A method for improving the frequency measurement accuracy of an optical lattice clock in a microgravity environment

Abstract

The application relates to a method for improving the frequency measurement precision of an optical lattice clock in a microgravity environment, which comprises the following steps: two beams of lattice light are divided from one lattice light laser, each beam of lattice light is further divided into two beams of lattice light, and four beams of lattice light form two one-dimensional horizontal optical lattices; wherein the waist positions of the two one-dimensional horizontal optical lattices have a certain interval in the vertical direction, and the midpoint position is the position of the magnetic field zero point in the magneto-optical trap; the projections of the axial directions of the two horizontal optical lattices in the vertical plane are parallel to each other, and the projections in the horizontal plane are perpendicular to each other; an acousto-optic modulator with the same parameters is loaded on the light path of each beam of lattice light, and is used for linear frequency shift and modulation of the lattice light frequency; two clock laser beams are divided from one clock laser source, and are used for exciting different atomic groups in the two one-dimensional horizontal optical lattices. By synchronously detecting the clock transition spectral lines of each different atomic group, the differential comparison of the clock transition frequencies of different atomic groups is realized, so that the common-mode noise in the optical clock system is suppressed. The method can realize an optical lattice clock with super-high frequency measurement precision in a microgravity environment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atomic optical lattice clock, and particularly relates to a method for improving the frequency measurement precision of an optical lattice clock in a microgravity environment. BACKGROUND

[0002] In recent years, the optical lattice clock based on neutral atoms has been widely used in time frequency metrology, quantum precision measurement, quantum sensing, quantum simulation and other fields due to its ultra-high frequency measurement precision, stability and accuracy. In the development of optical clock, the improvement of precision is undoubtedly the primary goal pursued by optical clock development teams all over the world. Since the advent of optical lattice clock in 2005, the technology of neutral atom optical lattice clock has been continuously developing, and various optical clock development teams around the world have proposed numerous schemes to improve the frequency measurement precision of optical clock. From one-dimensional optical lattice clock to three-dimensional optical lattice clock, optical tweezer clock, Wannier-Stark clock and differential optical lattice clock based on shallow optical lattice, the frequency measurement precision of optical clock has been improved from E-18 to E-21 or even higher. The last two clocks are the optical lattice clocks with the highest reported frequency measurement precision, and both of them are based on shallow optical lattice. The advantage of shallow optical lattice is that it can reduce the scattering rate and atomic heating rate in the optical lattice, thereby prolonging the decoherence time of atoms in the lattice and providing a more stable place for the detection of clock transition spectrum. In July 2024, the Joint Institute for Laboratory Astrophysics (JILA) reported their latest strontium optical clock NEW JILA SrClock, with a system frequency uncertainty of 8.1×10 -19 This is the most accurate neutral atom optical clock so far, and it is realized based on shallow optical lattice. This also shows that shallow optical lattice technology plays a very important role in improving the frequency measurement precision and accuracy of neutral atom optical clock. However, shallow optical lattice will have tunneling effect, which will cause the broadening and splitting of clock transition spectrum. Both Wannier-Stark clock and differential optical lattice clock use vertical optical lattice and utilize gravity potential to introduce gradient potential field between different lattice sites, thereby suppressing tunneling. However, this method will not work in a microgravity environment. Therefore, if we want to improve the frequency measurement precision of space optical clock or star-borne optical clock operating in a microgravity environment, we need to suppress the tunneling phenomenon in shallow optical lattice through non-gravitational means to improve the precision of optical lattice clock operating in a microgravity environment. It should be noted that the information disclosed in the above background section is only used to strengthen the understanding of the background of the present application, and therefore can include information that does not constitute prior art known to those of ordinary skill in the art. SUMMARY

[0003] The application provides a method for improving the frequency measurement precision of an optical lattice clock in a microgravity environment, which can improve the frequency measurement precision of a neutral atom optical lattice clock in a microgravity environment, and can overcome the defects in the prior art to some extent.

[0004] Other characteristics and advantages of the application will become apparent from the detailed description that follows, or will be learned by practice of the application.

[0005] According to a first aspect of the application, a method for improving the frequency measurement precision of an optical lattice clock in a microgravity environment is provided, and the method comprises:

[0006] Two beams of lattice light are divided from one lattice light laser, and each beam of lattice light is further divided into two beams of lattice light, and the four beams of lattice light form two one-dimensional horizontal optical lattices; wherein the waist positions of the two one-dimensional horizontal optical lattices have a certain interval in the vertical direction, and the midpoint position is the position of the magnetic field zero point in the magneto-optical trap, and the axial directions of the two horizontal optical lattices are parallel to each other in the projection in the vertical plane, and perpendicular to each other in the projection in the horizontal plane;

[0007] Two beams of clock light are divided from one clock laser source to excite different groups of atoms in the two one-dimensional horizontal optical lattices;

[0008] An acousto-optic modulator with the same parameters is loaded on the light path of each beam of lattice light for linear frequency shift and modulation of the lattice light frequency, wherein the acousto-optic modulator loaded on the light path of the two beams of lattice light for generating one one-dimensional horizontal optical lattice is connected to an arbitrary function generator, the acousto-optic modulator loaded on the light path of the two beams of lattice light for generating another one-dimensional horizontal optical lattice is connected to another arbitrary function generator; an acousto-optic modulator is also loaded before the clock light is divided for scanning the clock light frequency, and the acousto-optic modulator on the clock light is connected to a third arbitrary function generator;

[0009] The three arbitrary function generators are all traced back to the same hydrogen clock as a frequency reference source.

[0010] In some exemplary embodiments, the two beams of lattice light are divided from one lattice light laser, and each beam of lattice light is further divided into two beams of lattice light, and the four beams of lattice light form two one-dimensional horizontal optical lattices, specifically:

[0011] The lattice light output by the lattice light laser is split into two beams by a polarization beam splitter, and each beam of lattice light is further split into two beams of lattice light by a polarization beam splitter, and the four beams of lattice light are first lattice light, second lattice light, third lattice light and fourth lattice light; wherein the initial optical power of the first lattice light and the second lattice light is set to be the same, and the initial optical power of the third lattice light and the fourth lattice light is set to be the same; the initial optical power of the first lattice light and the second lattice light is greater than the initial optical power of the third lattice light and the fourth lattice light;

[0012] The first lattice light and the second lattice light are incident on the atomic group captured by the magneto-optical trap at a 90° angle, and the third lattice light and the fourth lattice light are incident on the atomic group captured by the magneto-optical trap at a 90° angle, and the third lattice light is opposite to one of the first lattice light and the second lattice light, and the fourth lattice light is opposite to the other of the first lattice light and the second lattice light, forming two one-dimensional horizontal optical lattices.

[0013] In some example embodiments, the two beams of clock laser split by the clock laser source excite different atomic groups in the two one-dimensional horizontal optical lattices, specifically:

[0014] The clock laser output by the clock laser is split into two beams by a polarization beam splitter, which are first clock laser and second clock laser, the first clock laser is combined with one of the third lattice light and the fourth lattice light through a dichroic mirror, and the second clock laser is combined with the other of the third lattice light and the fourth lattice light through a dichroic mirror.

[0015] In some example embodiments, a half-wave plate, a linear polarizer and a convex lens are sequentially connected at the end of the optical path of each beam of lattice light, wherein:

[0016] The half-wave plate and the linear polarizer are used to adjust the polarization direction of each beam of lattice light, so that the polarization direction remains vertical polarization;

[0017] The convex lens is used to fix the beam waist position of the lattice light at the center of the atomic group in the magneto-optical trap.

[0018] In some example embodiments, the polarization direction is adjusted by adding a half-wave plate to each of the two beams of clock laser, so that the polarization direction of the clock laser is consistent with the polarization direction of the lattice light; then a convex lens is used to combine with the convex lens in the lattice light beam, so as to adjust the beam waist size and position of the clock laser.

[0019] In some example embodiments, a microwave switch, a voltage-controlled attenuator and a time sequence control system are provided between the acousto-optic modulator and the arbitrary function generator;

[0020] The series of TTL digital pulse signals generated by the timing control system are transmitted to the microwave switch, and the microwave switch turns on or off the RF signal outputted from the arbitrary function generator according to the instruction of the timing control system, so as to realize the switching of the lattice laser and the control of the linear frequency shift signal and the frequency modulation signal in the action time.

[0021] The timing control system transmits a time-varying analog voltage waveform to the voltage-controlled attenuator, so as to realize the variable attenuation of the RF signal intensity.

[0022] In some example embodiments, the modulation parameters suitable for the specific optical lattice well depth are selected by Floquet design technology, and the specific process is as follows:

[0023] Two identical modulation RF signals are outputted from an arbitrary function generator, both of which are sine modulation and have the same carrier frequency and modulation parameters, and then the two signals are synchronously loaded on the acousto-optic modulators of the first lattice light and the second lattice light, and the starting time and the action time of the signals are controlled by the timing control system and the microwave switch; the parameters of the sine modulation signal are selected by the tunneling rate modulation function, that is, the modulation depth corresponding to the zero point of the first Bessel function; the parameters of the frequency modulation functions loaded on the two one-dimensional horizontal optical lattices are completely consistent.

[0024] In some example embodiments, the acceleration and movement of the optical lattice are realized by changing the frequency difference of the two counter-propagating lattice lights in the two one-dimensional horizontal optical lattices, so as to prepare a plurality of atomic samples required by the differential optical clock, and the specific process is as follows:

[0025] Two RF signals without modulation, which have the same carrier frequency as the RF signal outputted from the arbitrary function generator in claim 7, are outputted from another arbitrary function generator at the initial time, and then the two signals are synchronously loaded on the acousto-optic modulators of the third lattice light and the fourth lattice light, and the starting time and the action time of the signals are controlled by the timing control system, the microwave switch and the acousto-optic modulator; the output frequency of the RF signal without modulation is changed in a given action time period by the timing control system, the arbitrary function generator and the acousto-optic modulator, so as to introduce the frequency difference with the carrier frequency of the RF signal loaded on the acousto-optic modulators of the first lattice light and the second lattice light, thereby accelerating the optical lattice, splitting the atomic group in the optical lattice, and moving the split atomic group to the position symmetric to the center of the magnetic field zero point of the magnetic optical trap, so as to prepare a plurality of atomic group samples required by the differential optical clock.

[0026] In some example embodiments, the excitation process is to use two interval time The pulse is realized by a time sequence control system and an acousto-optic modulator on a clock laser light path and a third arbitrary function generator connected therewith to realize a frequency scanning function of the clock laser, so as to detect complete Ramsey spectrum lines in a given frequency band. The time sequence control system, a voltage-controlled attenuator and the acousto-optic modulator are cooperated to control the duration of the clock laser pulse and the interval time between the two pulses; and the time sequence control system, the voltage-controlled attenuator and the acousto-optic modulator are cooperated to adjust the required clock laser power of the pulses corresponding to different excitation times. The time sequence control system, a voltage-controlled attenuator and the acousto-optic modulator are cooperated to control the duration of the clock laser pulse and the interval time between the two pulses; and the time sequence control system, the voltage-controlled attenuator and the acousto-optic modulator are cooperated to adjust the required clock laser power of the pulses corresponding to different excitation times.

[0027] The method for improving the frequency measurement precision of the optical lattice clock in the microgravity environment provided by the embodiment of the application combines the Floquet design technology and the differential optical lattice clock technology, realizes the synchronous differential optical lattice clock of multiple quantum samples by constructing 8 atom group samples in two horizontal optical lattices, and suppresses the tunneling phenomenon in the shallow optical lattice by the Floquet design technology, so as to realize the optical lattice clock with ultra-high frequency measurement precision in the microgravity environment, which is of great significance for the establishment of the time frequency reference source in the space environment and the basic physical research based on the optical lattice clock. The specific embodiments are as follows:

[0028] The Floquet design technology is introduced, that is, the optical lattice potential field is constructed by modulating the optical lattice frequency, the tunneling rate in the optical lattice potential is modulated, and the tunneling effect in the shallow optical lattice is suppressed, so as to overcome the problem that the optical lattice step potential field cannot be introduced by the gravitational potential in the microgravity environment to suppress the tunneling effect in the shallow optical lattice. The double one-dimensional horizontal multiplexing differential optical lattice device is adopted to eliminate the clock transition frequency shift caused by various common mode noises such as clock laser noise and environmental fluctuation changes such as blackbody radiation, magnetic field gradient and electric field gradient, so as to improve the frequency measurement precision of the optical clock, especially the frequency measurement precision of the optical clock in the microgravity environment. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0029] The drawings incorporated into the specification and forming a part of the specification, show embodiments consistent with the application, and together with the specification serve to explain the principles of the application. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained from these drawings without creative labor for those skilled in the art.

[0030] Figure 1Theoretical principle diagram for tunneling inhibition by Floquet design for embodiments of the present application;

[0031] Figure 2 Optical path schematic diagram of a one-dimensional horizontal double optical lattice device provided by embodiments of the present application;

[0032] Figure 3 Radio frequency signal link diagram in a one-dimensional horizontal double optical lattice device provided by embodiments of the present application;

[0033] Figure 4 Differential optical lattice clock timing control schematic diagram based on Floquet design provided by embodiments of the present application;

[0034] Figure 5 One-dimensional horizontal double optical lattice atomic group provided by embodiments of the present application; (a) distribution of atomic samples without optical lattice acceleration and movement; (b) distribution of atomic samples after optical lattice acceleration and movement. DETAILED DESCRIPTION

[0035] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations can, however, be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these implementations are provided so that this disclosure will be thorough and complete, and fully convey the scope of example implementations to those skilled in the art. Features described in the description, structures, or characteristics can be combined in any suitable manner in one or more implementations.

[0036] In addition, the drawings are merely schematic and are not drawn to scale. Identical reference numerals in the figures designate the same or similar parts throughout the figures and the detailed description. Some of the block components, which are illustrated in the drawings, are functional entities that do not necessarily have to correspond to physically or logically independent entities. These functional entities can be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0037] At present, there are many techniques for improving the frequency measurement precision of optical lattice clocks, such as the existing shallow optical lattice technique and the differential optical lattice clock technique. By combining the two techniques, the frequency measurement precision of E-21 or even higher order can be achieved by using only the clock laser with a linewidth of the order of hertz. However, in order to achieve such high frequency measurement precision of the shallow optical lattice clock with a single quantum sample instead of the differential structure, the clock laser local oscillator with a linewidth of the order of millihertz is required. However, the optical lattice device for realizing the differential shallow optical lattice clock is a one-dimensional vertical multiplexing optical lattice device, and the tunneling phenomenon in the shallow optical lattice is mainly suppressed by relying on the gravitational potential. In the microgravity environment, the tunneling phenomenon in the shallow optical lattice cannot be effectively suppressed, thereby causing the broadening of the clock transition spectral line of the optical lattice clock and the deterioration of the frequency stability and uncertainty of the optical clock, so that the frequency measurement precision of the optical clock cannot be improved by using the shallow optical lattice differential optical lattice clock device.

[0038] In the microgravity environment, if the shallow optical lattice is used to realize the optical lattice clock with higher frequency measurement precision, the tunneling phenomenon in the shallow optical lattice cannot be suppressed by the gravitational potential field. In order to solve the problem of the prior art, the present application proposes to construct the optical lattice potential field by using the Floquet design technique to modulate the tunneling rate in the optical lattice potential, so as to suppress the tunneling phenomenon in the shallow optical lattice in the microgravity environment. The present application proposes to combine the one-dimensional horizontal shallow optical lattice based on the Floquet design with the differential optical lattice clock technique, so as to further improve the frequency measurement precision of the optical lattice clock in the microgravity environment. In this way, the research and development cost of the ultra-stable clock laser system in the space environment can be reduced, and the precision of the optical clock can be improved.

[0039] The present application upgrades the optical path and the electric control system of the optical lattice device based on the existing conventional strontium optical clock system in the laboratory, increases the functions of lattice light frequency modulation and scanning, realizes the tunneling suppression in the shallow optical lattice and the movement process of the atomic group by using the non-gravitational method, and realizes the differential optical lattice clock function by using the double horizontal one-dimensional optical lattice structure.

[0040] Specifically, the lattice light frequency is modulated, so that the potential field function of the optical lattice is designed to modulate the tunneling rate to a value close to zero, so as to avoid the spectral line broadening and splitting of the clock transition spectral line due to the tunneling. Under the modulation of the sine function, the effective tunneling rate under the driving optical lattice satisfies wherein is the zero-order first Bessel function, is the modulation coefficient, and for each different order in the expansion term . Since the and terms contained in the tunneling rate can be expanded into a Fourier series, the expansion coefficient obtained is the first Bessel function .​Figure 1 exhibits sinusoidal function modulation = 0, 1, 2 order Bessel function and the first zero point of each order Bessel function corresponding to the modulation depth coefficient In the present application, the sinusoidal function is also used as the frequency modulation function of the lattice light, and the tunneling effect can be almost completely suppressed by setting the modulation parameters in the experimental system at the zero points of the Bessel function in the figure, so that it is not necessary to introduce a step potential field by gravity to suppress the tunneling between the lattice sites.

[0041] Specifically, the spatial position distribution of the atomic group in the optical lattice is changed by changing the center frequency difference of the two lattice lights forming the optical lattice potential well. When the optical lattice is formed by two beams of laser light emitted from the same laser to form a standing wave field, since the two beams of laser light are homologous, when there is no additional frequency shift device, the center position of the atomic group in the optical lattice will be at the beam waist of the lattice laser, and when a frequency difference is generated between the two beams of laser light by the frequency shift device , then part of the atomic group in the optical lattice will be dragged by the moving optical lattice for a distance . If the frequency difference of the two beams of lattice laser light is fixed , then the moving speed of the atom with the lattice is . If the frequency difference changes with time, then the acceleration of the lattice movement can be written as . Therefore, by changing the frequency difference between the two beams of lattice laser light forming the optical lattice and the action time and change rate, the movement and splitting of the spatial position of the atomic group in the optical lattice can be realized. By controlling the acceleration of the lattice movement to a level that can ensure that the kinetic energy of the high-energy state atom is close to the potential energy of the optical lattice potential well, and then non-adiabatically quickly changing the frequency difference of the two counter-propagating beams of lattice laser light, while also keeping the 689 nm magneto-optical trap corresponding to the process of two-stage narrow-band cooling of atoms in the open state, part of the atoms in the low-energy state are tightly bound by the optical lattice potential well and move with the optical lattice, while the remaining high-energy state atoms are thrown out of the lattice or tunnel and are captured by the magneto-optical trap, thereby staying at the original center position. This way, a group of atomic samples is spatially divided into two groups of atomic samples. Multiple use of this atomic group splitting technology can form a small differential optical clock network, thereby performing various quantum precision measurements. The optical lattice device in the present application is composed of a standing wave field formed by two beams of laser light divided from a lattice laser, and an acousto-optic modulator with the same parameters is loaded on each of the two beams of split laser light to realize independent control of the center frequency and frequency modulation function of the two beams of lattice light.

[0042] Traditional optical lattice clock systems usually detect the clock transition spectrum of a quantum sample composed of a group of atoms, and evaluate the stability and uncertainty of the optical clock by time-sharing self-comparison method. Generally, the fractional frequency stability of an optical clock under the standard quantum limit is determined by quantum projection noise (QPN), which can be expressed as:

[0043] (1)

[0044] wherein, is the mass factor of the atomic clock transition energy level transition spectrum (the ratio of transition frequency to line width), is the number of atoms being detected, is a period of clock closed loop operation, is the average time, is the number of photons detected by each atom, characterizes the measurement fluctuation introduced by the detection technology, which is manifested as the change of the normalized atomic fractional excitation rate. As can be seen, the number of atoms in the quantum sample of the neutral atom optical clock is much larger than that in the single ion optical clock, so this is why the neutral atom optical clock can reach the same stability faster than the single ion optical clock in the same average time. Although the quantum projection noise limit calculated by the typical parameter values of the neutral atom optical lattice clock can reach 1×10 -17 / , but in the process of detecting the spectrum of the traditional single atom quantum sample optical clock, the atomic detection noise is usually masked by the noise from the optical phase-locked loop. In the process of quantum state preparation and reading, the optical phase-locked loop does not act on the clock laser, so there will be frequency fluctuation aliasing, and this aliasing noise is called Dick noise. During the laser tuning process, it will be compensated for errors, thereby affecting the stability of the optical clock. At this time, the stability of the optical clock is mainly determined by the optical phase-locked loop, not the atomic system, so if you want to improve the stability of the optical clock, you need to use a higher performance optical phase-locked loop by iteration. Sometimes this phase-locked loop is even more complex in the experiment than the atomic system it detects, which is a challenge for the application of optical clocks in scenarios outside the laboratory.

[0045] If the detection method of the clock transition spectrum of the optical clock is Ramsey spectrum, the fractional frequency uncertainty of the comparison of two optical clocks with the same performance under the QPN limit is:

[0046] (2)

[0047] wherein, is the transition frequency of the clock transition energy level, is the coherence time of the clock laser and the atom, The sum of the preparation time of the quantum state for each clock cycle, also known as the dead time, and the clock cycle . The contrast ratio of the Ramsey fringe, factor It is assumed that two optical clocks have equal contributions to the uncertainty. As can be seen from equation (2), increasing the number of atoms and the coherence time of the atoms and the laser , can improve the stability of the optical clock, but the frequency noise of the clock laser will cause the coherence time of the atoms and the laser to decrease, and due to the Dick effect, the stability of the optical clock will be hindered from reaching the QPN limit. At this time, the Dick noise is the main factor that limits the highest level of optical clock stability.

[0048] Therefore, there are usually two ways to reduce Dick noise. One is to directly further reduce the frequency noise of the clock laser. Currently, the clock laser based on a strontium atomic optical lattice clock in a ground laboratory can achieve a laser linewidth of 8 mHz. By interacting with atoms through such an ultra-stable clock laser, a high-stability optical clock can be achieved. The advantage is that the noise of the laser itself is lower, so the noise mixed into the optical clock is also lower, which is suitable for optical clock systems of various structures, but the disadvantage is that the technical challenge is great and the cost is high, and the Dick effect cannot be completely eliminated. The other method is to use two or more cold atomic systems of the same structure in parallel to suppress the Dick effect. That is, by using a clock laser to perform Ramsey synchronous detection on different atomic samples, noises such as detector electronic noise and short-term frequency drift of the laser can be suppressed. The advantage of this method is that the stability requirement of the clock laser itself is not very high. The disadvantage is that two or more atomic quantum sample systems need to be prepared separately, and the structure becomes complex. If these differential quantum samples are not generated by the same physical system, some new environmental noise may be introduced. However, if the differential quantum samples are generated in the same physical system, even if they are divided from the same atomic group, the common-mode noise caused by environmental fluctuations, such as blackbody radiation frequency shift, AC Stark shift introduced by lattice light and clock laser, etc., will be significantly reduced. At the same time, the complexity of the device structure is much simpler than that of the separately prepared atomic quantum sample system.

[0049] Therefore, the differential optical clock scheme in the same physical system is more suitable for realizing high-precision space optical clocks and high-performance mobile optical clocks in a microgravity environment.

[0050] Based on the above principle analysis, the example embodiment provides a method for improving the frequency measurement accuracy of an optical lattice clock in a microgravity environment, including the following three aspects:

[0051] On the one hand, the lattice light output from the lattice laser is split into four beams by multiple polarization beam splitters, and the initial optical power of the two beams is... P 1 is set to 600 mW, while the initial optical power of the other two lattice beams is... P 2. The power is set to 200 mW. An identical acousto-optic modulator is added to each of the four lattice beams to achieve linear frequency shifting and modulation of the lattice beam frequency. Two higher-power lattice beams are horizontally incident on the atomic clusters trapped in the magneto-optical trap at a 90° angle in the horizontal plane. The beam waists of the two beams are at the same horizontal position, with a vertical spacing of 200 μm and a consistent beam waist diameter of approximately 100 μm. The polarization direction of each lattice beam is adjusted by adding a linear polarizer and a half-wave plate to each of the four lattice beams to maintain vertical polarization. Simultaneously, the two weaker lattice beams are incident on the two stronger lattice beams to form a one-dimensional horizontal two-beam lattice structure. Meanwhile, a clock laser passes through a dichroic mirror from the weaker beams... P The two clock laser beams are combined with the lattice beam at both ends. Both beams originate from the same laser source and are of the same origin. A waveplate is used to adjust the polarization direction, ensuring that the clock laser's polarization direction aligns with that of the lattice beam. A convex lens is then used in combination with a lens in the lattice beam to adjust the beam waist size and position of the clock laser, making it as planar as possible within the optical lattice region to guarantee the uniformity of energy level transitions within excited atoms. Furthermore, the radio frequency drive signal and modulation signal acting on the acousto-optic modulator are both generated by an arbitrary function generator, with the two beams having a power of [missing information]. P Both acousto-optic modulators in the lattice light path of beam 1 are connected to the same arbitrary function generator to achieve frequency modulation of the lattice light; the two beams have power of P The two acousto-optic modulators on the lattice laser path are both connected to another arbitrary function generator to achieve frequency shifting of the lattice laser; while the acousto-optic modulator on the clock laser path is connected to a third arbitrary function generator to achieve frequency sweeping of the clock laser. Furthermore, all three arbitrary function generators are traced back to the same hydrogen clock as a frequency reference source. To perform timing control of the lattice laser, a microwave switch is connected between the arbitrary function generator and the voltage-controlled attenuator. This microwave switch transmits a series of TTL digital pulse signals generated by the timing control system to the microwave switch, which then turns the radio frequency signal output from the arbitrary function generator on or off according to the instructions of the timing system. This enables the switching of the lattice laser and the manipulation of the linear frequency shift signal and frequency modulation signal in terms of their duration. In order to adjust and control the power and power change rate of the lattice laser incident on the atomic group, a voltage-controlled attenuator needs to be connected between the microwave switch and the acousto-optic modulator. Then, an analog voltage waveform that changes with time is transmitted to the voltage-controlled attenuator through a timing control system, so as to realize the variable attenuation of the radio frequency signal strength.

[0052] For example, such as Figure 2 The diagram shows the optical path of a one-dimensional horizontal dual-light lattice device provided in an embodiment of the present invention. First, a beam of lattice light output from an 813 nm laser is split into two beams of equal power by passing through a waveplate and a polarizing beam splitter. These two beams are then each passed through a waveplate and a polarizing beam splitter, splitting into four beams: a first lattice beam, a second lattice beam, a third lattice beam, and a fourth lattice beam. The first and second lattice beams have higher power and are both set to... P 1 = 600 mW, the two beams of light from the third and fourth lattice layers are both set to relatively weak power. P 2 = 200 mW. These four lattice beams are guided by a necessary 813 nm high-reflection mirror. Each beam passes sequentially through an acousto-optic modulator, a half-wave plate, a linear polarizer, and a convex lens. These optical elements enable linear frequency shifting or modulation of each beam, ensuring vertical linear polarization. The beam waist is fixed at the center of the atomic cluster in the magneto-optical trap by the convex lens. Simultaneously, a higher-power lattice beam and a lower-power lattice beam are incident towards each other to form a one-dimensional horizontal optical lattice. The remaining higher-power lattice beam and another lower-power lattice beam are incident towards each other to form a second one-dimensional horizontal optical lattice. The projections of the optical axes of the two one-dimensional horizontal optical lattices onto the horizontal plane are two perpendicular lines, while their projections onto the vertical plane are two parallel lines. The optical axes of the two one-dimensional horizontal optical lattices are perpendicular to each other in opposite planes, with a spacing of 200 μm. The power is... P Two beams of lattice light, 1, are incident horizontally at angles of +45° and -45° respectively, onto the atomic clusters captured by the magneto-optical trap; the power is... P Two beams of lattice light are incident horizontally at +135° and -135°, respectively, onto the atomic clusters captured by the magneto-optical trap. Furthermore, the clock laser is first scanned for frequency and its switching and power adjustment functions are achieved through an acousto-optic modulator. Then, a half-wave plate and a polarization beam splitter split the clock laser into two beams. Each of these two beams is then passed through a half-wave plate to adjust its polarization direction to vertical, consistent with the polarization direction of the lattice light. Finally, each beam is passed through a convex lens, in conjunction with the convex lens before the lattice light incident onto the atomic clusters, to adjust the beam waist position and spot size of the clock laser. This ensures that the spot size of the clock laser incident on the atomic clusters in the optical lattice remains almost unchanged, and that the power density is uniform in the region of the optical lattice, thereby achieving uniform excitation of atoms when probing clock transition spectral lines. Finally, the two clock laser beams are combined with the lattice light at the weaker power end by passing through a dichroic mirror that has high reflectivity for 813 nm wavelength light and high transmittance for 698 nm wavelength light.

[0053] On the other hand, the timing control involved in the one-dimensional horizontal dual-light lattice device in the optical clock is modified, and then the power and frequency of the lattice light and clock laser are changed and modulated through optoelectronic components such as acousto-optic modulators, voltage-controlled attenuators, and microwave switches, so as to realize the Flokai-designed differential optical lattice clock that can be used to improve the frequency measurement accuracy of optical clocks under microgravity environments. Among them, Figure 2 The radio frequency signal transmission links involved in each acousto-optic modulator are as follows: Figure 3 As shown in the figure, the timing control system controls the timing of the radio frequency drive signal applied to the acousto-optic modulator by connecting a microwave switch and a voltage-controlled attenuator. The specific timing control diagram for implementing the Floch design differential optical lattice clock is shown below. Figure 4 As shown. First, after primary atomic cooling via a 461 nm magneto-optical trap and secondary broadband cooling via a 689 nm magneto-optical trap, during the secondary narrowband cooling process, cold atomic clusters in the 689 nm magneto-optical trap are loaded using a deep-light lattice. At this point, under the influence of two relatively high-power lattice lights... P At the incident end 1, the same lattice light modulation signal is applied by acousto-optic modulators 1 and 3 respectively. At the two weaker lattice light incident ends, the same lattice light frequency shift signal is applied by acousto-optic modulators 2 and 4 respectively, thereby realizing the movement of atomic clusters within the optical lattice. Figure 4 The process within the black dashed box enables the spatial splitting and movement of atomic clusters. Figure 5 This demonstrates the change in the spatial distribution of atomic clusters within the optical lattice during this process. When the frequency difference between the incident and reflected light is... At that time, the optical lattice will move at a speed To move, therefore, the frequency difference is first set to... Then the optical lattice moves at a speed The atom cluster moves forward, then stops at the predetermined position, and the frequency difference is reduced to 0, causing the atom cluster to stop moving. The duration is... t 1. Then set the frequency difference to... Since no particularly large acceleration is needed to separate the atomic clusters during the later stages of moving the optical lattice, but only a short period of time is required to move them to the designated positions, the two frequency differences are usually set to... Then the optical lattice moves at a speed Move backward. During this process, The choice is also crucial, if If the atoms are too small, they are more likely to follow adiabatically, and the splitting is not obvious. If the frequency difference is too large, many atoms will be ejected from the lattice or tunneled and then captured by the magneto-optical trap, resulting in a loss of atoms in the moving lattice and a decrease in splitting efficiency. This invention selects a frequency difference on the order of hundreds of kHz or even lower. It is more appropriate to realize obvious atomic group splitting, and the adjustment needs to be made according to the potential well depth of the optical lattice and the temperature distribution of the atoms. The maintenance time of each frequency difference t 2and t 4can be preliminarily calculated through the specific values of the speed, acceleration, action time and separation distance of the optical lattice, and then fine-tuned in combination with the experimental conditions. In the process of realizing atomic group splitting, the 689 nm magneto-optical trap narrow-band cooling needs to be kept on until the atomic splitting is completed, and then the magneto-optical trap is turned off. Then, the smaller lattice light frequency difference is used to move the split atomic groups to the positions symmetrically centered on the zero point of the magnetic field in the magneto-optical trap, and keep the spatial position distance unchanged. This is because in the process of realizing atomic group splitting by accelerating through the optical lattice, part of the atoms have too high temperature or too wide momentum distribution. If there is no assistance of the magneto-optical trap, the atoms are likely to escape from the lattice potential well, resulting in loss of the number of atoms and reducing the atomic splitting efficiency. After realizing the atomic sample distribution in Figure 5 , in order to further reduce the atomic temperature, the power of the lattice light is first adiabatically reduced to reduce the well depth of the optical lattice potential well. The power of the lattice light is adjusted by adjusting the acousto-optic modulator on the weaker P 2end of the lattice light, so as to reduce the well depth of the optical lattice. The atoms with higher temperature in the high-order Bloch sideband of the optical lattice are thrown out of the optical lattice, and then the well depth is adiabatically increased to the original deep well depth. Then, the strong π pulse of the clock laser with the frequency at the red sideband is used to quickly pump the atoms to the lower-order Bloch sideband, i.e. the transition experienced by the atoms is . Then, the strong π pulse of the clock laser with the carrier frequency is used to pump the atoms to the ground state, i.e. . If necessary, this process can be repeated 2-3 times to ensure that most of the atoms are as much as possible in the ground state. Thus, the preparation of atomic motion state and the reduction of well depth are realized.

[0054] For example, as shown in Figure 3 , a radio frequency signal link diagram in a one-dimensional horizontal double optical lattice device provided by an embodiment of the application is shown. Figure 2To achieve arbitrary frequency changes and switching of the lattice light and clock laser frequencies, the five acousto-optic modulators first need to transmit TTL digital pulse signals and varying analog voltage signals to microwave switches and voltage-controlled attenuators via a timing control system. This allows for timing control of the radio frequency (RF) signals output by the arbitrary function generators. The timing-controlled RF signals are then connected to the acousto-optic modulators to regulate and switch the frequencies and power of the lattice light and clock laser. The RF drive signals for the acousto-optic modulators are provided by three arbitrary function generators. Two generators generate the RF drive signals for the acousto-optic modulators in the lattice light path, while the third generator generates the RF drive signals for the acousto-optic modulators in the clock laser path. All three arbitrary function generators are traced back to the same hydrogen clock, and are externally triggered by a 1 PPS pulse output from the hydrogen clock, thus achieving effective and synchronized high-precision timing control.

[0055] For example, such as Figure 4 The diagram shown is a schematic diagram of timing control for a differential optical lattice clock based on the Flokai design, provided in an embodiment of the present invention. First, in the capture... 87 In the magneto-optical trap of neutral Sr atoms, the operation is divided into two stages. In the first stage, the magneto-optical trap operates at a strong dipole transition at 461 nm, reducing the atomic temperature to the mK level. This stage is also known as primary cooling, and typically takes about 500 ms in our experiments. The second stage involves broadband and narrowband cooling through a 689 nm magneto-optical trap, cooling the atoms to the μK level. This stage is also known as secondary cooling. Broadband cooling in secondary cooling takes about 100 ms, while narrowband cooling in a non-differential optical lattice clock takes about 50 ms. Because the initial power of the lattice laser in this invention is lower than that of lattice lasers in existing technologies, its corresponding trap depth is also smaller. Therefore, the lattice movement acceleration used to separate multiple samples from atomic clusters is also correspondingly lower. Thus, more time is allowed between the movement and acceleration of the optical lattice for the system to stabilize. The total time for cooling and loading multiple atomic samples after secondary narrowband separation was set to 100 ms. During this process, an 813 nm lattice laser was used. P The center frequency of the two ends and P The offset of the center frequency at end 1 t Increase to within 1 time period Drag a portion of the atoms, and then maintain this frequency difference at... t The frequency difference is kept constant for 2 time intervals to drag these atoms further away from the original atomic cluster, thereby achieving resolvable atomic sample separation, and then the frequency difference is... tWithin one time frame, the distance between the two separated atomic clusters linearly returns to zero, thus fixing the distance between them. This process is repeated three times to separate the original large atomic cluster into four smaller ones. Then, the 689 nm narrowband magneto-optical trap is closed, moving the four separated atomic cluster samples back to their spatial positions centered on the zero point of the magnetic field in the magneto-optical trap. The frequency changes of the two one-dimensional horizontal optical lattice devices are synchronized during this process, ensuring the consistency of the two horizontal optical lattices as much as possible, thus forming a differential optical clock structure with eight discrete atomic clusters. Spatially, the centers of the two optical lattices are 200 μm apart vertically to avoid the two one-dimensional optical lattices overlapping and forming a two-dimensional optical lattice, which would hinder atomic cluster separation. The midpoint of this distance also coincides with the zero point of the magnetic field. This design is more effective in eliminating the frequency shift caused by magnetic field gradients along the vertical or horizontal directions. Figure 5 The distribution of atomic samples before and after the splitting of atomic clusters was demonstrated by accelerating and moving the atomic clusters using an optical lattice. Figure 5 (a) is a sample distribution diagram of atomic clusters in a one-dimensional horizontal double optical lattice without optical lattice acceleration and movement. The left diagram shows the projection sample distribution of the atomic clusters in the horizontal plane before splitting, while the right diagram shows the projection sample distribution in the vertical plane. Figure 5 (b) shows the atomic sample distribution of a one-dimensional horizontal double-optical lattice atomic group after acceleration and movement by the optical lattice. Similarly, the left figure shows the projected sample distribution of the atomic group in the horizontal plane after splitting within the lattice, while the right figure shows its projected sample distribution in the vertical plane. Figure 5 In (a) and 5(b), g represents the direction of gravity. In a microgravity environment, it represents the direction perpendicular to the xoy plane.

[0056] On the other hand, the Ramsey clock transition spectral synchronous detection method is used to synchronously excite all differential atomic groups using a clock laser, thereby achieving one-dimensional optical lattice differential optical clock comparison for multiplexing and suppressing some common-mode noise. First, a clock laser is used... Atoms are excited by a pulse, resulting in a 1:1 distribution of atoms in the ground and excited states; then, they undergo free evolution during the dark time of a Ramsey probe under clockless laser irradiation; finally, another pulse is used... A clock laser pulse is used to read the phase difference between two atomic states after free evolution. By comparing them pairwise, the clock transition frequency difference between different atomic groups can be determined. Using absorption imaging normalized detection, an electron multiplication charge-coupled device (ECC) combined with a photomultiplier tube is employed to measure the fluorescence intensity of atoms at different spatial locations in their ground and excited states, thereby obtaining the fractional excitation rate of the clock laser at the excitation frequency. During standard Ramsey line detection, the clock laser applies two pulses to the atoms. Free evolution time between pulses Within, the system accumulates a phase:

[0057] (4)

[0058] in, The eigenfrequency of the transition level in an atomic clock. The frequency of the clock laser is given. For comparing the clock transition frequencies of two atomic samples, their fractional excitation rates can be recorded separately. and As the phase of the clock laser fluctuates during each clock cycle, a series of points can be obtained ( , When the frequencies of the two groups of atoms are exactly the same, then = ,point( , When these frequencies fall on a diagonal, and there is a fixed frequency difference between them, their phase difference remains constant. If the value is constant, then the trajectory of these scattered points is an ellipse. Thus, by fitting the ellipse formed by the fractional excitation rates of the two atomic cluster samples, the phase difference can be calculated, and the clock transition frequency difference between the two atomic samples can be deduced.

[0059] (5)

[0060] And without needing to know the frequency variation of the clock laser itself. For a differential optical clock with multiple atomic samples, the fractional excitation rate in the Ramsey spectral measurement of a single sample is:

[0061] (6)

[0062] in, For contrast, it is a constant between 0 and 1. For clock laser frequency With the The transition eigenfrequency of each atom sample The phase difference. The frequency drift of the clock laser is modeled as a common-mode term: The eigenfrequency of the transition level of an atomic clock The accumulated phase in the Ramsey spectra of the two atomic samples was obtained as follows: and The phase difference between the two samples is .when When the fractional ratios of the two atomic samples are exactly the same, the ellipse degenerates into a diagonal, and when... At this point, the fractional ratio of the excitation rate cosine values ​​of the two atomic samples shows the largest misalignment, resulting in the flattest ellipse. This method, also known as ellipse fitting bias correction, fails when the phase difference is 0 or π. It is only effective within the open interval (0, π) by using the frequency difference between different atomic sample pairs to correct the clock transition frequency of the differential optical clock system. This eliminates the influence of frequency shift caused by some common-mode noise within the system. Compared to systems without bias correction, it can significantly improve the frequency uncertainty of clock closed-loop operation, thereby reducing the system's requirements for clock laser noise limits.

[0063] For example, after separating and moving multiple atomic cluster samples, the next step is to further cool and reduce the optical lattice potential well for the detection of clock transition spectral lines. This process mainly involves... P The laser power at the two ends of the lattice is slowly reduced and then maintained at a well depth of approximately 15-20. E r ( E r A certain value in the recoil energy of the optical lattice is kept constant, and this process lasts for approximately 200 ms. Then, according to the atomic state requirements for clock transition Ramsey spectroscopy, atomic state preparation is performed, which takes approximately 100 ms. Finally, clock transition Ramsey spectroscopy is performed, using two time intervals... T 2 698 nm clock laser The pulses excite the atoms and detect the phase difference between their atomic states; the duration of the two pulses is... T 1. The specific implementation process involves setting the required parameters in the timing control system. T 1 and T The time is 2 seconds, and the corresponding TTL digital pulse signal is output to the microwave switch to control the switching time of the clock laser. The RF drive signal output by the arbitrary function generator to the acousto-optic modulator is controlled to achieve timing control of the clock laser during excitation. The timing control system works in conjunction with the voltage-controlled attenuator to change the intensity of the RF drive signal acting on the acousto-optic modulator, thereby adjusting the corresponding excitation time. The clock laser power required for the pulse. Because... 87 The excited state lifetimes of Sr atomic clock transitions exceed 100 seconds. Electrons in the excited state rarely return to the ground state through spontaneous emission in a short time. Moreover, even if they do return, the 698 nm fluorescence is extremely weak and cannot be directly observed using a photomultiplier tube. Therefore, we need to indirectly measure the number of particles in the ground state using the more easily observable strong dipole transition at 461 nm. First, the number of particles in the ground state can be directly excited using a 461 nm probe light, and the fluorescence intensity at this point is recorded. This fluorescence intensity corresponds to the number of particles in the ground state. N gMeanwhile, the excitation of the probe light also makes the atoms escape from the optical lattice potential, which actually plays a role in emptying the ground state population. Then the excited state population is pumped back to the ground state by the 679, 707 nm repump light 1 On S0, the excited state population is measured by the same method N e The corresponding fluorescence intensity is calculated by normalizing the two recorded fluorescence intensities to obtain the atomic transition probability P e = N e / ( N g + N e ), P e It is also called fractional excitation rate, and this method of collecting the strontium atomic clock transition spectrum is called normalized electron shelving detection. Using this method to detect the clock transition spectrum has another advantage, that is, after normalization, the influence introduced by the fluctuation of the number of atoms in each cycle of the optical clock can be reduced, thereby improving the signal-to-noise ratio of the collected spectrum. Figure 4 The three 461 nm probe light pulses in the middle blue dashed box are usually set to a fixed value of 2-5 ms, the first pulse is used to detect the number of atoms in the ground state, the second pulse is used to detect the number of atoms in the excited state, and the last pulse is used to detect the noise of the light. The fluorescence intensities detected by the first two pulses are respectively subtracted by the fluorescence intensity detected by the last pulse, and the normalized atomic spectrum excitation rate is obtained. The 679, 707 nm repump light pulse time is set to about 10 ms. In this process, the frequency modulation of the lattice light is always in the open state, and the modulation parameter is the best modulation parameter corresponding to the suppression of tunneling at a certain well depth. In this way, a complete clock cycle is realized. After one cycle, the excitation rate of the clock transition Ramsey spectrum at a certain clock laser frequency is obtained. To detect a clock transition Ramsey spectrum, multiple such cycle cycles need to be run, and the frequency of the clock laser does not change in each cycle, but the frequency of the clock laser needs to be scanned by the acousto-optic modulator 5 in each cycle. The step size of each frequency change is the same. This frequency sweeping function is realized by the timing control system and the acousto-optic modulator 5 in the clock laser light path and the arbitrary function generator 3 connected thereto. In this way, a clock transition Ramsey spectrum in a frequency range is obtained. By comparing the clock transition frequencies obtained by detecting the Ramsey spectra of different atomic groups, the frequency difference between different atomic groups is obtained, and the elliptical fitting bias correction method is used to eliminate the influence of common mode noise in the system on the clock transition frequency shift.

[0064] Moreover, the above-described figures are only a schematic representation of the processes comprised in the method according to the exemplary embodiments of the present application, and are not intended to limit purposes. It is readily understood that the processes shown in the above-described figures do not indicate or limit the chronological order of these processes. In addition, it is readily understood that these processes can be executed, for example, synchronously or asynchronously in a plurality of modules.

[0065] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope and spirit of the application being indicated by the following claims.

[0066] It is to be understood that the application is not limited to the precise details of design and construction set forth above and illustrated in the drawings, but that various modifications and changes can be made by those skilled in the art without departing from the scope of the application. The scope of the application is indicated by the appended claims, rather than by the foregoing description.

Claims

1. A method for improving the frequency measurement accuracy of an optical lattice clock in a microgravity environment, characterized in that, The method comprises: two beams of lattice light are divided from one lattice light laser, each of the two beams of lattice light is further divided into two beams of lattice light, and four beams of lattice light form two one-dimensional horizontal optical lattices; wherein the waist positions of the two one-dimensional horizontal optical lattices exist a certain interval in the vertical direction, and the midpoint position is the position of the magnetic field zero point in the magneto-optical trap, and the projections of the axial directions of the two horizontal optical lattices in the vertical plane are parallel to each other, and the projections in the horizontal plane are perpendicular to each other; two beams of clock laser are divided from one clock laser source to excite different atomic groups in the two one-dimensional horizontal optical lattices; an acousto-optic modulator with the same parameters is loaded on the light path of each beam of lattice light for linear frequency shift and modulation of the lattice light frequency, wherein the acousto-optic modulator loaded on the light path of the two beams of lattice light for generating one one-dimensional horizontal optical lattice is connected to an arbitrary function generator, the acousto-optic modulator loaded on the light path of the two beams of lattice light for generating another one-dimensional horizontal optical lattice is connected to another arbitrary function generator; an acousto-optic modulator is also loaded before the clock laser is divided into two beams for scanning the clock laser frequency, and the acousto-optic modulator on the clock laser is connected to a third arbitrary function generator; the three arbitrary function generators are all traced back to the same hydrogen clock as the frequency reference source; the two beams of lattice light are divided from one lattice light laser, each of the two beams of lattice light is further divided into two beams of lattice light, and four beams of lattice light form two one-dimensional horizontal optical lattices, specifically: the lattice light output by the lattice light laser is divided into two beams by a polarization beam splitter, each beam of lattice light is further divided into two beams of lattice light by a polarization beam splitter, and the four beams of lattice light are first lattice light, second lattice light, third lattice light and fourth lattice light; wherein the initial optical powers of the first lattice light and the second lattice light are set to be the same, the initial optical powers of the third lattice light and the fourth lattice light are set to be the same; the initial optical powers of the first lattice light and the second lattice light are greater than the initial optical powers of the third lattice light and the fourth lattice light; the first lattice light and the second lattice light are incident on the atomic group captured by the magneto-optical trap at a 90° angle, the third lattice light and the fourth lattice light are incident on the atomic group captured by the magneto-optical trap at a 90° angle, and the third lattice light is opposite to one of the first lattice light and the second lattice light, and the fourth lattice light is opposite to the other of the first lattice light and the second lattice light, forming two one-dimensional horizontal optical lattices; a half-wave plate, a linear polarizer and a convex lens are connected in sequence at the end of the light path of each beam of lattice light, wherein: the half-wave plate and the linear polarizer are used to adjust the polarization direction of each beam of lattice light, so that the polarization direction remains vertical; the convex lens is used to fix the waist position of the lattice light at the center of the atomic group in the magneto-optical trap.

2. The method of claim 1, wherein, the two beams of clock laser are divided from one clock laser source to excite different atomic groups in the two one-dimensional horizontal optical lattices, specifically: the clock laser output by the clock laser is divided into two beams by a polarization beam splitter, which are first clock laser and second clock laser, the first clock laser is combined with one of the third lattice light and the fourth lattice light through a dichroic mirror, and the second clock laser is combined with the other of the third lattice light and the fourth lattice light through a dichroic mirror.

3. The method of claim 1, wherein, The polarization direction of the clock laser is adjusted by adding a half-wave plate to each of the two clock lasers, so that the polarization direction of the clock laser is consistent with the polarization direction of the lattice light; then a convex lens is combined with the convex lens in the lattice light beam, so that the waist size and position of the clock laser are adjusted.

4. The method of claim 1, wherein, A microwave switch, a voltage-controlled attenuator and a time sequence control system are arranged between the acousto-optic modulator and the arbitrary function generator. The time sequence control system generates a series of TTL digital pulse signals, which are transmitted to the microwave switch, and then the microwave switch turns on or off the output radio frequency signal of the arbitrary function generator according to the instruction of the time sequence system, so as to realize the switching of the lattice laser and the control of the action time of the linear frequency shift signal and the frequency modulation signal. The time sequence control system transmits a time-varying analog voltage waveform to the voltage-controlled attenuator, so as to realize variable attenuation of the radio frequency signal strength.

5. The method of claim 1, wherein, The modulation parameters suitable for the specific optical lattice well depth are selected by Floquet design technology, and the specific process is as follows: Two identical modulation radio frequency signals are output by an arbitrary function generator, both of which are sine modulation, and the carrier frequency and modulation parameters are completely consistent, then the two signals are loaded on the acousto-optic modulators of the first and second lattice lights, and the start time and action time of the signals are controlled by the time sequence control system and the microwave switch; the parameters of the sine modulation signal are selected by the tunneling rate modulation function, that is, the modulation depth corresponding to the zero point of the first Bessel function; wherein the parameters of the frequency modulation function loaded on the two one-dimensional horizontal optical lattices must be completely consistent.

6. The method of claim 5, wherein, The acceleration and movement of the optical lattice are realized by changing the frequency difference of the two counter-propagating lattice lights in the two one-dimensional horizontal optical lattices, so as to prepare multiple atomic samples required by the differential optical clock, and the specific process is as follows: Two radio frequency signals without modulation are output by another arbitrary function generator at the initial time, and the carrier frequency of the two signals is completely consistent with the carrier frequency of the radio frequency signal output by the arbitrary function generator, then the two signals are loaded on the acousto-optic modulators of the third and fourth lattice lights, and the start time and action time of the signals are controlled by the time sequence control system, the microwave switch and the acousto-optic modulator; the output frequency of the unmodulated radio frequency signal is changed within a given action time period by the time sequence control system, the arbitrary function generator and the acousto-optic modulator, so as to introduce the frequency difference with the carrier frequency of the radio frequency signal loaded on the acousto-optic modulators of the first and second lattice lights, thereby accelerating the optical lattice, splitting the atomic group in the optical lattice, and moving the split atomic group to the position symmetric to the center of the magnetic field zero point of the magnetic optical trap, so as to prepare multiple atomic group samples required by the differential optical clock.

7. The method of claim 1, wherein, The excitation process involves using two time intervals. The frequency scanning function of the clock laser is achieved through a pulse, using a timing control system, an acousto-optic modulator on the clock laser optical path, and a third arbitrary function generator connected to it. This allows for the detection of the complete Ramsey spectral lines within a given frequency band. Simultaneously, the timing control system, in conjunction with a microwave switch and the acousto-optic modulator, controls two pulses during the excitation process. The duration of the laser pulse and the interval between two pulses are controlled; and the timing control system, voltage-controlled attenuator, and acousto-optic modulator work together to adjust the corresponding excitation times. The required clock laser power for the pulse is used to achieve synchronous detection of the Ramsey spectral lines of the clock transition and closed-loop locking of the clock transition frequency. The clock transition frequencies obtained from multiple atomic samples are compared pairwise, and then the elliptic fitting correction bias method is used to eliminate the influence of common-mode noise on the clock transition frequency shift.

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