Time-frequency multi-dimensional coding frequency hopping communication method and device based on Rydberg atoms

Abstract

The invention belongs to the technical field of communication, and relates to a time-frequency multi-dimensional coding frequency hopping communication method and device based on Rydberg atoms. Comprising the following steps: exciting a cesium atom system from a ground state to an intermediate excitation state by utilizing probe light, and exciting the cesium atom system from the intermediate excitation state to a Rydberg state by utilizing coupling light; determining the resonant frequency and the non-resonant frequency of a carrier based on the energy level of the cesium atom system in the Rydberg state, and selecting the carrier of the resonant frequency or the non-resonant frequency according to the binary state of the baseband signal to perform time-frequency coding to generate a frequency hopping sequence; and radiating the frequency hopping sequence to a cesium atom system in a Rydberg state, and receiving a spectral signal of the transmissivity of the detection light passing through the cesium atom system so as to complete receiving of a baseband signal. According to the invention, frequency hopping sequence synchronization and signal modulation are not needed, the complexity of the system is reduced, and the method has the characteristic of tracking interference resistance.

Description

Technical Field

[0001] This application belongs to the field of communication technologies, and particularly relates to a time-frequency multi-dimensional coding frequency-hopping communication method and apparatus based on Rydberg atoms. Background Art

[0002] In today's communication field, communication security has always been a key issue of great concern. With the rapid development of information technology and the increasingly complex communication environment, malicious interference and detection and monitoring are becoming more and more common, posing a serious threat to communication security. These malicious behaviors may not only lead to the leakage of important information, but also cause the interruption of communication links, seriously affecting the accuracy and timeliness of information transmission, and then having a significant impact on various systems and services relying on communication. To address the above challenges, frequency-hopping communication technology has emerged and been widely applied. The basic principle of frequency-hopping communication is that during the communication process, the carrier frequency is controlled by a specific frequency-hopping sequence to quickly and randomly switch between multiple preset frequencies. This dynamic change in frequency makes it difficult for external interference sources to continuously track and interfere with the communication signal, thus significantly improving the anti-interference ability and concealment of the communication system. In a complex electromagnetic environment, frequency-hopping communication can effectively reduce the probability of the signal being interfered with and ensure the reliable transmission of information.

[0003] However, conventional frequency-hopping technologies still have some obvious limitations in practical applications. On the one hand, the frequency-hopping rules adopted by conventional frequency-hopping technologies are relatively simple and fixed, and are easily predicted by external interference parties through long-term signal monitoring and analysis. Once the interference party masters the frequency-hopping rules, it can implement targeted tracking interference, greatly weakening the anti-interference performance of frequency-hopping communication and making the communication system face serious security risks. On the other hand, traditional communication receivers require the frequency-hopping sequences of the transceiver parties to be strictly synchronized in order to ensure that the correct carrier frequency can be quickly and accurately captured. During the actual communication process, due to the influence of various factors, it is very easy for the transceiver parties to have a synchronization deviation. Once this occurs, the receiver will not be able to correctly identify and track the signal, resulting in misdecoding or loss of information, and then seriously affecting the reliability and stability of communication.

[0004] In recent years, the booming development of quantum technology has brought new opportunities and breakthrough directions to the field of communication. Among them, Rydberg atoms, as a kind of substance with unique quantum properties, have shown great application potential in the field of communication. Rydberg atoms have a rich energy level structure, which covers multiple frequency bands from hertz to terahertz. Their unique quantum properties enable communication systems based on Rydberg atoms to achieve the function of "multi-frequency transmission and integrated reception". Compared with traditional frequency hopping communication systems, this characteristic makes the communication system more flexible and efficient when implementing multi-frequency hopping, without the need for complex synchronization mechanisms to ensure the frequency consistency between the transceiver parties, and is expected to solve the synchronization difficulties in traditional frequency hopping communication, providing a new technical approach to improve the security and reliability of communication. Summary of the Invention

[0005] Aiming at the technical problems existing in the prior art, this application aims to provide a time-frequency multi-dimensional coding frequency hopping communication method based on Rydberg atoms, as well as a device suitable for this method. This application divides the carrier signal into a resonance frequency sequence and a non-resonance frequency sequence to form a dual-sequence parallel transmission mechanism, realizes the parallel demodulation and signal reconstruction of the above dual-sequence carriers, and then achieves the technical effect of multi-sequence collaborative frequency hopping reception. This method does not require frequency hopping sequence synchronization and has potential advantages in improving the anti-interference ability, confidentiality of communication, and achieving more efficient communication.

[0006] In order to achieve the above technical objectives, the following technical solutions are adopted in this application: On the one hand of this application, a time-frequency multi-dimensional coding frequency hopping communication method based on Rydberg atoms is provided, including the following steps: Use the probe light to excite the cesium atom system from the ground state to the intermediate excited state, and use the coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state; Based on the energy levels of the cesium atom system in the Rydberg state, determine the resonance frequency and non-resonance frequency of the carrier, and select the carrier of the resonance frequency or non-resonance frequency for time-frequency coding to generate a frequency hopping sequence according to the binary state of the baseband signal; Radiate the frequency hopping sequence to the cesium atom system in the Rydberg state, and receive the spectral signal of the transmittance of the probe light passing through the cesium atom system to complete the reception of the baseband signal.

[0007] In one embodiment, the wavelength of the probe light is 852 nm, and the probe light excites the cesium atom system from the ground state to the intermediate excited state 6P 3 / 2 .

[0008] In one embodiment, the wavelength of the coupling light is 509 nm, and the coupling light excites the cesium atom system from the intermediate excited state to the Rydberg state 66S 1 / 2 .

[0009] In one embodiment, the resonant frequency is used as the first channel, and the non-resonant frequency is used as the second channel. In each time slot, when the baseband signal is characterized by a first preset logic value, the carrier selects the frequency point of the first channel; when the baseband signal is characterized by a second preset logic value, the carrier selects the frequency point of the second channel. By combining time slot selection, time-frequency coding of the carrier for the baseband signal is achieved.

[0010] In one embodiment, the time slot selection includes: generating a set of pseudo-random sequences locally, and using the timing information corresponding to each element in the pseudo-random sequences to control the start and end time slots of each hop period of the carrier frequency hopping.

[0011] In one embodiment, the resonant frequency includes one or more of 12.53 GHz, 13.41 GHz, 14.28 GHz, and 15.21 GHz.

[0012] In one embodiment, the non-resonant frequency includes one or more of 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, and 18 GHz.

[0013] In another aspect of the present application, a time-frequency multi-dimensional coding frequency hopping communication device based on Rydberg atoms is provided, including a transmitting end and a receiving end; The transmitting end includes an analog signal source and a coding module. The analog signal source is used to generate carriers of different frequencies, and the coding module is used to generate a frequency hopping sequence by time-frequency coding of the carrier according to the baseband signal; The receiving end includes an atomic excitation module and a spectral analysis module. The atomic excitation module is used to emit a probe light to excite the cesium atom system from the ground state to an intermediate excited state, and emit a coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state; the spectral analysis module is used to receive the probe light passing through the cesium atom system in the Rydberg state when the frequency hopping sequence is radiated, and analyze the spectral signal to extract the baseband signal.

[0014] In one embodiment, the transmitting end further includes a horn antenna, and the horn antenna radiates the frequency hopping sequence to the cesium atom system in the Rydberg state at the receiving end.

[0015] In one embodiment, the atomic excitation module includes a cesium atom gas cell, a first laser, and a second laser. The first laser is used to emit the probe light, and the second laser is used to emit the coupling light. The probe light and the coupling light are respectively incident on the cesium atom gas cell from both ends in opposite directions, and the light beams of the probe light and the coupling light incident on the cesium atom gas cell coincide with each other in the cesium atom gas cell.

[0016] The beneficial effects of the present application are: 1) Simplification of frequency hopping sequence synchronization Utilizing the unique physical properties of Rydberg atoms, during the communication process, the receiving end does not need to perform the synchronization operation of the frequency hopping sequence. Rydberg atoms have a highly sensitive energy level structure and unique optical response characteristics, enabling the accurate parsing of the transmitted information at the receiving end without the need to synchronize the frequency hopping sequence additionally, simplifying the complexity of the communication system, reducing the system implementation cost, and improving the reliability and stability of communication.

[0017] 2) High - efficiency coding This application innovatively divides the carrier signal into a resonant frequency sequence and a non - resonant frequency sequence. Different states of the baseband signal (such as high level and low level) respectively correspond to the selection of resonant frequency or non - resonant frequency for coding. During the data transmission process, the hopping of the carrier frequency is directly controlled by the baseband information without the need for traditional modulation operations, greatly improving the data transmission efficiency.

[0018] 3) Improvement of anti - interference performance Since the non - resonant frequency points are far detuned and Rydberg atoms are not sensitive to their responses, the increase in non - resonant frequency points can well hide the resonant frequency points, thereby reducing the probability of the resonant frequency points being interfered. Additionally, for tracking interference, when the resonant frequency signal is detected and the interfering party implements a signal of the same frequency for tracking interference, within this time slot, Rydberg atoms will not be interfered but will generate a stronger AT splitting due to the higher power, resulting in a reduced transmittance and an increased probability of being detected by the receiver; if the non - resonant frequency signal is detected, within this time slot, the interfering party interferes with the same frequency with a certain power, the frequency shift of the EIT spectrum is very small, the transmittance of the EIT peak remains almost unchanged, and the interference effect of the non - resonant frequency points is also small, so it has the effect of improving anti - tracking interference. Description of the drawings

[0019] Figure 1 It is a schematic diagram of the device for the time - frequency multi - dimensional coding frequency hopping method based on Rydberg atoms in the embodiment of this application; Figure 2 It is a schematic diagram of the energy levels of Rydberg atom resonance frequencies in the embodiment of this application; Figure 3 It is the EIT spectrum and AT splitting spectrum diagram in the embodiment of this application; Figure 4 It is the relationship diagram between the transmittance of the EIT peak and the carrier electric field strength in the embodiment of this application; Figure 5 It is the frequency hopping pattern of carrier time - frequency multi - dimensional coding in the embodiment of this application. Detailed implementation manners

[0020] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application without creative efforts shall fall within the protection scope of the present application.

[0021] The present application proposes a time-frequency multi-dimensional coding frequency-hopping receiving method based on Rydberg atoms. The baseband information is encoded onto the carrier, and at the same time, the carrier is divided into a resonance and a non-resonance dual sequence according to whether the frequency resonates with the atomic energy level. Utilizing the response of the atomic four-level structure to the carrier, multi-sequence frequency-hopping reception is achieved. At the same time, by combining the two dimensions of time and frequency, signals are transmitted at different time slots and frequency points. The present application can effectively enhance the concealment of communication, and can resist partial band interference and certain tracking interference. Moreover, the receiving end does not need to perform frequency-hopping sequence synchronization, reducing the complexity of the system, while enhancing the flexibility and stability of frequency-hopping communication.

[0022] In an embodiment of the present application, a time-frequency multi-dimensional coding frequency-hopping communication method based on Rydberg atoms is provided, including the following steps: S1: Use the probe light to excite the cesium atom system from the ground state to the intermediate excited state, and use the coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state.

[0023] In the present application, the ground state is the stable state in which the atom is normally located, and the intermediate excited state is the state in which the atom is at a higher energy after absorbing energy. The cesium atom system is irradiated with the probe light to cause the cesium atom to jump from the ground state (the state with the lowest energy) to the intermediate excited state.

[0024] In the present application, the probe light is an electromagnetic wave radiation with a specific photon energy, and its essence is a laser beam, possessing the common characteristics of lasers such as high coherence, high monochromaticity, and high directivity. The wavelength of the probe light is determined according to the energy level difference between the ground state and the specific excited state of the cesium atom system, and is usually in a specific spectral range. In some embodiments, the wavelength of the probe light is 852 nm, and the probe light excites the cesium atom system from the ground state to the intermediate excited state 6P 3 / 2 。

[0025] To ensure that the cesium atom system can stably and effectively absorb the photon energy of the probe light and achieve the transition from the ground state to the intermediate excited state, the frequency of the probe light needs to have a high degree of stability. In some embodiments, the frequency of the probe light is locked to the cesium atom D2 absorption line.

[0026] In this application, the coupling light is an electromagnetic wave radiation with a specific photon energy, which is essentially a laser beam. The wavelength of the coupling light is determined based on the energy level difference between the excited state and the Rydberg state of the cesium atom system, ensuring that its photon energy can be effectively absorbed by the cesium atoms in the intermediate excited state. In some embodiments, the wavelength of the coupling light is 509 nm, and the coupling light excites the cesium atom system from the intermediate excited state to the Rydberg state 66S 1 / 2 .

[0027] In this application, the frequency of the coupling light should have a certain degree of tunability. Its frequency adjustment range should be able to cover the possible small changes in the energy levels from the intermediate excited state to the Rydberg state of the cesium atom system to ensure accurate energy level transitions in different situations. In some embodiments, the frequency of the coupling light is locked at zero detuning, i.e., at the peak of the Electromagnetically Induced Transparency (EIT) spectrum

[0028] In this application, to effectively excite the cesium atom system, the probe light and the coupling light need to be precisely spatially coincident. Through a precise optical alignment system, such as using optical elements like mirrors and lenses, the two beams of light are adjusted to completely coincide in the region where the cesium atom system is located, ensuring that the atoms can be simultaneously affected by the probe light and the coupling light, thereby increasing the probability and efficiency of energy level transitions

[0029] S2: Determine the resonance frequency and non - resonance frequency of the carrier based on the energy levels of the cesium atom system in the Rydberg state, and select the resonance frequency or non - resonance frequency according to the binary state of the baseband signal for time - frequency coding to generate a frequency - hopping sequence

[0030] In this application, when the cesium atoms are excited to the Rydberg state, their energy levels are extremely sensitive to the external electromagnetic field, and there are specific energy differences between different energy levels. Through precise measurement and theoretical calculation, the carrier frequency matching the vicinity of the energy levels of the Rydberg - state cesium atoms is determined as the resonance frequency; and the frequency that does not match the energy level transition of the Rydberg - state cesium atoms is determined as the non - resonance frequency

[0031] When the frequency of the carrier signal is the same as this resonance frequency, the Rydberg - state cesium atoms will have a strong interaction with the carrier signal, resulting in physical phenomena such as Autler - Townes (AT) splitting, leading to significant changes in the optical response of the atoms, such as a decrease in transmittance

[0032] The principle of resonance response is as follows The EIT effect refers to the phenomenon that when a probe light and a coupling light interact in a three-level system, the probe light that would originally be absorbed by the atoms can pass through the gas cell without being absorbed. The probe light shows a transmission peak at the resonance frequency of the coupling light in the spectrum, which is simply referred to as the EIT signal. Applying a carrier wave resonant with the energy level frequency will destroy the transparency of the probe light to the atomic medium, reduce the transmittance at the EIT peak, and cause the spectrum to split, which is called the Autler-Townes (AT) split.

[0033] When the carrier signal resonates with the energy level to form a four-level system, according to the Lambert-Beer law, the output power of the probe light passing through the atomic gas cell is: (1) In the formula, L is the length of the atomic gas cell, is the wave number vector of the probe light, is the wavelength of the probe light, is the input optical power of the probe light. is the imaginary part of the polarizability of the atomic gas cell. When the frequency detunings of the probe light, coupling light, and carrier wave are all zero, Specifically expanded as: Specifically expanded as: (2) Among them, N is the atomic density, 、 are the vacuum permittivity and the reduced Planck constant respectively, 、 are the transition dipole moments corresponding to the energy levels of the probe light and the carrier signal, 、 are the Rabi frequencies corresponding to the energy levels of the carrier signal and the coupling light respectively. , where Γ1 is the spontaneous decay rate of the ground state, is the energy level is the spontaneous decay rate.

[0034] (3) Among them, 、 are the intensities of the carrier signal and the coupling light, is the transition dipole moment corresponding to the energy level of the coupling light.

[0035] According to formula (1), at the EIT transmission peak where the detuning of the coupling light is 0, the transmittance of the probe light, and the relationship with the Rabi frequencies of the carrier signal and the coupling light: The transmittance of the probe light at the EIT peak is nonlinearly negatively correlated with the Rabi frequency of the carrier signal.

[0036] When the frequency of the carrier signal is the same as the non-resonant frequency, due to the large detuning, the interaction between the Rydberg cesium atoms and the carrier signal is weak and does not cause significant changes in the optical response.

[0037] The specific principle of the non-resonant response is as follows: In the large detuning region, the EIT spectrum undergoes an AC Stark frequency shift under the action of an externally applied radio frequency field, and the shift is proportional to the square of the externally applied electric field strength E and can be expressed as: (4) where is related to the electric field frequency and represents the dynamic scalar polarizability at the frequency . The farther away from the resonance frequency, that is, the larger the frequency detuning amount, the smaller the value of , where the negative sign represents the detuning direction.

[0038] Although the non-resonant frequency will cause the EIT spectrum to shift left and right, the shift amount decreases with the increase of the frequency detuning amount. At the same time, different from the response in the resonance region, since the interaction between the Rydberg atoms and the external electric field is relatively weak in the large detuning region, a radio frequency signal with a larger electric field strength is required in the large detuning region to cause an obvious shift in the EIT spectrum. Therefore, the large detuning frequency and low field strength have little effect on the EIT frequency shift. In summary, the transmittance at the EIT peak when non-resonant is similar to the transmittance without the carrier field, but compared with the AT splitting caused by frequency resonance, the transmittance at the non-resonant EIT peak is higher, thus clearly distinguishing the response of the Rydberg atoms to the resonant frequency and the non-resonant frequency.

[0039] In some embodiments, the resonant frequency includes one or more of 12.53 GHz, 13.41 GHz, 14.28 GHz, and 15.21 GHz. The non-resonant frequency includes one or more of 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, and 18 GHz.

[0040] In some embodiments, the baseband signal generates a frequency hopping sequence by time-frequency encoding the carrier based on the resonant frequency and the non-resonant frequency, including: taking the resonant frequency as the first channel and the non-resonant frequency as the second channel. In each time slot, when the baseband signal is characterized by a first preset logic value, the carrier selects the frequency point of the first channel; when the baseband signal is characterized by a second preset logic value, the carrier selects the frequency point of the second channel, and combining the time slot selection to achieve the time-frequency encoding of the baseband signal.

[0041] Further, the time slot selection includes: locally generating a set of pseudo-random sequences, and using the timing information corresponding to each element in the pseudo-random sequences to control the start and end time slots of each hop period of the carrier frequency hopping.

[0042] For example, the frequencies resonant with the energy level 66S 1 / 2 are: 12.53 GHz, 13.41 GHz, 14.28 GHz, 15.21 GHz. Select the above resonant frequencies as channel F0, and at the same time select far-detuned non-resonant frequencies: 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, 18 GHz, as channel F1. The baseband signal encodes the carrier. For each hop, when the information is 1, the frequency of channel F1 is selected, and when the information is 0, the frequency of F0 is selected. For time slot selection, a set of pseudo-random sequences is locally generated to control the frequency hopping time slots of each hop, and a frequency hopping sequence is generated after carrier time-frequency encoding.

[0043] The time-frequency multi-dimensional coding principle is as follows: The frequency hopping signal can be expressed as: (5) where, M is the total number of hops, A、 and are respectively the amplitude, frequency and phase of the k th signal of each hop, T represents the frequency hopping time slot. is the time slot code of each hop, randomly generated by the pseudo-random code. In the k th frequency hopping period, the frequency hopping signal can be expressed as: (6) The frequency is determined by the digital baseband information , and the specific value is: (7) In the formula, F (0,k) , F (1,k) respectively represent the th frequency point of the resonant frequency channel , non-resonant frequency channel k .

[0044] S3: Radiate the frequency hopping sequence to the cesium atom system in the Rydberg state, and receive the spectral signal of the transmittance of the probe light passing through the cesium atom system to complete the reception of the baseband signal.

[0045] Specifically, at the transmitting end, an analog signal source with frequency hopping function is used to feed the generated frequency hopping sequence into the Rydberg atomic cell through a horn antenna. The horn antenna can effectively radiate electromagnetic wave signals into space, and the atoms in the Rydberg atomic cell will respond to these signals with different frequencies. At the receiving end, the probe light is connected to an oscilloscope through a photodetector. Rydberg atoms will produce different spectral responses to the carriers of the resonance frequency (the frequency of channel F0) and the non-resonance frequency (the frequency of channel F1). This response will change the transmittance of the probe light. By collecting the spectral signal of the probe light transmittance in real time through the oscilloscope, the baseband signal can be restored according to the change of the spectral signal, thus completing the reception of the baseband signal.

[0046] In another aspect of the present application, a time-frequency multi-dimensional coding frequency hopping communication device based on Rydberg atoms is provided, including a transmitting end and a receiving end.

[0047] In some embodiments, the transmitting end includes an analog signal source, a coding module, and a horn antenna. The analog signal source is used to generate carriers with different frequencies. The coding module is used to generate a frequency hopping sequence by time-frequency coding the carrier according to the baseband signal. The horn antenna radiates the frequency hopping sequence to the cesium atom system in the Rydberg state at the receiving end. Among them, the baseband signal generates a frequency hopping sequence by time-frequency coding the carrier based on the resonance frequency and the non-resonance frequency. The resonance frequency and the non-resonance frequency are determined based on the energy levels of the cesium atom system at the receiving end in the Rydberg state. For example, the cesium atom system at the receiving end uses a probe light with a wavelength of 852 nm to excite the atom from the ground state 6S 1 / 2 to the intermediate excited state 6P 3 / 2 , and a coupling light with a wavelength of 509 nm excites the atom from the intermediate excited state to the Rydberg state 66S 1 / 2 , then according to the Rydberg state 66S 1 / 2 , the nearby resonance frequencies can be calculated to be 12.53 GHz, 13.41 GHz, 14.28 GHz, or 15.21 GHz, and the non-resonance frequencies can be 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, or 18 GHz.

[0048] In some embodiments, the receiving end includes an atom excitation module and a spectral analysis module. The atom excitation module is used to generate a probe light to excite the cesium atom system from the ground state to the intermediate excited state, and generate a coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state. The spectral analysis module is used to receive the probe light passing through the cesium atom system when the frequency hopping sequence is radiated to the cesium atom system in the Rydberg state, and analyze the spectral signal to extract the baseband signal.

[0049] The atomic excitation module includes a cesium atomic gas cell, a first laser, and a second laser. The first laser is used to generate the probe light, and the second laser is used to generate the coupling light. The probe light and the coupling light are respectively incident on the cesium atomic gas cell from both ends in opposite directions, and the light beams of the probe light and the coupling light incident on the cesium atomic gas cell overlap with each other in the cesium atomic gas cell.

[0050] In some embodiments, the atomic excitation module further includes a half-wave plate, a frequency stabilization module, and a polarization beam splitter (PBS). The probe light generated by the first laser is transmitted through the half-wave plate to the polarization beam splitter, and the polarization beam splitter separates the probe light into two beams. One beam of the probe light is incident on the cesium atomic gas cell for related operations such as atomic excitation; the other beam of the probe light is incident on the frequency stabilization module. The frequency stabilizer in the frequency stabilization module detects the frequency of this beam of probe light, compares its frequency with a preset reference frequency, generates a feedback control signal according to the frequency deviation, and transmits this signal to the frequency control unit of the first laser. By adjusting the relevant parameters of the laser (such as cavity length, injection current, etc.), the frequency of the probe light generated by the first laser is indirectly adjusted to keep it stable near the target frequency value. The coupling light generated by the second laser is transmitted through the half-wave plate to the polarization beam splitter, and the polarization beam splitter separates the coupling light into two beams. One beam of the probe light is incident on the cesium atomic gas cell for related operations such as atomic excitation; the other beam of the coupling light is incident on the frequency stabilization module. The frequency stabilizer in the frequency stabilization module detects the frequency of this beam of coupling light, compares its frequency with a preset reference frequency, generates a feedback control signal according to the frequency deviation, and transmits this signal to the frequency control unit of the second laser. By adjusting the relevant parameters of the laser (such as cavity length, injection current, etc.), the frequency of the probe light generated by the second laser is indirectly adjusted to keep it stable near the target frequency value.

[0051] In some embodiments, the frequency stabilization module locks the wavelength of the probe light using the saturated absorption spectroscopy method and locks the wavelength of the coupling light by detecting the EIT spectrum.

[0052] In some embodiments, the spectral analysis module includes a photodetector, an oscilloscope, and a signal processor. When the frequency hopping sequence irradiates the cesium atomic system in the Rydberg state, the probe light passing through the cesium atomic system sequentially passes through the photodetector, the oscilloscope, and the signal processor, so as to extract the baseband signal according to the change in the transmittance of the probe light. Among them, the photodetector is used to detect the change in the intensity of the probe light passing through the cesium atomic system. Since the transmittance of the probe light changes with the change of the frequency hopping sequence, the current output by the photodetector will also change accordingly, thereby converting the change in the light intensity of the probe light into a change in an electrical signal. The oscilloscope is used to display and analyze the time-domain waveform of the electrical signal output by the photodetector. By analyzing the level change of the electrical signal collected by the oscilloscope, the original baseband signal information can be restored.

[0053] In some embodiments, the receiving end further includes an optical path regulation device, which includes a reflector, a first dichroic mirror, and a second dichroic mirror. The first dichroic mirror is arranged at one end close to the first laser for regulating the optical path of the probe light incident on the cesium atomic cell. The first dichroic mirror reflects the probe light and transmits the coupling light. The second dichroic mirror is arranged at one end close to the second laser for regulating the optical path of the coupling light incident on the cesium atomic cell. The second dichroic mirror reflects the coupling light and transmits the probe light. The reflector is arranged on the optical path of the probe light passing through the cesium atomic system to the photodetector for regulating the optical path of the probe light passing through the cesium atomic system.

[0054] Exemplary embodiment In this example, the device includes: an 852 nm laser, a 509 nm laser, a cesium atomic cell, an analog signal source, a horn antenna, a photodetector, and various spatially separated optical path devices such as dichroic mirrors and highly reflective mirrors. A probe light with a wavelength of 852 nm and a coupling light with a wavelength of 509 nm act on the atomic cell in opposite directions and overlap in cesium vapor, exciting the atoms from the ground state to the Rydberg state. At the transmitting end, the baseband signal controls carrier signals of different frequencies and encodes time slots, and the signal is fed to the atomic cell by the horn antenna. At the receiving end, the receiving and reading of the baseband signal are realized by using the response characteristics of Rydberg atoms to resonant and non-resonant carriers.

[0055] The specific implementation steps are as follows: Step 1: In this application, a cesium atomic four-level system is used as an atomic antenna to receive frequency-hopping signals. The relevant experimental device is as Figure 1 shown. A probe light with a wavelength of 852 nm and a coupling light with a wavelength of 509 nm act on a cylindrical atomic cell with a diameter of 1 cm and a length of 5 cm in opposite directions and overlap in cesium vapor. Among them, the diameter of the probe light spot is 300 , and the power is 250 . Its frequency is locked to the D2 transition line of → through saturated absorption spectroscopy; the diameter of the coupling light spot is 300 , and the power is 60 . The coupling light scans between → to form a three-level system. The energy level diagram is as Figure 2 , and the generated EIT spectrum is as Figure 3 shown by the curve without loading waves. Figure 2 In , taking the energy level as the initial state, carrier signals with frequencies of 12.53 GHz, 13.41 GHz, 14.28 GHz, and 15.21 GHz are respectively combined with the atomic energy level 66P1 / 2 、66P 3 / 2 、65P 3 / 2 、65P 1 / 2 Resonance. Taking the carrier wave of 15.21 GHz as an example, after the carrier signal is radiated to the Rydberg cell through the horn antenna, the EIT spectrum generates an AT splitting. As shown in the Figure 3 loading wave curve, at this time, the transmittance at the EIT peak decreases. Through theoretical calculation, the relationship between the transmittance of the EIT peak and the carrier electric field strength is as shown in Figure 4 , and the two show a non-linear negative correlation.

[0056] Step 2: ① Frequency encoding: Select the above resonance frequency as the channel F0, and at the same time select far-off resonance frequencies, that is, non-resonance frequencies: 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, 18 GHz, as the channel F1. The baseband signal encodes the carrier wave. For the k-th frequency hopping period, when the information is 1, the k-th frequency of the channel F1 is selected, otherwise the k-th frequency of the F0 is selected. Specifically, it is . No modulation is required. The data is sent by controlling the carrier frequency hopping through the baseband information. Among them, the carrier power is set to -8 dBm, the number of frequency points in the frequency hopping frequency set is 10, and the frequency hopping rate is 1 kbps. ② Time slot encoding: Each transmission time slot T is evenly divided into two sub-time slots. Taking the k-th frequency hopping period as an example, the first sub-time slot is , and the second is . For time slot selection, a group of pseudo-random sequences are locally generated to control the frequency hopping time slots of each hop , when selecting the first sub-time slot, when selecting the second sub-time slot, thus completing the time slot encoding of the frequency hopping.

[0057] Step 3: Generate a frequency hopping sequence after time-frequency encoding the carrier wave, and input it into an analog signal source with frequency hopping function, and radiate it to the cesium atomic cell through the horn antenna. The frequency hopping pattern is as shown in Figure 5 , both the time slot and the frequency are irregular, similar to white noise, and it is difficult to be intercepted and decoded, so it has strong concealment.

[0058] Step 4: At the receiving end of the atomic antenna, after observing the EIT spectrum, lock the coupling light frequency at zero detuning, i.e., the frequency where the EIT peak is located. The probe light is output through a photodetector to an oscilloscope, and the signal displayed on the oscilloscope is collected in real time. Since the transmittance of the EIT peak is relatively high when a non-resonant frequency carrier signal is applied, while applying a resonant frequency carrier will cause AT splitting and reduce the transmittance, the relative change in transmittance reflects the high and low levels of the baseband signal. After signal acquisition, a digital signal is obtained through simple threshold decision. In each time slot, if there is no carrier frequency in a certain sub-time slot, the transmittance of the EIT spectrum remains unchanged, approximating the non-resonant frequency response. Therefore, when making a decision in each time slot, if there are low levels in two sub-time slots, it is digital 0, otherwise it is digital 1, thus completing the reception of the baseband signal.

[0059] Since Rydberg atoms only respond to resonant and near-detuned frequency signals and far-detuned frequency signals with relatively high power, while signals of other frequencies, i.e., partial frequency bands or signals with relatively low power, have little impact on Rydberg atoms, it has a certain ability to resist partial frequency band interference. At the same time, for tracking interference, if the resonant frequency signal is detected and the interfering party implements a signal of the same frequency for tracking interference, in this time slot, the Rydberg atoms will not only not be interfered but will generate stronger AT splitting due to the relatively high power, resulting in a decrease in transmittance and increasing the probability of being detected by the receiver; if a non-resonant frequency signal is detected and the interfering party interferes with the same frequency with a certain power, the frequency shift of the EIT spectrum is very small, the transmittance of the EIT peak remains almost unchanged, and the interference at non-resonant frequency points has little impact. Therefore, the time-frequency multi-dimensional coding frequency hopping receiving method based on Rydberg atoms proposed in this application has a certain ability to resist tracking interference.

[0060] In summary, the time-frequency multi-dimensional coding frequency hopping receiving method based on Rydberg atoms in this application is simple and easy to implement. It can achieve multi-frequency point frequency hopping communication reception without carrier synchronization at the receiving end. This application can effectively enhance the concealment of communication, and can resist partial frequency band interference and certain tracking interference. Compared with traditional receivers, it reduces the complexity of the system, and at the same time enhances the flexibility and stability of frequency hopping communication.

[0061] The above-described implementation examples are only examples of this application, and are not only used to limit the protection scope of this application. It should be noted that for those of ordinary skill in the art in this technical field, several equivalent deformations and substitutions can be made based on the content disclosed in this application. The frequency and number of carriers, modulation methods, energy levels of atoms, etc. can all be changed. These equivalent deformations, substitutions, and adjustments of the frequency range should also be regarded as the protection scope of this application.

Claims

1. A time-frequency multi-dimensional coding frequency-hopping communication method based on Rydberg atoms, characterized in that Including: Using probe light to excite a cesium atom system from the ground state to an intermediate excited state, and using coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state; Based on the energy levels of the cesium atom system in the Rydberg state, determining the resonance frequency and non-resonance frequency of the carrier wave, and selecting the carrier wave with the resonance frequency or non-resonance frequency according to the binary state of the baseband signal for time-frequency coding to generate a frequency-hopping sequence; Radiating the frequency-hopping sequence to the cesium atom system in the Rydberg state, and receiving the spectral signal of the transmittance of the probe light passing through the cesium atom system to complete the reception of the baseband signal.

2. The time-frequency multi-dimensional coded frequency hopping communication method according to claim 1, wherein The wavelength of the probing light is 852 nm, and the probing light excites the cesium atomic system from the ground state to the intermediate excited state 6P 3 / 2 .

3. The time-frequency multi-dimensional coded frequency hopping communication method according to claim 1, characterized in that The wavelength of the coupled light is 509 nm, and the coupled light excites the cesium atom system from an intermediate excited state to the Rydberg state 66S 1 / 2 .

4. The time-frequency multi-dimensional coded frequency-hopping communication method according to claim 1, wherein Taking the resonance frequency as the first channel and the non-resonance frequency as the second channel. In each time slot, when the baseband signal represents a first preset logical value, the carrier selects the frequency point of the first channel; when the baseband signal represents a second preset logical value, the carrier selects the frequency point of the second channel. Combining time slot selection to achieve time-frequency coding of the carrier by the baseband signal.

5. The time-frequency multi-dimensional coding frequency-hopping communication method according to claim 4, wherein The time slot selection includes: generating a set of pseudo-random sequences locally, and using the timing information corresponding to each element in the pseudo-random sequences to control the start and end time slots of each hop period of the carrier frequency hopping.

6. The time-frequency multi-dimensional coded frequency hopping communication method according to claim 1, characterized in that The resonance frequency includes one or more of 12.53 GHz, 13.41 GHz, 14.28 GHz, and 15.21 GHz.

7. The time-frequency multi-dimensional coding frequency-hopping communication method according to claim 1, characterized in that The non-resonance frequency includes one or more of 7 GHz, 8 GHz, 9 GHz, 10 GHz, 17 GHz, and 18 GHz.

8. A time-frequency multi-dimensional coding frequency-hopping communication device based on Rydberg atoms, characterized in that Including a transmitter and a receiver; The transmitter includes an analog signal source and a coding module. The analog signal source is used to generate carriers of different frequencies, and the coding module is used to perform time-frequency coding on the carrier according to the baseband signal to generate a frequency-hopping sequence; The receiver includes an atomic excitation module and a spectral analysis module. The atomic excitation module is used to generate probe light to excite a cesium atom system from the ground state to an intermediate excited state, and generate coupling light to excite the cesium atom system from the intermediate excited state to the Rydberg state; the spectral analysis module is used to receive the probe light passing through the cesium atom system in the Rydberg state when the frequency-hopping sequence is radiated, and analyze the spectral signal to extract the baseband signal.

9. The time-frequency multi-dimensional coded frequency-hopping communication device according to claim 8, wherein The transmitter further includes a horn antenna, and the horn antenna radiates the frequency-hopping sequence to the cesium atom system in the Rydberg state of the receiver.

10. The time-frequency multi-dimensional coded frequency-hopping communication device according to claim 8, wherein The atomic excitation module includes a cesium atomic gas cell, a first laser, and a second laser. The first laser is used to generate the probe light, and the second laser is used to generate the coupling light. The probe light and the coupling light are respectively incident on the cesium atomic gas cell from both ends in opposite directions, and the light beams of the probe light and the coupling light incident on the cesium atomic gas cell coincide with each other in the cesium atomic gas cell.

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