Microwave detection based on optical detection magnetic resonance technology (ODMR) of nitrogen-vacancy (NV) centers is simple and non-invasive. However, in high microwave power ranges, saturation appears and cannot be used for accurate power measurement. The self-coherent reference measurement for high-power microwave based on ODMR of NV centers has been demonstrated. Firstly, by introducing the principle of microwave self-coherent reference, that is, by adjusting the phase difference to achieve power regulation of microwave, a conversion model by phase modulation between enhancement and attenuation of microwave power is introduced. Then, the microwave self-coherent reference measurement is established under combinations of microwave power with different phase settings. Combined with the frequency modulation technology, the sensitivity of measurement is significantly improved from 4.59 nT/Hz1/2 to 67.69 pT/Hz1/2. The maximum measurement range of microwave power can be extended to 2×104 times the initial saturated power of direct measurement with ODMR. The results show that the method efficiently overcomes saturation under the direct measurement of ODMR and provides useful technical assistance for near-field detection, performance monitoring, and problem diagnostics for microwave devices.

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 × 10 5 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.

Nitrogen Vacancy (NV) centers in Diamond exhibits the advantages of high resolution, high sensitivity, and error-free sensing in the field of vector field detection, which bolstering the potential of NV centers magnetometers for practical applications. However, most of the NV centers magnetometers is still limited by the constraints imposed by bulky laboratory instruments, and the method of sweeping frequency points to detect resonance frequencies can also lead to slower detection of vector magnetic field (MF). To address these limitations, enhancing the portability of integrated vector magnetometers, we made an integrated vector magnetometer based on NV centers and proposed a microwave (MW) frequency-hopping method to realize vector MF triaxial real-time (400 ms) detection. The experimental results indicate that the magnetometer dynamic range is ± 130 μT along the x-axis, ± 110 μT along the y-axis, and ± 260 μT along the z-axis, with the minimum standard deviation of vector MF measurements across all three axes being 1.84 nT. The frequency-hopping method is more than 87 times faster than the sweeping method and the size of the integrated NV magnetometer fit in the palm of the hand to portable usage. This proposal, which accomplishes vector MF rapidly measure using a self-made NV centers magnetometer, has potential applications in fields such as medical diagnosis, new energy battery testing and geomagnetic detection.

Imaging of electronic device surface or sub -surface electromagnetic fields under operating conditions is important for device design and diagnosis. In this study, we proposed a method to characterize specific magnetic field properties of electromagnetic devices at micronscale using a solid-state quantum sensor, namely diamond nitrogen -vacancy (NV) centers. By employing a wide -field magnetic field measurement technique based on NV centers, we rapidly obtain the first -order magnetic field distribution of anomalous regions. Furthermore, we approximate the second -order magnetic field (magnetic gradient tensor) using the differential gradient method. To visualize the electromagnetic anomalous regions boundary, we utilize the tensor invariants of the magnetic gradient tensor components, along with their nonlinear combinations. The identification error rate of the anomalous regions is within 12.5%. Additionally, the electromagnetic field of anomalous regions is simulated showing the measurement accuracy. Our study shows that the experimental results are very similar to the theoretical simulation of the electromagnetic field (error: 7%). This work is essential for advancing electromagnetic field characterization of electronic devices and the advancement of quantum magnetic sensor applications.

Visualizing the near-field distribution of microwave field in a monopole antenna is very important for antenna design and manufacture. However, the traditional method of measuring antenna microwave near field distribution by mechanical scanning has some problems, such as long measurement time, low measurement accuracy and large system volume, which seriously limits the measurement effect of antenna microwave near field distribution. In this paper, a method of microwave near-field imaging of a monopole antenna using a nitrogen-vacancy center diamond is presented. We use the whole diamond as a probe and camera to achieve wide-field microwave imaging. Because there is no displacement structure in the system, the method has high time efficiency and good stability. Compared with the traditional measurement methods, the diamond probe has almost no effect on the measured microwave field, which realizes the accurate near-field imaging of the microwave field of the monopole antenna. This method achieves microwave near-field imaging of a monopole antenna with a diameter of 100 µm and a length of 15 mm at a field of view of 5 × 5 mm, with a spatial resolution of 3 µm and an imaging bandwidth of 2.7~3.2 GHz, and an optimal input microwave phase resolution of 0.52° at a microwave power of 0.8494 W. The results provide a new method for microwave near-field imaging and measurement of monopole antennas.

The diamond nitrogen-vacancy (NV) centers have stable spin-coherent properties at room temperature. They are easily initialized and read out, highly manipulable, and hold great promise for quantum precision measurements. In this article, we construct a magnetic flux concentration (MFC) structure combined with a quantum spin manipulated magnetometer of NV centers. This structure is further combined with a uniform spatial magnetic field gradient to achieve high-resolution microdisplacement (MD). MD measurement with and without MFC is realized using Ramsey’s principle. The sensitivity of MD measurement with MFC is 150.84 mV/mm, and the experimental test range is 105–107 mm. The resolution of MD detection has been experimentally verified to be 1.95 $\mu $ m without MFC and 49 nm with MFC. The resolution of MD detection has been improved by a factor of 39.8. The displacement shot-noise-limited sensitivity of the magnetometer can reach 0.21 nm/Hz $^{\text{1/2}}$ . The results demonstrate that utilizing quantum spin manipulation and the MFC effect enables achieving both high resolution and rapid detection of MD for NV centers in systematic diamonds. This offers a novel approach for high-resolution MD measurement.

The ensemble of nitrogen-vacancy (NV) centers is widely used in quantum information transmission, high-precision magnetic field, and temperature sensing due to their advantages of long-lived state and the ability to be pumped by optical cycling. In this study, we investigate the zero-phonon line behavior of the two charge states of NV centers by measuring the photoluminescence of the NV center at 1.6 K-300 K. The results demonstrate a positional redshift, an increase in line width, and a decrease in fluorescence intensity for the ZPL of NV0 and NV- as the temperature increased. In the range of 10 K to 140 K, the peak shift with high concentrations of NV- revealed an anomaly of bandgap reforming. The peak position undergoes a blueshift and then a redshift as temperature increases. Furthermore, the transformation between NV0 and NV- with temperature changes has been obtained in diamonds with different nitrogen concentrations. This study explored the ZPL characteristics of NV centers in various temperatures, and the findings are significant for the development of high-resolution temperature sensing and high-precision magnetic field sensing in ensemble NV centers.

The rapid tracking of magnetic target holds significant importance in biomedicine, precision instrumentation, materials science, and more. The diamond nitrogen vacancy ( NV - ) color centers exhibit magnetic field detection effect. They have shown high sensitivity, calibration-free nature, easy readout, and operability at room temperature. This paper presents an approach to rapidly induce magnetic fields based on the NV - color centers ensemble without microwave. We demonstrated the magnetic-field-dependent photoluminescence (PL) of the NV - color centers ensemble quantum system, and applied it wide-field imaging. By expanding the magnetic dipole model, we achieved rapid three-dimension (3D) tracking imaging technology of micro-sized magnetic target. Results show the NV - color centers ensemble’s high dynamic sensing capabilities for magnetic fields, providing a wide field of view (3000 μm × 3000 μm) with a time resolution of 5 ms and a magnetic detection sensitivity of 0.5 μT/√Hz. Furthermore, it eliminated the influence of microwaves and reduced the experimental equipment requirements. These findings offer a direction for rapid tracking the magnetic target based on NV - color centers ensemble.

The multilevel encoding (MLE) scheme is an effective method for improving the anticounterfeiting encryption capabilities of physically unclonable functions (PUFs). However, owing to the correlation between encoding layers, the encoding capacity (EC) is difficult to improve by orders of magnitude. Herein, four noncorrelated structures in the diamond crystal structure (carbon-carbon single bond, defect luminescence structures, spin structures, and electron energy distribution structures) are considered for MLE. First, the microdiamonds containing nitrogen-vacancy (NV) color centers are embedded into polydimethylsiloxane (PDMS) to fabricate PUFs. Using an optical imaging system, four codable images of four noncorrelated structures are read. The noncorrelation of the four-level encoding structure is verified by calculating the Hamming distance (0.496 & PLUSMN; 0.02). The results show that EC exponentially improves to 24x10 000/(100 pixels)2. Furthermore, the encoding method based on the energy level does not depend on physical structure parameters, such as the size and position of the spin structure. Thus, it is protected from structural modeling attacks, resulting in high security. Moreover, PUF labels based on PDMS flexible substrates can be employed for various flexible applications. In the proposed scheme, the information is encrypted by a four-level two-dimensional (2D) barcode and decoded by self-developed PUF authentication software. The proposed scheme presents a way for developing next-generation PUFs with super-high EC. A four-level encoding physically unclonable function (PUF) is constructed based on diamond's carbon-carbon single bond, defect luminescence structures, spin structures, and electron energy distribution structures. This PUF realizes fast authentication with encoding capacity up to 24x10 000/(100pixels)2. The PUF is independent of physical structure parameters, therefore cannot be cloned by nanofabrication. It provides new paradigms for high secure PUFs with high encoding capacity.image

Thermal crosstalk between array structures is a key factor in limiting the sensitivity of micro-nano array sensors. We propose a two-stage thermally isolated structure with thermal holes and heat dissipation layer and pulsed voltage heating to reduce thermal crosstalk. Through finite element thermal simulation analysis as well as thermal interference test, the results show that the thermal crosstalk of the two-stage structure is reduced by 12.89% and 39.67%, respectively, in the steady state compared to the structure with no thermal isolation, and pulsed voltage heating leads to the thermal crosstalk of the two-stage structure to be <10%.

The development of semiconductor technology has enabled the planarization and miniaturization of microwave sensors and it brought challenge for near-field microwave measurements at micro and nanoscale. In this article, we propose a method for detecting microwave frequency on sensing chip surface with high resolution via scanning probe microscopy and microwave detection technology. The radiated signal of microwave sensor is determined by analyzing the center frequency of the S-11 oscillation curve, and the high-precision measurement of both single-frequency and multifrequency signals is achieved over a wide operating range of frequencies (100 kHz-10 GHz), with low power (-20 dBm) and minimal error (8 Hz). Due to the simplicity, flexibility, and accuracy of frequency identification technique, the proposed method can be applied to the design, failure analysis, and performance optimization of microwave sensor at micro and nanoscale.

Multiplexing technology creates several orthogonal data channels and dimensions for high-density information encoding and is irreplaceable in large-capacity information storage, and communication, etc. The multiplexing dimensions are constructed by light attributes and spatial dimensions. However, limited by the degree of freedom of interaction between light and material structure parameters, the multiplexing dimension exploitation method is still confused. Herein, a 7D Spin-multiplexing technique is proposed. Spin structures with four independent attributes (color center type, spin axis, spatial distribution, and dipole direction) are constructed as coding basic units. Based on the four independent spin physical effects, the corresponding photoluminescence wavelength, magnetic field, microwave, and polarization are created into four orthogonal multiplexing dimensions. Combined with the 3D of space, a 7D multiplexing method is established, which possesses the highest dimension number compared with 6 dimensions in the previous study. The basic spin unit is prepared by a self-developed laser-induced manufacturing process. The free state information of spin is read out by four physical quantities. Based on the multiple dimensions, the information is highly dynamically multiplexed to enhance information storage efficiency. Moreover, the high-dynamic in situ image encryption/marking is demonstrated. It implies a new paradigm for ultra-high-capacity storage and real-time encryption.

As an anti-counterfeiting technology, physical unclonable function (PUF) is irreplaceable in addressing security risks in the Internet of Things. However, limited by the fixed structural shape, PUF security cannot be further improved. Here, we present a 5D spin-PUF with three sensing effects and two spatial parameters as encoding parameters. The free transformation of the spin state is regulated for dynamic anti-counterfeiting. Fabricated by the self-developed laser-induced technology, the 5D coding base units are composed with random crystal direction, height, and concentration of SiC nanocrystals with spin structures. Spin states are manipulated by temperature, magnetic fields, and microwaves as three additional dimensions. The number of challenge-response pairs increases exponentially to 4,097 with an encoding capacity of 1027,310,000. With an excellent Hamming distance and low autocorrelation coefficient, the recognition accuracy reaches more than 94% using DenseNet. Additionally, we demonstrate unique real-time anti-counterfeiting of product state information. It could potentially be a next-generation security strategy.

Invisible microstrip defect detection is of great significance for ensuring the reliability of integrated circuits and improving the performance of communication system. In this article, the microwave fields radiated by six typically invisible microstrip defects were experimentally characterized with high accuracy based on quantum wide-field microscope, and the origin of microwave field contrast was theoretically analyzed. In a view of 1400 x 700 m(2), the microwave near-field distribution radiated by invisible microstrip defects was reconstructed with a resolution of 1.63 mu m/pixel, and the microwave magnetic field detection sensitivity reached 0.7 nT/Hz(1/2). Meanwhile, the causes of microwave field discrepancies were analyzed specifically on the basis of microstrip transmission line theory. It was attributed to the transmission loss and the uneven distribution of induced current arising from variations in geometrical structures. The phenomenon validated the feasibility of detecting invisible microstrip defects utilizing the microwave field intensity distribution. The proposed approach is expected to have applications in microchip design and radio frequency (RF) equipment maintenance, thereby notably improving the practicability of quantum measurement technology.

This article proposed a microwave (MW) detection method by utilizing the effect of the dual MW on nitrogen-vacancy (NV) centers in diamond. We established a theoretical model of dual MW superposition and experimentally discovered the unusual peak in the optically detected magnetic resonance (ODMR) spectrum. The peak frequency and the full-width at half-maximum of the unusual peak, as well as fluorescence intensity in the nonresonant frequency range of the ODMR spectrum, were systematically analyzed to obtain the frequency and amplitude of the measured MW signals. The broadband MW detection was realized in a wide range of 2240–4512 MHz by utilizing the linear relation between the magnetic field and the resonant frequency in the Zeeman splitting. The experiments showed that the minimum detection power was up to 1 $\mu$ W. The proposed approach can greatly improve the practicability of detecting MW fields on chip surfaces by quantum engineering techniques.

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.

Non-destructive measurement of tiny magnetic structures widely found in precision instruments has been a challenging work. Nitrogen vacancy (NV) is a solid-state quantum sensor that enables fast vector magnetic imaging by optical detection. However, NV magnetic detection results lack information about magnetic anomalies in the perpendicular direction, while the dispersive magnetic field blurs the features of the magnetic source. In this article, we combine optical detection NV magnetic imaging with regularized inversion techniques and propose a dual-observation-plane detection inversion method. We study the relationship between spatial magnetization intensity and observed magnetic induction intensity, and realize 3-D inversion reconstruction of miniature magnetic structures. For the validation experiments, we chose to perform 3-D inverse reconstruction and quantitative analysis of the magnetic structures that break in the middle, which is difficult to detect by traditional methods. The inversion results achieve a spatial resolution of 40 mu m in all three directions and a model accuracy of 94.4% at 20 iterations, providing a new solution for magnetic structure detection.

The localization and tracking of tiny magnetic source hold great potential for applications in the fields of medical and scientific research. However, cross-order-of-magnitude localization using millimeter sensor is an open problem. In this article, we proposed a precise localization method for the tiny magnetic source that breaks through the limited field-of-view of the optical quantum sensor imaging. The position of the magnetic source is uniquely resolved by the construction of a magnetic gradient tensor (MGT) based on the vector magnetic field (2.7 $\times $ 2.7 mm, pixel size: $3.45~\mu \text{m}$ ) obtained by nitrogen-vacancy (NV) color centers in a diamond. A 3 mm diameter magnetic source is accurately located within a spatial range of 5 cm with a mean error of 8%. In addition, the limitations and influencing factors of the NV-MGT localization method are theoretically discussed. The results provide insight into the localization of tiny magnetic sources and extend the application of quantum sensor.

In this paper, we establish a set of schemes to generate, detect, and identify the multi-frequency magnetic field in the extremely low-frequency range. Based on the magnetic sensitivity of nitrogen-vacancy centers in diamond, the schemes adopt frequency closed-loop proportion-integration-differentiation locking and microwave modulation and demodulation to obtain magnetic field information. A set of multi-coil mutual inductance devices is used to generate a multi-frequency AC magnetic field. In the schemes, the DenseNet network structure is used to train and identify the magnetic field information, with a recognition rate of 99.16%. When the Net is used to identify noisy signals, it still maintains an average recognition rate of 95.18% for random frequency noisy signals. This generating, detecting, and identifying schemes of the multi-frequency magnetic field in the extremely low-frequency range based on quantum sensors in this paper provides a novel idea for the future application of quantum sensors in biomedicine.

Measurement of radio frequency chip microwave field is of great importance for the manufacturing of precision instruments and the development of integrated circuits. In this article, the characterization of chip surface 3-D microwave field distribution was realized with high resolution based on diamond nitrogen-vacancy (NV) centers, and the field-image separation technique was developed to suppress the stray light noise caused by the reflection of the chip. The feasibility of the proposed method was verified by characterizing the planar microwave fields at different powers and the 3-D microwave fields at different frequencies radiated by an antenna chip with a characteristic linewidth of $100~\mu \text{m}$ . The microwave field of chip radiation was accurately reconstructed with a vertical resolution of $30~\mu \text{m}$ , and the optimal NV detection sensitivity is 0.8 nT/Hz1/2. The results provide a new approach for antenna radiation detection and on-chip measurement based on quantum detection techniques.