Method and system for locking clock transition frequency of ytterbium ion optical clock
By determining the initial frequency of the ytterbium ion clock with the same frequency spacing between the frequency at both ends, the state of the ions is judged and the transition probability is calculated, and the laser frequency is adjusted using the feedback signal, the problem of difficulty in stably locking the laser frequency is solved, and a higher accuracy is achieved. Frequency locking and photoclock performance improvements.
Patent Information
- Application Number
- CN202411449995.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-02-18
AI Technical Summary
The prior art has shortcomings in long-term stability, making it difficult to achieve stable locking of laser frequency to the transition frequency of ytterbium ion clock, and cannot meet the needs of higher accuracy.
By determining the first and second frequency at the same interval between the initial frequency and the frequency at both ends, the state of the ions is determined, the transition probability between the first frequency and the second frequency is determined, and the laser frequency is adjusted through the feedback signal to lock it to The center of the clock transition spectrum line of the ytterbium ion photoclock.
The laser frequency is stable locked on the transition frequency of the ytterbium ion photoclock, improving the overall performance and frequency stability of the photoclock.
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Figure CN119481926A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of ion optical clocks, and in particular to a method and system for locking the transition frequency of an ytterbium ion optical clock. Background Art
[0002] 171 ytterbium + Ion optical clock locks the laser frequency to the ion transition energy level, thereby obtaining a stable laser frequency output. 171 ytterbium + The energy level structure is simple, and the energy level of the fourth-level clock transition is 2 S 1 / 2 (F = 0) → 2 D 3 / 2 (F = 2), the natural line width is about 3Hz, which belongs to m F = 0 → m F = 0 transition, is insensitive to magnetic field and is not easily affected by the external magnetic field environment. 171 ytterbium + Ions have a large mass and strong anti-interference ability.
[0003] In order to accurately lock the frequency of the laser, the current frequency locking method mainly relies on the Pound-Drever-Hall (PDH) frequency stabilization technology, which can achieve good short-term stability by locking the laser frequency to the ultra-stable cavity. However, there are still deficiencies in long-term stability, which needs further improvement to meet the needs of higher precision.
[0004] By locking the laser frequency to the ion transition frequency, a clock laser frequency output with good frequency stability and uncertainty can be obtained. Therefore, a method and system for locking the ytterbium ion optical clock transition frequency that can achieve rapid frequency locking is needed. Summary of the invention
[0005] The embodiments of the present application provide a method and system for locking the transition frequency of an ytterbium ion optical clock, which solves the problem that the laser frequency is difficult to stably lock on the ion clock transition frequency.
[0006] In a first aspect, an embodiment of the present application provides a method for locking the frequency of an ytterbium ion optical clock transition, comprising the steps of: Determine the initial frequency of the laser and the first frequency and the second frequency with the same frequency interval at both ends; The laser frequency is fixed at the first frequency or the second frequency to perform clock transition to determine the state of the ions; determining a transition probability between a first frequency and a second frequency; The transition probability comparison result of the first frequency and the second frequency is used as an input signal to determine a feedback signal to adjust the laser frequency.
[0007] In one embodiment, the input signal is used to calculate the feedback signal through a PID control algorithm. The coefficients of the PID control algorithm include a proportional coefficient, an integral coefficient and a differential coefficient.
[0008] In one embodiment, determining the state of the ions specifically comprises the steps of: Acquire a detection signal of a first frequency or a second frequency clock transition; determining a threshold voltage, the detection signal being compared with the threshold voltage; When the detection signal is greater than the threshold voltage, the ion is in the ground state; when the detection signal is less than the threshold voltage, the ion is in the clock transition state.
[0009] In one embodiment, determining the transition probability of the first frequency or the second frequency comprises the following steps: The clock transition is performed a set number of times for the first frequency or the second frequency, and the probability of the ion being in the clock transition state is calculated as the transition probability.
[0010] In one embodiment, the method further comprises the steps of: By adjusting the feedback signal, the frequency of the clock laser is locked to the center of the clock transition spectral line of the ytterbium ion optical clock.
[0011] In a second aspect, an embodiment of the present application further provides an ytterbium ion optical clock transition frequency locking system, comprising: a clock laser module, a frequency control module, an ion trap module, a fluorescence collection module and a data processing module. The clock laser module is used to send a laser signal. The ion trap module is used to receive the laser signal and interact with the ytterbium ion. The fluorescence collection module is used to detect the interaction between the laser signal and the ytterbium ion and generate a detection signal; the data processing module is used to analyze the detection signal and send a feedback signal. The frequency control module is used to receive the feedback signal to adjust the frequency of the laser signal sent by the clock laser module.
[0012] In one embodiment, the data processing module includes: a data acquisition unit, a PID feedback control unit and a signal output unit. The data acquisition unit is used to determine the initial frequency of the laser and the first frequency and the second frequency with the same frequency interval at both ends; and is also used to compare the transition probability of the first frequency and the second frequency. The PID feedback control module is used to receive the comparison result of the transition probability of the first frequency and the second frequency, and determine the feedback signal for adjusting the laser frequency. The signal output unit is used to send the feedback signal to the frequency control module.
[0013] Furthermore, the PID feedback control module receives a comparison result of the transition probabilities of the first frequency and the second frequency, adjusts the proportional coefficient, integral coefficient and differential coefficient of the PID, and outputs a feedback signal.
[0014] In one of the embodiments, a timing control module is also included, which is used to control the status of instruments and equipment at different times according to the set timing.
[0015] In one embodiment, the fluorescence collection module uses PMT to collect the fluorescence signal of the detection light.
[0016] At least one of the above technical solutions adopted in the embodiments of the present application can achieve the following beneficial effects: The present application proposes an ytterbium ion optical clock laser frequency locking system, which ensures that the laser frequency is stable at the clock transition frequency by optimizing the locking technology and feedback control, thereby improving the overall performance of the optical clock. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 A flow chart of a method for locking the frequency of an ytterbium ion optical clock transition is provided for an embodiment of the present application; Figure 2 This is a flow chart of clock transition frequency locking in an embodiment of the present application; Figure 3 A structural diagram of an ytterbium ion optical clock transition frequency locking system is also provided for an embodiment of the present application. DETAILED DESCRIPTION
[0018] In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.
[0019] The technical solutions provided by various embodiments of the present application are described in detail below in conjunction with the accompanying drawings.
[0020] Example 1 Figure 1 A flow chart of a method for locking the frequency of an ytterbium ion optical clock transition is provided for an embodiment of the present application, comprising steps 110 to 140.
[0021] Step 110, determining an initial frequency of the laser and a first frequency and a second frequency with the same frequency interval at both ends; For example, the initial frequency of the clock laser is fixed to , by changing the initial frequency of the laser Point A and point B at both ends are explored, and the frequency interval of the two detection points is guaranteed to be the same.
[0022] The laser frequencies at points A and B can be expressed as the first frequency and the second frequency .
[0023] Step 120, the laser frequency is fixed at the first frequency or the second frequency to perform clock transition to determine the state of the ions; In one embodiment, in step 120, determining the state of the ions specifically comprises the steps of: Step 120-1, obtaining a detection signal of a first frequency or a second frequency clock transition; Step 120-2, determining a threshold voltage, and comparing the detection signal with the threshold voltage; Step 120 - 3 : If the detection signal is greater than the threshold voltage, the ion is in the ground state; if the detection signal is less than the threshold voltage, the ion is in the clock transition state.
[0024] For example, the laser frequency is fixed at a first frequency , clock transition, if the PMT detection signal is greater than or equal to the threshold voltage , indicating that the ion is in the ground state 2 S 1 / 2 If the PMT detection signal is less than the threshold voltage , indicating that the ion is in the clock transition state 2 D 3 / 2 superior.
[0025] Step 130: determining the transition probability between the first frequency and the second frequency; In one embodiment, in step 130, the transition probability of the first frequency or the second frequency is determined. Specifically, the steps include: Step 130 - 1 performs a set number of clock transitions on the first frequency or the second frequency, and calculates the probability of the ion being in the clock transition state as the transition probability.
[0026] The clock transition process is repeated multiple times, for example, a set number of times is determined, the clock transition is performed on the first frequency for more than the set number of times, and the transition probability P1 at the first frequency is calculated. The transition probability is the ratio of the number of times the ion is in the clock transition state to the total number of clock transitions when the clock transition is performed on the first frequency multiple times.
[0027] Fix the laser frequency at the second frequency and repeat the above process of calculating the transition probability of the first frequency. Calculate the transition probability P2 at the second frequency Step 140: The transition probability comparison result of the first frequency and the second frequency is used as an input signal to determine a feedback signal to adjust the laser frequency.
[0028] The transition probabilities of the first frequency and the second frequency are compared.
[0029] For example, if P2-P1>0, then increase , if P2-P1<0, then reduce .
[0030] In one embodiment, the input signal is used to calculate the feedback signal through a PID control algorithm. The coefficients of the PID control algorithm include a proportional coefficient, an integral coefficient and a differential coefficient.
[0031] According to the result of P2-P1, as the input signal of PID, the proportional coefficient kp, integral coefficient ki, differential coefficient kd in the PID control algorithm are adjusted to output a feedback signal u. The feedback signal is a control signal used to control the frequency of the clock laser.
[0032] In one embodiment, the method further comprises the steps of: Step 150: The frequency of the clock laser is locked to the center of the clock transition spectrum line of the ytterbium ion optical clock by adjusting the feedback signal.
[0033] The driving frequency of the AOM is controlled by feedback signal feedback, the frequency of the clock laser is adjusted, and the frequency is locked to the center of the clock transition spectrum line of the ytterbium ion optical clock.
[0034] Example 2 Figure 2 This is a flow chart of clock transition frequency locking in an embodiment of the present application.
[0035] In actual operation, first run the timing control system, use the program to open the timing file and read the timing file, so that the system works according to the preset state. Then fix the clock laser frequency to By changing the frequency of the laser Points A and B at both ends are explored, and the frequency interval between the two detection points is guaranteed. The laser frequencies at points A and B can be expressed as and The program flow chart is shown below. First, fix the laser frequency at , clock transition, if the PMT detection signal is greater than or equal to the threshold voltage , indicating that the ion is in the ground state 2 S 1 / 2 If the PMT detection signal is less than the threshold voltage , indicating that the ion is in the clock transition state 2 D 3 / 2 Repeat this process several times to obtain Further, the laser frequency is fixed at Repeat the above process to obtain The transition probability P2 at that time. According to the result of P2- P1, as the input signal of PID, the proportional coefficient kp, integral coefficient ki, differential coefficient kd in the PID control algorithm are adjusted, the output signal control signal u is used to feedback control the driving frequency of AOM, and the frequency of the clock laser is locked to the center of the clock transition spectrum line of the ytterbium ion optical clock.
[0036] The principle of driving frequency to adjust the clock laser frequency is: if P2- P1>0, then increase; if P2- P1<0, then decrease.
[0037] Figure 3 A structural diagram of an ytterbium ion optical clock transition frequency locking system is also provided for an embodiment of the present application, comprising: a clock laser module 210, a frequency control module 220, an ion trap module 230, a fluorescence collection module 240 and a data processing module 250.
[0038] The clock laser module is used to send laser signals.
[0039] For example, the clock laser module doubles the frequency of 871nm ultra-stable laser to obtain 436nm laser.
[0040] The ion trap module is used to receive laser signals and interact with ytterbium ions.
[0041] Since ions move in the trap, the ion trap module traps and cools the ions to keep them stably in the trap, preparing the ytterbium ion state so that the ytterbium ions are stably prepared to the ground state of the 436-clock transition energy level.
[0042] The fluorescence collection module is used to detect the interaction between the laser signal and the ytterbium ion to generate a detection signal.
[0043] For example, a clock laser emits a 436nm laser, which interacts with ions. At this time, another beam of light (detection light) is added to the ions for detection to determine whether the clock laser interacts with the ytterbium ions.
[0044] It should be noted that the interaction between the detection clock laser and the ytterbium ion depends mainly on whether the frequency of the clock laser resonates with the ytterbium ion. When the frequencies of the two are close or the same, resonance will occur, and resonance indicates that the frequency of this clock laser meets the requirements.
[0045] In one embodiment, the fluorescence collection module uses PMT to collect the fluorescence signal of the detection light.
[0046] For example, the fluorescence collection module uses a PMT to collect fluorescence signals of the detection light at 370 nm.
[0047] The data processing module is used to analyze the detection signal and send a feedback signal.
[0048] The data module receives the detection signal sent by the fluorescence collection module, that is, the signal detecting whether the frequency of the clock laser of the light detection resonates with the ytterbium ion.
[0049] In one of the embodiments, the data processing module includes: a data acquisition unit, a PID feedback control unit and a signal output unit.
[0050] The data acquisition unit is used to determine the initial frequency of the laser and the first frequency and the second frequency with the same frequency interval at both ends; and is also used to compare the transition probability of the first frequency and the second frequency.
[0051] For example, the acquisition card in the data acquisition unit acquires the PMT signal of the fluorescence collection module, and then uses the processing algorithm to analyze the acquired signal, and uses the processed data as the input signal of the PID control algorithm.
[0052] For example, the result of P2-P1 is used as the input signal of PID.
[0053] The PID feedback control module is used to receive a comparison result of the transition probabilities of the first frequency and the second frequency, and determine a feedback signal for adjusting the laser frequency.
[0054] Furthermore, the PID feedback control module receives a comparison result of the transition probabilities of the first frequency and the second frequency, adjusts the proportional coefficient, integral coefficient and differential coefficient of the PID, and outputs a feedback signal.
[0055] For example, adjust the proportional coefficient kp, integral coefficient ki, differential coefficient kd in the PID control algorithm, and output the feedback signal u.
[0056] The signal output unit is used to send a feedback signal to the frequency control module.
[0057] The signal output unit sends a feedback signal to the frequency control module, which feedback controls the driving frequency of the AOM and locks the frequency of the clock laser to the center of the clock transition spectrum line of the ytterbium ion optical clock.
[0058] The frequency control module is arranged between the clock laser module and the ion trap module, and is used to receive a feedback signal to adjust the frequency of the laser signal sent by the clock laser module.
[0059] For example, the frequency control module uses an acousto-optic modulator (AOM) to control the output frequency of a 436nm laser.
[0060] In one embodiment, a timing control module 260 is also included, which is used to control the status of instruments and equipment at different times according to the set timing.
[0061] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0062] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.
[0063] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.
Claims
1. A method for locking the frequency of an ytterbium ion optical clock transition, characterized in that: Contains steps: Determine the initial frequency of the laser and the first frequency and the second frequency with the same frequency interval at both ends; The laser frequency is fixed at the first frequency or the second frequency to perform clock transition to determine the state of the ions; determining a transition probability between a first frequency and a second frequency; The transition probability comparison result of the first frequency and the second frequency is used as an input signal to determine a feedback signal to adjust the laser frequency.
2. The method for locking the frequency of ytterbium ion optical clock transition according to claim 1, characterized in that: The input signal is calculated as a feedback signal through a PID control algorithm; The coefficients of the PID control algorithm include proportional coefficients, integral coefficients and differential coefficients.
3. The method for locking the frequency of ytterbium ion optical clock transition according to claim 1, characterized in that: Determine the state of the ion, including the following steps: Acquire a detection signal of a first frequency or a second frequency clock transition; determining a threshold voltage, the detection signal being compared with the threshold voltage; When the detection signal is greater than the threshold voltage, the ion is in the ground state; when the detection signal is less than the threshold voltage, the ion is in the clock transition state.
4. The method for locking the frequency of ytterbium ion optical clock transition according to claim 1, characterized in that: Determine the transition probability of the first frequency or the second frequency. Specifically comprising the steps: The clock transition is performed a set number of times for the first frequency or the second frequency, and the probability of the ion being in the clock transition state is calculated as the transition probability.
5. The method for locking the frequency of ytterbium ion optical clock transition according to claim 1, characterized in that: Also includes the steps: By adjusting the feedback signal, the frequency of the clock laser is locked to the center of the clock transition spectral line of the ytterbium ion optical clock.
6. An ytterbium ion optical clock transition frequency locking system, characterized in that: Contains: clock laser module, frequency control module, ion trap module, fluorescence collection module and data processing module; The clock laser module is used to send laser signals; The ion trap module is used to receive laser signals and interact with ytterbium ions; The fluorescence collection module is used to detect the interaction between the laser signal and the ytterbium ion to generate a detection signal; The data processing module is used to analyze the detection signal and send a feedback signal; The frequency control module is used to receive the feedback signal to adjust the frequency of the laser signal sent by the clock laser module.
7. The ytterbium ion optical clock transition frequency locking system according to claim 6, characterized in that: The data processing module comprises: a data acquisition unit, a PID feedback control unit and a signal output unit; The data acquisition unit is used to determine the initial frequency of the laser and the first frequency and the second frequency with the same frequency interval at both ends; and is also used to compare the transition probability of the first frequency and the second frequency; The PID feedback control module is used to receive a comparison result of the transition probabilities of the first frequency and the second frequency, and determine a feedback signal for adjusting the laser frequency; The signal output unit is used to send a feedback signal to the frequency control module.
8. The ytterbium ion optical clock transition frequency locking system according to claim 6, characterized in that: It also includes a timing control module, which is used to control the status of instruments and equipment at different times according to the set timing.
9. The Ytterbium ion optical clock transition frequency locking system according to claim 6, characterized in that: The fluorescence collection module uses PMT to collect the fluorescence signal of the detection light.
10. The ytterbium ion optical clock transition frequency locking system according to claim 7, characterized in that: The PID feedback control module receives the transition probability comparison result between the first frequency and the second frequency, adjusts the proportional coefficient, integral coefficient and differential coefficient of the PID, and outputs a feedback signal.