Quantum magnetic probe, current measuring equipment and measuring method

Abstract

The invention relates to the technical field of quantum precision measurement, and provides a quantum magnetic probe which comprises a diamond block, a polarization-maintaining single-mode optical fiber and a microwave radiator. According to the scheme, the optical waveguide for transmitting the linear polarization excitation light in the specific direction is connected with the diamond block containing the NV color center, and the transmission direction of the linear polarization excitation light and the NV axial direction are controlled to form a specific angle, so that efficient excitation in the specified NV axial direction is realized, and the measurement accuracy of the magnetic component in the specified axial direction is further improved; the structure is simple and stable, the size is small, and the practicability is high.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement technology, and in particular to a quantum magnetic probe, current measuring equipment and a measuring method. Background Art

[0002] In recent years, research on solid-state spin color center systems in the field of quantum precision has developed rapidly, especially in the detection of magnetic fields. A detection method based on optically detected magnetic resonance (ODMR) has been developed. By studying the linear relationship between the magnetic resonance frequency and the external magnetic field, the sensing, measurement and quantification of the external magnetic field can be achieved.

[0003] However, when the current diamond NV color center sensing structure is measured based on ODMR technology, there is a problem of inaccurate spin resonance frequency positioning due to the low NV color center excitation efficiency. The spin resonance frequency corresponding to each NV axis can measure the magnetic component of the external magnetic field on the NV axis. If the spin resonance frequency positioning is not accurate, the magnetic field measurement accuracy will be reduced. In some non-vector measurement scenarios, such as current detection in a conductor, the direction of the electromagnetic field is generally fixed. It is only necessary to accurately measure the magnetic field size in this direction to obtain current information. Therefore, it is very necessary to improve the measurement accuracy of the magnetic component on the NV axis. There are related technologies that use linearly polarized light to improve the NV color center excitation efficiency, but they mainly achieve polarization excitation by adjusting spatial light to irradiate the NV color center. This probe has a complex structure, low stability and practicality, and is generally large in size, making it difficult to apply in practice. Summary of the Invention

[0004] The present invention proposes a quantum magnetic probe, current measurement equipment and measurement method. By connecting an optical waveguide that transmits linearly polarized excitation light in a specific direction to a diamond block containing NV color centers, and controlling the transmission direction of the linearly polarized excitation light to form a specific angle with the NV axis, efficient excitation of the specified NV axis can be achieved. This structure is simple and stable, compact in size and highly practical.

[0005] To achieve the above object, the present invention provides the following technical solutions: A quantum magnetic probe, comprising: - a diamond block comprising a first face and a second face perpendicular thereto, wherein the diamond block contains an ensemble NV color center, wherein the first NV axis is perpendicular to the first face; - a polarization-maintaining single-mode optical fiber, the output end face of which is fixedly bonded to the second face of the diamond block and is configured such that its transmission axis is perpendicular to the first NV axis; - A microwave radiator, wherein the diamond block is installed in a radiation zone of the microwave radiator.

[0006] In a preferred design of the quantum magnetic probe as described above, the transmission principal axis is the fast axis of the polarization-maintaining single-mode optical fiber.

[0007] The quantum magnetic probe as described above, in a preferred design, further comprises a photodetection module arranged proximate to the diamond block, for collecting photoluminescence generated by the diamond block through spatial light transmission mode.

[0008] The quantum magnetic probe as described above, in a preferred design, the surface of the diamond block facing the photodetection module is provided with a first form of cured glue for concentrating photoluminescence.

[0009] The quantum magnetic probe as described above, in a preferred design, the first form of cured glue formed does not produce photoluminescence effect under irradiation of excitation light.

[0010] The quantum magnetic probe as described above, in a preferred design, further comprises a laser module for aligning excitation light with input linear polarization to the input end surface of the polarization maintaining single-mode fiber.

[0011] Another aspect of the present application further introduces another quantum magnetic probe, wherein the polarization maintaining single-mode fiber is replaced by a polarization fiber.

[0012] Another aspect of the present application further introduces a current measurement device for detecting current information of a to-be-measured energized conductor, comprising: at least one quantum magnetic probe as described above; a magnetic concentrating ring, the magnetic concentrating ring is sleeved outside the to-be-measured energized conductor, the quantum magnetic probe is arranged in a magnetic concentrating gap of the magnetic concentrating ring, and is configured to be parallel to the direction of the magnetic concentrating magnetic field of the magnetic concentrating ring along the first NV axis; Wherein, the current measurement device is used to detect magnetic field information generated by the to-be-measured current by reading the spin resonance related to the magnetic field information in the quantum magnetic probe, and further obtain the to-be-measured current information by inversely calculating the magnetic field information.

[0013] Another aspect of the present application further introduces a measurement method, which applies the current measurement device as described above, and obtains independent spin resonance data related to the first NV axis during measurement, and calculates the to-be-measured current information based on the data.

[0014] Another aspect of the present application further introduces another measurement method, which applies the current measurement device as described above, and simultaneously obtains independent spin resonance data related to the first NV axis and combined spin resonance data of other three-direction NV axes during measurement; when the spin resonance data is less than a set value, the combined spin resonance data is used to calculate the to-be-measured current information; when the spin resonance data is greater than the set value, the independent spin resonance data is used to calculate the to-be-measured current information.

[0015] Compared with the prior art, the present application has the following beneficial effects: By connecting the optical waveguide transmitting linearly polarized excitation light in a specific direction with the diamond block containing NV color centers, and controlling the transmission direction of the linearly polarized excitation light to be at a specific angle with the NV axial direction, efficient excitation of the specified NV axial direction is realized, and the measurement accuracy of the magnetic component in the specified axial direction is improved. The structure is simple, stable, small in size and strong in practicality.

[0016] During current measurement, the spin resonance frequency data is obtained by tracking the outermost peak of the ODMR, which maintains high linearity during large-span magnetic field measurement, meets the demand of high-precision large-range current measurement, and realizes the high uniformity of the magnetic field direction and the specified NV axial direction through magnetic aggregation. Combined with the quantum magnetic probe with high excitation efficiency, the current measurement accuracy is effectively improved. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed for the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The schematic diagram of the quantum magnetic probe in embodiment one is shown in the figure. Figure 2 The four-axis schematic diagram of the ensemble NV color center is shown in the figure. Figure 3 The installation schematic diagram of the polarization maintaining single-mode fiber and the diamond block in embodiment one is shown in the figure. Figure 4 The schematic diagram of the quantum magnetic probe with a photoelectric detection module in embodiment one is shown in the figure. Figure 5 The structural schematic diagram of the current measurement device in embodiment two is shown in the figure. Figure 6 The layout schematic diagram of the first NV axial direction parallel to the magnetic field aggregation in embodiment two is shown in the figure. Figure 7 The ODMR diagram with two pairs of peaks is shown in the figure. Figure 8 The linearity diagram of the magnetic field and the microwave frequency of each NV axial direction is shown in the figure. DETAILED DESCRIPTION

[0019] The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be interpreted as a limitation of the present application.

[0020] For the purposes of the present application embodiments, the technical solutions and advantages, one or more embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a more thorough understanding of one or more embodiments. It is apparent, however, that one or more embodiments can be practiced without these specific details, and that each embodiment can include many of the same elements as other embodiments, and each embodiment can be used with any of the other embodiments.

[0021] It should be noted that the terms "first", "second" and the like in the description and in the claims of the present application and the above-described accompanying drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged, where appropriate, so that the embodiments of the present application described herein can be implemented in other than the order illustrated or described herein. Furthermore, the terms "comprise" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, processes, methods, systems, products, or devices that include a series of steps or units are not necessarily limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products, or devices. Also, the method of describing the positional relationship between structures using "vertical" and "parallel" is used herein, but in actual operation, it is difficult to achieve absolute "vertical" and "parallel", and here it should be allowed to have a certain degree of deviation. The description of the related angle relationship in the present application still has good effect when the deviation is not more than 3°, therefore, the "vertical" and "parallel" described throughout the text covers the case where the deviation is not more than 3°.

[0022] The diamond NV color center (Nitrogen-Vacancy Center, Nitrogen-Vacancy color center) is an atomic level defect in the diamond lattice, which is formed by a nitrogen atom (N) replacing a carbon atom and combining with an adjacent vacancy (V). It is one of the most concerned solid-state spin color center systems at present, because of its excellent quantum characteristics at room temperature, it has become the core platform of quantum sensing, quantum computing and quantum communication.

[0023] The core principle of ODMR (optically detected magnetic resonance) is to initialize the NV center spin state to the m_s=0 ground state by using green laser, and to apply adjustable microwave at the same time. When the microwave frequency precisely matches the energy level difference between the m_s=0 state and the m_s=±1 state, the microwave frequency is the center resonance frequency, and the NV center resonates and flips part of the spin to the m_s=±1 state. Since the red fluorescence intensity of the NV center in the m_s=0 state is significantly stronger than that in the m_s=±1 state, the fluorescence intensity detected at the resonance frequency will decrease. By scanning the microwave frequency and monitoring the decrease of the fluorescence intensity (i.e. the "resonance valley"), the size of the resonance frequency can be determined. At this time, under the action of the magnetic field, the m_s=±1 state will split into m_s=+1 state and m_s=-1 state, at this time, two groups of resonance frequencies symmetric about the center resonance frequency will be produced, and the difference between the two groups of frequencies is positively correlated with the external magnetic field. Obtaining the corresponding resonance frequency can accurately calculate the size of the external magnetic field. Embodiment one

[0024] Referring to the accompanying drawings Figure 1 As a basic scheme, a quantum magnetic probe includes a diamond block 1, a polarization maintaining single mode optical fiber 2 and a microwave radiator 3.

[0025] In this example, the diamond block 1 includes a first surface 100 and a second surface 101 perpendicular to the first surface 100. The diamond block 1 contains a system of NV centers (a large number of NV centers), and the first NV axis is perpendicular to the first surface 100. For a diamond block containing a system of NV centers, it has four NV axis directions. Based on the characteristics of the diamond lattice, the included angles between the four NV axis directions are equal, and the spatial positional relationship is as shown in the accompanying drawings. For the first NV axis, it can be any NV axis, such as the NV axis of the

[111] crystal direction, which is perpendicular to the first surface 100. It should be understood that the first surface 100 includes all parallel surfaces on the diamond block 1 that meet the conditions, such as the opposite surfaces of a cubic diamond block 1, both of which are first surfaces 100. Figure 2

[0026] Regarding the structure of the diamond block 1, this example does not make specific restrictions, but in an exemplary scheme, the diamond block 1 is preferably a cube or a cuboid, and the first surface 100 can be the top surface, and the second surface 101 can be the side surface. Regarding the size of the diamond block 1, since it needs to be connected with the optical fiber and ensure that the laser is fully excited, generally, its size is in the micron level, and in the accompanying drawings, the size relationship between the diamond block 1 and the polarization maintaining single mode optical fiber 2 is only for the convenience of display and illustration. In fact, in the basic scheme of embodiment one, the diamond block 1 is at most slightly larger than the end face diameter of the polarization maintaining single mode optical fiber 2, and more preferably, the size of the diamond block 1 is smaller than the end face diameter of the polarization maintaining single mode optical fiber 2, such as close to the diameter of the core. Figure 1

[0027] ​​In this case, the output end face of the polarization maintaining single-mode optical fiber 2 is fixedly connected with the second face 101 of the diamond block 1, and is configured to have a transmission main axis perpendicular to the first NV axial direction, as shown in Figure 3 The first NV axial direction is selected as the NV axial direction of the

[111] crystal direction, which is perpendicular to the first face 100, and the polarization maintaining single-mode optical fiber 2 is fixedly connected with the second face 101. As for the polarization maintaining single-mode optical fiber 2, it mainly realizes the polarization maintaining function based on the stress birefringence principle, and can be a panda fiber, a bowtie fiber, an elliptical cladding fiber, etc. The reason for selecting a single-mode fiber is that it has a single mode, which can avoid the change of the light field caused by the fiber dithering, and ensure the reliability of the sensing data.

[0028] For the fixed connection of the polarization maintaining single-mode optical fiber 2 and the diamond block 1, optical cement can be used for connection and fixation. The end face of the existing polarization maintaining single-mode optical fiber is marked with the direction of the transmission main axis, generally the slow axis. In this scheme, both the fast axis and the slow axis can be used as the transmission main axis of the polarization maintaining fiber.

[0029] We know that the polarization direction of the excitation light has a very important influence on the spin excitation efficiency of the nitrogen-vacancy color center of the diamond. For the excitation light with linear polarization direction, the excitation efficiency P of the nitrogen-vacancy color center satisfies: P= P 0* [sin 2 (α)+1 / 9*cos 2 (α)] In the formula, α is the polarization angle of the laser, and P0 is the total excitation rate of the nitrogen-vacancy color center when the polarization direction of the laser is aligned. From the above, it can be found that when α=90°, i.e. the polarization direction of the laser is perpendicular to the axial direction of the nitrogen-vacancy color center, the excitation efficiency P of the nitrogen-vacancy color center is the largest, and when φ=0°, the excitation efficiency P of the nitrogen-vacancy color center is only 1 / 9 of the vertical direction, and the laser excitation efficiency is the lowest.

[0030] Based on the above reasons, the transmission main axis of the polarization maintaining single-mode optical fiber 2 is perpendicular to the first NV axial direction, i.e. perpendicular or close to perpendicular, and the perpendicular state is preferred to realize high-efficiency excitation of the NV color center.

[0031] In order to facilitate understanding of how to achieve the perpendicularity of the transmission main axis and the first NV axis, in an example, we select the fast axis as the transmission main axis, and the normal of a face of the diamond block 1 is as parallel as possible to the first NV axis (e.g., the parallel deviation is less than or equal to 2°). When connected, the face contacts a relatively smooth base face, and the slow axis mark is perpendicular to the base face through the optical fiber fixing device. At this time, the slow axis is substantially parallel to the first NV axis, and the fast axis is perpendicular to the first NV axis. The connection and fixation of the two are realized through the optical glue. When working, we align the access of the external linearly polarized excitation light into the polarization maintaining single-mode optical fiber 2, and the linearly polarized excitation light is transmitted with the fast axis as the transmission main axis. The polarization maintaining linearly polarized excitation light is approximately perpendicular to the first NV axis, and the purpose of high-efficiency excitation is achieved.

[0032] We know that the diamond block 1 containing the ensemble NV color center has four NV axis directions, and the external magnetic field has a component in each NV axis direction. The design of the polarization angle can realize high-efficiency excitation of a specific NV axis direction, and further can more accurately obtain the spin resonance change caused by the magnetic field in the NV axis direction. That is, the measurement accuracy of the magnetic component in the NV axis direction is higher. This design is particularly suitable for the measurement of a magnetic field with a certain direction. When detecting the quantum magnetic probe using this design, the magnetic field direction can be parallel to the first NV axis. At this time, the NV color center of the first NV axis can fully perceive the external magnetic field. Combined with the ODMR measurement method, we can know that in this case, the corresponding peak has a higher bandwidth, and the tracking of the resonance frequency can improve the measurement accuracy.

[0033] In this example, the microwave radiator 3 is used to load the external microwave signal and radiate to the diamond block 1. The structure and type of the microwave radiator 3 are various, such as a spiral antenna, a microstrip antenna, a planar waveguide, and the like. In an example, a microstrip antenna is used as a planar radiator. The advantages are that it can provide more stable microwave signals, and can be used as a backing plate for mounting the diamond block 1 and the polarization maintaining single-mode optical fiber 2. As shown in the structure in FIG. 2, the diamond block can be fixed on the surface of the antenna through optical glue, or the front end of the polarization maintaining single-mode optical fiber 2 can be fixed with the antenna to improve the structural stability. Figure 1

[0034] Regarding the polarization maintaining optical fiber, we know that it has a fast axis and a slow axis. The fast axis has a low refractive index, fast light propagation, and low sensitivity to disturbance. The slow axis has a high refractive index, slow light propagation, and significant phase delay but is susceptible to interference. Combined with the characteristics of the present scheme, the transmission process of the optical fiber is prone to disturbance. Therefore, as an optional scheme, the transmission main axis selected by us is the fast axis of the polarization maintaining single-mode optical fiber.

[0035] ​In each scheme described in Example 1, there is no restriction on the collection method of the photoluminescence generated by the NV color center. We can collect the photoluminescence by reversely transmitting it through the polarization-maintaining single-mode fiber 2. For example, a dichroic plate is set between the laser source and the polarization-maintaining single-mode fiber 2. The excitation light can penetrate the dichroic plate, and the photoluminescence is reflected by the dichroic plate and received by the photodetector. In this design, the photodetector can be designed at the far end (i.e., close to the data processing side). In addition, in another design, we consider improving the integration of the quantum magnetic probe and choose to set the photodetection module near the diamond block 1 to collect the photoluminescence generated by the diamond block 1 through the spatial light transmission mode, as shown in the attached figure. Figure 4 As shown, the photoelectric detection module 4 is selected to be arranged above the top surface of the diamond block 1, wherein the photoelectric detection module 4 includes a filter device (not shown in the figure) for filtering stray light in the photoluminescence.

[0036] Further, in order to improve the collection efficiency of photoluminescence, see the attached Figure 4We have a first form of cured glue 1001 on the face of the diamond block 1 towards the photodetection module 4, which is used to gather photoluminescence. For the first form of cured glue 1001, as can be known from its function introduction, it is mainly used to gather photoluminescence. In theory, any structure form that can achieve this function is included in the so-called first form, such as a semi-spherical or approximately semi-spherical cured glue. When making, drop the liquid optical glue on the first face 100 and invert it. Control the curing time to form (also can be made by nano-imprinting scheme). For the design of the first form of cured glue 1001, it not only can improve the optical density of photoluminescence, but also we know that the NV color center is in the diamond block 1, which means that the photoluminescence is generated inside it and needs to be transmitted through the diamond block-air interface before it can be sensed by the photodetection module 4. The refractive index of diamond is much higher than that of air, so the photoluminescence will be reflected by total internal reflection at the interface, which will affect the collection of photoluminescence. In this example, the cured glue is used to replace the air as the interface with the diamond block 1. Since the refractive index of the cured glue is much higher than that of the air, this significantly weakens the loss of total internal reflection on the fluorescence, so more photoluminescence can pass through the diamond interface, thereby improving the fluorescence collection efficiency. For this purpose, in further design, the refractive index of the first form of cured glue 1001 is not less than 1.5, and the cured glue with a refractive index of about 1.7 is preferred. The quantum magnetic probe formed by the above structure is characterized by using a cured glue with light gathering function, which can gather the photoluminescence generated by the diamond block. The improvement of fluorescence optical density in ODMR measurement technology will significantly improve the measurement bandwidth and response speed. The bandwidth can improve the measurement accuracy, and the response speed improvement represents the improvement of the sampling rate. Compared with the existing fluorescence gathering lens, the manufacturing cost and difficulty of the cured glue are low, and it is easier to mass-produce. Moreover, it has a small volume and is suitable for small volume integration with other devices in a limited space.

[0037] In the foregoing design of the first form of cured glue 1001, the function of optical gathering is the main feature. In another perspective, we consider that the cured glue formed by part of the optical glue will also generate stray fluorescence under the irradiation of the excitation light. This part of the fluorescence has a wavelength close to that of photoluminescence and cannot be removed by the optical filter device, so it will affect the purity of photoluminescence. To optimize this problem, in a preferred design, the cured glue is required not to generate photoluminescence effect under the irradiation of the excitation light. Preferably, the cured glue material is glass or glass-like material, such as the cured product of hydrogen silsesquioxane photoresist (HSQ photoresist). Similar photoresists include polysiloxane photoresist or organosilane photoresist or polyimide photoresist or benzocyclobutene photoresist. This cured glue will not generate stray fluorescence under the irradiation of the excitation light, so it can effectively reduce the interference of stray fluorescence.

[0038] In the foregoing embodiment, the input linearly polarized excitation light is input by using a polarization maintaining optical fiber (PM fiber), which is effective, but when using the polarization maintaining optical fiber, accurate positioning and adjustment of the connection and splicing of the optical fiber are required to ensure the stability of the polarization state, which is a relatively complex process; as an alternative, it is proposed to replace the polarization maintaining single-mode optical fiber in the foregoing scheme with a polarization optical fiber (PZ fiber). The polarization optical fiber is a special optical fiber, in which only one polarization state of light can be and can only be propagated, similar to a polarized polarizer. When light of other polarization directions propagates therein, it will experience high optical loss and cannot continue to propagate in the optical fiber. The PZ fiber produces high birefringence effect through special design structure (such as bow tie type), which makes the light of a specific polarization direction propagate along the optical fiber, and the light of other polarization directions is subject to high optical loss and rapidly attenuates.

[0039] When connecting an external laser source with an optical fiber, the connection alignment process of the polarization optical fiber (PZ fiber) is obviously simpler than that of the polarization maintaining optical fiber (PM fiber), and the core difference lies in the difficulty of controlling the polarization direction.

[0040] The PM fiber connection laser includes the following difficulties: Polarization axis pre-calibration: a special device (such as a polarization controller) is required to adjust the laser output polarization state and match the PM fiber slow axis direction. If a polarization maintaining jumper is used, the jumper Key key direction must be consistent with the laser polarization direction (manual rotation error is difficult to control).

[0041] Dynamic stability challenge: temperature / vibration easily causes the aligned polarization axis to deviate (repeated calibration is required).

[0042] Verification complexity: the insertion loss (IL) and polarization extinction ratio (PER≥25dB) must be tested simultaneously, and the equipment cost is high (such as a polarization analyzer).

[0043] Advantages of PZ fiber connection laser: Polarization matching free: the laser can be directly incident without adjusting the polarization direction (such as Optiphase PZ1, which realizes phase modulation by stretching the optical fiber through a piezoelectric ceramic, and is independent of polarization).

[0044] Simplified process: the operation is close to that of ordinary single-mode optical fiber: focus the laser → inject into the core → optimize the coupling efficiency (only a power meter is required for monitoring).

[0045] Strong anti-interference: the multi-layer winding structure reduces the influence of environmental disturbance, and there is no need to continuously calibrate the polarization state.

[0046] As can be seen from the above, the use of PZ fiber can save the polarization matching step in the connection process with an external laser source, and the connection process is the same as that of ordinary optical fiber, and the efficiency is improved by 3-5 times.

[0047] As described above, the quantum magnetic probe, due to the high difficulty in aligning and connecting linearly polarized light with optical fibers, makes it difficult for external personnel to subsequently connect the laser to the quantum magnetic probe and control the measurement accuracy of the device. Therefore, in a preferred design, the quantum magnetic probe also includes a laser module, which is used to align the input linearly polarized excitation light to the input end face of the polarization-maintaining single-mode fiber 2. The two remain fixed after being pre-aligned and connected. Therefore, in subsequent use, only power needs to be supplied to the laser module, and no optical path adjustment is required, thus ensuring the connection stability of the polarization-maintaining fiber. The specific composition of the laser module is not limited in this example. The existing connection technology for laser modules and polarization-maintaining fibers is relatively mature. The main purpose of this example is to provide a quantum magnetic probe whose polarized light transmission can stably and efficiently act on NV color centers through a preset connection relationship. Example 2

[0048] The quantum magnetic probe introduced in Example 1 is particularly well-suited for directional magnetic field measurements. When using this design, the magnetic field can be aligned parallel to the axis of the first NV. The NV color center along the axis of the first NV can fully sense the external magnetic field. Combined with the ODMR measurement method, the corresponding peak has a higher bandwidth, and tracking its resonant frequency improves measurement accuracy.

[0049] Based on this, the second embodiment proposes a suitable application scenario and introduces a current measuring device, as shown in the attached Figure 5 and attached Figure 6 As shown, it has at least one quantum magnetic probe 7 as mentioned above, which is used to detect the current information in the conductor to be measured. It is also equipped with a magnetic ring 5, which is set outside the conductor to be measured 6. The quantum magnetic probe 7 is set in the magnetic air gap of the magnetic ring 5 and is configured so that the first NV axis (i.e., the

[111] crystal direction in the figure) is parallel to the magnetic field direction of the magnetic ring 5. The current measuring device is used to detect the magnetic field information generated by the current to be measured by reading the spin resonance related to the magnetic field information in the quantum magnetic probe 7, and then obtain the current information to be measured by reverse deduction through the magnetic field information. In the above design, the magnetic field component of the magnetic field in the first NV axis is the largest, and the components in the other three NV axes are equal (that is, the difference in the resonance frequency is equal, which is reflected in the ODMR. The peaks corresponding to the three axes are merged). The spectrum drawn based on the ODMR method has two pairs of peaks, as shown in the attached figure. Figure 7 As shown in Figure 1, the resonant frequency difference between the two outer peaks is positively correlated with the magnetic field magnitude along the

[111] NV axis (i.e., the first NV axis), while the resonant frequency difference between the two inner combined peaks is positively correlated with the magnetic field magnitudes along the other three NV axes. In practice, no matter which resonant frequency difference is obtained, the magnetic field data can be effectively inferred.

[0050] However, based on the characteristics of the aforementioned quantum magnetic probe, we know that the first NV axis is almost perpendicular to the polarization direction of the excitation light, so it can be excited most efficiently. Therefore, the independent spin resonance data related to the first NV axis will be more accurate. Based on this, this application also proposes a measurement method, which uses the current measurement device as described above. During measurement, it obtains independent spin resonance data related to the first NV axis (such as the two resonance frequencies of a pair of peaks on the outside), and calculates and obtains the current information to be measured based on the data.

[0051] In addition, experiments have shown that the linearity of NV centers with different axes in sensing magnetic fields is different. Figure 8 The eight oblique lines above correspond to the changing relationship between the resonant frequency and magnetic field of the eight peaks on the ODMR, and the upper and lower oblique lines correspond to the changing relationship between the outermost peak. It can be found that as the magnetic field changes, the oblique line maintains good linearity, that is, the corresponding relationship between the magnetic field and the resonant frequency difference is stable, while the six inner oblique lines will bend as the magnetic field increases, that is, the corresponding relationship between the magnetic field and the resonant frequency difference is unstable. Therefore, in some scenarios, such as large-range, high-precision current measurement scenarios, it is very effective to choose to track the resonant frequency of the outermost peak, which can maintain the linearity of the current measurement.

[0052] Considering that the bandwidth of the combined peak is larger, the identification or tracking of the resonance frequency is more accurate, and according to the attached Figure 8 It can be seen that within a certain range, it also has high linearity. When measuring small current (magnetic field), using the spin resonance data of the combined peak for current calculation will obtain higher accuracy. Therefore, in the design of this scheme, another measurement method is also introduced, which also uses the current measurement equipment as described above, but when measuring, it simultaneously obtains independent spin resonance data related to the first NV axis (such as the two resonance frequencies of a pair of peaks on the outside) and the combined spin resonance data of the other three directions of the NV axis (such as the two resonance frequencies of a pair of combined peaks on the inside). After obtaining the above data, this method uses different spin resonance data in different measurement intervals to calculate the current. Specifically: when the spin resonance data is less than the set value, the combined spin resonance data is used to calculate the current information to be measured; when the spin resonance data is greater than the set value, the independent spin resonance data is used to calculate the current information to be measured. Regarding the setting of the set value, combined with the attached Figure 8 We know that when the magnetic field magnitude in the non-first NV axis exceeds 6mT, the sensing linearity deteriorates. Therefore, in an exemplary solution, a magnetic field value of 6mT can be used as the set value, and the spin resonance data used for comparison should also be calculated and converted magnetic field data. It should be noted that the set value and spin resonance data are not limited to magnetic field data and can also be current data.

[0053] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "an example", "a specific example" or the like in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0054] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments. Obviously, many modifications and variations can be made in light of the contents of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A quantum magnetic probe, characterized in that: Include: - a diamond block comprising a first face and a second face perpendicular thereto, wherein the diamond block contains an ensemble NV color center, wherein the first NV axis of the diamond block is perpendicular to the first face; - a polarization-maintaining single-mode optical fiber, the output end face of which is fixedly bonded to the second face of the diamond block and is configured such that its transmission principal axis is perpendicular to the first NV axis; - A microwave radiator, wherein the diamond block is installed in a radiation zone of the microwave radiator.

2. The quantum magnetic probe according to claim 1, characterized in that The transmission main axis is the fast axis of the polarization-maintaining single-mode optical fiber.

3. The quantum magnetic probe according to claim 1, characterized in that The device further comprises a photoelectric detection module, which is arranged on the proximal side of the diamond block and is used for collecting the photoluminescence generated by the diamond block through a spatial light transmission mode.

4. The quantum magnetic probe according to claim 3, characterized in that A first form of curing glue is provided on the surface of the diamond block facing the photoelectric detection module, which is used to gather photoluminescence.

5. The quantum magnetic probe according to claim 4, characterized in that: The formed first-state cured adhesive does not generate a photoluminescence effect under the irradiation of excitation light.

6. The quantum magnetic probe according to claim 1, characterized in that The invention also comprises a laser module, which is used for inputting linearly polarized excitation light toward the input end face of the polarization-maintaining single-mode optical fiber.

7. The quantum magnetic probe according to claim 1, characterized in that The polarization-maintaining single-mode optical fiber is replaced by a polarization optical fiber.

8. A current measuring device for detecting current information in a conductor to be measured, characterized in that: Include: - having at least one quantum magnetic probe as claimed in any one of claims 1 to 7; - a magnetic focusing ring, which is sleeved over the current-carrying conductor to be measured, and the quantum magnetic probe is located in the magnetic focusing air gap of the magnetic focusing ring and is configured so that the first NV axis is parallel to the magnetic field direction of the magnetic focusing ring; The current measuring device is used to detect the magnetic field information generated by the current to be measured by reading the spin resonance related to the magnetic field information in the quantum magnetic probe, and then infer the current information to be measured through the magnetic field information.

9. A measurement method using the current measuring device according to claim 8, characterized in that: During measurement, independent spin resonance data related to the first NV axis is obtained, and current information to be measured is calculated based on the data.

10. A measurement method using the current measuring device according to claim 8, characterized in that: During measurement, independent spin resonance data related to the first NV axis and combined spin resonance data of the other three NV axes are simultaneously acquired; When the spin resonance data is less than a set value, the current information to be measured is obtained by calculating the combined spin resonance data; When the spin resonance data is greater than a set value, the current information to be measured is obtained by calculation using the independent spin resonance data.

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