Quantum magnetic sensor and method of magnetic measurement

Abstract

The application provides a single-channel mixing temperature compensation quantum magnetic sensor and a magnetic measurement method, which significantly improves the precision, dynamic range and environmental adaptability of magnetic field measurement through innovative architecture design and algorithm optimization. The core is to use the nonlinear mixing characteristics of the local oscillator source and the direct digital frequency synthesizer to generate phase-inverted double-sideband microwave signals, which synchronously excite the ms=0 to ms=-1 resonance and ms=0 to ms=+1 resonance of the NV color center in a single channel. Through differential demodulation of the fluorescence signal and closed-loop feedback control, the system can eliminate common-mode temperature drift in real time and effectively widen the dynamic range of diamond spin color center magnetic measurement. Therefore, the application overcomes the hardware redundancy bottleneck in the prior art and provides a new technical path for miniaturization and engineering of high-precision magnetic measurement technology.

Description

Technical Field

[0001] This invention relates to the field of quantum precision measurement technology, and in particular to a quantum magnetic sensor and a magnetic measurement method. Background Technology

[0002] Breakthroughs in quantum precision measurement technology are propelling magnetic field detection from traditional classical methods to ultra-sensitive detection based on quantum effects. Diamond nitrogen-vacancy (NV) centers, as solid-state quantum systems, have become the core carrier of next-generation quantum magnetic sensors due to their unique advantages such as room-temperature stability, optically addressable spin states, and millisecond-level coherence time. The ground-state electron spin (S=1) of NV centers splits into ms=0 and ms=±1 energy levels under zero magnetic field conditions due to the crystal field. The linear response of its Zeeman effect to external magnetic fields (~28 GHz / T) forms the physical basis of magnetic measurement. Optically probed magnetic resonance (ODMR) technology allows for the manipulation of spin states using microwave fields and the reading of fluorescence intensity changes, thereby achieving highly sensitive magnetic field detection. This demonstrates disruptive potential in fields such as biomedical imaging, geomagnetic navigation, and superconducting device detection.

[0003] However, traditional NV magnetic sensing technology faces two major challenges: temperature drift interference and microwave drive efficiency bottlenecks. The zero-field splitting frequency of the NV color center (D≈2.87GHz) has a significant temperature dependence (-74kHz / K), leading to coupling of the magnetic field measurement signal with temperature noise. To simultaneously excite the ms=0 to ms=-1 resonance and the ms=0 to ms=+1 resonance to achieve differential temperature drift suppression, existing solutions generally employ dual-channel independent microwave drive, demodulating fluorescence independently by applying different frequency modulations to the two channels; or they alternately drive using time-division multiplexing technology. However, phase mismatch between the two channels introduces incoherent noise into the differential signal, and the hardware size and power consumption increase exponentially.

[0004] On the other hand, to achieve rapid frequency transitions, a high-frequency local oscillator is often used in conjunction with a fast-moving source for single-sideband modulation. For example, a single-sideband generation method using an IQ mixer can suppress mirror sidebands using a 90° phase shifter and a balanced mixer. However, this method requires precise control of the phase relationship between the local oscillator and the fast-moving signal, and the sideband suppression ratio is limited by the mixer's nonlinearity. If a bandpass filter is used after mixing to filter out non-target sidebands, it will result in microwave power loss of more than 50%.

[0005] Therefore, how to propose a magnetic measurement device and method for realizing dual-frequency driving of NV color centers through single-channel mixing has become one of the problems that urgently need to be solved by those skilled in the art.

[0006] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a quantum magnetic sensor and a magnetic measurement method to solve the problems of temperature drift interference, poor magnetic measurement sensitivity, dual-channel redundancy, and phase mismatch in the existing NV magnetic sensor.

[0008] To achieve the above and other related objectives, the present invention provides a quantum magnetic sensor, the quantum magnetic sensor comprising at least:

[0009] Microwave mixing and driving module, microwave antenna, laser module, quantum spin color center diamond, optical detection module, and phase-locked demodulation and signal processing device;

[0010] The microwave mixing and driving module generates phase-complementary double-sideband microwaves through single-channel mixing.

[0011] The microwave antenna radiates the dual-frequency microwaves onto the quantum spin color center diamond;

[0012] The laser module is used to generate an excitation light signal, which is used to polarize the NV center spin state of the quantum spin center diamond.

[0013] The quantum spin color center diamond generates a fluorescence signal when excited by the excitation light signal;

[0014] The optical detection module detects the fluorescence signal and converts the optical signal into an electrical signal;

[0015] The phase-locked demodulation and signal processing device is connected to the output of the optical detection module. It extracts the sensitive signal of the magnetic field under test by demodulating the output signal of the optical detection module with a reference frequency and suppresses temperature drift noise. It updates the frequency control word based on the offset of the resonant frequency and feeds it back to the microwave mixer and drive module to form a closed-loop frequency tuning.

[0016] Optionally, the microwave mixer and drive module includes a local oscillator, a direct digital frequency synthesizer, and a double-balanced mixer;

[0017] The local oscillator source generates a local oscillator signal;

[0018] The direct digital frequency synthesizer receives the frequency control word and uses it to generate agile signals;

[0019] The dual-balanced mixer is connected to the output of the local oscillator and the direct digital frequency synthesizer, and is used to mix the local oscillator signal with the output signal of the direct digital frequency synthesizer to generate a spectrally symmetrical upper sideband signal and lower sideband signal.

[0020] Optionally, the quantum magnetic sensor further includes a power amplifier connected to the output of the double-balanced mixer to amplify the power of the output signal of the double-balanced mixer.

[0021] Optionally, the microwave antenna is implemented using a microwave resonator.

[0022] Optionally, the laser module includes a laser and a dichroic mirror;

[0023] The laser generates a laser signal;

[0024] The dichroic mirror is disposed at the output end of the laser and is used to divide the laser signal into an excitation light signal and a reference light signal; the reference light signal is provided to the optical detection module to suppress optical noise.

[0025] Optionally, the phase-locked demodulation and signal processing device includes an analog-to-digital converter, a frequency control module, a frequency multiplier, a filter, a frequency offset calculation module, a modulation module, and a frequency adder;

[0026] The analog-to-digital converter is connected to the output terminal of the optical detection module and converts the output signal of the optical detection module into a digital signal.

[0027] The frequency control module generates a reference signal to implement frequency sweep mode and frequency hopping mode;

[0028] The frequency multiplier performs coherent mixing of the digital signal and the reference signal;

[0029] The filter is connected to the output of the frequency multiplier and is used to extract the low-frequency signal from the output signal of the frequency multiplier.

[0030] The frequency offset calculation module is connected to the output of the filter and calculates the offset of the resonant frequency based on the low-frequency signal.

[0031] The modulation module generates a modulation signal for the agile signal based on the reference signal;

[0032] The frequency adder is connected to the output of the frequency offset calculation module and the modulation module, and updates the frequency control word based on the offset.

[0033] Alternatively, the microwave mixing and driving module and the phase-locked demodulation and signal processing device are integrated on the same PCB board, and the quantum spin color center diamond, the laser module, the optical detection module and the microwave antenna are integrated to form a diamond quantum probe.

[0034] To achieve the above and other related objectives, the present invention also provides a magnetic measurement method based on the aforementioned quantum magnetic sensor, wherein the magnetic measurement method includes at least:

[0035] 1) Provide excitation light to initialize the quantum spin color center diamond; set the initial frequency offset based on the frequency control word, and obtain a phase-complementary double-sideband microwave by mixing with the local oscillator signal, wherein the double-sideband microwave matches the resonant frequency corresponding to the current magnetic field;

[0036] 2) Acquire fluorescence signals and demodulate the fluorescence signals to obtain demodulated signals;

[0037] 3) When the magnetic field changes, the offset of the resonant frequency is calculated based on the predicted demodulation slope, and the frequency control word is updated so that the demodulated signal returns to the initial value, tracks the change of the magnetic field, and then reconstructs the magnetic field strength.

[0038] Optionally, the initial frequency offset satisfies:

[0039] f D =γB;

[0040] Among them, f D γ is the initial frequency deviation, B is the current magnetic field, and γ is the electron gyrometry.

[0041] Optionally, the offset of the resonant frequency satisfies:

[0042] Δf=Δ(V - +V + ) / k;

[0043] Where Δf is the offset, (V - +V + ) represents the demodulated signal, and k represents the demodulation slope.

[0044] As described above, the quantum magnetic sensor and magnetic measurement method of the present invention have the following beneficial effects:

[0045] 1. The quantum magnetic sensor and magnetic measurement method of the present invention utilize the nonlinear characteristics of a mixer to naturally generate a phase-inverted double-sideband signal, synchronously exciting the m of the NV color center. s =0 to m s =-1 resonance and m s =0 to m s =+1 resonance eliminates the need for bandpass filters or IQ phase shifting circuits in traditional solutions.

[0046] 2. The quantum magnetic sensor and magnetic measurement method of the present invention eliminates the filtering and phase control modules, and directly utilizes the total power of the double-sideband to drive the double resonance method, thereby improving the effective magnetic measurement sensitivity by 30%.

[0047] 3. The quantum magnetic sensor and magnetic measurement method of the present invention naturally generate upper and lower sidebands with a 180° phase difference during the nonlinear mixing process, which accurately matches the Zeeman frequency shift of the target magnetic field and can achieve differential temperature drift suppression without additional hardware.

[0048] 4. The quantum magnetic sensor and magnetic measurement method of the present invention can realize board-level integrated measurement, has wide applicability, and is more conducive to promotion and use. Attached Figure Description

[0049] Figure 1 The diagram shown is a structural schematic of the quantum magnetic sensor of the present invention.

[0050] Figure 2 The diagram shown is a schematic of a portable quantum magnetic sensor with board-level integration according to the present invention.

[0051] Figure 3 The diagram shown illustrates the spectrum generation principle of the microwave mixing and driving module of this invention.

[0052] Figure 4 The image shows the frequency spectrum of the phase-locked demodulation of this invention.

[0053] Figure 5 The figure shows the magnetic field variation curve under dual-frequency microwave drive according to the present invention.

[0054] Figure 6 The figure shows the temperature change curve under dual-frequency microwave drive according to the present invention.

[0055] Figure 7 The flowchart shown is a flowchart of the dynamic frequency tracking algorithm of the present invention.

[0056] Figure 8 The figure shows the demodulation curve of magnetic field changes under the dynamic frequency tracking algorithm of this invention.

[0057] Component designation explanation

[0058] 1. Quantum magnetic sensor

[0059] 11 Microwave Mixer and Driver Module

[0060] 111 Local Oscillator

[0061] 112 Direct Digital Frequency Synthesizer

[0062] 113 Double-balanced mixer

[0063] 12 Microwave Antenna

[0064] 13 Laser Module

[0065] 131 laser

[0066] 132 Dichroic Mirror

[0067] 14 Quantum Spin Color Center Diamonds

[0068] 15 Optical Inspection Module

[0069] 16. Phase-locked demodulation and signal processing device

[0070] 161 Analog-to-Digital Converter

[0071] 162 Frequency Control Module

[0072] 163 Frequency Multiplier

[0073] 164 Filter

[0074] 165 Frequency Offset Calculation Module

[0075] 166 modulation module

[0076] 167 Frequency Adder

[0077] 168 Local Oscillator Frequency Control Module

[0078] 17 Power Amplifier

[0079] 1a Board-level integrated single-channel dual-frequency drive module

[0080] 1b Diamond Quantum Probe Detailed Implementation

[0081] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0082] Please see Figures 1 to 8 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0083] like Figure 1As shown, the present invention provides a quantum magnetic sensor 1, which includes:

[0084] The system includes a microwave mixing and driving module 11, a microwave antenna 12, a laser module 13, a quantum spin color center diamond 14, an optical detection module 15, and a phase-locked demodulation and signal processing device 16.

[0085] like Figure 1 As shown, the microwave mixer and drive module 11 generates phase-complementary double-sideband microwaves through single-channel mixing.

[0086] Specifically, the microwave mixing and driving module 11 includes a local oscillator source 111, a direct digital synthesizer (DDS) 112, and a double-balanced mixer 113. The local oscillator source 111 generates a local oscillator signal LO. In this embodiment, the frequency f of the local oscillator signal is... LO Locking NV color center zero field splitting D gs ≈2.87GHz; as an example, the local oscillator 111 is implemented using a PLL circuit. The direct digital frequency synthesizer 112 receives a frequency control word to generate a fast-moving signal DDS, with a frequency set from 1kHz to 400MHz. A double-balanced mixer 113 is connected to the outputs of the local oscillator 111 and the direct digital frequency synthesizer 112, and is used to mix the local oscillator signal LO with the output signal DDS of the direct digital frequency synthesizer to generate a spectrally symmetrical upper sideband signal and a lower sideband signal (double-sided microwave), wherein the two sideband signals are 180° out of phase.

[0087] As another implementation of the present invention, such as Figure 2 As shown, the quantum magnetic sensor 1 also includes a power amplifier 17, which is connected to the output of the double-balanced mixer 113 and is used to amplify the power of the output signal of the double-balanced mixer 113.

[0088] like Figure 1 As shown, microwave antenna 12 radiates dual-frequency microwaves to quantum spin color center diamond 14.

[0089] Specifically, the microwave antenna 12 is used to apply a uniform microwave field to the NV color center. In this example, the microwave antenna 12 is implemented using a microwave resonator, thereby increasing the intensity of the generated microwave field. In practical applications, any form of microwave antenna is applicable to this invention.

[0090] like Figure 1 As shown, the laser module 13 is used to generate an excitation light signal, which is used to polarize the NV center spin state of the quantum spin center diamond 14.

[0091] Specifically, as an example, the laser module 13 includes a laser 131. The laser signal with a preset wavelength (532 nm in this example, but can be set as needed in actual use) provided by the laser 131 is applied as excitation light to the quantum spin center diamond 14 to polarize the spin state of the NV center. As another example, the laser module 13 also includes a dichroic mirror 132, which is disposed at the output end of the laser 131 to split the laser signal into an excitation light signal and a reference light signal; wherein the reference light signal is provided to the optical detection module 15 as a reference optical path.

[0092] like Figure 1 As shown, quantum spin color center diamond 14 generates a fluorescence signal when excited by an excitation light signal.

[0093] Specifically, quantum spin color center diamond 14 contains a nitrogen-vacancy color center ensemble whose spin state is modulated by a microwave field, and can be excited by laser to generate fluorescence signals.

[0094] like Figure 1 As shown, the optical detection module 15 detects the fluorescence signal and converts the optical signal into an electrical signal.

[0095] Specifically, in this embodiment, the optical detection module 15 includes any type of photodetector, including but not limited to photodetectors for spatial light detection (capable of large-area fluorescence collection). As one implementation of the invention, the optical detection module 15 also includes a filter, which is disposed on the optical signal input side of the photodetector to filter out laser light unrelated to fluorescence; the filtered fluorescence then enters the photodetector. As another implementation of the invention, the fluorescence signal enters the photodetector through a high numerical aperture objective lens to improve fluorescence collection efficiency; the fluorescence signal can also enter the photodetector through a fiber optic circulator to simultaneously achieve laser incident light and fluorescence collection. Of course, the filter can also be disposed before the high numerical aperture objective lens or the fiber optic circulator, which will not be elaborated further here.

[0096] In addition, when the optical detection module 15 receives the reference light signal, it processes the detected fluorescence signal based on the reference light signal to suppress optical noise.

[0097] like Figure 1 As shown, the phase-locked demodulation and signal processing device 16 is connected to the output of the optical detection module 15. It extracts the magnetic field sensitive signal under test and suppresses temperature drift noise by demodulating the output signal of the optical detection module 15 with the reference frequency. It updates the frequency control word based on the offset of the resonant frequency and feeds it back to the microwave mixer and drive module 11 to form a closed-loop frequency tuning.

[0098] Specifically, such as Figure 2As shown, the phase-locked demodulation and signal processing device 16 includes an analog-to-digital converter 161, a frequency control module 162, a frequency multiplier 163, a filter 164, a frequency offset calculation module 165, a modulation module 166, and a frequency adder 167. The analog-to-digital converter 161 is connected to the output of the optical detection module 15, converting the analog signal output by the optical detection module 15 into a digital signal. The frequency control module 162 generates a reference signal; in this embodiment, the reference signal is a 32-bit DSS frequency control word. The frequency multiplier 163 coherently mixes the digital signal output by the analog-to-digital converter 161 and the reference signal output by the frequency control module 162. The filter 164 is connected to the output of the frequency multiplier 163 and is used to extract low-frequency signals from the output signal of the frequency multiplier 163; in this example, the filter 164 is implemented using a cascaded FIR (Finite Impulse Response) filter. The frequency offset calculation module 165 is connected to the output of the filter 164 and has real-time calculation capabilities. It calculates the offset Δf of the resonant frequency based on the low-frequency signal, satisfying Δf = Δ(V - +V + The system also includes a dynamic frequency tuning algorithm, which controls the DDS frequency to follow the resonant frequency change to achieve frequency sweep and frequency hopping modes. Frequency sweep mode ensures precise frequency matching of the dual-frequency drive signal to the resonant frequency, while frequency hopping mode improves the dynamic range of magnetic field measurement. The modulation module 166 generates a modulation signal for the agile signal based on the reference signal output by the frequency control module 162. The frequency adder 167 is connected to the output of the frequency offset calculation module 165 and the modulation module 166, based on the agile frequency offset Δf. D Output the updated frequency control word to achieve closed-loop large dynamic range magnetic field measurement.

[0099] As another implementation of the present invention, the phase-locked demodulation and signal processing device 16 further includes a local oscillator frequency control module 168, which is used to control the local oscillator source 111 to output the local oscillator frequency f in the initial stage. LO =Frequency around 2.87GHz.

[0100] like Figure 2 As shown, as an example, the microwave mixing and driving module 11 and the phase-locked demodulation and signal processing device 16 of the present invention are configured as a board-level integrated single-channel dual-frequency driving module 1a, integrated on the same PCB board. The quantum spin color center diamond 14, the laser module 13, the optical detection module 14, and the microwave antenna 12 are integrated to form a diamond quantum probe 1b. Furthermore, each part can be integrated through microfabrication processes (e.g., forming a coplanar waveguide microwave antenna on the diamond surface by plasma etching to achieve the integration of the diamond and the microwave antenna). The cooperation between the single-channel dual-frequency driving module 1a and the diamond quantum probe 1b enables mobile and portable magnetic measurement.

[0101] Specifically, in this embodiment, the frequency control module 162, frequency multiplier 163, filter 164, frequency offset calculation module 165, modulation module 166, frequency adder 167, and local oscillator frequency control module 168 are implemented using an FPGA main control module. Through the FPGA all-digital control architecture and microwave integrated design, the board-level integration of the dual-frequency drive module is realized, and real-time tracking of the resonant frequency can be achieved, expanding the measurement range.

[0102] In this invention, the quantum spin color center in a diamond undergoes Zeeman splitting under the influence of an external magnetic field, causing the spin energy level to be modulated by the magnetic field. This can be achieved using a microwave field. s =0 to m s =-1 resonance and m s =0 to m s = +1 resonance, its resonant frequency satisfies:

[0103] f ± =D gs ±γB (0.1)

[0104] Among them, D ga It is a zero-field split, approximately 2.87 GHz at room temperature, γ = 28 nT / Hz is the electron gyrometry ratio, and B is the magnitude of the projection of the external magnetic field onto the quantum spin color center. When B = 0, m s =±1 energy level is in a degenerate state; when the external magnetic field changes, m s =0 jump to m s The resonance frequency of the ±1 energy level splits into f + =D gs +γB and f-=D gs -γB. When the applied microwave field frequency is equal to the resonance frequency, it results in a state at m s The spin-dependent decrease in fluorescence intensity of the NV color center at the ±1 energy level allows for the detection of changes in the external magnetic field by detecting the frequency corresponding to the change in fluorescence intensity.

[0105] like Figure 3 As shown, the signal of the direct digital frequency synthesizer 112 can be described as:

[0106] f DDS =f D +f dev cos(2πf mod t) (0.2)

[0107] Among them, f dev f is the modulation depth of the modulated signal. mod f is the modulation frequency of the modulated signal. DDSf is the modulated agile frequency output by the direct digital frequency synthesizer 112. D This is the initial frequency offset. When the local oscillator 111 and the direct digital frequency synthesizer 112 are nonlinearly superimposed through the double-balanced mixer 113, a spectrally symmetrical upper sideband (f) will be generated. LO +f DDS ) and the lower sideband (f LO -f DDS The modulation signals of these two sidebands have a 180° phase difference, satisfying:

[0108] f mix =f LO ±f DDS =(f LO +f D +f dev cos(2πf mod t))+(f LO -f D -f dev cos(2πf mod t)) (0.3)

[0109] For a fluorescence signal S with a resonance frequency near f0, it can be described by a Lorentz curve, satisfying the following:

[0110]

[0111] Where S0 is the fluorescence intensity at the non-resonance frequency, and C CW Δv is the fluorescence contrast of the Lorentz curve, and Δv is the resonance linewidth of the Lorentz curve.

[0112] When f LO =(f-+f + ) / 2, f D =(f + When -f-) / 2, it can make f LO and f D The two sidebands obtained from the mixing are exactly f ± Frequency, taking the lower sideband as an example, fluorescence signals at frequencies near f- can be described as:

[0113]

[0114] Perform a Taylor expansion of the fluorescence signal near the resonance point f = f- and retain the first-order terms:

[0115]

[0116] Typically, f is set. dev << Δv, and by neglecting the DC term through AC coupling, the formula can be simplified to:

[0117]

[0118] This indicates that the fluorescence signal contains a modulation component f. mod Therefore, a reference signal of the same frequency needs to be introduced for demodulation:

[0119] S ref =cos(2πf) mod t) (0.8)

[0120] Multiply the fluorescence signal by the reference signal:

[0121]

[0122] in, This represents the phase difference between the DC signal and the fluorescence modulation signal components. It can be seen that the multiplied signal contains a second harmonic component of the modulation frequency, cos(4πf). mod t) and DC component At this point, low-pass filtering can preserve the DC signal R1. For the upper sideband near f-, since the modulation signals of the upper and lower sidebands are mixed by a mixer to ensure a 180° phase difference, the resulting DC signal... Therefore, the resonance point f of the single-channel mixer double-sideband at the NV color center can be plotted. ± Nearby demodulated signals, such as Figure 4 As shown.

[0123] like Figure 5 As shown, when the magnetic field increases, f- shifts to lower frequencies, while f+ shifts to higher frequencies. The resulting demodulated signal is V. - +V + =2V - This indicates that the signal strength has been increased by 2 times. For example... Figure 6 As shown, when the temperature increases, f- shifts to lower frequencies, and the resulting demodulated signal is V. - +V + =V - +(V - ) = 0, indicating that the interference introduced by temperature is eliminated. Therefore, this method can achieve temperature drift suppression magnetic field measurement with only a single channel.

[0124] The present invention also provides a magnetic measurement method, which in this embodiment is implemented based on the quantum magnetic sensor 1 of the present invention. The magnetic measurement method includes:

[0125] 1) Provide excitation light to initialize the quantum spin color center diamond; set the initial frequency offset based on the frequency control word, and obtain a phase-complementary double-sideband microwave by mixing with the local oscillator signal, wherein the double-sideband microwave matches the resonant frequency corresponding to the current magnetic field.

[0126] Specifically, initial locking: laser initialization of the NV color center spin state to m s =0; Sets the initial frequency offset f of the direct digital frequency synthesizer 112. D =γB, making the microwave sideband f LO ±f DDS Matching the resonant frequency f corresponding to the current magnetic field B ± Synchronous drive m s =0 to m s =-1 resonance and m s =0 to m s =+1 resonance.

[0127] 2) Acquire fluorescence signals, demodulate the fluorescence signals, and obtain demodulated signals.

[0128] Specifically, signal monitoring: real-time acquisition of fluorescence demodulation to obtain signal S = (V - +V + ).

[0129] 3) When the magnetic field changes, the offset Δf of the resonant frequency is calculated based on the predicted demodulation slope, and the frequency control word is updated so that the demodulated signal returns to the initial value, tracks the change of the magnetic field, and then reconstructs the magnetic field strength.

[0130] Specifically, frequency offset calculation: when the change in magnetic field ΔB causes the demodulated signal S to deviate from zero, the required frequency offset correction is calculated based on the pre-measured demodulation slope k.

[0131] Frequency adjustment: Controls the output frequency of the direct digital frequency synthesizer 112 to be updated to f. D –Δf, then feedback adjustment Δf to zero, so that the microwave sidebands are realigned with f. ± =D gs The magnetic field changes are tracked using ±γ(B+ΔB), the Δf value corresponding to the current magnetic field is locked, and the magnetic field strength is reconstructed based on Δf=±γB, thereby realizing magnetic field measurement with a large dynamic range.

[0132] like Figure 8 As shown, when the magnetic field changes, the demodulated signal (V) - +V + The frequency will change, and the shift in resonant frequency Δf = Δ(V) will be calculated by the change in the demodulated signal. - +V + Then, control the frequency of the agile source to change synchronously by Δf. D This makes the microwave frequency f LO ±f DDS Rematching the resonant frequency f ± At this point, the demodulated signal returns to zero; by adjusting the frequency of the agile source DDS in real time, continuous and wide-range detection of the magnetic field can be achieved.

[0133] Specifically, in this embodiment, the local oscillator frequency control module 168 inside the FPGA main control module controls the local oscillator source 111 to generate a high-frequency local oscillator frequency f. LO Frequency control module 162 generates the initial frequency offset f. D The frequency control word, along with the modulation signal generated by the modulation module 166, controls the direct digital frequency synthesizer 112 to generate agile frequency f. DDS After being mixed by the double-balanced mixer 113, the upper and lower sideband microwave signals with matching f± are generated. After being amplified by the power amplifier 17, they are transmitted to the diamond quantum probe 1b. The analog-to-digital converter 161 converts the fluorescence signal of the diamond quantum probe 1b into an electrical signal, which is then transmitted to the FPGA main control module for demodulation. The fluorescence signal is multiplied by the frequency multiplier 163 and the reference signal, and then low-pass filtered by the filter 164 to obtain the demodulated signal. Subsequently, the frequency offset calculation module 165 calculates the frequency offset value of the direct digital frequency synthesizer 112, and the frequency adder 168 completes the regulation of the frequency control word of the direct digital frequency synthesizer 112.

[0134] In summary, this invention provides a single-channel mixing-based quantum magnetic sensor and magnetic measurement method for temperature compensation. Through innovative architecture design and algorithmic optimization, it significantly improves the accuracy, dynamic range, and environmental adaptability of magnetic field measurement. Its core lies in utilizing the nonlinear mixing characteristics of a local oscillator and a direct digital frequency synthesizer (DDS) to generate a phase-inverted double-sideband microwave signal (f... LO ±f DDS This invention simultaneously excites NV color centers from ms=0 to ms=-1 and from ms=0 to ms=+1 resonances within a single channel. Through differential demodulation of the fluorescence signal and closed-loop feedback control, the system can eliminate common-mode temperature drift in real time and effectively broaden the dynamic range of magnetic measurements of diamond spin color centers. Therefore, this invention effectively overcomes the hardware redundancy bottleneck in existing technologies and provides a new technical path for the miniaturization and engineering of high-precision magnetic measurement technology. Thus, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0135] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A quantum magnetic sensor, characterized in that, The quantum magnetic sensor includes at least: Microwave mixing and driving module, microwave antenna, laser module, quantum spin color center diamond, optical detection module, and phase-locked demodulation and signal processing device; The microwave mixing and driving module generates phase-complementary double-sideband microwaves through single-channel mixing. The microwave antenna radiates the dual-frequency microwaves onto the quantum spin color center diamond; The laser module is used to generate an excitation light signal, which is used to polarize the NV center spin state of the quantum spin center diamond. The quantum spin color center diamond generates a fluorescence signal when excited by the excitation light signal; The optical detection module detects the fluorescence signal and converts the optical signal into an electrical signal; The phase-locked demodulation and signal processing device is connected to the output of the optical detection module. It extracts the sensitive signal of the magnetic field under test by demodulating the output signal of the optical detection module with a reference frequency and suppresses temperature drift noise. It updates the frequency control word based on the offset of the resonant frequency and feeds it back to the microwave mixer and drive module to form a closed-loop frequency tuning.

2. The quantum magnetic sensor according to claim 1, characterized in that: The microwave mixing and driving module includes a local oscillator, a direct digital frequency synthesizer, and a double-balanced mixer. The local oscillator source generates a local oscillator signal; The direct digital frequency synthesizer receives the frequency control word and uses it to generate agile signals; The dual-balanced mixer is connected to the output of the local oscillator and the direct digital frequency synthesizer, and is used to mix the local oscillator signal with the output signal of the direct digital frequency synthesizer to generate a spectrally symmetrical upper sideband signal and lower sideband signal.

3. The quantum magnetic sensor according to claim 2, characterized in that: The quantum magnetic sensor also includes a power amplifier connected to the output of the double-balanced mixer to amplify the power of the output signal of the double-balanced mixer.

4. The quantum magnetic sensor according to claim 1, characterized in that: The microwave antenna is implemented using a microwave resonator.

5. The quantum magnetic sensor according to claim 1, characterized in that: The laser module includes a laser and a dichroic mirror; The laser generates a laser signal; The dichroic mirror is disposed at the output end of the laser and is used to divide the laser signal into an excitation light signal and a reference light signal; the reference light signal is provided to the optical detection module to suppress optical noise.

6. The quantum magnetic sensor according to claim 1, characterized in that: The phase-locked demodulation and signal processing device includes an analog-to-digital converter, a frequency control module, a frequency multiplier, a filter, a frequency offset calculation module, a modulation module, and a frequency adder. The analog-to-digital converter is connected to the output terminal of the optical detection module and converts the output signal of the optical detection module into a digital signal. The frequency control module generates a reference signal to implement frequency sweep mode and frequency hopping mode; The frequency multiplier performs coherent mixing of the digital signal and the reference signal; The filter is connected to the output of the frequency multiplier and is used to extract the low-frequency signal from the output signal of the frequency multiplier. The frequency offset calculation module is connected to the output of the filter and calculates the offset of the resonant frequency based on the low-frequency signal. The modulation module generates a modulation signal for the agile signal based on the reference signal; The frequency adder is connected to the output of the frequency offset calculation module and the modulation module, and updates the frequency control word based on the offset.

7. The quantum magnetic sensor according to any one of claims 1 to 6, characterized in that: The microwave mixing and driving module and the phase-locked demodulation and signal processing device are integrated on the same PCB board. The quantum spin color center diamond, the laser module, the optical detection module and the microwave antenna are integrated to form a diamond quantum probe.

8. A magnetic measurement method, implemented based on a quantum magnetic sensor as described in any one of claims 1-7, characterized in that, The magnetic measurement method includes at least: 1) Provide excitation light to initialize the quantum spin color center diamond; set the initial frequency offset based on the frequency control word, and obtain a phase-complementary double-sideband microwave by mixing with the local oscillator signal, wherein the double-sideband microwave matches the resonant frequency corresponding to the current magnetic field; 2) Acquire fluorescence signals and demodulate the fluorescence signals to obtain demodulated signals; 3) When the magnetic field changes, the offset of the resonant frequency is calculated based on the predicted demodulation slope, and the frequency control word is updated so that the demodulated signal returns to the initial value, tracks the change of the magnetic field, and then reconstructs the magnetic field strength.

9. The magnetic measurement method according to claim 8, characterized in that: The initial frequency offset satisfies: f D =γB; Among them, f D γ is the initial frequency deviation, B is the current magnetic field, and γ is the electron gyrometry.

10. The magnetic measurement method according to claim 8, characterized in that: The offset of the resonant frequency satisfies: Δf=Δ(V - +V + ) / k; Where Δf is the offset, (V - +V + ) represents the demodulated signal, and k represents the demodulation slope.

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