Low-frequency electromagnetic field detection method based on Rydberg atoms and detection device thereof

Abstract

The invention discloses a method for detecting a low-frequency electromagnetic field based on Rydberg atoms. According to the method, on the basis that Rydberg atoms have a unique response mechanism for an external electric field and a magnetic field, the Rydberg atoms can convert modulation of a low-frequency electromagnetic field into relevant physical quantity changes of a detection light field under an appropriate quantum regulation and control means, and therefore precise measurement of the low-frequency electromagnetic field is achieved; according to the method, a stable local bias field is applied to the atomic gas chamber, so that the measurement process occurs in a linear conversion area, and the measurement accuracy and sensitivity are remarkably improved; furthermore, the gas chamber condition, the laser driving system, the detection light path and the specific frequency component extraction process are optimized, so that the signal-to-noise ratio of low-frequency electromagnetic field signal measurement can be remarkably improved, and the detection capability of the system is enhanced. According to the method and device, the design thought is clear, the structural complexity is low, good environmental adaptability is shown, and an efficient and reliable means is provided for low-frequency electromagnetic field measurement.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement, specifically a compact, high-precision, high-sensitivity electromagnetic field sensor designed based on the high sensitivity of Rydberg atoms to electromagnetic fields; and a method for achieving linear response between electromagnetic fields and detection light fields through quantum coherence effects, which is particularly suitable for the precise detection of low-frequency electromagnetic fields. Background Art

[0002] Electromagnetic field signals in the very low frequency (VLF) (3 kHz to 30 kHz), extra-low frequency (300 Hz to 3 kHz), ultra-low frequency (30 Hz to 300 Hz), and extremely low frequency (3 Hz to 30 Hz) ranges play a crucial role in long-distance communications and detection due to their ability to propagate over long distances in surface, underground, and underwater environments. To minimize the effects of environmental interference, detection technologies must meet higher sensitivity and accuracy requirements. Previously, detection methods based on the interaction of magnetic fields with the ground state of hot alkali metal atoms (from Sensitive magnetometry based on nonlinear magneto-optical rotation, authors D. Budker, D. Kimball, S. Rochester, V. Yashchuk, and M. Zolotorev) had stringent requirements for the ambient magnetic field, limiting their applicability in practical applications. Relatively speaking, since the electrons in Rydberg atoms are excited to high energy levels and have a very large principal quantum number (n), their electron orbital radius is large and their interaction with the magnetic field is close to the ideal Zeeman effect, so they are very sensitive to external electric and magnetic fields. The new low-frequency electromagnetic field detection method based on the atomic Rydberg state can exhibit characteristics that are completely different from the detection method based on the atomic ground state interaction. It is an effective supplement to current technologies such as spin exchange relaxation free atom magnetometer (SERF), and is expected to achieve technological breakthroughs in detecting weak signals in low-frequency fields, thereby demonstrating its unique advantages. Compared with the previous method of accurately measuring microwave signals by observing the AT splitting of the Rydberg EIT peak (cited from Microwave electrometry with Rydberg atoms in avapour cell using bright atomic resonances, authors Jonathon A. Sedlacek, Arne Schwettmann, Harald Kübler, Robert Löw, Tilman Pfau, James P. Shaffer), which requires the electric field signal to couple two Rydberg states during the measurement process, previous technologies mainly measured external fields in the 1 GHz to 1 THz RF, microwave, and terahertz frequency bands. In contrast, this method also effectively expands and supplements the frequency band of electromagnetic field measurements based on Rydberg atoms, thereby expanding the application scope of electromagnetic field measurement technology based on Rydberg atoms. Summary of the Invention

[0003] The purpose of the present invention is to propose a detection method and detection device based on Rydberg atoms for detecting low-frequency electromagnetic fields. The method utilizes the sensitive response mechanism of Rydberg atoms to external electric and magnetic fields, modulates the energy levels of Rydberg atoms through low-frequency electromagnetic fields, and based on the interaction between the detection light and the Rydberg atoms, uses quantum coherence effects to convert the information of the low-frequency electromagnetic field into observable physical quantities of the detection light field, thereby achieving precise measurement of the low-frequency electromagnetic field. During the measurement process, the method applies a stable local DC bias field and a low-frequency AC electric or magnetic field to be measured to the atomic gas chamber. The stable local DC bias field ensures that the change in the measured physical quantity and the field strength of the electric or magnetic field to be measured exhibit a strictly linear response characteristic, which is conducive to improving measurement accuracy and sensitivity. Applying a suitable DC bias electric field during low-frequency electric field measurements can also increase the Stark shift of the Rydberg state. Applying a suitable DC bias magnetic field during low-frequency magnetic field measurements can also increase the energy level shift caused by the Zeeman effect of the Rydberg state, effectively amplifying the system's response to the measured low-frequency electric and magnetic field signals, thereby improving measurement sensitivity. In actual measurements, by optimizing the design and parameters of the gas chamber, driving laser, detection optical path, and specific frequency component extraction process, the signal-to-noise ratio of the signal can be significantly improved in the low-frequency range, thereby enhancing the system's detection capability. In particular, in the phase detection scheme, the modulation of the Rydberg state by the AC electromagnetic field is converted into optical field information through resonant coupling. This process corresponds to the mathematical form of performing a unitary transformation, and the result is presented in the form of an integral. The phase change of the optical field is proportional to the ratio of the AC field amplitude to its frequency. This method can significantly amplify the detection of phase changes in the low-frequency range, making it particularly suitable for low-frequency field measurements.

[0004] The technical solution of the present invention is as follows: In one aspect, the present invention provides a method for detecting low-frequency electromagnetic fields based on Rydberg atoms, which comprises the following steps: Step 1. Use the first laser to emit a probe light, which is frequency-stabilized to the atomic ground state energy level. and excited state energy levels The resonant frequency of the atoms is near 0.01 and guided into the atomic gas chamber through the first dichroic mirror.

[0005] Step 2. Use a second laser to emit coupled light, which is frequency-stabilized to the atomic excited state energy level. and Rydberg levels The probe light is guided into the atomic gas chamber through the second dichroic mirror near the resonance frequency of the probe light. The optical path is adjusted so that the probe light and the coupled light coincide with each other in the opposite directions in the atomic gas chamber. By scanning the frequency of the coupled light, the spectral lines produced by the quantum coherence effect can be observed.

[0006] Step 3. Apply a DC bias field and the low-frequency AC electric field or magnetic field to be measured to the atomic gas chamber. The total electromagnetic field modulates the Rydberg state and converts it into light field intensity, phase or polarization information through quantum coherence effects. The stable local DC bias field ensures that the measurement process occurs within the linear conversion region, and the intensity, phase or polarization of the detection light field is detected.

[0007] Step 4. Set the reference signal frequency to the same frequency as the AC field to be measured, perform a specific frequency component extraction process on the detected signal, and calculate the magnitude of the low-frequency electromagnetic field to be measured based on the specific frequency component extraction output.

[0008] Preferably, the atomic gas chamber is processed so as to avoid the electric field shielding effect caused by atomic adsorption when the low-frequency AC electric field to be measured is applied.

[0009] On the other hand, the present invention also provides a low-frequency electromagnetic field detection device based on Rydberg atoms, which is characterized by comprising: a first laser, configured to output a detection light; a second laser for outputting coupled light; A beam splitting system for splitting the probe light and / or the coupled light; Dual-wavelength frequency stabilization module, used to stabilize the detection light frequency at the atomic ground state energy level and atomic excited state energy levels The coupled light is fixed at the atomic excited state energy level within the resonance frequency range. and Rydberg levels within the resonant frequency range; Atomic gas cell, used to provide various atoms that can be excited to Rydberg states for low-frequency electromagnetic field detection; The guiding optical path system is used to make the detection light and the coupling light coincide with each other in the opposite direction in the atomic gas chamber, thereby generating a quantum coherence effect; A DC field generator is used to provide a DC bias field for the atomic gas chamber, so that the atoms reach the measurement working range of low-frequency electric or magnetic fields; The specific frequency component extraction system is used to perform intensity detection, phase detection or polarization detection on the detection light before and after entering the atomic gas chamber, and calculate the magnitude of the low-frequency electromagnetic field to be measured.

[0010] The laser drive system needs to be frequency-stabilized to improve the coherence of quantum optical effects such as Rydberg EIT and Autler-Townes generated by the interaction between the two laser beams and atoms, which is beneficial to improving the signal-to-noise ratio of the final detection signal; the atomic gas chamber is processed to reduce the electric field shielding effect caused by atomic adsorption, and the detection optical path can adopt intensity measurement, phase measurement or polarization measurement schemes. In particular, the phase detection scheme requires the detection light before and after entering the atomic gas chamber to be simultaneously input into a specific frequency component extraction system. The phase change of the light field is proportional to the ratio of the AC field amplitude to its frequency. It can significantly amplify the detection of phase changes in the low-frequency range, thereby further improving the sensitivity of the system.

[0011] Compared with the prior art, the present invention has the following beneficial effects: 1) The treated atomic gas chamber can reduce the electric field shielding effect caused by atomic adsorption, ensuring the effectiveness of low-frequency electric field measurements; 2) Applying a DC bias field places the measurement process within the linear response region, which helps improve measurement accuracy and sensitivity. In addition, it also helps amplify the modulation of the Rydberg state by the AC field during measurement, thereby improving the sensitivity of the system. 3) Rich detection methods. By adopting different quantum control methods, the electromagnetic field signal to be measured can be converted into the intensity change signal, phase change signal or polarization change signal of the detection light. Therefore, various detection methods such as intensity detection, phase detection and polarization detection can be adopted. The diversified detection methods improve the environmental adaptability of the system. 4) In particular, for the phase detection scheme, since the phase change of the light field is proportional to the ratio of the AC field amplitude to its frequency, it can be seen that the detection of phase changes can be significantly amplified in the low-frequency range, thereby further improving the sensitivity of the system, which is particularly suitable for the precise measurement of low-frequency electromagnetic fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a flow chart of a method for detecting low-frequency electromagnetic fields based on Rydberg atoms in the present invention. Figure 2 This is a schematic diagram of the structure of a device for detecting low-frequency electric fields based on Rydberg atoms in the present invention. Figure 3 This is a schematic diagram of the energy levels of the Rydberg atom probe low-frequency electric field in the present invention. Figure 4 This is a schematic diagram of the structure of a low-frequency magnetic field device based on Rydberg atom detection in the present invention. Figure 5 This is a schematic diagram of the energy levels of the Rydberg atom probe low-frequency magnetic field in the present invention. Figure 6 This is a schematic diagram of the working point of the present invention based on the Rydberg atom detection low-frequency magnetic field DETAILED DESCRIPTION The present invention will be further described below with reference to the embodiments and drawings, but the scope of protection of the present invention should not be limited thereto.

[0013] Take the example of using alkali metal or alkaline earth metal atoms and exciting them to Rydberg states and performing low-frequency electromagnetic field detection: See Figure 2 , Figure 2 The present invention is a schematic diagram of the structure of a device for detecting low-frequency electric fields based on Rydberg atoms. As shown in the figure, the low-frequency electric field detection device of the present invention includes a first laser 2-1, a second laser 2-2, a first beam splitter prism 2-3, a second beam splitter prism 2-4, a dual-wavelength ultra-stable cavity 2-5, a first dichroic mirror 2-6, a second dichroic mirror 2-7, an atomic gas chamber 2-8, a parallel capacitor plate 2-9, a low-frequency electric field to be measured 2-10, a first beam splitter 2-11, a reflector 2-12, a reference light 2-13, and a specific frequency component extraction system 2-14.

[0014] Frequency locking based on the dual-wavelength ultrastable cavity can effectively reduce the linewidth of the laser used, improve the coherence of quantum optical effects such as Rydberg EIT and Autler-Townes generated by the interaction between the two laser beams and atoms, and is conducive to improving the signal-to-noise ratio of the final detection signal.

[0015] The atomic gas chamber 2-8 uses sapphire glass as the gas chamber material to reduce the electric field shielding effect caused by atomic adsorption on the inner wall of the gas chamber, thereby ensuring the effectiveness of low-frequency electric field measurement; in the future, the electric field shielding effect caused by the gas chamber itself can be further reduced by coating or upgrading the material.

[0016] The parallel capacitor plates 2-9 are arranged at both ends of the atomic gas chamber 2-8 to provide a DC bias electric field to increase the measurement sensitivity of the AC electric field. The parallel capacitor plates should provide a spatially uniform DC bias electric field within the atomic gas chamber 2-8 without blocking the light path. The parallel capacitor plates will not hinder the application of the AC low-frequency electric field, and the design of this device naturally has the ability to detect vector electric fields.

[0017] See also Figure 3 , Figure 3 This is a schematic diagram of the energy levels of the Rydberg atom probe low-frequency electric field in the present invention, which is applicable to a variety of atoms including typical alkali metal atoms such as Rb, Cs, K, and Na, and typical alkaline earth metal atoms such as Yb and Sr. As shown in the figure, the Rabi frequency is The probe light 3-1 excites the atom from the ground state 3-3 to excited state 3-4, the Rabbi frequency is The coupled light 3-2 excites the atom from the excited state 3-4 to a specific Rydberg state 3-5. In addition, the DC bias electric field and the low-frequency electric field to be measured add an AC Stark shift correction to the Rydberg state energy level.

[0018] Further integration Figure 1 The schematic flow chart of the method for detecting low-frequency electromagnetic fields based on Rydberg atoms of the present invention can be given in detail in Example 1, using 87 Take the Rb atom as an example, the atomic transition frequency corresponding to the detection light 3-1 is 384.2346 THz, and the atomic transition frequency corresponding to the coupling light 3-2 is 312.3886 THz, which excites it to The method for detecting a Rydberg state and a low-frequency electric field comprises the following steps: Step 1: The first laser 2-1 uses a 780 nm laser as the probe light, which is split by the first beam splitter prism 2-3. One beam is input into the ultrastable cavity 2-5 for frequency stabilization, and the frequency is fixed to the atomic ground state energy level. and excited state energy levels The resonant frequency of the laser is 384.2346 THz. The second laser 2-2 uses a 480 nm laser as the coupling light, which is split by the second beam splitter prism 2-4. One beam is input into the ultrastable cavity 2-5 for frequency stabilization, and the frequency is fixed to the atomic excited state energy level. Rydberg levels The resonant frequency of the two laser beams is 312.3886 THz, which ensures the high coherence of the Rydberg EIT effect generated by the interaction between the two laser beams and the atoms.

[0019] Step 2: The detection light is transmitted through the first dichroic mirror 2-6 into the atomic gas chamber 2-8 and is transmitted by the second dichroic mirror 2-7; the coupling light is reflected by the second dichroic mirror 2-7 into the atomic gas chamber 2-8 and is reflected by the first dichroic mirror 2-6; the optical path is adjusted so that the detection light and the coupling light overlap in the opposite collinear direction in the atomic gas chamber 2-8, and the atoms can be excited to At the Rydberg energy level; by scanning the coupled light frequency, the Rydberg EIT spectrum line can be observed.

[0020] Step 3: Apply a DC bias electric field and a low-frequency electric field to be measured to the atomic gas chamber 2-8. The total electric field can be described as ,in is the DC bias electric field, is the amplitude of the low-frequency electric field to be measured, and They correspond to the frequency and phase of the low-frequency electric field to be measured. The square of the total electric field amplitude is: Selecting a suitable DC bias electric field can improve the measurement sensitivity of low-frequency electric field signals. Similarly, selecting a suitable DC bias magnetic field can improve the measurement sensitivity of low-frequency magnetic field signals. Common Stark effects include first-order and second-order Stark effects. For the first-order Stark effect, changing the DC bias electric field can select the slope of the linear correction relationship between the total electric field and the Rydberg energy level; for the second-order Stark effect, the correction of the total electric field to the Rydberg energy level is ,in The response of Rydberg atoms to electric fields is characterized. The DC bias electric field and the low-frequency electric field to be measured modulate the Rydberg state according to the frequency of the electric field to be measured. The modulation intensity is proportional to .

[0021] Under the influence of the common first-order or second-order Stark effect, the Hamiltonian is in the form of in, Indicates the modulation intensity of the low-frequency electric field to be measured on the Rydberg state; in low-frequency electric field measurement, Equal to the low-frequency electric field frequency ; To detect the optical Rabi frequency, is the coupled light Rabi frequency, To detect the optical detuning frequency; is the detuning frequency of the coupled light; Then do the following unitary transformation , in , The transformed Hamiltonian is , It can be seen that the detection light will be modulated with the same frequency as the low-frequency electric field to be measured during its interaction with the atoms, which is equivalent to the low-frequency electric field signal to be measured being converted into a specific change in the detection light.

[0022] Step 4 extracts the information carried by the probe light. For example, this can be done using reference light 2-13. While extracting the specific frequency component of the detected signal, the extraction frequency is set to the same as the frequency of the low-frequency electric field to be measured. The magnitude of the low-frequency electric field to be measured is then calculated based on the output of the specific frequency component extraction system 2-14. This method emphasizes the sensitivity of phase measurement, providing a more sensitive measurement method than EIT signal intensity changes.

[0023] See Figure 4 , Figure 4 This is a structural schematic diagram of a low-frequency magnetic field detection device based on Rydberg atoms of the present invention. As shown in the figure, the low-frequency magnetic field detection device of the present invention includes a first laser 4-1, a second laser 4-2, a first beam splitter prism 4-3, a second beam splitter prism 4-4, a dual-wavelength ultra-stable cavity 4-5, a first dichroic mirror 4-6, a second dichroic mirror 4-7, an atomic gas chamber 4-8, a Lee-Whiting magnetic field coil 4-9, a low-frequency electric field to be measured 4-10, a first beam splitter 4-11, a reflector 4-12, a detection light reference 4-13, and a specific frequency component extraction system 4-14.

[0024] The Lee-Whiting magnetic field coil 4-9 provides a DC bias magnetic field for the atomic gas chamber 4-8 so that the atoms reach a suitable low-frequency magnetic field measurement working range. The spacing between each coil can be adjusted to provide a spatially uniform DC bias magnetic field within the atomic gas chamber 4-8. The Lee-Whiting magnetic field coil will not hinder the application of an AC low-frequency magnetic field.

[0025] See also Figure 5 , Figure 5 This is a schematic diagram of the energy levels of the Rydberg atom probe low-frequency magnetic field in the present invention. As shown in the figure, the Rabi frequency is The probe light 5-1 excites the atom from the ground state 5-3 to excited state 5-4, the Rabbi frequency is The coupled light 5-2 excites the atom from the excited state 5-4 to Rydberg state 5-5. In addition, the DC bias magnetic field and the low-frequency magnetic field to be measured all add Zeeman shift corrections to the ground state, excited state and Rydberg state energy levels.

[0026] See also Figure 6 , Figure 6 This is a schematic diagram of the working point of the low-frequency magnetic field based on Rydberg atom detection in the present invention, which explains the change of the Zeeman shift of the atomic state under different DC bias magnetic field conditions and its applicability to low-frequency magnetic field detection. As shown in the figure, under weak magnetic field conditions 6-1, the good quantum number of the ground state and excited state is the total angular momentum , the Zeeman shift varies linearly with the magnetic field, while the Rydberg state varies linearly with the total angular momentum. For good quantum numbers, the total angular momentum of the electron gradually transitions to For good quantum numbers, it shows nonlinear changes with magnetic field, so it is not suitable as a detection area for low-frequency magnetic fields; if a large DC bias magnetic field of 6-3 is applied, the ground state and excited state may change from the total angular momentum For good quantum numbers, the total angular momentum of the electron gradually transitions to The good quantum number changes nonlinearly with the magnetic field due to the transformation of the good quantum number. When the DC bias magnetic field size is selected appropriately, 6-2 (for example, 10 Gauss), the good quantum number of the ground state and the excited state is still the total angular momentum. , the Zeeman shift varies linearly with the magnetic field. For the Rydberg state, the total angular momentum of the electron is It is a good quantum number, so it also shows a linear change relationship with the magnetic field, which is suitable as a low-frequency magnetic field detection working point.

[0027] Further integration Figure 1 The schematic flow chart of the method for detecting low-frequency electromagnetic fields based on Rydberg atoms of the present invention can be given in detail in Example 2, using 87 Rb atoms and excite them to The method for detecting a Rydberg state and a low-frequency magnetic field comprises the following steps: Step 1: The first laser 4-1 uses a 780 nm laser as the probe light, which is split by the first beam splitter 4-3. One beam is input into the ultrastable cavity 4-5 for frequency stabilization, and the frequency is fixed to the atomic ground state energy level. and excited state energy levels The resonant frequency of the laser is 384.2346 THz. The second laser 4-2 uses a 480 nm laser as the coupling light, which is split by the second beam splitter prism 4-4. One beam is input into the ultrastable cavity 4-5 for frequency stabilization, and the frequency is fixed to the atomic excited state energy level. and Rydberg levels The resonant frequency of the two laser beams is 312.3886 THz, which ensures the high coherence of the Rydberg EIT effect generated by the interaction between the two laser beams and the atoms.

[0028] Step 2: The detection light is transmitted through the first dichroic mirror 4-6 into the atomic gas chamber 4-8 and is transmitted by the second dichroic mirror 4-7; the coupling light is reflected by the second dichroic mirror 4-7 into the atomic gas chamber 4-8 and is reflected by the first dichroic mirror 4-6; the optical path is adjusted so that the detection light and the coupling light overlap in the opposite collinear direction in the atomic gas chamber 4-8, and the atoms can be excited to At the Rydberg energy level; by scanning the coupled light frequency, the Rydberg EIT spectrum line can be observed.

[0029] Step 3: Apply a DC bias magnetic field and a low-frequency magnetic field to be measured to the atomic gas chambers 4-8. The total magnetic field can be described as ,in is the DC bias magnetic field, is the amplitude of the low-frequency magnetic field to be measured, and They correspond to the frequency and phase of the low-frequency magnetic field to be measured, and the Zeeman correction of the magnetic field to the ground state is: , The Zeeman correction for the excited state is , The Zeeman correction for the Rydberg state is .

[0030] in 、 、 denote the Lande factors of the ground excited state and the Rydberg state, respectively. is the Bohr magneton, 、 、 denote the magnetic quantum numbers of the ground state, excited state and Rydberg state, respectively.

[0031] For a Hamiltonian of the form The system is transformed as follows in, 、 and Respectively represent the modulation intensity of the low-frequency magnetic field to be measured on the ground state, excited state and Rydberg state; in the low-frequency magnetic field measurement, Equal to the low-frequency magnetic field frequency ; To detect the optical Rabi frequency, is the coupled light Rabi frequency, To detect the optical detuning frequency; is the detuning frequency of the coupled light; , in The transformed Hamiltonian is , It can be seen that the detection light will be modulated with the same frequency as the low-frequency magnetic field to be measured during its interaction with the atoms, which is equivalent to the low-frequency magnetic field signal to be measured being converted into a specific change in the detection light.

[0032] Step 4 extracts the information carried by the probe light. For example, this can be done using reference light 4-13. While extracting specific frequency components from the detected signal, the extraction frequency is set to the same as the frequency of the low-frequency magnetic field to be measured. The magnitude of the low-frequency magnetic field to be measured is then calculated based on the output of the specific frequency component extraction system 4-14. This method emphasizes the sensitivity of phase measurement, providing a more sensitive measurement method than EIT signal intensity changes.

[0033] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A low-frequency electromagnetic field detection method based on Rydberg atoms, characterized in that: include: Step 1. Provide probe light and coupling light to the atomic gas cell, wherein the frequency of the probe light is fixed at the atomic ground state energy level. and atomic excited state energy levels The frequency of the coupled light is fixed to the atomic excited state energy level within the resonance frequency range. and Rydberg levels The detection light and the coupling light overlap in opposite directions and collinearly in the atomic gas chamber to excite the atoms to the Rydberg state and form a quantum coherence effect; Step 2. Applying a steady local DC bias field and a low-frequency AC electric / magnetic field to be measured to the atomic gas chamber, so that the energy level of the Rydberg state is modulated by the electric / magnetic field under the influence of the Stark effect / Zeeman effect; Step 3. Convert the energy level modulation into a change in the physical quantity of the probe light through quantum coherence effects such as electromagnetic induced transparency (EIT) and Autler-Townes splitting. The physical quantity includes light field intensity, phase, or polarization information. Step 4. Extract the specific frequency component of the detection light that has the same frequency as the low-frequency electromagnetic field to be measured, and calculate the field intensity of the low-frequency electric / magnetic field to be measured. When using a Rydberg atomic cell to measure low-frequency electric fields, a DC bias electric field is applied to the atomic cell. And the low-frequency electric field to be measured , then the total electric field , the formula is as follows; ， Where, and are the frequency and phase of the low-frequency electric field to be measured, respectively, and Re represents the real part operation of the electric field; The square of the amplitude of the total electric field is: By adjusting the DC bias electric field , optimize the linear or nonlinear correction relationship of the total electric field to the Rydberg energy level to improve the measurement sensitivity of the low-frequency electric field signal. For the first-order Stark effect, changing the DC bias electric field can select the slope of the linear correction relationship of the total electric field to the Rydberg energy level; for the second-order Stark effect, the correction of the total electric field to the Rydberg energy level is ,in, The response of Rydberg atoms to electric fields is characterized. The DC bias electric field and the low-frequency electric field to be measured modulate the Rydberg state according to the frequency of the electric field to be measured. The modulation intensity is proportional to Alternatively, when using a Rydberg atomic cell to measure low-frequency magnetic fields, a DC bias magnetic field is applied to the atomic cell. And the low-frequency magnetic field to be measured , then the total magnetic field , the formula is as follows; Where, and are the frequency and phase of the low-frequency magnetic field to be measured; Re represents the real part operation of the magnetic field; The influence of magnetic field on the ground state of atoms through the Zeeman effect , excited state and Rydberg states Generate energy level correction, the formula is as follows: Where, 、 、 denote the Lande factors of the ground excited state and the Rydberg state, respectively. is the Bohr magneton, 、 、 denote the magnetic quantum numbers of the ground excited state and the Rydberg state, respectively; Under the influence of the Stark effect or the Zeeman effect, the Hamiltonian is constructed as follows: Where, 、 and Respectively represent the modulation intensity of the low-frequency electric field or magnetic field to be measured on the ground state, excited state and Rydberg state. When measuring the low-frequency electric field, and are all zero, and To detect optical detuning, is the coupled light detuning, To detect the optical Rabi frequency, is the coupled light Rabi frequency, ; The Hamiltonian is subjected to a unitary transformation to obtain a transformed Hamiltonian, which is as follows: ； A specific frequency component extraction system is used to perform intensity detection, phase detection or polarization detection on the detection light before and after entering the atomic gas chamber, and the magnitude of the low-frequency electromagnetic field to be measured is calculated.

2. The low-frequency electromagnetic field detection method based on Rydberg atoms according to claim 1, characterized in that: The local DC bias field is a DC bias electric field or a DC bias magnetic field; When detecting a low-frequency electric field, the DC bias electric field is used to increase the linear response of the Stark shift of the Rydberg state; When detecting a low-frequency magnetic field, the DC bias magnetic field is used to increase the Zeeman shift linear response of the Rydberg state.

3. The low-frequency electromagnetic field detection method based on Rydberg atoms according to claim 2, characterized in that: When detecting low-frequency electric fields, a steady local DC bias electric field is applied to the atomic gas cell. and the low-frequency AC electric field to be measured , adjust the DC bias electric field through the first-order or second-order Stark effect , so that the total electric field ,in, is the amplitude of the low-frequency electric field to be measured, and are the frequency and phase of the low-frequency electric field to be measured, and Re represents the real part operation of the electric field.

4. The low-frequency electromagnetic field detection method based on Rydberg atoms according to claim 2, characterized in that: When detecting low-frequency magnetic fields, a steady local DC bias magnetic field is applied to the atomic gas chamber. and the low-frequency AC magnetic field to be measured, the total magnetic field ,in, , and are the amplitude, frequency and phase of the low-frequency magnetic field to be measured, and Re represents the real part of the magnetic field. , excited state and Rydberg states Generate energy level correction, the formula is as follows: Where, 、 、 denote the Lande factors of the ground excited state and the Rydberg state, respectively. is the Bohr magneton, 、 、 denote the magnetic quantum numbers of the ground state, excited state and Rydberg state, respectively.

5. The low-frequency electromagnetic field detection method based on Rydberg atoms according to claim 3 or 4, characterized in that: Under the influence of the Stark effect or the Zeeman effect, the Hamiltonian is constructed as follows: Where, 、 and Respectively represent the modulation intensity of the low-frequency electric field or magnetic field to be measured on the ground state, excited state and Rydberg state. When measuring the low-frequency electric field, and are all zero, and ; The Hamiltonian is subjected to a unitary transformation to obtain a transformed Hamiltonian, which is as follows:

6. A low-frequency electromagnetic field detection device based on Rydberg atoms, characterized in that: include: The first laser and the second laser are used to output detection light and coupling light respectively; Dual-wavelength frequency stabilization module, used to stabilize the detection light frequency at the atomic ground state energy level and atomic excited state energy levels The coupled light is fixed at the atomic excited state energy level within the resonant frequency range. and Rydberg levels within the resonant frequency range; An atomic gas cell containing atoms that can be excited to Rydberg states, and the gas cell material or surface treatment is used to reduce electric field shielding effects; An optical path guiding system, configured to cause the detection light and the coupling light to propagate in opposite directions and collinearly within the atomic gas chamber to generate a quantum coherence effect; The DC field generator is used to apply a steady DC bias electric field or magnetic field; the signal detection module is used to extract the intensity, phase or polarization changes of the detection light and calculate the low-frequency electromagnetic / field parameters to be measured.

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