A broadband frequency-hopping device based on high orbital angular momentum Rydberg atoms

Abstract

This invention provides a broadband frequency hopping device based on high-orbit angular momentum Rydberg atoms. The atomic gas chamber contains high-orbit angular momentum Rydberg atoms. A first and second reflector reflect probe light and coupling light, respectively, back into the atomic gas chamber to excite the high-orbit angular momentum Rydberg atoms from their ground state to an excited state and pump them to a first Rydberg state. A first, second, and third microwave generator are used to transition the high-orbit angular momentum Rydberg atoms to a second, third, and fourth Rydberg state, respectively. A photodetector receives the probe light passing through the atomic gas chamber. This invention enables frequency hopping across six octaves at a hopping speed of 60 kHz / s and utilizes a microwave frequency comb to extend the number of hopping points within a limited instantaneous bandwidth. This invention has potential applications in the field of secure radio communication.

Description

Technical Field

[0001] This invention relates to the field of quantum communication technology, specifically to a broadband frequency hopping device based on high orbital angular momentum Rydberg atoms. Background Technology

[0002] Frequency-hopping communication is a technology that transmits signals by rapidly switching operating frequencies. Its importance lies primarily in its anti-interference, anti-interception, and enhanced communication confidentiality. Because the signal hops across multiple frequency points, it is difficult for the enemy to conduct sustained interference or eavesdropping, thus significantly improving the reliability and security of the communication system, playing an irreplaceable role, especially in military communications and wireless network security. However, the operating frequencies of frequency-hopping communication are constrained by spectrum resource allocation, hardware bandwidth limitations, and frequency bands stipulated by the International Telecommunication Union (ITU), limiting hopping to specific licensed frequency bands. This restricts its flexibility in spectrum-dense environments.

[0003] Furthermore, high-frequency hopping may be limited by the switching speed of radio frequency devices, while low-frequency bands may face problems such as spectrum congestion and increased interference. Therefore, the design of frequency hopping systems needs to strike a balance between frequency range, hopping rate, and regulatory restrictions. Currently existing frequency hopping communication schemes implemented with low orbital angular momentum (OAM) Rydberg atoms can only achieve communication in the 3-15 GHz frequency band, which is relatively limited. Summary of the Invention

[0004] The purpose of this invention is to provide a broadband frequency hopping device based on high orbital angular momentum Rydberg atoms, capable of frequency hopping across six octaves at a hopping speed of 60 khops / s, and utilizing a microwave frequency comb to extend the number of hopping points within a limited instantaneous bandwidth. This invention has potential application value in the field of secure radio communication.

[0005] To achieve the above objectives, this utility model provides a broadband frequency-hopping device based on high-orbit angular momentum Rydberg atoms. The receiver includes an atomic gas cell, a probe light emitter, a coupling light emitter, a first microwave generator, a second microwave generator, a third microwave generator, a first reflector, a second reflector, and a photodetector. The atomic gas cell contains high-orbit angular momentum Rydberg atoms with principal quantum number n > 10 and angular quantum number l ≥ 3. The first and second reflectors are used to reflect the probe light emitted by the probe light emitter and the coupling light emitted by the coupling light emitter back to the atomic gas cell, respectively, to excite the high-orbit angular momentum Rydberg atoms from their ground state to an excited state and pump them to a first Rydberg state. The probe light and the coupling light propagate in opposite directions after being reflected. The first, second, and third microwave generators are used to generate a first, second, and third microwave field, respectively, to cause the high-orbit angular momentum Rydberg atom to transition to a second, third, and fourth Rydberg state. The photodetector is used to receive the probe light passing through the atomic gas cell and convert the optical signal induced by the interaction between the high-orbit angular momentum Rydberg atom and the microwave into an electrical signal. The first and second microwave generators are microwave horns, configured to face the atomic gas cell at a 45° angle from both sides. The third microwave generator is a parallel electric dipole plate, and the applied microwave field is perpendicular to the plane containing the microwave fields generated by the first and second microwave generators, as well as the reflected probe light and the coupled light.

[0006] Preferably, the frequencies of the first microwave field, the second microwave field, and the third microwave field are 29.737 GHz, 1.772 GHz, and 315 MHz, respectively.

[0007] Preferably, the ground state is 6S. 1 / 2 The excited state is 6P. 3 / 2 The first Rydberg state is 48D. 5 / 2 The second Rydberg state is 46F. 7 / 2 The third Rydberg state is 46G. 9 / 2 The fourth Rydberg state is 46H. 11 / 2 .

[0008] Preferably, the first microwave field, the second microwave field, and the third microwave field are microwave frequency combs of 29.735 GHz to 29.739 GHz, 1.7718 GHz to 1.7722 GHz, and 313 MHz to 317 MHz, respectively, with a frequency interval of 1 MHz.

[0009] Preferably, the probe light is an 852nm laser, and the coupling light is a 510nm laser.

[0010] Preferably, the device is capable of receiving microwave signals spanning 6 octaves, with a frequency hopping speed of 60 khops / s, and uses the microwave frequency comb to extend the frequency hopping point to a resonant frequency of ±5 MHz.

[0011] Through the above technical solution, the broadband frequency hopping device based on a high orbital angular momentum Rydberg atom provided in this embodiment of the invention can achieve frequency hopping across 6 octaves at a hopping speed of 60 khops / s, and expands the number of hopping points within a limited instantaneous bandwidth by utilizing a microwave frequency comb. This invention has potential application value in the field of secure radio communication.

[0012] Other features and advantages of this utility model embodiment will be described in detail in the following detailed description section. Attached Figure Description

[0013] The accompanying drawings are provided to further illustrate the embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0014] Figure 1 This is a schematic diagram of the structure of a broadband frequency hopping device based on Rydberg atoms with high orbital angular momentum provided in an embodiment of this utility model;

[0015] Figure 2 This is a schematic diagram of atomic transition energy levels provided in an embodiment of the present invention;

[0016] Figure 3 This is a schematic diagram of the rising edge test direct modulation bandwidth and sinusoidal modulation response provided in one embodiment of the present invention;

[0017] Figure 4 This is a schematic diagram of frequency hopping of a signal field in a monotonic local field according to an embodiment of the present invention;

[0018] Figure 5 This is a schematic diagram of the Stark calibration field strength and calibration curve provided in one embodiment of the present invention;

[0019] Figure 6 This is a schematic diagram of the microwave frequency comb results and signal strength as the measurement results of the signal microwave provided in an embodiment of the present invention;

[0020] Figure 7 This is a schematic diagram of frequency hopping of a signal field with a frequency comb-shaped local field provided in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures

[0022] 1-Atomic gas cell, 2-Detector light emitter, 3-Coupled light emitter, 4-First microwave generator, 5-Second microwave generator, 6-Third microwave generator, 7-First reflector, 8-Second reflector, 9-Photodetector Detailed Implementation

[0023] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the scope of the present invention.

[0024] Figure 1 This is a schematic diagram of a broadband frequency-hopping device based on Rydberg atoms with high orbital angular momentum, provided in one embodiment of this utility model. Figure 1 As shown, the receiver includes an atomic gas chamber 1, a probe light emitter 2, a coupling light emitter 3, a first microwave generator 4, a second microwave generator 5, a third microwave generator 6, a first reflector 7, a second reflector 8, and a photodetector 9. The atomic gas chamber 1 contains high-orbit angular momentum Rydberg atoms with principal quantum number n > 10 and angular quantum number l ≥ 3. The first reflector 7 and the second reflector 8 are respectively used to reflect the probe light emitted by the probe light emitter 2 and the coupling light emitted by the coupling light emitter 3 back to the atomic gas chamber 1, thereby reflecting the high-orbit angular momentum Rydberg atoms. Rydberg atoms are excited from their ground state to an excited state and pumped to a first Rydberg state, wherein the probe light and the coupling light are reflected and propagate in opposite directions; the first microwave generator 4, the second microwave generator 5, and the third microwave generator 6 are used to generate a first microwave field, a second microwave field, and a third microwave field, respectively, to cause the high orbital angular momentum Rydberg atoms to transition to the second Rydberg state, the third Rydberg state, and the fourth Rydberg state; the photodetector 9 is used to receive the probe light passing through the atomic gas cell and convert the optical signal induced by the interaction between the high orbital angular momentum Rydberg atoms and the microwaves into an electrical signal.

[0025] In one embodiment, the first microwave generator 4 and the second microwave generator 5 are microwave horns, positioned at a 45° angle from both sides of the atomic gas chamber. The third microwave generator 6 is a parallel electric dipole plate, and the applied microwave field is perpendicular to the plane containing the microwave fields generated by the first microwave generator 4 and the second microwave generator 5, as well as the reflected probe light and coupling light. This allows for good consistency in the polarization of the three microwave beams reaching the atom while saving space. The cesium atomic gas chamber is square, with dimensions of 2.5cm × 2.5cm × 2.5cm, and the ambient temperature is 22 degrees Celsius.

[0026] Figure 2 This is a schematic diagram of atomic transition energy levels provided in one embodiment of this utility model. (See diagram below.) Figure 2 As shown, cesium atoms are excited from the ground state 6S by 852 nm probe light (beam waist radius 180 μm, Rabi frequency 15.6 × 2π MHz). 1 / 2 To the excited state 6P 3 / 2 The transition occurs, followed by pumping to the first Rydberg state 48D with 510nm coupling light (beam waist radius 220μm, Rabi frequency 1.85×2π MHz). 5 / 2 Two microwave speakers were used to input 29.74 GHz (MW1) and 1.772 GHz (MW2) at a 45° angle, respectively, and a vertical electric field (MW3) was applied through parallel brass electric dipole plates, causing the atom to transition to the second Rydberg state of 46F. 7 / 2 The third Ridburg state is 46G. 9 / 2 The fourth Ridburg state is 46H. 11 / 2 The microwave electric field intensity was measured using the AT splitting effect.

[0027] The following is a series of experimental verifications of the broadband frequency hopping device for high orbital angular momentum Rydberg atoms of this invention.

[0028] High-orbital-angular-momentum Rydberg atoms can directly respond to radio-frequency (RF) field changes through Otler-Towns (AT) level splitting. By applying a square-wave AM-modulated local RF electric field with a modulation frequency of 1 kHz, the atom's response is as follows: Figure 3 The direct modulation bandwidth of the rising edge test is shown in section (a). The rise time is 2.44 μs, corresponding to an instantaneous response bandwidth of 140 kHz. Figure 3 Part (b) shows the sinusoidal modulation response of the system at a modulation frequency of 1 kHz to sinusoidal AM modulated RF fields of different depths, where the modulation depths are 20%, 40%, 60%, 80% and 99% ERF, respectively.

[0029] Frequency hopping experiments were conducted using a broadband frequency hopping device based on high orbital angular momentum Rydberg atoms. Three different frequency bands of microwave signals were modulated by square waves with a period of 100 μs, such as... Figure 4 Part (a) shows the timing sequence of the signal field. The frequency and envelope variations of the microwave signal response to the heterodyne signal in the atomic system are illustrated. The local microwave frequencies in the three bands are 29.737 GHz, 1.772 GHz, and 315 MHz, respectively, while the signal microwave frequencies are 29.73712 GHz, 1.7721 GHz, and 315.08 MHz, respectively. The response results of the signal microwave and the corresponding reference microwave at intermediate frequencies of 120 kHz, 100 kHz, and 80 kHz are shown in [reference]. Figure 4 The time-related transmission signal jump field in section (b) is shown. With timing disabled, the frequency distribution of the three intermediate frequency signals in the analysis spectrum can be seen, as follows... Figure 4The Fourier spectra of panel (b) in section (c) are shown. This demonstrates that leveled communication from 350 MHz to 30 GHz can be achieved using the high-orbit Rydberg atoms of this invention.

[0030] High-orbit Rydberg atoms were used to measure real microwave field strength. The 315.05 MHz microwave field strength sensed by the EIT calibrator atoms in the 6s→6p→55D state was measured using the Stark method. As the output of the microwave signal under test increases, the energy level frequency shift caused by the Stark effect gradually increases, as shown in [reference needed]. Figure 5 The Stark calibration field strength is shown in section (a). This represents the magnitude of the energy level frequency shift caused by the AC Stark effect. The relationship with the microwave electric field intensity E is as follows: (1)

[0031] For the 55D state, its maximum polarizability α0 = -2.811 × 10 3 MHz cm 2 / V 2 According to formula (1), the electric field strength at the atom's location obtained through Stark frequency shift has a linear relationship with the output power of the signal source. The experimental results are shown in the calibration curve. Figure 5 The calibration curve is shown in section (b). The error bars are obtained by taking the standard deviation of five measurements. The black line represents the linear fitting result with the intercept at 0 for the data points. The fitting formula is E = k·P, and the fitting coefficient k is 17.1812. This formula can be used to obtain the relationship between the true field strength and the output power of the signal source. It is evident that the high-orbit Rydberg atomic antenna can be used to measure the true microwave field strength and detect changes in the microwave field.

[0032] In another embodiment of this utility model, a microwave frequency comb can be used to widen the frequency range of microwave frequency hopping. That is, the first microwave field, the second microwave field, and the third microwave field are microwave frequency combs of 29.735 GHz to 29.739 GHz, 1.7718 GHz to 1.7722 GHz, and 313 MHz to 317 MHz, respectively, with a frequency interval of 1 MHz. This can expand the number of frequency hopping points of the system when the instantaneous bandwidth of the system is limited.

[0033] A microwave frequency comb is a microwave field composed of a series of equally spaced, highly stable discrete frequencies, similar to a comb in the frequency domain. Using a microwave frequency comb as intrinsic microwaves helps improve the instantaneous bandwidth of a receiving system. In the time domain, the waveform of the frequency comb can be represented as a superposition of a series of phase-coherent single-frequency microwave signals, expressed as: (2)

[0034] in, Our experimental conditions are as follows: The starting frequency, For frequency intervals, A n Let N = 20 be the amplitude of the nth frequency comb tooth, covering 310–320 MHz, for a total of 21 frequency points. We will output the waveform generated by formula (2) through an arbitrary waveform generator 1652B, and display it in frequency space as a comb composed of a series of Dirac delta functions (discrete spectral lines) using a spectrometer, such as... Figure 6 The results of the microwave frequency comb are shown in section (a). Measurements were performed by averaging 100 measurements at an RBW of 10 kHz. Replacing the intrinsic microwave in the original high-orbit experiment with this frequency comb, the power of a single comb tooth was evaluated to be approximately 0.624 V / m. The signal microwave output remained around -45 dBm, at which point the measurable frequency range was extended to ±5 MHz compared to using a monochromatic 315 MHz microwave as the intrinsic field. (See section (a)). Figure 6 The signal strength in part (b) is shown as the measurement result of the signal microwave, but the signal-to-noise ratio drops by about 24 dB.

[0035] In actual measurements, multiple frequency components exist. The experiment uses the intermediate frequency (IF) signal strength between the closest frequency comb teeth and the signal frequency in each measurement as the measured value. Using frequency combs can broaden the frequency range of microwave frequency hopping because more frequency combinations can provide frequency references and amplification for unknown signal microwaves. We demonstrated a multi-tone microwave frequency hopping experiment as local microwaves, with each band containing five frequency combs (frequency ranges of 29.735 GHz to 29.739 GHz, 1.7718 GHz to 1.7722 GHz, and 313 MHz to 317 MHz, with a frequency interval of 1 MHz). The multi-tone local microwaves drive the transition of atoms from the 48D state to the 46H state, while simultaneously providing a reference for the frequency hopping signal. See [link to relevant documentation]. Figure 7 A sketch of the local field of the frequency comb in section (a) is shown. The microwave signal still undergoes frequency hopping via timing control, but after every 100 µs cycle, the microwave frequency jumps back to the original band, but increases by 1 MHz. Here, δs is the frequency detuning between each resonant frequency comb tooth and the signal field, as shown... Figure 7 The timing sequence of the signal field in section (b) is shown. Figure 7 In the time-related transmission section (c), when multi-tone modulation is disabled, the frequency-hopping results show that no frequency-hopping microwave signal was observed except for the intermediate frequency signal close to the resonant local frequency, because the differential frequency exceeds the instantaneous bandwidth of our system, 140kHz. After enabling multi-tone modulation, we can observe... Figure 7The middle (d) section shows the time-dependent transmission and each frequency-hopping signal in the local frequency comb region. This demonstrates that the frequency comb, acting as a local reference microwave, provides a wider operating bandwidth for frequency-hopping experiments. A microwave frequency comb with 21 teeth (single tooth field strength 0.624 V / m) spaced 500 kHz and 310–320 MHz was generated using an arbitrary waveform generator. The signal under test was mixed with the comb teeth to extend the bandwidth to ±5 MHz while reducing the signal-to-noise ratio by 24 dB. The instantaneous bandwidth of the system was 200 kHz. In the embodiment, single-frequency measurements (315 MHz intrinsic field, 315.05 MHz signal) demonstrated high sensitivity, while the frequency comb application (310–320 MHz) verified the broadband detection capability.

[0036] This invention enables simultaneous measurement at 315 MHz and nearly 30 GHz using high OAM conditions, achieves frequency hopping across six octaves at a hopping speed of 60 khops / s, and utilizes a microwave frequency comb to extend the number of hopping points within a limited instantaneous bandwidth, with a resonant frequency of ±5 MHz. This invention has potential applications in the field of secure radio communications.

[0037] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0038] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A wideband frequency hopping device based on high orbital angular momentum Rydberg atoms, characterized in that, It includes an atomic gas chamber, a probe light emitter, a coupling light emitter, a first microwave generator, a second microwave generator, a third microwave generator, a first reflector, a second reflector, and a photodetector, wherein: The atomic chamber contains high orbital angular momentum Rydberg atoms with principal quantum number n > 10 and angular quantum number l ≥ 3; The first reflector and the second reflector are respectively used to reflect the probe light emitted by the probe light emitter and the coupling light emitted by the coupling light emitter to the atomic gas cell, so as to excite the high orbital angular momentum Rydberg atom from the ground state to the excited state and pump it to the first Rydberg state, wherein the probe light and the coupling light propagate in opposite directions after being reflected; The first microwave generator, the second microwave generator, and the third microwave generator are used to generate a first microwave field, a second microwave field, and a third microwave field, respectively, to cause the high orbital angular momentum Rydberg atom to transition to a second Rydberg state, a third Rydberg state, and a fourth Rydberg state. The photodetector is used to receive the probe light passing through the atomic gas cell and convert the optical signal induced by the interaction between the high orbital angular momentum Rydberg atom and microwaves into an electrical signal. The first microwave generator and the second microwave generator are microwave horns, configured to face the atomic gas chamber from both sides at a 45° angle. The third microwave generator is a parallel electric dipole plate, and the applied microwave field is perpendicular to the microwave field generated by the first microwave generator and the second microwave generator, as well as the plane containing the reflected probe light and coupling light.

2. The wideband frequency hopping device based on high orbital angular momentum Rydberg atoms of claim 1, wherein, The frequencies of the first microwave field, the second microwave field, and the third microwave field are 29.737 GHz, 1.772 GHz, and 315 MHz, respectively.

3. The wideband frequency hopping apparatus based on high orbital angular momentum Rydberg atoms of claim 1, wherein, The ground state is 6S. 1 / 2 The excited state is 6P. 3 / 2 The first Rydberg state is 48D. 5 / 2 The second Rydberg state is 46F. 7 / 2 The third Rydberg state is 46G. 9 / 2 The fourth Rydberg state is 46H. 11 / 2 .

4. The broadband frequency hopping device based on high orbital angular momentum Rydberg atoms according to claim 1, characterized in that, The first microwave field, the second microwave field, and the third microwave field are microwave frequency combs of 29.735 GHz to 29.739 GHz, 1.7718 GHz to 1.7722 GHz, and 313 MHz to 317 MHz, respectively, with a frequency interval of 1 MHz.

5. The wideband frequency hopping apparatus based on high orbital angular momentum Rydberg atoms of claim 1, wherein, The detection light is an 852nm laser, and the coupling light is a 510nm laser.

6. The wideband frequency hopping apparatus based on high orbital angular momentum Rydberg atoms of claim 4, wherein, The device is capable of receiving microwave signals across 6 octaves with a frequency hopping speed of 60 khops / s. It uses the microwave frequency comb to extend the frequency hopping point to a resonant frequency of ±5 MHz.

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