Method and system for measuring NV color center magnetic field and current

Abstract

The invention relates to the technical field of NV color centers, and discloses an NV color center magnetic field and current measurement method and system. The method comprises the following steps: performing decomposition and noise reduction on the two to generate target three-dimensional data, and constructing a joint response equation by combining the resonant frequency offset and the fluorescence intensity change value of the target three-dimensional data; and finally, decoupling the equation to obtain a global magnetic field estimation value, and determining a current density distribution diagram according to the value and the vacuum magnetic conductivity. According to the method, the initial signal quality is improved through the quantum coherence enhanced pulse sequence, the influence of interference such as environmental thermal noise on the magnetic field signal is effectively weakened through decomposition noise reduction and joint response equation decoupling, and the magnetic field characteristics are accurately extracted, so that high-precision data support is provided for subsequent magnetic field analysis and current density distribution determination. The technical problem that in the prior art, interference such as environmental thermal noise exists generally, so that initially-collected magnetic field signals are mixed with a large amount of noise, and follow-up magnetic field and current analysis is seriously affected is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of NV color centers, and particularly relates to an NV color center magnetic field and current measurement method and system. BACKGROUND

[0002] In the field of precise measurement of magnetic field and current, high-precision magnetic field and current information acquisition is of great significance to many scientific research and engineering scenarios. For example, in the manufacture of precision instruments, accurate magnetic field data can ensure the stable performance of the instruments; in the study of biomagnetism, reliable current distribution information can help to further explore electromagnetic phenomena in living organisms. These high-precision data are the key support for promoting technological development and breakthroughs in related fields.

[0003] Currently, the optical detection magnetic resonance (ODMR) technology based on NV color centers is an important means to realize magnetic field detection. This technology uses the spin characteristics of NV color centers to reflect the magnetic field situation by detecting the change of fluorescence intensity. However, in actual measurement, environmental thermal noise and other disturbances are ubiquitous, so that the initially collected magnetic field signal is mixed with a large amount of noise, which seriously affects the subsequent analysis of magnetic field and current. SUMMARY

[0004] The present application provides an NV color center magnetic field and current measurement method and system, which solves the technical problem that in the prior art, environmental thermal noise and other disturbances are ubiquitous, so that the initially collected magnetic field signal is mixed with a large amount of noise, which seriously affects the subsequent analysis of magnetic field and current.

[0005] The first aspect of the present application provides an NV color center magnetic field and current measurement method, comprising:

[0006] An initial magnetic field signal containing environmental thermal noise is obtained, and a quantum coherence enhancement pulse sequence is constructed using the initial magnetic field signal containing environmental thermal noise;

[0007] The spin state of the NV color center is regulated by the quantum coherence enhancement pulse sequence, and the optical detection magnetic resonance spectrum and the time domain fluorescence intensity are determined;

[0008] The optical detection magnetic resonance spectrum and the time domain fluorescence intensity are decomposed and denoised to generate target three-dimensional data;

[0009] The resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time domain fluorescence intensity are combined to construct a joint response equation;

[0010] The joint response equation is decoupled to generate a global magnetic field estimate, and the current density distribution map is determined according to the global magnetic field estimate and the preset vacuum permeability.

[0011] Optionally, the spin state of the NV center is regulated by the quantum coherence enhancement pulse sequence, and the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity are determined, comprising:

[0012] The spin state of the NV center is regulated by the quantum coherence enhancement pulse sequence, and when the spin state of the NV center is in the ground state, the NV center is excited by a laser to generate an initial fluorescence signal;

[0013] Within a preset pulse interval time, a plurality of microwave pulses of different frequencies are applied to the NV center to obtain target microwave frequency points;

[0014] Within the regulation period of each target microwave frequency point, an optical detection magnetic resonance spectrum is collected;

[0015] The initial fluorescence signal of each spatial pixel point within the regulation period of the target microwave frequency point is integrated to obtain the total fluorescence integral intensity of each spatial pixel point;

[0016] The sum of the total fluorescence integral intensities of all spatial pixel points is calculated to generate a time-domain fluorescence intensity.

[0017] Optionally, it further comprises:

[0018] When the spin state of the NV center is regulated by the quantum coherence enhancement pulse sequence, the preset pulse interval time, the pulse repetition number and the intrinsic decoherence time are obtained;

[0019] According to the preset pulse interval time, the pulse repetition number and the intrinsic decoherence time, the effective decoherence time of the NV center is determined;

[0020] According to the effective decoherence time of the NV center, the initial acquisition sensitivity of the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity is adjusted to generate a target acquisition sensitivity.

[0021] Optionally, it further comprises:

[0022] The measurement time, the electron gyromagnetic ratio, the temperature disturbance value, the angle between the magnetic field corresponding to the initial magnetic field signal containing environmental thermal noise and the axial direction of the NV center are obtained;

[0023] The effective decoherence time, the initial magnetic field signal containing environmental thermal noise, the measurement time, the angle, a preset Gaussian white noise, the electron gyromagnetic ratio and the initial fluorescence intensity corresponding to the initial fluorescence signal are used to calculate a fluorescence response function;

[0024] According to the initial resonance frequency offset corresponding to the time-domain fluorescence intensity, the temperature disturbance value and the temperature offset rate of a preset zero-field splitting coefficient, a thermal drift compensation amount is determined.

[0025] Optionally, the light-probing magnetic resonance spectrum and the time-domain fluorescence intensity are decomposed and denoised to generate target three-dimensional data, including:

[0026] The light-probing magnetic resonance spectrum and the time-domain fluorescence intensity are processed in a higher dimension to obtain initial three-dimensional data;

[0027] The initial three-dimensional data are subjected to Tucker decomposition processing and alternating least squares optimization processing to generate denoised target three-dimensional data and a resonance frequency matrix of each spatial point and crystal direction.

[0028] Optionally, the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time-domain fluorescence intensity are combined to construct a joint response equation, including:

[0029] The first resonance frequency of each spatial point and crystal direction is extracted from the target three-dimensional data using a fast Fourier transform method;

[0030] Based on a reference value of a preset zero-field splitting coefficient, a temperature offset rate of a preset zero-field splitting coefficient, and a temperature drift suppression rate, a temperature drift correction amount of the zero-field splitting coefficient is determined;

[0031] The difference between the first resonance frequency and the reference value of the preset zero-field splitting coefficient is calculated to generate a resonance frequency offset;

[0032] According to the current measured fluorescence integral intensity corresponding to the time-domain fluorescence intensity and the baseline intensity without disturbance, a fluorescence intensity change value is determined;

[0033] The resonance frequency offset, the fluorescence intensity change value, the electronic gyromagnetic ratio, the preset temperature and frequency coupling coefficient, the preset fluorescence thermal quenching coefficient, the magnetic field, the temperature drift suppression rate, and the measurement noise covariance matrix are combined to construct a joint response equation.

[0034] Optionally, the joint response equation is decoupled to generate a global magnetic field estimate value, and based on the global magnetic field estimate value and a preset vacuum permeability, a current density distribution map is determined, including:

[0035] The magnetic field influencing factors and temperature influencing factors in the joint response equation are decoupled using a Bayesian filtering algorithm to obtain a global magnetic field estimate value;

[0036] According to the current probe spatial coordinates and the conductor coordinates, the perpendicular distance between the probe and the conductor is determined;

[0037] Based on Ampere's law, the global magnetic field estimate value, the perpendicular distance, and a preset vacuum permeability are used to calculate a current estimate value.

[0038] Performing a curl operation on the global magnetic field estimation value, the preset vacuum permeability and a preset cylindrical coordinate system tangent unit vector to generate a current density distribution map;

[0039] According to the magnetic field resolution corresponding to the global magnetic field estimation value, the preset vacuum permeability and the vertical distance, a current resolution is determined.

[0040] The second aspect of the present application provides an NV color center magnetic field and current measurement system, comprising:

[0041] The acquisition module is configured to acquire an initial magnetic field signal containing environmental thermal noise, and construct a quantum coherence enhancement pulse sequence using the initial magnetic field signal containing environmental thermal noise.

[0042] The control module is configured to control the spin state of the NV color center through the quantum coherence enhancement pulse sequence, and determine the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity.

[0043] The processing module is configured to decompose and denoise the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to generate target three-dimensional data.

[0044] The construction module is configured to construct a joint response equation by combining the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time-domain fluorescence intensity.

[0045] The decoupling processing module is configured to perform decoupling processing on the joint response equation to generate a global magnetic field estimation value, and determine a current density distribution map according to the global magnetic field estimation value and a preset vacuum permeability.

[0046] The third aspect of the present application provides a computer readable storage medium having a computer program stored thereon, wherein the computer program is executed to implement the NV color center magnetic field and current measurement method according to any one of the above aspects.

[0047] The fourth aspect of the present application provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer executes the NV color center magnetic field and current measurement method according to any one of the above aspects.

[0048] From the above technical solutions, the present application has the following advantages:

[0049] The application firstly acquires an initial magnetic field signal containing environmental thermal noise and constructs a quantum coherence enhancement pulse sequence, regulates the NV color center spin state by using the sequence to determine the optical detection magnetic resonance spectrum and the time domain fluorescence intensity; then decomposes and denoises the two to generate target three-dimensional data, and constructs a joint response equation combined with the resonance frequency offset and the fluorescence intensity change value of the target three-dimensional data; finally, the global magnetic field estimation value is obtained by decoupling the equation, and the current density distribution map is determined according to the value and the vacuum magnetic permeability. The application improves the initial signal quality through the quantum coherence enhancement pulse sequence, effectively weakens the influence of environmental thermal noise and other interferences on the magnetic field signal through decomposition, denoising and decoupling of the joint response equation, and accurately extracts the magnetic field characteristics, thereby providing high-precision data support for subsequent magnetic field analysis and current density distribution determination. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0051] Figure 1 A step flow chart of an NV color center magnetic field and current measurement method provided by the first embodiment of the present application.

[0052] Figure 2 A structural block diagram of an NV color center magnetic field and current measurement system provided by the second embodiment of the present application. DETAILED DESCRIPTION

[0053] The embodiments of the present application provide an NV color center magnetic field and current measurement method and system, which are used to solve the technical problem that environmental thermal noise and other interferences generally exist in the prior art, so that the initially collected magnetic field signal is mixed with a large amount of noise, which seriously affects the analysis of the subsequent magnetic field and current.

[0054] In order to make the purposes, characteristics and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the following described embodiments are only some embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0055] Please refer to Figure 1 , Figure 1 A step flow chart of an NV color center magnetic field and current measurement method provided by the first embodiment of the present application.

[0056] The application provides a NV color center magnetic field and current measurement method, which comprises the following steps:

[0057] In step 101, an initial magnetic field signal containing environmental thermal noise is obtained, and a quantum coherence enhancement pulse sequence is constructed by using the initial magnetic field signal containing environmental thermal noise.

[0058] In the embodiment of the application, the environmental thermal noise refers to random noise generated by the thermal motion of electrons in a conductor, which widely exists in various measurement environments, and the power spectral density thereof is proportional to the absolute temperature of the environment.

[0059] The initial magnetic field signal containing environmental thermal noise refers to the acquisition of a special magnetic sensor, which is sensitive to the change of the magnetic field in the environment and can convert the magnetic field strength into an electrical signal output, but inevitably introduces environmental thermal noise interference.

[0060] The quantum coherence enhancement pulse sequence (QCE-Pulse sequence) refers to a specific pulse combination for controlling the spin state of a diamond ensemble NV (Nitrogen-Vacancy, nitrogen-vacancy) color center, and the core form is:

[0061]

[0062] In the formula, Laser, 532 nm laser pulse, is used to initialize the NV color center spin state to the ground state , and excite the fluorescence readout signal. The typical pulse width is 3 mu s, and the power is 1 mW / mu m2; is a microwave pulse, which corresponds to the X-axis and Y-axis phases (for controlling the NV color center spin state) respectively, Or state flip, introducing a phase difference (imaginary unit), destroying the phase correlation between noise and spin; : pulse interval time, satisfying ( is the electronic gyromagnetic ratio, is the environmental magnetic field noise bandwidth, is a noise spectrum adaptation parameter ); : pulse repetition number, used to prolong the effective coherence time, when is 128 times, the effective coherence time is prolonged from 10 mu s to 100 mu s.

[0063] Through the diamond quantum sensor (nanodiamond probe containing NV density > 5 ppb), the magnetic field signal in the scene to be measured (i.e. ​This signal naturally contains environmental thermal noise (such as random magnetic interference caused by the thermal motion of conductor electrons), and environmental temperature disturbances must be recorded simultaneously. (Due to thermal drift, the NV level will shift). Next, the ambient magnetic field noise bandwidth in the initial magnetic field signal is utilized ( )(from( Extracting from ( ), the key parameters of the pulse sequence are determined according to the formula ( ( () () represents the electron gyromagnetic ratio. (For noise spectrum adaptation parameters) calculate the pulse interval τ and set the number of pulse repetitions ( (e.g., 128 times, the effective coherence time can be...) (From < 10μs to ≈100μs); combined with a 532 nm laser pulse (initializing the NV color center to the ground state). (and excite fluorescence) (accomplish or Spin state flip) and ( (Introducing phase difference) Microwave pulses (which disrupt the correlation between noise and spin phase) are used to ultimately construct a QCE-Pulse sequence that fits the current noise characteristics.

[0064] It is worth mentioning that this invention integrates the technology of precise measurement of magnetic field / current of diamond NV color center by optically detected magnetic resonance (ODMR) into a systematic algorithm flow, covering the decoupling of physical quantities and the mathematical proof of Heisenberg limit approximation. The input-output logic relationship of each step in this invention is as follows:

[0065] NV centers (nitrogen-vacancy centers) are point defects in the diamond lattice formed by the substitution of carbon atoms with nitrogen atoms, accompanied by adjacent vacancies. Their ground state is a spin triplet. In a static magnetic field The following Zeeman split occurs:

[0066]

[0067] In the formula, , For Bohr magneton, The angle between the magnetic field and the NV axis; through 532 nm laser excitation and microwave resonance manipulation, the fluorescence intensity changes with the microwave frequency to form an ODMR spectrum, whose resonance frequency... ( The zero-field splitting coefficient; (electron gyromagnetic ratio); Bz represents the component of the magnetic field B along the NV color center crystal axis direction, i.e. the projection value of the magnetic field .

[0068] Step 102, the spin state of the NV color center is regulated by a quantum coherence enhancement pulse sequence, and the optical detection magnetic resonance spectrum and the time domain fluorescence intensity are determined.

[0069] In the embodiment of the present application, the NV color center, i.e. the nitrogen-vacancy color center, is a point defect formed by the substitution of a nitrogen atom for a carbon atom and the existence of a vacancy at the adjacent position in the diamond lattice, and the ground state is a spin triplet state (S=1). The Zeeman splitting occurs in the magnetic field, and the magnetic field detection can be realized through laser excitation and microwave regulation.

[0070] Spin state refers to the quantum state of the electron spin of the NV color center. In the present application, it mainly involves the ground state and the excited state , Different spin states can undergo transitions under the action of laser and microwave, and the transition process is accompanied by changes in fluorescence intensity.

[0071] Optical detection magnetic resonance spectrum (ODMR spectrum) refers to the relationship curve of fluorescence intensity with microwave frequency. The resonance peak in the spectrum corresponds to the transition of the spin state of the NV color center, and can reflect the magnetic field information.

[0072] Time domain fluorescence intensity refers to a time domain signal with discrete measurement time t as the horizontal coordinate and fluorescence intensity as the vertical coordinate.

[0073] The quantum coherence enhancement pulse sequence generated according to step 101 is used to regulate the spin state of the NV color center, i.e. the 532 nm laser pulse (typical pulse width 3 μs, power 1 mW / μm²) in the sequence is used to act on the NV color center in the diamond ensemble, so that the spin state of the NV color center is initialized to the ground state At the same time, the laser excites the NV color center to generate a fluorescence signal; then according to the sequence structure of , the X-axis phase microwave pulse ( ) and the Y-axis phase microwave pulse ( ) are alternately applied, wherein the spin state of the NV color center is flipped between or and , the phase difference of the imaginary unit i is introduced to destroy the phase correlation between the environment noise and the spin, the pulse interval τ is determined according to the noise bandwidth in the initial magnetic field signal, and the repetition number N is set to 128 times to effectively extend the coherence time of the NV color center The duration is prolonged from 10 to 100 s. In this regulation process, the fluorescence signal of the NV center is synchronously collected by a single photon counter: on the one hand, the output frequency of the microwave source (frequency range 1-4 GHz) is scanned, and the fluorescence intensity values at different microwave frequencies are recorded to form a curve of the fluorescence intensity versus the microwave frequency, that is, an optical detection magnetic resonance spectrum; on the other hand, the fluorescence intensity data at different times are recorded based on the discrete measurement time t generated by the processor clock to obtain the time-domain fluorescence intensity.

[0074] Further, step 101 comprises the following sub-steps:

[0075] S11, the spin state of the NV center is regulated by the quantum coherence enhancement pulse sequence, and when the spin state of the NV center is in the ground state, the initial fluorescence signal of the NV center is generated by laser excitation.

[0076] In the embodiment of the application, the ground state refers to the stable state with the lowest electron spin energy of the NV center, denoted as , which is the initial target state regulated by the quantum coherence enhancement pulse sequence, and the NV center in the ground state can generate a fluorescence signal after laser excitation.

[0077] The initial fluorescence signal refers to the initial optical signal formed when the NV center transitions from the excited state to the ground state under laser excitation, and its intensity is related to the spin state of the NV center, the laser power and the environmental noise.

[0078] The 532 nm laser pulse (typical pulse width 3 s, power 1 mW / m2) in the sequence acts on the NV center in the diamond ensemble, and the spin state of the NV center is initialized to the ground state , and the laser excitation of the NV center generates a fluorescence signal, that is, an initial fluorescence signal.

[0079] S12, a plurality of microwave pulses of different frequencies are applied to the NV center within a preset pulse interval time to obtain a target microwave frequency point.

[0080] In the embodiment of the application, the preset pulse interval time (τ) refers to the fixed time interval between the adjacent two microwave π pulses (π ) and (π ) in the quantum coherence enhancement pulse sequence, which needs to be calculated and determined according to the environmental magnetic field noise bandwidth, and the core function is to adapt to the noise spectrum to suppress interference and prolong the effective coherence time of the NV center.

[0081] The target microwave frequency point refers to the frequency value when the microwave pulse frequency matches the resonance frequency (f ) of the NV center, at which time the fluorescence intensity of the NV center decreases significantly.

[0082] In a preset pulse interval time τ, a microwave source with a frequency range of 1-4 GHz and a Q value of >200 is used to apply microwave pulses covering the ODMR resonance frequency interval to the NV center in the diamond ensemble, and the microwave pulses contain microwave pulses ( ) and microwave pulses ( ); at the same time, the fluorescence intensity change of the NV center is synchronously collected by a single photon counter (efficiency >80%), when the microwave pulse frequency matches the resonance frequency of the NV center , D≈2.87GHz is the zero-field splitting coefficient, is the component of the magnetic field B along the NV center crystal axis), the spin state transition probability of the NV center is significantly improved, and the fluorescence intensity will decrease obviously, and the corresponding microwave frequency is the target microwave frequency point.

[0083] S13, in the regulation period of each target microwave frequency point, the ODMR spectrum is collected.

[0084] In the embodiment of the present application, the regulation period refers to the complete time period of "laser initialization-microwave pulse control-fluorescence collection" for a single target microwave frequency point. In the present application, one regulation period corresponds to N=128 pulse cycles of the quantum coherence enhancement pulse sequence, which ensures that noise can be sufficiently suppressed and stable fluorescence signals can be obtained.

[0085] The regulation period of each target microwave frequency point needs to be synchronized with the pulse repetition rhythm of the quantum coherence enhancement pulse sequence, that is, one regulation period corresponds to N times (N=128 times) of pulse cycles, and the preset pulse interval time τ in the period is still determined according to the environmental magnetic field noise bandwidth in the initial magnetic field signal According to the formula ( is the electronic gyromagnetic ratio, is the environmental magnetic field noise bandwidth, is the noise spectrum fitting parameter); in the regulation period, the NV center spin state is first initialized to the ground state by a 532 nm laser pulse (pulse width 3μs, power 1 mW / μm²) and excited to fluorescence, and then the frequency of the target microwave frequency point is output and Microwave pulse, alternating effect on NV color center to maintain its spin coherence, inhibit environmental noise interference; at the same time, using the single photon counter with efficiency > 80% continuously collect the fluorescence intensity data of NV color center in this period, record the change rule of fluorescence intensity with time, then the average value of fluorescence intensity corresponding to the target microwave frequency point is associated with the fluorescence intensity data of other microwave frequency points scanned in the early stage, form the corresponding relationship curve of "microwave frequency-fluorescence intensity", that is, complete the data acquisition of ODMR spectrum of light detection in the control period of the target microwave frequency point . .

[0086] S14, integrate the initial fluorescence signal of each spatial pixel point in the control period of the target microwave frequency point to obtain the total fluorescence integral intensity of each spatial pixel point.

[0087] In the embodiment of the application, the spatial pixel point refers to the smallest spatial unit divided when the nanodiamond probe scans the to-be-measured region, and the total number of pixels P is determined by the scanning step (such as 256*256), and each pixel point corresponds to a micro spatial position of the to-be-measured region.

[0088] The total fluorescence integral intensity refers to the intensity value obtained by time-domain integration of the initial fluorescence signal of a single spatial pixel point in the control period of the target microwave frequency point.

[0089] For each spatial pixel point covered by the nanodiamond probe, the initial fluorescence signal generated by the NV color center excited by the 532 nm laser is collected in real time in the control period of the corresponding target microwave frequency point through the single photon counter; then the discrete measurement time t generated by the processor clock is taken as the integration interval (the integration time is synchronized with the control period), and the time-domain integration operation is performed on the initial fluorescence signal of each spatial pixel point in the period, that is, the fluorescence intensity values at different times are accumulated, the influence of transient noise on the signal is eliminated, and finally the total fluorescence integral intensity of each spatial pixel point under the target microwave frequency point is obtained.

[0090] S15, calculate the sum of the total fluorescence integral intensity of all spatial pixel points to generate the time-domain fluorescence intensity.

[0091] In the embodiment of the present application, the measured time t generated by the processor clock is taken as the reference, and a plurality of continuous time units are divided according to preset time intervals (synchronized with the operation rhythm of the pulse sequence), each time unit corresponding to a complete "full space pixel signal acquisition-total fluorescence integral intensity calculation" process; then, in each time unit, the total fluorescence integral intensity of all spatial pixels is summed to obtain the fluorescence intensity sum corresponding to the time unit; and then the fluorescence intensity sums of different time units are arranged in chronological order to form a time-domain signal with the measured time t as the horizontal coordinate and the total fluorescence intensity of the full space as the vertical coordinate, that is, to generate the time-domain fluorescence intensity.

[0092] It is worth mentioning that the time-domain signal integral intensity of each spatial pixel (P points) forms a fluorescence intensity matrix , .

[0093] Further, the method further includes the following sub-steps:

[0094] S21, when the quantum coherence enhancement pulse sequence controls the spin state of the NV center, the preset pulse interval time, the pulse repetition number and the intrinsic decoherence time are obtained.

[0095] In the embodiment of the present application, the pulse repetition number refers to the cycle number of the quantum coherence enhancement pulse sequence unit.

[0096] The intrinsic decoherence time refers to the characteristic time of the natural decay of the NV center spin state coherence due to environmental disturbance (such as lattice vibration, spin-spin interaction) without active control (such as without microwave pulse intervention).

[0097] When the quantum coherence enhancement pulse sequence controls the spin state of the NV center in the diamond ensemble, first, the environmental magnetic field noise bandwidth extracted from the initial magnetic field signal is calculated and obtained according to the formula to obtain the preset pulse interval time , which needs to be accurately matched with the noise spectrum to weaken the environmental disturbance; then, according to the requirement of improving the effective coherence time of the NV center, the pulse repetition number N is set and obtained, N = 128 times in the present application, and through the pulse cycle of this number, the effective coherence time of the NV center can be extended from < 10 μs to ≈ 100 μs; at the same time, in the process of pulse sequence control, the natural decay process of the NV center spin state coherence is monitored, that is, the decay curve of the initial fluorescence signal with time is recorded, and the intrinsic decoherence time of the NV center is obtained through the inversion calculation combined with the fluorescence response function.

[0098] S22. Determine the effective decoherence time of the NV color center based on the preset pulse interval time, pulse repetition number, and intrinsic decoherence time.

[0099] In this embodiment of the invention, the effective decoherence time refers to the actual time during which the spin state maintains coherence after being modulated by the quantum coherence enhancement pulse sequence of the NV color center. It is a comprehensive reflection of the intrinsic decoherence time and the effect of pulse sequence modulation.

[0100] Specifically, the original decoherence time limit is:

[0101] The free induction decay (FID) time of NV color centers is determined by environmental noise (magnetic field noise, lattice vibration, etc.), with a typical value of <10 μs.

[0102] ;

[0103] In the formula, This refers to the intrinsic decoherence time (related to diamond purity, typically >1 ms). The ambient magnetic field noise amplitude (approximately 1 μT / √Hz); It is the electron gyromagnetic ratio.

[0104] In this invention, the effective decoherence time can be extended by using a quantum coherence enhancement pulse (QCE-Pulse) after suppression by the QCE-Pulse sequence. The specific calculation formula is as follows:

[0105]

[0106] In the formula, N is the number of pulse repetitions; The preset pulse interval time; This refers to the relevant time for the collection and withdrawal of taxes.

[0107] S23. Based on the effective decoherence time of the NV color center, adjust the initial acquisition sensitivity of the photodetector magnetic resonance spectrum and time-domain fluorescence intensity to generate the target acquisition sensitivity.

[0108] In this embodiment of the invention, the initial acquisition sensitivity refers to the original sensitivity of detectable magnetic field changes before optimization by incorporating effective decoherence time.

[0109] Target acquisition sensitivity refers to the optimal sensitivity for detecting changes in the magnetic field achieved after adjusting the acquisition parameters in conjunction with the effective decoherence time.

[0110] It can improve magnetic field sensitivity (i.e., acquisition sensitivity):

[0111] Magnetic field sensitivity defined as the minimum detectable magnetic field change (unit: T / √Hz), whose theoretical limit is:

[0112]

[0113] where, is the fluorescence photon collection rate (related to NV density, optical efficiency) ; is the total measurement time; is the electron gyromagnetic ratio.

[0114] And the magnetic field sensitivity is improved with the increase of , which is specifically manifested as:

[0115] Traditional ODMR ( ) :

[0116]

[0117] QCE-Pulse after optimization ( ) :

[0118]

[0119] According to the increase of , the magnetic field sensitivity is improved by 10 times (corresponding to 14 dB signal-to-noise ratio gain).

[0120] Compared with the theoretical Heisenberg limit , the optimized is closer.

[0121] Further, the method further includes the following sub-steps:

[0122] S31, acquiring the measurement time, the electron gyromagnetic ratio, the temperature disturbance value, and the angle between the magnetic field corresponding to the initial magnetic field signal containing the environmental thermal noise and the axial direction of the NV color center.

[0123] In the embodiment of the present application, the measurement time refers to a discrete digital time signal for recording the change of the NV color center signal, which is generated by a processor clock and needs to be synchronized with the control period of the quantum coherence enhancement pulse sequence.

[0124] The electron gyromagnetic ratio refers to the physical constant of the ratio of the electron spin magnetic moment to the angular momentum.

[0125] The temperature disturbance value refers to the difference (ΔT=T 实测 -T0) between the actual measurement environment temperature and the undisturbed reference temperature T0, which is used to correct the temperature drift of the zero-field splitting coefficient D.

[0126] The angle between the magnetic field and the axial direction of the NV color center refers to the angle between the measured magnetic field vector and the axial direction of the NV color center, which is a calibrated value.

[0127] When obtaining the initial magnetic field signal containing environmental thermal noise, the measurement time t, the temperature disturbance value and the angle between the magnetic field and the NV axial direction are also obtained.

[0128] S32, the effective dephasing time, the initial magnetic field signal containing environmental thermal noise, the measurement time, the angle, the preset Gaussian white noise, the electronic gyromagnetic ratio and the initial fluorescence intensity corresponding to the initial fluorescence signal are used to calculate the fluorescence response function.

[0129] In the embodiment of the present application, the preset Gaussian white noise refers to a preset noise term simulating random noise interference in actual measurement.

[0130] The initial fluorescence intensity refers to the reference fluorescence intensity value extracted from the initial fluorescence signal, which is related to the 532 nm laser power and the NV color center density, and is used as the first reference value of the fluorescence response function to determine the initial amplitude of the fluorescence intensity.

[0131] The calculation formula of the fluorescence response function is:

[0132]

[0133] In the formula, is the initial fluorescence intensity (related to the laser power and the NV density); is the parallel component of the magnetic field; is the Gaussian white noise (standard deviation ); is the effective dephasing time; t is the measurement time; is the electronic gyromagnetic ratio.

[0134] Mainly simulate the quantum state evolution of the NV color center under the pulse sequence, and output the time domain fluorescence signal .

[0135] S33, according to the initial resonance frequency offset corresponding to the time domain fluorescence intensity, the temperature disturbance value and the temperature offset rate of the preset zero field splitting coefficient, determine the thermal drift compensation amount.

[0136] In the embodiment of the present application, the initial resonance frequency offset refers to the difference between the resonance frequency extracted from the FFT peak value of the time domain fluorescence intensity and the reference value of the zero field splitting coefficient D0, which contains the contribution of the measured magnetic field and the interference of the temperature drift, and is the original input parameter of the thermal drift compensation.

[0137] The temperature offset rate of the preset zero field splitting coefficient refers to the rate of change of the zero field splitting coefficient D with temperature.

[0138] The thermal drift compensation amount refers to the corrected resonance frequency offset.

[0139] The calculation formula of the thermal drift compensation amount is:

[0140]

[0141] In the formula, is the original resonance frequency offset (from the FFT peak value of ); is the preset zero-field splitting coefficient ; and is the temperature disturbance value.

[0142] The formula mainly eliminates the interference of temperature on the ODMR resonance frequency, and improves the magnetic field measurement accuracy.

[0143] Step 103, decompose and denoise the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to generate target three-dimensional data.

[0144] In the embodiment of the application, the decomposition and denoising processing refers to the process of feature extraction and noise filtering of the ODMR data and the fluorescence intensity through the combined operation of tensor lifting + Tucker decomposition + ALS optimization.

[0145] The target three-dimensional data refers to a data set containing “frequency-space-orientation” three-dimensional information formed by the third-order tensor and the characteristic frequency matrix after denoising, and the signal-to-noise ratio is improved by more than 10 dB.

[0146] First, the time-domain enhanced collected in the early stage (F is the frequency point number, and P is the spatial pixel number) and the fluorescence intensity matrix are lifted to a third-order tensor (frequency × space × orientation) through a fold operation. The lifting process can introduce the “orientation” dimension (O=4 is the number of NV color center orientation categories), and solve the problem of overlapping magnetic response signals of different orientations of NV color centers in traditional two-dimensional processing; then, Tucker decomposition is used to extract features from the third-order tensor X, and the core tensor , the frequency factor matrix , the spatial factor matrix , and the orientation factor matrix are iteratively updated through alternating least squares (ALS) optimization until the loss function converges. During the decomposition process, high-dimensional components dominated by random noise are set to zero by truncating high-order singular values (the first four principal components are retained); then, based on the converged , 、 、 , the denoised tensor is calculated by tensor n-module product , and the resonance frequency of each spatial point and crystal direction is extracted from the core tensor , finally, the denoised tensor is integrated with the characteristic frequency matrix to generate target three-dimensional data containing three-dimensional information of frequency, space and crystal direction.

[0147] Further, step 103 comprises the following sub-steps:

[0148] S41, dimensionally processing the optical detection magnetic resonance spectrum and the time domain fluorescence intensity to obtain initial three-dimensional data.

[0149] In the embodiment of the application, the dimensionally processing refers to the process of increasing the order of the data of the optical detection magnetic resonance spectrum and the fluorescence intensity matrix by fold operation.

[0150] The initial three-dimensional data refers to the initial three-dimensional data (frequency×space×crystal direction) obtained after dimensionally processing.

[0151] The input , two-dimensional data is increased to a three-order tensor, and the core significance of increasing the two-dimensional data (frequency×space) to a three-order tensor (frequency×space×crystal direction) can solve the prominent contradictions in NV color center ensemble measurement through modal separation:

[0152] Interference of crystal direction difference: there are four crystal directions of NV color centers in diamond, and the projection of magnetic field is different in different axial directions. Traditional two-dimensional fitting will cause resonance peak overlap.

[0153] Complexity of noise coupling: the coupling modes of environmental noise (such as electromagnetic interference, temperature drift) are different in different crystal directions, and two-dimensional processing will confuse noise and real signal.

[0154] After dimensionally increasing, the tensor decomposition decouples the mixed signal into independent components through characteristic, which essentially increases the "crystal direction" dimension to provide physical constraint conditions for the algorithm.

[0155] The specific calculation formula is:

[0156] ;

[0157] ;

[0158] ​In the formula, F is a frequency point number (ODMR spectrum resolution, usually ); P is a spatial pixel number (depending on the probe scanning step, such as ); O is a number of NV crystal direction categories (in diamond , there are four types of <100>, <110> and <111> axes); and fold is a matrix operation for upgrading low-dimensional data to high-order tensors.

[0159] Through spatial-frequency-crystal direction three-dimensional decomposition, magnetic response signals of different NV axes are separated.

[0160] S42, Tucker decomposition processing and alternating least squares optimization processing are performed on the initial three-dimensional data to generate target three-dimensional data after noise reduction and a resonance frequency matrix of each spatial point and crystal direction.

[0161] In the embodiment of the present application, Tucker decomposition processing (Tucker decomposition) refers to a high-order tensor decomposition method, which can decompose a three-order tensor X into a core tensor and multiple one-dimensional factor matrices.

[0162] Alternating least squares (ALS, Alternating Least Squares) optimization processing refers to an iterative optimization algorithm of Tucker decomposition, which fixes part of the parameters, alternately updates another part of the parameters, minimizes the Frobenius norm error of the original tensor and the reconstructed tensor, and converges to a preset threshold until the error converges to the preset threshold. The threshold set by the present application is .

[0163] The resonance frequency matrix refers to a matrix characterizing the resonance frequency corresponding to each spatial point (P) and each crystal direction (O=4 types).

[0164] Tucker decomposition extracts features:

[0165]

[0166] In the formula, is a core tensor (storing a characteristic frequency mode); is a frequency factor matrix (a main frequency component, ), the frequency factor matrix extracts a Zeeman splitting main frequency component (corresponding to magnetic field information); is a spatial factor matrix (noise distribution characteristics) through spatial sparse constraints, 50 nm resolution (breaking the diffraction limit) can be achieved, and the spatial factor matrix characterizes the spatial distribution characteristics of noise (such as probe vibration noise); is a crystal direction factor matrix (axial weight, ), and the crystal direction factor matrix Identify the weight distribution of the 4 classes of NV axial.

[0167] Core tensor Separate the weight of the crystal direction, factor matrix Identify the contribution weight of different crystal direction NV, solve the problem of spectral line overlap.

[0168] The formula mainly initializes the high-order tensor: for Modal expansion, and calculate the singular value decomposition (SVD) initialization factor matrix.

[0169] In actual calculation, alternating least squares (ALS) optimization can be used: iteratively update And Until convergence (loss function ) can complete the iteration.

[0170] Noise filtering principle after upgrading: the real signal (magnetic field response) has low rank characteristics in the frequency-crystal direction dimension, while the random noise has no structure characteristics in the full dimension. When decomposed, by truncating the high-order singular value (keeping the first The high-dimensional component dominated by noise is forced to zero. The crystal direction factor matrix Implicitly associated with the quantum state of the NV color center, further suppress classical noise by projecting into Hilbert space.

[0171] After noise reduction and feature extraction, we get:

[0172] ;

[0173] ;

[0174] In the formula, The three-dimensional data after improving the signal-to-noise ratio (typical SNR gain > 10 dB); The resonance frequency representing each spatial point and crystal direction (used to calculate ), where The complete formula of , the specific writing of part of the formula should be , which represents the maximum value position of the frequency dimension f of the core tensor G. The complete implementation needs to calculate each p independently; The dimension of Matrix (frequency x space), store the magnetic field-space coupling characteristic spectrum of the oth crystal direction; Tensor n module product.

[0175] The measured ODMR spectral line full width at half maximum (FWHM) is reduced from 12 MHz to 4 MHz, close to the single NV color center limit, effectively improving the signal-to-noise ratio.

[0176] Step 104: Combine the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data with the fluorescence intensity change value corresponding to the time domain fluorescence intensity to construct a joint response equation.

[0177] In this embodiment of the invention, the resonance frequency offset refers to the difference between the resonance frequency of each spatial point and each crystal orientation in the target three-dimensional data and the zero-field splitting coefficient reference value D0.

[0178] The change in fluorescence intensity refers to the ratio of the total integrated fluorescence intensity at each spatial point to the initial fluorescence intensity. The difference.

[0179] The joint response equation refers to a mathematical equation that integrates the resonant frequency shift and the fluorescence intensity change, based on the physical mechanism of the NV color center magnetic response. It correlates the magnetic field magnitude, crystal orientation angle, and the characteristics of the two types of signals, providing a unified model for decoupled calculation of magnetic field estimates.

[0180] Extract the first resonance frequency of each space point (P points) and each crystal orientation (O=4 types). The difference between the value and the preset zero-field splitting coefficient reference value D0 is calculated. At the same time, the fluorescence intensity change value of each spatial point is extracted from the fluorescence intensity in the time domain to obtain the resonance frequency offset, which is used to correlate the influence of the magnetic field on the spin state transition probability of the NV color center. Then, a joint response equation is constructed based on the physical mechanism of the magnetic response of the NV color center.

[0181] Furthermore, step 104 includes the following sub-steps:

[0182] S51. The first resonance frequency of each spatial point and crystal orientation is extracted from the target three-dimensional data using the fast Fourier transform method.

[0183] In this embodiment of the invention, the Fast Fourier Transform method refers to...

[0184] First resonant frequency ( ), which refers to the resonance frequency of all spatial points (P points) and all crystal orientations (O=4 types).

[0185] From the noise reduction tensor Extract each spatial point and each crystal orientation resonant frequency The specific formula is as follows:

[0186]

[0187] In the formula, For Fast Fourier Transform (FFT); For the first Pixel, First Resonance frequency of crystal orientation.

[0188] S52, determine the temperature drift correction amount of the zero-field splitting coefficient based on the reference value of the preset zero-field splitting coefficient, the temperature offset rate of the preset zero-field splitting coefficient, and the temperature drift suppression rate.

[0189] In the embodiment of the application, the reference value of the preset zero-field splitting coefficient refers to the energy level splitting frequency between the NV color center ground state spin triplet states (|A|, |B| and |E|) when there is no temperature disturbance and no external magnetic field, and the typical value is approximately 2.87 GHz. 、 、 ) between the NV color center ground state spin triplet states (|A|, |B| and |E|) when there is no temperature disturbance and no external magnetic field, and the typical value is approximately 2.87 GHz.

[0190] The temperature offset rate of the preset zero-field splitting coefficient refers to the change amount of the zero-field splitting coefficient caused by a unit temperature change (1K), and the experimental calibration is -74 kHz / K. The negative sign indicates that the zero-field splitting coefficient decreases when the temperature rises, and is used to quantify the influence degree of temperature on the energy level splitting.

[0191] The temperature drift suppression rate refers to the proportion of temperature interference suppression achieved by the quantum coherence enhancement pulse sequence or the auxiliary temperature control module.

[0192] The temperature drift correction amount of the zero-field splitting coefficient refers to the actual influence amount of the remaining temperature disturbance on the zero-field splitting coefficient after considering the temperature drift suppression rate.

[0193] The temperature drift correction of the preset zero-field splitting coefficient is used to eliminate the energy level offset caused by thermal expansion:

[0194]

[0195] In the formula, is the temperature drift correction amount of the zero-field splitting coefficient; D0 is the reference value of the preset zero-field splitting coefficient; is the temperature offset rate of the preset zero-field splitting coefficient; is the temperature drift suppression rate.

[0196] S53, calculate the difference between the first resonance frequency and the reference value of the preset zero-field splitting coefficient to generate a resonance frequency offset.

[0197] In the embodiment of the application, the resonance frequency offset refers to the difference (including temperature interference) between the first resonance frequency and the reference value of the preset zero-field splitting coefficient. The calculation formula of the resonance frequency offset is:

[0198]

[0199] In the formula, is the first resonance frequency; D0 is the reference value of the preset zero-field splitting coefficient.

[0200] S54, determining a fluorescence intensity change value according to the current measured fluorescence integral intensity corresponding to the time domain fluorescence intensity and the baseline intensity without disturbance.

[0201] In the embodiment of the application, the current measured fluorescence integral intensity refers to the total fluorescence intensity obtained by performing initial time domain integration of the fluorescence signal on a single spatial pixel point according to the target microwave frequency point regulation period (including N=128 quantum coherence enhancement pulse sequence cycles) in the actual measurement scene with the presence of the to-be-measured magnetic field.

[0202] The baseline intensity without disturbance refers to the total fluorescence integral intensity obtained by regulating and integrating a single spatial pixel point in the same way as the actual measurement in the calibration scene without the to-be-measured magnetic field and with the complete suppression of environmental interference.

[0203] The fluorescence intensity change value refers to the difference between the current measured fluorescence integral intensity of a single spatial pixel point and the baseline intensity without disturbance.

[0204] Specifically, the calculation formula of the fluorescence intensity change value is:

[0205]

[0206] In the formula, I FL,p is the current measured fluorescence integral intensity; I FL,p 0 is the baseline intensity without disturbance (reference temperature T0).

[0207] S55, jointly constructing a joint response equation by using the resonance frequency shift, the fluorescence intensity change value, the electron spin magnetic ratio, the preset temperature and frequency coupling coefficient, the preset fluorescence thermal quenching coefficient, the magnetic field, the temperature drift suppression rate, and the measurement noise covariance matrix.

[0208] In the embodiment of the application, the preset temperature and frequency coupling coefficient refers to the influence coefficient of the temperature residual interference on the resonance frequency in the experimental calibration, and is used to quantify the slight interference of the remaining temperature after the temperature drift suppression on the frequency.

[0209] The preset fluorescence thermal quenching coefficient refers to the attenuation coefficient of the temperature on the NV color center fluorescence intensity.

[0210] The measurement noise covariance matrix refers to a 2x2 matrix of statistical characteristics of the resonance frequency shift and the fluorescence intensity change value measurement noise, and the diagonal elements are the variances of the two types of noise

[0211] Specifically, the calculation formula of the joint response equation is:

[0212]

[0213] In the formula, Y for resonance frequency shift; for fluorescence intensity change (pure temperature probe); for preset temperature-frequency coupling coefficient, ; for fluorescence thermal quenching coefficient (experimentally calibrated) ; for measurement noise covariance matrix.

[0214] Step 105, decoupling processing is performed on the joint response equation to generate a global magnetic field estimation value, and a current density distribution map is determined according to the global magnetic field estimation value and a preset vacuum magnetic permeability.

[0215] In the embodiment of the present application, the decoupling processing refers to a processing process in which a weighted least square method is used to take the inverse matrix of the measurement noise covariance matrix as the weight, minimize the objective function to eliminate the interference of the temperature disturbance value on the magnetic field calculation, so as to extract the magnetic field estimation value alone.

[0216] The global magnetic field estimation value refers to a matrix formed by arranging the local magnetic field estimation values of all spatial pixels according to the spatial positions, covering the entire to-be-measured region, and can completely reflect the distribution rule of the magnetic field in space.

[0217] The preset vacuum magnetic permeability refers to a physical constant of the relationship between the magnetic field and the current in the vacuum environment.

[0218] The current density distribution map refers to an image formed by mapping the current density (size and direction) of each spatial pixel according to the spatial coordinates.

[0219] The weighted least square method is used to decouple the joint response equation, and the influence of the temperature disturbance value is eliminated through iterative calculation to obtain the local magnetic field estimation value of each spatial pixel p; then the local magnetic field estimation values of all spatial pixels are arranged according to the spatial positions to form a global magnetic field estimation value matrix covering the entire to-be-measured region; finally, according to the Ampere loop theorem, in combination with the preset vacuum magnetic permeability, the current density size and direction corresponding to each spatial pixel are calculated through the correlation between the magnetic field and the current density, and then the current densities of all spatial pixels are mapped according to the spatial coordinates to generate the current density distribution map of the to-be-measured region.

[0220] Further, step 105 includes the following sub-steps:

[0221] S61, the magnetic field influencing factor and the temperature influencing factor in the joint response equation are decoupled by using a Bayesian filtering algorithm to obtain a global magnetic field estimation value.

[0222] In the embodiments of the present application, the Bayesian filtering algorithm refers to a recursive state estimation algorithm based on the Bayes theorem, which realizes the state estimation of a dynamic system through two steps of prediction (calculating the prior probability) and update (correcting the prior to obtain the posterior probability) by constructing a state space model (including a state transition model and an observation model).

[0223] The magnetic field influencing factor refers to a parameter related to the to-be-measured magnetic field in the joint response equation, and specifically refers to a local magnetic field B p (single spatial pixel point magnetic field size), which is the core target quantity of decoupling processing.

[0224] The temperature influencing factor refers to a parameter related to the temperature disturbance in the joint response equation, and specifically refers to a temperature disturbance value (a difference between a measured temperature and a reference temperature), which is a key factor interfering with the magnetic field estimation and needs to be separated from the magnetic field influencing factor through the Bayesian filtering.

[0225] The process of calculating the global magnetic field estimation value using the Bayesian filtering algorithm is as follows:

[0226]

[0227] In the formula, is a to-be-estimated state vector; is an observation vector. H is a joint response equation.

[0228] The posterior estimation is maximized:

[0229]

[0230] The magnetic field component explicit solution is:

[0231] The magnetic field estimation value of a single spatial pixel point p is:

[0232] In the formula, is a joint response matrix, is a thermal noise covariance; is a resonance frequency offset; is a fluorescence intensity change (pure temperature probe); is a preset temperature-frequency coupling coefficient; is a fluorescence thermal quenching coefficient.

[0233] wherein, is the total number of pixels, and the global magnetic field estimation value .

[0234] S62, determine the vertical distance between the probe and the conductor according to the current probe spatial coordinates and the conductor coordinates. ​

[0235] In the embodiments of the present application, the current probe space coordinates refer to the three-dimensional coordinates of the quantum sensing probe carrying the diamond ensemble NV color center in the global coordinate system.

[0236] The conductor coordinates refer to the coordinate data representing the spatial position and geometric shape of the conductor to be measured.

[0237] The vertical distance refers to the shortest spatial distance from the probe tip (NV color center sensitive area) to the surface of the conductor.

[0238] Specifically, the calculation formula of the vertical distance between the probe and the conductor is:

[0239]

[0240] In the formula, r is the current probe space coordinates; is the conductor coordinates.

[0241] S63, based on Ampere's law, using the global magnetic field estimate, the vertical distance and the preset vacuum permeability, the current estimate is calculated.

[0242] In the embodiments of the present application, Ampere's law refers to the full current law, which is one of the core laws of electromagnetism.

[0243] The current estimate refers to the size of the current flowing in the conductor calculated based on the simplified formula of Ampere's law.

[0244] The calculation process of the current based on Ampere's law is:

[0245]

[0246] In the formula, is the vertical distance between the probe and the conductor (unit: m, default 50 nm); is the preset vacuum permeability; is the magnetic field estimate of a single spatial pixel point p, ignoring the parallel magnetic field component (B main).

[0247] S64, the global magnetic field estimate, the preset vacuum permeability and the preset cylindrical coordinate system tangential unit vector are operated by the rotation rate to generate a current density distribution map.

[0248] In the embodiments of the present application, the preset cylindrical coordinate system tangential unit vector refers to the unit vector along the circumferential tangent direction of the cylindrical coordinate system.

[0249] The rotation rate operation refers to the differential operation of the rotation characteristics of the vector field (such as the magnetic field), which can be simplified in the cylindrical coordinate system combined with the axisymmetric magnetic field distribution, and its result is directly related to the current density.

[0250] Specifically, the current density distribution map is generated The calculation formula of the spatial resolution (50 nm) is:

[0251]

[0252] In the formula, is a preset cylindrical coordinate system tangential unit vector; is a curl operation (spatial derivative); is a magnetic field estimation value of a single spatial pixel point p.

[0253] In this way, the current density vector can be inversely calculated through the magnetic field spatial gradient.

[0254] S65, according to the magnetic field resolution corresponding to the global magnetic field estimation value, the preset vacuum permeability and the vertical distance, the current resolution is determined.

[0255] In the embodiment of the present application, the magnetic field resolution refers to the minimum magnetic field change amount that can be distinguished by the system for the global magnetic field estimation value.

[0256] The current resolution refers to the minimum current change amount that can be distinguished by the system.

[0257] The magnetic field resolution corresponding to the global magnetic field estimation value is the minimum magnetic field change amount (unit: T) that can be distinguished by the system after decoupling and tensor denoising by Bayesian filtering, and the value is determined by the frequency point number of the target three-dimensional data, the spatial pixel density and the quantum coherence enhancement pulse sequence control effect. In the present application, the magnetic field resolution can be stably reached 5 nT.

[0258] Specifically, the calculation formula of the current resolution is:

[0259] (error linear transmission)

[0260] In the formula, is the magnetic field resolution; is the vertical distance between the probe and the conductor; is the preset vacuum permeability.

[0261] Through the formula, the error of current measurement can be reduced.

[0262] It is worth mentioning that the present application prolongs the effective coherence time of the NV color center to 100 μs through the quantum coherence enhancement pulse (QCE-Pulse), so that the magnetic field sensitivity is improved. In addition, the multi-modal tensor decomposition technology also solves the problem of spectral line overlap in the traditional ensemble NV measurement, and the signal-to-noise ratio is improved by more than 10 dB. And through the physical quantity decoupling model and the Bayesian inversion, the temperature drift interference is actively eliminated, the current resolution is improved, and it is suitable for strong noise environment.

[0263] and reaction true magnetic field sensitivity , and the magnetic field sensitivity reaction to the accuracy of the magnetic field change capture, and the magnetic field change and the current change are related, which can be used to observe the current contrast.

[0264] The magnetic field / current density image can reflect the distribution of the magnetic field and the current in space, so it can be used to analyze whether the magnetic field and the electric field exist spatial distortion, which has very important practical significance for the evaluation of the electromagnetic environment.

[0265] The current resolution is used to indicate the accuracy of the current measurement, which can directly reflect how accurate the current measurement is.

[0266] Please refer to Figure 2 , Figure 2 The structure block diagram of an NV color center magnetic field and current measurement system provided by the second embodiment of the present application.

[0267] The NV color center magnetic field and current measurement system provided by the present application comprises:

[0268] The acquisition module 201 is configured to acquire an initial magnetic field signal containing environmental thermal noise, and construct a quantum coherence enhancement pulse sequence by using the initial magnetic field signal containing the environmental thermal noise.

[0269] The control module 202 is configured to control the spin state of the NV color center by using the quantum coherence enhancement pulse sequence, and determine the optical detection magnetic resonance spectrum and the time domain fluorescence intensity.

[0270] The processing module 203 is configured to perform decomposition and noise reduction processing on the optical detection magnetic resonance spectrum and the time domain fluorescence intensity, and generate target three-dimensional data.

[0271] The construction module 204 is configured to construct a joint response equation by combining the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time domain fluorescence intensity.

[0272] The decoupling processing module 205 is configured to perform decoupling processing on the joint response equation, generate a global magnetic field estimation value, and determine a current density distribution map according to the global magnetic field estimation value and a preset vacuum magnetic permeability.

[0273] Further, the control module 202 comprises:

[0274] The excitation sub-module is configured to control the spin state of the NV color center by using the quantum coherence enhancement pulse sequence, and when the spin state of the NV color center is in the ground state, the laser excites the NV color center to generate an initial fluorescence signal.

[0275] ​The application sub-module is configured to apply microwave pulses of multiple frequencies to the NV color center within a preset pulse interval time to obtain a target microwave frequency point;

[0276] The acquisition sub-module is configured to acquire an optically detected magnetic resonance spectrum within a regulation period of each target microwave frequency point;

[0277] The integration sub-module is configured to integrate the initial fluorescence signal of each spatial pixel point within the regulation period of the target microwave frequency point to obtain a total fluorescence integral intensity of each spatial pixel point;

[0278] The sum sub-module is configured to calculate the sum of the total fluorescence integral intensities of all spatial pixel points to generate a time-domain fluorescence intensity.

[0279] Further, the system comprises:

[0280] The acquisition sub-module is configured to acquire a preset pulse interval time, a pulse repetition number, and an intrinsic decoherence time when the quantum coherence enhancement pulse sequence regulates the spin state of the NV color center;

[0281] The effective decoherence time sub-module is configured to determine an effective decoherence time of the NV color center according to the preset pulse interval time, the pulse repetition number, and the intrinsic decoherence time;

[0282] The adjustment sub-module is configured to adjust the initial acquisition sensitivity of the optically detected magnetic resonance spectrum and the time-domain fluorescence intensity according to the effective decoherence time of the NV color center to generate a target acquisition sensitivity.

[0283] Further, the system comprises:

[0284] The angle sub-module is configured to acquire a measurement time, an electronic gyromagnetic ratio, a temperature disturbance value, and an angle between an axis of the NV color center and a magnetic field corresponding to an initial magnetic field signal containing environmental thermal noise;

[0285] The calculation function sub-module is configured to calculate a fluorescence response function using the effective decoherence time, the initial magnetic field signal containing environmental thermal noise, the measurement time, the angle, a preset Gaussian white noise, the electronic gyromagnetic ratio, and an initial fluorescence intensity corresponding to the initial fluorescence signal;

[0286] The thermal drift compensation quantum module is configured to determine a thermal drift compensation amount according to an initial resonance frequency offset corresponding to the time-domain fluorescence intensity, a temperature disturbance value, and a temperature drift rate of a preset zero-field splitting coefficient.

[0287] Further, the processing module 203 comprises:

[0288] The dimensionality-raising processing sub-module is configured to perform dimensionality-raising processing on the optically detected magnetic resonance spectrum and the time-domain fluorescence intensity to obtain initial three-dimensional data;

[0289] The optimization processing submodule is configured to perform Tucker decomposition processing and alternating least squares optimization processing on the initial three-dimensional data to generate target three-dimensional data after noise reduction and a resonance frequency matrix of each spatial point and crystal direction.

[0290] Further, the construction module 204 includes:

[0291] The extraction submodule is configured to extract a first resonance frequency of each spatial point and crystal direction from the target three-dimensional data by using a fast Fourier transform method.

[0292] The correction quantum module is configured to determine a temperature drift correction amount of the zero-field splitting coefficient based on a reference value of the preset zero-field splitting coefficient, a temperature offset rate of the preset zero-field splitting coefficient, and a temperature drift suppression rate.

[0293] The offset quantum module is configured to calculate a difference between the first resonance frequency and the reference value of the preset zero-field splitting coefficient to generate a resonance frequency offset.

[0294] The change value submodule is configured to determine a fluorescence intensity change value based on a current measured fluorescence integral intensity corresponding to the time-domain fluorescence intensity and a baseline intensity without disturbance.

[0295] The joint submodule is configured to jointly construct a joint response equation by using the resonance frequency offset, the fluorescence intensity change value, the electron spin magnetic ratio, the preset temperature and frequency coupling coefficient, the preset fluorescence thermal quenching coefficient, the magnetic field, the temperature drift suppression rate, and a measurement noise covariance matrix.

[0296] Further, the decoupling processing module 205 includes:

[0297] The decoupling processing submodule is configured to perform decoupling processing on the magnetic field influencing factor and the temperature influencing factor in the joint response equation by using a Bayesian filtering algorithm to obtain a global magnetic field estimation value.

[0298] The vertical distance submodule is configured to determine a vertical distance between the probe and the conductor based on the current probe spatial coordinates and the conductor coordinates.

[0299] The calculation estimation value submodule is configured to calculate a current estimation value based on Ampere's law by using the global magnetic field estimation value, the vertical distance, and a preset vacuum permeability.

[0300] The curl operator submodule is configured to perform curl operation on the global magnetic field estimation value, the preset vacuum permeability, and a preset cylindrical coordinate system tangent unit vector to generate a current density distribution map.

[0301] The current resolution submodule is configured to determine a current resolution based on a magnetic field resolution corresponding to the global magnetic field estimation value, the preset vacuum permeability, and the vertical distance.

[0302] The embodiment of the present application provides a computer readable storage medium, which stores a computer program, and the computer program is executed to realize the NV color center magnetic field and current measurement method of any embodiment of the present application.

[0303] The embodiment of the present application provides a computer program product, which comprises a computer program stored on a non-transitory computer readable storage medium, and the computer program comprises program instructions, wherein when the program instructions are executed by a computer, the computer is caused to execute the NV color center magnetic field and current measurement method of any embodiment of the present application.

[0304] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the system, the device and the unit described above can refer to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0305] In several embodiments provided in the present application, it should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the units is only a logical function division, and actual implementation can have another division manner, for example, a plurality of units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can be electrical, mechanical or other forms.

[0306] The units described as separate components can or can not be physically separated, and the components shown as units can or can not be physical units, that is, can be located in one place, or can be distributed on a plurality of network units. According to actual needs, part or all of the units can be selected to achieve the purpose of the embodiment scheme.

[0307] In addition, each functional unit in each embodiment of the present application can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit.

[0308] The integrated unit, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, the technical solutions of the present application or the entire or part of the technical solutions that essentially contribute to the prior art can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a plurality of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in the various embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0309] The above-described embodiments are only used to illustrate the technical solutions of the present application, rather than limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements for some technical features; and these modifications or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method of NV color center magnetic field and current measurement, characterized by, The method comprises the following steps: acquiring an initial magnetic field signal containing environmental thermal noise, and constructing a quantum coherence enhancement pulse sequence using the initial magnetic field signal containing environmental thermal noise; controlling the spin state of an NV color center through the quantum coherence enhancement pulse sequence, determining an optical detection magnetic resonance spectrum and a time-domain fluorescence intensity; decomposing and denoising the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to generate target three-dimensional data; constructing a joint response equation by combining the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time-domain fluorescence intensity; decoupling the joint response equation to generate a global magnetic field estimate, and determining a current density distribution based on the global magnetic field estimate and a preset vacuum magnetic permeability.

2. The NV color center magnetic field and current measurement method of claim 1, wherein, The method comprises the following steps: controlling the spin state of an NV color center through the quantum coherence enhancement pulse sequence, and when the spin state of the NV color center is in the ground state, exciting the NV color center with a laser to generate an initial fluorescence signal; applying multiple frequency microwave pulses to the NV color center within a preset pulse interval time to obtain target microwave frequency points; acquiring an optical detection magnetic resonance spectrum within the control period of each target microwave frequency point; integrating the initial fluorescence signal of each spatial pixel point within the control period of the target microwave frequency point to obtain the total fluorescence integral intensity of each spatial pixel point; calculating the sum of the total fluorescence integral intensity of all spatial pixel points to generate a time-domain fluorescence intensity.

3. The method of NV color center magnetic field and current measurement of claim 2, wherein, The method further comprises the following steps: acquiring the preset pulse interval time, the pulse repetition number, and the intrinsic decoherence time when the quantum coherence enhancement pulse sequence controls the spin state of the NV color center; determining the effective decoherence time of the NV color center based on the preset pulse interval time, the pulse repetition number, and the intrinsic decoherence time; adjusting the initial acquisition sensitivity of the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity based on the effective decoherence time of the NV color center to generate a target acquisition sensitivity.

4. The method of NV color center magnetic field and current measurement of claim 3, wherein, The method further comprises the following steps: acquiring a measurement time, an electronic gyromagnetic ratio, a temperature disturbance value, and an angle between the magnetic field corresponding to the initial magnetic field signal containing environmental thermal noise and the axial direction of the NV color center; calculating a fluorescence response function using the effective decoherence time, the initial magnetic field signal containing environmental thermal noise, the measurement time, the angle, a preset Gaussian white noise, the electronic gyromagnetic ratio, and the initial fluorescence intensity corresponding to the initial fluorescence signal; determining a thermal drift compensation amount based on the initial resonance frequency offset corresponding to the time-domain fluorescence intensity, the temperature disturbance value, and the temperature offset rate of a preset zero-field splitting coefficient.

5. The method of NV color center magnetic field and current measurement according to claim 1, wherein, The method comprises the following steps: decomposing and denoising the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to generate target three-dimensional data; performing dimensionality elevation processing on the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to obtain initial three-dimensional data; The initial three-dimensional data is subjected to Tucker decomposition processing and alternating least squares optimization processing to generate target three-dimensional data after noise reduction and resonance frequency matrix of each spatial point and crystal direction.

6. The method of NV color center magnetic field and current measurement of claim 4, wherein, The resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time-domain fluorescence intensity are combined to construct a joint response equation, which includes: The first resonance frequency of each spatial point and crystal direction is extracted from the target three-dimensional data by using a fast Fourier transform method; Based on the reference value of the preset zero-field splitting coefficient, the temperature offset rate of the preset zero-field splitting coefficient, and the temperature drift suppression rate, the temperature drift correction amount of the zero-field splitting coefficient is determined; The difference between the first resonance frequency and the reference value of the preset zero-field splitting coefficient is calculated to generate a resonance frequency offset; The current measured fluorescence integral intensity corresponding to the time-domain fluorescence intensity and the baseline intensity without disturbance are used to determine the fluorescence intensity change value; The resonance frequency offset, the fluorescence intensity change value, the electronic gyromagnetic ratio, the preset temperature and frequency coupling coefficient, the preset fluorescence thermal quenching coefficient, the magnetic field, the temperature drift suppression rate, and the measurement noise covariance matrix are combined to construct a joint response equation.

7. The NV color center magnetic field and current measurement method of claim 1, wherein, The joint response equation is decoupled to generate a global magnetic field estimate, and based on the global magnetic field estimate and a preset vacuum permeability, a current density distribution map is determined, including: The magnetic field influencing factors and temperature influencing factors in the joint response equation are decoupled by using a Bayesian filtering algorithm to obtain a global magnetic field estimate; The vertical distance between the probe and the conductor is determined based on the current probe spatial coordinates and the conductor coordinates; Based on Ampere's law, the global magnetic field estimate, the vertical distance, and the preset vacuum permeability are used to calculate a current estimate; The global magnetic field estimate, the preset vacuum permeability, and the preset cylindrical coordinate system tangent unit vector are subjected to curl operation to generate a current density distribution map; The current resolution is determined based on the magnetic field resolution corresponding to the global magnetic field estimate, the preset vacuum permeability, and the vertical distance.

8. An NV color center magnetic field and current measurement system, characterized by, It includes: An acquisition module is configured to acquire an initial magnetic field signal containing environmental thermal noise, and construct a quantum coherence enhancement pulse sequence using the initial magnetic field signal containing environmental thermal noise; A control module is configured to control the spin state of the NV color center through the quantum coherence enhancement pulse sequence to determine the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity; A processing module is configured to perform decomposition and noise reduction processing on the optical detection magnetic resonance spectrum and the time-domain fluorescence intensity to generate target three-dimensional data; A construction module is configured to combine the resonance frequency offset corresponding to the resonance frequency of the target three-dimensional data and the fluorescence intensity change value corresponding to the time-domain fluorescence intensity to construct a joint response equation; A decoupling processing module is configured to decouple the joint response equation to generate a global magnetic field estimate, and determine a current density distribution map based on the global magnetic field estimate and a preset vacuum permeability.

9. A computer readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed to implement the NV color center magnetic field and current measurement method of any one of claims 1-7. The computer program is executed to implement the NV color center magnetic field and current measurement method of any one of claims 1-7.

10. A computer program product, characterised in that, The computer program product comprises a computer program stored on a non-transitory computer-readable storage medium, the computer program comprising program instructions, wherein the program instructions, when executed by a computer, cause the computer to perform the method of NV color center magnetic field and current measurement according to any one of claims 1-7.

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