Atomic beam clock static magnetic field stabilizing method and device based on diatoms

Abstract

The invention relates to the field of atomic frequency standards, and provides a method and a device for stabilizing an atomic beam clock static magnetic field based on double atoms. A second atom is introduced on the basis of a traditional atomic beam clock, so that the two atoms act together in the same path and the same magnetic field, and a first atom is responsible for generating clock transition and serves as a main frequency reference; and the second atoms are specially used for static magnetic field stabilization. And periodically scanning the Ramsey pattern of the second atom to detect the change of the static magnetic field, and compensating according to the change so as to ensure that the static magnetic field is kept constant. The double atoms are in the same static magnetic field environment, so that when the static magnetic field of the second atom is stable, the static magnetic field of the first atom is also kept stable, and the frequency shift of the magnetic field is effectively eliminated. In the whole process, the locking loop of the first atom is always in a closed state, so that the adverse effect on the long-term stability caused by loop opening in a traditional method is avoided, and the long-term stability of the atomic beam clock is improved.

Description

Technical Field

[0001] This application relates to the field of atomic frequency standards. Specifically, it relates to a method and device for stabilizing the static magnetic field of an atomic beam clock based on dual atoms. Background Art

[0002] The content of this part only provides background information related to this application, which may not constitute prior art.

[0003] Atomic hyperfine level transitions have become an ideal choice for constructing reference signals due to their high precision and high stability, especially prominent in the application of atomic clocks. The working principle of an atomic clock is based on the spectral line of atomic hyperfine level transitions. Through a servo circuit, the output frequency of a voltage-controlled crystal oscillator is precisely locked onto this spectral line, thereby achieving a high-precision and stable signal output with the same frequency as the atomic transition frequency. However, although atomic hyperfine level transitions have a strong resistance to external interference, they are still affected by fluctuations in the temperature field, magnetic field, optical field, and microwave field around the atoms, resulting in a shift (frequency shift) of the atomic energy levels. This is a key factor affecting the frequency accuracy and long-term stability of atomic clocks.

[0004] To improve the performance of atomic clocks, reducing frequency shift is the core approach. Common types of frequency shifts include collision frequency shift, Doppler frequency shift, magnetic field frequency shift, and optical frequency shift, etc. Compared with atomic clocks using the "storage bubble" technology, the "atomic beam clock" using the "atomic beam" technology has significant advantages in reducing frequency shift. The atoms in an atomic beam clock freely move in a straight line in a vacuum, avoiding collisions between atoms, thus eliminating the collision frequency shift; at the same time, the direction of atomic travel is perpendicular to the propagation direction of the externally applied electromagnetic wave, effectively avoiding the Doppler effect and thus eliminating the Doppler frequency shift. Therefore, atomic beam clocks are superior in frequency accuracy and become primary frequency standards.

[0005] Magnetic field frequency shift stems from the slow change of the magnetic field around the atoms. To reduce magnetic field frequency shift and improve the accuracy and medium- to long-term stability of atomic beam clocks, two methods are usually used to stabilize the static magnetic field: one is to use a highly stable constant current source. Its advantage is that it does not interfere with the frequency control loop of the atomic beam clock, but its disadvantage is that it has extremely high requirements for the output current stability of the constant current source, with complex design and high cost, and is easily affected by minute changes in the environment, temperature, magnetic shielding, etc.; the other is to use dynamic servo technology. Through periodic open-loop scanning, using the relationship between the magnetic field strength sensed by the atoms and the difference in Ramsey transition frequencies, the output current of the magnetic field constant current source is dynamically adjusted to keep the magnetic field strength constant. The advantage of this method is that it fundamentally ensures the stability of the magnetic field strength and reduces the requirements for the magnetic field constant current source, but its disadvantage is that it will affect the long-term stability of the atomic clock during the open-loop process and introduces uncontrollable factors. Summary of the Invention

[0006] To solve the above technical problems, the purpose of this application is to provide a method and device for stabilizing the static magnetic field of an atomic beam clock based on two atoms. By using two atoms in the atomic beam clock, the first atom is used to generate clock transitions, and the second atom is used to stabilize the static magnetic field. Then, by scanning the Ramsey pattern of the second atom, changes in the static magnetic field are detected and compensated, so as to keep the static magnetic field unchanged. Utilizing the characteristic that the two atoms are in the same static magnetic field environment, the static magnetic field of the first atom also remains unchanged, thereby eliminating the magnetic field frequency shift.

[0007] The purpose of this application is achieved through the following technical solutions:

[0008] In the first aspect, the present invention provides a method for stabilizing the static magnetic field of an atomic beam clock based on two atoms, including:

[0009] Select two atoms, where the first atom of the first type is used as the atom for generating clock transitions, and the second atom of the second type is used as the atom for stabilizing the static magnetic field;

[0010] In the same path, a collinear two-atom beam containing the first atom and the second atom is generated in a heating furnace;

[0011] Perform atomic state preparation on the two-atom beam. Two pumping lights with different frequencies are emitted by a frequency-stabilized semiconductor laser light source, and the two pumping lights are set to vertically pass through the two-atom beam, so that the two pumping lights respectively undergo electric dipole resonance with the first atom and the second atom, so as to enable the first atom and the second atom to be respectively in their specific ground state hyperfine energy levels;

[0012] Inject the two-atom beam into a two-mode 0-phase-difference Ramsey cavity. Under the action of the static magnetic field, microwave field excitation of the ground state 0-0 hyperfine energy level transition frequencies of the first atom and the second atom is respectively performed according to the corresponding frequencies, so that the first atom and the second atom complete their respective microwave transitions;

[0013] Two detection lights with different frequencies are emitted by a frequency-stabilized semiconductor laser light source. The two detection lights vertically pass through the two-atom beam after microwave transition and respectively undergo electric dipole resonance with the first atom and the second atom;

[0014] The Ramsey resonance transition signals after the first atom and the second atom undergo microwave transitions and electric dipole resonance are received by a fluorescence collector, and the Ramsey resonance transition signal of the first atom is used as the clock transition signal; using the clock transition signal as the reference signal of the atomic beam clock, in the servo control system, the phase detector compares the phase of the clock transition signal and the voltage-controlled crystal oscillator signal to obtain the error signal of the voltage-controlled crystal oscillator; the error signal undergoes amplification and filtering processing through a loop filter to obtain a smooth control signal, and the voltage of the voltage-controlled crystal oscillator is controlled according to the control signal to adjust the frequency of the voltage-controlled crystal oscillator so that the frequency of the voltage-controlled crystal oscillator is consistent with the frequency of the clock transition signal;

[0015] During the operation of the atomic beam clock, the Ramsey resonance transition signal of the second atom is periodically scanned. By utilizing the characteristic that the static magnetic field strength is proportional to the difference between the two transition frequencies of the second atom, the difference between the two transition frequencies of the second atom is ensured to be constant by adjusting the static magnetic field current value, so as to achieve the stability of the static magnetic field.

[0016] Furthermore, the first atom is 87 Rb, and the second atom is 133 Cs.

[0017] In a second aspect, the present invention provides a static magnetic field stabilizing device for an atomic beam clock based on two atoms, which is applied to a static magnetic field stabilizing method for an atomic beam clock based on two atoms as described in the first aspect. The stabilizing device includes:

[0018] A cesium beam tube, on which there is a first optical window located between the heating furnace and the two-mode 0-phase-difference Ramsey cavity, and a second optical window located between the two-mode 0-phase-difference Ramsey cavity and the fluorescence collector; the first optical window is used to transmit the pumping light, and the second optical window is used to transmit the probing light;

[0019] A heating furnace, which is arranged inside the cesium beam tube. The output port of the heating furnace is provided with a collimation channel to generate a collinear two-atom beam containing the first atom and the second atom inside the heating furnace. The collinear two-atom beam is perpendicular to the pumping light;

[0020] A two-mode 0-phase-difference Ramsey cavity, which is arranged inside the cesium beam tube. The heating furnace, the two-mode 0-phase-difference Ramsey cavity, and the fluorescence collector are arranged in sequence collinearly. The collinear two-atom beam passes through the two-mode 0-phase-difference Ramsey cavity and reaches the fluorescence collector; outside the two-mode 0-phase-difference Ramsey cavity, there is a magnetic shielding cover, and inside the magnetic shielding cover, there is a magnetic field coil;

[0021] An electronics system, which includes a dual-frequency microwave source, a voltage-controlled crystal oscillator, a constant current source, and a servo control system; the two-mode 0-phase-difference Ramsey cavity, the dual-frequency microwave source, the voltage-controlled crystal oscillator, the servo control system, and the fluorescence collector are connected in sequence; the Ramsey resonance transition signal generated by the interaction between the two-atom beam after microwave transition and the probing laser is received by the fluorescence collector, and the Ramsey resonance transition signal of the first atom is used as the clock transition signal; in the servo control system, the clock transition signal is subjected to phase-sensitive detection to obtain the error signal of the voltage-controlled crystal oscillator; the two-mode 0-phase-difference Ramsey cavity is used to generate microwave fields of two frequencies; outside the two-mode 0-phase-difference Ramsey cavity, there is a magnetic shielding cover, and inside the magnetic shielding cover, there is a magnetic field coil, and the magnetic field coil is used to generate a static magnetic field, and the static magnetic field covers the collinear two-atom beam and enables the first atom and the second atom in the collinear two-atom beam to undergo ground-state 0-0 hyperfine level transitions according to the corresponding microwave frequencies;

[0022] A laser system, which includes a first frequency-stabilized semiconductor laser light source, a first half-wave plate + PBS combination, a first semi-transparent and semi-reflective mirror, a second half-wave plate + PBS combination, and a second semi-transparent and semi-reflective mirror; the laser emitted by the first frequency-stabilized semiconductor laser light source enters the first half-wave plate + PBS combination, and the first half-wave plate + PBS combination can continuously adjust the light intensity of the first frequency-stabilized semiconductor laser; the laser passing through the first half-wave plate + PBS combination enters the first semi-transparent and semi-reflective mirror, and the laser is divided into a first light beam and a second light beam; the first light beam serves as a first pumping light and passes through a first light window to intersect perpendicularly with a two-atomic beam; the second light beam enters the second half-wave plate + PBS combination, and the second half-wave plate + PBS combination can continuously adjust the light intensity of the second light beam; the laser passing through the second half-wave plate + PBS combination enters the second semi-transparent and semi-reflective mirror and serves as a first detection light, passing through the second light window to intersect perpendicularly with the two-atomic beam.

[0023] The laser system further includes a second frequency-stabilized semiconductor laser, a third half-wave plate + PBS combination, a third semi-transparent and semi-reflective mirror, a fourth half-wave plate + PBS combination, and a 45° reflector; the laser emitted by the second frequency-stabilized semiconductor laser enters the third half-wave plate + PBS combination, and the third half-wave plate + PBS combination can continuously adjust the light intensity of the second frequency-stabilized semiconductor laser; the laser passing through the third half-wave plate + PBS combination enters the third semi-transparent and semi-reflective mirror, and the laser is divided into a third light beam and a fourth light beam; the third light beam serves as a second pumping light and passes through the first light window to intersect perpendicularly with the two-atomic beam; the fourth light beam enters the fourth half-wave plate + PBS combination, and the fourth half-wave plate + PBS combination can continuously adjust the light intensity of the fourth light beam; the laser passing through the fourth half-wave plate + PBS combination enters the 45° reflector and serves as a second detection light, passing through the second light window to intersect perpendicularly with the two-atomic beam.

[0024] Further, it includes a graphite block, and the two-atomic beam passes through a fluorescence collector and enters the graphite block.

[0025] Further, the laser frequencies of the first pumping light and the first detection light are the same, and the laser frequencies of the second pumping light and the second detection light are the same.

[0026] Further, the first pumping light and the second pumping light are collinear, and the first detection light and the second detection light are collinear.

[0027] In a third aspect, the present invention provides an electronic device, including: a memory, a processor, and a computer program stored on the memory and executable on the processor, and when the processor executes the computer program, it implements the steps corresponding to the method in the first aspect.

[0028] Fourthly, the present invention provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, the steps corresponding to the method in the first aspect are implemented.

[0029] In summary, the technical solutions of the embodiments of the present application have at least the following advantages and beneficial effects:

[0030] By adopting the atomic beam clock scheme with a dual-atom design, the present invention introduces a second atom, which works in cooperation with the first atom originally used to generate clock transitions in the same path and the same magnetic field environment. The first atom generates clock transitions, while the second atom is used for static magnetic field stabilization. By scanning the Ramsey pattern of the second atom, the change of the static magnetic field can be accurately detected, and real-time compensation can be performed accordingly to ensure that the static magnetic field remains constant. Since the two atoms are in exactly the same static magnetic field environment, the influence of the static magnetic field on the first atom also remains unchanged, thus effectively eliminating the magnetic field frequency shift, which is an important factor affecting the accuracy of the atomic beam clock. By using this atomic beam clock with a dual-atom design, the locking loop of the first atom remains closed throughout the working process, successfully solving the problem that the loop may open during the detection of the change of the static magnetic field in the traditional scheme. The long-term stability of the atomic beam clock is improved. Description of the Drawings

[0031] Figure 1 It is a flowchart of a method for stabilizing the static magnetic field of an atomic beam clock based on dual atoms provided by the present invention;

[0032] Figure 2 It is a schematic structural diagram of a device for stabilizing the static magnetic field of an atomic beam clock based on dual atoms provided by the present invention;

[0033] Figure 3 For the atom 87 Atomic energy level diagram of Rb;

[0034] Figure 4 For the atom 133 Atomic energy level diagram of Cs;

[0035] Figure 5 For m F Ramsey pattern diagram corresponding to m = ±1.

[0036] Icons: 1. Cesium beam tube; 11. First optical window; 12. Second optical window; 2. Heating furnace; 21. Collimation channel; 3. Dual-mode 0-phase-difference Ramsey cavity; 31. Magnetic shielding cover; 32. Magnetic field coil; 4. Control system; 41. Dual-frequency microwave source; 42. Voltage-controlled crystal oscillator; 43. Constant current source; 44. Servo control system; 5. Fluorescence collector; 6. Graphite block; 7. Laser system; 71. First frequency-stabilized semiconductor laser light source; 711. Second frequency-stabilized semiconductor laser; 72. First half-wave plate + PBS combination; 73. First semi-transparent and semi-reflective mirror; 74. Second half-wave plate + PBS combination; 75. Second semi-transparent and semi-reflective mirror; 76. 45° reflector; 77. Fourth half-wave plate + PBS combination; 78. Third semi-transparent and semi-reflective mirror; 79. Third half-wave plate + PBS combination. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this application. Apparently, the described embodiments are some but not all of the embodiments of this application. Usually, the components of the embodiments of this application described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0038] Embodiment 1:

[0039] As Figure 1 shown, a method for stabilizing the static magnetic field of an atomic beam clock based on two atoms proposed in the embodiments of this application includes:

[0040] S101. Select two types of atoms, where the first type of atom is the first atom that generates clock transitions, and the second type of atom is the second atom used for stabilizing the static magnetic field. The first atom and the second atom can be combined in various ways. In this embodiment, the first atom is 87 Rb and the second atom is 133 Cs as an example for illustration; if the first atom is 133 Cs and the second atom is 87 Rb; if the first atom is 133 Cs and the second atom is 85 Rb, this patent is also equally applicable. The energy level diagram of the first atom 87 Rb is as Figure 3 shown, and its clock transition frequency f 1 is 6.8346875 GHz. The second atom 133 Cs, the energy level diagram is as Figure 3 shown, and the frequency difference shown in Figure 5 is used to stabilize the static magnetic field.

[0041] Specifically, the first atom and the second atom play different roles in subsequent processes: the first type of atom is selected as the first atom for generating clock transitions, while the second type of atom is used for static magnetic field stabilization. This step is set based on the characteristics of atomic hyperfine level transitions. An atomic clock uses the spectral line of atomic hyperfine level transitions as a reference signal, and through a servo circuit, locks the output frequency of a voltage-controlled crystal oscillator to the atomic hyperfine level transition spectral line, thereby achieving high-precision and high-stability signal output. However, this transition is still affected by the external environment, especially the magnetic field, resulting in frequency shift, which in turn affects the frequency accuracy and long-term stability of the atomic clock. To solve this problem, the present invention proposes an innovative method, that is, introducing a second atom to stabilize the static magnetic field.

[0042] S102. Under the same path, generate a collinear two-atom beam containing the first atom and the second atom in the heating furnace 2.

[0043] Specifically, by loading the two types of atoms in the same heating furnace 2 and ejecting them through the same collimation channel 21, it can be ensured that they travel along the same path to form a collinear two-atom beam. This enables the two types of atoms to be processed and detected in the same magnetic field environment, providing convenience for subsequent realization of static magnetic field stabilization and clock transition locking. Secondly, this method of generating a collinear two-atom beam not only simplifies the device structure but also helps to improve the stability and accuracy of the atomic beam clock. Because the two types of atoms are in the same physical environment, the interference and influence they receive are the same, which can be compensated and corrected through subsequent signal processing, thereby further improving the performance of the atomic beam clock.

[0044] S103. Perform atomic state preparation on the two-atom beam. By emitting two pumping lights with different frequencies from a frequency-stabilized semiconductor laser light source, set the two pumping lights to vertically pass through the two-atom beam, so that the two pumping lights respectively undergo electric dipole resonance with the first atom and the second atom, in order to enable the first atom and the second atom to be respectively in their specific ground state hyperfine energy levels.

[0045] Specifically, use a frequency-stabilized semiconductor laser light source to emit two pumping lights with different frequencies, and these two pumping lights are set to vertically pass through the already formed collinear two-atom beam. Since 87 Rb and 133 Cs two types of atoms have different energy level structures (as shown in Figure 3 and 4 ), and transition frequencies, therefore, by precisely adjusting the frequencies of these two pumping lights, they can be respectively made to resonate with 87 Rb and 133The Cs atoms undergo an electric dipole resonance. Electric dipole resonance is an effective means of preparing atomic states. It can excite atoms from their initial states to specific excited states and then return to specific ground state hyperfine energy levels through processes such as spontaneous emission. Additionally, since both types of atoms are prepared to specific energy levels, their responses to the external environment become more consistent and predictable, which is beneficial for subsequent signal processing and error correction, thereby further improving the stability and accuracy of the atomic beam clock.

[0046] S104, Inject the dual-atom beam into the dual-mode 0-phase-difference Ramsey cavity 3. Under the action of the static magnetic field, microwave field excitations for the ground state 0-0 hyperfine level transition frequencies are applied to the first atom and the second atom respectively according to their corresponding frequencies, causing the first atom and the second atom to complete their respective microwave transitions. Among them, 87 Rb undergoes a microwave transition under microwave magnetic field excitation at the clock transition frequency f 1 ≈6.8346875 GHz; 133 Cs undergoes a microwave transition under microwave magnetic field excitation at the clock transition frequency f 2 ≈9.192631770.

[0047] Specifically, after the preparation of the dual-atom beam and the precise control of the atomic states are completed, step S104 further advances the realization process of the atomic beam clock, specifically involving introducing the dual-atom beam into the dual-mode 0-phase-difference Ramsey cavity 3 for microwave field excitation. First, the dual-atom beam (containing 87 Rb and 133 Cs atoms) is injected into the dual-mode 0-phase-difference Ramsey cavity 3. This cavity is designed to accommodate and process both types of atoms while ensuring that they can undergo transitions in the same static magnetic field environment.

[0048] Inside the Ramsey cavity, for 87 Rb and 33 Cs atoms, microwave field excitations are applied respectively according to their respective corresponding frequencies. The frequencies of these microwave fields are precisely regulated to match the frequencies of the ground state 0-0 hyperfine level transitions of the two types of atoms. The role of the microwave field is to excite the atoms from their ground states to a short-lived excited state, and then the atoms spontaneously emit radiation back to another ground state, forming the so-called Ramsey interference fringes. Thus, the transition frequencies of the two types of atoms can be measured with high precision, providing an accurate reference signal for the frequency locking of the atomic clock; at the same time, since both types of atoms undergo transitions in the same static magnetic field environment, the dependence of their transition frequencies on the magnetic field becomes consistent, which is beneficial for subsequent monitoring and stabilizing the static magnetic field by comparing the transition frequencies of the two types of atoms, thereby further improving the long-term stability and frequency accuracy of the atomic beam clock.

[0049] S105. Two probe lights with different frequencies are emitted by a frequency-stabilized semiconductor laser source. The two probe lights vertically pass through the diatomic beam after microwave transition and respectively generate electric dipole resonance with the first atom and the second atom.

[0050] Specifically, a frequency-stabilized semiconductor laser source emits two probe lights with different frequencies, and the two probe lights are set to vertically pass through the diatomic beam that has completed microwave transition. The frequencies of the probe lights can be precisely adjusted by modulating the frequency-stabilized semiconductor laser source to generate electric dipole resonance with the atomic energy levels after transition. When the probe light resonates with the atom, the atom will absorb photons and transition from its current energy level to a higher energy level, which will cause a change in the intensity of the probe light. By monitoring the change in the intensity of the probe light, we can indirectly understand the state and quantity of atomic transitions, and further analyze to obtain the frequency information of the atomic clock.

[0051] S106. The Ramsey resonance transition signals after the first atom and the second atom undergo microwave transition and electric dipole resonance are collected by the fluorescence collector 5, and the Ramsey resonance transition signal of the first atom is used as the clock transition signal; the clock transition signal is used as the reference signal of the atomic beam clock; in the servo control system 44, the phase detector compares the phase of the clock transition signal and the signal of the voltage-controlled crystal oscillator 42 to obtain the error signal of the voltage-controlled crystal oscillator 42; the error signal is amplified and filtered by the loop filter to obtain a smooth control signal, and the voltage of the voltage-controlled crystal oscillator 42 is controlled according to the control signal to adjust the frequency of the voltage-controlled crystal oscillator 42 to make the frequency of the voltage-controlled crystal oscillator 42 consistent with the frequency of the clock transition signal.

[0052] Specifically, the fluorescence collector 5 receives the diatomic beam after microwave transition and electric dipole resonance. In this process, the fluorescence collector 5 can capture the fluorescence signals emitted by the atoms during the transition, and these signals contain the key information of the atomic clock transition. Then, the system extracts the clock transition signal from these fluorescence signals, and this signal is used as the reference signal of the atomic beam clock, with extremely high frequency stability and accuracy.

[0053] To convert this reference signal into an actual clock output, the phase detector in the servo control system 44 is further utilized to compare the clock transition signal with the signal generated by the voltage-controlled crystal oscillator 42. This comparison process can accurately measure the phase difference between the signal of the voltage-controlled crystal oscillator 42 and the clock transition signal, namely the error signal. The magnitude and direction of the error signal reflect the deviation between the frequency of the voltage-controlled crystal oscillator 42 and the frequency of the clock transition signal. To precisely adjust the frequency of the voltage-controlled crystal oscillator 42, the error signal is fed into a loop filter for amplification and filtering. The role of the loop filter is to smooth the error signal to eliminate noise and interference while maintaining the accuracy of the signal. The filtered control signal is used to adjust the control voltage of the voltage-controlled crystal oscillator 42, thereby achieving precise adjustment of the frequency of the voltage-controlled crystal oscillator 42.

[0054] Finally, by continuously adjusting the control voltage of the voltage-controlled crystal oscillator 42, the frequency of the voltage-controlled crystal oscillator 42 gradually approaches the frequency of the clock transition signal, thereby achieving high stability and high-precision output of the atomic beam clock.

[0055] S107. During the operation of the atomic beam clock, the Ramsey resonance transition signal of the second atom is periodically scanned. Utilizing the characteristic that the static magnetic field strength is proportional to the difference between the two transition frequencies of the second atom, the difference between the two transition frequencies of the second atom is ensured to remain unchanged by adjusting the static magnetic field current value, so as to achieve the stability of the static magnetic field.

[0056] Specifically, the Ramsey resonance transition signal of the second atom is used as a tool for monitoring the stability of the static magnetic field. The Ramsey resonance transition signal is generated when the atom undergoes hyperfine level transitions in a specific magnetic field environment, and its frequency is very sensitive to the magnetic field strength. By periodically scanning the Ramsey resonance transition signal of the second atom, the change in the magnetic field strength can be monitored in real time. Secondly, there is a proportional relationship between the static magnetic field strength and the difference between two specific transition frequencies of the second atom. This means that when the magnetic field strength changes, the difference between these two transition frequencies of the second atom will also change accordingly. Therefore, the change in the magnetic field strength is indirectly monitored by monitoring the change in the difference between these two transition frequencies.

[0057] To achieve the stability of the static magnetic field, it is necessary to ensure that the difference between these two transition frequencies of the second atom remains unchanged. For this purpose, the magnetic field strength is changed by adjusting the static magnetic field current value, thereby offsetting the influence of external interference on the magnetic field. Specifically, when it is monitored that the difference between the two transition frequencies of the second atom changes, the control system will automatically adjust the static magnetic field current value to restore the magnetic field strength to the original set value, thereby ensuring that the difference between the two transition frequencies remains unchanged.

[0058] Specifically, according to 133 the relationship between the Cs atom transition frequency and the magnetic field strength:

[0059]

[0060] Among them, v 0 is f 1 ≈6.8346875 GHz; v (0,0) is the frequency of the microwave excitation signal that causes the atoms to transition; H 0 is the static magnetic field strength, with the unit of gauss.

[0061] For ΔF = ±1, Δm F = 0 transition, the transition frequency is:

[0062]

[0063] Among them, represents 133 the transition frequency between the two Zeeman sub-levels of Cs atoms with F = 4, m F and F = 3, m F

[0064] For the two transition frequencies with m F = ±1, the difference is (see Figure 5 ):

[0065]

[0066] Among them, Δv is the difference between the two transition frequencies with m F = ±1, is 133 the transition frequency between the two Zeeman sub-levels of Cs atoms with F = 4, m F = 1 and F = 3, m F = 1, is 133 the transition frequency between the two Zeeman sub-levels of Cs atoms with F = 4, m F = -1 and F = 3, m F = -1.

[0067] It can be seen from formula (3) that the static magnetic field strength H 0 is proportional to the difference between the two transition frequencies with m F = ±1. That is to say, the difference between the two transition frequencies with m F = ±1 reflects the change of the static magnetic field. Taking the difference between the two transition frequencies with m F = ±1 as the reference signal and dynamically adjusting the current value of the constant current source 43 can achieve the stability of the static magnetic field.

[0068] And to obtain the difference between the two transition frequencies with m F = ±1, after the atomic beam clock frequency of the first atomic 87 Rb is locked, f is scanned between 9192666770 Hz and 9192681770 Hz​2 , the second atom is obtained 133 The m of Cs F = +1 peak frequency value f 2+ ; Scan f between 9192581770 and 9192596770 2 , the second atom is obtained 133 The m of Cs F = -1 peak frequency value f 2- ; Using f 2+ -f 2- as a fixed value as the criterion, dynamically adjust the size of the constant current source 43, thereby realizing magnetic field stability.

[0069] Embodiment 2:

[0070] Based on the same inventive concept, as Figure 2 shown, the present invention provides an atomic beam clock static magnetic field stabilization device based on a dual atom, applying a static magnetic field stabilization method for an atomic beam clock based on a dual atom in Embodiment 1. The stabilization device includes:

[0071] A cesium beam tube 1, on which there is a first optical window 11 located between the heating furnace 2 and the dual-mode 0-phase difference Ramsey cavity 3, and a second optical window 12 located between the dual-mode 0-phase difference Ramsey cavity 3 and the fluorescence collector 5; the first optical window 11 is used to transmit the pumping light, and the second optical window 12 is used to transmit the probing light.

[0072] Specifically, the design of the cesium beam tube 1 not only ensures the effective generation, transmission, and processing of the atomic beam, but also realizes the precise manipulation and detection of the atomic beam by the laser through the optical window structure thereon. It includes a heating furnace 2, a dual-mode 0-phase difference Ramsey cavity 3, and a fluorescence collector 5, etc., which are arranged collinearly in sequence, ensuring the efficient and stable transmission of the atomic beam in a straight line. The heating furnace 2 is located at the starting part of the cesium beam tube 1, and its interior is loaded with a first atom (such as 87 Rb) and a second atom (such as 133 Cs). Under the heating action of the heating furnace 2, the two atoms are evaporated and form a collinear dual-atom beam, which is accurately emitted through the collimation channel 21. This design ensures that the two atoms can be processed and detected under the same physical conditions, providing a solid foundation for subsequent realization of static magnetic field stabilization and clock transition locking.

[0073] Two optical windows are specially provided on the cesium beam tube 1, namely the first optical window 11 and the second optical window 12, which are respectively located between the heating furnace 2 and the dual-mode 0-phase difference Ramsey cavity 3, and between the dual-mode 0-phase difference Ramsey cavity 3 and the fluorescence collector 5, allowing light of a specific frequency (such as pumping light and probing light) to penetrate the cesium beam tube 1 and interact with the atomic beam, and also ensuring the perpendicular intersection of the light and the atomic beam, thereby realizing the precise preparation and detection of the atomic state.

[0074] Specifically, the first optical window 11 is mainly used to transmit the pumping light. During the atomic state preparation stage, the frequency-stabilized semiconductor laser light source emits two pumping lights with different frequencies, which are respectively set for 87 Rb and 133 the specific energy level transitions of Cs atoms. These two pumping lights pass vertically through the collinear two-atom beam through the first optical window 11, resonate with the atoms through the electric dipole, excite the atoms to a specific excited state, and then return to a specific ground state hyperfine energy level through processes such as spontaneous emission. This process realizes the precise control of the atomic state and provides a reliable guarantee for subsequent microwave transitions and signal detection.

[0075] The second optical window 12 is mainly used to transmit the probe light. After the microwave transition and the electric dipole resonance, the frequency-stabilized semiconductor laser light source emits two probe lights with different frequencies again, which pass vertically through the two-atom beam that has completed the microwave transition through the second optical window 12. When the probe light resonates with the atoms, the atoms will absorb photons and transition from their current energy level to a higher energy level, resulting in a change in the intensity of the probe light. By monitoring the change in the intensity of the probe light, the state and quantity of atomic transitions can be indirectly understood, and further the frequency information of the atomic clock can be analyzed.

[0076] The dual-mode 0-phase Ramsey cavity 3 is arranged in the cesium beam tube 1. The heating furnace 2, the dual-mode 0-phase Ramsey cavity 3, and the fluorescence collector 5 are arranged collinearly in sequence. The collinear two-atom beam passes through the dual-mode 0-phase Ramsey cavity 3 and reaches the fluorescence collector 5; a magnetic shielding cover 31 is provided outside the dual-mode 0-phase Ramsey cavity 3, and a magnetic field coil 32 is provided inside the magnetic shielding cover 31. Specifically, the magnetic shielding cover 31 is a device designed to weaken or eliminate the influence of external magnetic fields on electronic devices or precision instruments in a specific area. Its design is based on Faraday's law of electromagnetic induction and the principle of magnetic field shielding, and is usually made of materials with high magnetic permeability. These materials can effectively guide and disperse external magnetic field lines, thereby protecting the space inside the cover from external magnetic field interference. One or more magnetic field coils 32 are arranged inside the magnetic shielding cover 31. These coils generate an internal magnetic field when excited by an electric current, which is used to further control or adjust the magnetic field environment in the covered space. The working principle of the magnetic field coil 32 is based on Ampere's circuital law, that is, a magnetic field is generated around a wire when an electric current passes through it. By precisely controlling the magnitude and direction of the current in the coil, a magnetic field with the required intensity can be generated.

[0077] An electronics system 4, the electronics system 4 includes a dual-frequency microwave source 41, a voltage-controlled crystal oscillator 42, a constant current source 43, and a servo control system 44; a dual-mode 0-phase-difference Ramsey cavity 3, the dual-frequency microwave source 41, the voltage-controlled crystal oscillator 42, the servo control system 44, and a fluorescence collector 5 are connected in sequence; the fluorescence collector 5 receives the Ramsey resonance transition signal generated by the interaction of the dual-atom beam after microwave transition and the probe laser, and obtains the clock transition signal; using the clock transition signal as the reference signal of the atomic beam clock, in the servo control system 44, the phase detector is used to compare the phases of the clock transition signal and the signal of the voltage-controlled crystal oscillator 42, and the error signal of the voltage-controlled crystal oscillator 42 is obtained; the dual-mode 0-phase-difference Ramsey cavity 3 is used to generate microwaves of two frequencies, a magnetic shielding cover 31 is provided outside the dual-mode 0-phase-difference Ramsey cavity 3, and a magnetic field coil 32 is provided inside the magnetic shielding cover 31, the magnetic field coil 32 is used to generate a static magnetic field, the static magnetic field covers the collinear dual-atom beam, and enables the first atom and the second atom in the collinear dual-atom beam to perform microwave field excitation of the ground state 0-0 hyperfine level transition frequency according to the corresponding microwave frequencies.

[0078] Specifically, the dual-frequency microwave source 41 is responsible for generating microwave signals of two different frequencies, and the frequencies of these microwave signals are precisely regulated to match 87 Rb and 133 the frequencies of the ground state 0-0 hyperfine level transitions of two kinds of atoms, namely Cs. Inside the dual-mode 0-phase-difference Ramsey cavity 3, these two microwave signals act on the two kinds of atoms respectively, enabling them to complete their respective microwave transitions. This step is the basis for achieving high-precision measurement of the atomic clock.

[0079] The voltage-controlled crystal oscillator 42 is designed to generate a signal as the initial frequency reference of the atomic beam clock. However, due to the influence of the external environment (especially the magnetic field), the frequency of the voltage-controlled crystal oscillator 42 will shift, thus affecting the frequency accuracy and long-term stability. To solve this problem, the present invention introduces a servo control system 44. The servo control system 44 receives the dual-atom beam after microwave transition through the fluorescence collector 5 and extracts the clock transition signal from it. This signal, as the reference signal of the atomic beam clock, has extremely high frequency stability and accuracy. Then, the servo control system 44 uses a phase detector to compare the phases of the clock transition signal and the signal generated by the voltage-controlled crystal oscillator 42, thereby accurately measuring the phase difference between the signal of the voltage-controlled crystal oscillator 42 and the clock transition signal, that is, the error signal.

[0080] The magnitude and direction of the error signal reflect the deviation between the frequency of the voltage-controlled crystal oscillator 42 and the frequency of the clock transition signal. To precisely adjust the frequency of the voltage-controlled crystal oscillator 42, the error signal is sent to a loop filter for amplification and filtering. The function of the loop filter is to smooth the error signal to eliminate noise and interference while maintaining the accuracy of the signal. The filtered control signal is used to adjust the control voltage of the voltage-controlled crystal oscillator 42, thereby achieving precise adjustment of the frequency of the voltage-controlled crystal oscillator 42.

[0081] In addition, the control system further includes a constant current source 43, which is used to provide a stable current for the magnetic field coil 32. The magnetic field coil 32 is located inside a magnetic shielding cover 31 outside the dual-mode 0-phase-difference Ramsey cavity 3, and an internal static magnetic field is generated by passing a current. This static magnetic field covers the collinear two-atom beam and enables the two types of atoms to undergo transitions in the same magnetic field environment. Since both types of atoms undergo transitions in the same static magnetic field environment, the dependence of their transition frequencies on the magnetic field becomes consistent, which is beneficial for subsequent monitoring and stabilization of the static magnetic field by comparing the transition frequencies of the two types of atoms.

[0082] The laser system 7 is designed to vertically inject the pumping light and the probing light into a preset position, and the specific implementation method is as follows: The laser system 7 includes a first frequency-stabilized semiconductor laser light source 71, a first half-wave plate + PBS combination 72, a first semi-transparent and semi-reflective mirror 73, a second half-wave plate + PBS combination 74, and a second semi-transparent and semi-reflective mirror 75; the first frequency-stabilized semiconductor laser light source 71 emits laser light into the first half-wave plate + PBS combination 72, and the first half-wave plate + PBS combination 72 can continuously adjust the light intensity of the first frequency-stabilized semiconductor laser; the laser light passing through the first half-wave plate + PBS combination 72 is incident on the first semi-transparent and semi-reflective mirror 73, dividing the laser light into a first light beam and a second light beam; the first light beam serves as the first pumping light and passes through the first light window to intersect the two-atom beam perpendicularly; the second light beam is incident on the second half-wave plate + PBS combination 74, and the second half-wave plate + PBS combination 74 can continuously adjust the light intensity of the second light beam; the laser light passing through the second half-wave plate + PBS combination 74 is incident on the second semi-transparent and semi-reflective mirror 75, serving as the first probing light, and passes through the second light window to intersect the two-atom beam perpendicularly;

[0083] The laser system 7 further includes a second frequency-stabilized semiconductor laser 711, a third half-wave plate + PBS combination 79, a third semi-transmissive and semi-reflective mirror 78, a fourth half-wave plate + PBS combination 77, and a 45° reflector 76; the laser emitted by the second frequency-stabilized semiconductor laser 711 enters the third half-wave plate + PBS combination 79, and the third half-wave plate + PBS combination 79 can continuously adjust the light intensity of the second frequency-stabilized semiconductor laser 711; the laser passing through the third half-wave plate + PBS combination 79 enters the third semi-transmissive and semi-reflective mirror 78, which divides the laser into a third light beam and a fourth light beam; the third light beam serves as the second pumping light and passes through the first optical window to intersect perpendicularly with the two-atom beam; the fourth light beam enters the fourth half-wave plate + PBS combination 77, and the fourth half-wave plate + PBS combination 77 can continuously adjust the light intensity of the fourth light beam; the laser passing through the fourth half-wave plate + PBS combination 77 enters the 45° reflector 76 and serves as the second detection light, passing through the second optical window to intersect perpendicularly with the two-atom beam.

[0084] Among them, the laser frequencies of the first pumping light and the first detection light are the same, both being 87 the D 2 line 780 nm of Rb. The laser frequencies of the second pumping light and the second detection light are the same, both being 133 the D 2 line 852 nm of Cs. Additionally, in order to simplify the device, the first pumping light and the second pumping light can be collinear, and the first detection light and the second detection light can be collinear.

[0085] Furthermore, it further includes a graphite block 6, and the two-atom beam passes through the fluorescence collector 5 and enters the graphite block 6.

[0086] Specifically, the graphite block 6 is designed to be placed at the rear end of the fluorescence collector 5. After the two-atom beam completes microwave transitions and electric dipole resonances, it passes through the fluorescence collector 5 and is received by it, and then continues to move forward and enters the graphite block 6. The graphite block 6 mainly plays two key roles here: one is to serve as a termination absorber for the atomic beam, and the other is to help further stabilize the performance of the atomic beam clock through its unique physical properties.

[0087] First of all, as a termination absorber for the atomic beam, the graphite block 6 can effectively absorb the remaining atomic beam, preventing it from continuing to scatter or interfere with the normal operation of other parts. This ensures the overall stability and accuracy of the atomic beam clock system and avoids errors caused by incomplete processing of the atomic beam.

[0088] Secondly, the graphite block 6, by virtue of its high thermal conductivity and good thermal stability, helps to maintain the temperature stability of the operating environment of the atomic beam clock. During the precise measurement process of the atomic beam clock, temperature changes will have a significant impact on the energy level structure and transition frequency of atoms, thus leading to measurement errors. As a heat conduction medium, the graphite block 6 can effectively absorb and disperse the heat generated during the operation of the atomic beam clock, keeping the system temperature constant, thereby further improving the frequency accuracy and long-term stability of the atomic beam clock.

[0089] Furthermore, the laser system 7 further includes a second frequency-stabilized semiconductor laser light source 78. The second frequency-stabilized semiconductor laser light source 78 emits supplementary laser light that is incident on the second semi-transparent and semi-reflective mirror 75, and the second semi-transparent and semi-reflective mirror 75 reflects the supplementary laser light to the acousto-optic modulator 76.

[0090] Based on the same inventive concept, the present invention provides an electronic device, comprising: a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the computer program, a static magnetic field stabilization method for an atomic beam clock based on dual atoms is implemented.

[0091] Based on the same inventive concept, the present invention provides a computer-readable storage medium, on which a computer program is stored. When the program is executed by a processor, a static magnetic field stabilization method for an atomic beam clock based on dual atoms is implemented.

[0092] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A method for stabilizing the static magnetic field of an atomic beam clock based on diatomic atoms, characterized in that: Two types of atoms are selected, wherein the first type of atom is used as the first atom for generating clock transition, and the second type of atom is used as the second atom for stabilizing the static magnetic field; generating a collinear diatomic beam comprising the first atom and the second atom in a heating furnace under the same path; Performing atomic state preparation on the diatomic beam, emitting two pumping lights of different frequencies through a frequency-stabilized semiconductor laser light source, setting the two pumping lights to vertically pass through the diatomic beam, so that the two pumping lights respectively generate electric dipole resonance with the first atom and the second atom, so as to achieve that the first atom and the second atom are respectively in their specific ground state hyperfine energy levels; Injecting the diatomic beam into a dual-mode 0 phase difference Ramsey cavity, and under the action of a static magnetic field, respectively performing microwave field excitation of a ground state 0-0 hyperfine level transition frequency on the first atom and the second atom at corresponding frequencies, so that the first atom and the second atom complete their respective microwave transitions; Two probe lights of different frequencies are emitted by a frequency-stabilized semiconductor laser light source, and the two probe lights vertically pass through the diatomic beam after microwave transition and generate electric dipole resonance with the first atom and the second atom respectively; The Ramsey resonance transition signal after microwave transition and electric dipole resonance of the first atom and the second atom is received through a fluorescence collector, and the Ramsey resonance transition signal of the first atom is used as a clock transition signal; the clock transition signal is used as a reference signal of the atomic beam clock, and in a servo control system, a phase detector is used to compare the phase of the clock transition signal and the voltage-controlled crystal oscillator signal to obtain an error signal of the voltage-controlled crystal oscillator; the error signal is amplified and filtered by a loop filter to obtain a smooth control signal, and the voltage of the voltage-controlled crystal oscillator is controlled according to the control signal to adjust the frequency of the voltage-controlled crystal oscillator so that the frequency of the voltage-controlled crystal oscillator is consistent with the frequency of the clock transition signal; During the operation of the atomic beam clock, the Ramsey resonance transition signal of the second atom is scanned periodically. By utilizing the characteristic that the static magnetic field intensity is proportional to the difference between the two transition frequencies of the second atom, the static magnetic field current value is adjusted to ensure that the difference between the two transition frequencies of the second atom remains unchanged, thereby achieving stability of the static magnetic field.

2. The method for stabilizing the static magnetic field of a diatomic atomic beam clock according to claim 1, characterized in that: The first atom is 87 Rb, the second atom is 133 Cs; or the first atom is 133 Cs, the second atom is 87 Rb; or the first atom is 133 Cs, the second atom is 85 Rb.

3. A static magnetic field stabilization device for an atomic beam clock based on diatomic atoms, characterized in that: A method for stabilizing a static magnetic field of a diatomic atomic beam clock based on any one of claims 1 to 2, wherein the stabilizing device comprises: A cesium beam tube, wherein the cesium beam tube is provided with a first light window located between the heating furnace and the double-mode 0-phase-difference Ramsey cavity, and a second light window located between the double-mode 0-phase-difference Ramsey cavity and the fluorescence collector; the first light window is used to transmit pumping light, and the second light window is used to transmit detection light; A heating furnace, wherein the heating furnace is disposed in the cesium beam tube, and an output port of the heating furnace is provided with a collimation channel, so that a collinear diatomic beam containing the first atom and the second atom is generated in the heating furnace, and the collinear diatomic beam is perpendicular to the pumping light; A dual-mode 0 phase difference Ramsey cavity, wherein the dual-mode 0 phase difference Ramsey cavity is arranged in the cesium beam tube, the heating furnace, the dual-mode 0 phase difference Ramsey cavity and the fluorescence collector are arranged collinearly in sequence, and the collinear diatomic beam passes through the dual-mode 0 phase difference Ramsey cavity to reach the fluorescence collector; a magnetic shielding cover is arranged outside the dual-mode 0 phase difference Ramsey cavity, and a magnetic field coil is arranged inside the magnetic shielding cover; An electronics system, the electronics system comprising a dual-frequency microwave source, a voltage-controlled crystal oscillator, a constant current source and a servo control system; the dual-mode 0-phase difference Ramsey cavity, the dual-frequency microwave source, the voltage-controlled crystal oscillator, the servo control system and the fluorescence collector are connected in sequence; the Ramsey resonance transition signal generated by the action of the diatomic beam after microwave transition and the detection laser is received by the fluorescence collector, and the Ramsey resonance transition signal of the first atom is used as the clock transition signal; in the servo control system, the clock transition signal is phase-sensitively detected to obtain an error signal of the voltage-controlled crystal oscillator; the dual-mode 0-phase difference Ramsey cavity is used to generate microwave fields of two frequencies; a magnetic shielding cover is provided outside the dual-mode 0-phase difference Ramsey cavity, a magnetic field coil is provided inside the magnetic shielding cover, and the magnetic field coil is used to generate a static magnetic field, the static magnetic field covers the collinear diatomic beam, and causes the first atom and the second atom in the collinear diatomic beam to undergo a ground state 0-0 hyperfine level transition according to the corresponding microwave frequency; A laser system, the laser system comprising a first frequency-stabilized semiconductor laser light source, a first half glass slide + PBS combination, a first semi-transparent semi-reflecting mirror, a second half glass slide + PBS combination, and a second semi-transparent semi-reflecting mirror; the first frequency-stabilized semiconductor laser light source emits a laser that is injected into the first half glass slide + PBS combination, and the first half glass slide + PBS combination can continuously adjust the light intensity of the first frequency-stabilized semiconductor laser; the laser after passing through the first half glass slide + PBS combination is injected into the first semi-transparent semi-reflecting mirror, and the laser is divided into a first light and a second light; the first light is used as a first pumping light to pass through a first light window and intersect a diatomic beam perpendicularly; the second light is injected into a second half glass slide + PBS combination, and the second half glass slide + PBS combination can continuously adjust the light intensity of the second light; the laser after passing through the second half glass slide + PBS combination is injected into the second semi-transparent semi-reflecting mirror as a first detection light, and passes through the second light window and intersects the diatomic beam perpendicularly; The laser system also includes a second frequency-stabilized semiconductor laser, a third half glass slide + PBS combination, a third semi-transparent semi-reflecting mirror, a fourth half glass slide + PBS combination, and a 45° reflecting mirror; the laser emitted by the second frequency-stabilized semiconductor laser is injected into the third half glass slide + PBS combination, and the third half glass slide + PBS combination can continuously adjust the light intensity of the second frequency-stabilized semiconductor laser; the laser after passing through the third half glass slide + PBS combination is injected into the third semi-transparent semi-reflecting mirror, and the laser is divided into a third light ray and a fourth light ray; the third light ray is used as a second pumping light to pass through the first light window and intersect the diatomic beam perpendicularly; the fourth light ray is injected into the fourth half glass slide + PBS combination, and the fourth half glass slide + PBS combination is used to continuously adjust the light intensity of the fourth light ray; the laser after passing through the fourth half glass slide + PBS combination is injected into the 45° reflecting mirror as a second detection light, and passes through the second light window and intersects the diatomic beam perpendicularly.

4. The device for stabilizing a static magnetic field of a diatomic atomic beam clock according to claim 3, characterized in that: Also included is a graphite block, into which the diatomic beam is emitted through the fluorescence collector.

5. The device for stabilizing a static magnetic field of a diatomic atomic beam clock according to claim 3, characterized in that: The first pumping light and the first detection light have the same laser frequency, and the second pumping light and the second detection light have the same laser frequency.

6. The device for stabilizing a static magnetic field of a diatomic atomic beam clock according to claim 3, characterized in that: The first pumping light and the second pumping light are collinear, and the first detection light and the second detection light are collinear.

7. An electronic device, characterized in that: The electronic device comprises: a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps corresponding to the method according to any one of claims 1 to 2 when executing the computer program.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the program is executed by a processor, the steps corresponding to the method according to any one of claims 1 to 2 are implemented.

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