High-sensitivity differential magnetic acquisition system for NV color centers based on frequency-agile microwave modulation technology

Abstract

The present invention discloses a high-sensitivity differential magnetic acquisition system for NV color centers based on frequency-agile microwave modulation technology, including a magnetic signal calibration module, an optical system module, a signal processing module, a microwave signal generation module, and a signal control module. The beneficial effects of the present invention are as follows: when magnetic fields of different sizes and directions are applied to diamond, the double resonance peak system can identify the direction and size of the magnetic field like a single resonance peak system, and the change in voltage amplitude is about twice that of a single resonance peak system, and its magnetic sensitivity and resolution are also improved by 2 times; when the surface temperature of the diamond changes, the zero-field splitting D of the ODMR signal curve changes, and the two symmetrical resonance peaks of the ODMR spectrum drift in the same direction, and the temperature makes the voltage signal generated by the NV color center produce the same amount of change. After differential processing, the application of this system has a strong inhibitory effect on temperature noise.

Description

Technical Field

[0001] The present invention relates to a high-sensitivity differential magnetic acquisition system for NV color centers, in particular to a high-sensitivity differential magnetic acquisition system for NV color centers based on agile frequency microwave modulation technology, and belongs to the field of quantum sensing technology. Background Art

[0002] New magnetic materials and magnetic detection devices are constantly emerging. With the rapid development of magnetic sensors and weak magnetic measuring instruments, weak magnetic detection has also been greatly developed. Weak magnetic detection has a wide range of applications in scientific research, resource exploration, military and other fields. Among them, the application in the military field is one of the main factors promoting weak magnetic detection. Its application in the military field is mainly concentrated in unexploded object detection, fighter and missile navigation, satellite navigation, etc. Therefore, the integrated diamond NV sensor solution is of great significance to the development of my country's national defense construction and other fields.

[0003] In recent years, quantum precision measurement technology has developed rapidly, and the atomic-scale defect nitrogen vacancy (NV) center in diamond is undoubtedly one of the most influential representatives. Due to its long spin lifetime at room temperature, coherent microwave (MW) spin manipulation, optical spin state initialization and readout, and good biocompatibility, sensors based on NV centers have a wide range of practical applications. Based on the Zeeman splitting of the NV ensemble under an external magnetic field, and according to the ground state Hamiltonian intrinsic equation of the NV color center, high-precision detection of weak magnetic fields can be achieved. Summary of the invention

[0004] The purpose of the present invention is to provide a high-sensitivity differential magnetic acquisition system for NV color centers based on agile frequency microwave modulation technology in order to solve at least one of the above technical problems.

[0005] The present invention achieves the above-mentioned purpose through the following technical solutions: a high-sensitivity differential magnetic acquisition system of NV color center based on frequency-agile microwave modulation technology, and its experimental platform includes

[0006] A magnetic signal calibration module, comprising a magnetic coil for applying a bias magnetic field;

[0007] An optical system module, comprising a diamond sample containing NV color centers, a laser for emitting laser light, a bandpass filter for allowing light of a specific wavelength range to pass through, a dichroic mirror capable of generating a bidirectional light path, and a photodetector for receiving a fluorescence signal, wherein the diamond sample is fixed on a microwave antenna, the laser emitted by the laser irradiates the dichroic mirror, the diamond sample is arranged on one side of the dichroic mirror, and the photodetector is arranged on the other side of the dichroic mirror;

[0008] A signal processing module, comprising a lock-in amplifier for amplifying the photoelectric signal received by the photoelectric detector;

[0009] A microwave signal generating module, comprising a microwave signal source for generating a microwave signal for a diamond sample;

[0010] A signal control module, comprising an FPGA module for controlling the microwave signal source;

[0011] The data acquisition module acquires data through the FPGA module 11.

[0012] As a further solution of the present invention: an objective lens 1 is arranged between the diamond sample and the dichroic mirror, and an objective lens 2 is arranged between the dichroic mirror and the photodetector.

[0013] As a further solution of the present invention: a filter is further arranged between the dichroic mirror and the photodetector and close to the dichroic mirror side.

[0014] The NV color center high-sensitivity differential magnetic acquisition system based on agile frequency microwave modulation technology includes the following steps:

[0015] Step 1: Build an experimental platform, turn on the microwave signal source and laser, and use the FPGA module to control the microwave signal source to generate a sweep signal;

[0016] Step 2: Adjust the oscilloscope, observe the ODMR signal on the oscilloscope, and find the microwave frequency F corresponding to the ODMR half-width P1 、F P2 ;

[0017] Step 3: Use the FPGA module 11 to control the microwave signal source 12 to generate a frequency modulation signal, and control the microwave signal source 12 to generate a frequency modulation signal based on the frequency modulation. P1 -F P2 Both of them change frequency quickly;

[0018] Step 4: The modulated high-frequency ODMR signal is mixed into a magnetically sensitive DC signal in the lock-in amplifier 10;

[0019] Step 5: Control the frequency conversion of the microwave signal source and the on / off of FPGA acquisition and the address area of ​​the acquired data storage according to the timing sequence;

[0020] Step 6: Change the magnetic field size to obtain multiple sets of data, and use a PC to process the output data and obtain the final result.

[0021] As a further solution of the present invention: in the step 4, the fluorescent signal received by the photodetector is converted into a weak electrical signal and connected to an oscilloscope via a data line.

[0022] As a further solution of the present invention: in the step 4, the voltage signal output by the photodetector is input into a phase-locked amplifier, and the phase-locked amplifier has integrated circuits such as amplification, mixing, and filtering.

[0023] As a further solution of the present invention: the phase-locked amplifier has two output ports, one of which outputs the real part Vi of the demodulated signal, and the other outputs the imaginary part Vj of the demodulated signal, and then the two signals are input into the FPGA module for processing.

[0024] As a further solution of the present invention: in step 3, FPGA controls the microwave signal source to generate a variable frequency microwave signal, specifically including:

[0025] ①FPGA first controls the microwave source to generate two resonant frequencies F P1 and F P2 ;

[0026] ② After EA detects the rising edge signal 0→1, the FPGA clock signal CLK starts to generate a square wave signal (period is 2ms, duty cycle is 50%). When CLK is high, the microwave source is at the resonant frequency F P1 And around F P1 generating a modulation signal;

[0027] ③When CLK is low, it is at the resonant frequency F P2 And around F P2 generating a modulation signal;

[0028] ④DAT wave is used to control FPGA to collect signals. When DAT is low, FPGA does not collect signals. When DAT is high and CLK is high, it means that it is an odd number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the odd number of ms. When DAT is high and CLK is low, it means that it is an even number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the even number of ms.

[0029] ⑤ When FPGA detects the falling edge of the EA signal, FPGA stops generating the clock signal, the microwave source stops working, and the amplitude and phase of the modulation signal are adjusted by the host control system.

[0030] In step 6, the processing of data specifically includes:

[0031] The FPGA is used to collect the two voltage signals V i and V j The data of odd-numbered milliseconds are placed as a group (V i1 , V j1 ), the data of even-numbered milliseconds are placed in a group (Vi2 , V j2 ); Then solve the amplitude of the odd-numbered signal V1 and the even-numbered signal V2 respectively, and then use FPGA to perform differential operation on the two groups of signals, and finally obtain a set of voltage data V sensitive to magnetic signals x , and then transmit it to the PC for noise spectrum detection. The PC solves the collected data based on the magnetometer sensitivity analysis algorithm based on signal-to-noise ratio analysis.

[0032] The beneficial effects of the present invention are:

[0033] 1. When magnetic fields of different sizes and directions are applied to diamond, the double resonance peak system can identify the direction and size of the magnetic field like the single resonance peak system. The change in voltage amplitude is about twice that of the single resonance peak system, and its magnetic sensitivity and resolution are also improved by 2 times;

[0034] 2. When the surface temperature of diamond changes, the zero field splitting D of the ODMR signal curve changes, and the two symmetrical resonance peaks of the ODMR spectrum drift in the same direction. Temperature makes the voltage signals V1 and V2 generated by the NV color center change in the same amount. After differential processing, the application of this system has a strong suppression effect on temperature noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the module structure of the present invention;

[0036] Figure 2 It is a schematic diagram of the system flow of the present invention;

[0037] Figure 3 This is a schematic diagram of an ODMR signal of the present invention;

[0038] Figure 4 This is a schematic diagram of storing data collected by odd-numbered ms and even-numbered ms of the present invention;

[0039] Figure 5 It is a timing diagram of FPGA of the present invention.

[0040] In the figure: 1. magnetic coil, 2. diamond sample, 3. microwave antenna, 4. objective lens 1, 5. laser, 6. dichroic mirror, 7. filter, 8. objective lens 2, 9. photodetector, 10. lock-in amplifier, 11. FPGA module, 12. microwave signal source. DETAILED DESCRIPTION

[0041] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] Embodiment 1

[0043] like Figure 1 As shown in the figure, the NV color center high-sensitivity differential magnetic acquisition system based on frequency-agile microwave modulation technology has an experimental platform including

[0044] A magnetic signal calibration module, comprising a magnetic coil 1 for applying a bias magnetic field;

[0045] An optical system module, comprising a diamond sample 2 containing NV color centers, a laser 5 for emitting laser light, a bandpass filter for allowing light of a specific wavelength range to pass through, a dichroic mirror 6 capable of generating a bidirectional light path, and a photodetector 9 for receiving a fluorescence signal, wherein the diamond sample 2 is fixed on a microwave antenna 3, the laser light emitted by the laser 5 irradiates the dichroic mirror 6, the diamond sample 2 is arranged on one side of the dichroic mirror 6, and the photodetector 9 is arranged on the other side of the dichroic mirror 6;

[0046] A signal processing module, comprising a lock-in amplifier 10 for amplifying the photoelectric signal received by the photoelectric detector 9;

[0047] A microwave signal generating module, comprising a microwave signal source 12 for generating a microwave signal for the diamond sample 2;

[0048] A signal control module, comprising an FPGA module 11 for controlling the microwave signal source 12;

[0049] The data acquisition module acquires data through the FPGA module 11.

[0050] In the embodiment of the present invention, an objective lens 1 4 is arranged between the diamond sample 2 and the dichroic mirror 6, and an objective lens 2 8 is arranged between the dichroic mirror 6 and the photodetector 9, so that the red fluorescence reflected by the diamond sample 2 can be converted into collimated light, which can then be easily received by the photodetector 9.

[0051] In the embodiment of the present invention, a filter 7 is further provided between the dichroic mirror 6 and the photodetector 9 and close to the dichroic mirror 6 to filter out the useless green laser light, thereby ensuring that the photodetector 9 only receives useful photoelectric signals.

[0052] Embodiment 2

[0053] like Figures 2 to 5 As shown, a high-sensitivity differential magnetic acquisition system for NV color centers based on frequency-agile microwave modulation technology includes the following steps:

[0054] Step 1: Build an experimental platform, turn on the microwave signal source 12 and the laser 5, and use the FPGA module 11 to control the microwave signal source 12 to generate a frequency sweep signal;

[0055] Step 2: Adjust the oscilloscope, observe the ODMR signal on the oscilloscope, and find the microwave frequency F corresponding to the ODMR half-width P1 , F P2 ;

[0056] Step 3: Use the FPGA module 11 to control the microwave signal source 12 to generate a frequency modulation signal, and control the microwave signal source 12 to generate a frequency modulation signal based on the frequency modulation. P1 -F P2 Both of them change frequency quickly;

[0057] Step 4: The modulated high-frequency ODMR signal is mixed into a magnetically sensitive DC signal in the lock-in amplifier 10;

[0058] Step 5, controlling the frequency conversion of the microwave signal source 12 and the on-off of FPGA acquisition and the address area for storing the acquired data according to the timing;

[0059] Step 6: Change the magnetic field size to obtain multiple sets of data, and use a PC to process the output data and obtain the final result.

[0060] In the embodiment of the present invention, in step 4, the fluorescence signal received by the photodetector 9 is converted into a weak electrical signal and connected to an oscilloscope through a data line to observe the ODMR signal generated by the diamond fluorescence signal, and the size of the resonant frequency point corresponding to the half-width of the ODMR curve is observed in this signal.

[0061] In the embodiment of the present invention, in step four, the voltage signal output by the photodetector 9 is input into the phase-locked amplifier 10, and the phase-locked amplifier 10 integrates amplification, mixing, filtering and other circuits to realize signal demodulation and effectively reduce the external noise of the signal.

[0062] In the embodiment of the present invention, the phase-locked amplifier 10 has two output ports, one of which outputs the real part Vi of the demodulated signal, and the other outputs the imaginary part Vj of the demodulated signal, and then the two signals are input into the FPGA module 11 for processing.

[0063] In the embodiment of the present invention, in step three, FPGA controls the microwave signal source 12 to generate a variable frequency microwave signal, specifically including:

[0064] ①FPGA first controls the microwave source to generate two resonant frequencies F P1 and F P2 ;

[0065] ② After EA detects the rising edge signal 0→1, the FPGA clock signal CLK starts to generate a square wave signal (period is 2ms, duty cycle is 50%). When CLK is high, the microwave source is at the resonant frequency F P1 And around F P1 generating a modulation signal;

[0066] ③When CLK is low, it is at the resonant frequency F P2 And around F P2 generating a modulation signal;

[0067] ④DAT wave is used to control FPGA to collect signals. When DAT is low, FPGA does not collect signals. When DAT is high and CLK is high, it means that it is an odd number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the odd number of ms. When DAT is high and CLK is low, it means that it is an even number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the even number of ms.

[0068] ⑤ When FPGA detects the falling edge of the EA signal, FPGA stops generating the clock signal, the microwave source stops working, and the amplitude and phase of the modulation signal are adjusted by the host control system.

[0069] In the embodiment of the present invention, in step 6, the processing of data specifically includes:

[0070] The FPGA is used to collect the two voltage signals V i and V j The data of odd-numbered milliseconds are placed as a group (V i1 , V j1 ), the data of even-numbered milliseconds are placed in a group (V i2 , V j2 ); Then solve the amplitude of the odd-numbered signal V1 and the even-numbered signal V2 respectively, and then use FPGA to perform differential operation on the two groups of signals, and finally obtain a set of voltage data V sensitive to magnetic signals x , and then transmit it to the PC for noise spectrum detection. The PC solves the collected data based on the magnetometer sensitivity analysis algorithm based on signal-to-noise ratio analysis.

[0071] Working principle: After the fluorescence signal generated by the diamond NV color center is converted into a voltage signal through a photodetector, the signal is differentially processed to suppress thermal noise and improve the sensitivity of the magnetic signal.

[0072] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0073] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A high-sensitivity differential magnetic acquisition method for NV color centers based on frequency-agile microwave modulation technology, characterized in that: The differential magnetic acquisition method is applied to the NV color center high-sensitivity differential magnetic acquisition system based on frequency-agile microwave modulation technology. The differential magnetic acquisition system comprises: A magnetic signal calibration module, comprising a magnetic coil (1) for applying a bias magnetic field; An optical system module, comprising a diamond sample (2) containing an NV color center, a laser (5) for emitting laser light, a bandpass filter that allows light of a specific wavelength range to pass through, a dichroic mirror (6) capable of generating a bidirectional light path, and a photodetector (9) for receiving a fluorescence signal, wherein the diamond sample (2) is fixed on a microwave antenna (3), the laser light emitted by the laser (5) irradiates the dichroic mirror (6), the diamond sample (2) is arranged on one side of the dichroic mirror (6), and the photodetector (9) is arranged on the other side of the dichroic mirror (6); A signal processing module, comprising a lock-in amplifier (10) for amplifying the photoelectric signal received by the photoelectric detector (9); A microwave signal generating module, comprising a microwave signal source (12) for generating a microwave signal for a diamond sample (2); A signal control module, comprising an FPGA module (11) for controlling the microwave signal source (12); A data acquisition module, which acquires data through an FPGA module (11); The differential magnetic acquisition method comprises the following steps: Step 1: Build an experimental platform, turn on the microwave signal source (12) and the laser (5), and use the FPGA module (11) to control the microwave signal source (12) to generate a frequency sweep signal; Step 2: Adjust the oscilloscope, observe the ODMR signal on the oscilloscope, and find the microwave frequency F corresponding to the ODMR half-width P1 、F P2 ; Step 3: Use the FPGA module (11) to control the microwave signal source (12) to generate a frequency modulation signal, and control the microwave signal source (12) to generate a frequency modulation signal based on the frequency modulation. P1 -F P2 Both of them change frequency quickly; Step 4: The modulated high-frequency ODMR signal is mixed into a magnetically sensitive DC signal in a lock-in amplifier (10); Step 5, controlling the frequency conversion of the microwave signal source (12) and the on / off of FPGA acquisition and the address area for storing the acquired data according to the timing sequence; Step 6: Change the magnetic field size to obtain multiple sets of data, and use a PC to process the output data and obtain the final result; The lock-in amplifier (10) has two output ports, one of which outputs the real part Vi of the demodulated signal, and the other outputs the imaginary part Vj of the demodulated signal, and then the two signals are input into the FPGA module (11) for processing; In step 6, the processing of data specifically includes: The FPGA is used to collect the two voltage signals V i and V j The data of odd-numbered milliseconds are placed as a group (V i1 , V j1 ), the data of even-numbered milliseconds are placed in a group (V i2 , V j2 ); Then solve the amplitude of the odd-numbered signal V1 and the even-numbered signal V2 respectively, and then use FPGA to perform differential operation on the two groups of signals, and finally obtain a set of voltage data V sensitive to magnetic signals x , and then transmit it to the PC for noise spectrum detection. The PC solves the collected data based on the magnetometer sensitivity analysis algorithm based on signal-to-noise ratio analysis.

2. The differential magnetic acquisition method according to claim 1, characterized in that: An objective lens 1 (4) is arranged between the diamond sample (2) and the dichroic mirror (6), and an objective lens 2 (8) is arranged between the dichroic mirror (6) and the photoelectric detector (9).

3. The differential magnetic acquisition method according to claim 1, characterized in that: A filter (7) is also provided between the dichroic mirror (6) and the photodetector (9) and is close to the side of the dichroic mirror (6).

4. The differential magnetic acquisition method according to claim 3, characterized in that: In step 4, the fluorescent signal received by the photodetector (9) is converted into a weak electrical signal and connected to an oscilloscope via a data line.

5. The differential magnetic acquisition method according to claim 4, characterized in that: In the step 4, the voltage signal output by the photodetector (9) is input into a lock-in amplifier (10), wherein the lock-in amplifier (10) has integrated amplification, mixing and filtering circuits.

6. The differential magnetic acquisition method according to claim 4, characterized in that: In the step 3, the FPGA controls the microwave signal source (12) to generate a variable frequency microwave signal, which specifically includes: ①FPGA first controls the microwave source to generate two resonant frequencies F P1 and F P2 ; ② After EA detects the rising edge signal 0→1, the FPGA clock signal CLK starts to generate a square wave signal with a period of 2ms and a duty cycle of 50%. When CLK is high, the microwave source is at a resonant frequency of F P1 And around F P1 generating a modulation signal; ③When CLK is low, it is at the resonant frequency F P2 And around F P2 generating a modulation signal; ④DAT wave is used to control FPGA to collect signals. When DAT is low, FPGA does not collect signals. When DAT is high and CLK is high, it means that it is an odd number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the odd number of ms. When DAT is high and CLK is low, it means that it is an even number of ms. FPGA stores the data collected by the two acquisition channels in the storage address corresponding to the even number of ms. ⑤ When FPGA detects the falling edge of the EA signal, FPGA stops generating the clock signal, the microwave source stops working, and the amplitude and phase of the modulation signal are adjusted by the host control system.

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