In a groundbreaking stride toward the next frontier of molecular imaging and quantum technology, researchers at Purdue University have unveiled a novel method to detect and control individual nuclear spins within two-dimensional (2D) van der Waals materials. This breakthrough not only paves the way for atom-by-atom analysis of biological molecules but also contributes significantly to the emerging fields of quantum sensing and quantum information processing. Spearheaded by physicist Tongcang Li and his team, the research leverages optically detected nuclear magnetic resonance (NMR) spectroscopy enhanced by precisely engineered spin defects embedded in ultrathin hexagonal boron nitride (hBN).
Traditional nuclear magnetic resonance spectroscopy, familiar to many through its medical imaging counterpart—magnetic resonance imaging (MRI)—has revolutionized our ability to visualize internal structures non-invasively. Yet, the inherently limited resolution of conventional NMR has imposed a boundary on examining molecular structures at the atomic scale. Diagnostic MRI and standard NMR methods require large ensembles of atoms to produce signals, preventing scientists from observing single molecules or even individual atoms. This limitation has been an enduring obstacle in both fundamental research and applications demanding unparalleled precision, such as quantum computing components and highly sensitive molecular sensors.
Li’s team has capitalized on the unique qualities of 2D materials, which form crystalline sheets just atoms thick. Hexagonal boron nitride, specifically, exhibits a lattice structure of alternating boron and nitrogen atoms arranged in hexagonal rings and hosts naturally occurring vacancies—missing atoms that create localized sites capable of trapping electrons or nuclear spins. By introducing carbon-13 isotopes into these vacancies, the researchers transformed these sites into controllable spin defects. Unlike its most abundant isotope, carbon-12, carbon-13 has a nuclear spin that interacts with magnetic fields, enabling it to be directly probed by magnetic resonance techniques.
The process of embedding carbon-13 isotopes into hBN involved a sophisticated technique where carbon-13-enriched carbon dioxide gas was accelerated toward the hBN crystal using an electric field, causing some atoms to replace boron or nitrogen atoms in the lattice. These substitutions created a new class of spin defects that serve as sensitive probes of their atomic surroundings. By exploiting optically detected NMR, a method that couples nuclear magnetic resonance with optical readout through emitted photons, Li’s group succeeded in achieving single-spin detection. This approach allows the direct observation of the quantum state of a single nuclear spin in a material only a few atoms thick—a feat never accomplished before.
One of the hallmark achievements of this study is the ability to classify the newly discovered spin defects into three distinct groups based on their characteristic spectroscopic signals. Collaborating with theorist Yuan Ping from the University of Wisconsin-Madison, the team combined experimental observations with advanced computational modeling to identify the specific atomic structures corresponding to two of these groups. These insights are crucial because understanding the precise defect geometry is fundamental for reproducible quantum device engineering and for tuning the coherence properties of spin qubits.
Coherence time, or how long a quantum state remains unperturbed, is a critical parameter for quantum technologies. Remarkably, the carbon-13 spin defects in hBN demonstrated long coherence times even at room temperature, an attribute that positions these defects as promising quantum memories. Quantum memories are the backbone of many quantum computing and communication schemes, storing quantum information reliably during processing and transmission. The discovery that these nuclear spins maintain coherence without requiring cryogenic cooling represents a major leap toward practical quantum devices operating under ambient conditions.
The implications of this advancement extend beyond the realm of quantum computing. Magnetic resonance microscopy enhanced with atom-scale resolution can revolutionize molecular analysis by enabling the direct detection and structural characterization of individual biological molecules. This capability opens up possibilities for unprecedented insight into protein folding, enzyme mechanisms, and pharmacological interactions at the ultimate level of detail, potentially transforming drug discovery and molecular diagnostics.
Historically, Li’s research group has pursued using the electron spins in boron vacancies within hBN as quantum sensors. While these electron spins emitted light to signal local magnetic environments, their optical emission was too weak for single-defect resolution. The pivot toward carbon-13 nuclear spins represents a strategic evolution, overcoming the sensitivity barrier by directly targeting nuclear rather than electronic spins, which are less prone to environmental noise and thus capable of longer coherence times.
The sophisticated interplay between nuclear and electron spins in these 2D materials allows for precise manipulation and readout of quantum states using combinations of magnetic resonance and optical techniques. Optically detected nuclear magnetic resonance uniquely enables this control by using laser excitation to polarize and detect nuclear spins indirectly via changes in emitted light, thus merging the strengths of optical measurement with the intrinsic information contained in nuclear spins.
This research was enabled by meticulous experimental craftsmanship combined with theoretical expertise, supported by funding from the Gordon and Betty Moore Foundation, the U.S. National Science Foundation, and the Department of Energy. By revealing the pathways to harness individual nuclear spins in scalable and accessible materials like hexagonal boron nitride, the study marks a transformative moment in quantum science, where the manipulation of matter at the smallest scales can translate into revolutionary technologies.
Looking forward, the ability to deterministically place and control carbon-13 spin defects promises the creation of quantum sensors of unparalleled sensitivity and spatial resolution. These detectors could transform a wide array of scientific disciplines, ranging from nanoscale magnetic resonance imaging to quantum-enhanced biological sensing. Moreover, the research enriches the toolbox for engineering novel qubits in 2D materials, essential for developing scalable quantum networks that integrate with existing semiconductor technology.
In summary, Purdue University’s recent demonstration of single nuclear spin detection and precise control in hexagonal boron nitride heralds a new era of quantum sensing and molecular microscopy. By weaving together the subtle intricacies of materials science, quantum physics, and cutting-edge spectroscopy, this work not only solves a longstanding challenge in NMR spectroscopy but also lays the groundwork for breakthroughs in quantum computing, communications, and biomedical research—ushering us ever closer to the long-envisioned realm of atomic-scale exploration and manipulation.
Subject of Research: Not applicable
Article Title: Single nuclear spin detection and control in a van der Waals material
News Publication Date: 9-Jul-2025
Web References:
- Article in Nature: https://www.nature.com/articles/s41586-025-09258-7
- Purdue Physics Faculty: https://www.physics.purdue.edu/people/faculty/tcli.php
- Purdue Quantum Science and Engineering Institute: https://quantum.research.purdue.edu/
- Purdue National Science Foundation’s Quantum Technologies Center: https://www.purdue.edu/cqt/
- Purdue Strategic Initiatives: https://www.purdue.edu/president/strategic-initiatives
References:
Li, T., et al. “Single nuclear spin detection and control in a van der Waals material.” Nature (2025). DOI: 10.1038/s41586-025-09258-7
Image Credits: Purdue University photo/Charles Jischke
Keywords:
- NMR spectroscopy
- Quantum information
- Qubits
