs, candidly admits the initial skepticism about the device’s viability, given its intricate electrode meshwork. Yet, the successful operation of the chip at millikelvin temperatures validated this ambitious approach, marking a milestone in quantum device fabrication.

The fundamental issue QARPET addresses is the efficient benchmarking of qubit arrays, a challenge that looms large as quantum processors edge towards integrating thousands or even millions of qubits. Conventional approaches, which involve testing individual qubits or small arrays, are extraordinarily time-consuming and resource-intensive, impeding rapid iteration and optimization. Lead researcher Giordano Scappucci emphasizes that scaling up quantum processors requires a statistical understanding of qubit uniformity, noise characteristics, and device variability—a task that QARPET is uniquely equipped to perform.

QARPET’s design revolves around a tiled architecture, where the chip is partitioned into numerous identical ‘tiles.’ Each tile encompasses two spin qubits coupled with a charge sensor, forming a miniature, self-sufficient quantum unit. This modular approach simplifies testing since identical tiles can be interrogated independently while sharing control infrastructure. Such an elegant method contrasts sharply with monolithic chip designs where adding qubits exponentially increases wiring complexity, often becoming a bottleneck for scalability.

At the heart of QARPET lies a crossbar layout for control lines, reminiscent of classical computer memory architectures. Rows and columns intersect, with shared control lines selecting individual tiles for measurement. This crossbar method drastically curtails the number of control wires that must penetrate the cryogenic environment, a key technical limitation in current quantum hardware. The scaling advantage is clear: while the array size increases quadratically, the number of control lines scales only linearly, making the architecture remarkably efficient for large-scale implementations.

The first chip prototype leverages a germanium/silicon-germanium (Ge/SiGe) heterostructure, a semiconductor material system prized for its high mobility and compatibility with existing fabrication techniques. This chip contains a 23-by-23 grid of tiles, allowing for up to 1,058 hole-spin qubits to coexist within a mere square millimeter. Scappucci highlights this density as a remarkable demonstration of the compactness achievable with semiconductor spin qubits, noting that the current infrastructure potentially enables probing over a thousand qubits in a single cooldown cycle—an operational breakthrough against the constraints of cryogenic testing.

High-frequency electrical readout techniques form the experimental backbone for QARPET’s qubit characterization. The team successfully demonstrated independent addressability and tuning of nearly all tested tiles within a subset of 40 units on the chip. Such comprehensive measurements allow extraction of critical device parameters, including threshold voltages, noise spectra, and variances in quantum dot formation. This granular insight into device performance variability is crucial for refining fabrication processes and enhancing qubit consistency across large arrays.

Beyond measurement capabilities alone, the researchers presented evidence that the architecture does not impair the spin qubits’ fundamental properties—a key proof of principle. Ensuring that the crossbar design and tiling do not degrade coherence times or increase noise is essential for any quantum computing platform aspiring to practical application. The results affirm that QARPET can serve not only as a testing tool but also as a scalable blueprint for future quantum processor designs.

The statistical richness afforded by QARPET’s architecture opens new avenues for optimizing quantum device reliability and reproducibility. As quantum technologies inch closer to commercialization, understanding subtle device-to-device variations will be indispensable. QARPET’s ability to collect large-scale statistical data under operational conditions offers a pathway to address these challenges, facilitating machine learning-assisted calibration and automated tuning strategies that could further streamline quantum hardware development.

One of QARPET’s noteworthy advantages is its compatibility with established semiconductor fabrication processes. This modularity suggests that the platform is adaptable to other material systems beyond Ge/SiGe, including mainstream silicon-based qubits. Such cross-compatibility could accelerate technology transfer from research prototypes to commercially viable quantum processors, leveraging decades of accumulated semiconductor industry expertise.

The potential for integrating QARPET with automated and machine learning algorithms heralds a new paradigm in quantum device optimization. By harnessing vast datasets from hundreds of qubits measured simultaneously under identical conditions, researchers can train AI systems to identify performance outliers, predict device degradation, and optimize gate control parameters—all contributing to enhanced scalability and quantum error mitigation.

In summary, the QARPET platform emerges as a transformative development in quantum hardware engineering. Combining a scalable crossbar architecture with high-density qubit tiling, it sets a new standard for integrated quantum testing. The ability to map out nuanced variations across large qubit arrays, coupled with demonstrated operational viability at cryogenic temperatures, indicates that QARPET is poised to accelerate the transition from small-scale laboratory experiments to industrial quantum computing systems.

The milestone demonstrated by QARPET unmistakably signals that fully integrated, large qubit arrays are within technological reach, bringing the vision of practical quantum processors into sharper focus. With this achievement, QuTech reinforces the promise that semiconductor spin qubits can deliver high density, scalability, and compatibility with mature industrial processes—critical factors for the next quantum computing revolution.

Subject of Research: Not applicable

Article Title: A crossbar chip for benchmarking semiconductor spin qubits

News Publication Date: 12-Feb-2026

Web References: 10.1038/s41928-026-01569-5

Image Credits: Tosato & Scappucci – QuTech – Delft University of Technology

Keywords: Quantum computing, Qubits, Quantum processors, Circuit design, Semiconductors, Quantum measurement

Unlike prior studies where charge noise was identified as the dominant factor limiting qubit coherence and operation fidelity, this new work highlights a different pathway to performance enhancement. Here, noise stemming from nuclear spins within the silicon lattice assumes a critical role. By employing isotopically enriched silicon with a reduced content of the nuclear spin-active isotope ^29Si, the team managed to achieve qubit fidelities exceeding 99%. This level of isotopic purity, currently at 400 ppm of ^29Si in their devices, paves the way for further improvements, given that academic prototypes have already demonstrated enrichment to below 50 ppm. This significant reduction in nuclear spin noise correlates with extended coherence times and improved qubit stability, a vital condition for practical quantum computation.

The industrial realization of such qubit devices required meticulous engineering, combining precise device fabrication with sophisticated calibration protocols. The researchers report that while the current calibration and tuning procedures remain labor-intensive and manually driven, these are essential to reach the demonstrated exceptional qubit control. The development of automated methods for calibration and characterization at scale remains a crucial future step. Once mature, these methodologies will enable mass calibration campaigns necessary for deploying large arrays of spin qubits efficiently and reproducibly, a fundamental requirement for building fault-tolerant quantum processors.

A notable aspect of this study is the comprehensive noise analysis that establishes a strategic framework to address qubit fidelity constraints. While the present qubit performance already surpasses many previously reported results, the team emphasizes reducing overhead for fault-tolerant quantum computing by targeting fidelities above 99.9%. Achieving such ultra-high fidelities across all quantum operations will dramatically ease the resource requirements for quantum error correction, thus bringing scalable and practical quantum architectures closer to reality.

The integration of spin qubits within a silicon–metal–oxide–semiconductor (SiMOS) platform furnishes unique advantages, primarily leveraging decades of industrial-scale CMOS (complementary metal-oxide semiconductor) technology. Nonetheless, fabricating devices with extremely small gate pitches and interfaces exhibiting minimal charge noise has historically presented formidable challenges. By overcoming these technical barriers, the researchers have successfully produced silicon spin-qubit unit cells adhering to industrial fabrication standards, potentially enabling seamless integration of quantum circuits onto conventional semiconductor chips.

Looking toward future scalability, the team underscores the importance of studying qubit behaviors under operational conditions that reflect large-scale systems more accurately. These include the application of global microwave control fields, which simplify control architecture across extensive qubit arrays, and operation at elevated temperatures that accommodate the heat dissipation of co-integrated control electronics, such as CMOS control chips operating at millikelvin regimes. Addressing these factors is critical to designing quantum processors that balance performance, control complexity, and manufacturability.

Beyond the immediate performance metrics, this research lays foundational work for designing quantum error correction strategies uniquely suited to spin qubit technology. Tailoring error correction codes to the specific noise profiles and error rates of silicon spin qubits will optimize fault tolerance, advancing the practical realization of quantum advantage. Still, these error correction schemes require comprehensive characterization of qubit operation fidelity in increasingly complex environments and device architectures.

The consistent demonstration of high-quality qubit operation, achieved through advanced fabrication under 300-mm foundry conditions, marks a proof of principle with substantial implications for industrial quantum technology development. It signals a transition from isolated laboratory demonstrations toward the integration of quantum devices within existing semiconductor industry infrastructures. This fusion holds promise for accelerating the timeline toward commercial quantum computers built upon the silicon spin-qubit platform.

Moreover, the study highlights the critical role of collaborative efforts between academia and industry. The convergence of industrial-scale fabrication processes with scientific insights into qubit physics and control methodology embodies a multidisciplinary approach essential for overcoming current technical and practical challenges. Such partnerships will be vital for pushing the boundaries of quantum processor performance while maintaining scalability and cost-effectiveness.

In synthesizing the achievements and future outlook, the researchers advocate for continued refinement of both materials and control techniques. The route toward fault-tolerant quantum computing will demand not only ultra-pure silicon and optimized device geometries but also enhanced understanding of electron quantum behavior in complex semiconductor environments. Advanced modeling and real-time measurement capabilities during fabrication will underpin these developments, creating feedback loops that improve device quality and uniformity.

Ultimately, these results present a compelling narrative: the progression of silicon spin qubits from an experimental curiosity to a viable industrial quantum technology is underway. The convergence of high-fidelity quantum control, industrial fabrication compatibility, and scalable architectures augurs a new era in quantum hardware research and development. This trajectory promises to transform quantum computation from a theoretical framework into a pervasive technological platform that harnesses the immense processing power intrinsic to quantum mechanics.

Subject of Research: Silicon spin qubits fabricated in 300-mm industrial semiconductor processes demonstrating high-fidelity quantum control and prospects for scalable quantum computing.

Article Title: Industry-compatible silicon spin-qubit unit cells exceeding 99% fidelity.

Article References:
Steinacker, P., Dumoulin Stuyck, N., Lim, W.H. et al. Industry-compatible silicon spin-qubit unit cells exceeding 99% fidelity. Nature (2025). https://doi.org/10.1038/s41586-025-09531-9

Image Credits: AI Generated

Traditionally, the state of the electron spin in NV centres is interrogated optically. When illuminated with green laser light, NV centers fluoresce, emitting photons whose properties correlate with the underlying spin configuration. Detecting these spin-dependent photons, however, is notoriously difficult. The inherently weak single-photon emission from a single NV centre demands sophisticated optical setups and ultra-sensitive detectors. Such arrangements are not only bulky but also sensitive to environmental noise and challenging to miniaturize. For quantum technologies to transcend laboratory demonstrations and find real-world applications, alternative readout methods that bypass these constraints are desperately needed.

The innovative approach developed by the HZB team artfully circumvents these optical limitations by exploiting an inherently electrical signature linked to the NV centre’s spin state. The key insight stems from recognizing that NV centres, beyond their spin, also possess an associated electrical charge. When excited by a green laser, electron-hole pairs are generated in the diamond, leading to free charge carriers. These charges interact with surface states, creating measurable changes in the local electric potential. By employing an advanced variant of atomic force microscopy known as Kelvin probe force microscopy (KPFM), the researchers were able to spatially resolve these potential differences with nanometer precision, effectively mapping the electrical landscape induced by individual NV centres.

This electrical detection method hinges on the dependence of the generated photovoltage on the spin state of the NV centre. As the NV electron spin undergoes coherent manipulation via microwave excitation, the local charge environment — and hence the photovoltage detected by the KPFM tip — responds accordingly. By tunably driving the spin resonance and simultaneously recording the spatially-resolved photovoltage, the researchers succeeded in directly reading out single-spin dynamics without relying on photon detection. This elegant strategy not only increases the signal strength compared to weak fluorescence but also significantly reduces experimental complexity.

Capturing the spin dynamics electrically through photovoltage paves the way for a fundamentally new type of quantum sensor. The readout technique is inherently more robust and compact since it omits the need for bulky optics, single-photon detectors, or complicated cryogenic setups typically required for high-fidelity spin detection. Instead, simple electrical contacts suffice, drastically shrinking the device footprint while enhancing integration potential with existing electronic architectures. The method’s sensitivity to local spin states at the nanoscale heralds advances in magnetic field sensing, nanoscale thermometry, and pressure measurements pertinent to quantum metrology.

Moreover, the ability to manipulate and detect spin coherence electrically under ambient conditions — without the need for vacuum or low temperatures — is vital for real-world implementation of diamond quantum technologies. The photovoltage change linked to spin transitions was not only observed statically but also recorded dynamically, demonstrating coherent control of spin states in time-resolved fashion. This breakthrough reveals that spin qubits in diamond can be addressed and read out fully electrically with high spatial resolution, opening novel avenues in scalable quantum information processing and spintronics.

The implications extend beyond diamond NV centres alone. Many other solid-state systems with electron spin defects, such as silicon carbide or rare-earth doped crystals, also exhibit spin-dependent charge dynamics that could be harnessed using this electrical detection scheme. By generalizing these principles, a broader class of quantum materials and devices might benefit from simplified spin readout protocols, accelerating the development of quantum computing components, spin-based sensors, and hybrid quantum-electronic platforms.

Fundamental physics also stands to gain. Mapping photovoltage signals with nanometer precision provides insight into charge-spin interactions at surfaces and interfaces, shedding light on spin-dependent charge transport phenomena. This can deepen understanding of decoherence mechanisms that limit quantum device performance and guide the engineering of tailored quantum materials with optimized spin coherence times. The research thereby bridges basic science and application-driven engineering, fostering both.

Looking forward, the HZB team envisages the integration of this photovoltage readout technique into on-chip devices composed of nanoscale diamond elements with built-in microwave and electrical contacts. Such miniaturized diamond-based quantum sensors could monitor magnetic or electric fields with unprecedented spatial resolution and compactness, suitable for portable medical diagnostics, environmental monitoring, or fundamental research. This elegant electrical approach may thus accelerate the commercialization of quantum technologies, making them practical and cost-effective.

The study represents a pivotal leap toward the vision of scalable, electrically controlled quantum systems that operate under everyday conditions. It addresses a longtime technological hurdle by substituting complex photon counting with an all-electrical interface, merging the extraordinary physical properties of diamond NV centres with powerful scanning probe microscopy. This interdisciplinary advance highlights the synergy of optics, electronics, and quantum physics in propelling next-generation quantum device engineering.

In summary, through the innovative use of photo-induced voltages detected by Kelvin probe force microscopy, the HZB research team has demonstrated an unprecedented method for single-spin readout in diamond at room temperature. By leveraging electrical signals tightly coupled to spin states, the work alleviates the need for intricate optical setups, enabling compact and robust quantum sensors and potentially revolutionizing quantum information science. This breakthrough transforms the landscape of quantum measurement technologies and creates new pathways for their real-world deployment.

Subject of Research:
Not applicable

Article Title:
Voltage detected single spin dynamics in diamond at ambient conditions

News Publication Date:
14-Apr-2025

Web References:
http://dx.doi.org/10.1038/s41467-025-58635-3

Image Credits:
Credit: Martin Künsting / HZB

Keywords:
Spin manipulation, Sensors, Quantum information science, Signaling complexes, Qubits, Atomic force microscopy