Superconducting magnet residual magnetism measuring method, NV color center measuring system and electronic equipment

Abstract

The invention discloses a superconducting magnet residual magnetism measurement method, an NV color center measurement system and electronic equipment, and relates to the technical field of magnetic measurement. The method comprises the steps that a target application magnetic field of a preset size is applied to an NV color center through a superconducting magnet, and excitation energy is provided for the NV color center through an excitation module; changing the direction of the target applied magnetic field in a preset direction range, and monitoring a double-peak splitting value and a fluorescence contrast ratio of an ODMR spectrum in each direction; and according to the direction of the target applied magnetic field when the double-peak splitting value is maximum and the direction of the target applied magnetic field when the fluorescence contrast is maximum, obtaining the magnitude and direction of the residual magnetism of the superconducting magnet. Therefore, the residual magnetism of the superconducting magnet can be accurately measured, so that the accuracy and the reliability of NV measurement data can be guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of magnetic measurement, and in particular to a superconducting magnet residual magnetism measurement method, an NV color center measurement system and electronic equipment. BACKGROUND

[0002] The scanning nitrogen-vacancy (NV) color center probe microscope is a core tool for nanoscale magnetic measurement using the optical detection magnetic resonance (ODMR) technology of the NV color center. To perform vector magnetic field sensing or apply a directional bias field, such a system usually integrates a three-dimensional vector superconducting magnet.

[0003] After the superconducting magnet is excited by a large current and demagnetized, a stable residual magnetism (B0) exists due to the flux pinning effect of the non-ideal second superconductor. The residual magnetism causes the deviation in size and direction between the magnetic field (B1) intended to be applied by the operator and the resultant magnetic field (B=B0+B1) actually acting on the NV color center, thereby causing the following problems: 1) NV axis direction misjudgment: when initially calibrating the NV color center crystal axis direction, if the residual magnetism is not considered, the direction of the NV axis will be incorrectly identified; 2) fluorescence contrast quenching: when the bias magnetic field is applied based on the incorrect direction information, the actual resultant magnetic field direction has an angle with the NV axis, which will cause the fluorescence contrast of the ODMR spectrum to sharply decrease or even disappear, making the measurement impossible.

[0004] Currently, the accurate calibration of the residual magnetism inside the system faces the following technical bottlenecks: 1) the paradox of needing to calibrate the NV axis direction based on the magnetic field: to accurately calibrate the direction of the NV axis, the resultant magnetic field vector on the NV color center needs to be known, but the existence of the residual magnetism makes the resultant magnetic field actually unknown. To accurately calibrate the residual magnetism, the direction of the NV axis needs to be known. The traditional method attempts to calibrate under the premise of ignoring the residual magnetism or assuming it to be zero, which will inevitably introduce a large error in the actual superconducting magnet system; 2) lack of vector information: the traditional single NV color center single-point ODMR spectrum measurement can only obtain the magnetic field sizes parallel and perpendicular to the NV axis, but cannot obtain the direction of the perpendicular component, which is mathematically underdetermined; 3) low measurement accuracy: the method of calculating the perpendicular field size based on the double-peak position has very low sensitivity in theory, and in practice, it is also easily affected by local environment, temperature and noise interference, with large errors.

[0005] Therefore, there is an urgent need for a solution that can realize full-vector and high-precision residual magnetism measurement inside the system. SUMMARY

[0006] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application aims to provide a superconducting magnet residual magnetism measurement method, an NV color center measurement system and an electronic device to achieve accurate measurement of superconducting magnet residual magnetism, thereby ensuring the accuracy and reliability of NV measurement data.

[0007] In a first aspect, the present application provides a superconducting magnet residual magnetism measurement method, comprising the following steps: applying a target applied magnetic field of a preset size to an NV color center by a superconducting magnet, and providing excitation energy to the NV color center by an excitation module; changing the direction of the target applied magnetic field within a preset direction range, and monitoring the double-peak splitting value and fluorescence contrast of the ODMR spectrum under each direction; and obtaining the size and direction of the superconducting magnet residual magnetism according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum.

[0008] In a second aspect, the present application provides an NV color center measurement system, comprising: a superconducting magnet, an NV color center sensing unit, an excitation module, a detection module and a control module, wherein the NV color center sensing unit comprises an NV color center; and the control module is configured to: control the superconducting magnet to apply a target applied magnetic field of a preset size to the NV color center, and control the excitation module to provide excitation energy to the NV color center, and obtain an ODMR spectrum by the detection module; change the direction of the target applied magnetic field within a preset direction range, and monitor the double-peak splitting value and fluorescence contrast of the ODMR spectrum under each direction; and obtain the size and direction of the superconducting magnet residual magnetism according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum.

[0009] In a third aspect, the present application provides an electronic device comprising the NV color center measurement system of the second aspect.

[0010] The superconducting magnet residual magnetism measurement method, the NV color center measurement system and the electronic device of the present application can achieve accurate measurement of superconducting magnet residual magnetism, thereby ensuring the accuracy and reliability of NV measurement data. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1is a flow chart of a superconducting magnet residual magnetism measurement method of an embodiment of the present application; Figure 2 is a flow chart of step S3 of an embodiment of the present application; Figure 3 is a flow chart of step S31 of an embodiment of the present application; Figure 4 is a flow chart of step S32 of an embodiment of the present application; Figure 5 is a flow chart of step S3 of another embodiment of the present application; Figure 6 is a structural schematic diagram of an NV color center measurement system of an embodiment of the present application; Figure 7 is a structural schematic diagram of an electronic device of an embodiment of the present application. DETAILED DESCRIPTION

[0012] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar notations used throughout the drawings and the specific description denote the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0013] The superconducting magnet residual magnetism measurement method, the NV color center measurement system and the electronic device of the embodiments of the present application are described below with reference to the accompanying drawings.

[0014] Figure 1 is a flow chart of a superconducting magnet residual magnetism measurement method of an embodiment of the present application. The superconducting magnet residual magnetism measurement method can be executed by a host computer, a microprocessor, etc.

[0015] As shown in Figure 1 , the superconducting magnet residual magnetism measurement method comprises the following steps: S1, applying a target applied magnetic field of a preset size to the NV color center by the superconducting magnet, and providing excitation energy to the NV color center by an excitation module.

[0016] The excitation module comprises an optical excitation unit and a microwave excitation unit, the optical excitation unit is used to provide a light signal to polarize the spin state of the NV color center, and the microwave excitation unit is used to provide a microwave signal to drive the NV color center spin resonance transition.

[0017] It should be noted that the premise of the present application is that the superconducting magnet has been fully trained, i.e., the residual magnetism B 0 (including size and direction) is stable. The size of the applied magnetic field, i.e., the preset size, needs to ensure that the ODMR spectrum contrast of the NV color center does not completely disappear in any direction, which can be in the range of 10~100G. The superconducting magnet is a three-dimensional vector superconducting magnet.

[0018] S2, changing the direction of the target applied magnetic field in a preset direction range, and monitoring the doublet splitting value and the fluorescence contrast of the ODMR spectrum in each direction.

[0019] The preset direction range includes a preset pitch angle range (e.g., 0-180°) and a preset azimuth angle range (e.g., 0-180°).

[0020] In the first implementation, the changing of the direction of the applied magnetic field in the preset direction range and the monitoring of the doublet splitting value and the fluorescence contrast of the ODMR spectrum in each direction include: selecting an azimuth angle unchanged from the preset azimuth angle range, traversing the pitch angles in the preset pitch angle range as the direction of the applied magnetic field, and monitoring the doublet splitting value and the fluorescence contrast of the ODMR spectrum in each direction; determining a first pitch angle that maximizes the doublet splitting value and a second pitch angle that maximizes the fluorescence contrast; keeping the first pitch angle unchanged, traversing the azimuth angles in the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the doublet splitting value of the ODMR spectrum in each direction; and keeping the second pitch angle unchanged, traversing the azimuth angles in the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the fluorescence contrast of the ODMR spectrum in each direction.

[0021] In the second implementation, the changing of the direction of the applied magnetic field in the preset direction range and the monitoring of the doublet splitting value and the fluorescence contrast of the ODMR spectrum in each direction include: selecting an azimuth angle unchanged from the preset azimuth angle range, traversing the pitch angles in the preset pitch angle range as the direction of the applied magnetic field, and monitoring the doublet splitting value of the ODMR spectrum in each direction; determining a first pitch angle that maximizes the doublet splitting value, keeping the first pitch angle unchanged, traversing the azimuth angles in the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the doublet splitting value of the ODMR spectrum in each direction; and selecting an azimuth angle unchanged from the preset azimuth angle range, traversing the pitch angles in the preset pitch angle range as the direction of the applied magnetic field, and monitoring the fluorescence contrast of the ODMR spectrum in each direction; determining a second pitch angle that maximizes the fluorescence contrast, keeping the second pitch angle unchanged, traversing the azimuth angles in the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the fluorescence contrast of the ODMR spectrum in each direction.

[0022] The difference between this implementation and the previous implementation is that this implementation separately performs the traversal of the direction and the monitoring of the ODMR spectrum for the doublet splitting value and the fluorescence contrast, while the previous implementation shares the traversal of the pitch angle once. Compared with the previous implementation, the previous implementation can reduce the traversal of the pitch angle once.

[0023] In the third embodiment, the elevation angles (e.g., 180) in the preset elevation angle range and the azimuth angles (e.g., 180) in the preset azimuth angle range are grouped, each group containing one elevation angle and one azimuth angle, to obtain a group sequence (including 180x180 groups). Each group in the group sequence is traversed, and the corresponding elevation angle and azimuth angle are taken as the direction of the applied magnetic field, and the doublet splitting value and the fluorescence contrast of the ODMR spectrum in each direction are monitored.

[0024] Compared with the above-mentioned first and second embodiments, the third embodiment requires fewer times of applying magnetic fields and monitoring ODMR spectra.

[0025] S3, obtaining the magnitude and direction of the residual magnetism of the superconducting magnet according to the direction of the target applied magnetic field at which the doublet splitting value is maximum and the direction of the target applied magnetic field at which the fluorescence contrast is maximum.

[0026] In some embodiments, as shown in Figure 2 obtaining the magnitude and direction of the residual magnetism of the superconducting magnet according to the direction of the target applied magnetic field at which the doublet splitting value is maximum and the direction of the target applied magnetic field at which the fluorescence contrast is maximum, includes: S31, obtaining the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center, and the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center according to the direction of the target applied magnetic field at which the doublet splitting value is maximum and the direction of the target applied magnetic field at which the fluorescence contrast is maximum.

[0027] S32, obtaining the magnitude and direction of the residual magnetism of the superconducting magnet according to the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center, and the direction of the target applied magnetic field at which the fluorescence contrast is maximum.

[0028] Exemplarily, as shown in Figure 3 S31, includes: S311, obtaining the axial direction of the NV center according to the direction of the target applied magnetic field at which the doublet splitting value is maximum.

[0029] The direction of the target applied magnetic field at which the doublet splitting value is maximum can be the axial direction of the NV center.

[0030] S312, obtaining the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center according to the maximum value of the doublet splitting value and the magnitude of the target applied magnetic field.

[0031] The magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center can be obtained by subtracting the magnitude of the target applied magnetic field from the magnetic field strength corresponding to the maximum value of the doublet splitting value.

[0032] S313, obtaining the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center according to the direction of the target applied magnetic field, the axis of the NV center, and the size of the target applied magnetic field, or obtaining the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center according to the size of the target applied magnetic field, the double-peak splitting value when the fluorescence contrast is maximum, and the magnetic field component of the superconducting magnet remanence in the direction parallel to the axis of the NV center.

[0033] The obtaining of the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center according to the direction of the target applied magnetic field, the axis of the NV center, and the size of the target applied magnetic field can include: obtaining the included angle a between the direction of the target applied magnetic field and the axis of the NV center when the fluorescence contrast is maximum according to the direction of the target applied magnetic field and the axis of the NV center; and the size of the target applied magnetic field multiplied by cos a is the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center.

[0034] The obtaining of the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center according to the size of the target applied magnetic field, the double-peak splitting value when the fluorescence contrast is maximum, and the magnetic field component of the superconducting magnet remanence in the direction parallel to the axis of the NV center can include: subtracting the magnetic field component of the superconducting magnet remanence in the direction parallel to the axis of the NV center from the magnetic field intensity corresponding to the double-peak splitting value when the fluorescence contrast is maximum to obtain the magnetic field component of the target applied magnetic field in the direction parallel to the axis of the NV center when the fluorescence contrast is maximum; subtracting the square of the magnetic field component of the target applied magnetic field in the direction parallel to the axis of the NV center when the fluorescence contrast is maximum from the square of the size of the target applied magnetic field, and the square root of the result is the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center.

[0035] As shown in FIG. 32, Figure 4 S32 includes: S321, the ratio of the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center to the magnetic field component of the superconducting magnet remanence in the direction parallel to the axis of the NV center is the included angle β between the axis of the NV center and the direction of the superconducting magnet remanence.

[0036] S322, according to the coplanar of the axis of the NV center, the direction of the target applied magnetic field when the fluorescence contrast is maximum, and the direction of the superconducting magnet remanence, and the axis of the NV center being located between the direction of the target applied magnetic field when the fluorescence contrast is maximum and the direction of the superconducting magnet remanence, the direction of the superconducting magnet remanence is determined by the included angle β.

[0037] S323, the vector sum of the magnetic field component of the superconducting magnet remanence in the direction parallel to the axis of the NV center and the magnetic field component of the superconducting magnet remanence in the direction perpendicular to the axis of the NV center is the size of the superconducting magnet remanence.

[0038] In some embodiments, as shown in FIG. 1, the direction of the target applied magnetic field when the doublet splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum, are used to obtain the magnitude and direction of the superconducting magnet remanence, including: Figure 5 S33, determining the axial direction of the NV color center according to the direction of the target applied magnetic field when the doublet splitting value is maximum.

[0039] S34, determining the vector of the target applied magnetic field when the fluorescence contrast is maximum according to the direction of the target applied magnetic field when the fluorescence contrast is maximum, and the magnitude of the target applied magnetic field.

[0040] S35, determining the vector of the resultant magnetic field of the target applied magnetic field and the superconducting magnet remanence when the fluorescence contrast is maximum according to the doublet splitting value when the fluorescence contrast is maximum, and the axial direction of the NV color center.

[0041] S36, subtracting the vector of the target applied magnetic field when the fluorescence contrast is maximum from the vector of the resultant magnetic field, to obtain the vector of the superconducting magnet remanence.

[0042] It should be noted that when in a magnetic field, the ODMR spectrum of the NV color center will change in two key characteristics (i.e. doublet splitting value and fluorescence contrast), so the information of the magnetic field in which the NV color center is located can be inferred based on these two characteristics. However, when a magnetic field is applied in an environment with remanence, the maximum values of these two characteristics may be separated (i.e. their extreme values correspond to different directions of the external magnetic field). Based on this, the superconducting magnet remanence measurement method of the embodiments of the present application is to actively apply a small magnetic field with a known size and systematically adjust its direction under the premise that the superconducting magnet has been fully "trained" (i.e. its remanence remains constant), and observe the extreme value changes of the doublet splitting value and the fluorescence contrast of the ODMR spectrum of the NV color center, so as to inversely calculate the accurate remanence vector information, thereby ensuring the accuracy and reliability of subsequent NV measurement data.

[0043] Optionally, the maximum fluorescence contrast, the maximum doublet splitting value, and the maximum value of the doublet splitting value can be directly obtained based on the traversal results in the above three implementation manners, or can be obtained based on the fitted curve after the traversal results are fitted.

[0044] The following embodiments are described based on the second implementation manner, the fitted curve, and Figure 5 The superconducting magnet remanence measurement method of the embodiments of the present application is described based on the above-described second implementation manner, the fitted curve, and

[0045] In this example, the superconducting magnet remanence measurement method can be divided into the following two stages: Stage one: determining the axial direction of the NV color center 1) applying a target applied magnetic field with a preset size; ​The NV color center probe is placed at the sample point, and a target magnetic field of a predetermined size is applied using a superconducting magnet. The initial direction is arbitrary.

[0046] 2) Optimize the loop: Traverse the directions to maximize the bimodal splitting value of the ODMR spectrum and obtain the accurate axial direction of the NV color center. Specifically, this may include the following steps: S2.1: Maintain The magnitude remains unchanged, and the pitch angle of the target's applied magnetic field direction is adjusted during the traversal. The bimodal splitting value of the ODMR spectrum is monitored in real time, and the maximum bimodal splitting value is determined by extreme value fitting. ; S2.2: Maintain Size and The azimuth angle of the applied magnetic field direction to the target remains unchanged. Similarly, the method of extreme value fitting is used to determine the value that maximizes the bimodal splitting. ; S2.3: Steps S2.1 to S2.2 can be repeated one or more times to obtain the direction ( , ) is the axis of the true NV color center, denoted as ( , ).

[0047] For example, with a step size of 2°, in (0°~180°) and The scanning range is 0° to 180°. ODMR spectra are acquired at each point, and the algorithm automatically calculates the bimodal splitting value Δf.

[0048] By fitting the curve of the relationship between Δf and angle, we can find the value corresponding to the maximum value of the bimodal splitting ( ). , And record it. The curve fitting formula can be: and , Electron gyromagnetic ratio, , For redundant fitting parameters, Apply a magnetic field to the target Size.

[0049] Phase Two: Determining the Vector of Remanence in Superconducting Magnets 3) Optimize the loop: Traverse the directions to determine the direction in which the magnetic field is applied to the target when the fluorescence contrast is maximized; specifically, this may include the following steps: S3.1: Maintain The size remains unchanged, and starting from the current direction, the pitch angle is adjusted iteratively. Real-time monitoring of the fluorescence contrast of the ODMR spectrum, and determination of the maximum fluorescence contrast through extreme value fitting. ; S3.2: Maintain Size and The azimuth angle of the applied magnetic field direction to the target remains unchanged. The method of finding the maximum fluorescence contrast is determined by extreme value fitting. .

[0050] S3.3: Steps S3.1 to S3.2 can be repeated one or more times. direction ( , ) is denoted as ( , For example, from ( , Starting in the direction of ) and scanning in 2° increments. and The optimization target is fluorescence contrast ratio C.

[0051] By recording and fitting the data, we can find the direction that maximizes C. , And record it. The curve fitting formula can be: and ,in , These are redundant fitting parameters.

[0052] 4) Read the bimodal splitting value of the ODMR spectrum to obtain the magnitude of the synthetic magnetic field; Specifically, it reads in the direction ( , The bimodal splitting value of the ODMR spectrum is used to calculate the magnitude of the synthetic magnetic field B. total Specifically, you can refer to the formula. calculate.

[0053] 5) Vector operations are used to obtain remanence.

[0054] Vector solution: B0 = B - B1, where the size of B is B total The direction is ( , The magnitude of B1 is known, and its direction is ( ). , Therefore, the magnitude and direction of the remanence B0 are obtained. , ).

[0055] In some examples, when obtaining remanence BAfter B0, the vector information of B0 can be stored. After that, when the superconducting magnet needs to apply a target magnetic field B target , the B applied = B target - B 0, the precise compensation is realized, and the actual magnetic field to be applied B applied .

[0056] Figure 6 is a structural schematic diagram of the NV color center measurement system of the embodiment of the application.

[0057] As Figure 6 shown, the NV color center measurement system 600 comprises a superconducting magnet 1, an NV color center sensing unit 2, an excitation module 3, a detection module 4 and a control module 5. The superconducting magnet 1 is used to generate a controllable active magnetic field, and the NV color center sensing unit 2 comprises an NV color center probe for providing an NV color center.

[0058] The control module 5 is connected with the superconducting magnet 1, the excitation module 3 and the detection module 4 respectively, and is specially programmed to form a closed-loop automatic control system, which is used to: control the superconducting magnet 1 to apply a target applied magnetic field with a preset size to the NV color center, control the excitation module 2 to provide excitation energy to the NV color center, and acquire an ODMR spectrum through the detection module 3; change the direction of the target applied magnetic field in a preset direction range, and monitor the double-peak splitting value and the fluorescence contrast of the ODMR spectrum in each direction; and obtain the size and direction of the superconducting magnet remanence according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum.

[0059] Exemplarily, the excitation module 3 comprises an optical excitation unit and a microwave excitation unit, the optical excitation unit is used to provide an optical signal to polarize the spin state of the NV color center, and the microwave excitation unit is used to provide a microwave signal to drive the spin resonance transition of the NV color center.

[0060] Optionally, the excitation module 3 and the detection module 4 can be integrally arranged.

[0061] It should be noted that other specific embodiments of the NV color center measurement system 600 of the embodiment of the application can refer to the specific embodiments of the measurement method of the superconducting magnet remanence of the above-mentioned embodiment.

[0062] Figure 7 is a structural block diagram of the electronic device of the embodiment of the application.

[0063] As Figure 7 shown, the electronic device 700 comprises the NV color center measurement system 600 of the above-mentioned embodiment.

[0064] Specifically, the NV color center measurement system 600 with residual magnetism self-calibration function is deeply integrated with hardware and specific control logic, and constitutes a dedicated electronic device 700 as a measurement tool.

[0065] In summary, the superconducting magnet residual magnetism measurement method, the NV color center measurement system and the electronic device have the following beneficial effects: 1) Breakthrough technical bottleneck: successfully solve the two big problems of "unknown direction of vertical component" and "inaccurate measurement of vertical component size" in traditional NV magnetic measurement; 2) Precision order of magnitude leap: through "extreme value search" instead of "absolute value measurement", using multiple data points fitting, realizing the super-resolution positioning of angle, the precision is much higher than that of traditional method; 3) Strong operability and reliability: the flowchart steps are easy to complete automatically, the results are stable and reliable, and it is easy to complete automatically under computer control, realizing "one-key calibration".

[0066] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered a list of executable instructions for implementing logic functions, and can be specifically embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, a system including a processor, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. For the purposes of this specification, a "computer-readable medium" can be any apparatus that can contain, store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of the computer-readable medium include the following: an electrical connection having one or more wires (electronic devices), a portable computer diskette (magnetic devices), a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disc read-only memory (CD ROM). In addition, the computer-readable medium can even be paper or other suitable medium on which the program can be printed, because the program can be electronically obtained, for example, by optical scanning of the paper or other medium, followed by editing, interpretation, or necessary processing, if necessary, in other suitable ways, and then stored in the computer memory.

[0067] It should be understood that aspects of the application can be implemented in hardware, software, firmware or combinations thereof. In the embodiments described above, various steps or methods can be implemented, for example, through software or firmware in storage media which are executable by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, any of the following technologies, known in the art, or their combinations, can be employed: discrete logic circuitry having logic gates for implementing logic functions upon an application of data signals, application-specific integrated circuits having appropriate combinational logic gates, programmable gate arrays (PGA), field-programmable gate arrays (FPGA), and so on.

[0068] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are contained in at least one embodiment or example of the present application. In the present description, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0069] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application.

[0070] In addition, the terms "first", "second" are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0071] In the present application, unless specifically defined otherwise, the terms "mounting", "connected", "connecting", "fixed", and the like should be construed in a broad sense, for example, can be fixed connection, can also be detachable connection, or integral; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship of two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0072] In the present application, unless specifically defined otherwise, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The first feature "below", "under" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0073] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A method of measuring remanence of a superconducting magnet, characterized by, The method comprises the following steps: applying a target applied magnetic field with a preset size to the NV center by a superconducting magnet, and providing excitation energy to the NV center by an excitation module; changing the direction of the target applied magnetic field within a preset direction range, and monitoring the double-peak splitting value and fluorescence contrast of the ODMR spectrum under each direction; obtaining the size and direction of the residual magnetism of the superconducting magnet according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum.

2. The method of measuring remanence of a superconducting magnet according to claim 1, wherein, The method for obtaining the size and direction of the residual magnetism of the superconducting magnet according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum comprises: obtaining the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center, and the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum; obtaining the size and direction of the residual magnetism of the superconducting magnet according to the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center, and the direction of the target applied magnetic field when the fluorescence contrast is maximum.

3. The method of claim 2, wherein the magnetic field is applied in a direction parallel to the axis of the superconducting magnet. The method for obtaining the axial direction of the NV center, the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center, and the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center according to the direction of the target applied magnetic field when the double-peak splitting value is maximum, and the direction of the target applied magnetic field when the fluorescence contrast is maximum comprises: obtaining the axial direction of the NV center according to the direction of the target applied magnetic field when the double-peak splitting value is maximum; obtaining the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center according to the maximum value of the double-peak splitting value and the size of the target applied magnetic field; obtaining the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center according to the direction of the target applied magnetic field when the fluorescence contrast is maximum, the axial direction of the NV center, and the size of the target applied magnetic field, or obtaining the magnetic field component of the residual magnetism of the superconducting magnet perpendicular to the axial direction of the NV center according to the size of the target applied magnetic field, the double-peak splitting value when the fluorescence contrast is maximum, and the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center.

4. The method of claim 3, wherein the magnetic field is applied in a direction parallel to the axis of the superconducting magnet. The method for obtaining the axial direction of the NV center according to the direction of the target applied magnetic field when the double-peak splitting value is maximum comprises: the direction of the target applied magnetic field when the double-peak splitting value is maximum is the axial direction of the NV center.

5. The method of claim 3, wherein the magnetic field is applied in a direction parallel to the axis of the superconducting magnet. The method for obtaining the magnetic field component of the residual magnetism of the superconducting magnet parallel to the axial direction of the NV center according to the maximum value of the double-peak splitting value and the size of the target applied magnetic field comprises: The magnetic field strength corresponding to the maximum of the double-peak splitting value minus the size of the target applied magnetic field is the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center.

6. The method of claim 3, wherein the step of measuring the residual magnetic field of the superconducting magnet is performed by a method comprising: According to the direction of the target applied magnetic field when the fluorescence contrast is maximum, the axial direction of the NV center, and the size of the target applied magnetic field, the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center is obtained, including: According to the axial direction of the NV center and the axial direction of the superconducting magnet remanence, the angle α between the direction of the target applied magnetic field when the fluorescence contrast is maximum and the axial direction of the NV center is obtained. The size of the target applied magnetic field multiplied by cosα is the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center.

7. The method for measuring the remanence of a superconducting magnet according to claim 3, characterized in that, According to the size of the target applied magnetic field, the double-peak splitting value when the fluorescence contrast is maximum, and the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center, the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center is obtained, including: The magnetic field strength corresponding to the double-peak splitting value when the fluorescence contrast is maximum minus the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center is the magnetic field component of the target applied magnetic field in the axial direction parallel to the NV center when the fluorescence contrast is maximum. The square root of the result of subtracting the square of the magnetic field component of the target applied magnetic field in the axial direction parallel to the NV center when the fluorescence contrast is maximum from the square of the size of the target applied magnetic field is the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center.

8. The method of claim 2, wherein, According to the axial direction of the NV center, the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center, the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center, and the direction of the target applied magnetic field when the fluorescence contrast is maximum, the size and direction of the superconducting magnet remanence are obtained, including: The ratio of the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center to the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center is the angle β between the axial direction of the NV center and the direction of the superconducting magnet remanence. According to the axial direction of the NV center, the direction of the target applied magnetic field when the fluorescence contrast is maximum, and the direction of the superconducting magnet remanence, the direction of the superconducting magnet remanence is determined by the angle β, and the axial direction of the NV center is located between the direction of the target applied magnetic field when the fluorescence contrast is maximum and the direction of the superconducting magnet remanence. The vector sum of the magnetic field component of the superconducting magnet remanence in the axial direction parallel to the NV center and the magnetic field component of the superconducting magnet remanence in the axial direction perpendicular to the NV center is the size of the superconducting magnet remanence.

9. The method of claim 1, wherein, The preset direction range includes a preset pitch angle range and a preset azimuth angle range. The method comprises: selecting an azimuth angle from the preset azimuth angle range and traversing the preset elevation angle range as the direction of the applied magnetic field, and monitoring the double-peak splitting value and the fluorescence contrast of the ODMR spectrum under each direction; determining a first elevation angle that maximizes the double-peak splitting value and a second elevation angle that maximizes the fluorescence contrast; traversing the preset azimuth angle range as the direction of the applied magnetic field while keeping the first elevation angle unchanged, and monitoring the double-peak splitting value of the ODMR spectrum under each direction; traversing the preset azimuth angle range as the direction of the applied magnetic field while keeping the second elevation angle unchanged, and monitoring the fluorescence contrast of the ODMR spectrum under each direction.

10. The method of claim 9, wherein the magnetic field is applied in a direction parallel to the axis of the superconducting magnet. According to the direction of the target applied magnetic field when the double-peak splitting value is maximum and the direction of the target applied magnetic field when the fluorescence contrast is maximum, the size and direction of the superconducting magnet residual magnetism are obtained, comprising: determining the axial direction of the NV center according to the direction of the target applied magnetic field when the double-peak splitting value is maximum; determining the vector of the target applied magnetic field when the fluorescence contrast is maximum according to the direction of the target applied magnetic field when the fluorescence contrast is maximum and the size of the target applied magnetic field; determining the vector of the resultant magnetic field of the target applied magnetic field and the superconducting magnet residual magnetism when the fluorescence contrast is maximum according to the double-peak splitting value when the fluorescence contrast is maximum and the axial direction of the NV center; The vector of the resultant magnetic field minus the vector of the target applied magnetic field when the fluorescence contrast is maximum is the vector of the superconducting magnet residual magnetism.

11. An NV color center measurement system, comprising: The system comprises a superconducting magnet, an NV center sensing unit, an excitation module, a detection module, and a control module, wherein the NV center sensing unit comprises an NV center. The control module is configured to: control the superconducting magnet to apply a target applied magnetic field with a preset size to the NV center, control the excitation module to provide excitation energy to the NV center, and acquire an ODMR spectrum through the detection module; change the direction of the target applied magnetic field within a preset direction range, and monitor the double-peak splitting value and the fluorescence contrast of the ODMR spectrum under each direction; According to the direction of the target applied magnetic field when the double-peak splitting value is maximum and the direction of the target applied magnetic field when the fluorescence contrast is maximum, the size and direction of the superconducting magnet residual magnetism are obtained.

12. An electronic device, comprising: The method comprises: The NV center measurement system of claim 11.

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