Quantum detection system and detection method

Abstract

The invention relates to the technical field of quantum precision measurement, in particular to a quantum detection system and method, which are used for detecting a to-be-detected microwave field generated by an external microwave radiation device and comprise a quantum probe, a light source, a bias magnetic field module, a fluorescence detection module and a data processing module. According to the scheme, the quantum microwave detection method and system capable of measuring the external microwave field are designed according to the corresponding relation between the diamond NV color center and the microwave-light-magnetic field, accurate measurement of the microwave field can be achieved on the basis of the quantum precision measurement technology, the energy level splitting degree of the diamond NV color center can be adjusted by arranging the bias magnetic field module, and the detection accuracy is improved. Therefore, the measurable frequency range of the diamond NV color center is expanded, and the applicability of the device is improved.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement technology, and in particular to a quantum detection system and a detection method. Background Art

[0002] In recent years, the research on solid-state spin color center systems in the field of quantum precision has developed rapidly, and a detection method based on optical detection magnetic resonance (ODMR) has been developed. By studying the linear relationship between the microwave magnetic resonance frequency and the external magnetic field, the sensing measurement and quantification of the external magnetic field can be realized; in the solid-state quantum system, the diamond nitrogen-vacancy color center (NV color center) is the most representative system. The NV color center is a point defect in diamond, and the fluorescence emission is very stable.

[0003] This scheme is based on the principle of optical detection magnetic resonance. Considering the correspondence between microwave, light and magnetic field and diamond NV color center, a new method and system for measuring microwave field is proposed. By utilizing the high sensitivity characteristics of diamond NV color center, high-precision measurement of microwave field is achieved. This research result has a wide range of application scenarios and can be used for antenna radiation structure detection, microwave electromagnetic interference detection, etc. Summary of the invention

[0004] The present invention proposes a quantum detection system and a detection method, which realize accurate measurement of microwave fields by utilizing the high sensitivity and high precision characteristics of diamond NV color centers.

[0005] To achieve the above object, the present invention provides the following technical solutions: A quantum detection system for detecting a microwave field to be measured generated by an external microwave radiation device, comprising: A quantum probe, used to sense the microwave field to be measured, and comprising a diamond containing an NV color center; a light source for emitting excitation light, wherein the excitation light is configured to illuminate the diamond to cause it to generate photoluminescence; A bias magnetic field module, used to generate a bias magnetic field, wherein the bias magnetic field is configured to adjust the energy level splitting degree of the NV color center so that it can be acted upon by the microwave field to be measured and produce spin flip; A fluorescence detection module, used for collecting the photoinduced fluorescence and generating a detection signal; The data processing module is used to analyze, process and display the detection signal.

[0006] In the quantum detection system as described above, in some embodiments of the present application, the quantum probe comprises a transmission optical fiber, and the diamond is disposed on one end face of the transmission optical fiber.

[0007] In the quantum detection system as described above, in some embodiments of the present application, the bias magnetic field module includes a plurality of concentrically arranged magnetic rings, the diamond is located on the central axis of the magnetic rings, and the magnetic rings and the diamonds are connected via a displacement adjustment structure.

[0008] In the quantum detection system as described above, in some embodiments of the present application, the bias magnetic field is generated by a permanent magnet disposed around the diamond.

[0009] In the quantum detection system as described above, in some embodiments of the present application, the bias magnetic field is provided by a powered coil disposed around the diamond.

[0010] In the quantum detection system as described above, in some embodiments of the present application, the energized coil is electrically connected to a data processing module, and the data processing module includes an electric-to-microwave frequency conversion database. Based on the electric-to-microwave frequency conversion database, the data processing module can derive the frequency of the microwave field to be measured based on the working voltage of the energized coil.

[0011] In the quantum detection system as described above, in some embodiments of the present application, the diamond contains an ensemble NV color center, including four color center axes, and the direction of the bias magnetic field is configured to have equal angles with the four color center axes of the diamond.

[0012] The quantum detection system as described above, in some embodiments of the present application, further comprises a microwave module, wherein the microwave module is configured to provide a microwave signal to an external microwave radiation device.

[0013] Another aspect of the present application also provides a detection method, which uses the quantum detection system as described in any of the preceding items, comprising: Step 1: adjusting the relative position of the quantum probe and the external microwave radiation device so that the diamond is located in the effective detection area; Step 2: Start the quantum detection system, adjust the bias magnetic field module and observe the detection signal. When the detection signal shows the expected change, stop adjusting the bias magnetic field module and maintain it in the current state to start formal detection.

[0014] Furthermore, when adjusting the bias magnetic field module, the change of the detection signal is observed, and when the detection signal changes continuously, the adjustment process is stopped at the point where the change amplitude is the maximum.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This scheme uses the correspondence between diamond NV color centers and microwave-light-magnetic field to design a quantum microwave detection method and system that can measure external microwave fields. Based on quantum precision measurement technology, it can achieve accurate measurement of microwave fields.

[0016] This scheme can adjust the degree of energy level splitting of the diamond NV color center by setting a bias magnetic field module, thereby changing its resonance frequency, so that the measurable frequency range of the diamond NV color center is expanded, and the applicability of the device is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 This is a module diagram of the quantum detection system in Example 1; Figure 2 ODMR spectra under zero magnetic field and 1.19mT magnetic field; Figure 3 is a structural schematic diagram of the bias magnetic field module in Example 1; Figure 4 This is a module diagram of a quantum detection system including a microwave module in Example 1; Figure 5 A specific structural design diagram of the quantum detection system in Example 1; Figure 6 This is a flow chart of the detection method in Example 2.

[0019] Description of reference numerals: 1. Cylinder stand; 2. Center through hole; 3. Magnetic ring; 4. Straight tube; 5. Optical fiber; 6. Diamond; 7. Platform; 8. Bracket; 9. Probe seat; 10. Probe; 11. Bias magnetic source; 12. Electric translation stage; 13. Stage; 101. Sensing optical fiber; 111. Magnetic source mounting seat. DETAILED DESCRIPTION

[0020] The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and should not be construed as limiting the present application.

[0021] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, one or more embodiments are now described with reference to the accompanying drawings, wherein similar reference numerals throughout the text are used to refer to similar components. In the following description, for the purpose of explanation, many specific details are set forth in order to provide a more thorough understanding of one or more embodiments. However, it is clear that in various cases, one or more embodiments can be practiced without these specific details, and the various embodiments can be combined and referenced to each other without contradiction. <Example 1>

[0022] See attached Figure 1 This embodiment discloses a quantum detection system for detecting a microwave field to be measured generated by an external microwave radiation device, including a quantum probe, a light source, a bias magnetic field module, a fluorescence detection module and a data processing module.

[0023] In this example, the quantum probe is used to sense the microwave field to be measured, and its structure includes a diamond containing an NV color center, wherein the NV color center can be a single one or an ensemble. In a preferred design, the quantum probe also includes a transmission optical fiber, wherein the diamond is arranged on one end face of the transmission optical fiber, and the excitation light enters from the other side of the transmission optical fiber and acts on the diamond. The photoluminescence generated by the diamond will also be collected by a subsequently connected fluorescence detection module along with the reverse transmission of the transmission optical fiber. Preferably, the transmission optical fiber is a multimode optical fiber. The diamond and the transmission optical fiber can be bonded by optical glue.

[0024] In this example, the light source is used to output an excitation laser, and the excitation light is configured to irradiate the diamond to cause it to produce photofluorescence; for the diamond NV color center, the wavelength of the excitation light is generally 532nm, and under this laser irradiation, the diamond NV color center will produce red photofluorescence; an exemplary optical path configuration scheme is that after the excitation light is output from the light source, it can enter an optical fiber through a fiber coupler, and be transmitted through the optical fiber optical path to irradiate the diamond.

[0025] In this example, the bias magnetic field module is used to generate a bias magnetic field, and the bias magnetic field is configured to adjust the energy level splitting degree of the NV color center so that it can be acted upon by the microwave field to be measured and produce a spin flip; with respect to the NV color center, irradiating the NV color center with a laser will produce red fluorescence, and its ground state has m s =0 state and m s = ±1 state, based on its quantum properties, m s = ±1 state and m s =0 state, the red fluorescence intensity will be weaker, and the microwave signal with a frequency of 2.87 GHz will make m s =0 state to m s = ±1 state transition (i.e. spin flip), that is, when a microwave field with a frequency of 2.87 GHz is applied externally, the red fluorescence will become significantly weaker, see Appendix Figure 2 In the spectrum line on the upper side, the diamond NV color center will produce a resonant absorption peak at the microwave frequency of 2.87 GHz, and the change in microwave power is also related to the red fluorescence intensity. Therefore, in fact, we can use the diamond NV color center to sense the external microwave field with a frequency of about 2.87 GHz. By sensing the fluorescence changes, we can determine whether there is a microwave field of the corresponding frequency in the outside world, or sense the power changes of the microwave field (such as determining whether the antenna radiates microwaves evenly, or finding the optimal microwave radiation area).

[0026] But in fact, in many detection scenarios, the frequency of the microwave field is not around 2.87 GHz, so it is very necessary to improve the microwave frequency detection range of the detection system. Based on this problem, we combined the characteristics of NV color centers, that is, when an external magnetic field is applied, its ground state m s = ±1 state will undergo Zeeman splitting, which is divided into m s =+1 state and m s = -1 state, at this time the microwave resonance frequency of the diamond NV color center will change. s =+1 state and m s =-1 state will have a microwave resonance frequency, and the two are symmetrical about the frequency 2.87GHz, which is shown in the ODMR spectrum as shown in the following Figure 2 As shown in the upper and lower spectral lines, two resonant absorption peaks are generated, and the experiment found that the stronger the external magnetic field, the farther the center distance of the two resonant absorption peaks. In other words, the microwave frequency that can be sensed by the diamond NV color center has changed. Therefore, we designed a bias magnetic field module in the solution, which applies external magnetic fields of different sizes to the diamond NV color center, changes the microwave frequency range that the detection system can perceive, and improves the applicability of the system.

[0027] In some designs, the bias magnetic field module is a permanent magnet located near the diamond, which can move and change the distance from the diamond, that is, the size of the bias magnetic field can be changed. However, in this design, the strength of the bias magnetic field provided by the permanent magnet is relatively weak, and the changeable microwave frequency detection range is still not large enough. Based on this, the preferred solution is that the bias magnetic field module is made to include a number of concentrically arranged magnetic rings, and a stronger bias magnetic field is obtained by stacking the magnetic rings. More preferably, the diamond is located on the central axis of the magnetic ring, and the magnetic ring and the diamond are connected by a displacement adjustment structure. The exemplary structure is shown in the attached figure. Figure 3 As shown, it includes an I-shaped tube frame 1 and a straight tube 4 with external threads on the surface, a plurality of magnetic rings 3 are sleeved on the tube frame 1, the straight tube 4 is sleeved on the optical fiber 5 connected to the diamond 6 and is located close to the side of the diamond 6, and an internal thread is provided in the central through hole 2 of the tube frame 1, and the tube frame 1 and the straight tube 4 can be connected by the internal and external threads. When in use, by rotating the tube frame 1, the distance between the magnetic ring 3 and the diamond 6 can be adjusted, and then the bias magnetic field strength can be adjusted to increase the microwave frequency perception range; in addition, when a permanent magnet is used as a bias magnetic field module, due to the irregularity of its magnetic field direction, when the permanent magnet is moved, the signal-to-noise ratio of the detection signal may be reduced, and in the aforementioned preferred structural design, no matter how the magnetic ring moves, the diamond is always located on the central axis of the magnetic ring, and at this position, the bias magnetic field direction is uniform and stable, which can ensure the signal-to-noise ratio of the detection signal.

[0028] In some other design schemes, the bias magnetic field module can also be an energized coil, which is arranged around the diamond, and the periphery here includes the position design of the aforementioned permanent magnet and the position design of the magnetic ring structure.

[0029] Taking into account that in actual detection, the frequency of the external microwave field is often unknown (mainly some detection scenarios do not require knowing the frequency information to achieve detection, such as for microwave interference detection, there is no need to detect the specific microwave frequency. For radiation devices such as microwave antennas, it is only necessary to perceive the microwave power changes caused by design defects), but knowing the microwave frequency can better help analyze the data. In order to obtain this function, in some exemplary scheme designs, the bias magnetic field module is combined with the design of an energized coil, and the energized coil can be electrically connected to the data processing module. The data processing module includes an electric-microwave frequency conversion database (the database can be completed in the laboratory, by changing the current in the energized coil, measuring the microwave field of known frequency, and when the measured photoluminescence is the weakest, the current is marked with the microwave of that frequency. By changing the microwave field frequency, the current in the energized coil that can be used for perception corresponding to each microwave frequency is obtained, and the data can be summarized to construct an electric-microwave frequency conversion database). In actual detection, according to the electric-microwave frequency conversion database, the frequency of the microwave field to be measured can be inferred according to the working voltage of the energized coil.

[0030] In this example, the fluorescence detection module is used to collect the photofluorescence and generate a detection signal; as some preferred designs, the fluorescence detection module includes a photodiode (such as an avalanche diode) and a filtering structure (filter), and the photofluorescence directed to the photodiode needs to be filtered out of stray light by the filtering structure in advance.

[0031] In this example, the data processing module is used to analyze, process and display the detection signal; in some specific designs, the data processing module is included in the host computer, which at least has recorded therein a program method for performing microwave field analysis based on the detection signal, a functional module for realizing ODMR spectrum line drawing, etc.

[0032] In a preferred example, a diamond containing an ensemble NV color center is selected. This diamond contains four color center axes. At the same time, we set the direction of the bias magnetic field to be equal to the angles between the four color center axes of the diamond. In this way, the components of the bias magnetic field on each color center axis are equal, which is reflected in the ODMR spectrum as only one pair of peaks, as shown in the attached figure. Figure 2As shown in the spectrum lines on the upper and lower sides, in this case, the responsiveness of the change in photoluminescence is the most obvious. Maintaining this magnetic field orientation design for detection can effectively improve the measurement responsiveness. Further, considering that in this preferred example, the bias magnetic field needs to be movable and adjustable, in order to ensure that no secondary calibration is required during the adjustment process, the direction of the bias magnetic field can still be equal to the angle between the four color center axes of the diamond, then the bias magnetic field module needs to be optimized and designed. In the exemplary scheme, the structural design of the magnetic ring form in the aforementioned example can meet this requirement, and this structural design can be used as a bias magnetic field module for application here.

[0033] In some testing scenarios, such as the performance test of microwave radiation structures (such as antennas and microstrip antennas), they often cannot generate microwave fields autonomously for testing. To solve this problem, as an optimal design, the attached Figure 4 As shown, the quantum detection system in this solution can also be configured with a microwave module, which is configured to provide microwave signals to external microwave radiation devices, and the microwave module can be controlled by the data processing module. As some preferred designs, the microwave module can include a microwave source, a microwave amplifier and a microwave circulator, the microwave source is the emission source of the microwave signal, the microwave amplifier can amplify the microwave power, and the microwave circulator can prevent the reverse transmission of the microwave signal.

[0034] To facilitate understanding of this embodiment, an exemplary structure and composition design of a quantum detection system is introduced here, as shown in the attached Figure 5 As shown, it includes a platform 7, a bracket 8, a probe seat 9, a probe 10, a bias magnetic source 11, an electric translation stage 12, a stage 13, a control cabinet (not shown in the figure) and a host computer (not shown in the figure). The platform 7 is provided with mounting holes, the bracket 8 is installed on the platform 7, the bracket 8 includes a support rod and a top mounting plate, the probe seat 9 is used to clamp the probe 10, which can be moved along the XYZ three-axis direction, preferably, it can achieve micron-level fine adjustment in the longitudinal direction; the probe 10 includes a sensing optical fiber 101 and a diamond NV color center arranged at one end of the sensing optical fiber 101, and the other end of the sensing optical fiber 101 is connected to the control cabinet The control cabinet is connected to the host computer. The control cabinet includes a laser output module for outputting excitation light, a fluorescence acquisition module for collecting photofluorescence, and a data processing module. The bias magnetic source 11 is a permanent magnet, which is mounted on the top mounting plate of the bracket through a magnetic source mounting seat 12. When in use, the distance and orientation of the bias magnetic source 11 relative to the diamond NV color center can be adjusted through the magnetic source mounting seat 111; the electric translation stage 12 can realize XYZ three-axis adjustment, which is installed on the platform 7, and the stage 13 is installed on the top surface of the electric translation stage 12. Preferably, the stage 13 is made of non-metallic material to effectively shield the influence of the outside world and the motor on the measurement during measurement.

[0035] When the above structure is working, taking the detection antenna as an example, the antenna to be tested is placed on the top surface of the stage 13, and the probe seat 9 is adjusted so that the diamond NV color center at the bottom of the probe 10 is located near the top of the antenna. The antenna is connected to an external microwave module to generate a microwave field of a specific frequency, and the position of the bias magnetic source 11 is adjusted until the attenuation change of the photoluminescence signal appears on the display screen of the host computer, indicating that the system can now detect the microwave field of this frequency. At this time, the position of the bias magnetic source 11 is fixed and the upper computer sends commands to control the movement of the electric translation stage 12, so that the probe 10 covers the area where the detection antenna is located, and the detection signal of the area where the antenna is located is obtained (due to design defects of the antenna, the microwave field power at some positions will be different, which will affect the intensity of the photoluminescence, and the antenna performance can be judged based on this). <Example 1>

[0036] As attached Figure 6 As shown, this embodiment discloses a detection method, which applies the quantum detection system as described above, including: S1: adjusting the relative position of the quantum probe and the external microwave radiation device so that the diamond is located in the effective detection area; In a specific example, such as detecting a microwave antenna, in order to obtain a more accurate detection effect, the diamond NV color center at the front end of the quantum probe is as close to the antenna as possible.

[0037] S2: Start the quantum detection system, adjust the bias magnetic field module and observe the detection signal. When the detection signal shows the expected change, stop adjusting the bias magnetic field module and maintain it in the current state to start formal detection.

[0038] Specifically, this system operates based on the ODMR method. When the bias magnetic field is of appropriate size, it means that the microwave field of the current frequency can cause the NV color center to produce a spin flip. At this time, the photoluminescence intensity generated by the diamond NV color center will decay (expected change). The change in photoluminescence found by the host computer can be used to determine whether the position of the bias magnetic field module is appropriate.

[0039] Combined with the ODMR spectrum, it can be seen that microwaves near a center frequency can cause the NV color center to produce a spin flip, but the microwave field at the center frequency can maximize the spin flip, that is, the photoluminescence attenuation at this time is the strongest, and detection under microwaves of this frequency has a better response sensitivity. Therefore, in some preferred methods, when adjusting the bias magnetic field module, observe the changes in the detection signal. When the detection signal changes continuously, stop the adjustment process at the point where the change amplitude is the largest. At this time, the frequency of the external microwave field can maximize the NV color center spin flip, and the detection signal has the best responsiveness.

[0040] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0041] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A quantum detection system for detecting a microwave field to be measured generated by an external microwave radiation device, characterized in that: include: A quantum probe, used to sense the microwave field to be measured, and comprising a diamond containing an NV color center; A light source for outputting excitation light, wherein the excitation light is configured to illuminate the diamond to cause it to generate photoluminescence; A bias magnetic field module, used to generate a bias magnetic field, wherein the bias magnetic field is configured to adjust the energy level splitting degree of the NV color center so that it can be acted upon by the microwave field to be measured and produce spin flip; A fluorescence detection module, used for collecting the photoinduced fluorescence and generating a detection signal; The data processing module is used to analyze, process and display the detection signal.

2. The quantum detection system according to claim 1, characterized in that The quantum probe comprises a transmission optical fiber, and the diamond is arranged on one end face of the transmission optical fiber.

3. The quantum detection system according to claim 1, characterized in that The bias magnetic field module comprises a plurality of concentrically arranged magnetic rings, the diamond is located on the central axis of the magnetic rings, and the magnetic rings and the diamonds are connected via a displacement adjustment structure.

4. The quantum detection system according to claim 1, characterized in that The bias magnetic field is generated by a permanent magnet disposed around the diamond.

5. The quantum detection system according to claim 1, characterized in that: The bias magnetic field is provided by a powered coil arranged around the diamond.

6. The quantum detection system according to claim 5, characterized in that: The energized coil is electrically connected to a data processing module, which includes an electric-microwave frequency conversion database. Based on the electric-microwave frequency conversion database, the data processing module can derive the frequency of the microwave field to be measured according to the working voltage of the energized coil.

7. The quantum detection system according to claim 1, characterized in that: The diamond contains an ensemble NV color center, including four color center axes, and the direction of the bias magnetic field is configured to have equal angles with the four color center axes of the diamond.

8. The quantum detection system according to claim 1, characterized in that: Also included is a microwave module, which is configured to provide a microwave signal to an external microwave radiation device.

9. A detection method, using the quantum detection system according to any one of claims 1 to 8, characterized in that: Include; Adjusting the relative position of the quantum probe and the external microwave radiation device so that the diamond is located in the effective detection area; Start the quantum detection system, adjust the bias magnetic field module and observe the detection signal. When the detection signal shows the expected change, stop adjusting the bias magnetic field module and maintain it in the current state to start formal detection.

10. The detection method according to claim 9, characterized in that: When adjusting the bias magnetic field module, observe the changes in the detection signal. When the detection signal changes continuously, stop the adjustment process at the point where the change amplitude is the largest.

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