Method for measuring radio frequency electric field based on high orbital angular momentum quantum state

Abstract

The invention discloses a method for measuring a radio frequency electric field based on a high orbital angular momentum quantum state, and the method comprises the steps: firstly, detecting the radio frequency electric field through the high orbital angular momentum quantum state of Rydberg atoms, enabling the Rydberg atoms to continuously measure the radio frequency electric field in a certain frequency range through an external magnetic field or electric field regulation method, and enabling the Rydberg atoms to continuously measure the radio frequency electric field in a certain frequency range; and the frequency range of the Rydberg atom-based electric field meter for measuring the radio frequency electric field is expanded. According to the method, measurement is carried out in a resonance mode, resonance frequency points are matched, an electric field and atoms have stronger coupling at the resonance frequency points, and more sensitive measurement can be realized through electric dipole transition; besides, a mode of introducing an external field for regulation and control is proposed, Zeeman splitting of atomic energy levels can be precisely regulated and controlled by changing the size of an external magnetic field, or the external electric field is utilized for regulating and controlling the overall movement of Rydberg energy levels, so that the energy level interval is matched with the field intensity frequency to be detected, and the frequency range of the detectable electric field is further expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency electric field measurement, and in particular relates to a method for measuring radio frequency electric field based on high orbital angular momentum quantum state. Background Art

[0002] Rydberg atoms are very sensitive to external electric fields because of their large transition dipole moment and large electric susceptibility, so they can be used to measure electric fields. The interval between adjacent Rydberg energy levels covers the frequency range of MHz to THz. By adjusting the laser wavelength, different Rydberg energy levels can be prepared, thereby achieving ultra-wideband electric field measurement. The sensing process of Rydberg atoms, such as excitation and readout, is all-optical, so electromagnetic interference can be effectively avoided. Since the electric field measurement of Rydberg atoms has many excellent characteristics, it is expected to provide new solutions in measurement, perception, communication and other applications.

[0003] Based on the superheterodyne measurement method of Rydberg atoms, ~μV / cm / Hz can be achieved in the GHz band 1 / 2 The measurement sensitivity is close to ~400pV / cm for the minimum detectable strong field. However, when using Rydberg atoms to measure low-frequency radio frequency electric fields below GHz, especially ultrashort wave (30-300MHz) electric fields, since the transition frequency in this frequency band is quite different from the spacing of similar Rydberg energy levels, the non-resonant AC Stark effect is often used to complete the current measurement. Compared with the resonant measurement of the AC Stark effect, the non-resonant measurement has a lower measurement sensitivity. This is because the usual Rydberg atom measurement method, taking the most common 852nm+509nm two-photon excitation in cesium atoms as an example, first uses a laser with a wavelength of around 852nm to excite the 6S 1 / 2 The ground state atom is excited to the intermediate state 6P 3 / 2 , and then use a laser with a wavelength of about 509nm to excite the atoms in the intermediate state to the Rydberg state. Due to the limitation of the transition selection rule, the Rydberg initial state energy level of the above excitation scheme can only be S or D state. At the same time, due to some limitations of laser energy and experiments, the principal quantum number n of the Rydberg state cannot be too large, usually not exceeding 120. In this way, the adjacent energy level intervals of the S and D states with n<120 cannot cover the frequency range of the RF electric field. If the RF electric field frequency band is to be measured, the principal quantum number of the S state must be n>220, and the principal quantum number of the D state must be n>130, which poses huge challenges in the experimental operation process. Summary of the invention

[0004] Technical problem to be solved by the present invention: Overcoming the deficiencies of the prior art, providing a method for measuring radio frequency electric fields based on high orbital angular momentum quantum states. First, use the high orbital angular momentum quantum states of Rydberg atoms to detect radio frequency electric fields, and through methods of external magnetic field or electric field regulation, enable Rydberg atoms to continuously measure radio frequency electric fields within a certain frequency range, expanding the frequency range of radio frequency electric field measurement by electric field meters based on Rydberg atoms.

[0005] To solve the above technical problems, the present invention discloses a method for measuring radio frequency electric fields based on high orbital angular momentum quantum states, including:

[0006] Prepare a matching high angular momentum quantum state according to the specific frequency point of the measured radio frequency electric field;

[0007] At the resonance frequency point, based on the prepared matching high angular momentum quantum state, use the EIT-AT splitting measurement method or the superheterodyne measurement method based on Rydberg atoms to measure the intensity of the incident radio frequency electric field;

[0008] In addition to measuring at the resonance frequency point, adopt an external field regulation method to achieve continuously tunable radio frequency electric field frequency measurement.

[0009] In the above method for measuring radio frequency electric fields based on high orbital angular momentum quantum states, the high angular momentum quantum state refers to a quantum state with an orbital angular momentum quantum number L≥3.

[0010] In the above method for measuring radio frequency electric fields based on high orbital angular momentum quantum states, use the three-photon excitation method or the two-photon excitation combined with microwave excitation method to prepare a matching high angular momentum quantum state.

[0011] In the above method for measuring radio frequency electric fields based on high orbital angular momentum quantum states, the steps of using the three-photon excitation method to prepare a matching high angular momentum quantum state are as follows:

[0012] Use a laser with a wavelength of 852nm to excite the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ;

[0013] Use a laser with a wavelength of 917nm to excite the atom from the first intermediate state 6P 3 / 2 to the second intermediate state 6D 5 / 2 ;

[0014] Use a laser with a wavelength of 1141nm to excite the atom from the second intermediate state 6D 5 / 2 to the first Rydberg state nF 7 / 2 ; Thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state, the second Rydberg state nG 7 / 2, realizing the perception of the radio frequency electric field.

[0015] In the above method for measuring the radio frequency electric field based on the high orbital angular momentum quantum state, the steps of preparing a matched high angular momentum quantum state by using two-photon excitation in cooperation with microwave excitation are as follows:

[0016] Using a laser with a wavelength of 852 nm to excite the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ;

[0017] Using a laser with a wavelength of 509 nm to excite the atom from the first intermediate state 6P 3 / 2 to the third Rydberg state nD 5 / 2 ;

[0018] Using a microwave with a frequency of GHz to excite the atom from the third Rydberg state nD 5 / 2 to the first Rydberg state nF 7 / 2 ; Thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state, the second Rydberg state nG 7 / 2 , realizing the perception of the radio frequency electric field.

[0019] In the above method for measuring the radio frequency electric field based on the high orbital angular momentum quantum state, the external field regulation methods include: applying an external electric field and an external magnetic field.

[0020] In the above method for measuring the radio frequency electric field based on the high orbital angular momentum quantum state, in the presence of an external electric field, by changing the magnitude of the applied electric field, the displacement of the Rydberg energy level is adjusted; where, Δf = αE 2 / 2, Δf represents the energy level shift interval, α represents the electric polarizability of the Rydberg energy level, and E represents the magnitude of the applied electric field.

[0021] In the above method for measuring the radio frequency electric field based on the high orbital angular momentum quantum state, in the presence of an external magnetic field, the Rydberg energy level undergoes Zeeman splitting. Utilizing the Zeeman effect, by changing the magnitude of the applied magnetic field, the magnetic sub-levels of the Rydberg energy level are adjusted; where, ΔE = h·ΔF = μ·Bcosθ, ΔE represents the energy difference of the energy level transition, h represents Planck's constant, ΔF represents the frequency interval between energy levels, μ represents the total magnetic moment of the atom, B represents the magnetic induction intensity, and θ represents the angle between the total magnetic moment and the magnetic field direction.

[0022] The present invention has the following advantages:

[0023] (1) The present invention discloses a method for measuring the radio frequency electric field based on the high orbital angular momentum quantum state. By measuring the radio frequency electric field through the resonance transition with the high orbital angular momentum quantum state, compared with the non-resonance measurement method of the AC Stark effect, the atom has a stronger interaction with the electric field, and the measurement sensitivity will be higher.

[0024] (2) The present invention discloses a method for measuring radio frequency electric fields based on high orbital angular momentum quantum states. By introducing an external electric field or magnetic field, non-resonant frequency points can also achieve resonant measurement under the induction of the external field. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a schematic diagram of a method for preparing high angular momentum quantum states (Rydberg state nF 7 / 2 ) by means of three-photon excitation in an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a method for preparing high angular momentum quantum states (Rydberg state nF 7 / 2 ) by means of two-photon excitation combined with microwave excitation in an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] To make the objectives, technical solutions, and advantages of the present invention clearer, the following will further describe in detail the disclosed embodiments of the present invention with reference to the accompanying drawings.

[0028] For the measurement of radio frequency electric fields based on Rydberg atoms, it can be achieved when the principal quantum number n < 100 by using high angular momentum quantum states. Among them, the high angular momentum quantum state refers to a quantum state with an orbital angular momentum quantum number L ≥ 3, including F, G, H, etc., and the corresponding orbital angular momentum quantum numbers L are 3, 4, 5, etc. In addition, by introducing an external magnetic field, the atom will produce the Zeeman effect under the action of the external magnetic field. By changing the magnitude of the magnetic field, the magnetic sub-level interval of the Rydberg state can be adjusted, and continuous tunable radio frequency electric field frequency measurement can be achieved through continuously tunable magnetic field magnitudes.

[0029] In this embodiment, the method for measuring radio frequency electric fields based on high orbital angular momentum quantum states includes:

[0030] Step 1, prepare a matching high angular momentum quantum state according to the specific frequency point of the radio frequency electric field to be measured.

[0031] In this embodiment, a matching high angular momentum quantum state can be prepared by means of three-photon excitation or two-photon excitation combined with microwave excitation.

[0032] Preferably, as Figure 1 shown, the steps of preparing a matching high angular momentum quantum state by means of three-photon excitation are as follows: Use a laser with a wavelength of 852 nm to excite the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ; Use a laser with a wavelength of 917 nm to excite the atom from the first intermediate state 6P 3 / 2 to the second intermediate state 6D5 / 2 ; Use a laser with a wavelength of 1141 nm to excite the atom from the second intermediate state 6D 5 / 2 to the first Rydberg state nF 7 / 2 ; Thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state, the second Rydberg state nG 7 / 2 , the sensing of the radio frequency electric field is realized.

[0033] Preferably, as Figure 2 shown, the steps of preparing a phase-matched high angular momentum quantum state by using two-photon excitation in combination with microwave excitation are as follows: Use a laser with a wavelength of 852 nm to excite the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ; Use a laser with a wavelength of 509 nm to excite the atom from the first intermediate state 6P 3 / 2 to the third Rydberg state nD 5 / 2 ; Use a microwave with a frequency of GHz to excite the atom from the third Rydberg state nD 5 / 2 to the first Rydberg state nF 7 / 2 ; Thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state, the second Rydberg state nG 7 / 2 , the sensing of the radio frequency electric field is realized.

[0034] Step 2, at the resonance frequency point, based on the prepared phase-matched high angular momentum quantum state, use the EIT-AT splitting measurement method or the heterodyne measurement method based on Rydberg atoms to measure the intensity of the incident radio frequency electric field.

[0035] In this embodiment, taking the measurement of the radio frequency electric field with a measurement frequency of 180 MHz to 200 MHz as an example, in this frequency range, the existing resonance frequency points are 184.391 MHz (98F 7 / 2 →98G 7 / 2 ), 190.152 MHz (97F 7 / 2 →97G 7 / 2 ) and 196.155 MHz (96F 7 / 2 →96G 7 / 2 ). At these three resonance frequency points, the resonance between the electric field to be measured and the Rydberg energy level can be achieved without applying an external magnetic field.

[0036] Step 3, in addition to measuring the resonance frequency point, use an external field control method to realize the measurement of continuously tunable radio frequency electric field frequency.

[0037] In this embodiment, except for measuring at the resonance point, in order to further expand the measurement frequency range, an external field regulation method (applied electric field and applied magnetic field) can be adopted to achieve continuously tunable radio frequency electric field frequency measurement. Among them, in the presence of a magnetic field, the Rydberg energy level undergoes Zeeman splitting, and by changing the magnitude of the applied magnetic field, the magnetic sub-levels of the Rydberg energy level are adjusted. In the presence of an electric field, by changing the magnitude of the applied electric field, the displacement of the Rydberg energy level is adjusted to achieve the expansion of the measurement frequency within a certain range.

[0038] Taking the radio frequency electric field with a measurement frequency of 180 MHz to 200 MHz as an example, in this frequency range, the existing resonance frequencies are 184.391 MHz (98F 7 / 2 →98G 7 / 2 ), 190.152 MHz (97F 7 / 2 →97G 7 / 2 ) and 196.155 MHz (96F 7 / 2 →96G 7 / 2 ). When deviating from the above three resonance frequencies, the methods for realizing electric field measurement are as follows:

[0039] Adopt the method of applying an external electric field. In the presence of an external electric field, utilize the Stark effect Δf = αE 2 / 2. By changing the magnitude of the applied electric field, the displacement of the Rydberg energy level is adjusted. Among them, Δf represents the energy level shift interval, α represents the electric susceptibility of the Rydberg energy level, and E represents the magnitude of the applied electric field.

[0040] Adopt the method of applying an external magnetic field. In the presence of an external magnetic field, the Rydberg energy level undergoes Zeeman splitting. Utilize the Zeeman effect to adjust the magnetic sub-levels of the Rydberg energy level by changing the magnitude of the applied magnetic field. Among them, ΔE = h·ΔF = μ·Bcosθ, ΔE represents the energy difference of the energy level transition, h represents Planck's constant, ΔF represents the frequency interval between energy levels, μ represents the total magnetic moment of the atom, B represents the magnetic induction intensity, and θ represents the angle between the total magnetic moment and the magnetic field direction.

[0041] On the basis of the above embodiment, taking cesium atoms as an example, the method of three-photon excitation and the method of two-photon excitation combined with microwave excitation are used to prepare high orbital angular momentum quantum states respectively, and the Rydberg energy level or its magnetic sub-levels are adjusted by an external electric field or magnetic field to achieve radio frequency electric field measurement below 300 MHz.

[0042] As Figure 1 shown, the laser with a wavelength near 852 nm excites the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 , and the laser with a wavelength near 917 nm excites the atom from the first intermediate state 6P 3 / 2 to the second intermediate state 6D 5 / 2, a laser with a wavelength near 1141 nm excites the atom from the second intermediate state 6D 5 / 2 to the first Rydberg state nF 7 / 2 , thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state nG 7 / 2 , the sensing of the radio frequency electric field can be achieved. Under the action of an external electric field, the Rydberg energy levels will undergo a small range of shifts, and the shift range is related to the applied electric field strength. Under the action of an external magnetic field, the Rydberg energy levels will further split, and the splitting interval is related to the magnitude of the applied magnetic field. The splitting interval of the energy levels can be adjusted by adjusting the magnetic field magnitude, so as to match the frequency of the measured radio frequency electric field and achieve resonance transition.

[0043] As Figure 2 shown, a laser with a wavelength near 852 nm excites the atom from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 , a laser with a wavelength near 509 nm excites the atom from the first intermediate state 6P 3 / 2 to the third Rydberg state nD 5 / 2 , and a microwave with a frequency of GHz is used to excite the atom from the third Rydberg state nD 5 / 2 to the first Rydberg state nF 7 / 2 ; thus, through the first Rydberg state nF 7 / 2 and the second Rydberg state the second Rydberg state nG 7 / 2 , the sensing of the radio frequency electric field is achieved. Under the action of an external electric field, the Rydberg energy levels will undergo a small range of shifts, and the shift range is related to the applied electric field strength. Under the action of an external magnetic field, the Rydberg energy levels will further split, and the splitting interval is related to the magnitude of the applied magnetic field. The splitting interval of the energy levels can be adjusted by adjusting the magnetic field magnitude, so as to match the frequency of the measured radio frequency electric field and achieve resonance transition.

[0044] Although the present invention has been disclosed above with preferred embodiments, it is not used to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and decorations made to the above embodiments according to the technical essence of the present invention without departing from the technical solution of the present invention all belong to the protection scope of the technical solution of the present invention.

[0045] The content not detailedly described in the specification of the present invention belongs to the well-known technology of those skilled in the art.

Claims

1. A method for measuring radio frequency electric fields based on the measurement of high orbital angular momentum quantum states, characterized in that, Including: Preparing a matched high-angular-momentum quantum state according to the specific frequency point of the measured radio-frequency electric field; At the resonance frequency point, based on the prepared matched high-angular-momentum quantum state, measuring the intensity of the incident radio-frequency electric field by using the EIT-AT splitting measurement method or the superheterodyne measurement method based on Rydberg atoms; For measurements outside the resonance frequency point, an external field control method is used to achieve continuously tunable radio-frequency electric field frequency measurement.

2. The method for measuring a radio frequency electric field based on a high orbital angular momentum quantum state according to claim 1, wherein The high-angular-momentum quantum state refers to a quantum state with an orbital angular momentum quantum number L≥3.

3. The method for measuring a radio frequency electric field based on a high orbital angular momentum quantum state according to claim 1, wherein A matched high-angular-momentum quantum state is prepared by means of three-photon excitation or a combination of two-photon excitation and microwave excitation.

4. The method for measuring a radio frequency electric field based on a high orbital angular momentum quantum state according to claim 3, wherein The steps for preparing a matched high-angular-momentum quantum state by means of three-photon excitation are as follows: Use a laser with a wavelength of 852 nm to excite the atoms from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ; Atoms are excited from the first intermediate state 6P to the second intermediate state 6D by a laser with a wavelength of 917 nm 3 / 2 5 / 2 ;​ Use a laser with a wavelength of 1141 nm to excite the atom from the second intermediate state 6D 5 / 2 to the first Rydberg state nF 7 / 2 ; thereby, through the first Rydberg state nF 7 / 2 and the second Rydberg state nG 7 / 2 , realize the perception of the radio frequency electric field.

5. The method for measuring a radio frequency electric field based on a high orbital angular momentum quantum state according to claim 3, wherein The steps for preparing a matched high-angular-momentum quantum state by means of a combination of two-photon excitation and microwave excitation are as follows: Use a laser with a wavelength of 852 nm to excite the atoms from the ground state 6S 1 / 2 to the first intermediate state 6P 3 / 2 ; Atoms are excited from the first intermediate state 6P to the third Rydberg state nD by a laser with a wavelength of 509 nm 3 / 2 5 / 2 ;​ Using microwaves with a frequency of GHz to transfer atoms from the third Rydberg state nD 5 / 2 to the first Rydberg state nF 7 / 2 ; thereby, through the first Rydberg state nF 7 / 2 and the second Rydberg state nG 7 / 2 , the sensing of the radio frequency electric field is achieved.

6. The method for measuring radio frequency electric field based on high orbital angular momentum quantum state according to claim 1, wherein The external field control method includes: an applied electric field and an applied magnetic field.

7. The method for measuring radio frequency electric field based on high orbital angular momentum quantum state according to claim 6, wherein In the presence of an externally applied electric field, the shift of the Rydberg energy level is adjusted by changing the magnitude of the applied electric field; where Δf = αE 2 / 2, Δf represents the energy level shift interval, α represents the polarizability of the Rydberg energy level, and E represents the magnitude of the applied electric field.

8. The method for measuring radio frequency electric field based on high orbital angular momentum quantum state according to claim 6, characterized in that, In the presence of an applied magnetic field, the Rydberg energy level undergoes Zeeman splitting. By using the Zeeman effect, the magnetic sub-levels of the Rydberg energy level are adjusted by changing the magnitude of the applied magnetic field; where, ΔE = h·ΔF = μ·Bcosθ, ΔE represents the energy difference of the energy level transition, h represents the Planck constant, ΔF represents the frequency interval between energy levels, μ represents the total magnetic moment of the atom, B represents the magnetic induction intensity, and θ represents the angle between the total magnetic moment and the magnetic field direction.

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