Rydberg atom AT split signal-based closed-loop locking detection method and system
By using a closed-loop lock-in detection method based on the Rydberg atom AT splitting signal, and utilizing frequency switching and a lock-in amplifier to generate an error voltage signal, a real-time dynamic measurement of microwave electric fields with high precision, high speed, and high anti-interference capability is achieved, solving the problems of low efficiency and poor stability in existing technologies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NAT SPACE SCI CENT CAS
- Filing Date
- 2026-04-15
- Publication Date
- 2026-05-12
AI Technical Summary
Existing technologies struggle to achieve high-precision, high-speed, and high-interference-resistant real-time dynamic measurement of microwave electric fields, especially in the accurate detection and stable locking of AT split signals, where there are problems such as low efficiency, large human error, and poor stability.
A closed-loop locking detection method based on the Rydberg atom AT splitting signal is adopted. By establishing a frequency reference under microwave field-free conditions, the error voltage signal is generated by frequency switching of the coupled laser and lock-in amplifier. Combined with a servo controller, the zero-crossing point of the AT splitting peak is locked, and the microwave electric field intensity is calculated through feedback control.
It significantly improves measurement accuracy and anti-interference capability, achieves millisecond-level dynamic response speed, eliminates human error, and ensures the reliability and repeatability of measurement results.
Smart Images
Figure CN122017374A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of quantum precision measurement and automatic control technology, and in particular to a closed-loop locking detection method and system based on the Rydberg atom AT splitting signal. Background Technology
[0002] Due to their enormous electric dipole moments, Rydberg atoms exhibit extremely high sensitivity to microwave electric fields, making electric field measurement techniques based on the electromagnetically induced transparency (EIT) and Autler-Townes (AT) splitting effects of Rydberg atoms a cutting-edge research area in quantum precision measurement. Autler-Townes (AT) splitting refers to the phenomenon where energy levels of atoms split under the influence of a strong resonant electromagnetic field.
[0003] However, accurate detection and stable locking of this AT split signal has always been a technical challenge. Current mainstream methods include: Manual scanning method: By manually adjusting the frequency of the coupled laser, the entire AT split spectrum is slowly scanned, and the positions of the two peaks are recorded before calculating the frequency difference (split distance). This method is inefficient, cannot achieve real-time measurement, and is heavily dependent on the operator's experience, which can easily introduce human error and has poor repeatability.
[0004] Automatic peak locking method: This method uses analog circuits or software algorithms to directly lock the peak value of the AT split signal. Although it achieves automation, this method has inherent drawbacks: First, it has a poor signal-to-noise ratio, as directly locking the amplitude of the signal makes it highly sensitive to laser intensity noise, low-frequency beam drift, and other amplitude noise. Second, it has low locking accuracy, as the derivative of signal intensity with respect to frequency change (i.e., the slope) approaches zero near the peak point of the spectrum, leading to fuzzy locking points and limiting the sensitivity and accuracy of frequency tracking. Finally, it has poor stability, as any factor causing fluctuations in light intensity will directly translate into drift of the frequency locking point.
[0005] And a method to improve the sensitivity of microwave electric field amplitude measurement: This method obtains the EIT-AT spectrum dispersion signal of the probe light frequency by amplitude modulation of the microwave field to be measured. At this time, two zero-crossing points will appear on the dispersion signal. By measuring the distance between the zero-crossing points of the dispersion signal, the intensity of the microwave electric field can be obtained. However, this method only scans and does not achieve closed-loop locking of the AT split signal.
[0006] Therefore, there is an urgent need to propose a method to meet the requirements of real-time dynamic measurement of microwave electric fields with high precision, high speed, and high anti-interference capability. Summary of the Invention
[0007] The purpose of this application is to overcome the shortcomings of existing technologies in meeting the requirements for high-precision, high-speed, and high anti-interference capabilities in real-time dynamic measurement of microwave electric fields, thereby providing a closed-loop locking detection method and system based on Rydberg atom AT splitting signals with high measurement accuracy, fast response speed, and strong anti-interference capability.
[0008] To solve the above-mentioned technical problems, the technical solution of this application provides a closed-loop locking detection method based on Rydberg atom AT splitting signal, comprising: Electromagnetically induced transparent EIT signals are acquired under microwave field-free conditions, and the frequency of the coupled laser output from the coupled laser is locked at a preset reference point to establish a frequency reference. The coupled laser and the probe laser emitted by the probe laser are combined and pass collinearly through the gas cell, and the microwave field to be measured is applied. When the microwave field to be measured is applied to the gas cell to cause the atomic energy level to split into AT, the frequency of the coupled laser is controlled by the laser frequency shifter to switch between two preset target frequencies. A lock-in amplifier is used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path, an error voltage signal is generated based on the AT split signal, and the error voltage signal is fed back to the servo controller. The servo controller outputs a control signal to lock the system at the error voltage zero-crossing point corresponding to the two AT split peaks, and records the feedback control quantity that maintains the two locking points. The intensity of the microwave electric field to be measured is calculated based on the difference in feedback control values between the two locking points.
[0009] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the preset reference point is the frequency position corresponding to the peak value of the electromagnetically induced transparent EIT signal under microwave field-free conditions.
[0010] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the laser frequency shifter is driven by a sine wave generated by a driver.
[0011] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the preset target frequency point is the frequency position corresponding to the peak value of the two AT splitting signals.
[0012] According to the closed-loop locking detection method based on the Rydberg atom AT splitting signal of the present invention, the error voltage signal is a zero-crossing point at the frequency position of the peak of the AT splitting signal, and has a voltage-frequency slope near the zero-crossing point.
[0013] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the servo controller is a digital PID servo controller.
[0014] The present invention also provides a laser, comprising: a probe laser and a coupling laser, for emitting a probe laser and a coupling laser; A laser frequency shifter is disposed in the optical path of the coupled laser to lock the frequency of the coupled laser emitted by the coupled laser at a preset reference point to establish a frequency reference. After applying the microwave field to be measured to generate AT splitting, the laser frequency shifter controls the frequency of the coupled laser to switch between preset target frequency points. Microwave antenna, used to apply microwave field to the gas chamber; A dichroic mirror, including a first dichroic mirror and a second dichroic mirror, is used to combine the probe laser and the coupling laser beams and pass them through a gas cell; The gas chamber is used to contain Rydberg atoms; A photodetector is used to receive the detection laser light after it passes through the gas chamber and output a photoelectric signal. An input signal selection module, connected to the photodetector, is used to input photoelectric signals to two lock-in amplifiers; Two lock-in amplifiers are used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path and generate corresponding error signals respectively; Two servo controllers are connected to the two lock-in amplifiers respectively, and are used to generate control signals based on the corresponding error signals; Two frequency source modules are connected to the two servo controllers respectively, and are used to output frequency-adjustable drive signals under the control of the corresponding servo controllers; An output signal selection module, connected to the two frequency source modules, is used to select a drive signal and output it to the driver. A driver, connected to a laser frequency shifter, is used to generate a sinusoidal signal to drive the laser frequency shifter; The electric field strength calculation module is used to calculate the measured microwave electric field strength based on the control values of two locked points; and The central controller is used to coordinate the system's operation and calculate the microwave electric field strength.
[0015] Compared with the closest prior art, the beneficial effects of this invention include: Significantly improved measurement accuracy: By utilizing the high slope characteristics of the error signal near the zero crossing point, the system is extremely sensitive to minute frequency changes, improving the accuracy and sensitivity of frequency locking by one to two orders of magnitude.
[0016] The anti-interference capability is greatly enhanced: the phase-sensitive detection technology of the lock-in amplifier itself has a strong narrowband suppression capability, which can effectively filter out wideband noise that is not at the same frequency as the reference signal; at the same time, the zero-crossing locking strategy is not sensitive to the fluctuation of laser amplitude, thus overcoming the main weakness of the traditional peak locking method, enabling the system to work stably in complex experimental environments.
[0017] Faster dynamic response: Closed-loop feedback control combined with a time-division scanning strategy enables the system to track rapid changes in the microwave electric field with a response speed on the order of milliseconds, achieving true real-time dynamic measurement.
[0018] Fully automated and highly reliable: The entire measurement process requires no human intervention, eliminating human error and ensuring the objectivity, repeatability, and high reliability of the measurement results. Attached Figure Description
[0019] Figure 1 The diagram shown is a structural principle block diagram of the system of the present invention; Figure 2(a) shows the signal evolution of the AT split spectrum; Figure 2(b) shows the signal evolution of the zero-crossing characteristics of the error signal; Figure 3 The diagram shown is a structural principle block diagram based on AOM modulation. Figure 4 The diagram shown is a structural principle block diagram based on laser driving current modulation. Detailed Implementation
[0020] The technical solutions provided in this application are further illustrated below with reference to the embodiments.
[0021] Example 1 A method for locking the AT splitting signal of a Rydberg atomic electric field meter is proposed. Its core lies in the innovative use of modulation and phase-sensitive detection techniques to transform the difficult-to-lock signal peak characteristics into easily lockable error signal zero-crossing characteristics. The method includes the following steps: S1: Frequency reference establishment The frequency of the coupled laser is stabilized near an atomic level transition reference point. This step establishes a stable frequency reference for subsequent precise measurements. As a preferred implementation, this can be achieved by locking onto the peak value of the EIT signal in the absence of a microwave field.
[0022] S2: Time-sharing frequency switching After applying the microwave field to be measured, a frequency scan measurement of the coupled laser is first performed. During this scan, the frequency of the coupled laser varies within a certain range. After observing the AT splitting phenomenon, the approximate values of two preset target frequencies are recorded. The coupled laser is controlled by an acousto-optic modulator (AOM) so that its frequency switches rapidly and alternately between the two preset target frequencies under the control of a periodic signal. These two target frequencies correspond to the vicinity of the peak values of the two AT splitting signals, respectively.
[0023] The AT splitting phenomenon affects the transmission intensity of the probe laser, which is then converted into a voltage signal by a photoelectric detection unit (such as a photodiode) for detection.
[0024] In the Rydberg atomic system, when a coupled laser and a probe laser act simultaneously on an atom and the resonance condition is met, electromagnetically induced transparency (EIT) occurs, increasing the transmittance of the probe laser. When a microwave electric field (i.e., the electric field to be measured) is applied and induces Autler-Townes (AT) splitting between Rydberg states, the single EIT peak splits into two peaks. This is directly manifested as a specific change in the transmittance (intensity) of the probe laser through the atomic medium with frequency scanning—from a single peak to a double-peak structure.
[0025] The positions of the two peaks in the AT split (i.e., the desired laser frequency) are strongly dependent on the frequency and intensity of the microwave field being measured. Different microwave fields will cause peak position shifts. Therefore, it is impossible to use a fixed set of historical data to handle all measured fields. Frequency scanning measurements are designed to adaptively track changing microwave fields.
[0026] In this embodiment, the laser frequency shift module is implemented using an acousto-optic modulator (AOM), such as... Figure 3 As shown. In other embodiments, other devices or methods capable of changing the laser frequency can also be used to achieve the same performance as an acousto-optic modulator (AOM), such as directly modulating the laser's drive current, like... Figure 4 As shown, to implement the method described in this application.
[0027] S3: Error Signal Generation A lock-in amplifier is used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path. Through this key technical step, the lock-in amplifier converts the peak (amplitude) information of the AT split signal into an error voltage signal. The significant characteristic of this error signal is that it crosses zero (voltage is zero) at the precise frequency position of each AT split peak, and has an extremely high voltage-frequency slope near the zero-crossing point.
[0028] In scanning observation mode, the lock-in amplifier does not enable phase-sensitive detection. The central controller records an approximate value of the peak value of the EIT-AT signal (photoelectric) signal. The approximate value can be approximated using the peak detection method.
[0029] In locked operating mode, the central controller generates two signals: a frequency perturbation signal and a lock-up switching signal. The frequency perturbation signal serves as a reference signal for the lock-in amplifier (LIA) at the same frequency. The lock-up switching signal is used to switch the input signal to the LIA (e.g., by using a signal selection switch or enabling the LIA), thus achieving time-division locking.
[0030] S4: Alternating closed-loop locking The error signal generated in step S3 is fed back to the servo controller (such as a PID controller) that controls other components of the AOM. Based on the magnitude and polarity of the error signal, the servo controller outputs a control signal to adjust the driving frequency of the other components of the AOM, with the control objective of keeping the error signal close to zero. Since the coupled laser frequency alternates between two frequencies, the servo controller alternately and independently locks the system at the zero-crossing points of the error signals corresponding to the two AT splitting peaks, thus achieving alternating closed-loop locking at two points.
[0031] S5: Electric Field Intensity Calculation Record the feedback control quantity required to maintain these two lock points (e.g., the control quantity applied to the RF voltage or frequency of the AOM drive source). Record the difference in this control quantity (e.g., voltage difference). Or frequency difference) and the frequency difference between the two AT split peaks (i.e., AT split distance) Proportional to () , (These are pre-calibrated coefficients). Finally, based on the Rydberg atom energy level structure theory, the AT split is determined. The intensity of the microwave electric field to be measured can be calculated directly.
[0032] Example 2 A closed-loop locking detection method based on Rydberg atom AT splitting signal includes: Electromagnetically induced transparent EIT signals are acquired under microwave field-free conditions. The frequency of the coupled laser is locked at a preset reference point to establish a frequency reference. After the applied microwave field generates AT splitting, the frequency of the coupled laser is switched between preset target frequencies by adjusting the laser drive current. The transmission intensity signal of the probe laser path is phase-sensitively detected using a lock-in amplifier. An error voltage signal is generated based on the AT splitting signal and fed back to the servo controller. The servo controller outputs a control signal to lock the system at the error voltage zero-crossing points corresponding to the two AT splitting peaks. The feedback control quantities that maintain the two locking points are recorded. The intensity of the microwave electric field to be measured is calculated based on the difference between the feedback control quantities of the two locking points.
[0033] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the preset reference point is the frequency position corresponding to the peak value of the electromagnetically induced transparent EIT signal under microwave field-free conditions.
[0034] According to the closed-loop locking detection method based on Rydberg atom AT splitting signal of the present invention, the preset target frequency point is the frequency position corresponding to the peak value of the two AT splitting signals.
[0035] According to the closed-loop locking detection method based on the Rydberg atom AT splitting signal of the present invention, the error voltage signal is a zero-crossing point at the frequency position of the peak of the AT splitting signal, and has a voltage-frequency slope near the zero-crossing point.
[0036] According to the closed-loop locking detection method based on the Rydberg atom AT splitting signal of the present invention, the laser driving current modulation is driven by a sine wave generated by the driver.
[0037] In the closed-loop locking detection method based on the Rydberg atom AT splitting signal of the present invention, the sine wave is the reference signal of the lock-in amplifier.
[0038] According to the closed-loop locking detection method based on the Rydberg atom AT splitting signal of the present invention, the frequency of the sine wave is 2kHz and the time constant of the lock-in amplifier is 1ms.
[0039] In the closed-loop locking detection method based on Rydberg atom AT splitting signal according to the present invention, the servo controller is a digital PID servo controller.
[0040] Example 3 A closed-loop locking detection system based on Rydberg atom AT splitting signal, used to execute the method described in any of the above embodiments, includes: Photodetector: used to acquire electromagnetically induced transparent EIT signals under microwave field-free conditions; Laser frequency shifter: used to lock the frequency of the coupled laser at a preset reference point to establish a frequency reference. After applying the microwave field to be measured to generate AT splitting, the frequency of the coupled laser is controlled by an acousto-optic modulator to switch between preset target frequency points. Lock-in amplifier: used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path, generate an error voltage signal based on the AT split signal, and feed the error voltage signal back to the servo controller; Servo controller: Used to output control signals to lock the system at the zero-crossing points of the error voltage corresponding to the two AT split peaks; and Electric field strength calculation module: Records the feedback control values that maintain two locking points, and calculates the strength of the microwave electric field to be measured based on the difference between the feedback control values of the two locking points.
[0041] According to the closed-loop locking detection system based on Rydberg atom AT splitting signal of the present invention, the lock-in amplifier includes: a first lock-in amplifier and a second lock-in amplifier, which are used to generate error voltage signals corresponding to the two AT splitting peaks, respectively.
[0042] According to the Rydberg atom AT splitting signal closed-loop locking detection system of the present invention, the laser frequency shifter is an acousto-optic modulator used to modulate the frequency of the coupled laser.
[0043] Example 4 This embodiment uses cesium atoms as a quantum medium to further illustrate the technical solution provided in this application.
[0044] like Figure 1 As shown, the detector outputs a laser with a wavelength of 852 nm, corresponding to cesium atoms from... arrive The transition energy level; the coupled-optical laser outputs a laser with a wavelength of 510 nm, corresponding to the transition energy level from... arrive The Rydberg state transition occurs. Two laser beams are combined by a dichroic mirror and then collinearly pass through a 75mm long cesium atom gas cell. An acousto-optic modulator with a center frequency of 110MHz is placed in the coupled laser path. The transmission intensity of the probe laser is received by a photodetector. The AOM is driven by a 2kHz sine wave signal generated by a frequency source to introduce a small-amplitude frequency jitter, resulting in a frequency offset used by the lock-in amplifier to extract the error signal. The signal output from the photodetector is fed into the lock-in amplifier, whose reference input is synchronized with the aforementioned sine wave signal. The output of the lock-in amplifier (X channel) is connected to a digital PID servo controller, whose output is ultimately fed back to the AOM's RF driver, forming a closed loop.
[0045] The specific operating steps are as follows: 1. Initial Frequency Stabilization: Without applying a microwave field, the frequency of the coupled laser is scanned to obtain a typical EIT signal. The Pound-Drever-Hall (PDH) frequency-locking technique is used to actively lock the frequency of the coupled laser at the peak of the EIT signal.
[0046] 2. Introduction of microwave field: A microwave field of about 7 GHz was applied to the atomic gas cell through a horn antenna, and it was observed that the single EIT peak split into two symmetrical AT split peaks, as shown in Figure 2(a).
[0047] 3. Configure the detection system: The function generator generates a 2kHz sine wave to drive the AOM and serve as the phase-locked loop reference signal; the time constant of the phase-locked loop amplifier is set to 1ms.
[0048] 4. Initiate alternating closed-loop locking: Enable PID control, and the 50Hz switching signal alternately locks the two AT peaks. The lock-in amplifier outputs the error signal in real time, as shown in Figure 2(b). The PID dynamically adjusts the AOM frequency to maintain the zero-crossing point of the error signal.
[0049] 5. Electric field calculation: Record the difference in AOM driving frequency. According to the formula (in For AT crack distance, is Planck's constant. The intensity of the microwave electric field to be measured was calculated using the Rydberg state. .
[0050] In summary, this invention, through a shift in locking strategy, changes from directly locking the peak amplitude to locking the zero-crossing point of the error signal generated by phase-sensitive detection. Utilizing the high slope characteristic of the zero-crossing point significantly improves locking accuracy and sensitivity. Through a time-division alternating locking mechanism, the laser frequency is controlled to switch rapidly near the two AT peaks. Combined with a single servo controller, synchronous and alternating closed-loop locking of the dual-peak signal is achieved, simplifying the system structure and ensuring data synchronization. Through dynamic anti-interference design, the narrow-band suppression characteristics of the lock-in amplifier, combined with the zero-crossing locking strategy insensitive to amplitude fluctuations, give the system extremely strong robustness against laser intensity noise and environmental interference.
[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application do not depart from the spirit and scope of the technical solutions of this application, and should all be covered within the scope of the claims of this application.
Claims
1. A closed-loop locking detection method based on Rydberg atom AT splitting signal, comprising: Electromagnetically induced transparent EIT signals are acquired under microwave field-free conditions, and the frequency of the coupled laser output from the coupled laser is locked at a preset reference point to establish a frequency reference. The coupled laser and the probe laser emitted by the probe laser are combined and pass collinearly through the gas cell, and the microwave field to be measured is applied. When the microwave field to be measured is applied to the gas cell to cause the atomic energy level to split into AT, the frequency of the coupled laser is controlled by the laser frequency shifter to switch between two preset target frequencies. A lock-in amplifier is used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path, an error voltage signal is generated based on the AT split signal, and the error voltage signal is fed back to the servo controller. The servo controller outputs a control signal to lock the system at the error voltage zero-crossing point corresponding to the two AT split peaks, and records the feedback control quantity that maintains the two locking points. The intensity of the microwave electric field to be measured is calculated based on the difference in feedback control values between the two locking points.
2. The AT split signal closed-loop locking detection method according to claim 1, characterized in that, The preset reference point is the frequency position corresponding to the peak value of the electromagnetically induced transparent EIT signal under microwave field-free conditions.
3. The AT split signal closed-loop locking detection method according to claim 1, characterized in that, The laser frequency shifter is driven by a sine wave generated by a driver.
4. The AT split signal closed-loop locking detection method according to claim 1, characterized in that, The preset target frequency point is the frequency position corresponding to the peak values of the two AT split signals.
5. The AT split signal closed-loop locking detection method according to claim 1, characterized in that, The error voltage signal has a zero-crossing point at the frequency position of the peak of the AT split signal, and has a voltage-frequency slope near the zero-crossing point.
6. The AT split signal closed-loop locking detection method according to claim 1, characterized in that, The servo controller is a digital PID servo controller.
7. A closed-loop locking detection system based on Rydberg atom AT splitting signal, used to execute the method described in any one of claims 1-6, characterized in that, include: Lasers, including probe lasers and coupling lasers, are used to emit probe lasers and coupling lasers, respectively. A laser frequency shifter is disposed in the optical path of the coupled laser to lock the frequency of the coupled laser emitted by the coupled laser at a preset reference point to establish a frequency reference. After applying the microwave field to be measured to generate AT splitting, the laser frequency shifter controls the frequency of the coupled laser to switch between preset target frequency points. A microwave antenna is used to apply a microwave field to the gas chamber. A dichroic mirror, including a first dichroic mirror and a second dichroic mirror, is used to combine the probe laser and the coupling laser beams and pass them through a gas cell; The gas chamber is used to contain Rydberg atoms; A photodetector is used to receive the detection laser light after it passes through the gas chamber and output a photoelectric signal. An input signal selection module, connected to the photodetector, is used to input photoelectric signals to two lock-in amplifiers; Two lock-in amplifiers are used to perform phase-sensitive detection on the transmission intensity signal of the probe laser path and generate corresponding error signals respectively; Two servo controllers are connected to the two lock-in amplifiers respectively, and are used to generate control signals based on the corresponding error signals; Two frequency source modules are connected to the two servo controllers respectively, and are used to output frequency-adjustable drive signals under the control of the corresponding servo controllers; An output signal selection module, connected to the two frequency source modules, is used to select a drive signal and output it to the driver. A driver, connected to a laser frequency shifter, is used to generate a sinusoidal signal to drive the laser frequency shifter; The electric field strength calculation module is used to calculate the measured microwave electric field strength based on the control values of two locked points; and The central controller is used to coordinate the system's operation and calculate the microwave electric field strength.