Bias magnetic field output angle acquisition method, automatic control method and device

Abstract

The invention relates to the field of quantum precision measurement, and discloses a bias magnetic field output angle acquisition method, an automatic control method and an automatic control device, by adopting the bias magnetic field output angle acquisition method, the direction of a magnetic field generated by a three-dimensional Helmholtz coil can be efficiently and regularly parallel to a certain NV axis in a diamond, and the precision of the diamond is improved. Under the magnetic field setting condition, a four-peak ODMR curve can be obtained.

Description

Methods and devices for obtaining the output angle of the bias magnetic field, and automatic control methods. Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, specifically to a method for obtaining the output angle of a bias magnetic field, a diamond NV color center quantum device based on ODMR technology, an automatic control method for computer implementation, and a storage medium. Background Technology

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

[0003] When plotting ODMR curves, different numbers of even peaks are formed when the external magnetic field is at different spatial angles to the four NV axes of the diamond containing the ensemble NV color centers (e.g., an ODMR curve with two peaks is formed when the magnetic field direction is at equal angles to the four NV axes; an ODMR curve with eight peaks is formed when the magnetic field direction is at unequal angles to the four NV axes; and an ODMR curve with four peaks is formed when the magnetic field direction is parallel to any NV axis). Among these, the four-peak ODMR curve has a higher signal-to-noise ratio during measurement, which is the state that the diamond NV color center quantum detection device wants to obtain during detection. In existing devices, a three-dimensional Helmholtz coil is often used as a magnetic field generating device. The magnetic field direction is adjusted by controlling the magnitude of the current in the coil in the XYZ three-axis directions. However, the adjustment process is entirely determined by the engineer based on the real-time ODMR curve (by manually adjusting the three-axis current and manually calibrating by observing the ODMR curve). Manual adjustment relies on the engineer's experience, is time-consuming (usually more than 30 minutes), and has poor repeatability. Based on this, the present invention is proposed. Summary of the Invention

[0004] This invention proposes a method, an automatic control method, and a device for obtaining the output angle of a bias magnetic field, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for obtaining the output angle of a bias magnetic field, applicable to a diamond NV center quantum device based on ODMR technology, wherein the diamond NV center quantum device has a three-dimensional Helmholtz coil and a diamond containing an ensemble NV center; the method for obtaining the output angle of the bias magnetic field includes: applying an initial bias magnetic field at the location of the diamond based on the three-dimensional Helmholtz coil, wherein the angle between the initial bias magnetic field and the Z-axis direction is a set angle a1; wherein, if the angle between the Z-axis direction and the four NV axes inside the diamond satisfies the theoretical equality, then the set angle a1 is 54.735°±2. °; If the Z-axis direction is theoretically parallel to any NV axis inside the diamond, then the angle a1 is set to 0°±2°; Keep the total strength of the initial bias magnetic field and the angle between it and the Z-axis direction unchanged, control the initial bias magnetic field to rotate around the Z-axis and scan to obtain the photoluminescence intensity. When the photoluminescence intensity reaches any peak value, obtain the horizontal angle b corresponding to the initial bias magnetic field; Keep the total strength of the initial bias magnetic field unchanged and fixed at the horizontal angle b, adjust the angle between the initial bias magnetic field and the Z-axis direction and scan to obtain the photoluminescence intensity. When the photoluminescence intensity is at its peak value, obtain the angle a2 between the initial bias magnetic field and the Z-axis direction.

[0006] In a preferred design of the method for obtaining the output angle of the bias magnetic field as described above, the horizontal angle b corresponding to the initial bias magnetic field is obtained when the photoluminescence intensity first reaches its peak.

[0007] In a preferred design of the method for obtaining the output angle of the bias magnetic field as described above, the angle between the initial bias magnetic field and the Z-axis direction is adjusted within the angle range of a1±20°.

[0008] In a preferred design of the bias magnetic field output angle acquisition method described above, current is sequentially applied to the X-axis coil, Y-axis coil, and Z-axis coil to obtain the current-magnetic field curves of the three coils, and the curve formula is obtained by fitting.

[0009] Another aspect of this application also introduces a diamond NV color center quantum device based on ODMR technology, which includes a three-dimensional Helmholtz coil and a diamond containing an ensemble NV color center, and includes a bias magnetic field output module. The bias magnetic field output module is configured to perform the bias magnetic field output angle acquisition method as described in any of the preceding claims, and control the three-dimensional Helmholtz coil to output a working bias magnetic field of the required magnitude at the location of the diamond at a horizontal angle b and an included angle a2.

[0010] In a preferred design of the diamond NV center quantum device described above, a curve display module is also included, which is used at least to output observable ODMR curves and fluorescence intensity versus angle curves.

[0011] In a preferred design of the diamond NV center quantum device described above, a data acquisition module is further included, which is at least used to track and acquire fluorescence characterization data of the NV axis that coincides with the direction of the working bias magnetic field.

[0012] Another aspect of this application also describes a computer-implemented automatic control method, which, when the initial parameter setting is completed and executed on the data processing hardware, causes the data processing hardware to perform the operation of the bias magnetic field output angle acquisition method as described in any of the preceding claims.

[0013] In a preferred design of the automatic control method described above, after obtaining the output angle of the bias magnetic field, the three-dimensional Helmholtz coil is controlled to output the required working bias magnetic field at the location of the diamond according to the horizontal angle b and the included angle a2.

[0014] Another aspect of this application also describes a storage medium storing a computer program, which, when executed by data processing hardware, can perform the operation of the automatic control method described above after the initial parameter setting is completed.

[0015] Compared with the prior art, the beneficial effects of the present invention are: by using the bias magnetic field output angle acquisition method of the present invention, the magnetic field direction generated by the three-dimensional Helmholtz coil can be made parallel to a certain NV axis in the diamond in a efficient and regular manner. Under this magnetic field setting, a four-peak ODMR curve can be obtained. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 is a schematic diagram of the four axial distributions of NV color centers in diamond; Figure 2 is a schematic diagram of

[100] diamond in the XYZ three-axis coordinate system; Figure 3 is a flowchart of the method for obtaining the output angle of the real bias magnetic field; Figure 4 is a schematic diagram of the linear fitting curve of the current-magnetic field of the X-axis coil; Figure 5 is a schematic diagram of the linear fitting curve of the current-magnetic field of the Y-axis coil; Figure 6 is a schematic diagram of the linear fitting curve of the current-magnetic field of the Z-axis coil; Figure 7 is a schematic diagram of the theoretical curve of fluorescence voltage versus horizontal angle; Figure 8 is a schematic diagram of the ODMR curve with the bias magnetic field parallel to an NV axis; Figure 9 is a measured curve of fluorescence voltage versus horizontal angle (angle range: 0°-90°); Figure 10 is a measured curve of fluorescence voltage versus vertical angle (angle range: 54°±20°); Figure 11 is a schematic diagram of the diamond NV color center quantum device in Example 2; Figure 12 is a schematic diagram of the hardware structure of the storage medium in Example 4. Detailed Implementation

[0018] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, one or more embodiments are now described with reference to the accompanying drawings, wherein similar reference numerals are used throughout the text to refer to similar components. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a more thorough understanding of one or more embodiments. However, it will be apparent that one or more embodiments may be practiced in various circumstances without these specific details, and the various embodiments may be combined with and referenced to each other without contradiction.

[0020] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0021] A diamond NV center (nitrogen-vacancy center) is an atomic-level defect in the diamond lattice, formed by a nitrogen atom (N) replacing a carbon atom and bonding with an adjacent vacancy (V). It is one of the most promising solid-state spin center systems due to its exceptional quantum properties at room temperature, making it a core platform for quantum sensing, quantum computing, and quantum communication.

[0022] For diamond containing ensemble NV color centers, due to the limitations of the crystal lattice morphology, only four NV axis distributions can be formed inside, as shown in Figure 1. Theoretically, the four NV axes are at equal angles (but in reality, there will be slight angle deviations due to some reasons), with an angle of 109.47°. For ease of understanding, the four NV axes can also be equivalently drawn within a diamond crystal lattice, and a spatial coordinate system (XYZ three-axis coordinate system) can be constructed with a vacancy (V) as the origin. The positional relationship of the four NV axes (NV1~NV4) in the coordinate system is shown in Figure 2.

[0023] Regarding diamonds containing ensemble NV centers, they can be grown along different crystal orientations. For this scheme, diamond cubes (which can be cubes or cuboids) grown along the

[100] crystal orientation and its equivalent crystal orientation or the

[111] crystal orientation and its equivalent crystal orientation are generally selected. For ease of description, they will be referred to as

[100] diamonds and

[111] diamonds in the following text. Since the four NV axes in the diamond correspond to the diamond lattice, for the cube-shaped

[100] diamond, when it is placed flat in the magnetic coordinate system of a three-dimensional Helmholtz coil, theoretically its Z-axis direction is located in the middle of NV1 and NV4, with an angle of half 109.47° with NV1, i.e., 54.735°, as shown in Figure 2. For the

[111] diamond, theoretically, the Z-axis direction is parallel to the NV1 axis. Example 1

[0024] This example introduces a method for obtaining the output angle of a bias magnetic field, applicable to diamond NV center quantum devices based on ODMR (Optically Detected Magnetic Resonance) technology. The diamond NV center quantum device has a three-dimensional Helmholtz coil and a diamond containing ensemble NV centers. The purpose is to adjust the direction of the bias magnetic field to be parallel to one NV axis. This results in a four-peak ODMR curve with a high signal-to-noise ratio, as shown in Figure 3. The method for obtaining the output angle of the bias magnetic field includes steps S1 to S3, as follows: S1: An initial bias magnetic field is applied to the diamond location based on the three-dimensional Helmholtz coil. The angle between this initial bias magnetic field and the Z-axis is a set angle a1. If the angle between the Z-axis and the four NV axes inside the diamond is theoretically equal, then the set angle a1 is 54.735°±2°; if the Z-axis is theoretically parallel to any NV axis inside the diamond, then the set angle a1 is 0°±2°.

[0025] Regarding the three-dimensional Helmholtz coil, it includes an X-axis coil, a Y-axis coil, and a Z-axis coil. When energized, it generates a uniform magnetic field with a consistent direction at its internal center. In existing diamond NV color center quantum devices containing three-dimensional Helmholtz coils, the diamond is installed at the internal center of the three-dimensional Helmholtz coil. The magnitude and direction of the magnetic field acting on the diamond are changed by altering the current in the three directions. Before use, the three-dimensional Helmholtz coil requires coordinate system calibration and magnetic field-current relationship calibration.

[0026] Regarding coordinate system calibration, the steps are as follows: A constant current source is applied to the X-axis coil, and a three-dimensional gaussmeter probe (or other sensor capable of detecting the direction of the magnetic field) is inserted into the uniform region of the coil to measure the magnetic field generated along the X-axis. The direction of the positive magnetic field is calibrated as the +X direction. Similarly, a constant current is applied to the Y-axis and Z-axis coils, and a three-dimensional gaussmeter probe is inserted into the uniform region of the coils to measure the magnetic fields generated by the Y-axis and Z-axis coils. The directions of the positive magnetic fields are calibrated as the +Y and +Z directions, respectively. Generally, coordinate system calibration of the three-dimensional Helmholtz coil is performed before using the method described in this scheme, or a three-dimensional Helmholtz coil with a known coordinate system can be used directly. However, if the coordinate system of an unknown three-dimensional Helmholtz coil is used, calibration must be performed first.

[0027] The calibration of the magnetic field-current relationship actually refers to sequentially and individually applying current to the X-axis coil, Y-axis coil, and Z-axis coil to obtain the current-magnetic field curves of the three coils, and then fitting the curve formula. The example steps involve applying current to the X-axis coil using a constant current source, gradually increasing the current in 0.2A increments until the rated current is reached, while simultaneously recording the magnetic field value corresponding to each current (this can be done using an external magnetometer such as a 3D gaussmeter probe, or by calibrating the magnetic field within the device itself). The current-magnetic field curve is plotted in 0.2A increments until the rated current is reached (Bx = Ix * Kx + bx, where Bx is the magnetic field value generated by the X-axis coil, Ix is the current value applied to the X-axis coil, Kx is the curve slope, and bx is the curve base). By fitting the curve, the curve slope Kx and the curve base bx can be obtained; thus, the curve formula can be derived. Similarly, the current-magnetic field strain curve formulas for the other two coils can be obtained, as shown in Figures 4, 5, and 6, corresponding to the current-magnetic field curves and curve formulas for the X-axis coil, Y-axis coil, and Z-axis coil, respectively.

[0028] Referring to Figure 2, the significance of this step is explained. In this scheme, the

[100] diamond is placed in the positive magnetic field coordinate system of the three-dimensional Helmholtz coil. An initial bias magnetic field is applied through the three-dimensional Helmholtz coil, and the angle between the initial bias magnetic field and the Z-axis is a set angle a1. The size of the set angle a1 needs to be determined based on the selected diamond, but the goal is that the size of the set angle should be equal to or close to the theoretical angle between the Z-axis and the NV1 axis (i.e., 54.735°). In this way, when the initial bias magnetic field is rotated around the Z-axis in step S2, it can be ensured that the found horizontal angle b (i.e., the angle between the component magnetic field of the initial bias magnetic field in the XY plane and the X-axis) is equal to or approximately equal to the angle between the projection of the NV1 axis in the XY plane and the X-axis. Compared with the

[100] diamond, if the

[111] diamond is used, the set angle should also be equal to or close to the theoretical angle between the Z-axis and the NV1 axis (i.e., 0°).

[0029] S2. Keep the total strength of the initial bias magnetic field and the angle between it and the Z-axis unchanged. Control the initial bias magnetic field to rotate around the Z-axis and scan to obtain the photoluminescence intensity. When the photoluminescence intensity reaches any peak value, obtain the horizontal angle b corresponding to the initial bias magnetic field.

[0030] After setting in step S1, the angle between the initial bias magnetic field and the Z-axis is equal to or nearly equal to the angle between the NV1 axis and the Z-axis. However, the initial bias magnetic field is not necessarily on the same vertical plane as the NV1 axis; there is a lateral angle difference between them. Therefore, the purpose of step S2 is to determine whether the rotated initial bias magnetic field is on the same vertical plane as the NV1 axis by rotating the initial bias magnetic field around the Z-axis and observing the fluorescence change. After setting in step S1, the initial bias magnetic field rotated around the Z-axis will sequentially become parallel or nearly parallel to the four NV axes. The fluorescence intensity is most obvious each time it becomes parallel or nearly parallel to the NV axis. This horizontal angle b is related to the fluorescence voltage ( The relationship between the change of photoluminescence intensity (converted into a fluorescence voltage signal by a photodetector module) should be as shown in Figure 7. The horizontal angle corresponding to the peak should be equal to the angle between the projection of the NV axis on the XY plane and the X-axis direction. The horizontal angle b at the first peak corresponds to the angle between the projection of the NV1 axis on the XY plane and the X-axis direction. The purpose of this step is to find this angle value through this process. For this purpose, it is necessary to control variables, that is, to keep the total strength of the initial bias magnetic field and the size of its angle with the Z-axis direction unchanged. This means that the magnitude of the magnetic field generated by the Z-axis coil remains unchanged. By coordinating the change of the magnetic field strength of the X-axis coil and the Y-axis coil, the resultant magnetic field strength generated by the two coils remains unchanged, and the magnetic field direction rotates around the Z-axis. This control method is easy to implement after knowing the relationship between the change of the magnetic field generated by each axis coil and itself.

[0031] S3. Keep the total strength of the initial bias magnetic field unchanged and fixed at the horizontal angle b. Adjust the angle between the initial bias magnetic field and the Z-axis and scan to obtain the photoluminescence intensity. When the photoluminescence intensity is at its peak, obtain the angle a2 between the initial bias magnetic field and the Z-axis.

[0032] Considering that whether using

[100] diamond or

[111] diamond, due to the internal stress of diamond, uneven cutting leading to installation tilt, etc., the theoretical angle between the Z-axis and the NV1 axis has a fluctuation range, the preset angle a1 in step S1 cannot guarantee that the bias magnetic field is parallel to the NV1 axis during operation. Therefore, step S3 needs to find the angle between the bias magnetic field and the Z-axis more accurately, and this angle is equal to the angle between the NV1 axis and the Z-axis. Since the horizontal angle b has been found in step S2, when the initial bias magnetic field satisfies the horizontal angle b and the total magnetic field strength remains unchanged, the initial bias magnetic field and the NV1 axis are in the same vertical plane. Therefore, in step S3, it is only necessary to adjust the angle between the initial bias magnetic field and the Z-axis. During the adjustment process, the fluorescence intensity is detected. When the photoluminescence intensity is at its peak (the photoluminescence intensity reaches its maximum value, indicating that the bias magnetic field direction is parallel to the NV1 axis at this time), the angle a2 between the initial bias magnetic field and the Z-axis is obtained.

[0033] So far, we have obtained the positioning angles of the NV1 axis in the XYZ three-axis coordinate system, namely the horizontal angle b (the angle between the projection of the NV1 axis on the XY plane and the X-axis direction) and the angle a2 (the angle between the NV1 axis and the Z-axis). It is easy to control the three-dimensional Helmholtz coil to output the required bias magnetic field at these two angles. The example scheme is as follows: Substitute (a2, b) into the formula. If the total magnetic field is 30Gs, then: Bz=30*cos(a2)=Iz*Kz+bz; Bx=30*sin(a2)*cos(b)=Ix*Kx+bx; By=30*sin(a2)*sin(b)=Iy*Ky+by.

[0034] In the formula, Bx, By, and Bz are the magnetic field values ​​generated by the X-axis coil, Y-axis coil, and Z-axis coil, respectively; Ix, Iy, and Iz are the current values ​​passed through the X-axis coil, Y-axis coil, and Z-axis coil, respectively; Kx, Ky, and Kz are the slopes of the curves relating the X-axis coil to the current, Y-axis coil to the current, and Z-axis coil to the current, respectively; and bx, by, and bz are the curve bases of the curves relating the X-axis coil to the current, Y-axis coil to the current, and Z-axis coil to the current, respectively.

[0035] The above method can quickly achieve parallelism between the bias magnetic field and the NV axis, thereby obtaining a four-peak ODMR curve (of course, obtaining a displayable ODMR is not the actual purpose), saving adjustment time and making subsequent operations more regular and repeatable.

[0036] In step S2, when the initial bias magnetic field is rotated around the Z-axis to obtain four peaks (as shown in Figure 7), it is feasible to take the horizontal angle b corresponding to any peak, and the effect is the same. Therefore, it is unnecessary to control the initial bias magnetic field to complete a 360° scan around the Z-axis, which would undoubtedly waste time and effort. Based on this, in some preferred solutions, it can be required that the horizontal angle b corresponding to the initial bias magnetic field is obtained when the photoluminescence intensity first reaches a peak. Furthermore, considering that the four NV axes of diamond are at equal angles (i.e., perpendicular to each other) from a top-view perspective, controlling the initial bias magnetic field to complete a 0°-90° rotation around the Z-axis will inevitably produce a fluorescence peak. Therefore, when controlling the X-axis and Y-axis coils, it is only necessary to execute within this rotation angle range, without the need for large-angle scanning, thereby shortening the horizontal angle b. The acquisition time is shown in Figure 9, which represents the initial bias magnetic field rotating around the Z-axis in the range of 0°-90°. The angle corresponding to the peak point (the position of the dashed line) in the figure is the horizontal angle b to be obtained. (The peak point on the left side of the dashed line in the figure is the jitter error at startup. There is a sharp peak point on the right side of the dashed line in the figure, which is actually the error caused by laser jitter. These two anomalies should be ignored when selecting the horizontal angle.)

[0037] In step S1, the standard and rationale for setting angle a1 have been explained. Here, we discuss the range in which the set angle size and the theoretical angle between the Z-axis direction and the NV1 axis are close to each other, so as to give the implementer a wider operating range. Since

[100] diamond and

[111] diamond are two commonly used sensing media in diamond NV color center sensing devices, this solution is for

[100] diamond (this type of diamond is placed flat in the magnetic field coordinate system of a three-dimensional Helmholtz coil, and the angle between the Z-axis direction and the four NV axes inside the diamond satisfies the theoretical equality) and [1 ... The diamond was placed flat in the magnetic field coordinate system of a three-dimensional Helmholtz coil (the Z-axis direction is theoretically parallel to any NV axis inside the diamond). For

[100] diamond, in addition to the theoretical angle of 54.735°, the set angle a1 was changed to 52.735° and 56.735°; for

[111] diamond, in addition to the theoretical angle of 0°, the set angle a1 was changed to -2° and +2°. After the above design, they can all obtain the four-peak ODMR curve shown in Figure 8. This shows that it is also possible to limit the set angle a1 to the range of ±2° of the theoretical angle.

[0038] In step S3, it is necessary to adjust the angle between the initial bias magnetic field and the Z-axis. While adjusting the entire angle will inevitably yield the desired angle a2, this process is time-consuming and labor-intensive. Considering that the set angle a1 is actually close to the desired angle a2, there is no need to perform a large-scale search. Therefore, in a preferred design, the angle between the initial bias magnetic field and the Z-axis is adjusted within the set angle a1 ± 20° range to find the angle a2 between the initial bias magnetic field and the Z-axis. Based on the limitation of the set angle a1 in step S1, adjusting within the set angle a1 ± 20° range is sufficient. When the experiment is set in this way, a four-peak ODMR curve can be output, and the operation is stable, as shown in Figure 10. This represents adjusting the angle between the initial bias magnetic field and the Z-axis within the angle range of 54° ± 20°. The angle corresponding to the peak value (where the dotted line is located) in the figure is the desired angle a2 (the peak value to the left of the dotted line in the figure is the jitter error during startup, and this abnormality should be ignored when selecting the angle).

[0039] Regarding the method of obtaining the corresponding angle value at the peak, in this example and its preferred embodiment, it can be obtained by manual selection; of course, it can also be obtained automatically through algorithm design. Example 2

[0040] This example introduces a diamond NV center quantum device based on ODMR technology, as shown in Figure 11. It includes a three-dimensional Helmholtz coil 1 and a diamond 2 containing an ensemble NV center. It also includes a bias magnetic field output module 3, which is configured to execute the bias magnetic field output angle acquisition method as described in the previous embodiment, and control the three-dimensional Helmholtz coil 1 to output a working bias magnetic field of the required magnitude at the location of the diamond 2 at a horizontal angle b and an included angle a2. In addition, the device also includes other components for implementing ODMR technology, including a laser module 4, a microwave module 5, a photoelectric detection module 6, a main control module 7, and a host 8.

[0041] The working principle of the diamond NV center quantum device based on ODMR technology specifically includes: the laser module 4 transmits excitation light (preferably a 532nm laser) to the diamond 2, the microwave module 5 radiates a microwave field to the diamond 2 (the frequency of the microwave field is sufficient to force the NV centers in the diamond 2 to undergo spin flipping; the microwave frequency used in different scenarios varies and depends on the actual situation), the diamond 2 generates photoluminescence that changes with the magnetic field strength under stimulation, the photodetector module 6 collects the photoluminescence and converts it into an electrical signal, which is then transmitted to the main control module 7. The main control module 7 processes the fluorescent electrical signal and interacts with the host 8. At the same time, the main control module 7 is also electrically connected to the laser module 4 and the microwave module 5 for corresponding control.

[0042] In this example, the bias magnetic field output module 3 mainly exists in the processor of the host 8 in the form of a program module. Its operation in this example is not completely autonomous. For example, before starting step S1, the value of the set angle a1, the angle range of the initial bias magnetic field around the Z-axis, and the angle adjustment range between the initial bias magnetic field and the Z-axis direction need to be manually filled in. After clicking the corresponding start button, the built-in program of the bias magnetic field output module 3 controls the subsequent actions. The parameters can be modified as needed before each operation. In other embodiments, the determined reliable parameters can also be written in advance in the program design of the bias magnetic field output module 3. However, it is important to clearly mark the diamond type that the system is adapted to (

[100] diamond OR

[111] diamond). After the diamond is determined, the other parameters are universal. Therefore, when operating the device, the bias magnetic field output module 3 can be started with one click until the desired bias magnetic field in a specific direction is obtained.

[0043] In this example, the laser module 4 can be a laser or an LED. The excitation light it outputs can enter the diamond 2 through an optical waveguide (such as an optical fiber) or as spatial light. Similarly, the photoluminescence generated by the diamond 2 can also be received by the photodetector in the photodetector module 6 through an optical waveguide or spatial light transmission. The photodetector can be a narrow field sensing device such as a photodiode, or a wide field light sensing device such as a CCD or CMOS (such as a diamond NV color center wide field measurement device used with an objective lens).

[0044] The specific functions and uses of the diamond NV center quantum device mentioned in this example are not limited. It can be used for magnetic field measurement, temperature measurement, pressure measurement, and can also be used as a teaching or research device for the study of NV center performance.

[0045] In a preferred embodiment, the diamond NV color center quantum device preferably includes a curve display module, which is used to output at least observable ODMR curves and fluorescence intensity versus angle curves. When the bias magnetic field output module 3 is used to adjust the bias magnetic field, an intuitively visible ODMR curve allows the operator to know whether the bias magnetic field output module 3 is operating normally. When the bias magnetic field output module 3 fails or is not used, the bias magnetic field can also be adjusted manually by observing the ODMR curve while adjusting the coil output. The fluorescence intensity versus angle curves mentioned here include the curve of the change between the horizontal angle b and the fluorescence voltage (corresponding to S2) and the curve of the change between the vertical angle a (representing the angle between the initial bias magnetic field and the Z-axis) and the fluorescence voltage (corresponding to S3). When the bias magnetic field output module 3 is not fully automated, in steps 2 and 3, it is necessary to manually obtain the horizontal angle b and the angle a2 based on the obtained fluorescence voltage versus angle relationship curves.

[0046] In a further design, the diamond NV center quantum device preferably includes a data acquisition module. This module is used at least to track and acquire fluorescence characterization data along the NV axis that coincides with the direction of the working bias magnetic field. Referring to Figure 8, the pair of relatively short peaks on the outer side correspond to the fluorescence characterization data along the NV axis that coincides with the direction of the working bias magnetic field. Because of its extremely high signal-to-noise ratio, it can obtain more accurate measurement results. Example 3

[0047] Another aspect of this application also introduces a computer-implemented automatic control method that, when the initial parameter setting is completed and executed on the data processing hardware, causes the data processing hardware to perform operations similar to any of the previous bias magnetic field output angle acquisition methods.

[0048] In the method for obtaining the output angle of the bias magnetic field described in this invention, some steps S1 to S3 can be implemented by computer, while others require manual assistance; the automatic control method of this embodiment includes at least the basic program framework for implementing steps S1 to S3.

[0049] For example, regarding step S1, the automatic control method at least includes, after inputting the control parameters for the initial bias magnetic field, being able to control the three-dimensional Helmholtz coil to output the required initial bias magnetic field via command. The step of inputting the control parameters for the initial bias magnetic field can be done manually before each use; after completing the manual parameter setting, a single-click start control can be used to output the initial bias magnetic field. Alternatively, in another example, the control parameters for the initial bias magnetic field can exist as a fixed pre-command in the program (e.g., set at the factory). When outputting the initial bias magnetic field, the required initial bias magnetic field can be directly output after startup, without the need for manual parameter input. Furthermore, in the automatic control method... When setting the control parameters of the initial bias magnetic field using the pre-command method, one or more pre-commands can be included, such as pre-commands corresponding to

[100] diamond or

[111] diamond respectively. Before working, it is also necessary to select the corresponding pre-command to control the output of the initial bias magnetic field according to the selected diamond type. Regarding the parameter setting of the angle a1, for example, if the angle between the Z-axis direction and the four NV axes inside the diamond satisfies the theoretical equality (i.e., the case of using

[100] diamond), then the angle a1 is set to 52°~56°; if the Z-axis direction and any NV axis inside the diamond satisfies the theoretical parallelism (i.e., the case of using

[111] diamond), then the angle a1 is set to 0°~4°.

[0050] For example, for step S2, the automatic control method includes at least the following: after inputting the control parameters of the initial bias magnetic field, the three-dimensional Helmholtz coil can be controlled by a command to control the initial bias magnetic field to complete the rotation around the Z-axis in the desired manner. The step of inputting the control parameters of the initial bias magnetic field can be manually filled in before each use. After completing the manual parameter setting, the output of the initial bias magnetic field can be controlled by a single key. Of course, in another example, the control parameters of the initial bias magnetic field can also exist as a fixed pre-command in the program (such as being set in the program before leaving the factory). During detection, a single key can be used to complete the rotation scanning process of the initial bias magnetic field around the Z-axis. Of course, the single key start action can be performed at the same time as the start of step S1, or it can be started in stages.

[0051] For step S2, after the initial bias magnetic field is rotated around the Z-axis according to the command, the horizontal angle b can be manually extracted based on the curve of the horizontal angle and the fluorescence voltage. Of course, for a more convenient and intelligent approach, the computer-implemented automatic control method further includes a method for automatically extracting the horizontal angle b, such as a curve fitting algorithm and a feature point selection algorithm.

[0052] Based on the same considerations as before, and considering that the four NV axes of diamond are at equal angles (i.e., perpendicular to each other) from a top-down view, controlling the initial bias magnetic field to rotate around the Z-axis from 0° to 90° will inevitably produce a fluorescence peak. Therefore, when controlling the X-axis and Y-axis coils, preferably, in this automatic control algorithm, the control parameters only need to satisfy the requirement of controlling the initial bias magnetic field to rotate around the Z-axis from 0° to 90°, without needing to perform too many angle rotations. This can save time in obtaining the horizontal angle b. Of course, this is a preferred solution and not a limitation on the rotation angle range.

[0053] For example, for step S3, the automatic control method includes at least the following: after inputting the control parameters of the initial bias magnetic field, the three-dimensional Helmholtz coil can be controlled by command to adjust the angle between the initial bias magnetic field and the Z-axis direction as required and scan to obtain the photoluminescence intensity. The step of inputting the control parameters of the initial bias magnetic field can be manually filled in before each use. After completing the manual parameter setting, the output of the initial bias magnetic field can be controlled by one-click start. Of course, in another example, the control parameters of the initial bias magnetic field can also exist as a fixed pre-command in the program (such as being set in the program before leaving the factory). During detection, the scanning process can be completed by one-click start. This one-click start operation can be executed at the same time as the start of step S1 or S2, or it can be started step by step.

[0054] For step S3, after controlling the three-dimensional Helmholtz coil to adjust the angle between the initial bias magnetic field and the Z-axis as required and scanning to obtain the photoluminescence intensity, the angle a2 can be manually extracted based on the curve of the vertical angle and the fluorescence voltage. Of course, considering a more convenient and intelligent approach, the computer-implemented automatic control method further includes a method for automatically extracting the angle a2, such as a curve fitting algorithm and a feature point selection algorithm.

[0055] In step S3, it is necessary to adjust the angle between the initial bias magnetic field and the Z-axis. While adjusting the entire angle will inevitably yield the desired angle a2, this process is time-consuming and labor-intensive. Considering that the set angle a1 is actually close to the desired angle a2, there is no need to perform a large-scale search. Therefore, in a preferred design, during the operation of the automatic control method, the angle between the initial bias magnetic field and the Z-axis is adjusted within the angle range of set angle a1 ± 20° to find the angle a2 between the initial bias magnetic field and the Z-axis. This design can be entered manually or written into the program of the automatic control method as a pre-command.

[0056] As described above, if the magnetic field-current relationship of the three coils of the three-dimensional Helmholtz coil is unknown before proceeding with this scheme, corresponding calibration is required. The calibration of the magnetic field-current relationship actually refers to sequentially and individually applying current to the X-axis coil, Y-axis coil, and Z-axis coil to obtain the current-magnetic field curves of the three coils, and then fitting the curve formula. Therefore, in the preferred scheme, the automatic control method also includes the following steps: after inputting the coil power supply control parameters, the function of obtaining the current-magnetic field curve and fitting the curve formula is triggered by the command. The specific technical details are relatively conventional and will not be elaborated here.

[0057] After obtaining the horizontal angle b and the included angle a2, the preliminary goal of this example has been achieved. The operator can then output a bias magnetic field parallel to an NV axis based on this angle information. In some solutions, this automatic control method can further, after obtaining the bias magnetic field output angle, automatically control the three-dimensional Helmholtz coil to output the required working bias magnetic field at the diamond location according to the horizontal angle b and the included angle a2. This can be done by manually filling in the bias magnetic field output angle or by automatically obtaining the angle information through a program and outputting it directly. Example 4

[0058] Corresponding to the computer-implemented automatic control method described above, as shown in Figure 12, one embodiment of this application also introduces a storage medium 200. The storage medium 200 can be a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by data processing hardware, it can perform the operation of the automatic control method described above after the initial parameter setting is completed. The computer program contains one or more computer-readable instructions 201. For example, when the computer-readable instructions 201 are executed by a processor, one or more steps in the automatic control method described above can be performed.

[0059] The various embodiments in the specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0060] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0061] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented directly by hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0062] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," 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, 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.

[0063] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for obtaining the output angle of a bias magnetic field, applicable to a diamond NV center quantum device based on ODMR technology, wherein the diamond NV center quantum device has a three-dimensional Helmholtz coil and a diamond containing an ensemble NV center, the method for obtaining the output angle of the bias magnetic field being characterized in that it includes: applying an initial bias magnetic field at the location of the diamond based on the three-dimensional Helmholtz coil, wherein the angle between the initial bias magnetic field and the Z-axis direction is a set angle α1; wherein, If the angle between the Z-axis and the four NV axes inside the diamond is theoretically equal, then angle a1 is set to 54.735°±2°; if the Z-axis is theoretically parallel to any NV axis inside the diamond, then angle a1 is set to 0°±2°; keeping the total strength of the initial bias magnetic field and its angle with the Z-axis constant, the initial bias magnetic field is rotated around the Z-axis and scanned to obtain the photoluminescence intensity. When the photoluminescence intensity reaches any peak value, the horizontal angle b corresponding to the initial bias magnetic field is obtained; keeping the total strength of the initial bias magnetic field constant and fixed at the horizontal angle b, the angle between the initial bias magnetic field and the Z-axis is adjusted and the photoluminescence intensity is scanned to obtain the photoluminescence intensity. When the photoluminescence intensity is at its peak value, the angle a2 between the initial bias magnetic field and the Z-axis is obtained.

2. The method for obtaining the output angle of the bias magnetic field according to claim 1, characterized in that, When the photoluminescence intensity first reaches its peak, the horizontal angle b corresponding to the initial bias magnetic field is obtained.

3. The method for obtaining the output angle of the bias magnetic field according to claim 1, characterized in that, Adjust the angle between the initial bias magnetic field and the Z-axis direction within the set angle range of a1±20°.

4. The method for obtaining the output angle of the bias magnetic field according to claim 1, characterized in that, By sequentially applying current to the X-axis coil, Y-axis coil, and Z-axis coil, the current-magnetic field curves of the three coils are obtained, and the curve formulas are obtained by fitting the curves.

5. A quantum device for diamond NV centers based on ODMR technology, comprising a three-dimensional Helmholtz coil and diamond containing ensemble NV centers, characterized in that, The device includes a bias magnetic field output module, which is configured to perform the bias magnetic field output angle acquisition method according to any one of claims 1-4, and control the three-dimensional Helmholtz coil to output a working bias magnetic field of the required magnitude at the location of the diamond at a horizontal angle b and an included angle a2.

6. The diamond NV color center quantum device based on ODMR technology according to claim 5, characterized in that, It also includes a curve display module, which is used to output at least observable ODMR curves and fluorescence intensity versus angle curves.

7. The diamond NV color center quantum device based on ODMR technology according to claim 5 or 6, characterized in that, It also includes a data acquisition module, which is at least used to track and acquire fluorescence characterization data of the NV axis that coincides with the direction of the working bias magnetic field.

8. A computer-implemented automatic control method, characterized in that, When the initial parameter setting is completed and executed on the data processing hardware, the method causes the data processing hardware to perform the operation of the bias magnetic field output angle acquisition method as described in any one of claims 1-4.

9. The automatic control method according to claim 5, characterized in that, After obtaining the bias magnetic field output angle, the three-dimensional Helmholtz coil is controlled to output the required working bias magnetic field at the location of the diamond according to the horizontal angle b and the included angle a2.

10. A storage medium, characterized in that, The storage medium stores a computer program, which, when executed by the data processing hardware, can perform the operation of the automatic control method as described in any one of claims 8 or 9 after the initial parameter settings are completed.

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