Optically detected magnetic resonance of nitrogen-vacancy centers in diamond using two-photon excitation
Lam T. Nguyen, Khanh Kieu
Abstract
We demonstrate the use of two-photon excitation for observing the ground state optically detected magnetic resonance (ODMR) of nitrogen-vacancy centers in diamonds at room temperature. An ultrafast femtosecond laser at 1040 nm was used for excitation, while fluorescence signal read out was achieved through a combination of a PMT and a lock-in amplifier. The imaging capability of two-photon excitation fluorescence (2PEF) was utilized to map the distribution of NV centers in a bulk diamond and micro-sized diamonds. For the first time, ODMR traces of the nitrogen-vacancy center are observed with two-photon excitation, providing a promising tool for fast 3D quantum sensing and imaging.
AI Impact Assessments
(3 models)Scientific Impact Assessment
Core Contribution
This paper presents the first demonstration of optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in diamond using two-photon excitation (2PE) with a 1040 nm femtosecond laser. While two-photon excited fluorescence (2PEF) of NV centers has been previously demonstrated [23-25], the novel step here is combining this nonlinear excitation scheme with microwave-driven spin readout to obtain ODMR spectra. The authors show zero-field splitting, hyperfine splitting, and Zeeman splitting in their ODMR traces, and demonstrate multi-color multiphoton imaging of both bulk HPHT diamonds and micro-sized diamonds to map the spatial distribution of NV centers.
The conceptual advance is straightforward but meaningful: two-photon excitation provides intrinsic 3D optical sectioning, which could enable localized ODMR measurements at specific depths within bulk diamond without the limitations of confocal microscopy (limited penetration depth, out-of-focus background). This addresses a real constraint in NV-based sensing, where one-photon wide-field excitation lacks axial localization and confocal microscopy suffers from depth-dependent aberrations.
Methodological Rigor
The experimental approach is sound but relatively basic in its demonstration. The setup uses a home-built Yb fiber femtosecond laser (1040 nm, ~50 fs, 7.01 MHz, 60 mW average), a standard multiphoton microscope with galvo scanning, and lock-in detection referenced to the pulse repetition rate. The microwave delivery uses a simple PCB-based loop antenna.
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Weaknesses:
Potential Impact
The work opens a pathway toward 3D-resolved quantum sensing using NV centers. If developed further, this could impact:
1. Deep-tissue or thick-sample magnetic sensing: The superior penetration depth of NIR light could enable ODMR measurements within bulk diamond or through scattering media, relevant for applications in geological diamond characterization or embedded sensor designs.
2. Nanodiamond-based biosensing: Two-photon microscopy is already standard in biological imaging; integrating ODMR could enable co-registered structural and magnetic/thermal imaging in biological samples containing fluorescent nanodiamonds.
3. Quality control of diamond materials: The multi-color imaging capability effectively screens for different defect types (NV⁰, NV⁻, other color centers), which has practical value for diamond characterization.
However, the current demonstration remains at a proof-of-concept level. The practical advantages over confocal ODMR are argued but not quantitatively demonstrated. The low repetition rate (7 MHz) and modest pulse energy (~3.5 nJ at sample) mean that photon count rates may be limiting for single-NV detection or fast ODMR mapping.
Timeliness & Relevance
NV-center-based quantum sensing is a rapidly growing field with increasing translation toward practical applications (magnetometry, thermometry, gyroscopy, battery monitoring). The need for 3D-resolved, high-resolution ODMR is genuine, particularly for applications involving bulk diamonds or nanodiamonds distributed within three-dimensional structures. The use of multiphoton microscopy — a mature and widely available technology — for NV-center ODMR is a natural convergence that has been surprisingly unexplored until now. This timeliness gives the paper relevance, even though the execution is preliminary.
Strengths & Limitations
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Overall Assessment
This is a clean proof-of-concept demonstration that establishes a new excitation modality for NV-center ODMR. The novelty is incremental — combining two existing techniques (2PE of NV centers and ODMR) — but the result is non-trivial and opens a clear path for future development. The paper would have been substantially stronger with depth-resolved ODMR demonstrations and sensitivity comparisons. As published, it serves primarily as a "first demonstration" with limited quantitative insight into performance advantages.
Generated Apr 20, 2026
Comparison History (39)
Paper 2 presents a tangible, experimental advancement in quantum sensing and 3D imaging using NV centers. This methodology has broad, immediate real-world applications across materials science, biology, and quantum technology, likely driving high citation rates and practical adoption. Paper 1 offers a profound theoretical re-evaluation of boson correlations, but its impact is more constrained to foundational quantum mechanics and lacks the immediate cross-disciplinary applications of Paper 2.
Paper 2 connects classical deep learning with quantum machine learning, addressing significant optimization bottlenecks in quantum architectures. Its ability to directly translate classical weights to quantum operations provides a highly scalable framework with broad theoretical and practical implications for AI and quantum computing. Paper 1, while innovative, focuses on a specific experimental technique for NV centers, which has a narrower scope and more specialized applications.
Paper 2 demonstrates a novel experimental technique—first-ever ODMR of NV centers using two-photon excitation—opening new possibilities for 3D quantum sensing and imaging with practical applications in materials science, biology, and quantum technologies. Its novelty (first demonstration), clear real-world applications (3D quantum sensing/imaging), and cross-disciplinary relevance (quantum physics, photonics, sensing) give it broader impact. Paper 1 presents useful quantum circuit methods for measuring invariants but is more incremental and narrower in scope, primarily advancing quantum information theory tools.
Paper 2 demonstrates a novel experimental technique—two-photon excitation ODMR of NV centers in diamond—which is a first-of-its-kind result with clear applications in 3D quantum sensing and imaging. This opens new experimental capabilities with broad impact across quantum sensing, bioimaging, and materials science. Paper 1, while technically sound, addresses a narrower theoretical problem (generator selection in QML) under restricted settings with only small-scale (5-qubit) numerical demonstrations, limiting its immediate practical impact and broader relevance.
Paper 1 presents a concrete, first-of-its-kind experimental breakthrough with immediate and broad applications in 3D quantum sensing and imaging, impacting fields like biology, medicine, and materials science. Paper 2 is highly innovative in combining differential privacy with quantum computing, but its impact is currently constrained by the theoretical nature of large-scale quantum data processing. Thus, Paper 1 promises higher near-term and interdisciplinary scientific impact.
Paper 2 addresses a more broadly impactful intersection of quantum machine learning, adversarial robustness, and symmetry—topics of high current interest. It provides a systematic theoretical framework connecting equivariance to adversarial vulnerability, with actionable insights for improving robustness. Paper 1 demonstrates a useful but incremental technical advance (two-photon excitation ODMR of NV centers), extending known techniques to a new excitation regime. While valuable for quantum sensing, its conceptual novelty and cross-field impact are more limited compared to Paper 2's contributions to understanding fundamental properties of quantum ML models.
Paper 2 likely has higher impact due to broader conceptual reach and timeliness: a rigorous, general algebraic framework for classifying and predicting perturbative behavior of all non-Hermitian multi-block degeneracies can influence many subfields (photonics, condensed matter, open quantum systems, control). Its methodological rigor and generality suggest wide reuse beyond specific platforms. Paper 1 is novel experimentally (two-photon ODMR of NV centers) with clear applications in 3D sensing, but it is more niche and platform-specific, potentially limiting breadth compared to a general theory tool for non-Hermitian physics.
Paper 1 presents a novel experimental advance—demonstrating ODMR of NV centers via two-photon excitation at room temperature—with clear methodological implementation and immediate utility for 3D imaging/quantum sensing. This can broaden NV-platform applications in microscopy, materials characterization, and bio/medical sensing, making it timely and broadly impactful. Paper 2 is primarily a critical/commentary work that corrects an interpretation and highlights methodological issues in a prior proposal; while valuable for theoretical clarity, its direct real-world applications and breadth of impact are likely narrower than a new enabling experimental technique.
Paper 1 presents a general, broadly applicable framework for interpretable ML-driven discovery of quantum phenomena across diverse datasets, with novel findings (e.g., corner-ordering in Rydberg arrays) and an open-source library. Its cross-disciplinary impact spans quantum physics, machine learning, and condensed matter. Paper 2, while demonstrating a novel two-photon excitation approach for NV-center ODMR, is more incremental—extending existing techniques to a new excitation regime—with a narrower scope of impact primarily in quantum sensing and diamond magnetometry.
Paper 1 demonstrates the first observation of ODMR of NV centers using two-photon excitation, opening new possibilities for 3D quantum sensing and imaging with deeper tissue penetration and better spatial resolution. This experimental breakthrough has broad practical applications in quantum sensing, bioimaging, and materials science. Paper 2 makes solid theoretical contributions to quantum query complexity, but its impact is more narrowly confined to theoretical computer science. The experimental novelty and cross-disciplinary applicability of Paper 1 give it higher potential scientific impact.
Paper 1 offers higher potential impact due to a more conceptually novel mechanism—thermodynamically stable non-ergodic dynamics arising from exponentially many symmetry-protected zero modes—and a predicted localization transition with clear theoretical implications for thermalization breakdown in many-body physics. Its results are broadly relevant across quantum statistical mechanics, localization, and quantum simulation, and connect to experimentally accessible platforms. Paper 2 is a valuable experimental advance (2-photon ODMR of NV centers) with clear applications, but is more incremental relative to the mature NV/ODMR field and is narrower in fundamental scope.
Paper 1 has higher potential impact due to its conceptual advance in nonequilibrium spin-glass dynamics and quantum annealing: demonstrating sub-threshold state reachability in O(1) time with thermodynamic-limit, finite-size-free integro-differential equations and improved scaling exponents. This speaks directly to optimization theory, statistical physics, and quantum computing, with broad cross-field relevance and timely interest in quantum advantage. Paper 2 is a solid experimental first (two-photon ODMR of NV centers) with clear applications in 3D sensing, but the methodological and conceptual novelty is more incremental within a mature platform.
Paper 2 likely has higher impact: it extends quantum feedback control theory by incorporating full PID (integral and derivative) terms and analyzes effects on both conditional and unconditional squeezing and tracking, with broad relevance to optomechanics, quantum metrology, and control. The approach is conceptually novel and timely for quantum control of mechanical systems, potentially influencing multiple platforms. Paper 1 is a useful experimental demonstration (2-photon ODMR of NV centers) with clear applications in 3D imaging/sensing, but it is more incremental within an already active NV/ODMR toolkit and narrower in theoretical reach.
Paper 2 likely has higher scientific impact due to broader and more immediate real-world applications: enabling two-photon-excited ODMR of NV centers at room temperature supports scalable 3D quantum sensing/imaging in biology, materials, and device metrology. The approach is timely for quantum technologies and microscopy, and can be readily adopted with existing ultrafast/2PEF setups. Paper 1 is conceptually novel and rigorous for fundamental quantum dynamics, but its impact is narrower (specialized ultrafast molecular physics/COLTRIMS) and less directly translatable to widespread sensing or engineering use cases.
Paper 2 is more novel: it reports the first observation of NV-center ODMR using two-photon excitation, enabling new experimental capability (deep/3D excitation, spatially resolved sensing) with broad relevance to quantum sensing, bioimaging, and condensed-matter/photonic platforms. Its potential applications span fast 3D quantum sensing and imaging, affecting multiple fields. Paper 1 is valuable and timely for deployment engineering of QKD, but it is primarily a performance characterization of an existing commercial device with narrower conceptual novelty and more limited cross-field impact.
Paper 1 presents a first-of-its-kind experimental breakthrough with immediate, high-impact applications in 3D quantum sensing and imaging. While Paper 2 offers a strong theoretical framework for non-Hermitian systems, Paper 1's practical applicability in the rapidly growing field of quantum technologies gives it broader interdisciplinary relevance and higher potential for immediate real-world impact.
Paper 1 offers an experimentally validated breakthrough with immediate, highly interdisciplinary applications in quantum sensing, biology, and materials science. By demonstrating two-photon excitation ODMR of NV centers, it provides a practical tool for 3D quantum imaging. Paper 2, while addressing a profound fundamental physics question, relies on a theoretical and phenomenological model that currently lacks experimental validation, making its near-term scientific impact narrower compared to the immediate technological utility of Paper 1.
Paper 1 demonstrates a novel experimental technique—first-ever ODMR of NV centers using two-photon excitation—opening new possibilities for 3D quantum sensing and imaging with deeper tissue/material penetration. This is a concrete experimental breakthrough with immediate applications in quantum sensing, bio-imaging, and materials science. Paper 2 presents a theoretical queueing framework for quantum network management, which, while rigorous and relevant, addresses a more niche problem in quantum networking theory without experimental validation and builds incrementally on existing queueing-theoretic approaches.
Paper 2 addresses a critical bottleneck in scaling fault-tolerant quantum computers by significantly reducing physical resource overhead (average 30% reduction). Its algorithmic approach to error budget optimization has broad, immediate applicability across quantum computing architecture and compiler design. While Paper 1 presents an innovative experimental technique for quantum sensing, Paper 2's dramatic resource savings in quantum design automation give it broader and more transformative potential impact in advancing practical quantum computing.
Paper 2 has higher potential impact due to a broadly applicable, algorithmic advance: a unified framework for n-th order nonlinear spectroscopy with improved efficiency via a generalized parameter-shift reformulation, demonstrated on real quantum hardware and multiple physical scenarios. This is timely for near-term quantum computing and could influence quantum algorithms, quantum chemistry/materials, and spectroscopy communities. Paper 1 is a valuable experimental first (two-photon ODMR of NV centers) with clear sensing/imaging applications, but it is more incremental and narrower in cross-field reach than a scalable computational framework.