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

Abstract

A quantum sensing module, a quantum current transformer, and a current measurement method, the quantum sensing module comprising a quantum probe (1), a laser module (2), a microwave module (3), a photoelectric detection module (4), a lock-in amplifier (5), a frequency locking module (6), and a data processing module (7); the quantum probe (1) comprises a diamond sensing unit (11) and a microwave radiator (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 configured to receive photoluminescence generated by the diamond sensing unit (11) and convert same into an output voltage signal; the lock-in amplifier (5) comprises a modulating unit and a demodulating unit; the frequency locking module (6) comprises a PID control unit and a frequency acquiring unit. The quantum current transformer comprises a quantum sensing module, which is configured to measure a current in a conductor. The current measurement method is applied to the quantum current transformer to obtain current information within the conductor. This improves magnetic detection efficiency and increases current measurement precision.

Description

Quantum sensing module, quantum current transformer and current measurement method

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on March 14, 2024, with application number 202410289213.4, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of quantum precision measurement technology, for example, to a quantum sensing module, a quantum current transformer and a current measurement method. Background Art

[0003] In recent years, research on solid-state spin color center systems in the field of quantum precision has advanced rapidly, particularly in magnetic field detection. Optically detected magnetic resonance (ODMR) has been developed as a primary detection method. By studying the linear relationship between the magnetic resonance frequency and the external magnetic field, it is possible to sense, measure, and quantify the external magnetic field. However, some current research remains largely theoretical, and many application challenges remain to be addressed before these technologies can be commercialized.

[0004] Chinese patent number CN113804941B discloses a current measurement device and method based on diamond NV color centers, including laser excitation and reflected light receiving and analysis equipment, diamond NV color center probe, magnetic concentrator and microwave excitation equipment. The mutual inductor includes three measurement methods, namely full-optical measurement method, non-full-optical measurement method and combined measurement method; the solution of this application proposes a current measurement method based on optical detection magnetic resonance (ODMR). In this method, obtaining the magnetic resonance frequency is a difficulty in actual work.

[0005] Related technologies for extracting resonant frequencies primarily include manual point extraction and curve fitting. However, both methods require obtaining ODMR spectrum lines through a frequency sweep method when measuring different magnetic fields to obtain the resonant frequency, which takes a long time. Furthermore, the manual point extraction method suffers from low accuracy and impracticality for commercialization, while the curve fitting method suffers from a complex fitting derivation process and limited measurement bandwidth.

[0006] Summary of the Invention

[0007] This application proposes a quantum sensing module, a quantum current transformer and a current measurement method to solve the problems existing in the related technologies.

[0008] The present application provides a quantum sensing module, comprising:

[0009] A quantum probe, comprising a diamond sensitive unit and a microwave radiator, wherein the diamond sensitive unit is located in a working area of ​​the microwave radiator and contains nitrogen-vacancy NV color centers;

[0010] a laser module configured to output an excitation laser, wherein the excitation laser is configured to irradiate the diamond sensitive unit to cause the diamond sensitive unit to generate photoluminescence;

[0011] a microwave module configured to output a microwave signal, wherein the microwave signal is configured to form a microwave field through the microwave radiator and radiate to the corresponding diamond sensitive unit;

[0012] a photoelectric detection module configured to receive the photoluminescence generated by the diamond sensitive unit and convert it into an output voltage signal;

[0013] a lock-in amplifier, comprising a modulation unit and a demodulation unit, wherein the modulation unit is configured to output a microwave modulation signal to the microwave module, wherein the microwave modulation signal is configured to modulate the microwave signal, and the demodulation unit is configured to demodulate the voltage signal and output a demodulation result;

[0014] a frequency locking module, comprising a proportional-integral-differential (PID) control unit and a frequency acquisition unit, wherein the PID control unit is configured to take the demodulation result as an input value and output a frequency adjustment parameter, wherein the frequency adjustment parameter is configured to adjust the microwave output frequency of the microwave module, and the frequency acquisition unit is configured to read the microwave output frequency of the microwave module;

[0015] A data processing module is configured to communicate with the frequency locking module and the phase-locked amplifier to implement data analysis and processing of the target program.

[0016] In the quantum sensing module described above, in some embodiments of the present application, the quantum probe includes a transmission optical fiber, and the diamond sensitive unit is installed in a light conduction area on one end face of the transmission optical fiber; or

[0017] The quantum probe includes two transmission optical fibers, and the two transmission optical fibers are fused into one, and the diamond sensitive unit is installed on the fusion surface between the two transmission optical fibers.

[0018] In the quantum sensing module as described above, in some embodiments of the present application, the lock-in amplifier is a two-phase digital demodulator.

[0019] Another aspect of the present application provides a quantum current transformer, which includes the quantum sensing module as described above, configured to measure the current in a conductor, and further includes a conductor channel, an external magnetic shield is provided on the outside of the conductor channel, and the diamond sensitive unit is installed on a virtual annular ring between the conductor channel and the external magnetic shield.

[0020] As described above, in some embodiments of the present application, the quantum current transformer includes a plurality of the quantum sensing modules, and all diamond sensitive units are configured to be distributed on the virtual annular ring at equal intervals.

[0021] As described above, in some embodiments of the present application, the diamond sensitive unit is a diamond grain containing an ensemble NV color center, and the angles between the tangent line at the point on the virtual annular ring corresponding to the diamond grain and the axes of the four color centers of the diamond sensitive unit are the same or unequal.

[0022] The quantum current transformer as described above, in some embodiments of the present application, further comprises a magnetic concentrator, and the diamond sensitive unit is placed in a magnetic concentrating air gap of the magnetic concentrator.

[0023] In some embodiments of the present application, in the quantum current transformer as described above, when the quantum current transformer includes a plurality of the quantum sensing modules, the number of the quantum sensing modules is 4n, where n is a positive integer.

[0024] In the quantum current transformer as described above, in some embodiments of the present application, an internal magnetic shield is further provided on the outside of the conductor channel, and the diamond sensitive unit is located on the outside of the internal magnetic shield.

[0025] The quantum current transformer as described above, in some embodiments of the present application, further comprises a bias magnetic source, wherein the bias magnetic source is configured to apply a bias magnetic field of any angle to the diamond sensitive unit.

[0026] The quantum current transformer as described above, in some embodiments of the present application, further includes a primary ring, the conductor channel is located in the inner hole of the primary ring, and the external magnetic shield and the diamond sensitive unit are both located in the inner cavity of the primary ring.

[0027] The quantum current transformer as described above, in some embodiments of the present application, further includes a conductor rod, the central axis of the conductor rod coincides with the central axis of the inner hole of the primary ring, and the central axis of the conductor rod perpendicularly intersects the center of the virtual annular ring.

[0028] The quantum current transformer as described above, in some embodiments of the present application, further includes an insulator, the primary ring is installed on the top of the insulator, and the insulator is provided with a cable channel running through the upper and lower sides thereof.

[0029] Another aspect of the present application further provides a current measurement method, which is applied to the aforementioned quantum current transformer, comprising:

[0030] Initial parameter acquisition: Control the microwave module to output a swept-frequency microwave signal, draw the ODMR spectrum line of the quantum probe based on the swept-frequency microwave signal, and obtain the microwave resonance frequency at the magnetic resonance characteristic point on the ODMR spectrum line, which is recorded as the initial microwave frequency;

[0031] Conductor current measurement: controlling the microwave module to output a point-frequency microwave signal at the initial microwave frequency, setting a phase-locked amplifier to output a frequency-modulated signal to modulate the point-frequency microwave signal, and starting the quantum current transformer to perform optical detection magnetic resonance detection based on the point-frequency microwave signal. The quantum current transformer measures the magnetic field generated by the energized conductor to be measured and obtains a demodulation result. The PID control unit performs feedback adjustment on the microwave module based on the demodulation result and a target value so that the microwave output frequency of the microwave module is switched to an available resonant frequency that characterizes the magnetic field generated by the energized conductor to be measured. The frequency acquisition unit captures the available resonant frequency and transmits it to the data processing module. The data processing module analyzes and processes the available resonant frequency to obtain current information in the energized conductor to be measured.

[0032] In the current measurement method as described above, in some embodiments of the present application, obtaining the demodulation result includes: controlling the photoelectric detection module to output a voltage signal representing the magnetic field generated by the current-carrying conductor to be measured; demodulating the voltage signal through a two-phase digital demodulation method to obtain the demodulation result, and adjusting the phase so that one of the two demodulated component values ​​is near zero, and using the other component value as the input value of the PID control unit to compare with the target value, and outputting the frequency adjustment parameter for adjusting the microwave module.

[0033] In the current measurement method described above, in some embodiments of the present application, the quantum current transformer further includes a phase self-adjusting module, and the phase self-adjusting module is configured to automatically adjust the initial phase of the lock-in amplifier according to a set target.

[0034] In the current measurement method described above, in some embodiments of the present application, the quantum current transformer further includes a characteristic point self-acquisition module, which is configured to automatically identify the magnetic resonance characteristic points on the ODMR spectrum line and obtain the microwave resonance frequency corresponding to the magnetic resonance characteristic points. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to illustrate the embodiments of the present application, the drawings required for describing the embodiments will be introduced below. The drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] FIG1 is a system schematic diagram of a quantum sensing module in Example 1;

[0037] Figure 2 shows the ODMR spectrum line plotted with the demodulation value R as the ordinate;

[0038] FIG3 shows the ODMR spectrum line plotted with the demodulated Y-term component value as the ordinate;

[0039] FIG4 is a schematic diagram of the structure of the quantum sensing module in Example 1;

[0040] FIG5 is a schematic diagram of the structure of a quantum probe in Example 1;

[0041] FIG6 is another schematic diagram of the structure of the quantum probe in Example 1;

[0042] FIG7 is a schematic structural diagram of a quantum current transformer including a single quantum sensing module in Example 2;

[0043] FIG8 is a schematic diagram of another part of the structure of the quantum current transformer including four quantum sensing modules in Example 2;

[0044] FIG9 is a schematic diagram of a use of a magnetic concentrator in four quantum sensing modules in Example 2;

[0045] FIG10 is a schematic diagram of the combination of the primary ring and the conductor rod in the second embodiment. DETAILED DESCRIPTION

[0046] The embodiments described below with reference to the accompanying drawings are exemplary and are used to explain the present application.

[0047] One or more embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals are used throughout to refer to like components. In the following description, numerous details are set forth to provide a more thorough understanding of one or more embodiments. However, in various cases, one or more embodiments may be practiced without these details, and the various embodiments may be combined and referenced with each other unless inconsistent.

[0048] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units listed, but may include other steps or units that are not listed or inherent to these processes, methods, products or devices.

[0049] The NV (nitrogen-vacancy) color center in diamond is a common defect, consisting of a nitrogen atom and an adjacent vacancy (i.e., a missing carbon atom). This structure introduces an unpaired electron into the diamond, making the NV color center paramagnetic. In addition, the NV color center can also produce fluorescence under the irradiation of light, so it is of great significance in the optical and electronic applications of diamond; the formation of NV color centers in diamond usually requires certain treatments, such as introducing nitrogen atoms into the diamond lattice through ion implantation or electron beam irradiation, and then through high-temperature annealing treatment, so that the nitrogen atoms combine with adjacent vacancies to form NV color centers. In addition, other impurities and defects in diamond may also affect the properties of NV color centers, so there are high requirements for the purity and crystal quality of diamond.

[0050] Due to their excellent fluorescence properties and paramagnetism, NV centers have potential applications in biomarkers, quantum information, and magnetic imaging. For example, NV centers can be used as fluorescent markers for imaging and detection of cells and tissues, or as quantum bits for quantum computing and quantum communication. Furthermore, due to their paramagnetic nature, NV centers can be exploited for magnetic imaging and the development of magnetic sensors.

[0051] When there are a large number of NV color centers in diamond (that is, it contains ensemble NV color centers), due to the particularity of the diamond lattice, the randomly oriented NV color centers will make the diamond NV color center have four color center axes determined by the angles. At this time, the diamond ensemble NV color center has vector detection capability as a sensitive unit.

[0052] The key to optically detected magnetic resonance (ODMR) is to use the sensitivity and high resolution of optics to detect magnetic resonance signals. In an optically detected magnetic resonance experiment of diamond NV centers, the diamond NV center must first be placed in an external magnetic field to allow the magnetic moments of the atomic nuclei or electrons in the diamond NV center to interact with the external magnetic field. Then, by radiating microwaves of a specific frequency into the sample, the atomic nuclei or electrons in the diamond NV center undergo energy level transitions. These energy level transitions cause the diamond NV center to absorb or emit electromagnetic radiation of a specific frequency, forming a magnetic resonance signal. The magnetic resonance signal is then detected using optical technology. Quantum sensing measurement can be achieved by calibrating and converting the magnetic resonance signal to physical quantities such as the magnetic field.

[0053] The so-called ODMR spectrum line generally refers to the detection curve drawn by implementing the optical detection magnetic resonance measurement method through the swept frequency method (this curve is divided into modulated and unmodulated types. The point where the magnetic resonance frequency is located on the curve is also called the magnetic resonance characteristic point. On the modulated ODMR spectrum line, the magnetic resonance characteristic point is the zero crossing point, and on the unmodulated ODMR spectrum line, the magnetic resonance characteristic point is the resonance peak point). Since the swept frequency method uses swept frequency microwaves to work, the spectrum line drawing time is long, which is not conducive to the rapid extraction of characteristic values ​​for magnetic field calculation.

[0054] Example 1

[0055] 1 , this embodiment discloses a quantum sensing module, including a quantum probe, a laser module, a microwave module, a photoelectric detection module, a lock-in amplifier, a frequency locking module, and a data processing module.

[0056] In this example, the quantum probe includes a diamond sensitive unit and a microwave radiator. The diamond sensitive unit is located in the microwave radiator's working area and contains NV color centers. In some examples, the microwave radiator can be a microstrip antenna or a spiral copper wire, and the diamond sensitive unit is a diamond grain containing an ensemble of NV color centers.

[0057] In this example, the laser module is configured to output an excitation laser, which is configured to illuminate the diamond-sensitive unit to cause it to produce photoluminescence. As some examples, the excitation laser output by the laser module has a wavelength of 532 nanometers (nm). Under this laser illumination, the diamond-sensitive unit produces red photoluminescence.

[0058] In this example, the microwave module is configured to output a microwave signal, which is configured to form a microwave field through the microwave radiator and radiate to the corresponding diamond sensitive unit. As some examples, the microwave module includes a microwave source, a microwave amplifier, and a microwave circulator. The microwave source is the source of microwave signal transmission, the microwave amplifier amplifies microwave power, and the microwave circulator prevents reverse transmission of the microwave signal.

[0059] In this example, the photodetection module is configured to receive the photoluminescence generated by the diamond sensitive unit and convert it into an output voltage signal. As some examples, the photodetection module includes a photodiode (such as an avalanche diode) and a filtering structure (such as a filter). The photoluminescence directed to the photodiode needs to be filtered out of stray light by the filtering structure in advance.

[0060] In this example, the lock-in amplifier includes a modulation unit and a demodulation unit, wherein the modulation unit is configured to output a microwave modulation signal to the microwave module, and the demodulation unit is configured to demodulate the voltage signal and output a demodulation result. As some examples, the lock-in amplifier is a two-phase digital demodulator.

[0061] In some embodiments, the microwave modulation signal is configured to modulate the microwave signal (eg, including frequency modulation or amplitude modulation).

[0062] In this example, the frequency locking module includes a proportional integral differential (PID) control unit and a frequency acquisition unit. The PID control unit is configured to take the demodulation result as an input value and output a frequency adjustment parameter. 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. As for the PID control unit, it has an input value and a target value. By comparing the two, a feedback adjustment parameter can be output to change the input value until it is equal to or close to the target value. In this example, the demodulation result output by the phase-locked amplifier can be used as the input value of the PID control unit.

[0063] In some embodiments, the data processing module is configured to communicate with the frequency locking module and the lock-in amplifier to perform data analysis and processing on a target program. A target program is a program that implements a specific function or algorithm. The target program can be configured based on actual data processing requirements.

[0064] In this example, the data processing module is configured to perform data analysis and processing; for example, the data processing module is included in the host computer, and contains at least a program method for calculating the magnetic field based on the microwave resonance frequency, a functional module for realizing ODMR spectrum line drawing, etc.

[0065] To facilitate understanding of the role of the PID control unit in this embodiment, an exemplary explanation is provided here. When performing optical detection magnetic resonance measurement of diamond NV color centers using swept-frequency microwaves, the measured photoluminescence output is converted into a voltage signal by a photodetection module and then input to a lock-in amplifier. After demodulation using a bidirectional digital demodulation method (assuming the microwave modulation signal is a frequency-modulated signal), the demodulation results (demodulated value R, demodulated X-component value, demodulated Y-component value, and phase value) are obtained. When constructing ODMR spectra using different demodulation results and microwave frequencies as the ordinate and abscissa, spectra similar to those shown in Figure 2 (plotted with demodulated value R as the ordinate) or Figure 3 (plotted with demodulated Y-component value as the ordinate) are obtained. Analysis of the spectra reveals that the characteristic magnetic resonance points are all zero-crossing points. Therefore, when switching the magnetic field, simply setting the ordinate to zero allows the microwave resonance frequency (i.e., the zero-crossing point) to be traced under the current magnetic field. By setting the target value of the PID control unit to 0, the microwave resonance frequency can be quickly locked (quickly switching from the microwave resonance frequency of the previous magnetic field to the microwave resonance frequency of the next magnetic field). This method of obtaining the microwave resonance frequency does not require drawing the ODMR spectrum through a large-scale frequency sweep, which greatly improves the speed of obtaining the microwave resonance frequency, and thus improves the magnetic measurement efficiency.

[0066] Here, an exemplary structural composition design of a quantum sensing module is introduced, as shown in Figure 4, which includes a quantum probe 1, a laser module 2, a microwave module 3, a photoelectric detection module 4, a phase-locked amplifier 5, a frequency locking module 6 and a data processing module 7. The quantum probe 1 includes a diamond sensitive unit 11 and a microwave radiator 12, the laser module 2 includes a 532nm laser 21 and an optical modulator 22, the microwave module 3 includes a microwave source 31, a microwave amplifier 32 and a microwave circulator 33, and the photoelectric detection module 4 includes a photodiode 41, a filter 42 and a dichroic plate 43. The connection method of the above devices is shown in the figure (the structure should also include some necessary basic connectors, such as optical fibers, optical fiber couplers and electrical signal transmission cables). Based on the connection method of the above devices, the following working process is formed: the laser 21 is started to generate 532nm laser light, the laser light modulated by the optical modulator 22 is reflected by the dichroic plate 43 (red-transmitting and blue-reflecting dichroic plate), and is coupled into the optical fiber and transmitted to the diamond sensitive unit 11. The microwave source 31 outputs a microwave signal, which passes through the microwave amplifier 32 and the microwave circulator 33 in sequence, and is finally transmitted to the microwave radiator 12 through the radio frequency transmission line. The microwave radiator 12 radiates the microwave signal to the diamond sensitive unit 11 in the form of a field; after the dual action of microwaves and lasers, the diamond sensitive unit 11 produces red photoluminescence, which returns along the way and passes through the two-color plate 43. After the stray light is filtered by the filter 42, it is received by the photodiode 41 and forms an electrical signal. The electrical signal is transmitted to the phase-locked amplifier 5 for demodulation processing (the phase-locked amplifier 5 also performs microwave modulation on the microwave source 31), and the demodulation result is transmitted to the frequency locking module 6. When the external magnetic field changes, the frequency locking module 6 can quickly lock the corresponding microwave resonance frequency at all times. The microwave resonance frequency is subsequently processed by the data processing module 7 to obtain the physical quantity to be measured.

[0067] For the quantum probe mentioned in Example 1, there are various ways to excite the diamond sensitive unit 11 with laser and recover fluorescence. In some examples, as shown in FIG5 , the quantum probe 1 includes a transmission optical fiber 13 (i.e., input / output optical fiber), and the diamond sensitive unit 11 is installed in the light conduction area of ​​one end face of the transmission optical fiber 13. In this structure, the excitation laser for exciting the diamond sensitive unit 11 and the photoluminescence generated by the diamond sensitive unit 11 are both transmitted through the same transmission optical fiber 13, and the light excitation and collection processes are both achieved through the same end; or as shown in FIG6 , the quantum probe 1 includes two transmission optical fibers 13, and the two transmission optical fibers 13 are fused into one, and the diamond sensitive unit 11 is installed at the fusion surface between the two transmission optical fibers 13. In this structure, the excitation laser is transmitted from the transmission optical fiber 13 on one side to the diamond sensitive unit 11, and the photoluminescence is transmitted from the transmission optical fiber 13 on the other side to the photoelectric detection module 4.

[0068] In some examples, the lock-in amplifier is a dual-phase digital demodulator. The demodulation results obtained by the dual-phase demodulation subunit include a demodulated value R, a demodulated X-component value, a demodulated Y-component value, and a phase value. In some examples, a phase auto-adjustment module is also included, configured to automatically adjust the initial phase of the lock-in amplifier according to a set target. When using a dual-phase digital lock-in amplifier for modulation and demodulation, and desiring to plot an ODMR spectrum as shown in FIG4 (plotted with the demodulated Y-component value as the vertical axis), initial phase adjustment is required (i.e., phase adjustment is required to bring the demodulated X-component value closer to zero) to achieve more accurate measurement requirements. For example, the initial phase is manually adjusted continuously, and the value of one component is observed to determine whether it meets the set target. This manual adjustment process has a low degree of automation, so it is automated in the software program. In one example, the set goal can be to make the demodulated X-term component value or the demodulated Y-term component value equal to zero or near zero (i.e., a near-zero value). Based on this set goal, the software program can continuously correct the initial phase and complete the closed loop by determining whether the set goal is achieved. The program programming is relatively simple.

[0069] For the first embodiment, it can realize the measurement of the magnetic field. Considering the conversion relationship between electromagnetics, the present application also provides a second embodiment for current measurement.

[0070] Example 2

[0071] As shown in FIG7 , this embodiment discloses a quantum current transformer, which is configured to measure the current in a conductor, and includes one or more quantum sensing modules as described in Example 1 (for ease of presentation, the structure of the quantum sensing module covered in FIG7 is consistent with the structure shown in FIG4 , but it should be understood that the structure of the quantum sensing module in this example is not limited to this), and also includes a conductor channel 8, an external magnetic shield 9 is provided on the outside of the conductor channel 8, and the diamond sensitive unit 11 is installed on a virtual annular ring between the conductor channel 8 and the external magnetic shield 9.

[0072] As shown in FIG8 , when the quantum current transformer includes a plurality of the quantum sensing modules, all the diamond sensitive units 11 are configured to be distributed at equal intervals on the virtual annular ring.

[0073] In one embodiment, when the quantum current transformer includes multiple quantum sensing modules, since each quantum sensing module includes a quantum probe 1, and the quantum probe 1 includes a diamond sensitive unit 11 and a microwave radiator 12, the number of diamond sensitive units 11 is correspondingly multiple. When there are multiple diamond sensitive units 11, all diamond sensitive units 11 are configured to be evenly spaced on the virtual annular ring. As shown in Figure 8, four diamond sensitive units 11 are configured to be evenly spaced on the virtual annular ring.

[0074] Considering the loop integration's suppression mechanism for magnetic measurement noise, as one embodiment, when the quantum current transformer includes multiple quantum sensing modules, the number of quantum sensing modules is 4n, where n is a positive integer. For example, n is 1 or 2. In this case, the magnetic field information measured by multiple quantum sensing modules, after summing and averaging, effectively eliminates the external magnetic field, thereby improving the accuracy of current measurement.

[0075] In some embodiments, the diamond sensitive unit used in the quantum current transformer is a diamond grain containing an ensemble NV color center, which can produce a stronger fluorescence excitation effect and is conducive to the collection of fluorescence data. For the ensemble NV color center, it has four NV color center axes. Based on the interaction between magnetic fields in different directions and the four NV color center axes, it will be manifested in the ODMR spectrum line, forming multiple peak shapes (2 peaks, 4 peaks, 6 peaks, or 8 peaks).

[0076] For a two-peak ODMR spectrum, due to its small number of peaks, fewer microwave resonant frequencies need to be locked and tracked, making locking easy and fast, making it ideal for situations requiring rapid current measurement. In some examples, the angle between the tangent line corresponding to the diamond grain on the aforementioned virtual annular ring and the four color center axes of the diamond sensitive unit can be aligned, resulting in a two-peak ODMR spectrum.

[0077] For 8-peak ODMR lines, based on the multi-directional axial relationship with the magnetic field, vector measurement of the magnetic field can be achieved. In this case, although a large number of microwave resonant frequencies must be locked and tracked, the resulting vector current measurement can well meet some detection requirements. In other examples, 8-peak ODMR lines are generated by ensuring that the angles between the tangent line corresponding to the diamond grain point on the aforementioned virtual annular ring and the four color center axes of the diamond sensitive unit are different.

[0078] Taking into account the complexity of the current detection environment, for example, in small current scenarios (when the magnetic field generated by the current-carrying conductor is not much different from the external interference magnetic field), in order to improve the accuracy of current measurement, in some embodiments, as shown in Figure 9 (the scenario of four quantum probes), the quantum current transformer is also provided with a magnetic concentrator 111, and the diamond sensitive unit 11 is placed in the magnetic air gap 112 of the magnetic concentrator 111. The magnetic field generated by the current-carrying conductor to be measured is amplified by the magnetic concentrator 111, and the effect of the external magnetic field is weakened, thereby improving the accuracy of current measurement.

[0079] In order to improve the ability of the device to suppress external magnetic field interference, in some embodiments, as shown in Figure 7, an internal magnetic shield 91 is also provided, and the diamond sensitive unit 11 is located on the outside of the internal magnetic shield 91. The matching design of the internal magnetic shield 91 and the external magnetic shield 9 further improves the noise reduction ability of the device.

[0080] In some scenarios, some additional magnetic fields need to be provided to complete the initial debugging or corresponding testing of the quantum current transformer. In some embodiments, the quantum current transformer is also equipped with a bias magnetic source, which is configured to apply a bias magnetic field of any angle to the diamond sensitive unit, wherein the bias magnetic source can be a permanent magnet or a energized coil.

[0081] Based on some practical application considerations, as shown in Figures 7 and 8, the quantum current transformer also includes a primary ring 10. The conductor channel 8 is located in the inner hole of the primary ring 10. The external magnetic shield 9 and the diamond sensitive unit 11 are both located in the inner cavity of the primary ring 10. The primary ring 10 not only facilitates the installation of some front-end components, but also provides good protection. In some embodiments, as shown in Figure 10, the quantum current transformer also includes a conductor rod 101. The central axis of the conductor rod 101 coincides with the central axis of the inner hole of the primary ring 10, and the central axis of the conductor rod 101 perpendicularly intersects the center of the virtual annular ring. This means that the distance between each quantum probe 1 and the conductor rod 101 is equal, thus ensuring the consistency of the conductor magnetic field measurement. In some embodiments, the primary ring 10 is mounted on the top of an insulator. The insulator has a cable channel running through its upper and lower sides. The cable channel is configured to install transmission components such as optical fibers and wires.

[0082] On the other hand, this article also proposes a current measurement method applicable to the aforementioned quantum current transformer, which includes an initial parameter acquisition step and a conductor current measurement step, wherein:

[0083] Initial parameter acquisition step: Control the microwave module to output a swept-frequency microwave signal, draw the ODMR spectrum of the quantum probe based on the swept-frequency microwave signal, and obtain the microwave resonance frequency at the magnetic resonance characteristic point on the ODMR spectrum, which is recorded as the initial microwave frequency;

[0084] During the initial parameter acquisition step, the diamond sensitive unit outputs feedback fluorescence under the dual effects of the swept-frequency microwave signal and the laser signal. This detection signal is processed and mapped to obtain the target ODMR spectrum line. The target ODMR spectrum line can generally be of two types: one in which the magnetic resonance characteristic point is a zero-crossing point (the swept-frequency microwave is modulated), and the other in which the magnetic resonance characteristic point is a peak point (the swept-frequency microwave is not modulated). During this step, the PID control unit does not begin to function. Once the swept-frequency ODMR spectrum line is obtained, the microwave resonant frequency can be manually acquired. Alternatively, a software program can be configured to automatically acquire the microwave resonant frequency. In this case, the quantum current transformer also includes a characteristic point self-acquisition module, which is configured to automatically identify the magnetic resonance characteristic points on the ODMR spectrum line and acquire the microwave resonant frequency corresponding to the magnetic resonance characteristic points.

[0085] Based on the ODMR spectrum under frequency modulation, analysis shows that the microwave resonance frequency of any magnetic field belongs to the horizontal coordinate of the zero-crossing point on the ODMR spectrum under frequency modulation. Therefore, if the locking condition is set based on the zero-crossing point, the microwave resonance frequency of the next magnetic field can be quickly locked. Of course, the premise is that there must be a starting microwave resonance frequency that matches the current diamond sensitive unit. This is the actual purpose of the initial parameter acquisition step.

[0086] Conductor current measurement steps include: controlling a microwave module to output a point-frequency microwave signal at an initial microwave frequency, setting a phase-locked amplifier to output a frequency-modulated signal to modulate the point-frequency microwave signal, starting a quantum current transformer based on the point-frequency microwave signal to implement a light detection magnetic resonance detection process, the quantum current transformer measuring the magnetic field generated by the energized conductor to be measured and obtaining a demodulation result, the PID control unit performing feedback adjustment on the microwave module based on the demodulation result and a target value so that its microwave output frequency is switched to an available resonant frequency that characterizes the magnetic field generated by the energized conductor to be measured, the frequency acquisition unit capturing the available resonant frequency and transmitting it to a data processing module, and the data processing module analyzing and processing the available resonant frequency to obtain current information in the energized conductor to be measured.

[0087] When measuring conductor current, there is no need to use swept-frequency microwaves. Instead, a point-frequency microwave signal (i.e., the initial microwave frequency obtained in the previous step) is used in conjunction with a laser signal. The PID control unit tracks the initial point-frequency microwave signal. When the external magnetic field changes, the microwave resonant frequency can be quickly locked, thereby enabling a rapid current measurement process.

[0088] The aforementioned current measurement scheme mentions comparing the demodulation results with the target data to obtain the frequency adjustment parameters. Different demodulation methods express the demodulation results differently. For example, in single-phase demodulation, the demodulation result only includes the demodulation value R (non-negative); in dual-phase demodulation, the demodulation result includes the demodulation value R (non-negative), the demodulation X component value, the demodulation Y component value, and the phase value.

[0089] The ODMR spectrum constructed using the demodulated value R value and the microwave frequency is shown in Figure 2. If the demodulated value R value is used as the input value of the PID control unit and compared with the target value to analyze the spectrum, when the magnetic field is switched, the new magnetic resonance characteristic point is the zero-crossing point on the graph (the zero-crossing point is the target locked by the PID control unit, so the target value is generally set to 0), and the magnetic resonance characteristic point of the previous magnetic field is point A (or point B). In order to achieve the movement of the magnetic resonance characteristic point from point A (or point B) to the zero-crossing point, a frequency adjustment parameter needs to be provided. If the magnetic resonance characteristic point is at point A, a positive frequency adjustment parameter needs to be set to increase the frequency of the microwave signal. If the magnetic resonance characteristic point is at point B, a negative frequency adjustment parameter needs to be set to reduce the frequency of the microwave signal. Therefore, when outputting the frequency adjustment parameter, it is also necessary to determine the direction of feedback adjustment. The conventional solution is to randomly apply a positive (or negative) frequency adjustment parameter, and then determine whether the demodulation result after adjustment is close to the zero point. If so, continue to apply the positive (or negative) frequency adjustment parameter until the frequency locking process is completed; if not, apply the negative (or positive) frequency adjustment parameter to perform frequency adjustment. This frequency adjustment method requires judgment of the adjustment direction, resulting in a long frequency adjustment time and bandwidth limitation (taking Figure 2 as an example, the above adjustment steps can only be implemented in the part between the two peak points).

[0090] Since the direction needs to be considered when adjusting the microwave signal feedback, the frequency locking speed will be increased, affecting the measurement speed of the entire device.

[0091] In order to improve the feedback regulation efficiency of the PID control unit, the following exemplary design scheme is proposed:

[0092] In the conductor current measurement step, the photoelectric detection module is controlled to output a voltage signal representing the magnetic field generated by the energized conductor to be measured, and the voltage signal is demodulated using a two-phase digital demodulation method;

[0093] By adjusting the phase, one of the two demodulated component values ​​is made close to zero, and the other component value is used as the input value of the PID control unit to compare with the target value, and the frequency adjustment parameter of the microwave signal is output.

[0094] In an exemplary embodiment, a dual-phase digital lock-in amplifier is used to demodulate a voltage signal using a dual-phase digital demodulation method. The output demodulation results include a demodulated value R, a demodulated X-component value, a demodulated Y-component value, and a phase value. The dual-phase digital lock-in amplifier is phase-adjusted (referring to the phase of the frequency modulation signal or the reference signal) so that the demodulated X-component value (or the demodulated Y-component value) is zero. The demodulated Y-component value (or the demodulated X-component value) is used as the input value of a PID control unit, and a target value is set. The input value and the target value are compared to output a frequency adjustment parameter to adjust the microwave signal output by the microwave source.

[0095] The demodulated X-component value is set to zero, the demodulated Y-component value is used as the input value of the PID control unit, and the target value is set to 0. In this scenario, the ODMR spectrum is constructed using the demodulated Y-component value and the microwave frequency, as shown in FIG3. When the magnetic field changes, the new magnetic resonance characteristic point is the zero-crossing point on the graph (the zero-crossing point is the target locked by the PID control unit. When the demodulation result is equal to 0, it means it is the magnetic resonance characteristic point, so the target value is generally set to 0). The magnetic resonance characteristic point of the previous magnetic field is point A (or point B). In order to achieve the movement of the magnetic resonance characteristic point from point A (or point B) to the zero-crossing point, a frequency adjustment parameter needs to be provided. Analysis of the spectrum shown in FIG3 shows that the demodulated Y-component value has positive and negative values ​​before and after the zero-crossing point. Therefore, when the demodulated Y-component value is greater than 0, the microwave signal frequency can be reduced, otherwise the microwave signal frequency can be increased. This feedback adjustment method is faster, effectively shortens the adjustment time of the PID control unit, improves the measurement speed of the quantum current transformer, and has a wider measurement bandwidth.

[0096] In the above scheme, it is mentioned that by adjusting the initial phase, one of the two demodulated component values ​​is made to be near-zero. Regarding the near-zero value, it can be selected as 0, but it can also fluctuate slightly around 0 (the fluctuation amplitude can be limited to less than 10% of the component value amplitude); for example, by manually adjusting the initial phase and observing in real time whether the selected component value on the phase lock is zero, of course, automatic phase adjustment can also be achieved by designing a software program. In this case, the quantum current transformer also includes a phase self-adjustment module, which is configured to automatically adjust the initial phase of the phase-locked amplifier according to the set target.

[0097] In some embodiments, this embodiment does not need to draw the ODMR sweep spectrum line every time the magnetic field is measured. It can quickly track the changing magnetic resonance frequency by comparing the target data with the demodulation result, greatly shortening the acquisition time of the new magnetic resonance frequency and improving the measurement speed of the quantum current transformer.

[0098] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" mean that the features, structures, materials, or characteristics described in conjunction with the 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. A quantum sensing module, comprising: A quantum probe, comprising a diamond sensitive unit and a microwave radiator, wherein the diamond sensitive unit is located in a working area of ​​the microwave radiator and contains nitrogen-vacancy NV color centers; a laser module configured to output an excitation laser, wherein the excitation laser is configured to irradiate the diamond sensitive unit to cause the diamond sensitive unit to generate photoluminescence; a microwave module configured to output a microwave signal, wherein the microwave signal is configured to form a microwave field through the microwave radiator and radiate to the corresponding diamond sensitive unit; a photoelectric detection module configured to receive the photoluminescence generated by the diamond sensitive unit and convert it into an output voltage signal; a lock-in amplifier, comprising a modulation unit and a demodulation unit, wherein the modulation unit is configured to output a microwave modulation signal to the microwave module, wherein the microwave modulation signal is configured to modulate the microwave signal, and the demodulation unit is configured to demodulate the voltage signal and output a demodulation result; a frequency locking module, comprising a proportional-integral-differential (PID) control unit and a frequency acquisition unit, wherein the PID control unit is configured to take the demodulation result as an input value and output a frequency adjustment parameter, wherein the frequency adjustment parameter is configured to adjust the microwave output frequency of the microwave module, and the frequency acquisition unit is configured to read the microwave output frequency of the microwave module; A data processing module is configured to communicate with the frequency locking module and the phase-locked amplifier to implement data analysis and processing of the target program.

2. The quantum sensing module according to claim 1, wherein: The quantum probe includes a transmission optical fiber, and the diamond sensitive unit is installed in the light conduction area of ​​one end face of the transmission optical fiber; or The quantum probe includes two transmission optical fibers, and the two transmission optical fibers are fused into one, and the diamond sensitive unit is installed on the fusion surface between the two transmission optical fibers.

3. The quantum sensing module according to claim 1, wherein: The lock-in amplifier is a dual-phase digital demodulator.

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

5. The quantum current transformer according to claim 4, wherein: The quantum current mutual inductance includes a plurality of the quantum sensing modules, and all diamond sensitive units are configured to be distributed on the virtual annular ring at equal intervals.

6. The quantum current transformer according to claim 4 or 5, wherein: The diamond sensitive unit is a diamond grain containing an ensemble NV color center, and the angles between the tangent line at the point on the virtual annular ring corresponding to the diamond grain and the axes of the four color centers of the diamond sensitive unit are the same or unequal.

7. The quantum current transformer according to claim 4 or 5, further comprising a magnetic concentrator, wherein the diamond sensitive unit is placed in a magnetic concentrating air gap of the magnetic concentrator.

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

9. The quantum current transformer according to claim 4 or 5, wherein: An internal magnetic shield is further provided on the outside of the conductor channel, and the diamond sensitive unit is located on the outside of the internal magnetic shield. 10 . The quantum current transformer according to claim 4 , further comprising a bias magnetic source configured to apply a bias magnetic field of any angle to the diamond sensitive unit.

11. The quantum current transformer according to claim 4 or 5, further comprising a primary ring, wherein the conductor channel is located in an inner hole of the primary ring, and the external magnetic shield and the diamond sensitive unit are both located in an inner cavity of the primary ring.

12. The quantum current transformer according to claim 11, further comprising a conductor rod, wherein the central axis of the conductor rod coincides with the central axis of the inner hole of the primary ring, and the central axis of the conductor rod perpendicularly intersects the center of the virtual annular ring.

13. The quantum current transformer according to claim 11, further comprising an insulator, wherein the primary ring is mounted on the top of the insulator, and the insulator is provided with a cable channel passing through the upper and lower sides thereof.

14. A current measurement method, applied to the quantum current transformer according to any one of claims 4 to 13, comprising: Initial parameter acquisition: Control the microwave module to output a swept-frequency microwave signal, draw the optical detection magnetic resonance (ODMR) spectrum of the quantum probe based on the swept-frequency microwave signal, and obtain the microwave resonance frequency at the magnetic resonance characteristic point on the ODMR spectrum, which is recorded as the initial microwave frequency; Conductor current measurement: controlling the microwave module to output a point-frequency microwave signal at the initial microwave frequency, setting a phase-locked amplifier to output a frequency-modulated signal to modulate the point-frequency microwave signal, and starting the quantum current transformer to perform optical detection magnetic resonance detection based on the point-frequency microwave signal. The quantum current transformer measures the magnetic field generated by the energized conductor to be measured and obtains a demodulation result. The PID control unit performs feedback adjustment on the microwave module based on the demodulation result and a target value so that the microwave output frequency of the microwave module is switched to an available resonant frequency that characterizes the magnetic field generated by the energized conductor to be measured. The frequency acquisition unit captures the available resonant frequency and transmits it to the data processing module. The data processing module analyzes and processes the available resonant frequency to obtain current information in the energized conductor to be measured.

15. The current measuring method according to claim 14, wherein: The obtaining of the demodulation result includes: Controlling the photoelectric detection module to output a voltage signal representing the magnetic field generated by the energized conductor to be tested; The voltage signal is demodulated by a two-phase digital demodulation method to obtain the demodulation result, and through phase adjustment, one of the two demodulated component values ​​is made to be near zero, and the other component value is used as the input value of the PID control unit to be compared with the target value, and the frequency adjustment parameter of the microwave module is output.

16. The current measurement method according to claim 15, wherein: The quantum current transformer further comprises a phase self-adjusting module, which is configured to automatically adjust the initial phase of the lock-in amplifier according to a set target.

17. The current measurement method according to claim 14, wherein: The quantum current transformer further includes a characteristic point self-acquisition module, which is configured to automatically identify magnetic resonance characteristic points on the ODMR spectrum line and acquire the microwave resonance frequency corresponding to the magnetic resonance characteristic points.

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