Nitrogen-vacancy Color Centers Research Articles

High-Dynamic-Range Integrated NV Magnetometers

High-dynamic-range integrated magnetometers demonstrate extensive potential applications in fields involving complex and changing magnetic fields. Among them, Diamond Nitrogen Vacancy Color Core Magnetometer has outstanding performance in wide-range and high-precision magnetic field measurement based on its inherent high spatial resolution, high sensitivity and other characteristics. Therefore, an innovative frequency-tracking scheme is proposed in this study, which continuously monitors the resonant frequency shift of the NV color center induced by a time-varying magnetic field and feeds it back to the microwave source. This scheme successfully expands the dynamic range to 6.4 mT, approximately 34 times the intrinsic dynamic range of the diamond nitrogen-vacancy (NV) center. Additionally, it achieves efficient detection of rapidly changing magnetic field signals at a rate of 0.038 T/s.

Molecular dynamics simulation study of nitrogen vacancy color centers prepared by carbon ion implantation into diamond

Nitrogen vacancy (NV) color centers in diamond have useful applications in quantum sensing and fluorescent marking. They can be generated experimentally by ion implantation, femtosecond lasers, and chemical vapor deposition. However, there is a lack of studies of the yield of NV color centers at the atomic scale. In the molecular dynamics simulations described in this paper, NV color centers are prepared by ion implantation in diamond with pre-doped nitrogen and subsequent annealing. The differences between the yields of NV color centers produced by implantation of carbon (C) and nitrogen (N) ions, respectively, are investigated. It is found that C-ion implantation gives a greater yield of NV color centers and superior location accuracy. The effects of different pre-doping concentrations (400–1500 ppm) and implantation energies (1.0–3.0 keV) on the NV color center yield are analyzed, and it is shown that a pre-doping concentration of 1000 ppm with 2 keV C-ion implantation can produce a 13% yield of NV color centers after 1600 K annealing for 7.4 ns. Finally, a brief comparison of the NV color center identification methods is presented, and it is found that the error rate of an analysis utilizing the identify diamond structure + coordination analysis method is reduced by about 7% compared with conventional identification methods.

NV color center fluorescence signal measurement based on FPGA architecture

Nitrogen-vacancy (NV) quantum defects in diamond are sensitive detectors of magnetic fields. Then, the existing sensing technologies based on diamond NV centers rely on bulky and expensive instruments, which must be replaced by a more compact design. Here we combine NV quantum sensing technology with integrated circuit technology to create a compact and easy-to-operate platform. Using the existing integrated circuit technology, we integrate the lock-in amplifier, microwave generator and TTL modulator together. with this platform, we can obtain a magnetic sensitivity of 5.72μT/Hz 1/2.

Hot ion implantation to create dense NV center ensembles in diamond

Creating dense and shallow nitrogen-vacancy (NV) ensembles with good spin properties is a prerequisite for developing diamond-based quantum sensors exhibiting better performance. Ion implantation is a key enabling tool for precisely controlling spatial localization and density of NV color centers in diamond. However, it suffers from a low creation yield, while higher ion fluences significantly damage the crystal lattice. In this work, we realize N2+ ion implantation in the 30–40 keV range at high temperatures. At 800 °C, NV's ensemble photoluminescence emission is three to four times higher than room temperature implanted films, while narrow electron spin resonance linewidths of 1.5 MHz, comparable to well-established implantation techniques, are obtained. In addition, we found that ion fluences above 2 × 1014 ions/cm2 can be used without graphitization of the diamond film, in contrast to room temperature implantation. This study opens promising perspectives in optimizing diamond films with implanted NV ensembles that could be integrated into quantum sensing devices.

Unraveling Eumelanin Radical Formation by Nanodiamond Optical Relaxometry in a Living Cell.

Defect centers in a nanodiamond (ND) allow the detection of tiny magnetic fields in their direct surroundings, rendering them as an emerging tool for nanoscale sensing applications. Eumelanin, an abundant pigment, plays an important role in biology and material science. Here, for the first time, we evaluate the comproportionation reaction in eumelanin by detecting and quantifying semiquinone radicals through the nitrogen-vacancy color center. A thin layer of eumelanin is polymerized on the surface of nanodiamonds (NDs), and depending on the environmental conditions, such as the local pH value, near-infrared, and ultraviolet light irradiation, the radicals form and react in situ. By combining experiments and theoretical simulations, we quantify the local number and kinetics of free radicals in the eumelanin layer. Next, the ND sensor enters the cells via endosomal vesicles. We quantify the number of radicals formed within the eumelanin layer in these acidic compartments by applying optical relaxometry measurements. In the future, we believe that the ND quantum sensor could provide valuable insights into the chemistry of eumelanin, which could contribute to the understanding and treatment of eumelanin- and melanin-related diseases.

Magnetic-field-assisted optical fiber quantum temperature sensor with enhanced sensitivity.

In recent years, utilizing nitrogen-vacancy color centers in diamond for temperature sensing has drawn great attention. However, increasing the sensitivity has encountered challenges due to the intrinsic temperature-dependent energy level shift, i.e., temperature responsivity, being limited to -74 kHz/K. In this Letter, we take advantage of the magnetic field to regulate the energy level to enhance temperature sensitivity. The sensor is formed by adhering a micron-sized diamond on the end face of an optical fiber, and a small magnet is mounted at a certain distance with the diamond exploiting a cured polydimethylsiloxane block as the bridge. The temperature change leads to the variation of the distance between the diamond and the magnet, thus affecting the magnetic strength felt by the diamond. This finally contributes an additional temperature-induced energy level shift, giving rise to an enhanced sensitivity. Experimental results demonstrated the proposed scheme and achieved a 4.2-fold improvement in the temperature responsivity and a 2.1-fold enhancement in sensitivity. Moreover, the diamond and the fiber-optic integrated structure improve the portability of the sensor.

The concentration estimation for ensemble of NV– color centers with spin coherent manipulation

The concentration and distribution of negatively charged nitrogen-vacancy color centers (NV−) directly affect the sensitivity and resolution of quantum sensing. In this paper, a simple method is proposed to estimate the concentration of the ensemble of NV− centers with spin coherent manipulation. The stray fluorescence is eliminated by separating the fluorescence near the NV− zero-phonon line. By introducing a single NV− fluorescence quantitative model, the number of NV− centers in the diamond under test can be obtained. The average concentration of the ensemble of NV− centers in the sample can be obtained by combining the detection volume. Compared with the results measured by electron spin resonance, the concentration of NV− centers measured by our method can be verified, and the maximum error between the two methods is less than 4.3%. The results show that the method provides an effective reference for accurately characterizing the concentration distribution characteristics of the NV− ensemble.

High precision microwave measurement based on nitrogen-vacancy color center and application in velocity detection.

Wide-range high-precision velocity detection with nitrogen-vacancy (NV) color center has been realized. By treating the NV color center as a mixer, the high-precision microwave measurement is realized. Through optimization of acquisition time, the microwave frequency resolution is improved to the mHz level. Combined with the frequency-velocity conversion model, velocity detection is realized in the range of 0-100 cm/s, and the velocity resolution is up to 0.012 cm/s. The maximum deviation in repeated measurements does not exceed 1/1000. Finally, combined with the multiplexed microwave reference technique, the range of velocity can be extended to 7.4 × 105 m/s. All of the results provide reference for high-precision velocity detection and play a significant role in various domains of quantum precision measurement. This study provides a crucial technical foundation for the development of high-dynamic-range velocity detectors and novel quantum precision velocity measurement technologies.

AI-Enhanced Visual-Spectral Synergy for Fast and Ultrasensitive Biodetection of Breast Cancer-Related miRNAs.

In biomedical testing, artificial intelligence (AI)-enhanced analysis has gradually been applied to the diagnosis of certain diseases. This research employs AI algorithms to refine the precision of integrative detection, encompassing both visual results and fluorescence spectra from lateral flow assays (LFAs), which signal the presence of cancer-linked miRNAs. Specifically, the color shift of gold nanoparticles (GNPs) is paired with the red fluorescence from nitrogen vacancy color centers (NV-centers) in fluorescent nanodiamonds (FNDs) and is integrated into LFA strips. While GNPs amplify the fluorescence of FNDs, in turn, FNDs enhance the color intensity of GNPs. This reciprocal intensification of fluorescence and color can be synergistically augmented with AI algorithms, thereby improving the detection sensitivity for early diagnosis. Supported by the detection platform based on this strategy, the fastest detection results with a limit of detection (LOD) at the fM level and the R2 value of ∼0.9916 for miRNA can be obtained within 5 min. Meanwhile, by labeling the capture probes for miRNA-21 and miRNA-96 (both of which are early indicators of breast cancer) on separate T-lines, simultaneous detection of them can be achieved. The miRNA detection methods employed in this study may potentially be applied in the future for the early detection of breast cancer.

Storage and retrieval of solitons in electromagnetically induced transparent system of V-type three-level diamond nitrogen-vacancy color centers

<sec>Compared with light, the solitons, which are from the balance between dispersion and nonlinearity of the system, possess high stability and fidelity as the information carries in quantum information processing and transmission, and have gained considerable attention in ultra-cold atomic electromagnetically induced transparent (EIT) media. To date, the EIT models on the three-level ultra-cold atoms realized experimentally, are ladder-, <inline-formula><tex-math id="M1">\begin{document}$\Lambda $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M1.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M1.png"/></alternatives></inline-formula>-, and V-type mode. Current studies show that the solitons cannot be stored in V-type three-level ultra-cold atomic EIT media but they can be stored in ladder- and <inline-formula><tex-math id="M2">\begin{document}$\Lambda $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M2.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M2.png"/></alternatives></inline-formula>-type three-level ultra-cold atomic EIT media. It is mainly because the atoms of the V-type system initially are in a excited state, while the atoms of the ladder- and <inline-formula><tex-math id="M3">\begin{document}$\Lambda $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M3.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M3.png"/></alternatives></inline-formula>-type systems initially are in the ground state. For the practical applications, it is a large challenge to control accurately the solitons stored in the ultra-cold atomic EIT media due to their ultralow temperature and rarefaction. Fortunately, with the maturity of semiconductor quantum technology, quantum dots have extensively application prospect in quantum information processing and transmission. However, the solitons cannot be stored in V-type three level InAs/GaAs quantum dot EIT media either, while it can be stored in ladder-type system and <inline-formula><tex-math id="M4">\begin{document}$\Lambda $\end{document}</tex-math><alternatives><graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M4.jpg"/><graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="10-20232006_M4.png"/></alternatives></inline-formula>-type system.</sec><sec>Therefore, herein we propose a V-type three-level nitrogen-vacancy (NV) center EIT model in which a weakprobe field and a strong control field are coupled to different energy levels of NV center in diamond. Subsequently, the linear and nonlinear properties of system are studied by using semiclassical theory combined with multi-scale method. It is shown that when control field is turned on, the linear absorption curve of the system presents an EIT window. And the width of the EIT window increases with the strength of magnetic induction of the control field increasing. In the nonlinear case, the solitons formed can stably propagate over a long distance. Interestingly, the solitons can be stored and retrieved by switching off and on the magnetic field of control field. Moreover, the amplitude of the stored solitons can be modulated by the magnetic induction strength of control field. This result indicates that solitons as information carriers in quantum information processing and transmission of NV center can greatly improve the fidelity of information processing.</sec>

Robust diamond-embedded microwave antenna for optimizing quantum sensing using nitrogen-vacancy center ensembles

The nitrogen-vacancy (NV) color center in diamond has emerged as a promising candidate for quantum sensing. In this study, we propose a diamond-embedded metal antenna for magnetic detection utilizing NV center ensembles. Our approach involved employing nanofabrication and microwave plasma chemical vapor deposition techniques to fabricate the metal antenna and diamond epilayer. By directly embedding the antenna into the diamond, we effectively minimize external environmental interference, leading to improved device stability and reusability. Moreover, this integration enhances the device's compactness, making it highly suitable for on-chip quantum sensing applications. The innovative antenna design holds great potential for the development of future integrated quantum sensing devices based on NV centers in diamond.

Creation of shallow nitrogen vacancy centers in HPHT diamond surface via catalytic etching of transition metal

The nitrogen vacancy (NV) color centers are a solid-state quantum system with the ability to maintain long coherence times at room temperatures. NV centers have potential applications in quantum detection, which necessitates their positioning at minimal distances from surfaces. However, the existing methods for fabricating NV centers are cumbersome, expensive, and difficult to control. This study investigates the etching mechanism of transition metals on diamond under plasma conditions and develops a method for producing shallow NV centers on the surface of high pressure and high temperature diamond. Our proposed method enables the production of shallow NV centers below the surface in the longitudinal direction, while simultaneously allowing precise control over the lateral distribution. Moreover, the operating costs associated with our technique are significantly lower than those of ion implantation and electron irradiation. This research contributes to the advancement of iron-etching diamond processing technology, and the proposed method facilitates the more portable preparation of shallow color centers in specific regions, enabling the realization of locally controllable and scalable coupled quantum systems.

Advances in Nitrogen-Vacancy color centers in diamond for magnetometry: Advantages and Challenges

Advances in Nitrogen-Vacancy color centers in diamond for magnetometry: Advantages and Challenges

Noise Suppression of Nitrogen-Vacancy Magnetometer in Lock-In Detection Method by Using Common Mode Rejection.

Nitrogen-vacancy (NV) centers in diamonds are promising solid-state magnetic sensors with potential applications in power systems, geomagnetic navigation, and diamond NV color center current transformers, in which both high bandwidth and high magnetic field resolution are required. The wide bandwidth requirement often necessitates high laser power, but this induces significant laser fluctuation noise that affects the detection magnetic field resolution severely. Therefore, enhancement of the magnetic field resolution of wide-bandwidth NV center magnetic sensors is highly important because of the reciprocal effects of the bandwidth and magnetic field resolution. In this article, we develop a common mode rejection (CMR) model to eliminate the laser noise effectively. The simulation results show that the noise level of the light-detected magnetic resonance signal is significantly reduced by a factor of 6.2 after applying the CMR technique. After optimization of the laser power and modulation frequency parameters, the optimal system bandwidth was found to be 75 Hz. Simultaneously, the system's detection magnetic field resolution was enhanced significantly, increasing from 4.49 nT/Hz1/2 to 790.8 pT/Hz1/2, which represents an improvement of nearly 5.7 times. This wide-bandwidth, high-magnetic field resolution NV color center magnetic sensor will have applications including power systems, geomagnetic navigation, and diamond NV color center current transformers.

Millimeter‐Scale Temperature Self‐Calibrated Diamond‐Based Quantum Sensor for High‐Precision Current Sensing

AbstractThe negatively charged nitrogen vacancy (NV) color center in diamond is a type of point defect, which is extensively studied as a promising high‐sensitivity solid‐state magnetic field sensor. However, its transition from research to application is still limited due to the technical challenges of an integrated physical package. Here, an integrated diamond sensor is demonstrated with the essential component on the order of mm3, which is realized by a standard microfabrication process. A microfabrication‐compatible light guiding structure is constructed, providing photon detection efficiency of 66% and thus enabling a magnetic field detection sensitivity reaching 203 pT·Hz1/2. Incorporation of the sensor device with a magnetic yoke enables high‐precision wide‐range direct‐current sensing with current isolation. A current measuring range of 0–400 A with a minimum detection limit of 2 mA is achieved. By utilizing dual spin resonance modulation, the temperature drift is suppressed from 219 to 1.92 ppm∙°C−1. This configuration provides new possibilities as a robust and scalable platform for current quantum sensing technologies.

Integrating Fluorescent Nanodiamonds into Polymeric Microstructures Fabricated by Two-Photon Polymerization.

Nitrogen-vacancy (NV) and other color centers in diamond have attracted much attention as non-photobleaching quantum emitters and quantum sensors. Since microfabrication in bulk diamonds is technically difficult, embedding nanodiamonds with color centers into designed structures is a way to integrate these quantum emitters into photonic devices. In this study, we demonstrate a method to incorporate fluorescent nanodiamonds into engineered microstructures using two-photon polymerization (2PP). We studied the optimal concentration of nanodiamonds in the photoresist to achieve structures with at least one fluorescent NV center and good structural and optical quality. Fluorescence and Raman spectroscopy measurements were used to confirm the presence and location of the nanodiamonds, while absorbance measurements assessed scattering losses at higher concentrations. Our results show the feasibility of fabricating microstructures embedded within fluorescent nanodiamonds via 2PP for photonics and quantum technology applications.

Silicon Vacancy in Boron-Doped Nanodiamonds for Optical Temperature Sensing.

Boron-doped nanodiamonds (BNDs) have recently shown a promising potential in hyperthermia and thermoablation therapy, especially in heating tumor cells. To remotely monitor eigen temperature during such operations, diamond color centers have shown a sensitive optical temperature sensing. Nitrogen-vacancy (NV) color center in diamonds have shown the best sensitivity in nanothermometry; however, spin manipulation of the NV center with green laser and microwave-frequency excitations is still a huge challenge for biological applications. Silicon-vacancy (SiV) color center in nano/bulk diamonds has shown a great potential to be a good replacement of the NV center in diamond as it can be excited and detected within the biological transparency window and its thermometry operations depends only on its zero-phonon line (ZPL) shift as a function of temperature changes. In this work, BNDs were carefully etched on smooth diamond nanocrystals' sharp edges and implanted with silicon for optical temperature sensing. Optical temperature sensing using SiV color centers in BNDs was performed over a small range of temperature within the biological temperature window (296-308 K) with an excellent sensitivity of 0.2 K in 10 s integration time. These results indicate that there are likely to be better application of more biocompatible BNDs in hyperthermia and thermoablation therapy using a biocompatible diamond color center.

A Two-Frequency Resonator for Exciting Hyperfine Transitions in a Nitrogen-Vacancy Color Center in Diamond

A Two-Frequency Resonator for Exciting Hyperfine Transitions in a Nitrogen-Vacancy Color Center in Diamond

Mitigation of nitrogen vacancy photoluminescence quenching from material integration for quantum sensing

The nitrogen-vacancy (NV) color center in diamond has demonstrated great promise in a wide range of quantum sensing. Recently, there have been a series of proposals and experiments using NV centers to detect spin noise of quantum materials near the diamond surface. This is a rich complex area of study with novel nano-magnetism and electronic behavior, that the NV center would be ideal for sensing. However, due to the electronic properties of the NV itself and its host material, getting high quality NV centers within nanometers of such systems is challenging. Band bending caused by space charges formed at the metal-semiconductor interface force the NV center into its insensitive charge states. Here, we investigate optimizing this interface by depositing thin metal films and thin insulating layers on a series of NV ensembles at different depths to characterize the impact of metal films on different ensemble depths. We find an improvement of coherence and dephasing times we attribute to ionization of other paramagnetic defects. The insulating layer of alumina between the metal and diamond provide improved photoluminescence and higher sensitivity in all modes of sensing as compared to direct contact with the metal, providing as much as a factor of 2 increase in sensitivity, decrease of integration time by a factor of 4, for NV T 1 relaxometry measurements.

Sensing of Magnetic-Field Gradients with Nanodiamonds on Optical Glass-Fiber Facets.

We demonstrate a photonic sensor of the magnetic field and its gradients with remote readout. The sensor is based on optically detected magnetic resonance (ODMR) in nanodiamonds with nitrogen-vacancy color centers that are covalently attached as a thin film on one facet of an optical fiber bundle. By measuring ODMR signals from a group of individual fibers in an ∼0.5-mm-wide imaging bundle, differences of local magnetic field strengths and magnetic field gradients are determined across the plane of the bundle facet. The measured gradients are created by direct electric currents flowing in a wire placed near the nanodiamond film. The measurement enabled the determination of the net magnetic field corresponding to various current directions and their corresponding magnetic field gradients. This demonstration opens up a perspective for compact fiber-based endoscopy, with additional avenues for remote and sensitive magnetic field detection with submicrometer spatial resolution under ambient conditions.