Nitrogen-vacancy Centers Research Articles

Imaging of radio frequency magnetic field by multifrequency resonance

Abstract We present our results of a radio frequency (RF) imaging method in which microwave pulse errors in the field of view do not directly result in a deterioration of quantitative accuracy of the amplitude of the detected RF field by utilizing the multifrequency resonance. The amplitude of the RF field is transferred to the diamond nitrogen-vacancy (NV) center electron spin states, which are read out as light emission from the NV centers using a wide-field microscope at high throughput as an image with a pixel size of (1.65 μm)2. Importantly, our method simplifies the setup required for RF imaging, eliminating the need for high-power microwave pulses and offering a wide dynamic range for the detected RF field.

Studying Critical Parameters of Superconductor via Diamond Quantum Sensors

Abstract Critical parameters are the key to superconductivity research, and reliable instrumentations can facilitate the study. Traditionally, one has to use several different measurement techniques to measure critical parameters separately. In this work, we develop the use of a single species of quantum sensor to determine and estimate several critical parameters with the help of independent simulation data. We utilize the nitrogen-vacancy (NV) center in the diamond, which recently emerged as a promising candidate for probing exotic features in condensed matter physics. The non-invasive and highly stable nature provides extraordinary opportunities to solve scientific problems in various systems. Using a high-quality single-crystalline YBa2Cu4O8 (YBCO) as a platform, we demonstrate the use of diamond particles and a bulk diamond to probe the Meissner effect. The evolution of the vector magnetic field, the H-T phase diagram, and the map of fluorescence contour are studied via NV sensing. Our results reveal different critical parameters, including lower critical field Hc1 , upper critical field Hc2 , and critical current density jc , as well as verifying the unconventional nature of this high-temperature superconductor YBCO. Therefore, NV-based quantum sensing techniques have huge potential in condensed matter research.

Light Yields of Diamonds with Nitrogen-Vacancy Centers as Scintillators for Ionizing Radiation from 80 to 1200 eV

Light Yields of Diamonds with Nitrogen-Vacancy Centers as Scintillators for Ionizing Radiation from 80 to 1200 eV

Heralded interconversion between hyperentangled W state and hyperentangled KLM state assisted by nitrogen vacancy centers coupled with microresonators

As the hyperentanglement of photon systems holds lots of remarkable applications for enhancing channel capacity with less quantum resource, the interconversion of various hyperentangled states warrants in-depth investigation and becomes a vital work for quantum information technologies. Here we realize completely mutual conversions between spatial-polarization hyperentangled Knill-Laflamme-Milburn state and hyperentangled W state for three-photon systems, resorting to hyperparallel quantum control gates and the practical nonlinear interaction of nitrogen-vacancy centers coupled with whispering-gallery-mode microresonators. The hyperparallel quantum gates, i.e., hyperparallel controlled-not and controlled-swap gates, are fundamental prerequisites for realizing interconversions of two hyperentangled states in a deterministic way. The fidelities of these conversion processes are robust and their efficiencies are also high due to fewer nonlinear interactions and errors heralded by the response of detectors, which intensify comprehending the properties of hyperentanglement.

Magnetic noise detection and imaging from a superparamagnetic core-shell particle via an ensemble of nitrogen-vacancy centers in a thin diamond chip

Magnetic noise detection and imaging from a superparamagnetic core-shell particle via an ensemble of nitrogen-vacancy centers in a thin diamond chip

Heteroepitaxial (111) Diamond Quantum Sensors with Preferentially Aligned Nitrogen‐Vacancy Centers for an Electric Vehicle Battery Monitor

AbstractA platform for heteroepitaxial (111) chemical vapor deposition (CVD) diamond quantum sensors with preferentially aligned nitrogen vacancy (NV) centers on a large substrate is developed, and its operation as an electric vehicle (EV) battery monitor is demonstrated. A self‐standing heteroepitaxial CVD diamond film with a (111) orientation and a thickness of 150 µm is grown on a non‐diamond substrate and subsequently separated from it. The high uniformity and crystallinity of the (111)‐oriented diamond is confirmed. A 150‐µm thick NV‐diamond layer is then deposited on the heteroepitaxial diamond. The T2 value measured by confocal microscopy is 20 µs, which corresponds to substitutional nitrogen defect concentration of 8 ppm. The nitrogen‐vacancy concentration and T2* are estimated to be 0.05 ppm and 0.05 µs by continuous wave optically detected magnetic resonance (CW‐ODMR) spectroscopy in a fiber‐top sensor configuration. In a gradiometer, where two sensors are placed on both sides of the busbar, the noise floor is 17 nT/Hz0.5 in the frequency range of 10–40 Hz without magnetic shielding. The Allan deviation of the magnetic field noise in the laboratory is below 0.3 µT, which corresponds to a busbar current of 10 mA, in the accumulation time range of 10 ms to 100 s.

Quantum magnetometry of transient signals with a time resolution of 1.1 nanoseconds

Quantum magnetometers based on spin defects in solids enable sensitive imaging of various magnetic phenomena, such as ferro- and antiferromagnetism, superconductivity, and current-induced fields. Existing protocols primarily focus on static fields or narrow-band dynamical signals, and are optimized for high sensitivity rather than fast time resolution. Here, we report detection of fast signal transients, providing a perspective for investigating the rich dynamics of magnetic systems. We experimentally demonstrate our technique using a single nitrogen-vacancy (NV) center magnetometer at room temperature, reaching a best-effort time resolution of 1.1 ns, an instantaneous bandwidth of 0.9 GHz, and a time-of-flight precision better than 20 ps. The time resolution can be extended to the picosecond range by use of on-chip waveguides. At these speeds, NV quantum magnetometers will become competitive with time-resolved synchrotron X-ray techniques. Looking forward, adding fast temporal resolution to the spatial imaging capability further promotes single-spin probes as powerful research tools in spintronics, mesoscopic physics, and nanoscale device metrology.

Quantum neural network-inspired variational quantum circuit for simulating diamond 14NV center Hamiltonian with a proximal 13C isotope

Abstract We present a variational quantum circuit (VQC) that utilizes the architecture of a quantum neural network (QNN) to simulate hyperfine interactions in diamond nitrogen-vacancy (NV) centers, which is typically a challenging task for traditional computation methods. Isotopes of

In Vivo Nanodiamond Quantum Sensing of Free Radicals in Caenorhabditis elegans Models.

Free radicals are believed to play a secondary role in the cell death cascade associated with various diseases. In Huntington's disease (HD), the aggregation of polyglutamine (PolyQ) not only contributes to the disease but also elevates free radical levels. However, measuring free radicals is difficult due to their short lifespan and limited diffusion range. Here, a quantum sensing technique (T1 relaxometry) is used that involves fluorescent nanodiamonds (FND). Nitrogen vacancy (NV) centers within these nanodiamonds change their optical properties in response to magnetic noise, which allows detecting the unpaired electron from free radicals. This method is used to monitor the production of free radicals inside Caenorhabditis elegans models of Huntington's disease in vivo and in real-time. To investigate if radical generation occurs near polyglutamine expansions, a strain expressing Q40 yellow fluorescent protein (Q40::YFP, polyglutamine expansion overexpressed in the muscle) is used. By applying T1 relaxometry on FNDs in the body wall muscle, it is found that the production of free radicals significantly increase when PolyQ is expressed there (compared to the FNDs in intestine). The technique demonstrates the submicrometer localization of free radical information in living animals and direct measurement of their level, which may reveal the relation between oxidative stress and Huntington's disease.

Harnessing individual nitrogen-vacancy centers with a compact and portable confocal microscope

Abstract Recent advancements in quantum technology have highlighted the potential of nitrogen-vacancy (NV) centers in diamond. However, fully realizing this potential requires addressing challenges related to the size, complexity, and cost of current optical systems used for NV center manipulation. In this work, we present a compact and portable confocal setup specifically designed for the efficient detection and control of single NV centers. Our system facilitates optical initialization and readout of individual NV center photoluminescence signals, enabling coherent spin control and nanoscale-resolution magnetic field sensing.

NV center creation in diamond by local CW laser irradiation of shallow implantednitrogen

Abstract A novel creation procedure for the nitrogen-vacancy center in diamond is investigated. After shallow nitrogen implantation, a continuous-wave laser is used to induce NV formation, while simultaneously exciting fluorescence to enable live observation. Our investigations imply that a different mechanism than heat induced vacancy diffusion causes the formation of NV centers with this method and we suggest possible alternative pathways which could be responsible, based on the observed properties. Furthermore, we test the procedure for its capabilities for the controlled creation of single centers and show that the emergence of individual centers can be tracked, while achieving sub-micrometer spatial precision.

Nanoscale Magnetic Ordering Dynamics in a High Curie Temperature Ferromagnet.

Thermally driven transitions between ferromagnetic and paramagnetic phases are characterized by critical behavior with divergent susceptibilities, long-range correlations, and spin dynamics that can span kHz to GHz scales as the material approaches the critical temperature Tc, but it has proven technically challenging to probe the relevant length and time scales with most conventional measurement techniques. In this study, we employ scanning nitrogen-vacancy center based magnetometry and relaxometry to reveal the critical behavior of a high-Tc ferromagnetic oxide near its Curie temperature. Cluster analysis of the measured temperature-dependent nanoscale magnetic textures points to a 3D universality class with a correlation length that diverges near Tc. Meanwhile, the temperature-dependent spin dynamics, measured through all optical relaxometry suggest that the phase transition is in the XY universality class. Our results capture both static and dynamic aspects of critical behavior, providing insights into universal properties that govern phase transitions in magnetic materials.

Enhancing the Optically Detected Magnetic Resonance Signal of Organic Molecular Qubits.

In quantum information science and sensing, electron spins are often purified into a specific polarization through an optical-spin interface, a process known as optically detected magnetic resonance (ODMR). Diamond-NV centers and transition metals are both excellent platforms for these so-called color centers, while metal-free molecular analogues are also gaining popularity for their extended polarization lifetimes, milder environmental impacts, and reduced costs. In our earlier attempt at designing such organic high-spin π-diradicals, we proposed to spin-polarize by shelving triplet M S = ±1 populations as singlets. This was recently verified by experiments albeit with low ODMR contrasts of <1% at temperatures above 5 K. In this work, we propose to improve the ODMR signal by moving singlet populations back into the triplet M S = 0 sublevel, designing a true carbon-based molecular analogue to the NV center. Our proposal is based upon transition-orbital and group-theoretical analyses of beyond-nearest-neighbor spin-orbit couplings, which are further confirmed by ab initio calculations of a realistic trityl-based radical dimer. Microkinetic analyses point toward high ODMR contrasts of around 30% under experimentally feasible conditions, a stark improvement from previous works. Finally, in our quest toward ground-state optically addressable molecular spin qubits, we exemplify how our symmetry-based design avoids Zeeman-induced singlet-triplet mixings, setting the scene for realizing electron spin qubit gates.

Indirect control of 13C nuclear spin in nitrogen vacancy center in diamond

Indirect control of 13C nuclear spin in nitrogen vacancy center in diamond

Fluorescent nanodiamond scintillators for beam diagnostics of EUV and soft X-ray in photolithographic applications.

Extreme ultraviolet (EUV) lithography is a cutting-edge technology in contemporary semiconductor chip manufacturing. Monitoring the EUV beam profiles is critical to ensuring consistent quality and precision in the manufacturing process. This study uncovers the practical use of fluorescent nanodiamonds (FNDs) coated on optical image sensors for profiling EUV and soft X-ray (SXR) radiation beams. We employed a positive electrospray ion source to deposit 100 nm FNDs onto indium tin oxide (ITO)-coated substrates, forming 1 μm thick films. The scintillation films exhibited approximately 50% transparency in the visible region and could emit red fluorescence from neutral nitrogen-vacancy (NV0) centers in the FNDs when exposed to EUV/SXR radiation. We evaluated the performance of a device featuring an FND coating on a fiber optic plate (FOP) attached to the sensor of a complementary metal-oxide semiconductor (CMOS) camera using synchrotron radiation across the 80-1400 eV energy range. At 91.8 eV (or a wavelength of 13.5 nm), the fiber-coupled device exhibited a noise-equivalent power density of 0.25 μW cm-2 Hz-1/2, approximately eight times lower than that of an f/1.0 lens-coupled system. This enhanced sensitivity makes the FND/FOP-based detection system useful for beam profiling of various EUV/SXR radiation sources. Our results highlight the promising potential of electrosprayed FND scintillators as a cost-effective and versatile diagnostic tool for advancing next-generation photolithography.

Magnetic field characterization of edge currents in quantum spin Hall insulators

Abstract Quantum spin Hall (QSH) insulators are materials with nontrivial topological properties, characterized by helical edge currents. In 2D strips, the application of a bias voltage along the edge generates a magnetization that can be measured using quantum sensors and magnetometry techniques. In this work, we calculate the magnetic field in the vicinity of the edge and explore the potential role of nitrogen-vacancy (NV) centers in diamond as local probes for the characterization of QSH edge states in topological insulators. We characterize the magnetic field near the edges produced by both electron currents and spin accumulation at the edge. We focus on identifying the position from the edge at which the effects of spin accumulation become detectable. We observe that a larger gap between the conduction and valence bands, along with a lower Fermi velocity, results in a stronger magnetic field, with the detectable spin accumulation being more concentrated near the edge. Conversely, a smaller gap results in a slight reduction in the magnetic field magnitude, but the field associated with spin accumulation becomes detectable further from the edge. This work provides insights that could be useful for the characterization of topological materials and the development of novel electro-optical devices.&amp;#xD;

A glovebox-integrated confocal microscope for quantum sensing in inert atmosphere.

Confocal microscopy is an invaluable tool for studying fluorescent materials and finds a wide application in biology and in quantum sensing. Usually, these experiments are performed under ambient conditions, but many materials are air sensitive (for example, black phosphorus) and degrade quickly under the strong laser irradiance. Here, we present a glovebox-integrated confocal microscope designed for nitrogen-vacancy (NV) center-based nano-scale sensing and NMR spectroscopy in an inert gas atmosphere. Using black phosphorus as a test material, we confirm that the glovebox maintains low oxygen levels and prevents material degradation during laser exposure. We demonstrate the setup's capabilities through experiments that show NV center detection and spin manipulation under a black phosphorus flake. This custom-built system enables the study of air-sensitive materials and opens new perspectives for exploring surface chemistry in a controlled environment. Our work outlines both the strengths and the challenges of using a glovebox-integrated confocal microscope for quantum technology applications.

Nitrogen vacancy centers integrated magnetometer based on multi-frequency modulation measurement technique

Purpose This study aims to improve the sensitivity of magnetic detection. In this article, a multi-frequency modulation technique is used to increase the magnetic detection sensitivity of diamond nitrogen vacancy (NV) centers sensors. Design/methodology/approach In the field of magnetic detection, NV centers have corresponding advantages due to their unique long coherence property at room temperature. The important indicators for NV centers magnetometers are the magnetic detection sensitivity of the NV centers and the integration of the magnetometer. To solve this problem, the authors propose a multi-frequency modulated magnetic detection technique, using an integrated probe as well as a lock-in amplifier for the double enhancement of sensitivity as well as integration. Findings The following results can be obtained by processing and calculating the experimental data with an integrated lock-in amplifier circuit with an area of 27.50 cm2 and a probe volume of 3.12 cm3. The multi-frequency modulation technique was used to increase the magnetic detection sensitivity of the NV centers from 8.59 nT/Hz1 / 2–2.42 nT/Hz1 / 2. Research limitations/implications The authors propose a signal modulation technique with an integrated design, which achieves an improvement in the sensitivity of the sensor’s magnetic detection through practical testing. Originality/value The authors propose a signal modulation technique with an integrated design, which achieves an improvement in the sensitivity of the sensor’s magnetic detection through practical testing. This technique provides new research solution for the subsequent improvement of the magnetic detection sensitivity.

Color-Coded Traffic Signal Method Combined with Nanodiamond Quantum Sensing for Accurate miRNA Detection.

Background noise interferes with the accurate detection of early tumor biomarkers. This study introduces a method that effectively reduces background noise to enhance detection accuracy by combining a color-coded signaling approach with the unique fluorescent properties and room-temperature tunable quantum spin characteristics of fluorescent diamonds (FNDs) with nitrogen-vacancy centers. In this approach, a red signal indicates the presence of the target analyte within the spectral region, a green signal indicates its absence, and a yellow signal indicates the need for further analysis using FNDs' quantum spin properties for optical detection magnetic resonance (ODMR) to distinguish the FND signal from background noise. Preliminary results demonstrate that this method enables the detection of breast cancer-related miRNA-21 and miRNA-96 concentrations as low as 1 fM within a 100 × 100 μm2 area, achieving single-molecule detection capability. This method is suitable for accurate biomarker identification and detection under high-background fluorescence conditions.

Room-Temperature Solid-State Maser Amplifier

Masers once represented the state of the art in low-noise microwave amplification technology but eventually became obsolete due to their need for cryogenic cooling. Masers based on solid-state spin systems perform most effectively as amplifiers, since they provide a large density of spins and can, therefore, operate at relatively high powers. While solid-state maser oscillators have been demonstrated at room temperature, continuous-wave amplification in these systems has only ever been realized at cryogenic temperatures. Here, we report on a continuous-wave solid-state maser amplifier operating at room temperature. We achieve this feat using a practical setup that includes an ensemble of nitrogen-vacancy center spins in a diamond crystal, a strong permanent magnet, and a simple laser diode. We describe important amplifier characteristics including gain, bandwidth, compression power, and noise temperature and discuss the prospects of realizing a room-temperature near-quantum-noise-limited amplifier with this system. Finally, we show that in a different mode of operation the spins can be used to reduce the microwave noise in an external circuit to cryogenic levels, all without the requirement for physical cooling. Published by the American Physical Society 2024