A method for enhancing low-frequency sensitivity of a quantum sensor to magnetic fields

Abstract

This application discloses a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, relating to the field of quantum sensor technology. The method includes: during the detection of a longitudinal magnetic field by the target quantum sensor, adding a driving magnetic field to an atomic system in the transverse direction; the transverse direction being perpendicular to the longitudinal magnetic field to be measured; adding a feedback magnetic field to a y-direction coil on the atomic gas cell side to form a coil feedback-induced quantum coupling system; the y-direction being perpendicular to both the direction of the longitudinal magnetic field to be measured and the direction of the probe light; and adjusting the interaction between different atoms in the quantum coupling system under the quantum coupling system so that the frequency of the driving magnetic field differs from the rate of change of the longitudinal magnetic field to be measured by the gyromagnetic ratio by a set value, and then measuring the longitudinal magnetic field to be measured based on this. This application reduces the influence of low-frequency noise, improves the sensitivity of longitudinal low-frequency magnetic field measurement, and thus improves the accuracy of magnetic measurement.

Description

Technical Field

[0001] This application relates to the field of quantum sensor technology, and in particular to a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field. Background Technology

[0002] Quantum sensors are physical devices designed based on the laws of quantum mechanics. They achieve high-precision measurements through quantum effects such as quantum superposition and entanglement. Their sensing elements include structures such as laser-cooled atoms and diamond nitrogen-vacancy color centers, enabling them to detect subtle changes in physical quantities such as gravitational fields and magnetic fields. During the magnetic field detection process of quantum sensors, noise interference significantly impacts the detection sensitivity, necessitating a method to enhance the magnetic field detection sensitivity of quantum sensors. Summary of the Invention

[0003] The purpose of this application is to provide a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, reducing the influence of low-frequency noise, improving the sensitivity of longitudinal low-frequency magnetic field measurement, and thus improving the accuracy of magnetic measurement.

[0004] To achieve the above objectives, this application provides the following solution: This application provides a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, including: During the process of the target quantum sensor detecting the longitudinal magnetic field to be measured, a driving magnetic field is added to the atomic system in the transverse direction; the transverse direction is the direction perpendicular to the longitudinal magnetic field to be measured. A feedback magnetic field is added to the y-direction coil on the atomic gas cell side to form a quantum coupling system induced by coil feedback; the y-direction is the direction perpendicular to both the longitudinal magnetic field direction to be measured and the probe light direction. In the quantum coupling system, the interaction between different atoms in the quantum coupling system is adjusted so that the frequency of the driving magnetic field is greater than the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio. The longitudinal magnetic field to be measured is measured under the condition that the difference between the rate of change and the gyromagnetic ratio is greater than a set value.

[0005] According to the specific embodiments provided in this application, the following technical effects are disclosed: This application provides a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field. A feedback magnetic field is added to the y-direction coil on the atomic gas chamber side to form a coil feedback-induced quantum coupling system. Under the quantum coupling system, the interaction between different atoms in the quantum coupling system is adjusted so that the frequency of the driving magnetic field is greater than the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio, thus achieving a rate of change much greater than the gyromagnetic ratio. This enhances the sensitivity of the longitudinal low-frequency magnetic field measurement, reduces the influence of low-frequency noise, and improves the accuracy of magnetic field measurement. Attached Figure Description

[0006] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0007] Figure 1 This is a flowchart illustrating a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, provided as an embodiment of this application.

[0008] Figure 2 Provided for an embodiment of this application 129 Xe atoms and 131 A schematic diagram of a strongly coupled system of Xe atoms.

[0009] Figure 3 This is a schematic diagram of four free decay signals at different frequencies provided in an embodiment of this application.

[0010] Figure 4 This is a schematic diagram showing a comparison of sensitivity effects provided in an embodiment of this application.

[0011] Figure label: 1-Horizontal coil, 2-Lock-in amplifier, 3-Filter, 4-Photodetector. Detailed Implementation

[0012] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0013] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] In one exemplary embodiment, this application provides a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, such as... Figure 1 As shown, a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field includes steps 101-104.

[0015] Step 101: During the process of the target quantum sensor detecting the longitudinal magnetic field to be measured, a driving magnetic field is added to the atomic system in the transverse direction; the transverse direction is the direction perpendicular to the longitudinal magnetic field to be measured.

[0016] Step 102: Add a feedback magnetic field to the y-direction coil on the atomic gas chamber side to form a quantum coupling system induced by coil feedback; the y-direction is the direction perpendicular to both the longitudinal magnetic field direction to be measured and the probe light direction.

[0017] Step 103: In the quantum coupling system, adjust the interaction between different atoms in the quantum coupling system so that the frequency of the driving magnetic field is greater than the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio.

[0018] Step 104: Measure the longitudinal magnetic field to be measured under the condition that the difference between the rate of change and the gyromagnetic ratio is greater than a set value.

[0019] The frequency range of the low-frequency magnetic field is greater than or equal to 1 milliHz and less than or equal to 1 Hz.

[0020] This application modulates the interaction between different atoms in a quantum coupling system to make the frequency of the driving magnetic field greater than the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio. This results in a rate of change much greater than the gyromagnetic ratio, thereby enhancing the sensitivity of longitudinal low-frequency magnetic field measurement, reducing the influence of low-frequency noise, and thus improving the accuracy of magnetic field measurement.

[0021] In one exemplary embodiment, the target quantum sensor is a rubidium (Rb) atomic magnetometer, and the quantum coupling system is... 129 Xe atoms and 131 Xe atom strongly coupled system.

[0022] In one exemplary embodiment, the measurement formula is: ; in, Let be the precession frequency of the i-th type of Xe atom, and be different. Corresponding to 129 Xe atoms and 131 Xe atoms, such as the first type of Xe atom for 129 The precession frequency of Xe atoms, the second type of Xe atom for 131 The precession frequency of Xe atoms, Let be the gyromagnetic ratio corresponding to the i-th type of Xe atom. For bias magnetic field, The longitudinal magnetic field to be measured is [value]. Figure 2 In the z-axis direction, the z-axis is the direction that provides pump light to the pump. The plane formed by the x and y directions is the transverse direction. For the rotation of the system's physics.

[0023] The frequency of the driving magnetic field is expressed as: ; in, For the driving magnetic field of the i-th type of Xe atom, Let be the precession frequency of the i-th type of Xe atom. For quantum sensors The response signal relative to phase shift, Let be the relaxation rate of the i-th type of Xe atom.

[0024] by As a reference signal, by changing make Zero can make Continuous tracking .

[0025] When the response signal of the driving magnetic field is phase-shifted relative to the driving magnetic field When the frequency is zero, the relationship between the frequency of the driving magnetic field and the longitudinal magnetic field to be measured is expressed as: ; ; in, It is the gyromagnetic ratio. For bias magnetic field, The longitudinal magnetic field to be measured, For the rotation of the system's physics.

[0026] Currently, without using coil feedback, the quantum sensor achieves a magnetometry sensitivity of 50 fT / Hz for longitudinal magnetic fields at 0.01 Hz. 1 / 2 In most frequency ranges from 0.1 to 0.01 Hz, it is significantly better than 50 fT / Hz. 1 / 2 Poor; it doesn't achieve a performance better than 50 fT / Hz in the 0.1-0.01 Hz frequency range. 1 / 2 The required indicators.

[0027] To achieve higher sensitivity, while maintaining the current frequency noise level, it is necessary to improve... Make it much larger This improves the magnetic sensitivity of the longitudinal magnetic field B being measured. This is achieved through a quantum coupling system with feedback from a subsequent coil.

[0028] In one exemplary embodiment, such as Figure 2 As shown, step 102 specifically includes steps 201-202.

[0029] Step 201: Measure the Rb atoms 129 Xe atoms and 131 The nuclear spin signal of the Xe atom in the x-direction Frequency modulation is performed to obtain a modulated signal; the x-direction is the propagation direction of the probe light.

[0030] Step 202: Apply the modulation signal to the y-direction coil to form a feedback magnetic field, and form a feedback magnetic field through the feedback magnetic field. 129 Xe atoms and 131 A strongly coupled system of Xe atoms.

[0031] Step 201 specifically includes: measuring the Rb atoms... 129 Xe atoms and 131 The nuclear spin signal of the Xe atom in the x-direction is multiplied by the feedback coefficient and modulated by a trigonometric function to obtain the modulated signal.

[0032] Step 202 specifically includes: applying the modulation signal to the y-direction coil to form a feedback magnetic field. The feedback magnetic field is applied in the y-direction, forming 129 Xe atoms and 131 A strongly coupled system of Xe atoms; the y-direction is perpendicular to both the x-direction and the bias magnetic field.

[0033] The feedback magnetic field is represented as: ; in, This represents the feedback magnetic field, where k is the feedback coefficient. Represents the coupling coefficient. For modulation frequency, Indicates time.

[0034] Figure 2 middle, for 129 The nuclear spin signal of the Xe atom in the x-direction. for 129 The nuclear spin signal of the Xe atom in the y-direction. for 131 The nuclear spin signal of the Xe atom in the y-direction. for 131 The nuclear spin signal of the Xe atom in the x-direction. and They are respectively 129 Xe atoms and 131 The relaxation rate of Xe atoms.

[0035] In a strongly coupled system, the strong coupling coefficient is denoted by J, which is proportional to the feedback coefficient k. By adjusting k, J can be changed, thereby altering the strongly coupled state of the system.

[0036] In an exemplary embodiment, in step 103, before adjusting the interaction between different atoms in the quantum coupling system so that the frequency of the driving magnetic field differs from the rate of change of the longitudinal magnetic field to be measured from the gyromagnetic ratio by a set value, a method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field further includes: locking the phase shift of the response signal of the driving magnetic field relative to the driving magnetic field to zero.

[0037] In one exemplary embodiment, the frequency of the driving magnetic field is made such that the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio is greater than a set value, specifically including... 129 The frequency of the driving magnetic field of Xe atoms and the rate of change of the longitudinal magnetic field under test 129 The difference in the gyromagnetic ratio of Xe atoms is greater than a set value, and 131 The frequency of the driving magnetic field of Xe atoms and the rate of change of the longitudinal magnetic field under test 131 The difference in the gyromagnetic ratio of Xe atoms is greater than the set value.

[0038] Step 103 specifically includes: in the quantum coupling system, by adjusting the coupling coefficient and the modulation frequency, the frequency of the driving magnetic field is made such that the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio is greater than a set value.

[0039] In an exemplary embodiment, under the quantum coupling system, by adjusting the coupling coefficient and the modulation frequency, the frequency of the driving magnetic field is made such that the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio is greater than a set value, specifically including steps 301-302.

[0040] Step 301: In the quantum coupling system, before adjusting the interaction between different atoms in the quantum coupling system, if 129 Xe atoms and 131 The nuclear spin signal of the Xe atom has a non-zero transverse relaxation rate, which will produce four free-induction decay signals of different frequencies, such as... Figure 3 As shown, the four free induction decay (FID) signals are respectively , , and .

[0041] Step 302: Adjust the interaction between different atoms in the quantum coupling system so that the four free induction decay signals of different frequencies all have points with infinite slopes. Then the frequency of the driving magnetic field is satisfied that the difference between the rate of change of the longitudinal magnetic field to be tested and the gyromagnetic ratio is greater than the set value.

[0042] ; in, and Represent129 Xe atoms and 131 The transverse nuclear spin signal of the Xe atom and Corresponding to 129 Xe atoms and 131 The precession frequency of Xe atoms, detuning , , . The average relaxation rate, These are intermediate parameters.

[0043] In an exemplary embodiment, a circuit feedback system is constructed using components such as a lock-in amplifier 2 and a transverse coil 1. The x-direction and y-direction form a transverse plane. The signal measured by the photodetector 4 passes through a filter 3 and then enters the lock-in amplifier 2. The circuit feedback system converts the measured Xe atom precession signal into a feedback magnetic field and applies it back to the atomic system. This introduces an interaction between the two types of Xe atoms that can be precisely adjusted via the circuit, achieving strong coupling between them, i.e., forming... 129 Xe atoms and 131 A strongly coupled system of Xe atoms. By adjusting the strength of this interaction through a circuit feedback system, the system can be precisely tuned to the Exceptional Point (EP) region. In this region, the frequency of the driving magnetic field is much greater than the rate of change of the magnetic field under test than the gyromagnetic ratio, thus enabling the measurement of the longitudinal component of the magnetic field under test at a higher sensitivity than the gyromagnetic ratio.

[0044] This application also employs techniques such as frequency stabilization, power stabilization, and optimal phase to further reduce the impact of low-frequency noise in the system, improve the magnetic sensitivity of the longitudinal low-frequency magnetic field, and thus enhance the accuracy of magnetic field measurement.

[0045] like Figure 3 As shown, with the bias magnetic field The changes in these four frequencies will result in points with infinitely large slopes at specific locations, known as the EP point. At the EP point, if a frequency of [value missing] is applied laterally... The driving field will appear The phenomenon.

[0046] In this strongly coupled system, a frequency of [frequency] is applied laterally. The driving field, and the phase shift Locked at zero, we now have: , For intermediate parameters; ; in, and These are all intermediate parameters. , .

[0047] ,if only A value greater than 1 can enhance sensitivity.

[0048] At point EP, there is In the experiment, when Γ=0.1, J can reach 2π. 0.45, substituting the data yields... Considering this magnification factor, such as... Figure 4 Middle red line, Figure 4 The blue line represents the sensitivity of the quantum sensor before enhancement, and the red line represents the sensitivity after enhancement. For example... Figure 4 As shown, the sensitivity is less than 50 fT / Hz in the range of 0.1-0.01 Hz. 1 / 2 This enhances the longitudinal magnetic field sensitivity of the quantum sensor, achieving the predetermined performance requirements.

[0049] Based on the same inventive concept, this application also provides a quantum sensor for implementing the method described above for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field. The solution provided by this quantum sensor is similar to the solution described in the above method; therefore, the specific limitations in one or more quantum sensor embodiments provided below can be found in the above-described limitations of the method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field, and will not be repeated here.

[0050] In one exemplary embodiment, a quantum sensor is provided that applies the method described above for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field.

[0051] The quantum sensor is an Rb atomic magnetometer.

[0052] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0053] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for enhancing the low-frequency sensitivity of a quantum sensor in terms of magnetic field, characterized in that, include: During the process of the target quantum sensor detecting the longitudinal magnetic field to be measured, a driving magnetic field is added to the atomic system in the transverse direction; the transverse direction is the direction perpendicular to the longitudinal magnetic field to be measured. A feedback magnetic field is added to the y-direction coil on the atomic gas cell side to form a quantum coupling system induced by coil feedback; the y-direction is the direction perpendicular to both the longitudinal magnetic field direction to be measured and the probe light direction. In the quantum coupling system, the interaction between different atoms in the quantum coupling system is adjusted so that the frequency of the driving magnetic field is greater than the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio. The longitudinal magnetic field to be measured is measured under the condition that the difference between the rate of change and the gyromagnetic ratio is greater than a set value.

2. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 1, characterized in that, In the quantum coupling system, before adjusting the interaction between different atoms in the quantum coupling system so that the frequency of the driving magnetic field differs from the rate of change of the longitudinal magnetic field under test and the gyromagnetic ratio by a set value, the process further includes: The phase shift of the response signal of the driving magnetic field relative to the driving magnetic field is locked to zero.

3. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 1, characterized in that, The target quantum sensor is an Rb atomic magnetometer.

4. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 3, characterized in that, The quantum coupling system is 129 Xe atoms and 131 Xe atom strongly coupled system.

5. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 4, characterized in that, A feedback magnetic field is added to the y-direction coil on the atomic gas chamber side to form a coil feedback-induced quantum coupling system, specifically including: The measured 129 Xe atoms and 131 The nuclear spin signal of Xe atoms in the x-direction is frequency-modulated to obtain a modulation signal; the x-direction is the propagation direction of the probe light. The modulation signal is applied to the y-direction coil to form a feedback magnetic field, and the feedback magnetic field forms... 129 Xe atoms and 131 A strongly coupled system of Xe atoms.

6. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 5, characterized in that, The feedback magnetic field is represented as: ; in, Indicates the feedback magnetic field. Represents the coupling coefficient. For modulation frequency, Indicates time.

7. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 6, characterized in that, In the quantum coupling system, adjusting the interactions between different atoms in the quantum coupling system so that the frequency of the driving magnetic field differs from the rate of change of the longitudinal magnetic field under test and the gyromagnetic ratio by a set value, specifically includes: In the quantum coupling system, by adjusting the coupling coefficient and the modulation frequency, the frequency of the driving magnetic field is made such that the difference between the rate of change of the longitudinal magnetic field under test and the gyromagnetic ratio is greater than a set value.

8. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 7, characterized in that, In the quantum coupling system, by adjusting the coupling coefficient and the modulation frequency, the frequency of the driving magnetic field is made such that the difference between the rate of change of the longitudinal magnetic field under test and the gyromagnetic ratio is greater than a set value. Specifically, this includes: In the quantum coupling system, before adjusting the interactions between different atoms in the quantum coupling system, if 129 Xe atoms and 131 The nuclear spin signal of the Xe atom has a non-zero relaxation rate in the transverse direction, which will produce four free induction decay signals of different frequencies. By adjusting the coupling coefficient and the modulation frequency so that all four free induction attenuation signals of different frequencies have points with infinite slopes, the difference between the rate of change of the longitudinal magnetic field to be measured and the gyromagnetic ratio at the frequency of the driving magnetic field is greater than a set value.

9. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 1 or 2, characterized in that, The frequency of the driving magnetic field is expressed as: ； in, For the driving magnetic field of the i-th type of Xe atom, Let be the precession frequency of the i-th type of Xe atom. For quantum sensors The response signal relative to phase shift, Let be the relaxation rate of the i-th type of Xe atom.

10. The method for enhancing the low-frequency sensitivity of a quantum sensor's magnetic field according to claim 9, characterized in that, when When the frequency is zero, the relationship between the frequency of the driving magnetic field and the longitudinal magnetic field to be measured is expressed as: ； in, Let be the gyromagnetic ratio corresponding to the i-th type of Xe atom. For bias magnetic field, The longitudinal magnetic field to be measured, For the rotation of the system's physics.

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