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 following steps: applying a magnetic field with a preset size to an NV color center through a superconducting magnet, and providing excitation energy to the NV color center through an excitation module; changing the direction of applying the magnetic field in a preset direction range, and monitoring a double-peak splitting value and a fluorescence contrast ratio of the optical detection magnetic resonance spectrum in each direction; obtaining the direction of a target resultant magnetic field according to the double-peak splitting value, obtaining the direction of a target applied magnetic field according to the fluorescence contrast, and obtaining the size of the target resultant magnetic field according to the fluorescence contrast and the double-peak splitting value; and according to the size and direction of the target resultant magnetic field and the size and direction of the target applied magnetic field, obtaining the size 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] This invention aims to at least partially solve one of the technical problems in related technologies. Therefore, the objective of this invention is to propose a method for measuring the remanence of superconducting magnets, an NV color center measurement system, and electronic equipment to achieve accurate measurement of the remanence of superconducting magnets, thereby ensuring the accuracy and reliability of NV measurement data.

[0007] In a first aspect, embodiments of the present invention propose a method for measuring the remanence of a superconducting magnet, comprising the following steps: applying a magnetic field of a preset magnitude to an NV color center through a superconducting magnet, and providing excitation energy to the NV color center through an excitation module; changing the direction of the applied magnetic field within a preset directional range, and monitoring the bipeak splitting value and fluorescence contrast of the ODMR spectrum in each direction; obtaining the direction of the target combined magnetic field based on the bipeak splitting value, obtaining the direction of the target applied magnetic field based on the fluorescence contrast, and obtaining the magnitude of the target combined magnetic field based on the fluorescence contrast and the bipeak splitting value, wherein the target combined magnetic field is the combined magnetic field of the target applied magnetic field and the remanence of the superconducting magnet, and the direction of the target combined magnetic field is parallel to the NV axis of the NV color center; obtaining the magnitude and direction of the remanence of the superconducting magnet based on the magnitude and direction of the target combined magnetic field and the magnitude and direction of the target applied magnetic field.

[0008] In some embodiments, the preset direction range includes a preset pitch angle range and a preset azimuth angle range; the step of changing the direction of the applied magnetic field within the preset direction range and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction includes: selecting one azimuth angle from the preset azimuth angle range and keeping it constant, traversing the pitch angles within the preset pitch angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; determining a first pitch angle that maximizes the bimodal splitting value and a second pitch angle that maximizes the fluorescence contrast; keeping the first pitch angle constant, traversing the azimuth angles within the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value of the ODMR spectrum in each direction; keeping the second pitch angle constant, traversing the azimuth angles within 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.

[0009] In some embodiments, the step of obtaining the direction of the target resultant magnetic field based on the bimodal splitting value, obtaining the direction of the target applied magnetic field based on the fluorescence contrast, and obtaining the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value includes: determining a first azimuth angle that maximizes the bimodal splitting value; using the direction determined by the first pitch angle and the first azimuth angle as the direction of the target resultant magnetic field; determining a second azimuth angle that maximizes the fluorescence contrast; using the direction determined by the second pitch angle and the second azimuth angle as the direction of the target applied magnetic field, and obtaining the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

[0010] In some embodiments, obtaining the direction of the target combined magnetic field based on the bimodal splitting value, obtaining the direction of the target applied magnetic field based on the fluorescence contrast, and obtaining the magnitude of the target combined magnetic field based on the fluorescence contrast and the bimodal splitting value include: performing curve fitting on the bimodal splitting value of the ODMR spectrum at each elevation angle, the bimodal splitting value of the ODMR spectrum at each azimuth angle, the fluorescence contrast of the ODMR spectrum at each elevation angle, and the fluorescence contrast of the ODMR spectrum at each azimuth angle; using the direction determined by the third elevation angle corresponding to the maximum bimodal splitting value in the fitted bimodal splitting value-elevation angle curve and the third azimuth angle corresponding to the maximum bimodal splitting value in the bimodal splitting value-azimuth angle curve as the direction of the target combined magnetic field; using the direction determined by the fourth elevation angle corresponding to the maximum fluorescence contrast in the fitted fluorescence contrast-elevation angle curve and the fourth azimuth angle corresponding to the maximum fluorescence contrast in the fluorescence contrast-azimuth angle curve as the direction of the target applied magnetic field; and obtaining the magnitude of the target combined magnetic field based on the bimodal splitting value corresponding to the fourth elevation angle and the fourth azimuth angle.

[0011] In some embodiments, the steps of changing the direction of the applied magnetic field within a preset directional range and monitoring the bipeak splitting value and fluorescence contrast of the ODMR spectrum in each direction are performed once or multiple times.

[0012] Secondly, embodiments of the present invention propose an NV color center measurement system, the system comprising: a superconducting magnet, an NV color center sensing unit, an excitation module, a detection module, and a control module. The NV color center sensing unit includes NV color centers. The control module is used to: control the superconducting magnet to apply a magnetic field of a preset magnitude to the NV color center, control the excitation module to provide excitation energy to the NV color center, and acquire an ODMR spectrum through the detection module; change the direction of the applied magnetic field within a preset directional range, and monitor the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; obtain the direction of the target combined magnetic field based on the bimodal splitting value, obtain the direction of the target applied magnetic field based on the fluorescence contrast, and obtain the magnitude of the target combined magnetic field based on the fluorescence contrast and the bimodal splitting value, wherein the target combined magnetic field is the combined magnetic field of the target applied magnetic field and the remanence of the superconducting magnet, and the direction of the target combined magnetic field is parallel to the NV axis of the NV color center; and obtain the magnitude and direction of the remanence of the superconducting magnet based on the magnitude and direction of the target combined magnetic field and the magnitude and direction of the target applied magnetic field.

[0013] In some embodiments, the preset direction range includes a preset pitch angle range and a preset azimuth angle range; when the control module changes the direction of the applied magnetic field within the preset direction range and monitors the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction, it is specifically configured to: select one azimuth angle from the preset azimuth angle range and keep it constant; traverse the pitch angles within the preset pitch angle range as the direction of the applied magnetic field and monitor the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; determine a first pitch angle that maximizes the bimodal splitting value and a second pitch angle that maximizes the fluorescence contrast; keep the first pitch angle constant and traverse the azimuth angles within the preset azimuth angle range as the direction of the applied magnetic field and monitor the bimodal splitting value of the ODMR spectrum in each direction; keep the second pitch angle constant and traverse the azimuth angles within the preset azimuth angle range as the direction of the applied magnetic field and monitor the fluorescence contrast of the ODMR spectrum in each direction.

[0014] In some embodiments, when the control module obtains the direction of the target resultant magnetic field based on the bimodal splitting value, obtains the direction of the target applied magnetic field based on the fluorescence contrast, and obtains the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value, it is specifically configured to: determine a first azimuth angle that maximizes the bimodal splitting value; take the direction determined by the first pitch angle and the first azimuth angle as the direction of the target resultant magnetic field; determine a second azimuth angle that maximizes the fluorescence contrast; take the direction determined by the second pitch angle and the second azimuth angle as the direction of the target applied magnetic field, and obtain the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

[0015] In some embodiments, the control module is further configured to: store the magnitude and direction of the remanence of the superconducting magnet; and / or compensate for the target magnetic field in applications where a target magnetic field needs to be applied through the superconducting magnet.

[0016] Thirdly, embodiments of the present invention provide an electronic device including the NV color center measurement system described in the second aspect embodiment.

[0017] The superconducting magnet remanence measurement method, NV center measurement system, and electronic device of this invention, in measuring the remanence of a superconducting magnet, firstly apply a magnetic field of a preset magnitude to the NV center through the superconducting magnet, and provide excitation energy to the NV center through an excitation module; then, change the direction of the applied magnetic field within a preset directional range, and monitor the bipeak splitting value and fluorescence contrast of the ODMR spectrum in each direction; then, obtain the magnitude and direction of the target resultant magnetic field based on the bipeak splitting value, and obtain the direction of the target applied magnetic field based on the fluorescence contrast, wherein the target resultant magnetic field is the combined magnetic field of the target applied magnetic field and the superconducting magnet remanence, and the direction of the target resultant magnetic field is parallel to the NV axis of the NV center; finally, obtain the magnitude and direction of the superconducting magnet remanence based on the magnitude and direction of the target resultant magnetic field and the magnitude and direction of the target applied magnetic field. Therefore, accurate measurement of the superconducting magnet remanence can be achieved, thereby ensuring the accuracy and reliability of NV measurement data. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for measuring the remanence of a superconducting magnet according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the ODMR spectrum of an NV color center according to an embodiment of the present invention; Figure 3 This is a flowchart of a method for measuring the remanence of a superconducting magnet, as an example of the present invention. Figure 4 This is a fitting curve diagram of a local magnetic field traversal test in an example of the present invention. Figure 5 This is a schematic diagram of vector relationships according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the NV color center measurement system according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0019] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0020] The following description, with reference to the accompanying drawings, describes a method for measuring the remanence of a superconducting magnet, an NV color center measurement system, and an electronic device according to embodiments of the present invention.

[0021] Figure 1 This is a flowchart of a method for measuring the remanence of a superconducting magnet according to an embodiment of the present invention. This method for measuring the remanence of a superconducting magnet can be executed by a host computer, microprocessor, or the like.

[0022] like Figure 1 As shown, the method for measuring the remanence of a superconducting magnet includes the following steps: S1 applies a magnetic field of a preset size to the NV color center through a superconducting magnet and provides excitation energy to the NV color center through an excitation module.

[0023] The excitation module includes 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 resonant transition of the NV color center.

[0024] It should be noted that the implementation of this invention is premised on the superconducting magnet having undergone sufficient training, i.e., remanence. B 0 (including magnitude and direction) stability. The magnitude of the applied magnetic field, i.e., the preset magnitude, must ensure that the ODMR spectral contrast of the NV color center will not completely disappear in any direction; a value within the range of 10~100G is acceptable. The superconducting magnet is a three-dimensional vector superconducting magnet.

[0025] S2, change the direction of the applied magnetic field within a preset directional range, and monitor the bipeak splitting value and fluorescence contrast of the ODMR spectrum in each direction.

[0026] The preset direction range includes a preset pitch angle range (e.g., 0~180°) and a preset azimuth angle range (e.g., 0~180°).

[0027] In the first embodiment, changing the direction of the applied magnetic field within a preset directional range and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction includes: selecting one azimuth angle from a preset azimuth angle range and keeping it constant, traversing the elevation angles within a preset elevation angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; determining a first elevation angle that maximizes the bimodal splitting value and a second elevation angle that maximizes the fluorescence contrast; keeping the first elevation angle constant, traversing the azimuth angles within the preset azimuth angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value of the ODMR spectrum in each direction; keeping the second elevation angle constant, traversing the azimuth angles within 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.

[0028] In the second embodiment, the direction of the applied magnetic field is changed within a preset directional range, and the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction are monitored. This includes: selecting one azimuth angle from a preset azimuth angle range and keeping it constant, traversing the elevation angles within a preset elevation angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value of the ODMR spectrum in each direction; determining a first elevation angle that maximizes the bimodal splitting value, keeping the first elevation angle constant, traversing the azimuth angles within a preset azimuth angle range as the direction of the applied magnetic field, and monitoring the bimodal splitting value of the ODMR spectrum in each direction; selecting one azimuth angle from a preset azimuth angle range and keeping it constant, traversing the elevation angles within a preset elevation 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 elevation angle that maximizes the fluorescence contrast, keeping the second elevation angle constant, traversing the azimuth angles within a preset azimuth angle range as the direction of the applied magnetic field, and monitoring the fluorescence contrast of the ODMR spectrum in each direction.

[0029] The difference between this embodiment and the previous embodiment is that this embodiment performs traversal of directions and monitoring of ODMR spectra separately for bimodal splitting values ​​and fluorescence contrast, while the previous embodiment uses only one traversal of the pitch angle. Compared to the previous embodiment, this embodiment reduces one traversal of the pitch angle.

[0030] In the third embodiment, the pitch angles within a preset pitch angle range (e.g., 180) and the azimuth angles within a preset azimuth angle range (e.g., 180) are grouped, with each group containing one pitch angle and one azimuth angle, resulting in a group sequence (including 180×180 groups). Each group in the group sequence is traversed, and the corresponding pitch angle and azimuth angle are used as the direction of the applied magnetic field. The bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction are monitored.

[0031] Compared to this implementation, the first and second implementations described above require fewer applications of magnetic fields and fewer monitoring of the ODMR spectrum.

[0032] S3, the direction of the target resultant magnetic field is obtained based on the bimodal splitting value, the direction of the target applied magnetic field is obtained based on the fluorescence contrast, and the magnitude of the target resultant magnetic field is obtained based on the fluorescence contrast and the bimodal splitting value. The target resultant magnetic field is the combined magnetic field of the target applied magnetic field and the remanence of the superconducting magnet, and the direction of the target resultant magnetic field is parallel to the NV axis of the NV color center.

[0033] Based on the first and second embodiments described above, in some examples, obtaining the direction of the target resultant magnetic field based on the bimodal splitting value includes: determining a first azimuth angle that maximizes the bimodal splitting value; and using the direction determined by the first pitch angle and the first azimuth angle as the direction of the target resultant magnetic field. Obtaining the direction of the target applied magnetic field based on fluorescence contrast, and obtaining the magnitude of the target resultant magnetic field based on fluorescence contrast and the bimodal splitting value, includes: determining a second azimuth angle that maximizes the fluorescence contrast; using the direction determined by the second pitch angle and the second azimuth angle as the direction of the target applied magnetic field, and obtaining the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

[0034] Based on the first and second embodiments described above, in some other examples, the direction of the target resultant magnetic field is obtained based on the bimodal splitting value, the direction of the target applied magnetic field is obtained based on the fluorescence contrast, and the magnitude of the target resultant magnetic field is obtained based on the fluorescence contrast and the bimodal splitting value. This includes: performing curve fitting on the bimodal splitting value of the ODMR spectrum at each elevation angle, the bimodal splitting value of the ODMR spectrum at each azimuth angle, the fluorescence contrast of the ODMR spectrum at each elevation angle, and the fluorescence contrast of the ODMR spectrum at each azimuth angle; using the direction determined by the third elevation angle corresponding to the maximum bimodal splitting value in the fitted bimodal splitting value-elevation angle curve and the third azimuth angle corresponding to the maximum bimodal splitting value in the bimodal splitting value-azimuth angle curve as the direction of the target resultant magnetic field; using the direction determined by the fourth elevation angle corresponding to the maximum fluorescence contrast in the fitted fluorescence contrast-elevation angle curve and the fourth azimuth angle corresponding to the maximum fluorescence contrast in the fluorescence contrast-azimuth angle curve as the direction of the target applied magnetic field; and obtaining the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the fourth elevation angle and the fourth azimuth angle.

[0035] Based on the third embodiment described above, in some examples, obtaining the direction of the target resultant magnetic field based on the bimodal splitting value includes: determining the group that maximizes the bimodal splitting value; using the direction determined by the pitch and azimuth angles in that group as the direction of the target resultant magnetic field, and obtaining the magnitude of the target resultant magnetic field based on the maximum bimodal splitting value. Obtaining the direction of the target applied magnetic field based on fluorescence contrast, and obtaining the magnitude of the target resultant magnetic field based on fluorescence contrast and the bimodal splitting value, includes: determining the group that maximizes the fluorescence contrast; using the direction determined by the pitch and azimuth angles in that group as the direction of the target applied magnetic field, and obtaining the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the pitch and azimuth angles in that group.

[0036] Based on the third implementation described above, in some other examples, the direction of the target resultant magnetic field is obtained based on the bimodal splitting value, the direction of the target applied magnetic field is obtained based on the fluorescence contrast, and the magnitude of the target resultant magnetic field is obtained based on the fluorescence contrast and the bimodal splitting value. This includes: performing curve fitting on the bimodal splitting value of the ODMR spectrum under each group of determined directions and the fluorescence contrast of the ODMR spectrum under each group of determined directions; taking the first direction corresponding to the maximum bimodal splitting value in the fitted bimodal splitting value-magnetic field direction curve as the direction of the target resultant magnetic field, taking the second direction corresponding to the maximum fluorescence contrast in the fitted fluorescence contrast-magnetic field direction curve as the direction of the target applied magnetic field, and obtaining the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the second direction.

[0037] For example, step S2 above, which involves changing the direction of the applied magnetic field within a preset directional range and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction, can be performed once or multiple times. When performed multiple times, for the example of directly taking points, the average of multiple times can be taken as the final result; for the example of fitting a curve, the points obtained multiple times can be combined for curve fitting.

[0038] S4. Based on the magnitude and direction of the target's resultant magnetic field and the magnitude and direction of the target's applied magnetic field, the magnitude and direction of the superconducting magnet's remanence are obtained.

[0039] Specifically, based on the magnitude and direction of the target's resultant magnetic field and the magnitude and direction of the target's applied magnetic field, the magnitude and direction of the superconducting magnet's remanence can be obtained by vector subtraction using the triangle rule or parallelogram rule.

[0040] It should be noted that when under a magnetic field, the ODMR spectrum of the NV color center will have two key characteristics (i.e., the bimodal splitting value and the fluorescence contrast, such as...). Figure 2The values ​​of the two features (as shown in the figure) change, and thus, information about the magnetic field at the NV center 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 features may separate (i.e., their extreme values ​​correspond to external magnetic fields in different directions). The maximum value of the bimodal splitting value occurs when the applied magnetic field is parallel to the NV axis, while the maximum value of the fluorescence contrast occurs when the combined magnetic field of the applied magnetic field and the remanent magnetic field is parallel to the NV axis. Based on this, the superconducting magnet remanence measurement method of this embodiment of the invention, under the premise that the superconducting magnet has completed sufficient "training" (i.e., its remanence remains constant), actively applies a small magnetic field of known magnitude and systematically adjusts its direction, observes the changes in the extreme values ​​of the bimodal splitting value and fluorescence contrast of the ODMR spectrum of the NV center, and thus reversely calculates the accurate remanence vector information, thereby ensuring the accuracy and reliability of subsequent NV measurement data.

[0041] The following is combined Figure 3 Taking the second implementation method described above and the example of curve fitting as an example, the method for measuring the remanence of a superconducting magnet according to the present invention is explained.

[0042] like Figure 3 As shown, the method for measuring the remanence of a superconducting magnet can be divided into the following two stages: Phase 1: High-precision calibration of the NV axis direction 1) Apply a magnetic field of a preset size; The NV color center probe is placed at the sample point, and a preset size (e.g., ) is applied by a superconducting magnet. ) magnetic field The initial direction is arbitrary.

[0043] 2) Optimize the loop: Iterate through the directions to maximize the bimodal splitting value of the ODMR spectrum and obtain the precise NV axis direction (i.e., the direction of the target resultant magnetic field). Specifically, this may include the following steps: S2.1: Maintain The magnitude remains unchanged, and the pitch angle of the applied magnetic field direction is adjusted iteratively. 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 remains unchanged, and the process is iterated and adjusted. 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 ( , This is the true NV axis direction, denoted as ( , ).

[0044] 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.

[0045] 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. Figure 4 The left side shows Δf and The relationship (only a portion of the intervals are shown for clarity) is represented by the formula. Fit, where Electron gyromagnetic ratio, , For redundant fitting parameters, we can obtain =88.7°. Following the same steps, the fitting yielded... =55.5°. Note that at this point, the direction of the resultant magnetic field is not parallel to the NV axis; that is, the target resultant magnetic field has not been obtained, but only its expected direction has been determined. The magnitude of this target resultant magnetic field will be obtained in stage two, thus yielding the target resultant magnetic field.

[0046] Phase Two: High-Precision Determination of Remanent Magnetism Vector 3) Optimize the loop: Traverse the directions to maximize the fluorescence contrast of the ODMR spectrum and obtain the precise direction of the applied magnetic field to the target; specifically, this may include the following steps: S3.1: Maintain The magnitude remains unchanged, and starting from the current direction of the applied magnetic field, 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 remains unchanged, and the process is iterated and adjusted. The method of finding the maximum fluorescence contrast is determined by extreme value fitting. .

[0047] S3.3: Steps S3.1 to S3.2 can be repeated one or more times. direction ( , ) is denoted as ( , In this direction, the target's net magnetic field is parallel to the NV axis.

[0048] For example, from ( , Starting in the direction of ) and scanning in 2° increments. and The optimization target is fluorescence contrast ratio C.

[0049] By recording and fitting the data, we can find the direction that maximizes C. , And record it. Figure 4 The right side shows C and The relationship (only a portion of the intervals are shown for clarity) is represented by the formula. Fit, where , For redundant fitting parameters, we can obtain =97.8°. Following the same steps, the fitting yielded... =56°. At this point, the resultant magnetic field is along the NV axis, which is the target resultant magnetic field, and its direction has been known in stage one; the applied magnetic field at this point is the target applied magnetic field, and its direction is ( , ).

[0050] 4) Read the bimodal splitting value of the ODMR spectrum to obtain the magnitude of the target resultant magnetic field; Specifically, it reads in the direction ( , The bimodal splitting value of the ODMR spectrum is used to calculate the magnitude of the target resultant magnetic field B. total Specifically, you can refer to the formula. The calculated value is approximately Btotal ≈ 88.8G.

[0051] 5) Vector operations are used to obtain remanence.

[0052] like Figure 5 As shown, the vector solution is: B0 = B - B1. Where the size of B is B0. total The direction is ( , The magnitude of B1 is known, and its direction is ( ). , From this, the magnitude and direction of the remanence B0 can be obtained. , ).

[0053] For example, given B = (88.8G, direction (88.7°, 55.5°)) and B1 = (80G, direction (97.8°, 56°)), solving for B0 = B - B1 yields a magnitude of 12.3 G and a direction of ( ). , = (40.1°, 62.6°).

[0054] In some examples, when obtaining remanence B After 0, the vector information of B0 can be stored. Subsequently, when a target magnetic field needs to be applied by the superconducting magnet... B target At that time, it can automatically calculate and apply B applied = B target - B 0, achieving precise compensation to obtain the actual magnetic field to be applied. B applied .

[0055] Figure 6 This is a schematic diagram of the NV color center measurement system according to an embodiment of the present invention.

[0056] like Figure 6 As shown, the NV color center measurement system 600 includes: 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 includes an NV color center probe that provides NV color centers.

[0057] The control module 5 is connected to the superconducting magnet 1, the excitation module 3, and the detection module 4, and is specially programmed to form a closed-loop automatic control system. This system is used to: control the superconducting magnet 1 to apply a magnetic field of a preset magnitude to the NV center, control the excitation module 4 to provide excitation energy to the NV center, and acquire the ODMR spectrum through the detection module 3; change the direction of the applied magnetic field within a preset directional range, and monitor the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; obtain the direction of the target combined magnetic field based on the bimodal splitting value, obtain the direction of the target applied magnetic field based on the fluorescence contrast, and obtain the magnitude of the target combined magnetic field based on the fluorescence contrast and the bimodal splitting value. The target combined magnetic field is the combined magnetic field of the target applied magnetic field and the remanence of the superconducting magnet, and its direction is parallel to the NV axis of the NV center; and obtain the magnitude and direction of the superconducting magnet's remanence based on the magnitude and direction of the target combined magnetic field and the magnitude and direction of the target applied magnetic field.

[0058] For example, the excitation module 3 includes 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 resonant transition of the NV color center.

[0059] Optionally, the excitation module 3 and the detection module 4 can be integrated.

[0060] In some embodiments, the preset direction range includes a preset pitch angle range and a preset azimuth angle range. When the control module 5 changes the direction of the applied magnetic field within the preset direction range and monitors the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction, it is specifically used for: selecting one azimuth angle from the preset azimuth angle range and keeping it constant; traversing the pitch angles within the preset pitch angle range as the direction of the applied magnetic field; and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction; determining a first pitch angle that maximizes the bimodal splitting value and a second pitch angle that maximizes the fluorescence contrast; keeping the first pitch angle constant; traversing the azimuth angles within the preset azimuth angle range as the direction of the applied magnetic field; and monitoring the bimodal splitting value of the ODMR spectrum in each direction; keeping the second pitch angle constant; traversing the azimuth angles within 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.

[0061] For example, when the control module 5 obtains the magnitude and direction of the target resultant magnetic field based on the bimodal splitting value, it is specifically used to: determine the first azimuth angle that maximizes the bimodal splitting value; and take the direction determined by the first pitch angle and the first azimuth angle as the direction of the target resultant magnetic field.

[0062] For example, when the control module 5 obtains the direction of the magnetic field applied to the target based on the fluorescence contrast and the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value, it is specifically used to: determine the second azimuth angle that maximizes the fluorescence contrast; take the direction determined by the second pitch angle and the second azimuth angle as the direction of the magnetic field applied to the target, and obtain the magnitude of the target resultant magnetic field based on the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

[0063] In some embodiments, the control module 5 is further configured to: store the magnitude and direction of the remanence of the superconducting magnet; and / or compensate for the target magnetic field in applications where a target magnetic field needs to be applied by the superconducting magnet.

[0064] It should be noted that for other specific embodiments of the NV color center measurement system 600 of this invention, please refer to the specific embodiments of the superconducting magnet remanence measurement method in the above embodiments.

[0065] Figure 7 This is a structural block diagram of an electronic device according to an embodiment of the present invention.

[0066] like Figure 7 As shown, the electronic device 700 includes the NV color center measurement system 600 of the above embodiment.

[0067] Specifically, the NV color center measurement system 600 with remanent magnetization self-calibration function, through deep integration of hardware and specific control logic, constitutes a dedicated electronic device 700 as a measurement tool.

[0068] In summary, the method for measuring the remanence of superconducting magnets, the NV color center measurement system, and the electronic equipment of the present invention have the following beneficial effects: 1) Breakthrough in technical bottlenecks: Successfully solved two major problems in traditional NV magnetic measurement: "unknown direction of vertical component" and "inaccurate measurement of vertical component magnitude"; 2) Order-of-magnitude leap in accuracy: By replacing "absolute value measurement" with "extreme value search" and using multiple data points for fitting, super-resolution positioning of angles is achieved, with accuracy far exceeding that of traditional methods; 3) Highly operable and reliable: The streamlined steps are easy to automate, the results are stable and reliable, and it is easy to automate under computer control, achieving "one-click calibration".

[0069] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0070] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0071] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] In the description of this invention, 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," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0073] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0074] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0075] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0076] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for measuring the remanence of a superconducting magnet, characterized in that, Includes the following steps: A magnetic field of a predetermined magnitude is applied to the NV color center by a superconducting magnet, and excitation energy is provided to the NV color center by an excitation module; The direction of the applied magnetic field was changed within a preset range, and the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction were monitored. The direction of the target combined magnetic field is obtained based on the bimodal splitting value, the direction of the target applied magnetic field is obtained based on the fluorescence contrast, and the magnitude of the target combined magnetic field is obtained based on the fluorescence contrast and the bimodal splitting value. The target combined magnetic field is the combined magnetic field of the target applied magnetic field and the remanent magnet of the superconducting magnet, and the direction of the target combined magnetic field is parallel to the NV axis of the NV color center. The magnitude and direction of the superconducting magnet's remanence are obtained based on the magnitude and direction of the target's combined magnetic field and the magnitude and direction of the magnetic field applied to the target.

2. The method for measuring the remanence of a superconducting magnet according to claim 1, characterized in that, The preset direction range includes a preset pitch angle range and a preset azimuth angle range; The step of changing the direction of the applied magnetic field within a preset directional range and monitoring the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction includes: Select one azimuth angle from the preset azimuth angle range and keep it unchanged, traverse the pitch angles from the preset pitch angle range, use them as the direction of the applied magnetic field, and monitor the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction. Determine the first pitch angle that maximizes the bimodal splitting value and the second pitch angle that maximizes the fluorescence contrast; Keeping the first pitch angle constant, the azimuth angles within the preset azimuth angle range are traversed as the direction of the applied magnetic field, and the bimodal splitting value of the ODMR spectrum in each direction is monitored. Keeping the second pitch angle constant, the azimuth angles within the preset azimuth angle range are traversed as the direction of the applied magnetic field, and the fluorescence contrast of the ODMR spectrum in each direction is monitored.

3. The method for measuring the remanence of a superconducting magnet according to claim 2, characterized in that, The step of obtaining the direction of the target resultant magnetic field based on the bimodal splitting value, obtaining the direction of the target applied magnetic field based on the fluorescence contrast, and obtaining the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value includes: Determine the first azimuth angle that maximizes the bimodal splitting value; The direction determined by the first pitch angle and the first azimuth angle shall be taken as the direction of the target's resultant magnetic field. Determine the second azimuth angle that maximizes the fluorescence contrast; The direction determined by the second pitch angle and the second azimuth angle is taken as the direction in which the magnetic field is applied to the target, and the magnitude of the resultant magnetic field of the target is obtained according to the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

4. The method for measuring the remanence of a superconducting magnet according to claim 2, characterized in that, The step of obtaining the direction of the target resultant magnetic field based on the bimodal splitting value, obtaining the direction of the target applied magnetic field based on the fluorescence contrast, and obtaining the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value includes: Curve fitting was performed on the bimodal splitting values ​​of the ODMR spectra at each pitch angle, the bimodal splitting values ​​of the ODMR spectra at each azimuth angle, the fluorescence contrast of the ODMR spectra at each pitch angle, and the fluorescence contrast of the ODMR spectra at each azimuth angle. The direction determined by the third pitch angle corresponding to the maximum bimodal splitting value in the fitted bimodal splitting value-pitch angle curve and the third azimuth angle corresponding to the maximum bimodal splitting value in the fitted bimodal splitting value-azimuth angle curve is taken as the direction of the target resultant magnetic field. The direction determined by the fourth pitch angle corresponding to the maximum fluorescence contrast in the fitted fluorescence contrast-pitch angle curve and the fourth azimuth angle corresponding to the maximum fluorescence contrast in the fitted fluorescence contrast-azimuth angle curve is taken as the direction of the applied magnetic field to the target. The magnitude of the target resultant magnetic field is obtained based on the bimodal splitting value corresponding to the fourth pitch angle and the fourth azimuth angle.

5. The method for measuring the remanence of a superconducting magnet according to any one of claims 1-4, characterized in that, The step of changing the direction of the applied magnetic field within a preset directional range and monitoring the bipeak splitting value and fluorescence contrast of the ODMR spectrum in each direction is performed once or multiple times.

6. An NV color center measurement system, characterized in that, The system includes: 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 includes NV color centers; The control module is used for: The superconducting magnet is controlled to apply a magnetic field of a preset magnitude to the NV color center, and the excitation module is controlled to provide excitation energy to the NV color center, and the ODMR spectrum is obtained through the detection module; The direction of the applied magnetic field was changed within a preset range, and the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction were monitored. The direction of the target combined magnetic field is obtained based on the bimodal splitting value, the direction of the target applied magnetic field is obtained based on the fluorescence contrast, and the magnitude of the target combined magnetic field is obtained based on the fluorescence contrast and the bimodal splitting value. The target combined magnetic field is the combined magnetic field of the target applied magnetic field and the remanent magnet of the superconducting magnet, and the direction of the target combined magnetic field is parallel to the NV axis of the NV color center. The magnitude and direction of the superconducting magnet's remanence are obtained based on the magnitude and direction of the target's combined magnetic field and the magnitude and direction of the magnetic field applied to the target.

7. The NV color center measurement system according to claim 6, characterized in that, The preset direction range includes a preset pitch angle range and a preset azimuth angle range; when the control module changes the direction of the applied magnetic field within the preset direction range and monitors the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction, it is specifically used for: Select one azimuth angle from the preset azimuth angle range and keep it unchanged, traverse the pitch angles from the preset pitch angle range, use them as the direction of the applied magnetic field, and monitor the bimodal splitting value and fluorescence contrast of the ODMR spectrum in each direction. Determine the first pitch angle that maximizes the bimodal splitting value and the second pitch angle that maximizes the fluorescence contrast; Keeping the first pitch angle constant, the azimuth angles within the preset azimuth angle range are traversed as the direction of the applied magnetic field, and the bimodal splitting value of the ODMR spectrum in each direction is monitored. Keeping the second pitch angle constant, the azimuth angles within the preset azimuth angle range are traversed as the direction of the applied magnetic field, and the fluorescence contrast of the ODMR spectrum in each direction is monitored.

8. The NV color center measurement system according to claim 7, characterized in that, When the control module obtains the direction of the target resultant magnetic field based on the bimodal splitting value, obtains the direction of the target applied magnetic field based on the fluorescence contrast, and obtains the magnitude of the target resultant magnetic field based on the fluorescence contrast and the bimodal splitting value, it is specifically used for: Determine the first azimuth angle that maximizes the bimodal splitting value; The direction determined by the first pitch angle and the first azimuth angle shall be taken as the direction of the target's resultant magnetic field. Determine the second azimuth angle that maximizes the fluorescence contrast; The direction determined by the second pitch angle and the second azimuth angle is taken as the direction in which the magnetic field is applied to the target, and the magnitude of the resultant magnetic field of the target is obtained according to the bimodal splitting value corresponding to the second pitch angle and the second azimuth angle.

9. The NV color center measurement system according to any one of claims 6-8, characterized in that, The control module is also used for: Store the magnitude and orientation of the remanence of the superconducting magnet; and / or In applications where a target magnetic field needs to be applied via the superconducting magnet, the target magnetic field is compensated.

10. An electronic device, characterized in that, include: The NV color center measurement system as described in any one of claims 6-9.

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