A rydberg atom electromagnetic direction finding system and method

Abstract

The application discloses a Rydberg atom electromagnetic direction-finding system, comprising a double-atom gas chamber module, a laser module, an optical element module, a phase-locked amplification module and a data solving and processing module; the double-atom gas chamber module provides a plurality of spatially discrete quantum sensing points to perceive microwave phases in parallel, the laser module provides laser with wavelengths of 509 nm and 852 nm, the optical element module is used for splitting and combining light beams and regulating and controlling polarization, two detection light beams carrying phase information are converted into photocurrent by a balanced photodetector, and differential processing is carried out, the phase-locked amplification module demodulates the phase difference of the electric signals of the two light paths, and the data solving and processing module solves the direction-of-arrival angle of a to-be-measured microwave signal. The application further provides a Rydberg atom electromagnetic direction-finding method. The core innovation of the application is that the high sensitivity of Rydberg atoms to an electric field improves the phase interference direction-finding precision, and accurate direction-finding of a spatial electromagnetic wave is realized.

Description

Technical Field

[0001] This invention belongs to the field of quantum precision measurement and electromagnetic spectrum sensing technology, specifically relating to a Rydberg atom electromagnetic direction finding system and method based on dual-atom gas cell phase measurement. Technical Background Electromagnetic wave direction finding technology plays a crucial role in radar, communications, radio astronomy, and radio monitoring. Traditional direction finding methods mainly include amplitude comparison, phase interferometry, and Doppler frequency difference methods. Among them, phase interferometry is widely used due to its high accuracy and excellent instantaneous direction finding capability. This method measures the phase difference of the signal arriving at multiple spatially separated antenna elements and calculates the direction of arrival based on geometric relationships. However, the sensitivity, bandwidth, and dynamic range of traditional electronic antennas are limited by their physical characteristics, and they are susceptible to interference in complex electromagnetic environments.

[0002] Rydberg atoms possess extremely large electric dipole moments, making them highly sensitive to external electromagnetic fields. Highly sensitive electric field measurements can be achieved using the electromagnetically induced transparency (EIT) effect. In recent years, electric field measurements based on Rydberg atoms have shown great potential in terms of sensitivity, traceability, and miniaturization. However, current technologies primarily focus on measuring electric field intensity, lacking effective solutions for direct measurement of electromagnetic wave phase and direction finding applications based on phase differences. Traditional single-cell methods struggle to obtain spatial phase distribution information, and there is a lack of models that directly map the atomic phase response to the incident angle of the electromagnetic wave. Summary of the Invention

[0003] The technical problem to be solved by this invention is to realize phase difference direction finding through a dual-atom gas cell by utilizing the electric field sensitivity characteristics of Rydberg atoms.

[0004] The technical solution of this invention is as follows: a complete direction finding system is constructed by using a dual-atom gas cell module, a laser module, an optical element module, a lock-in amplification module, and a data calculation and processing module. A dual-channel quantum detection unit is formed by two spatially separated atomic gas cells. The laser provides excitation light to prepare Rydberg atoms. The optical element realizes laser control and photoelectric conversion. The lock-in amplification module is used to lock-in and demodulate the phase difference between the two signals. Then, the data calculation and processing module combines the phase difference with the spatial geometry of the gas cells to calculate the direction of arrival of the electromagnetic wave to be measured.

[0005] The principle of this invention is: (1) Electromagnetically induced transparency (EIT) effect EIT is a quantum interference effect that occurs in specific atomic or molecular energy level systems (usually Λ-type, V-type, or step-type three-level systems). By simultaneously applying probe light (low-level transition) and coupling light (high-level transition) to the atom, under two-photon resonance conditions, the absorption of the probe light by the atom is suppressed, forming a transparent window.

[0006] Under the vortex approximation, the Hamiltonian of the system and the polarizability of the probe light can describe this effect. For a Λ-type system, the expression for the linear polarizability χ of the probe light is: (1) in, Atomic number density, energy level and Dipole matrix elements between ground state and Decoherence rate between them excited state to ground state The rate of decoherence, To detect optical detuning, Controlling optical detuning, Controlling the Rabi frequency of light, The imaginary unit is used to distinguish between the real and imaginary parts of linear polarizability. The vacuum permittivity, is the reduced Planck constant.

[0007] (2) Autler-Townes (AT) split AT splitting refers to the phenomenon where, under the influence of a strong light field, the energy levels of atoms or molecules undergo stimulated Rabi oscillations, resulting in the original energy level splitting into two new energy levels.

[0008] The core physical quantity of AT splitting is the stimulated Rabi frequency. It describes the intensity of the interaction between a strongly coupled light field and atoms. Its core formula is: (2) (3) (4) in, For atomic transition electric dipole moments, To drive the electric field intensity of the optical field, This is the reduced Planck constant. This coupling causes symmetric splitting of the atomic energy levels, resulting in an energy shift of... The modified state corresponds to the Autler-Townes double peak in the spectrum, with a peak-to-peak angular frequency difference. , The larger the value, the more significant the energy level splitting and spectral double-peak effect.

[0009] (3) Direction finding by phase interferometry In a superheterodyne receiver, the Rydberg atom probe can be considered a quantum mixer. It modulates the phase of the incident electromagnetic wave with high fidelity onto the intensity envelope phase of the probe light using higher-order terms of atomic polarizability. A photodetector and lock-in amplifier then compare the phases of the original probe light (reference signal) and the modulated probe light (measured signal), accurately measuring the relative phase difference between the two signals. In this system, due to the different positions of the two atomic cells, there is a wavenumber difference in the received wavefront. This wavenumber difference is converted into a phase difference, and the incident angle can be deduced by measuring the phase difference.

[0010] Assuming the distance between the two atomic gas chambers is When electromagnetic waves move at an angle At the point of incidence (angle with the normal to the atomic gas cell), the difference in path length to the two solar lines is: (5) corresponding phase difference for: (6) in The wavelength is the signal wavelength. Measured by a lock-in amplifier. Then the direction of the incoming wave can be determined: (7) The technical solution provided by this invention is as follows: a Rydberg atomic electromagnetic direction finding system based on dual-atom gas cell phase measurement, comprising a dual-atom gas cell module, a laser module, an optical element module, a lock-in amplification module, and a data processing module; wherein, the dual-atom gas cell module serves as the detection area for dual-channel microwave phase detection; the laser module provides stable 509nm and 852nm excitation light for preparing Rydberg states and reading phase information; the optical element module includes a waveplate, a PBS (polarizing beam splitter prism), and a photodetector for realizing laser beam splitting, beam combining, polarization control, and collecting optical signals carrying phase differences; the lock-in amplification module includes a lock-in amplifier, which obtains the phase difference between the two optical paths by demodulating the differential output electrical signal of the balanced photodetector; the data processing module includes an FPGA (Field Programmable Gate Array), which is used to acquire the phase difference data output by the lock-in amplification module and calculate the arrival direction angle of the microwave signal under test.

[0011] Furthermore, in the dual-atom gas chamber module, the first and second atomic gas chambers are cylindrical, filled with cesium atom gas, and nitrogen is used as a buffer gas. The two chambers are arranged in parallel side by side, with a spacing between them. d 12Based on the electromagnetic wave frequency band of the target under test, it meets the following requirements. d 12 ≤ / 2, where λ is the center wavelength of the signal to be measured.

[0012] Furthermore, the laser modules are lasers with wavelengths of 509 nm and 852 nm: the 852 nm laser pumps cesium atoms to the first-order excited state, and this laser uses saturable absorption spectrum frequency locking to control the output wavelength fluctuation within a certain range. Within nm; 509nm lasers are usually realized by down-conversion of 1020nm semiconductor lasers through frequency doubling crystals, which further pump cesium atoms to the second excited state, namely the Rydberg state.

[0013] Furthermore, the optical element module consists of a half-wave plate, a polarizing beam splitter, a reflector, a convex lens, a dichroic mirror, and a photodetector. First, the half-wave plate is used to change the polarization direction of the 509nm laser. Then, the polarizing beam splitter decomposes the incident light into two polarized beams with a power ratio of 50:50. Next, the reflector and convex lens are used to ensure that the polarized light is accurately incident on the atomic gas cell according to the optical path design. The outgoing light passes through the dichroic mirror to filter out the coupling light, leaving the probe light to be incident on the photodetector. Finally, the balanced photodetector converts the optical signals of the two optical paths into electrical signals and performs differential output, outputting a light intensity difference signal related to the phase difference. The relative phase difference between the two signals is directly measured by a lock-in amplifier.

[0014] Another technical solution provided by this invention is: a Rydberg atomic electromagnetic direction finding method based on phase measurement of a two-atom gas cell. First, a two-atom gas cell is constructed and spaced according to a preset baseline. d 12 The process involves several steps: First, the chamber is filled with microwave-sensitive cesium atoms. Second, 509nm and 852nm lasers are used to provide coupling and probe light, respectively, simultaneously acting on the diatomic gas cell. The cesium atoms are then prepared to the Rydberg state using electromagnetic induction transparency. Third, microwave signals emitted by a horn antenna are simultaneously applied to the diatomic gas cell, inducing Autler-Townes splitting in the EIT spectrum. Finally, a balanced photodetector converts the two light intensities into electrical signals and outputs them differentially. The phase difference between the two signals is obtained by lock-in amplification. Finally, the direction of arrival angle of the microwave signal under test is calculated based on the geometric relationship between the phase difference and the direction of arrival.

[0015] Compared with existing solutions, the main advantages of this invention are: (1) The present invention proposes a novel dual-atom gas cell structure, which utilizes two independent atomic gas cells to suppress interference such as laser frequency noise and ambient temperature changes through common mode, thereby improving the stability of phase measurement.

[0016] (2) The present invention realizes the mapping relationship between phase and angle, and converts the measured phase difference into the incident angle through geometric relationship, thereby realizing high-precision electromagnetic wave direction finding. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the principle of the direction finding method and system of the present invention. Figure 2 This is a schematic diagram of the geometric relationship between the diatomic gas chamber probe and the incident electromagnetic wave. Detailed Implementation The Rydberg atomic electromagnetic direction finding system based on dual-atom gas cell phase measurement of the present invention includes a dual-atom gas cell module, a laser module, an optical element module, a lock-in amplification module, and a data processing module. The dual-atom gas cell module employs two parallel cylindrical cesium atom gas cells, filled with cesium atoms and a nitrogen buffer gas, with a distance between the two gas cells... d 12 A dual-channel microwave phase detection region is formed, satisfying a wavelength no greater than half the center wavelength λ of the microwave signal under test. The laser module outputs stable 852nm and 509nm lasers, respectively exciting cesium atoms to Rydberg states, providing a quantum basis for microwave field-sensitive detection. The optical component module uses waveplates, polarizing beam splitters, mirrors, convex lenses, and dichroic mirrors to perform laser beam splitting, beam combining, polarization control, and optical path collimation, sending the signal light carrying phase information into a balanced photodetector, converting it into a differential electrical signal. The lock-in amplification module independently receives this weak electrical signal, filters noise through lock-in demodulation, accurately extracts the phase of the two signals, and calculates the phase difference. The data processing module uses an FPGA to acquire phase difference data in real time, and combines the geometric spacing of the two gas chambers with a phase interferometry direction-finding algorithm to calculate the direction angle of arrival of the microwave signal under test. This system first prepares atomic Rydberg states, then generates Autler-Townes splitting through microwave-induced EIT spectroscopy, extracts the phase difference through photoelectric conversion and phase-locked demodulation, and finally achieves high-precision electromagnetic direction finding by algorithm calculation.

[0018] The Rydberg atomic electromagnetic direction finding method based on phase measurement of a dual-atom gas cell of the present invention includes the following steps: First, constructing a dual-atom gas cell and spacing it according to a preset baseline. d 12The process involves several steps: First, the chamber is filled with microwave-sensitive cesium atoms. Second, 509nm and 852nm lasers are used to provide coupling and probe light, respectively, simultaneously acting on the diatomic gas cell. The cesium atoms are then prepared to the Rydberg state using electromagnetic induction transparency. Third, microwave signals emitted by a horn antenna are simultaneously applied to the diatomic gas cell, inducing Autler-Townes splitting in the EIT spectrum. Finally, a balanced photodetector converts the two light intensities into electrical signals and outputs them differentially. The phase difference between the two signals is obtained by lock-in amplification. Finally, the direction of arrival angle of the microwave signal under test is calculated based on the geometric relationship between the phase difference and the direction of arrival.

[0019] The contents not described in detail in this invention are existing technologies known to those skilled in the art.

Claims

1. A Rydberg atomic electromagnetic direction finding system, characterized in that, The system comprises a diatomic gas cell module, a laser module, an optical element module, a lock-in amplifier module, and a data processing module. The diatomic gas cell module serves as the detection region for dual-channel microwave phase detection. The laser module provides stable 509nm and 852nm excitation light for preparing Rydberg states. The optical element module includes waveplates, a photodiode (PBS), and a photodetector, used for laser beam splitting, combining, polarization control, and collecting optical signals carrying phase differences. The lock-in amplifier module includes a lock-in amplifier that demodulates the differential output electrical signal from the balanced photodetector to obtain the phase difference between the two optical paths. The data processing module includes an FPGA, used to acquire the phase difference data output from the lock-in amplifier module and calculate the direction of arrival angle of the microwave signal under test.

2. The Rydberg atomic electromagnetic direction finding system according to claim 1, characterized in that, In the aforementioned dual-atom gas chamber module, the first and second atomic gas chambers are cylindrical, filled with cesium atomic gas, and buffered with nitrogen gas. They are arranged in parallel side-by-side, with a spacing between them. d 12 Based on the electromagnetic wave frequency band of the target under test, it meets the following requirements. d 12 ≤ / 2, where λ is the center wavelength of the signal to be measured.

3. The Rydberg atomic electromagnetic direction finding system according to claim 1, characterized in that, The laser modules are lasers with wavelengths of 509nm and 852nm respectively: the 852nm laser pumps cesium atoms to the first-order excited state, and this laser uses saturated absorption spectrum frequency locking to control the output wavelength fluctuation within a certain range. Within nm; the 509nm laser is realized by down-conversion of the 1020nm semiconductor laser through a frequency doubling crystal. This laser further pumps cesium atoms to the second-order excited state, namely the Rydberg state.

4. The Rydberg atomic electromagnetic direction finding system according to claim 1, characterized in that, The optical element module consists of a half-wave plate, a polarizing beam splitter, a mirror, a convex lens, a dichroic mirror, and a photodetector. First, the half-wave plate is used to change the polarization direction of the 509nm laser. Then, the polarizing beam splitter decomposes the incident light into two polarized beams with a power ratio of 50:

50. Next, the mirror and convex lens are used to ensure that the polarized light is accurately incident on the atomic gas cell according to the optical path design. The outgoing light passes through the dichroic mirror to filter out the coupling light, leaving the probe light to enter the photodetector. Finally, the balanced photodetector converts the two probe light signals carrying phase information into photocurrents, performs differential processing, suppresses common-mode noise, and outputs a weak differential electrical signal.

5. The Rydberg atomic electromagnetic direction finding system according to claim 1, characterized in that, The lock-in amplifier module is set up independently and is used to receive the electrical signal output by the differential output of the balanced photodetector in the optical element module. It obtains the phase difference value of the two signals through lock-in demodulation and finally outputs high-precision phase difference data.

6. The Rydberg atomic electromagnetic direction finding system according to claim 1, characterized in that, The data processing module uses the FPGA to collect the phase difference data output by the lock-in amplifier module, combines it with the preset geometric layout parameters of the dual-atom gas cell, and substitutes it into the phase interferometry direction finding algorithm to calculate the arrival direction angle of the microwave signal under test.

7. A Rydberg atom electromagnetic direction finding method, characterized in that, First, construct the diatomic gas cell and arrange it according to the preset baseline spacing. d 12 The process involves several steps: First, the chamber is filled with microwave-sensitive cesium atoms. Second, 509nm and 852nm lasers are used to provide coupling and probe light, respectively, simultaneously acting on the diatomic gas cell. The cesium atoms are then prepared to the Rydberg state using electromagnetic induction transparency. Third, microwave signals emitted by a horn antenna are simultaneously applied to the diatomic gas cell, inducing Autler-Townes splitting in the EIT spectrum. Finally, a balanced photodetector converts the two light intensities into electrical signals and outputs them differentially. The phase difference between the two signals is obtained by lock-in amplification. Finally, the direction of arrival angle of the microwave signal under test is calculated based on the geometric relationship between the phase difference and the direction of arrival.

Images