The study culminated in a detailed exploration published in the journal Physical Review Materials, where it received the honor of being singled out as an Editors’ Suggestion paper. This recognition underscores the relevance and impact of the findings. The researchers effectively bridged theoretical models with empirical data, utilizing first-principles surface models along with quantum dynamics simulations. This comprehensive approach enabled them to identify the culprits behind decoherence: not merely the presence of defects on the surface, but the dynamic movement of these surface spins.

Giulia Galli, a distinguished professor at the University of Chicago Pritzker School of Molecular Engineering and a senior scientist at Argonne National Laboratory, emphasized the significance of understanding surface noise dynamics. This insight reveals that surface noise is not a static disturbance; rather, it fluctuates over time, catalyzing rapid decoherence among NV centers. This dynamic aspect of noise presents a frontier for engineering improvements in quantum sensors, aiming to enhance their stability and functionality.

The researchers’ dedication to unraveling the details surrounding the noise impacting NV centers led to a clearer understanding of the physics involved. The study articulates the profound implications for the design and engineering of diamond surfaces. Results indicate that specific surface terminations substantially influence the preservation of quantum coherence, which is critical for the future of quantum sensing technologies. Through systematic investigation, the team discovered that surfaces terminated with oxygen or nitrogen effectively maintain quantum properties for NV centers positioned just below the surface, whereas hydrogen and fluorine terminologies awaken unwanted magnetic noise, leading to shortened coherence times.

Conventional wisdom often dubbed the noise sources surrounding NV centers as “X spins” or “dark spins,” due to an inherent lack of clarity regarding their microscopic identities. The current research decisively tracks the sources of instability, pinpointing the types of spins that contribute to decoherence, paving the way for strategies aimed at mitigating surface noise. By addressing these points of noise, researchers aspire to fabricate diamond surfaces that will enable advanced quantum sensors, allowing for enhanced measurement accuracy and sensitivity.

The work of the research team hinges heavily on integrating density functional theory-based atomistic models with advanced quantum decoherence simulations. This powerful combination proved instrumental in isolating the predominant noise mechanisms originating from the surface. Such focused research not only deepens understanding but also directs future investigations toward the elimination of noise, ultimately enhancing the capabilities of quantum devices.

Moreover, they highlighted the potential issues arising during the diamond surface fabrication processes. Unwanted surface defects, such as dangling bonds—places where bonds haven’t formed properly—can harbor unpaired electrons, which generate magnetic noise as a byproduct of their fluctuations. This noise interferes significantly with the NV centers’ coherence, complicating measurements of weak signals that are crucial in many applications.

The study makes a compelling argument regarding the nuances of surface chemistry and facet orientation in relation to NV center coherence. As the team meticulously explored various surface terminations, they discovered that chemical termination plays a pivotal role in maintaining coherence. Oxygen and nitrogen-terminated surfaces provide a far more stable quantum environment, whereas incompatible surface chemistries introduce detrimental noise, fundamentally altering the reliability of quantum measurements.

While aspects such as chemical termination are undeniably important, the researchers revealed that the primary determinants of coherence involve electron relaxation and hopping at the surface. This electron movement interacts with the same laser pulses used for manipulating and reading the NV centers, generating time-varying magnetic fields that amplify noise. The team’s findings highlight the intricate dance between surface interactions and the fundamental mechanics of quantum coherence.

Ultimately, the research not only elucidates the complex web of interactions at play but also lays out a clear roadmap for future innovations in NV-center-based quantum technologies. With their findings, the authors have illuminated pathways that could lead to the realization of more powerful and sensitive quantum sensors, beneficial across a multitude of fields, including materials science, biological detection, and beyond.

The researchers confidently assert that once the effects of electron motion at the surface are accounted for, theoretical models will begin to align with experimental results. Such convergence marks a pivotal moment in quantum research, indicating the potential for unprecedented advancements in the field of quantum sensing. With each step forward, the realm of quantum technology becomes increasingly tangible, opening new horizons for future discoveries.

This comprehensive investigation reflects not only a deep understanding of quantum mechanics and material science but also a commitment to advancing the frontiers of knowledge in quantum technology. With rapid developments projected, this study sets a robust foundation for engineers and scientists eager to transform the landscape of quantum sensors and information technologies.

In conclusion, the implications of this study extend far beyond mere academic interest. The understanding of noise in NV centers holds the potential to inform the creation of advanced quantum devices that could redefine our grasp of information processing and measurement accuracy in scientific inquiries. As researchers continue to decode the secrets of quantum coherence, the excitement surrounding this field only intensifies, heralding a new era of technological innovation.

Subject of Research: The impact of diamond surface properties on quantum coherence of nitrogen-vacancy (NV) centers.
Article Title: Understanding surface-induced decoherence of NV centers in diamond
News Publication Date: 5-Feb-2026
Web References: Journal Link
References: [Physical Review Materials]
Image Credits: Elaina Eichorn

Keywords

Quantum information, applied sciences and engineering.

At the heart of SPINNING’s innovation lies the synthesis and manipulation of spin qubits hosted in color centers within diamond substrates. These color centers—primarily nitrogen vacancy (NV), germanium vacancy (GeV), and tin vacancy (SnV) defects—serve as robust quantum bits that maintain coherence far beyond what is typical for superconducting Josephson junction (SJJ) based systems. By embedding these spin qubits within diamond crystals featuring a meticulously controlled nuclear spin environment, the team achieved a quieter quantum landscape, suppressing decoherence mechanisms that traditionally scramble fragile quantum states. This refined material platform is foundational for the project’s unprecedented performance metrics.

One of the most distinguishing accomplishments realized by SPINNING is the successful entanglement of two separate quantum registers, each comprising six qubits, over an impressive distance exceeding 20 meters. This feat was enabled by high-quality photonic coupling facilitated through diamond-based optical microresonators. Such long-range coupling vastly exceeds the typical scale of quantum entanglement which often occurs over micrometer or millimeter distances in superconducting architectures. Achieving an average fidelity surpassing 0.9 in state similarity, this breakthrough demonstrates an unprecedented capacity for distributed quantum operations, a vital capability for constructing more powerful quantum networks and modular computers.

The architectural design pursued by SPINNING is truly hybrid and scalable, integrating the distinct advantages of spin qubits with a photonic interconnect framework. Optical microresonators act as efficient mediators, converting quantum information between spin states and photons. These photons then carry quantum correlations across spatially separated registers, allowing seamless, coherent communication. This design not only enables scalability across tens of meters but also promises compatibility with conventional computational infrastructure, fostering a hybrid quantum-classical ecosystem essential for practical quantum computing adoption.

Technological innovation extended beyond qubit creation, encompassing major progress in diamond microresonator fabrication achieving high Q-factors, essential for minimizing optical losses and ensuring strong spin-photon coupling. Precisely positioning color centers within these microresonators necessitated cutting-edge nanofabrication techniques, optimizing spatial overlap between the qubit’s electronic spin transitions and resonator modes. Moreover, the project developed novel quantum-grade electronics to operate this hybrid quantum device, advancing control systems capable of precise timing and error mitigation—critical requirements for functional quantum computation.

SPINNING’s advancements also chart new territory in quantum error rates and coherence times surpassing leading superconducting quantum devices. The developed spin-photon quantum computer achieved single-qubit gate error rates below 0.5%, rivalling or bettering prominent SJJ-based quantum processors such as IBM’s Eagle and Heron systems, despite operating at higher temperatures and with fewer qubits currently. Most strikingly, coherence times exceeded 10 milliseconds, representing an increase by two orders of magnitude over typical superconducting qubit temporal stability measured in microseconds. This extended coherence offers increased operational windows to execute complex quantum algorithms before decoherence intervenes.

Supporting these quantum hardware leaps, software and infrastructure developments within SPINNING were pivotal. The consortium integrated firmware and control protocols tailored to the unique hybrid quantum design, enabling real-time error detection and operational optimization. The team also demonstrated practical use cases including initial applications in artificial intelligence, signaling that this technology is approaching real-world viability. The collaboration between academic and industrial partners ensured that both foundational research and applied technology pathways were concurrently advanced.

The consortium assembling this major advance combined expertise from six universities, two non-profit research institutions, and several leading SMEs and spin-offs within quantum technology fields. Spearheaded by Fraunhofer Institute for Applied Solid State Physics IAF, this multi-disciplinary alliance leveraged advances in material sciences, quantum optics, and computational methods. Their collaborative efforts were underscored by strategic funding and alignment with Germany’s federal quantum technology roadmap, securing a €16.1 million investment to drive the translation of quantum fundamentals into market-ready hardware.

In comparison to SJJ quantum computers, SPINNING’s diamond-based system holds remarkable promise for room-temperature operation or near-room-temperature regimes, effectively reducing the cryogenic infrastructure demands so prevalent in superconducting qubit systems. Such thermal resilience reduces overall system complexity, energy consumption, and the cost of scaling quantum processors. This paradigm shift could accelerate the commercialization timelines for quantum solutions, fostering wider adoption across sectors ranging from chemical simulations and cryptography to machine learning.

Beyond the technical achievements, SPINNING’s demonstration of robust entanglement spanning multiple registers and long distances lays groundwork for future quantum networks. These interconnected quantum nodes, sharing entangled states over tens of meters, form building blocks for distributed quantum computing and quantum communication protocols, vital for realizing the quantum internet. The project thus not only advances standalone quantum processors but also contributes critical infrastructure for next-generation secure communications and computational paradigms.

The fundamental physics explored by SPINNING—with its manipulation of specific vacancy defects and nuclear spins within diamond—also enriches understanding of spin coherence mechanisms and decoherence suppression strategies. These insights can guide future optimization of materials and novel quantum devices with tailored characteristics. Furthermore, the successful demonstration of germanium and tin vacancy center applications within supporting photonic components expands the family of viable solid-state qubits, broadening the scope of materials science research in quantum information.

In summary, the SPINNING project represents a landmark achievement in the quantum computing field, illustrating that spin-photon hybrid quantum systems in diamond offer a powerful, scalable, and energy-efficient alternative to existing superconducting technologies. By combining long coherence times, low error rates, and scalable photonic connectivity, this new approach paves the way for advanced quantum computing platforms. As the quantum technology race intensifies globally, innovations like SPINNING will play a critical role in shaping the future landscape of quantum information science and technology.

Subject of Research: Spin-photon hybrid quantum computing; diamond spin qubits; quantum entanglement; solid-state quantum processors; photonic microresonators.

Article Title: SPINNING: Pioneering Scalable Spin-Photon Quantum Computing with Diamond Qubits

News Publication Date: June 2023

Web References: https://www.spinning-quantencomputing.de/en/partners.html

Image Credits: Fraunhofer IAF

Keywords: Quantum computing, spin qubits, diamond color centers, photonic coupling, quantum entanglement, solid-state quantum technology, coherence time, quantum error rates, distributed quantum computing, quantum hardware, hybrid quantum systems, microresonators

At the heart of this innovation lies the unique quantum properties of diamonds at the nanoscale—specifically, nanodiamonds embedded with nitrogen-vacancy (NV) centers. These NV centers act as extraordinary quantum sensors, capable of detecting electromagnetic signals with exceptional precision, even at room temperature. Unlike conventional radio receivers that rely on classical electronic components, these quantum receivers exploit spin states within nanodiamonds to capture and process quantum information encoded in radio frequency (RF) waves.

The research team, led by Zeng, Q., Zhang, J., and Gupta, M., addresses one of the principal challenges in modern wireless communication: the demand for receivers that can operate with minimal noise while maintaining high bandwidth. Traditional semiconductor-based radios often suffer from thermal noise and energy dissipation, limiting their sensitivity and overall performance. Nanodiamond-based quantum receivers, on the other hand, leverage quantum coherence phenomena to significantly reduce noise floors, thereby enhancing the clarity and quality of received signals.

From a technical perspective, these quantum receivers operate by initializing and reading out the spin state of NV centers using precisely controlled laser pulses and microwave fields. When exposed to an incoming RF signal, the interaction modifies the spin environment of the NV centers, which can then be detected through changes in fluorescence intensity. This fluorescence-based readout enables direct quantum measurement of electromagnetic fields, a capability unattainable with classical receivers.

Such quantum-enhanced sensitivity opens new avenues for radio access in dense urban environments and remote areas alike. In cities crowded with electromagnetic interference from numerous devices and networks, nanodiamond quantum receivers could filter through noise to retrieve pristine signals. Meanwhile, in rural or underdeveloped regions lacking extensive communication infrastructure, these receivers could enable highly efficient, low-power devices to connect reliably to network services over greater distances.

Security implications of this research are equally compelling. Quantum receivers inherently provide resistance to eavesdropping and jamming due to their dependence on fragile quantum states for signal detection. This intrinsic security layer makes nanodiamond quantum receivers promising candidates for applications where confidential and tamper-proof communications are critical, such as military, financial, and healthcare networks.

Moreover, the scalability of these quantum receivers forms a crucial part of this advancement. Nanodiamonds can be synthesized in large quantities using cost-effective chemical vapor deposition methods, allowing integration into existing communication hardware with minimal modifications. The potential for mass production heralds a future where quantum-enhanced radio receivers become standard components in smartphones, IoT devices, and infrastructure, paving the way toward truly ubiquitous radio access.

The energy efficiency gains are equally noteworthy. Because these quantum receivers operate at room temperature and avoid the cooling requirements typical of other quantum sensors, they consume significantly less power. This reduction in energy demands aligns perfectly with global efforts to develop greener technologies, critical for supporting sprawling networks of connected devices without escalating energy footprints.

Another technical dimension of the research lies in the meticulous engineering necessary to optimize NV center placement, orientation, and coherence times within nanodiamonds. The team’s breakthroughs in material science and quantum control enable prolonged interaction times and precise manipulation, critical parameters ensuring the receivers’ effectiveness in practical deployment scenarios. Such control represents a sophisticated interplay between quantum physics and nanofabrication technologies.

The integration of nanodiamond quantum receivers into radio access networks also potentially enhances bandwidth capabilities. Advances in quantum signal processing allow for subtler modulation detection and decoding strategies, potentially multiplying the communication capacity per unit of spectrum. This quantum leap in spectral efficiency could alleviate congestion in the ever-growing wireless data ecosystem.

Importantly, this research situates itself within the broader quantum technology revolution, complementing developments in quantum computing and quantum cryptography. By extending quantum advantages beyond computing paradigms into the domain of classical communication networks, nanodiamond-based quantum receivers highlight the versatility and transformative power of quantum engineering.

As with any emergent technology, challenges remain before widespread adoption can be realized. Key hurdles include ensuring stable reproducibility of nanodiamond properties across manufacturing batches, integrating control electronics with minimal overhead, and developing robust software for quantum signal decoding. The researchers outline promising early progress on these fronts, supported by collaborative efforts across interdisciplinary teams.

Looking ahead, the potential integration of these quantum receivers with evolving 6G and beyond-generation wireless standards could provide the necessary boost to support next-level connectivity demands. From immersive augmented reality experiences to autonomous systems requiring ultra-low latency links, the quantum receiver’s capabilities appear perfectly aligned with future technological needs.

Furthermore, the possible fusion of nanodiamond quantum receivers with satellite and space communication systems offers exciting prospects for global coverage. Their resilience against high-radiation environments and sensitivity to weak signals may redefine satellite communication paradigms, enabling novel services such as deep-space internet relay networks or resilient defense communication channels.

In summary, the work by Zeng, Zhang, Gupta, and colleagues represents a pivotal milestone toward realizing truly ubiquitous radio access. By harnessing the quantum prowess of nanodiamonds, this research unlocks a visionary pathway where wireless communication transcends current limitations in sensitivity, security, and energy efficiency. As quantum receiver technology matures, it promises to fundamentally reshape how humanity connects, opening up horizons for innovation and connectivity previously confined to the realm of science fiction.

The confluence of advanced materials science, quantum physics, and communication engineering demonstrated here exemplifies the multi-disciplinary approach critical for next-generation technologies. Following this trajectory, researchers and industry stakeholders are poised to translate the quantum receiver blueprint into tangible products, gradually embedding quantum advantages into everyday communication infrastructures, and cementing the dawn of a quantum-enhanced wireless era.

Subject of Research: Nanodiamond-based quantum receivers for ubiquitous radio access

Article Title: Towards ubiquitous radio access using nanodiamond based quantum receivers

Article References:
Zeng, Q., Zhang, J., Gupta, M. et al. Towards ubiquitous radio access using nanodiamond based quantum receivers. Commun Eng 4, 60 (2025). https://doi.org/10.1038/s44172-025-00396-4

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