Quantum sensing module, quantum current transformer, and current measurement method

Abstract

The present invention relates to a quantum sensing module, a quantum current transformer, and a current measurement method, wherein the quantum sensing module comprises a quantum probe (1), a laser module (2), a microwave module (3), a photoelectric detection module (4), a lock-in amplifier (5), a frequency lock module (6), and a data processing module (7). The quantum probe (1) comprises a diamond sensing unit (11) and a microwave emitter (12). The laser module (2) is configured to output an excitation laser. The microwave module (3) is configured to output a microwave signal. The photoelectric detection module (4) is arranged to receive photoluminescence generated by the diamond sensing unit (11), convert it into a voltage signal, and output it. The lock-in amplifier (5) comprises a modulation unit and a demodulation unit. The frequency lock module (6) comprises a PID control unit and a frequency acquisition unit.

Description

Technical Field

[0001] This application claims the priority of Chinese Patent Application No. 202410289213.4 filed with the Chinese Patent Office on March 14, 2024, and all the contents of the application are incorporated herein by reference.

[0002] This application relates to the technical field of quantum precise measurement, for example, to quantum sensing modules, quantum current transformers, and current measurement methods.

Background Art

[0003] In recent years, the solid spin color center system has seen rapid development in research in the field of quantum precision. In particular, in the research on detection of magnetic fields, detection methods mainly based on Optically Detected Magnetic Resonance (ODMR) have been developed. By studying the linear relationship between the magnetic resonance frequency and the external magnetic field, sensing measurement and quantification of the external magnetic field can be realized. However, some current research still focuses on the theoretical aspect, and in the process of productization of related technologies, there are still many application problems that need to be solved.

[0004] In the Chinese patent application with patent number CN113804941B, a current measurement device and measurement method based on a diamond NV color center are disclosed, which includes a laser excitation and reflected light receiving analysis device, a diamond NV color center probe, a magnetic collector, and a microwave excitation device. Its transformer includes three measurement methods: all-optical measurement method, non-all-optical measurement method, and combined measurement method. A current measurement method based on Optically Detected Magnetic Resonance (ODMR) is proposed in the aspect of this application. In this method, obtaining the magnetic resonance frequency is a difficulty in actual work.

[0005] In related technologies, methods for extracting resonance frequencies mainly include manual selection by humans and curve fitting acquisition. However, with both of these methods, when measuring different magnetic fields, the resonance frequency cannot be obtained without acquiring the ODMR frequency-swept spectral line using the frequency sweep method, resulting in a long acquisition time for the resonance frequency. Furthermore, the manual selection method has the problem of not being highly accurate and therefore unsuitable for commercialization, and the curve fitting acquisition method has the problem of the process of fitting and obtaining the derivative being complex and limiting the measurement bandwidth. [Overview of the project] [Means for solving the problem]

[0006] This application provides a quantum sensing module, a quantum current transformer, and a current measurement method for solving problems existing in related technologies.

[0007] This application is, The system comprises a diamond sensing unit and a microwave radiator, wherein the diamond sensing unit is located in the working area of ​​the microwave radiator, and includes a quantum probe containing a nitrogen-vacancy NV color center, A laser module configured to output an excitation laser positioned to irradiate the diamond sensing unit and generate photoluminescence in the diamond sensing unit, A microwave module configured to output a microwave signal that is positioned to form a microwave field using the microwave radiator and radiate it to a corresponding diamond sensing unit, A photoelectric detection module is arranged to receive the photoluminescence generated by the diamond sensing unit, convert it into a voltage signal, and output it; A lock-in amplifier comprising a modulation unit arranged to output a microwave modulation signal to the microwave module, which is arranged to modulate the microwave signal, and a demodulation unit arranged to demodulate the voltage signal and output the demodulated result, A frequency lock module comprising a proportional-integral-derivative PID control unit that takes the demodulation result as an input value and outputs a frequency adjustment parameter arranged to adjust the microwave output frequency of the microwave module, and a frequency acquisition unit arranged to read the microwave output frequency of the microwave module, The system comprises a data processing module that is connected to the frequency lock module and the lock-in amplifier for communication purposes and is arranged to perform data analysis processing on a target program. We provide quantum sensing modules.

[0008] In some embodiments of the present invention, the quantum sensing module described above comprises one transmission fiber to which the diamond sensing unit is attached in the photoconductive area of ​​one end face, or two transmission fibers that are integrally welded together and to which the diamond sensing unit is attached in the welded surface between the two.

[0009] In some embodiments of the present invention, the lock-in amplifier for the quantum sensing module described above is a two-phase digital demodulator.

[0010] Another aspect of this application is, The present invention provides a quantum current transformer comprising a quantum sensing module as described above, configured to measure current in a conductor, further comprising a conductor passage, with an external magnetic shield provided outside the conductor passage, and the diamond sensing unit being mounted in a virtual annular ring between the conductor passage and the external magnetic shield.

[0011] In some embodiments of the present invention, the quantum current transformer comprises a plurality of quantum sensing modules, and all diamond sensing units are arranged to be equally spaced in the virtual annular ring.

[0012] In some embodiments of the present invention, the quantum current transformer described above is a diamond grain containing an ensemble NV color center, and the tangents corresponding to the points where the diamond grains are located in the virtual annular ring are such that the magnitude of the angle between the tangents and the axial directions of the four color centers of the diamond sensing unit is equal or not equal to any of them.

[0013] In some embodiments of the present invention, the quantum current transformer described above is further equipped with a magnetic collector in which the diamond sensing unit is placed in the magnetic air gap.

[0014] In some embodiments of the present invention, when the quantum current transformer is equipped with a plurality of quantum sensing modules, the number of quantum sensing modules is 4n, where n is a positive integer.

[0015] In some embodiments of the present invention, an internal magnetic shield is further provided outside the conductor passage of the quantum current transformer described above, and the diamond sensing unit is located outside the internal magnetic shield.

[0016] In some embodiments of the present invention, the quantum current transformer described above further comprises a bias magnetic source arranged to enable the application of a bias magnetic field at any angle to the diamond sensing unit.

[0017] In some embodiments of the present invention, the quantum current transformer described above further comprises a primary ring in which the conductor passage is located within its inner bore, and both the outer magnetic shield and the diamond sensing unit are located within its inner chamber.

[0018] In some embodiments of the present invention, the quantum current transformer described above further comprises a conducting rod whose central axis coincides with the central axis of the bore of the primary ring and intersects perpendicularly with respect to the center of the virtual annular ring.

[0019] In some embodiments of the present invention, the quantum current transformer described above is further provided with an insulator having the primary ring attached to its tip and a cable passage provided inside that penetrates its upper and lower sides.

[0020] Another aspect of this invention is its application to quantum current transformers as described above. The microwave module is controlled to output a frequency-swept microwave signal, the ODMR spectral line of the quantum probe is drawn based on the frequency-swept microwave signal, the microwave resonance frequency at the magnetic resonance feature point in the ODMR spectral line is obtained, and the initial parameter acquisition is recorded as the initial microwave frequency. The present invention further provides a current measurement method that includes controlling the microwave module to output a single-frequency microwave signal at the initial microwave frequency, having a lock-in amplifier output a frequency modulation signal to modulate the single-frequency microwave signal, activating the quantum current transformer based on the single-frequency microwave signal to perform photodetection magnetic resonance detection, the quantum current transformer measuring the magnetic field generated by the current-carrying conductor under test and obtaining a demodulation result, a PID control unit performing feedback adjustment to the microwave module according to the demodulation result and target value to switch the microwave output frequency of the microwave module to a usable resonance frequency representing the magnetic field generated by the current-carrying conductor under test, a frequency acquisition unit capturing the usable resonance frequency and transmitting it to a data processing module, and the data processing module analyzing and processing the usable resonance frequency to obtain current information in the current-carrying conductor under test.

[0021] Regarding the current measurement method as described above, in some embodiments of the present application, obtaining the demodulation result as described above includes controlling the optoelectronic detection module to output a voltage signal representing the magnetic field generated by the measured current-carrying conductor, demodulating the voltage signal by a two-phase digital demodulation method to obtain the demodulation result, adjusting the phase to make one of the demodulated binary component values a value near zero, comparing the other component value with the target value as the input value of the PID control unit, and outputting a frequency adjustment parameter for adjusting the microwave module.

[0022] Regarding the current measurement method as described above, in some embodiments of the present application, the quantum current transformer further includes a phase automatic adjustment module configured to automatically adjust the initial phase of the lock-in amplifier according to a set target.

[0023] Regarding the current measurement method as described above, in some embodiments of the present application, the quantum current transformer further includes a feature point automatic acquisition module configured to automatically identify the magnetic resonance feature points on the ODMR spectral line and obtain the corresponding microwave resonance frequencies at the magnetic resonance feature points.

Brief Description of the Drawings

[0024] To describe the embodiments of the present application, the drawings necessary for use in the following description of the embodiments are introduced below. The drawings described below are some embodiments of the present application. Those skilled in the art can obtain other drawings according to these drawings on the premise of not paying creative labor.

[0025] [Figure 1] It is a system schematic diagram of the quantum sensing module in Embodiment 1. [Figure 2] It is an ODMR spectral line plotted with the demodulated R value as the vertical coordinate. [Figure 3] It is an ODMR spectral line plotted with the demodulated component value of the Y term as the vertical coordinate. [Figure 4]This is a schematic diagram of the structure of the quantum sensing module in Example 1. [Figure 5] This is a schematic diagram of the quantum probe structure in Example 1. [Figure 6] This is another schematic diagram of the quantum probe structure in Example 1. [Figure 7] This is a schematic diagram of the structure of a quantum current transformer equipped with a single quantum sensing module in Example 2. [Figure 8] This is another schematic diagram of the quantum current transformer equipped with four quantum sensing modules in Example 2. [Figure 9] This is a schematic diagram illustrating the application of magnetizers to four quantum sensing modules in Example 2. [Figure 10] This is a schematic diagram of the combination of the primary ring and the conducting rod in Example 2. [Modes for carrying out the invention]

[0026] The embodiments described below with reference to the drawings are illustrative and intended for interpretation purposes only.

[0027] Here, one or more embodiments are described with reference to the drawings, and similar reference numerals throughout the text are used to refer to similar components. In the following description, many details are provided to give a more thorough understanding of one or more embodiments. However, in various cases, one or more embodiments can be practiced without these details, and each embodiment can be combined and referenced to one another under consistent assumptions.

[0028] Furthermore, the terms "First," "Second," etc., in the specification, claims, and drawings of this application do not need to be used to describe a specific order or sequence, but are intended to distinguish similar subjects. The data used in this manner is replaceable where appropriate, and it should be understood that the embodiments of this application described herein can be carried out in an order other than that illustrated or described herein. Also, the terms "includes" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units listed, and may include other steps or units that are not listed or are specific to those processes, methods, products, or apparatus.

[0029] NV (nitrogen-vacancy) color centers in diamond are common defects, consisting of one nitrogen atom and an adjacent vacancy (i.e., a missing carbon atom). This structure introduces an unpaired electron into the diamond, giving the NV color center paramagnetism. Furthermore, NV color centers can generate photoluminescence upon light irradiation, making them of significant importance in the optical and electronic applications of diamond. The formation of NV color centers in diamond usually requires a specific treatment, such as introducing a nitrogen atom into the diamond lattice by ion implantation or electron beam irradiation, and then bonding the nitrogen atom with the adjacent vacancy through high-temperature annealing to form the NV color center. Other impurities and defects in diamond can also affect the properties of NV color centers, thus requiring high purity and crystal quality of the diamond.

[0030] NV color centers possess excellent photoluminescence and paramagnetism, making them promising for applications in fields such as biomarkers, quantum information, and magnetic imaging. For example, NV color centers may be used as photoluminescent markers for imaging and detection of cells and tissues, or as qubits for quantum computing and quantum communication. Furthermore, the paramagnetism of NV color centers allows for the development of magnetic imaging and magnetic sensors.

[0031] When a diamond contains a large number of NV color centers (i.e., ensemble NV color centers), due to the unique properties of the diamond lattice, the randomly oriented NV color centers have an axial direction determined by four angled angles, and in this case, the diamond ensemble NV color centers possess vector detection capabilities as sensing units.

[0032] The key to optically detected magnetic resonance (ODMR) lies in detecting the magnetic resonance signal with optical sensitivity and high resolution. In an experiment using optically detected magnetic resonance with a diamond NV color center, it is first necessary to place the diamond NV color center in an applied magnetic field so that the magnetic moments of the atomic nuclei or electrons in the diamond NV color center can interact with the applied magnetic field. Then, by emitting microwaves of a specific frequency onto the sample, energy level transitions are induced in the atomic nuclei or electrons in the diamond NV color center. Due to these energy level transitions, the diamond NV color center absorbs or emits electromagnetic radiation of a specific frequency, forming a magnetic resonance signal. This magnetic resonance signal can then be detected using optical techniques, and quantum sensing measurements can be realized by localizing and converting between the magnetic resonance signal and physical quantities such as the magnetic field.

[0033] So-called ODMR spectral lines are generally detection curves plotted by performing optical magnetic resonance (OCR) measurements using the frequency sweep method (these curves are further divided into two types: modulated and unmodulated. The points where the magnetic resonance frequencies are located on the curve are also called magnetic resonance feature points. In modulated ODMR spectral lines, the magnetic resonance feature points are zero-crossing points, while in unmodulated ODMR spectral lines, the magnetic resonance feature points are the peak points of the resonance peaks). Because the frequency sweep method uses frequency-swept microwaves, the spectral line plotting time is long, which is disadvantageous for quickly extracting feature values ​​and performing magnetic field calculations.

[0034] [Example 1] Referring to Figure 1, this embodiment discloses a quantum sensing module comprising a quantum probe, a laser module, a microwave module, a photoelectric detection module, a lock-in amplifier, a frequency lock module, and a data processing module.

[0035] In this example, the quantum probe comprises a diamond sensing unit and a microwave radiator, the diamond sensing unit being located in the working area of ​​the microwave radiator, and the diamond sensing unit containing NV color centers. In some examples, the microwave radiator may be a microstrip antenna or a spiral copper wire, and the diamond sensing unit is a diamond grain containing an ensemble of NV color centers.

[0036] In this example, the laser module is configured to output an excitation laser, which is positioned to irradiate the diamond sensing unit and generate photoluminescence. In some examples, the wavelength of the excitation laser output from the laser module is 532 nanometers (nm), and irradiation with this laser causes the diamond sensing unit to generate red photoluminescence.

[0037] In this example, the microwave module is configured to output a microwave signal, which is arranged to be radiated by the microwave radiator to form a microwave field and be directed to a corresponding diamond sensing unit. In some examples, the microwave module comprises a microwave source, a microwave amplifier, and a microwave circulator, where the microwave source is the source of the microwave signal, the microwave amplifier can amplify the microwave power, and the microwave circulator can prevent the transmission of the microwave signal in the reverse direction.

[0038] In this example, the photoelectric detection module is configured to receive the photoluminescence generated by the diamond sensing unit, convert it into a voltage signal, and output it. In some examples, the photoelectric detection module includes a photodiode (e.g., an avalanche diode) and a filtering structure (e.g., a filter), and the photoluminescence irradiated onto the photodiode must be filtered out of stray light by the filtering structure beforehand.

[0039] In this example, the lock-in amplifier comprises a modulation unit and a demodulation unit, wherein the modulation unit is configured to output a microwave modulated signal to the microwave module, and the demodulation unit is configured to demodulate the voltage signal and output the demodulated result. In some examples, the lock-in amplifier is a two-phase digital demodulator.

[0040] In some embodiments, the microwave modulation signal is arranged to modulate the microwave signal (including, for example, frequency modulation or amplitude modulation).

[0041] In this example, the frequency lock module comprises a Proportion-Integration-Differentiation (PID) control unit and a frequency acquisition unit. The PID control unit is configured to output a frequency adjustment parameter using the demodulation result as an input value. The frequency adjustment parameter is configured to adjust the microwave output frequency of the microwave module. The frequency acquisition unit is configured to read the microwave output frequency of the microwave module. The PID control unit has one input value and one target value. By comparing the two, it can output a feedback adjustment parameter to change the input value until the input value is equal to or close to the target value. In this example, the demodulation result output by the lock-in amplifier can be used as the input value of the PID control unit.

[0042] In some embodiments, the data processing module is connected to a frequency lock module and a lock-in amplifier, and is configured to perform data analysis processing on a target program. The target program is a program that implements a specific function or algorithm. The target program can be configured according to the actual data processing requirements.

[0043] In this example, the data processing module is configured to perform data analysis processing. For example, the data processing module is installed in a higher-level machine and contains at least a program method for performing magnetic field calculations based on microwave resonance frequencies, and a functional module for plotting ODMR spectral lines.

[0044] To facilitate understanding of the operation of the PID control unit in this embodiment, we interpret it illustratively here. When photodetection magnetic resonance measurement is performed on a diamond NV color center using frequency-swept microwaves, the output photoluminescence is measured, converted into a voltage signal by a photoelectric detection module, output to a lock-in amplifier, and demodulated using two-phase digital demodulation (the microwave modulated signal is set to a frequency modulated signal). After obtaining the demodulation result (demodulated value R value, demodulated X term component value, demodulated Y term component value, and phase value), and constructing ODMR spectral lines with different demodulation results and microwave frequencies as the y-coordinate and y-coordinate, respectively, spectral lines like those shown in Figure 2 (drawn with the demodulated value R value as the y-coordinate) or Figure 3 (drawn with the demodulated Y term component value as the y-coordinate) are obtained. By analyzing the spectral lines, it was found that since all magnetic resonance feature points are zero-crossing points, the microwave resonance frequency in the current magnetic field (i.e., the y-coordinate at the zero-crossing point) can be traced simply by setting the y-coordinate to zero when switching magnetic fields. Setting the target value of the PID control unit to 0 enables rapid locking to the microwave resonance frequency (rapid switching from the microwave resonance frequency of the previous magnetic field to the microwave resonance frequency of the next magnetic field). This method of acquiring the microwave resonance frequency eliminates the need to draw ODMR spectral lines by sweeping the frequency over a wide range, greatly improving the speed of microwave resonance frequency acquisition and thus improving magnetic measurement efficiency.

[0045] Here, we introduce the configuration design of an exemplary quantum sensing module, as shown in Figure 4. It comprises a quantum probe 1, a laser module 2, a microwave module 3, a photoelectric detection module 4, a lock-in amplifier 5, a frequency lock module 6, and a data processing module 7. Of these, the quantum probe 1 comprises a diamond sensing unit 11 and a microwave radiator 12, the laser module 2 comprises a 532nm laser device 21 and an optical modulator 22, the microwave module 3 comprises a microwave source 31, a microwave amplifier 32, and a microwave circulator 33, and the photoelectric detection module 4 comprises a photodiode 41, a filter 42, and a dichroic mirror 43. The connection method of these devices is as shown in the figure (the structure should further include several essential basic connectors, such as optical fibers, optical fiber couplers, and electrical signal transmission cables). Based on the connection method of these devices, the following work process is formed.The laser device 21 is activated and generates a 532nm laser. After being modulated by the optical modulator 22, the laser is reflected by the dichroic mirror 43 (a dichroic mirror that transmits red light and reflects blue light), coupled to an optical fiber, and transmitted to the diamond sensing unit 11. The microwave source 31 outputs a microwave signal, which is then transmitted sequentially through the microwave amplifier 32 and microwave circulator 33, and finally via a radio frequency transmission line to the microwave radiator 12. The microwave radiator 12 radiates the microwave signal to the diamond sensing unit 11 in the form of a field. Due to the dual action of microwaves and lasers, the diamond sensing unit 11 detects red light. Photoluminescence is generated, which travels back along the path, passes through the dichroic mirror 43, is filtered out by the filter 42 to remove stray light, and is then received by the photodiode 41 to form an electrical signal. This electrical signal is transmitted to the lock-in amplifier 5 for demodulation (the lock-in amplifier 5 further performs microwave modulation on the microwave source 31). The demodulated result is transmitted to the frequency lock module 6, and once the external magnetic field is converted, the frequency lock module 6 can immediately and quickly lock the corresponding microwave resonance frequency. The data processing module 7 then performs subsequent processing on the microwave resonance frequency to obtain the physical quantity to be measured.

[0046] For the quantum probe mentioned in Example 1, the methods for laser excitation of the diamond sensing unit 11 and photoluminescence collection vary. In some examples, as shown in Figure 5, the quantum probe 1 comprises one transmission fiber 13 (i.e., input / output optical fiber), and the diamond sensing unit 11 is attached to the photoconductive area on one end face of the transmission fiber 13. In such a structure, both the excitation laser for exciting the diamond sensing unit 11 and the photoluminescence generated by the diamond sensing unit 11 are transmitted through the same transmission fiber 13, and the light excitation and collection processes are both realized at the same end. Alternatively, as shown in Figure 6, the quantum probe 1 comprises two transmission fibers 13, and the two transmission fibers 13 are welded together. The diamond sensing unit 11 is attached to the welded surface between the two transmission fibers 13. In such a structure, the excitation laser is transmitted from one side of the transmission fiber 13 to the diamond sensing unit 11, and the photoluminescence is transmitted from the other side of the transmission fiber 13 to the photoelectric detection module 4.

[0047] In some examples, the lock-in amplifier is a two-phase digital demodulator. The demodulated result obtained by demodulation by the two-phase digital demodulator includes the demodulated value R, the component value of the demodulated X term, the component value of the demodulated Y term, and the phase value. In some examples, an automatic phase adjustment module is further provided, which is configured to automatically adjust the initial phase of the lock-in amplifier according to a set target. If modulation and demodulation are performed using a two-phase digital lock-in amplifier, and it is desired that the plotted ODMR spectral line is as shown in Figure 3 (plotted with the component value of the demodulated Y term as the y-coordinate), then it is necessary to adjust the initial phase to obtain more accurate measurement needs (i.e., the phase adjustment needs to bring the component value of the demodulated X term close to zero). For example, the initial phase is continuously adjusted manually, and it is observed whether the component value of one of the terms satisfies the set target. Since this manual adjustment process is not well automated, it is designed to be automated with a software program. In one example, the target setting may be that the component value of the demodulated X term or the component value of the demodulated Y term is equal to zero or near zero (i.e., a value near zero). Based on this target setting, the software program can complete a closed loop by continuously correcting the initial phase and determining whether the target setting has been achieved, and the programming of such a program is simple.

[0048] In Example 1, it is possible to measure a magnetic field, and considering the conversion relationship between electricity and magnetism, the present invention further provides Example 2 for measuring electric current.

[0049] [Example 2] As shown in Figure 7, this embodiment discloses a quantum current transformer configured to measure current in a conductor, comprising one or more quantum sensing modules as described in Embodiment 1 (for ease of demonstration, the structure of the quantum sensing module included in Figure 7 corresponds to the structure shown in Figure 4, but it should be understood that the structure of the quantum sensing module in this embodiment is not limited thereto), further comprising a conductor passage 8, an external magnetic shield 9 provided outside the conductor passage 8, and the diamond sensing unit 11 mounted in a virtual annular ring between the conductor passage 8 and the external magnetic shield 9.

[0050] As shown in Figure 8, when the quantum current transformer comprises multiple quantum sensing modules, all diamond sensing units 11 are arranged to be equally spaced and distributed within the virtual annular ring.

[0051] In one embodiment, when the quantum current transformer comprises a plurality of quantum sensing modules, each quantum sensing module comprises a quantum probe 1, and each quantum probe 1 comprises a diamond sensing unit 11 and a microwave radiator 12, so the number of diamond sensing units 11 is correspondingly multiple. When there are multiple diamond sensing units 11, all diamond sensing units 11 are arranged to be equally spaced in the virtual annular ring. As shown in Figure 8, four diamond sensing units 11 are arranged to be equally spaced in the virtual annular ring.

[0052] Considering the mechanism for suppressing loop integrals against noise in magnetic measurements, in one embodiment, when a quantum current transformer is equipped with multiple quantum sensing modules, the number of quantum sensing modules is 4n, where n is a positive integer. For example, n can be 1 or 2. In such a case, the magnetic field information measured by the multiple quantum sensing modules is added and averaged to achieve a good external magnetic field rejection effect, improving the accuracy of current measurement.

[0053] In some embodiments, the diamond sensing unit used in the quantum current transformer is a diamond grain containing ensemble NV color centers, which can generate a stronger photoluminescence excitation effect and is advantageous for acquiring photoluminescence data. The ensemble NV color centers have four different axial directions, and when reflected in the ODMR spectral line based on the interaction between the magnetic field in different directions and the axial directions of the four different NV color centers, multiple types of peak shapes (2 peaks, 4 peaks, 6 peaks, or 8 peaks) are formed.

[0054] Two-peak ODMR spectral lines are ideal for situations where locking is difficult, speed is high, and rapid acquisition of current measurement results is required, due to the small number of peaks and the correspondingly small number of microwave resonance frequencies that need to be locked and tracked. In some examples, the tangents corresponding to the points where the diamond grains are located in the aforementioned virtual annular ring may be such that the magnitude of the angle between the tangents and the axial directions of the four color centers of the diamond sensing unit matches, in which case two-peak ODMR spectral lines are generated.

[0055] For the 8-peak ODMR spectral line, vector measurements with respect to the magnetic field can be achieved based on the relationship between the multi-directional axes and the magnetic field components. In such cases, although there are many microwave resonance frequencies that need to be locked and tracked, the current results of the vector measurement can well satisfy several detection needs. In some other examples, the tangents corresponding to the points where the diamond grains are located in the aforementioned virtual annular ring are all set to different angles with respect to the axes of the four color centers of the diamond sensing unit, and in this case, an 8-peak ODMR spectral line is generated.

[0056] Considering the complexity of the current sensing environment, for example, in low-current scenarios (where the difference in magnitude between the magnetic field generated by the current-carrying conductor and the disturbing magnetic field is not large), in order to improve the accuracy of current measurement, in some embodiments, as shown in Figure 9 (for four quantum probes), a magnetic collector 111 is further added to the quantum current transformer, and the diamond sensing unit 11 is placed in the magnetic collection air gap 112 of the magnetic collector 111. The magnetic field generated by the current-carrying conductor under measurement is amplified by the magnetic collector 111, and the proportion of the effect of the external magnetic field is weakened, thereby improving the accuracy of current measurement.

[0057] To improve the device's ability to suppress interference from external magnetic fields, in some embodiments, an internal magnetic shield 91 is further provided, as shown in Figure 7, and the diamond sensing unit 11 is located outside the internal magnetic shield 91. The combined design of the internal magnetic shield 91 and the external magnetic shield 9 further enhances the device's noise reduction capability.

[0058] In some scenarios, it is necessary to provide some additional magnetic fields to complete initial adjustment tests or corresponding tests for the quantum current transformer, and in some embodiments, the quantum current transformer is further provided with a bias magnetic source, which is positioned to apply a bias magnetic field of any angle to the diamond sensing unit, and the bias magnetic source may be a permanent magnet or an energizing coil.

[0059] From consideration of several practical applications, as shown in Figures 7 and 8, the quantum current transformer further comprises a primary ring 10, the conductor passage 8 is located within the bore of the primary ring 10, and the external magnetic shield 9 and diamond sensing unit 11 are both located within the interior of the primary ring 10, so that the primary ring 10 is advantageous for mounting several front-end devices while also providing good protection. In some embodiments, as shown in Figure 10, the quantum current transformer further comprises a conductor rod 101, the central axis of the conductor rod 101 coincides with the central axis of the bore of the primary ring 10 and intersects perpendicularly with the center of the virtual annular ring, meaning that each quantum probe 1 is at the same distance to the conductor rod 101, thus ensuring consistency in measuring the magnetic field of the conductor. In some embodiments, the primary ring 10 is attached to the tip of an insulator, and a cable passage is provided within the insulator, penetrating its upper and lower sides, and the cable passage is configured to accommodate transmission materials such as optical fibers and electric wires.

[0060] In another respect, this paper further proposes a current measurement method applicable to the aforementioned quantum current transformer, the method comprising the steps of initial parameter acquisition and conductor current measurement, of which, In the initial parameter acquisition step, the microwave module is controlled to output a frequency-swept microwave signal, the ODMR spectral line of the quantum probe is plotted based on the frequency-swept microwave signal, the microwave resonance frequency at the magnetic resonance feature point in the ODMR spectral line is obtained and recorded as the initial microwave frequency. In the initial parameter acquisition step, the diamond sensing unit outputs photoluminescence through the dual action of a frequency-swept microwave signal and a laser signal and provides feedback. By processing the detected signal and creating a graph, the target ODMR spectral line can be acquired. There may generally be two types of target ODMR spectral lines: one where the magnetic resonance feature point is a zero-crossing point (frequency-swept microwave is modulated), and another where the magnetic resonance feature point is a peak point (frequency-swept microwave is not modulated). In this step, the PID control unit has not yet started operating, and after the frequency-swept ODMR spectral line is obtained, the microwave resonance frequency can be acquired by manual selection. Of course, it is also possible to set a software program to automatically acquire the microwave resonance frequency. In such a case, the quantum current transformer further includes an automatic feature point acquisition module, which is configured to automatically identify the magnetic resonance feature point in the ODMR spectral line and acquire the corresponding microwave resonance frequency at the magnetic resonance feature point.

[0061] Analysis based on the ODMR spectral lines under frequency modulation revealed that the microwave resonance frequencies of any given magnetic field all fall within the horizontal coordinate of the zero-crossing point in the ODMR spectral lines under frequency modulation. Therefore, by setting the lock condition based on the zero-crossing point, the microwave resonance frequency of the next magnetic field can be quickly locked. Of course, the prerequisite is that there should be one starting point microwave resonance frequency that fits the current diamond sensing unit, which is the actual function of the initial parameter acquisition step.

[0062] In the step of measuring conductor current, the microwave module is controlled to output a single-frequency microwave signal at an initial microwave frequency, a lock-in amplifier outputs a frequency modulation signal to modulate the single-frequency microwave signal, a quantum current transformer is activated based on the single-frequency microwave signal to perform the photodetection magnetic resonance detection process, the quantum current transformer measures the magnetic field generated by the current-carrying conductor under test and obtains the demodulation result, the PID control unit performs feedback adjustment to the microwave module according to the demodulation result and target value to switch its microwave output frequency to a usable resonance frequency representing the magnetic field generated by the current-carrying conductor under test, the frequency acquisition unit captures the usable resonance frequency and transmits it to the data processing module, and the data processing module analyzes and processes the usable resonance frequency to obtain current information in the current-carrying conductor under test.

[0063] When measuring the current in a conductor, it is no longer necessary to use frequency-swept microwaves. Instead, a single-frequency microwave signal (i.e., the initial microwave frequency acquired in the aforementioned step) is directly combined with the laser signal. The PID control unit tracks the initial single-frequency microwave signal, and as the external magnetic field changes, it can achieve rapid locking to the microwave resonance frequency, further enabling a rapid measurement of the current.

[0064] In the current measurement method described above, it was proposed to obtain frequency adjustment parameters by comparing the demodulated result with target data. Regarding the demodulated result, the format of expression of the demodulated result differs depending on the demodulation method. For example, in the case of single-phase demodulation, the demodulated result includes only the demodulated value R (non-negative), while in the case of two-phase demodulation, the demodulated result includes the demodulated value R (non-negative), the component value of the demodulated X term, the component value of the demodulated Y term, and the phase value.

[0065] The ODMR spectral line constructed with the demodulated R value and microwave frequency is shown in Figure 2. By comparing the demodulated R value with the target value as the input value to the PID control unit, the spectral line can be analyzed. When the magnetic field switches, the new magnetic resonance feature point is the zero-crossing point in the figure (the zero-crossing point is the target locked by the PID control unit, and therefore, the target value is generally set to 0), and the magnetic resonance feature point of the previous magnetic field is point A (or point B). To achieve the movement of the magnetic resonance feature point from point A (or point B) to the zero-crossing point, one frequency adjustment parameter needs to be provided. If the magnetic resonance feature point is at point A, a positive frequency adjustment parameter needs to be set to increase the frequency of the microwave signal, and if the magnetic resonance feature point is at point B, a negative frequency adjustment parameter needs to be set to decrease the frequency of the microwave signal. Therefore, when outputting the frequency adjustment parameter, it is necessary to further determine the direction of the feedback adjustment. A typical solution involves randomly applying a positive (or negative) frequency adjustment parameter, then determining whether the demodulated result after adjustment approaches zero. If yes, the positive (or negative) frequency adjustment parameter is continued until the frequency locking process is complete; if no, the negative (or positive) frequency adjustment parameter is applied to adjust the frequency. This frequency adjustment method requires determining the direction of adjustment, resulting in a long adjustment time and bandwidth limitations (taking Figure 2 as an example, only the portion between the two peaks can perform the adjustment steps described above).

[0066] As mentioned earlier, the need to consider direction during feedback adjustment of the microwave signal further reduces the speed of frequency locking, affecting the overall measurement speed of the instrument.

[0067] To improve the feedback adjustment efficiency of the PID control unit, the following exemplary design is proposed: In the step of measuring conductor current, the photoelectric detection module is controlled to output a voltage signal representing the magnetic field generated by the current-carrying conductor under test, and the voltage signal is demodulated using a two-phase digital demodulation method. By adjusting the phase, one of the two demodulated component values ​​is set to a value near zero, and the other component value is compared with the target value as the input value to the PID control unit to output the frequency adjustment parameter for the microwave signal.

[0068] In an exemplary embodiment, a two-phase digital lock-in amplifier is used to demodulate a voltage signal by a two-phase digital demodulation method, and the output demodulated result includes the demodulated value R value, the component value of the demodulated X term, the component value of the demodulated Y term, and the phase value. Phase adjustment (meaning the phase of the frequency-modulated signal or reference signal) is performed on the two-phase digital lock-in amplifier, the component value of the demodulated X term (or the component value of the demodulated Y term) is set to zero, the component value of the demodulated Y term (or the component value of the demodulated X term) is used as the input value to a PID control unit, a target value is set, and the frequency adjustment parameter is output by comparing the input value and the target value to adjust the microwave signal output from the microwave source.

[0069] The component value of the demodulated X term is set to zero, the component value of the demodulated Y term is used as the input value of the PID control unit, and the target value is set to 0. In this case, an ODMR spectral line is constructed using the component value of the demodulated Y term and the microwave frequency. As shown in Figure 3, when the magnetic field is transformed, the new magnetic resonance feature point is the zero-crossing point in the figure (the zero-crossing point is the target locked by the PID control unit, and if the demodulation result is equal to 0, it means that it is a magnetic resonance feature point, and therefore, the target value is generally set to 0), and the magnetic resonance feature point of the previous magnetic field is point A (or point B), and the magnetic resonance feature point To achieve the transition from point A (or point B) to the zero-crossing point, it is necessary to provide a single frequency adjustment parameter. By analyzing the spectral lines shown in Figure 3, it was discovered that there is a positive and negative distinction before and after the zero-crossing point for the component value of the demodulated Y term. Therefore, if the component value of the demodulated Y term is greater than 0, the microwave signal frequency should be decreased, and vice versa. This feedback adjustment method is faster, effectively reducing the adjustment time of the PID control unit, improving the overall measurement speed of the quantum current transformer equipment, and providing a wider measurement bandwidth.

[0070] In the embodiment described above, it is proposed that by adjusting the initial phase, one of the two demodulated component values ​​may be set to a value near zero, and the value near zero may be 0, but may fluctuate slightly above or below 0 (the fluctuation range can be limited to less than 10% of the range of the component value). For example, the initial phase can be manually adjusted, and whether or not the selected component value on the phase lock is zero can be observed in real time. Of course, automated phase adjustment can also be achieved by designing a software program. In such a case, the quantum current transformer further comprises an automatic phase adjustment module, which is configured to automatically adjust the initial phase of the lock-in amplifier according to a set target.

[0071] In some embodiments, this embodiment eliminates the need to draw ODMR frequency sweep spectral lines each time a magnetic field is measured, and by comparing target data with demodulated results, it is possible to quickly track the changed magnetic resonance frequency, drastically reduce the time required to acquire the new magnetic resonance frequency, and increase the measurement speed of the quantum current transformer.

[0072] In this specification, the terms “an embodiment,” “an example,” and “a specific example” mean that the specific features, structure, material, or property described in relation to such embodiment or example are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example.

Claims

1. The system comprises a diamond sensing unit and a microwave radiator, wherein the diamond sensing unit is located in the working area of ​​the microwave radiator, and includes a quantum probe containing a nitrogen-vacancy NV color center, A laser module configured to output an excitation laser positioned to irradiate the diamond sensing unit and generate photoluminescence in the diamond sensing unit, A microwave module configured to output a microwave signal that is positioned to form a microwave field using the microwave radiator and radiate it to a corresponding diamond sensing unit, A photoelectric detection module is arranged to receive the photoluminescence generated by the diamond sensing unit, convert it into a voltage signal, and output it; A lock-in amplifier comprising a modulation unit arranged to output a microwave modulation signal to the microwave module, which is arranged to modulate the microwave signal, and a demodulation unit arranged to demodulate the voltage signal and output the demodulated result, A frequency lock module comprising a proportional-integral-derivative PID control unit that takes the demodulation result as an input value and outputs frequency adjustment parameters arranged to adjust the microwave output frequency of the microwave module, and a frequency acquisition unit arranged to read the microwave output frequency of the microwave module, The system comprises a data processing module that is connected to the frequency lock module and the lock-in amplifier for communication purposes and is arranged to perform data analysis processing on a target program. Quantum sensing module.

2. The aforementioned quantum probe is The transmission fiber comprises one end face with a diamond sensing unit attached to the optical conduction area of ​​one end face, Alternatively, it comprises two transmission fibers that are integrally welded together, with the diamond sensing unit attached to the welded surface between the two. The quantum sensing module according to claim 1.

3. The aforementioned lock-in amplifier is a two-phase digital demodulator. The quantum sensing module according to claim 1.

4. A quantum sensing module configured to measure current in a conductor, comprising one or more quantum sensing modules according to any one of claims 1 to 3, further comprising a conductor passage, an external magnetic shield provided outside the conductor passage, and the diamond sensing unit mounted on a virtual annular ring between the conductor passage and the external magnetic shield, Quantum current transformer.

5. The system comprises multiple quantum sensing modules, and all diamond sensing units are arranged to be equally spaced in the virtual annular ring. The quantum current transformer according to claim 4.

6. The diamond sensing unit is a diamond grain containing an ensemble NV color center, and the tangent corresponding to the point where the diamond grain is located in the virtual annular ring has a magnitude of the angle between it and the axial direction of the four color centers of the diamond sensing unit, or none of them are equal. The quantum current transformer according to claim 4.

7. The magnetic collector further comprises a magnetic collector in which the diamond sensing unit is placed in the magnetic air gap. The quantum current transformer according to claim 4.

8. The number of quantum sensing modules is 4n, where n is a positive integer. The quantum current transformer according to claim 5.

9. An internal magnetic shield is further provided outside the conductor passage, and the diamond sensing unit is located outside the internal magnetic shield. The quantum current transformer according to claim 4.

10. The diamond sensing unit further comprises a bias magnetic source positioned to apply a bias magnetic field at an arbitrary angle. The quantum current transformer according to claim 4.

11. The conductor passage is located within its inner bore, and the primary ring further comprises the outer magnetic shield and the diamond sensing unit, both located within its inner chamber. The quantum current transformer according to claim 4.

12. The present invention further comprises a conducting rod whose central axis coincides with the central axis of the inner bore of the primary ring and which intersects perpendicularly with respect to the center of the virtual annular ring. The quantum current transformer according to claim 11.

13. The device further comprises an insulator to which the primary ring is attached at the tip, and which has cable passages provided inside that penetrate its upper and lower sides. The quantum current transformer according to claim 11.

14. Applied to the quantum current transformer described in claim 4, The microwave module is controlled to output a frequency-swept microwave signal, the photodetector magnetic resonance (ODMR) spectral line of a quantum probe is drawn based on the frequency-swept microwave signal, the microwave resonance frequency at the magnetic resonance feature point in the ODMR spectral line is obtained, and the initial parameter acquisition is recorded as the initial microwave frequency. The microwave module is controlled to output a single-frequency microwave signal at the initial microwave frequency; a lock-in amplifier outputs a frequency modulation signal to modulate the single-frequency microwave signal; the quantum current transformer is activated based on the single-frequency microwave signal to perform photodetection magnetic resonance detection; the quantum current transformer measures the magnetic field generated by the current-carrying conductor under test and obtains a demodulation result; the PID control unit performs feedback adjustment to the microwave module according to the demodulation result and target value to switch the microwave output frequency of the microwave module to a usable resonance frequency representing the magnetic field generated by the current-carrying conductor under test; the frequency acquisition unit captures the usable resonance frequency and transmits it to a data processing module; and the data processing module analyzes and processes the usable resonance frequency to obtain current information in the current-carrying conductor under test, including conductor current measurement. Current measurement method.

15. Obtaining the aforementioned recovery result means The photoelectric detection module is controlled to output a voltage signal representing the magnetic field generated by the current-carrying conductor under measurement, This includes demodulating the voltage signal using a two-phase digital demodulation method to obtain the demodulation result, adjusting the phase to set one of the two demodulated component values ​​to a value near zero, comparing the other component value to a target value as the input value to the PID control unit, and outputting a frequency adjustment parameter for adjusting the microwave module. The current measurement method according to claim 14.

16. The quantum current transformer further comprises an autophase adjustment module configured to automatically adjust the initial phase of the lock-in amplifier according to a set target. The current measurement method according to claim 15.

17. The quantum current transformer further comprises an automatic feature point acquisition module configured to automatically identify magnetic resonance feature points in the ODMR spectral line and acquire the corresponding microwave resonance frequencies at the magnetic resonance feature points. The current measurement method according to claim 14.

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