Quantum detection system and detection method

Abstract

The application relates to the technical field of quantum precision measurement, and is a kind of quantum detection system and detection method, which is used for detecting a to-be-measured microwave field generated by an external microwave radiation device, and comprises a quantum probe, a light source, a bias magnetic field module, a fluorescence detection module and a data processing module; the present scheme utilizes the corresponding relationship among diamond NV color centers, microwaves, light and magnetic fields, and designs a quantum microwave detection method and system capable of measuring external microwave fields; the quantum precision measurement technology can be used to realize accurate measurement of the microwave field; by arranging the bias magnetic field module, the energy level splitting degree of the diamond NV color center can be adjusted, and the resonance frequency of the diamond NV color center can be changed, so that 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 application relates to the technical field of quantum precision measurement, and particularly to a quantum detection system and a detection method. BACKGROUND

[0002] In recent years, the solid-state spin color center system has developed rapidly in the field of quantum precision measurement. A detection method mainly 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 and quantization 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] The present application is based on the principle of optical detection magnetic resonance, and considers the corresponding relationship between microwave, light and magnetic field and the diamond NV color center. A new method and system for measuring microwave field are proposed. The high sensitivity of the diamond NV color center is used to realize high-precision measurement of the microwave field. The research results have wide application scenarios and can be used for antenna radiation structure detection, microwave electromagnetic interference detection, etc. SUMMARY

[0004] The present application provides a quantum detection system and a detection method, which realizes accurate measurement of the microwave field by the high sensitivity and high precision characteristics of the diamond NV color center.

[0005] To achieve the above object, the present application provides the following technical scheme:

[0006] A quantum detection system for detecting a to-be-measured microwave field generated by an external microwave radiation device, comprising:

[0007] A quantum probe for sensing the to-be-measured microwave field, which comprises a diamond containing an NV color center;

[0008] A light source for emitting excitation light, the excitation light being configured to irradiate the diamond to generate photo-induced fluorescence;

[0009] A bias magnetic field module for generating a bias magnetic field, the bias magnetic field being configured to adjust the energy level splitting degree of the NV color center so that it can be affected by the to-be-measured microwave field and produce spin flipping;

[0010] A fluorescence detection module for collecting the photo-induced fluorescence and generating a detection signal;

[0011] A data processing module for analyzing and processing the detection signal and displaying.

[0012] 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 arranged at a side end face of the transmission optical fiber.

[0013] The quantum detection system as described above, in some embodiments of the present application, 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 are connected with the diamond through a displacement adjustment structure.

[0014] The quantum detection system as described above, in some embodiments of the present application, the bias magnetic field is generated by a permanent magnet arranged around the diamond.

[0015] The quantum detection system as described above, in some embodiments of the present application, the bias magnetic field is provided by a power coil arranged around the diamond.

[0016] The quantum detection system as described above, in some embodiments of the present application, the power coil is electrically connected with a data processing module, and the data processing module comprises an electric-microwave frequency conversion database, according to which the data processing module can obtain the frequency of the microwave field to be measured according to the working voltage of the power coil.

[0017] The quantum detection system as described above, in some embodiments of the present application, the diamond contains a system of NV color centers, which comprises four color center axial directions, and the direction of the bias magnetic field is configured to have equal angles with the four color center axial directions of the diamond.

[0018] The quantum detection system as described above, in some embodiments of the present application, further comprises a microwave module configured to provide a microwave signal to an external microwave radiation device.

[0019] Another aspect of the present application also provides a detection method, which applies the quantum detection system as described in any one of the preceding aspects, comprising:

[0020] Step 1: Adjust the relative position of the quantum probe and the external microwave radiation device so that the diamond is located in the effective detection area.

[0021] Step 2: Start the quantum detection system, adjust the bias magnetic field module and observe the detection signal, and when the expected change of the detection signal appears, stop adjusting the bias magnetic field module and maintain it in the current state, that is, the formal detection can be started.

[0022] Further, when adjusting the bias magnetic field module, the change of the detection signal is observed, and when the detection signal appears continuous change, the adjustment process is stopped at the place where the change amplitude is the largest.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The scheme utilizes the correspondence among the diamond NV color center, the microwave, and the optical-magnetic field, and designs a quantum microwave detection method and system capable of measuring external microwave field, which can realize accurate measurement of the microwave field based on quantum precision measurement technology.

[0025] The scheme can adjust the energy level splitting degree of the diamond NV color center through the bias magnetic field module, and further change the 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 DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed for the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0027] Figure 1 The module diagram of the quantum detection system in embodiment one;

[0028] Figure 2 The ODMR spectrum diagram under zero magnetic field and 1.19mT magnetic field;

[0029] Figure 3 The structural schematic diagram of the bias magnetic field module in embodiment one;

[0030] Figure 4 The module diagram of the quantum detection system containing the microwave module in embodiment one;

[0031] Figure 5 The specific structural design diagram of the quantum detection system in embodiment one;

[0032] Figure 6 The detection method flowchart in embodiment two.

[0033] Explanation of reference signs:

[0034] 1, cylinder holder; 2, center through hole; 3, magnetic ring; 4, straight tube; 5, optical fiber; 6, diamond; 7, platform; 8, support; 9, probe base; 10, probe; 11, bias magnetic source; 12, electric displacement table; 13, object table; 101, sensing optical fiber; 111, magnetic source mounting seat. DETAILED DESCRIPTION

[0035] The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and cannot be interpreted as a limitation on the present application.

[0036] For the purposes of the present application embodiments, the technical solutions and advantages to be clearer, now one or more embodiments are described with reference to the accompanying drawings, wherein similar reference signs are used throughout to refer to similar components. In the following description, for the purpose of explanation, numerous specific details are set forth in order to provide a more thorough understanding of one or more embodiments. It is apparent, however, that one or more embodiments can be practiced without these specific details in various circumstances, each embodiment can be mutually combined with each other without contradiction.

[0037] <Embodiment One>

[0038] Referring to the accompanying drawings Figure 1 , the present embodiment discloses a quantum detection system for detecting a to-be-detected microwave field generated by an external microwave radiation device, comprising a quantum probe, a light source, a bias magnetic field module, a fluorescence detection module and a data processing module.

[0039] In the present case, the quantum probe is used to perceive the to-be-detected microwave field, and its structure comprises a diamond containing NV centers, which can be single or an ensemble; in a preferred design, the quantum probe further comprises a transmission optical fiber, the diamond is arranged at one side end face of the transmission optical fiber, the excitation light enters the diamond from the other side of the transmission optical fiber and acts on the diamond, and the photoluminescence generated by the diamond is also transmitted back along the transmission optical fiber and collected by the subsequently connected fluorescence detection module; preferably, the transmission optical fiber is a multimode optical fiber; the diamond and the transmission optical fiber can be bonded by optical cement.

[0040] In the present case, the light source is used to output excitation laser, and the excitation light is configured to irradiate the diamond to make it produce photoluminescence; for the diamond NV center, the wavelength of the excitation light is generally 532 nm, and under the irradiation of this laser, the diamond NV center will produce red photoluminescence; 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 and irradiate the diamond.

[0041] In the present case, the bias magnetic field module is used to generate a bias magnetic field, which is configured to adjust the energy level splitting degree of the NV center so that it can be acted on by the to-be-detected microwave field and produce spin flipping; regarding the NV center, using laser to irradiate the NV center will produce red fluorescence, and its ground state exists m s =0 state and m s =±1 state, based on its quantum characteristics, the red fluorescence intensity produced by m s =±1 state will be weaker than that of m s =0 state, and a microwave signal of 2.87 GHz frequency will make m s =0 state to m s=±1 state transition (i.e., spin flip), meaning that when an external microwave field with a frequency of 2.87 GHz is applied, the red fluorescence will significantly weaken. See Appendix. Figure 2 The upper spectral line shows that the diamond NV color center will produce a resonance absorption peak at a microwave frequency of 2.87 GHz. Furthermore, the change in microwave power is related to the intensity of red fluorescence. Therefore, we can use the diamond NV color center to sense an external microwave field at a frequency of around 2.87 GHz. By sensing the change in fluorescence, we can determine whether there is a microwave field of the corresponding frequency in the outside world, or sense the change in the power of the microwave field (such as determining whether the antenna radiates microwaves uniformly, or finding the optimal microwave radiation area).

[0042] However, in reality, the frequency of the microwave field in many detection scenarios is not around 2.87 GHz, making it essential to improve the microwave frequency detection range of the detection system. Based on this issue, we combine the characteristics of NV color centers, i.e., the ground state m-value when an external magnetic field is applied. s The ±1 state will undergo Zeeman splitting, dividing into m s =+1 state and m s =-1 state, at which point the microwave resonant frequency of the diamond NV color center will change, at m s =+1 state and m s The -1 state will each have a microwave resonance frequency, and the two are symmetrical about the frequency 2.87 GHz, which will be shown in the ODMR spectrum as follows. Figure 2 As shown in the upper and lower spectral lines, two resonance absorption peaks are generated. The experiment found that the stronger the external magnetic field, the farther the center distance between the two resonance absorption peaks. In other words, the microwave frequency that the diamond NV color center can sense has changed. Therefore, we designed a bias magnetic field module in the solution to apply external magnetic fields of different magnitudes to the diamond NV color center, thereby changing the microwave frequency range that the detection system can sense and improving the applicability of the system.

[0043] In some designs, the bias magnetic field module is a permanent magnet positioned near the diamond, capable of shifting its position to change the distance from the diamond, thus altering the magnitude of the bias magnetic field. However, in this design, the strength of the bias magnetic field provided by the permanent magnet is relatively weak, and the detectable microwave frequency range is insufficient. Therefore, a preferred solution is to fabricate the bias magnetic field module as comprising several concentrically arranged magnetic rings. 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 rings, and the magnetic rings and the diamond are connected by a displacement adjustment structure. An exemplary structure is shown in the attached figure. Figure 3As shown, it comprises a I-shaped cylinder frame 1 and a straight tube 4 with external threads on the surface, several magnetic rings 3 are sleeved on the cylinder frame 1, the straight tube 4 is sleeved on the optical fiber 5 connected with the diamond 6 and is located close to the side of the diamond 6, the central through hole 2 of the cylinder frame 1 is provided with internal threads, and the cylinder frame 1 and the straight tube 4 can be connected through the internal and external threads. In use, the distance between the magnetic ring 3 and the diamond 6 can be adjusted by rotating the cylinder frame 1, and then the bias magnetic field strength is adjusted, and the microwave frequency sensing range is increased. In addition, when using a permanent magnet as a bias magnetic field module, due to the irregularity of the magnetic field direction, when the permanent magnet is moved, the signal-to-noise ratio of the detection signal may be reduced. In the foregoing preferred structure 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.

[0044] In some other scheme designs, the bias magnetic field module can also be a power coil, which is arranged around the diamond. Here, the periphery includes the position design of the foregoing permanent magnet and the position design of the magnetic ring structure.

[0045] In actual detection, the frequency of the external microwave field is often unknown (mainly because some detection scenes do not need to know the frequency information to achieve detection, such as microwave interference detection, which does not need to detect the specific microwave frequency, and for microwave antennas and other radiating devices, only the change in microwave power caused by design defects needs to be sensed). However, knowing the microwave frequency can better help analyze the data. In order to obtain this function, in some example scheme designs, in combination with the design that the bias magnetic field module is a power coil, the power coil can be electrically connected with a data processing module. The data processing module comprises an electric-microwave frequency conversion database (this database can be completed in a laboratory. The size of the current in the power coil is changed, the microwave field with a known frequency is measured, when the photoluminescence is weakest, the size of the current corresponding to the frequency of the microwave is marked, by changing the frequency of the microwave field, the size of the current in the power coil corresponding to each microwave frequency that can be used for sensing is obtained, and the data is summarized to construct the electric-microwave frequency conversion database. In actual detection, according to the electric-microwave frequency conversion database, the frequency of the microwave field to be detected can be inversely deduced according to the working voltage of the power coil.

[0046] In this example, the fluorescence detection module is used to collect the photoluminescence and generate a detection signal. As some preferred designs, the fluorescence detection module comprises a photodiode (such as an avalanche diode) and a filtering structure (filter). The photoluminescence directed to the photodiode needs to be filtered by the filtering structure in advance.

[0047] In the present case, the data processing module is used for analyzing and displaying the detection signal; in some specific designs, the data processing module is included in the host computer, and at least the program method for analyzing the microwave field according to the detection signal, the function module for realizing the ODMR spectrum drawing, etc. are recorded in the internal.

[0048] In a preferred example, a diamond containing ensemble NV color centers is selected, which contains four color center axial directions. At the same time, the angle between the direction of the bias magnetic field and the four color center axial directions of the diamond is equal. In this way, the components of the bias magnetic field in each color center axial direction are equal, which will only appear a pair of peaks on the ODMR spectrum, as shown in the upper and lower spectra. Figure 2 In this case, the response of the photoluminescence change is most obvious, and maintaining this magnetic field orientation design for detection can effectively improve the measurement response. Further, considering that in the preferred example, the bias magnetic field needs to be moved and adjusted, 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 axial directions of the diamond. Therefore, the bias magnetic field module needs to be optimized and designed. In an exemplary scheme, the structure design of the magnetic ring in the foregoing example can meet this requirement, and this structure design can be used as a bias magnetic field module and applied to this place.

[0049] In some detection situations, such as performance detection of microwave radiation structures (such as antennas, microstrip antennas), they often cannot generate microwave fields autonomously for detection. To solve this problem, as a preferred design, as shown in the lower part of FIG. 1, the quantum detection system in the present scheme can also be configured with a microwave module. Figure 4 The microwave module can be configured to provide a microwave signal to an external microwave radiation device, 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.

[0050] To facilitate understanding of the present embodiment, an exemplary structure and composition design of a quantum detection system is introduced here, as shown in FIG. 2. Figure 5As shown, it comprises a platform 7, a support 8, a probe holder 9, a probe 10, a bias magnetic source 11, an electric displacement table 12, a carrier table 13, a control cabinet (not shown in the figure) and a host computer (not shown in the figure), the platform 7 is distributed with mounting positioning holes, the support 8 is mounted on the platform 7, the support 8 comprises a support rod and a top mounting plate, the probe holder 9 is used for clamping the probe 10, which can move along the XYZ three-axis, preferably, it can realize fine adjustment of micrometer level in the longitudinal direction; the probe 10 comprises a sensing optical fiber 101 and a diamond NV color center arranged at one side end of the sensing optical fiber 101, the other end of the sensing optical fiber 101 is connected with the control cabinet, the control cabinet is connected with the host computer, the control cabinet comprises a laser output module for outputting excitation light, a fluorescence collection module for collecting photoluminescence and a data processing module, the bias magnetic source 11 is a permanent magnet, which is mounted on the top mounting plate of the support through a magnetic source mounting seat 12, during 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 displacement table 12 can realize XYZ three-axis adjustment, which is mounted on the platform 7, the carrier table 13 is mounted on the top surface of the electric displacement table 12, preferably, the carrier table 13 is made of non-metal material, which can effectively shield the influence of the outside and the motor on the measurement during measurement.

[0051] The above structure works as follows: taking a detection antenna as an example, the antenna to be detected is placed on the top surface of the carrier table 13, the probe holder 9 is adjusted so that the diamond NV color center at the bottom end of the probe 10 is located near the antenna, the antenna is connected with an external microwave module to generate a microwave field of a specific frequency, 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 detect the microwave field of this frequency at this time, the position of the bias magnetic source 11 is fixed at this time, the electric displacement table 12 is controlled to move by sending a command through the host computer, 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, the microwave field power at some positions of the antenna will be different, which will affect the intensity of the photoluminescence, and accordingly the performance of the antenna can be judged).

[0052] <Embodiment One>

[0053] As shown in the accompanying drawings, Figure 6 The embodiment discloses a detection method, which applies the quantum detection system as described above, comprising;

[0054] 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;

[0055] In a specific example, such as detecting a microwave antenna, in order to obtain more accurate detection effect, it is better that the front-end diamond NV color center of the quantum probe is closer to the antenna.

[0056] S2: start the quantum detection system, adjust the bias magnetic field module and observe the detection signal, when the detection signal appears the expected change, stop adjusting the bias magnetic field module and maintain it in the current state, that is, the formal detection can be started.

[0057] Specifically, the system operates based on the ODMR method. When the bias magnetic field size is appropriate, it indicates that the microwave field of the current frequency can make the NV color center produce spin flip. At this time, the photoluminescence intensity generated by the diamond NV color center will decay (expected change), and the change of the photoluminescence can be observed by the upper computer to determine whether the position of the bias magnetic field module is appropriate.

[0058] In combination with the ODMR spectrum, it can be known that the microwave near a center frequency can make the NV color center produce spin flip, but the microwave field of the center frequency can maximize the spin flip, that is, the photoluminescence decay at this frequency is the strongest. The detection under the microwave of this frequency has better response sensitivity. Therefore, in some preferred methods, when adjusting the bias magnetic field module, the change of the detection signal is observed, and when the detection signal appears continuous change, the adjustment process is stopped at the maximum change amplitude. At this time, the frequency of the external microwave field can maximize the spin flip of the NV color center, and the response of the detection signal is best.

[0059] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description 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.

[0060] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details, nor limit the application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited by the claims and their entire scope and equivalents.

Claims

1. A quantum detection system for detecting a microwave field to be measured generated by an external microwave radiator, characterized in that The quantum probe comprises: a quantum probe for sensing the microwave field to be measured, the structure of which comprises a diamond containing NV color centers; a light source for outputting excitation light, the excitation light being configured to irradiate the diamond to make it produce photoluminescence; a bias magnetic field module for generating a bias magnetic field, the bias magnetic field being configured to adjust the energy level splitting degree of the NV color centers so that they can be affected by the microwave field to be measured and produce spin flipping; 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 diamond are connected through a displacement adjustment structure; the displacement adjustment structure comprises an I-shaped barrel and a straight pipe with external threads on the surface, a plurality of magnetic rings are sleeved on the barrel, the straight pipe is sleeved on the optical fiber connected with the diamond and located close to one side of the diamond, the central through hole of the barrel is provided with internal threads, and the barrel and the straight pipe are connected through the internal and external threads; a fluorescence detection module for collecting the photoluminescence and generating a detection signal; a data processing module for analyzing and processing the detection signal and displaying the result; wherein the diamond contains a system of NV color centers, which comprises four color center axial directions, and the direction of the bias magnetic field is configured to have equal angles with the four color center axial directions of the diamond.

2. The quantum detection system of claim 1, wherein, The quantum probe comprises a transmission optical fiber, and the diamond is arranged on one side of the transmission optical fiber.

3. The quantum detection system of claim 1, wherein, The bias magnetic field is generated by a permanent magnet arranged around the diamond.

4. The quantum detection system of claim 1, wherein, The bias magnetic field is provided by a powered coil arranged around the diamond.

5. The quantum detection system of claim 4, wherein, The powered coil is electrically connected with the data processing module, and the data processing module comprises an electric-microwave frequency conversion database, according to which the data processing module can obtain the frequency of the microwave field to be measured according to the working voltage of the powered coil.

6. The quantum detection system of claim 1, wherein, The microwave module is further arranged to provide a microwave signal to an external microwave radiation device.

7. A detection method using the quantum detection system according to any one of claims 1 to 6, characterized by, The method comprises: 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; starting the quantum detection system, adjusting the bias magnetic field module and observing the detection signal, when the expected change of the detection signal appears, stopping adjusting the bias magnetic field module and maintaining it in the current state, and then starting the formal detection.

8. The detection method according to claim 7, characterized in that, When adjusting the bias magnetic field module, observe the change of the detection signal, and when the detection signal appears continuous change, stop the adjustment process at the maximum change amplitude.

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