Gravity measurement method, device and atomic gravimeter

Abstract

The application discloses a gravity measurement method and device and an atomic gravimeter, and relates to the technical field of quantum measurement. The method comprises the following steps: in an interference stage, a first selection current is applied to an upper selection coil, a second selection current is applied to a lower selection coil, so that the upper selection coil and the lower selection coil jointly generate a first selection magnetic field to form a first selection region, and a first interference current is applied to a bias magnetic field coil, so that the bias magnetic field coil generates a first bias magnetic field to form a first bias magnetic field region, and the direction of a quantization axis of an atomic group in the interference stage is maintained. Compared with the prior art, the selection coil is continuously powered after the selection stage is completed, the selection magnetic field is superimposed on the bias magnetic field in the interference stage through the joint action of the selection coil and the bias magnetic field coil, the effective movement distance of the atomic group in the uniform magnetic field region is prolonged under the condition that the physical size of the atomic gravimeter is unchanged, and therefore the precision of the gravity measurement is improved.

Description

Technical Field

[0001] This application relates to the field of quantum measurement technology, and in particular to a gravity measurement method, device and atomic gravimeter. Background Technology

[0002] An atomic gravimeter is a high-precision gravity measurement device widely used in geological exploration, resource detection, and inertial navigation. Its basic principle is to allow a cluster of atoms to fall freely in a vacuum chamber, and then precisely measure gravitational acceleration through the interaction of laser light with the atoms.

[0003] Currently, traditional laboratory atomic gravimeters are bulky, with vacuum chambers typically exceeding 1 meter in length. The long falling distance of atomic clusters and ample measurement time result in extremely high measurement accuracy. However, these devices are heavy, immobile, and can only be used within laboratories.

[0004] To facilitate outdoor measurements, portable miniaturized atomic gravimeters have emerged in recent years, shortening the vacuum cavity length to 20-40 cm. In these devices, atomic clusters undergo three functional stages: a cooling stage (capturing and cooling the atoms), a state selection stage (selecting atoms from multiple magnetic energy levels for measurement), and an interference stage (allowing the atoms to fall freely in a bias magnetic field and interact with a laser to extract gravitational information). The magnetic fields for each stage are provided independently by the magneto-optical trap coil, the state selection coil, and the bias magnetic field coil, respectively. After one stage is completed, the coil of the previous stage is de-energized and shut down, while the coil of the next stage is energized and turned on. In this operating mode, the state selection coil only functions during the state selection stage and is de-energized after completion; the interference stage is solely provided by the bias magnetic field coil. Because the atomic clusters must complete state selection before entering the interference stage, the selection region occupies limited axial space within the vacuum cavity, compressing the free fall distance and shortening the free evolution time during the interference stage, resulting in decreased gravity measurement accuracy. Meanwhile, the bias magnetic field coil in the compact structure exhibits significant end effects when operating alone, the range of the uniform magnetic field area is limited, and external environmental interference is more likely to affect the measurement results, further reducing the measurement accuracy.

[0005] Therefore, how to increase the movement time of atoms during the interference phase without changing the size of the device is an urgent problem to be solved. Summary of the Invention

[0006] The main objective of this application is to provide a gravity measurement method, apparatus, and atomic gravimeter, aiming to solve the technical problem of how to increase the distance of atomic movement during the interference phase without changing the size of the device.

[0007] To achieve the above objectives, this application proposes a gravity measurement method applied to an atomic gravimeter. The atomic gravimeter has a magneto-optical trap coil, a state selection coil, and a bias magnetic field coil sequentially arranged along the axial direction of the vacuum cavity. The magneto-optical trap coil is used to cool atomic clusters. The state selection coil includes an upper state selection coil and a lower state selection coil, used to generate a state selection magnetic field to form a state selection region, which is used to select the state of the atomic clusters. The bias magnetic field coil is used to generate a uniform bias magnetic field to form a bias magnetic field region. The state-selected atomic clusters interfere with each other in the bias magnetic field region. The interfered atomic clusters then enter the detection region for detection, obtaining gravity measurement results. The method includes: During the interference phase, a first driving current is applied to the upper selected state coil, and a second driving current is applied to the lower selected state coil. There is a first preset ratio between the first driving current and the second driving current, so that the upper selected state coil and the lower selected state coil jointly generate a first selected state magnetic field to form a first selected state region. A third driving current is applied to the bias magnetic field coil, so that the bias magnetic field coil generates a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction of the atomic clusters in the interference. Wherein, the first selected state region overlaps with at least a portion of the bias magnetic field region to form an overlapping region. The overlapping region extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

[0008] In one embodiment, the steps prior to the interference phase further include: During the state selection phase, a fourth driving current is applied to the upper state selection coil and a fifth driving current is applied to the lower state selection coil, so that the upper state selection coil and the lower state selection coil jointly generate a second state selection magnetic field to form a second state selection region.

[0009] In one embodiment, during the selection phase, a sixth driving current is applied to the bias magnetic field coil to generate a bias magnetic field, providing a bias-stabilized quantization axis for the atomic group in the selection phase.

[0010] In one embodiment, a second preset ratio exists between the fourth driving current and the fifth driving current.

[0011] In one embodiment, the steps prior to the selection phase further include: During the cooling phase, a seventh driving current is applied to the magneto-optical trap coil to generate a cooling magnetic field to form a cooling region, thereby cooling and trapping the atomic clusters.

[0012] In one embodiment, after the step of providing a bias-stabilized quantization axis to the atomic group in the selected state, the method further includes: During the detection phase, the first driving current applied to the upper-selection coil and the second driving current applied to the lower-selection coil are stopped, and the third driving current of the bias magnetic field coil is maintained or disconnected according to the preset detection mode; The interference fringe information of the atomic group during the detection phase is obtained, and the gravity measurement result is obtained based on the interference fringe information.

[0013] In one embodiment, after the steps of acquiring the interference fringe information of the atomic group during the detection phase and obtaining the gravity measurement result based on the interference fringe information, the method further includes: Obtain the free evolution time of the atomic group during the interference process; Based on the free evolution time and the magnetic field distribution data of the atomic cluster in the extended bias magnetic field region, the phase shift introduced by the second-order Zeeman effect in the interference stage of the atomic cluster is obtained; wherein, the extended bias magnetic field region includes the bias magnetic field region and the overlapping region; The gravity measurement results are corrected based on the phase shift.

[0014] Furthermore, to achieve the above objectives, this application also proposes a gravity measuring device, the device comprising: In the interference phase, the current control module applies a first driving current to the upper selection coil and a second driving current to the lower selection coil. A first preset ratio exists between the first driving current and the second driving current, so that the upper selection coil and the lower selection coil jointly generate a first selection magnetic field to form a first selection region. A third driving current is applied to the bias magnetic field coil to generate a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction for the atomic clusters in the interference. Wherein, the first selected state region overlaps with at least a portion of the bias magnetic field region to form an overlapping region. The overlapping region extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

[0015] Furthermore, to achieve the above objectives, this application also proposes an atomic gravimeter, comprising: a magneto-optical trap coil, a state selection coil, and a bias magnetic field coil sequentially arranged along the axial direction of a vacuum cavity; the magneto-optical trap coil being used to cool atomic clusters; the state selection coil including an upper state selection coil and a lower state selection coil being used to generate a state selection magnetic field to form a state selection region, the state selection region being used to state-select the atomic clusters; the bias magnetic field coil being used to generate a uniform bias magnetic field to form a bias magnetic field region, the state-selected atomic clusters interfering with each other in the bias magnetic field region; the interfering atomic clusters entering the detection region for detection, thereby obtaining gravity measurement results; The atomic gravimeter further includes a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the gravity measurement method as described above.

[0016] In one embodiment, the atomic gravimeter further includes an inner magnetic shield and an outer magnetic shield. The inner magnetic shield is disposed outside the bias magnetic field coil, and the outer magnetic shield is disposed outside the vacuum cavity. The inner magnetic shield constrains the edge magnetic field of the bias magnetic field coil to increase the uniform magnetic field range of the bias magnetic field coil. The outer magnetic shield attenuates the ambient magnetic field outside the vacuum cavity.

[0017] One or more technical solutions proposed in this application have at least the following technical effects: This application improves the accuracy of gravity measurement by applying a first driving current to the upper selection coil and a second driving current to the lower selection coil during the interference phase. A first preset proportional relationship exists between the first and second driving currents, causing the upper and lower selection coils to jointly generate a first selection magnetic field to form a first selection region. A third driving current is applied to the bias magnetic field coil to generate a bias magnetic field to form a bias magnetic field region, thus maintaining the quantization axis direction of the atomic clusters during interference. The first selection region and the bias magnetic field region at least partially overlap, forming an overlapping region. This overlapping region serves as a uniform axial extension of the bias magnetic field region, extending it. The selected atomic clusters complete interference within this extended bias magnetic field region. Compared to existing methods, this application continues to energize the selection coil after the selection phase, allowing it to work in conjunction with the bias magnetic field coil during the interference phase. This superimposes the selection magnetic field onto the bias magnetic field, extending the effective movement distance of the atomic clusters within the uniform magnetic field region while maintaining the physical dimensions of the atomic gravimeter, thereby improving the overall accuracy of gravity measurement. Attached Figure Description

[0018] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a distribution map of the regions traversed by atomic cluster motion in the existing technology; Figure 2 This is a distribution map of the area traversed by the movement of atomic groups in the first embodiment of the gravity measurement method of this application; Figure 3 This is a structural diagram of the atomic gravimeter in the first embodiment of the gravity measurement method of this application; Figure 4 This is a flowchart illustrating the first embodiment of the gravity measurement method of this application; Figure 5 This is a schematic diagram of the first process of the second embodiment of the gravity measurement method of this application; Figure 6 This is a schematic diagram of the second process of the second embodiment of the gravity measurement method of this application; Figure 7 This is a flowchart illustrating the third embodiment of the gravity measurement method of this application; Figure 8 This is a schematic diagram of the module structure of the gravity measuring device according to an embodiment of this application; Figure 9 This is a schematic diagram of the device structure of the hardware operating environment involved in the gravity measurement method in the embodiments of this application.

[0021] Explanation of icon numbers: 1. Vacuum cavity; 2. Magneto-optical trap coil; 3. Selective coil; 31. Upper selective coil; 32. Lower selective coil; 4. Bias magnetic field coil; 5. Inner magnetic shield; 6. Outer magnetic shield; A. Cooling region; B. Selective region; C. Interference region; D. Detection region; E. Overlapping region.

[0022] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0023] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.

[0024] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.

[0025] Because atomic gravimeters are high-precision gravity measurement devices, they are widely used in fields such as geological exploration, resource detection, and inertial navigation. Their basic principle is to allow atomic clusters to fall freely in a vacuum chamber, and then precisely measure gravitational acceleration through the interaction of laser light with the atoms.

[0026] Currently, traditional laboratory atomic gravimeters are bulky, with vacuum chambers typically exceeding 1 meter in length. The long falling distance of atomic clusters and ample measurement time result in extremely high measurement accuracy. However, these devices are heavy, immobile, and can only be used within laboratories.

[0027] To facilitate outdoor measurements, portable miniaturized atomic gravimeters have emerged in recent years, shortening the length of the vacuum chamber to 20 to 40 centimeters. In these devices, atomic clusters undergo three functional stages: a cooling stage (capturing and cooling atoms), a state selection stage (selecting atoms from multiple magnetic energy levels for measurement), and an interference stage (allowing atoms to fall freely in a bias magnetic field and interact with a laser to extract gravitational information).

[0028] Reference Figure 1 , Figure 1 This is a distribution map of the regions traversed by atomic motion in existing technology. (Through...) Figure 1 It is known that in existing technologies, when atomic clusters move within a portable miniaturized atomic gravimeter, they sequentially pass through a cooling region provided by the magneto-optical trap preparation stage, a selection region provided by the selection stage, and an interference region provided by the interference stage. The magnetic fields for these three stages are independently provided by the magneto-optical trap coil, the selection coil, and the bias magnetic field coil, respectively. After one stage is completed, the coil of the previous stage is de-energized and shut off, while the coil of the next stage is energized and turned on. In this operating mode, the selection coil only functions during the selection stage and is de-energized afterward. The interference stage is solely provided by the bias magnetic field coil. Because the atomic cluster must complete the selection process before entering the interference stage, the selection region occupies limited axial space within the vacuum cavity, compressing the free fall distance and shortening the free evolution time during the interference stage, leading to a decrease in gravity measurement accuracy. Simultaneously, the bias magnetic field coil exhibits significant end effects when operating alone in a compact structure, resulting in a limited range of uniform magnetic field areas. External environmental interference is also more likely to affect the measurement results, further reducing measurement accuracy.

[0029] Therefore, how to increase the movement time of atoms during the interference phase without changing the size of the device is an urgent problem to be solved.

[0030] The main solution of this application embodiment is as follows: During the interference stage, a first driving current is applied to the upper selection coil 31 and a second driving current is applied to the lower selection coil 32. There is a first preset ratio between the first driving current and the second driving current, so that the upper selection coil 31 and the lower selection coil 32 jointly generate a first selection magnetic field to form a first selection region B. A third driving current is applied to the bias magnetic field coil 4, so that the bias magnetic field coil 4 generates a bias magnetic field to form a bias magnetic field region, which maintains the quantization axis direction for the atomic clusters in the interference. The first selection region B overlaps with the bias magnetic field region to form an overlapping region E. The overlapping region E extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete the interference in the extended bias magnetic field region. Compared to existing methods, this application improves the accuracy of gravity measurement by keeping the selection coil 3 energized after the selection phase is completed, and working together with the bias magnetic field coil 4 during the interference phase to superimpose the selection magnetic field onto the bias magnetic field. This extends the effective movement distance of the atomic gravimeter in the uniform magnetic field region while keeping the physical dimensions of the atomic gravimeter unchanged.

[0031] It should be noted that the executing entity in this embodiment can be a gravity measuring device, an atomic gravimeter, or the like capable of performing the above functions. The following description uses an atomic gravimeter (hereinafter referred to as the device) as an example to illustrate this embodiment and the subsequent embodiments.

[0032] Based on this, embodiments of this application provide a gravity measurement method, referring to... Figure 2 , Figure 3 as well as Figure 4 , Figure 2 This is a distribution map of the area traversed by the movement of atomic groups in the first embodiment of the gravity measurement method of this application; Figure 3 This is a structural diagram of the atomic gravimeter in the first embodiment of the gravity measurement method of this application; Figure 4 This is a flowchart illustrating the first embodiment of the gravity measurement method of this application.

[0033] In this embodiment, the method is applied to an atomic gravimeter. The atomic gravimeter has a magneto-optical trap coil 2, a selection coil 3, and a bias magnetic field coil 4 arranged sequentially along the axial direction of the vacuum cavity 1. The magneto-optical trap coil 2 is used to cool the atomic clusters. The selection coil 3 includes an upper selection coil 31 and a lower selection coil 32, used to generate a selection magnetic field to form a selection region B, which is used to select the atomic clusters. The bias magnetic field coil 4 is used to generate a uniform bias magnetic field to form a bias magnetic field region. The selected atomic clusters interfere with each other in the bias magnetic field region. The interfered atomic clusters then enter the detection region D for detection, obtaining gravity measurement results. The method includes: Step S10: During the interference phase, a first driving current is applied to the upper selection coil 31 and a second driving current is applied to the lower selection coil 32. A first preset ratio relationship exists between the first driving current and the second driving current, so that the upper selection coil 31 and the lower selection coil 32 jointly generate a first selection magnetic field to form a first selection region B. A third driving current is applied to the bias magnetic field coil 4, so that the bias magnetic field coil 4 generates a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction for the atomic clusters in the interference. Step S20: Wherein, the first selected state region B overlaps with at least a portion of the bias magnetic field region to form an overlapping region E. The overlapping region E extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

[0034] It should be noted that vacuum chamber 1 can be a sealed cavity in an atomic gravimeter that allows atomic clusters to fall freely and provides an ultra-high vacuum environment; its internal vacuum level is typically better than 10. -6 Pa, to reduce the interference of background gas on the movement of atomic groups.

[0035] The magneto-optical trap coil 2 can be a pair of circular Helmholtz coils. When working, the currents in the two coils are in opposite directions, generating a gradient magnetic field. This, combined with the cooling light, forms a magneto-optical trap, which is used to cool atomic clusters to the μK level.

[0036] The state selection coil 3 can be a pair of Helmholtz coils, divided into two parts: the upper state selection coil 31 and the lower state selection coil 32. When energized, it generates a state selection magnetic field for selecting atoms of a single magnetic level.

[0037] The bias magnetic field coil 4 can be a solenoid coil tightly wound around the outer wall of the vacuum cavity 1. When energized, it generates a uniform bias magnetic field distributed along the axial direction of the vacuum cavity 1, providing a quantization axis for the atomic group.

[0038] The selected state region B can be the spatial range covered by the selected state magnetic field within the vacuum cavity 1, where the atomic group completes the selection of magnetic quantum energy levels.

[0039] The bias magnetic field region can be the spatial range covered by the bias magnetic field within the vacuum cavity 1, and the atomic clusters complete the interference process within this region.

[0040] The detection region D can be the spatial region located below the bias magnetic field region within the vacuum cavity 1. The interfering atomic clusters enter this region, are irradiated by Raman light, and generate fluorescence signals.

[0041] The first driving current can be the driving current applied to the upper selection coil 31 during the interference phase. In this embodiment, the first driving current is 0.40A. The second driving current can be the driving current applied to the lower selection coil 32 during the interference phase. In this embodiment, the second driving current is 0.08A.

[0042] The first preset ratio can be a ratio between the first driving current and the second driving current during the interference stage, used to enable the upper selection coil 31 and the lower selection coil 32 to generate a magnetic field distribution suitable for interference. In this embodiment, the first preset ratio is 5:1.

[0043] The third driving current can be the driving current applied to the bias magnetic field coil 4 during the interference phase. In this embodiment, the value of the third driving current is 0.10A.

[0044] The first selected magnetic field can be the magnetic field distribution jointly generated by the first driving current and the second driving current after the upper selected coil 31 and the lower selected coil 32 are applied, and is used to form an extended uniform magnetic field region by superimposing it with the bias magnetic field during the interference stage.

[0045] The first selected state region B can be the spatial range covered by the first selected state magnetic field within the vacuum cavity 1. The quantization axis can be a reference direction determined by the direction of the bias magnetic field, along which the magnetic moments of atoms are quantized. The polarization direction of the Raman laser is usually kept at a fixed angle to the quantization axis to achieve effective transition coupling.

[0046] The overlapping region E can be the spatial region where the first selected state region B and the bias magnetic field region overlap axially.

[0047] The extended bias magnetic field region can be the uniform magnetic field coverage area formed by connecting the bias magnetic field region and the overlapping region E along the axial direction.

[0048] In its implementation, the atomic gravimeter sequentially mounts a magneto-optical trap coil 2, a selection coil 3, and a bias magnetic field coil 4 along the axial direction of vacuum cavity 1. After being cooled and captured in the cooling magnetic field generated by the magneto-optical trap coil 2, the atomic clusters fall freely along the axial direction of vacuum cavity 1 under the influence of gravity. In conventional schemes, the selection coil 3 is de-energized and shut down after the selection phase, leaving only the bias magnetic field coil 4 operating during the interference phase. The bias magnetic field coil 4 has a solenoid structure, exhibiting a significant edge effect at its ends. Magnetic field lines diffuse outwards from both ends of the coil, compressing the axial range of the uniform magnetic field, limiting it to an area of ​​approximately 190 mm inside the coil. Within this region, the atoms complete interference, resulting in a limited free fall distance, a short free evolution time, and constrained gravity measurement accuracy. Furthermore, the compact structure of the bias magnetic field coil 4 exacerbates the end effect, making it difficult to effectively compensate for remanence and magnetic field gradients, further reducing magnetic field uniformity.

[0049] In this embodiment, after entering the interference stage, the device applies a first driving current to the upper selection coil 31, a second driving current to the lower selection coil 32, and a third driving current to the bias magnetic field coil 4, instead of energizing only the bias magnetic field coil 4 as in conventional solutions. The energization of the upper and lower selection coils 31 and 32 together generates a first selection magnetic field, forming a first selection region B within the vacuum cavity 1. The third driving current flowing through the bias magnetic field coil 4 generates a bias magnetic field, forming a bias magnetic field region within the vacuum cavity 1. The first selection region B and the bias magnetic field region overlap axially by at least a portion of their space, forming an overlapping region E. Within the overlapping region E, the first selection magnetic field and the bias magnetic field superimpose, causing the uniform magnetic field range of the bias magnetic field region to extend axially upwards to the lower middle region of the selection coil 3. The overlapping region E, as a uniform axial extension of the bias magnetic field region, together with the bias magnetic field region, constitutes the extended bias magnetic field region. After selection, the atomic clusters complete interference in the extended bias magnetic field region. The effective movement distance of the atomic clusters in the uniform magnetic field increases by approximately 5 cm, and the free evolution time reaches 80 to 90 milliseconds. The first driving current and the second driving current are configured with a 5:1 asymmetric ratio, i.e., the current in the upper selection coil 31 is 0.40 A and the current in the lower selection coil 32 is 0.08 A. This ensures a smooth transition between the first selection magnetic field and the bias magnetic field at the junction, and the rate of change of magnetic induction intensity in the extended bias magnetic field region is less than 10. -4 The bias magnetic field maintains the quantization axis direction for the atomic clusters during interference, ensuring that the magnetic moments of the atomic clusters are always aligned along the bias magnetic field direction. This guarantees that the polarization direction of the Raman laser maintains a fixed angular relationship with the quantization axis, allowing the interference process to proceed stably. In traditional schemes, the uniform region is only about 190 mm when the bias magnetic field coil 4 works alone, and the free evolution time is limited. In this embodiment, by having the state selection coil 3 and the bias magnetic field coil 4 work together during the interference stage, the uniform magnetic field range is extended to about 240 mm within the same physical cavity length, thus extending the effective interference distance of the atoms without increasing the size of the equipment.

[0050] For example, after the atomic cluster completes state selection and enters the interference stage, the device applies a first driving current of 0.40A to the upper selection coil 31 and a second driving current of 0.08A to the lower selection coil 32, with a ratio of 5:1. Simultaneously, a third driving current of 0.10A is applied to the bias magnetic field coil 4. The upper and lower selection coils 31 and 32 together generate a first selection magnetic field, forming a first selection region B. The bias magnetic field coil 4 generates a bias magnetic field, forming a bias magnetic field region. The first selection region B and the bias magnetic field region overlap axially, forming an overlapping region E. The uniform magnetic field range of the bias magnetic field region extends axially upwards to the lower part of the selection coil 3, together with the overlapping region E, constituting an extended bias magnetic field region with a total length of approximately 240mm. The selected atomic cluster completes interference in the extended bias magnetic field region, with a free evolution time of 85ms.

[0051] In this embodiment, during the interference phase, a first driving current is applied to the upper selection coil 31 and a second driving current is applied to the lower selection coil 32. A first preset proportional relationship exists between the first and second driving currents, causing the upper and lower selection coils 31 and 32 to jointly generate a first selection magnetic field to form a first selection region B. A third driving current is applied to the bias magnetic field coil 4 to generate a bias magnetic field to form a bias magnetic field region, maintaining the quantization axis direction for the atomic clusters during interference. The first selection region B overlaps at least partially with the bias magnetic field region, forming an overlapping region E. This overlapping region E serves as a uniform axial extension of the bias magnetic field region, extending it. The selected atomic clusters complete the interference within this extended bias magnetic field region. Compared to existing methods, this application, by keeping the selection coil 3 energized after the selection phase, works in conjunction with the bias magnetic field coil 4 during the interference phase to superimpose the selection magnetic field onto the bias magnetic field. This extends the effective movement distance of the atomic clusters within the uniform magnetic field region while maintaining the physical dimensions of the atomic gravimeter, thereby improving the accuracy of gravity measurement.

[0052] Based on the first embodiment of this application, a second embodiment of this application is proposed. In the second embodiment, content that is the same as or similar to that in the first embodiment described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 3 as well as Figure 5 , Figure 5 This is a schematic diagram of the first process of the second embodiment of the gravity measurement method of this application.

[0053] In this embodiment, the steps prior to the interference stage further include: Step S11: In the state selection stage, a fourth driving current is applied to the upper state selection coil 31 and a fifth driving current is applied to the lower state selection coil 32, so that the upper state selection coil 31 and the lower state selection coil 32 jointly generate a second state selection magnetic field to form a second state selection region B.

[0054] It should be noted that the state selection stage can be the stage of screening the magnetic quantum energy levels of the atomic group after it has completed cooling and capture and before it enters the interference stage.

[0055] The fourth driving current can be the driving current applied to the upper selection coil 31 during the selection phase. In this embodiment, the value of the fourth driving current is 0.20A.

[0056] The fifth driving current can be the driving current applied to the lower selection coil 32 during the selection phase. In this embodiment, the fifth driving current is 0.20A.

[0057] The second state-selection magnetic field can be the magnetic field distribution jointly generated by the fourth and fifth driving currents applied to the upper state-selection coil 31 and the lower state-selection coil 32, and is used to screen atomic groups for magneton energy levels during the state-selection stage. The second state-selection region B can be the spatial range covered by the second state-selection magnetic field within the vacuum cavity 1.

[0058] In its implementation, after the atomic cluster is cooled and captured in the cooling magnetic field generated by the magneto-optical trap coil, it falls freely along the axial direction of the vacuum cavity under the influence of gravity, entering the selection phase. Once the device detects that the atomic cluster has entered the selection phase, a fourth driving current is applied to the upper selection coil 31, and a fifth driving current is applied to the lower selection coil 32. No driving current is applied to the bias magnetic field coil 4 during the selection phase. The energization of the upper and lower selection coils together generates a second selection magnetic field, forming a second selection region within the vacuum cavity. This second selection magnetic field spatially separates atoms at different magnetic level energy levels, retaining only atoms at the target magnetic level.

[0059] Further, refer to Figure 6 , Figure 6 This is a second flowchart illustrating the second embodiment of the gravity measurement method of this application.

[0060] In this embodiment, step S12: During the state selection stage, a sixth driving current is applied to the bias magnetic field coil 4 to generate a bias magnetic field, providing a biased stable quantization axis for the atomic group in the state selection.

[0061] It should be noted that the sixth driving current can be the driving current applied to the bias magnetic field coil 4 during the selection phase. In this embodiment, the value of the sixth driving current is 0.10A.

[0062] In its implementation, after the atomic cluster is cooled and captured in the cooling magnetic field generated by the magneto-optical trap coil 2, it falls freely along the axis of the vacuum cavity 1 under the influence of gravity, entering the selection phase. Once the device detects that the atomic cluster has entered the selection phase, it applies a fourth driving current to the upward selection coil 31, a fifth driving current to the downward selection coil 32, and a sixth driving current to the bias magnetic field coil 4. The energization of the upward and downward selection coils 31 and 32 together generates a second selection magnetic field, forming a second selection region B within the vacuum cavity 1. The bias magnetic field coil 4, after the sixth driving current is applied, generates a bias magnetic field, providing a quantization axis for the selected atomic cluster. After the direction of the quantization axis is determined, atoms at different magnetic levels undergo energy level splitting due to the Zeeman effect. The second selection magnetic field, based on this energy level splitting, spatially separates atoms at different magnetic levels, retaining only atoms at the target magnetic level. The state selection phase also requires a bias magnetic field to provide a quantization axis to induce Zeeman splitting. After state selection is completed, the state selection coil 3 is de-energized, while the bias magnetic field coil 4 remains energized between the state selection and interference phases. In this embodiment, the state selection coil 3 is not immediately de-energized after state selection but continues to be energized in the subsequent interference phase, working in conjunction with the bias magnetic field coil 4 to form an extended bias magnetic field region during the interference phase. The fourth and fifth driving currents are symmetrically configured during the state selection phase, both being 0.20A, to generate a state selection magnetic field gradient suitable for atom screening.

[0063] It is important to emphasize that the stable quantization axis is provided by the bias magnetic field and is unrelated to the selection magnetic field. In this embodiment, no driving current is applied to the bias magnetic field coil during the selection phase, and no bias magnetic field provides the quantization axis during this phase. The selection process of the atomic group is completed under conditions without a bias magnetic field. Only after the atomic group completes the selection and enters the interference phase is the device applied a third driving current to the bias magnetic field coil, which generates a bias magnetic field to provide the quantization axis for the atomic group in the interference. Because the bias magnetic field coil remains de-energized during the selection phase, the atomic group needs to enter the bias magnetic field region from the region without a bias magnetic field after completing the selection, resulting in relatively weak stability when entering the bias magnetic field. In another implementation, a driving current can be applied to the bias magnetic field coil during the selection phase, so that the bias magnetic field provides the quantization axis for the atomic group during the selection phase. After the selection, the atomic group remains in a bias magnetic field environment from the selection phase to the interference phase, resulting in better stability.

[0064] For example, after the atomic cluster is released from cooling region A, it enters the selection phase. The device applies a fourth driving current of 0.20A to the upper selection coil 31, a fifth driving current of 0.20A to the lower selection coil 32, and a sixth driving current of 0.10A to the bias magnetic field coil 4. The upper and lower selection coils 31 and 32 together generate a second selection magnetic field, forming a second selection region B. The bias magnetic field coil 4 generates a bias magnetic field, providing a vertical quantization axis for the atomic cluster, causing Zeeman splitting of different magnetic level magnetic particles. The second selection magnetic field filters out atoms with the mF=0 magnetic level based on the energy level splitting.

[0065] Furthermore, in this embodiment, there is a second preset ratio relationship between the fourth driving current and the fifth driving current.

[0066] It should be noted that the second preset ratio can be a pre-set ratio between the fourth driving current and the fifth driving current during the selection phase. This ratio is used to generate a magnetic field distribution suitable for atom screening in the upper selection coil 31 and the lower selection coil 32, while providing a directionally stable quantized axis for the atomic clusters in the selection phase. In this embodiment, the second preset ratio is 1:1, that is, the fourth driving current and the fifth driving current are equal, both being 0.20A.

[0067] In the specific implementation, after the atomic cluster is cooled and captured in the cooling magnetic field generated by the magneto-optical trap coil 2, it falls freely along the axis of the vacuum cavity 1 under the action of gravity and enters the selection stage. After the device detects that the atomic cluster has entered the selection stage, it determines the values ​​of the fourth driving current and the fifth driving current according to the second preset ratio. The fourth driving current is applied to the upper selection coil 31, and the fifth driving current is applied to the lower selection coil 32. In this embodiment, the second preset ratio is 1:1, that is, the upper selection coil 31 and the lower selection coil 32 are supplied with equal currents, both 0.20A, so that the upper selection coil 31 and the lower selection coil 32 jointly generate the second selection magnetic field. When the upper selection coil 31 and the lower selection coil 32 are configured with symmetrical currents, the second selection magnetic field forms a gradient distribution suitable for atomic screening along the axis of the vacuum cavity 1. Atoms of different magnetic sub-levels are spatially separated under the action of the magnetic field gradient, and atoms of the target magnetic sub-level are retained. In this embodiment, the selection coil 3 uses a second preset ratio to determine the current value during the selection phase, which provides a current configuration basis for switching to the first preset ratio during the subsequent interference phase.

[0068] Furthermore, in this embodiment, the steps prior to the selection phase further include: Step S13: During the cooling stage, a seventh driving current is applied to the magneto-optical trap coil 2 to generate a cooling magnetic field to form a cooling region A, thereby cooling and capturing the atomic clusters.

[0069] It should be noted that the cooling stage can be a stage that cools and captures atomic groups before the selection stage.

[0070] The seventh driving current can be the driving current applied to the magneto-optical trap coil 2 during the cooling stage. In this embodiment, the value of the seventh driving current ranges from 1A to 10A.

[0071] The cooling magnetic field can be the gradient magnetic field distribution generated after the seventh driving current is applied to the magneto-optical trap coil 2, which, together with the cooling light, forms a magneto-optical trap to cool the atomic group to the μK level and trap it at the center of the cooling region A.

[0072] Cooling region A can be the region where the cooling magnetic field and cooling light work together. It is located in the upper part of vacuum cavity 1. The atomic clusters are cooled in this region and form cold atomic clusters.

[0073] In its implementation, the device performs a cooling phase before the atomic cluster enters the selection phase. A seventh driving current is applied to the magneto-optical trap coil 2, which generates a cooling magnetic field, forming a cooling region A in the upper part of the vacuum cavity 1. Simultaneously, the device activates a cooling light system, generating three pairs of antisymmetrically propagating cooling lights that irradiate the cooling region A from three mutually orthogonal directions. The cooling magnetic field and cooling light work together, causing the atomic cluster to decelerate under the radiation pressure of the cooling light and simultaneously experience a restoring force in the gradient magnetic field, confining it to the center of the cooling region A. After a set cooling period, the temperature of the atomic cluster decreases to the micro-Kelvin level, and the atomic density reaches the experimental requirements. Once the cooling phase is complete, the magneto-optical trap coil 2 is de-energized and shut down, releasing the atomic cluster into the subsequent selection and interference phases. The magneto-optical trap coil 2 no longer participates in the magnetic field effects of any subsequent phases.

[0074] For example, the device applies a seventh driving current of 5A to the magneto-optical trap coil 2, which generates a gradient magnetic field in the cooling region A. The device then activates the cooling optical system, which emits three pairs of antisymmetrically propagating cooling lights to cool the rubidium atom cluster to 10μK in the cooling region A. After a 100ms cooling process, the device shuts down the cooling optical system and stops applying the seventh driving current to the magneto-optical trap coil 2. Under the influence of gravity, the atom cluster is released from the cooling region A along the axial direction of the vacuum cavity 1, entering the selection phase.

[0075] Based on the first and second embodiments of this application, a third embodiment of this application is proposed. In this third embodiment, content that is the same as or similar to the first and second embodiments described above can be referred to the above description, and will not be repeated hereafter. Based on this, please refer to... Figure 3 And 7, Figure 7 This is a flowchart illustrating the third embodiment of the gravity measurement method of this application.

[0076] In this embodiment, after the step of providing a bias-stabilized quantization axis for the atomic group in the selected state, the method further includes: Step S30: During the detection phase, stop applying the first driving current to the upper-selection coil 31 and stop applying the second driving current to the lower-selection coil 32, and maintain or disconnect the third driving current of the bias magnetic field coil 4 according to the preset detection mode; Step S31: Obtain the interference fringe information of the atomic group during the detection phase, and obtain the gravity measurement result based on the interference fringe information.

[0077] It should be noted that the detection phase can be the phase following the interference phase, in which fluorescence detection is performed on the atomic groups that have completed the interference.

[0078] The preset detection mode can be a control parameter pre-stored inside the device to indicate whether the bias magnetic field coil 4 is kept energized or de-energized during the detection phase. Different detection modes correspond to different Raman light configurations and fluorescence acquisition methods.

[0079] Interference fringe information can be obtained by collecting fluorescence signal data after irradiating atomic groups with Raman light. This data reflects the population distribution of atomic groups at different energy levels, from which the interference phase related to gravitational acceleration can be extracted.

[0080] In its implementation, after the atomic cluster completes interference in the extended bias magnetic field region, it continues to move downwards along the axis of vacuum cavity 1 under the influence of gravity, entering the detection phase. Once the device detects the atomic cluster entering the detection phase, it stops applying the first driving current to the upper selection coil 31 and simultaneously stops applying the second driving current to the lower selection coil 32. The upper and lower selection coils 31 and 32 are de-energized, and the first selection magnetic field disappears. The device determines whether to maintain the third driving current of the bias magnetic field coil 4 according to the preset detection mode. If the preset detection mode is the energized mode, the device continues to maintain the third driving current of the bias magnetic field coil 4. During the detection phase, the bias magnetic field maintains the quantization axis of the atomic cluster, ensuring that the polarization direction of the Raman light maintains a fixed angular relationship with the quantization axis, thus ensuring stable acquisition of the fluorescence signal. If the preset detection mode is the de-energized mode, the device disconnects the third driving current of the bias magnetic field coil 4, allowing the atomic cluster to be detected in a zero magnetic field environment. The device emits Raman light to the atomic cluster through the Raman light system. The atomic cluster is stimulated to emit fluorescence, and the device acquires the fluorescence signal through a photodetector to obtain the interference fringe information of the atomic cluster. The equipment extracts the interference phase from the interference fringe information, calculates the gravitational acceleration value based on the conversion relationship between the interference phase and gravitational acceleration, and obtains the gravity measurement result.

[0081] For example, after the atomic cluster completes interference and enters the detection phase, the device stops applying the first driving current of 0.40A to the upward selection coil 31 and the second driving current of 0.08A to the downward selection coil 32, and maintains the third driving current of 0.10A in the bias magnetic field coil 4 according to the preset detection mode. The device emits a beam of Raman light that resonates with the transition of rubidium atoms towards the atomic cluster. The atomic cluster is excited and emits fluorescence. The device collects the fluorescence signal through a photodetector, obtains the interference fringe information of the atomic cluster, and calculates the gravitational acceleration value based on the interference fringe information. If the preset detection mode is the power-off mode, the device disconnects the third driving current of the bias magnetic field coil 4 when the atomic cluster enters the detection phase, and completes fluorescence detection in a zero magnetic field environment.

[0082] Furthermore, in this embodiment, after the step of acquiring the interference fringe information of the atomic group during the detection phase and obtaining the gravity measurement result based on the interference fringe information, the method further includes: Step S311: Obtain the free evolution time of the atomic group during the interference process.

[0083] Step S312: Based on the free evolution time and the magnetic field distribution data of the atomic cluster in the extended bias magnetic field region, obtain the phase shift introduced by the second-order Zeeman effect of the atomic cluster during the interference stage; wherein, the extended bias magnetic field region includes the bias magnetic field region and the overlapping region E.

[0084] Step S313: Correct the gravity measurement result based on the phase shift.

[0085] It should be noted that the free evolution time can be the time taken for the atomic cluster to go from completing the selected state to completing the interference process. This time is determined by the falling distance of the atomic cluster under the action of gravity. In this embodiment, the free evolution time ranges from 80ms to 90ms.

[0086] Magnetic field distribution data can be information on the distribution of magnetic induction intensity with spatial location within the extended bias magnetic field region obtained through simulation or measurement, reflecting the actual spatial variation of the magnetic field within the extended bias magnetic field region.

[0087] The second-order Zeeman effect is a physical phenomenon in which atomic energy levels split twice under the influence of an external magnetic field. The resulting energy level shift is proportional to the square of the magnetic induction intensity.

[0088] Phase shift can be the phase difference accumulated by atoms along different paths due to magnetic field inhomogeneity. This phase difference is superimposed on the phase caused by gravity. If it is not corrected, it will affect the accuracy of the final gravity measurement result.

[0089] The extended bias magnetic field region can include the bias magnetic field region and the overlapping region E, which together form a uniform magnetic field coverage area when connected along the axial direction.

[0090] In its implementation, the device detects the atomic cluster and obtains gravity measurement results, then further corrects these results. The device acquires the free evolution time of the atomic cluster during the interference process; in this embodiment, the free evolution time is 85 ms. The device acquires magnetic field distribution data of the atomic cluster within the extended bias magnetic field region; this data can be obtained in advance through simulation or measurement and stored internally. Based on the free evolution time and magnetic field distribution data, the device calculates the phase shift introduced by the second-order Zeeman effect during the interference phase. This phase shift is calculated based on the physical principle of the second-order Zeeman effect: magnetic field inhomogeneity causes atoms to experience different magnetic induction intensities at different spatial locations, and the energy level shift caused by the second-order Zeeman effect is proportional to the square of the magnetic induction intensity. The energy level shift accumulated when atoms move along two different paths differs, generating an additional phase difference when the beam converges. During calculation, the device substitutes the magnetic induction intensity values ​​at each point along the atom's fall path into the phase expression of the second-order Zeeman effect and integrates along the atom's movement path within the extended bias magnetic field region to obtain the phase shift introduced by the magnetic field inhomogeneity. The equipment corrects the previously obtained gravity measurement results based on the calculated phase shift. The phase shift is subtracted from the total interference phase to eliminate the systematic error introduced by magnetic field inhomogeneity, resulting in a corrected gravity measurement result. Within the extended bias magnetic field region, the systematic error in gravity measurement introduced by the second-order Zeeman effect is less than 1 μGal, a value far smaller than the typical measurement uncertainty target of 10 μGal for portable atomic gravimeters.

[0091] For example, the device obtains a free evolution time of 85 ms for the atomic cluster during the interference process. The device reads pre-stored magnetic field distribution data within the extended bias magnetic field region. Based on the free evolution time and magnetic field distribution data, it calculates the phase shift using the second-order Zeeman effect phase calculation method, obtaining a gravity deviation of 0.39 μGal. The device subtracts 0.39 μGal from the previously obtained gravity measurement result to obtain the corrected gravity measurement result, eliminating the systematic error caused by magnetic field inhomogeneity. This correction is far less than the typical measurement uncertainty target of 10 μGal for a portable atomic gravimeter, indicating that the magnetic field design scheme of this approach does not introduce significant systematic errors while effectively reducing the system volume.

[0092] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the gravity measurement method of this application. Any simple modifications based on this technical concept are within the protection scope of this application.

[0093] This application also provides a gravity measuring device, please refer to... Figure 8The device includes: During the interference phase, the current control module 10 applies a first driving current to the upper selection coil and a second driving current to the lower selection coil. A first preset ratio exists between the first driving current and the second driving current, so that the upper selection coil and the lower selection coil jointly generate a first selection magnetic field to form a first selection region. A third driving current is applied to the bias magnetic field coil to generate a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction for the atomic clusters in the interference. Wherein, the first selected state region overlaps with at least a portion of the bias magnetic field region to form an overlapping region. The overlapping region extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

[0094] The gravity measuring device provided in this application, employing the gravity measuring method described in the above embodiments, can solve the technical problem of increasing the atomic movement distance during the interference phase without changing the device volume. Compared with the prior art, the beneficial effects of the gravity measuring device provided in this application are the same as those of the gravity measuring method provided in the above embodiments, and other technical features in the gravity measuring device are the same as those disclosed in the methods of the above embodiments, and will not be repeated here.

[0095] This application provides an atomic gravimeter, which includes: a magneto-optical trap coil, a state selection coil, and a bias magnetic field coil arranged along the axial direction of a vacuum cavity; a cooling magnetic field generated by the magneto-optical trap coil acts on a cooling region in the vacuum cavity; a state selection magnetic field generated by the state selection coil and an interference magnetic field generated by the bias coil are superimposed on an overlapping region in the vacuum cavity; and the cooling region is adjacent to the overlapping region. The atomic gravimeter further includes: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the gravity measurement method in Embodiment 1 above.

[0096] The following is for reference. Figure 9The diagram illustrates a structural schematic of an atomic gravimeter suitable for implementing embodiments of this application. The atomic gravimeter in the embodiments of this application may include, but is not limited to, mobile terminals such as mobile phones, laptops, digital broadcast receivers, PDAs (Personal Digital Assistants), PADs (Portable Application Descriptions), PMPs (Portable Media Players), in-vehicle terminals (e.g., in-vehicle navigation terminals), and fixed terminals such as digital TVs and desktop computers. Figure 5 The atomic gravimeter shown is merely an example and should not be construed as limiting the functionality and scope of the embodiments of this application.

[0097] like Figure 5 As shown, the atomic gravimeter may include a processing device 1001 (e.g., a central processing unit, a graphics processing unit, etc.), which can perform various appropriate actions and processes according to a program stored in a read-only memory (ROM) 1002 or a program loaded from a storage device 1003 into a random access memory (RAM) 1004. The RAM 1004 also stores various programs and data required for the operation of the atomic gravimeter. The processing device 1001, ROM 1002, and RAM 1004 are interconnected via a bus 1005. An input / output (I / O) interface 1006 is also connected to the bus. Typically, the following systems can be connected to the I / O interface 1006: input devices 1007 including, for example, a touchscreen, touchpad, keyboard, mouse, image sensor, microphone, accelerometer, gyroscope, etc.; output devices 1008 including, for example, a liquid crystal display (LCD), speaker, vibrator, etc.; storage devices 1003 including, for example, magnetic tape, hard disk, etc.; and communication devices 1009. Communication device 1009 allows the atomic gravimeter to communicate wirelessly or wiredly with other devices to exchange data. Although atomic gravimeters with various systems are shown in the figures, it should be understood that implementation or possession of all the systems shown is not required. More or fewer systems may be implemented alternatively.

[0098] Furthermore, in this embodiment, as Figure 3As shown, the atomic gravimeter further includes an inner magnetic shield 5 and an outer magnetic shield 6. The inner magnetic shield 5 is disposed outside the bias magnetic field coil 4, and the outer magnetic shield 6 is disposed outside the vacuum cavity 1. Before the step of simultaneously applying corresponding driving currents to the upper selection coil 31, the lower selection coil 32, and the bias magnetic field coil 4 to make at least a portion of the selection magnetic field and the bias magnetic field overlap to form an overlapping region, the method further includes: Step S14: The edge magnetic field of the bias magnetic field coil 4 is constrained by the inner magnetic shield 5 to increase the uniform magnetic field range of the bias magnetic field coil 4.

[0099] Step S15: Attenuate the ambient magnetic field outside the vacuum cavity 1 by means of the outer magnetic shield 6.

[0100] It should be noted that the inner magnetic shield 5 can be a cylindrical shielding structure made of a high magnetic permeability material, which is installed close to the outside of the bias magnetic field coil 4.

[0101] The outer magnetic shield 6 can be a shielding structure made of a high magnetic permeability material, surrounding the outside of the entire vacuum cavity 1.

[0102] The edge magnetic field can be the distribution of magnetic field lines that spread outward from the two ends of the bias magnetic field coil 4. This part of the magnetic field deviates from the uniform distribution and will compress the effective axial range of the uniform magnetic field.

[0103] The ambient magnetic field can be the Earth's magnetic field outside the vacuum cavity 1, or stray magnetic fields generated by surrounding electronic devices and power lines. If these magnetic fields enter the vacuum cavity 1, they will interfere with the quantization axis direction of atoms, causing deviations in the measurement results.

[0104] In its implementation, the atomic gravimeter is sequentially mounted along the axial direction of vacuum cavity 1 with a magneto-optical trap coil 2, a selection coil 3, and a bias magnetic field coil 4. An inner magnetic shield 5 is mounted tightly against the outside of the bias magnetic field coil 4. Before the device simultaneously applies driving current to the upward selection coil 31, the downward selection coil 32, and the bias magnetic field coil 4, the inner magnetic shield 5 and the outer magnetic shield 6 are already in operation. The magnetic field lines generated after the bias magnetic field coil 4 is energized form a closed loop through the inner magnetic shield 5 material. The outward-spreading edge magnetic field at both ends of the coil is confined back into the magnetic shield material, reducing the diffusion range of the edge magnetic field. This results in a more gradual gradient in magnetic induction intensity at both ends of the bias magnetic field coil 4, extending the axial range of the uniform magnetic field outward from the range achievable solely by the coil itself. The outer magnetic shield 6 surrounds the entire vacuum cavity 1. The ambient magnetic field outside the vacuum cavity 1 is absorbed and shunted by the high permeability material when passing through the wall of the outer magnetic shield 6, significantly attenuating the magnetic field strength entering the vacuum cavity 1. The influence of ambient magnetic field fluctuations on atomic motion is effectively suppressed. The inner magnetic shield 5 and the outer magnetic shield 6 function before the atomic clusters enter the overlapping region, covering the entire process from the cooling stage to the interference stage.

[0105] In traditional technologies, the reduced number of magnetic shielding layers and increased proportion of end cap opening area in a compact structure lead to decreased magnetic field uniformity, making it difficult to effectively compensate for residual magnetism and magnetic field gradients. External environmental interference is also more likely to affect measurement results. In this embodiment, the inner magnetic shield 5 is set close to the outside of the bias magnetic field coil 4, optimizing the magnetic field non-uniformity at the coil edge and increasing the uniform magnetic field range from approximately 190 mm to approximately 240 mm. The outer magnetic shield 6 surrounds the entire vacuum cavity 1, effectively attenuating the interference of external environmental magnetic fields on the interior of the vacuum cavity 1 and improving environmental adaptability in portable application scenarios.

[0106] For example, when the bias magnetic field coil 4 is energized, it generates a bias magnetic field along its axis. The inner magnetic shield 5 constrains the edge magnetic field at the end of the bias magnetic field coil 4, causing the magnetic field lines at the end of the coil to contract back into the magnetic shielding material. The axial range of the uniform magnetic field expands from approximately 190 mm without shielding to 240 mm. The outer magnetic shield 6 surrounds the entire vacuum cavity 1. The Earth's magnetic field and stray magnetic fields in the environment are attenuated to less than one-thousandth of their original strength when passing through the outer magnetic shield 6. Atoms moving within the vacuum cavity 1 are almost unaffected by external magnetic fields.

[0107] Specifically, according to the embodiments disclosed in this application, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments disclosed in this application include a computer program product comprising a computer program carried on a computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device, or installed from storage device 1003, or installed from ROM 1002. When the computer program is executed by processing device 1001, it performs the functions defined in the methods of the embodiments disclosed in this application.

[0108] The atomic gravimeter provided in this application, employing the gravity measurement method described in the above embodiments, can solve the technical problem of increasing the atomic movement distance during the interference phase without changing the device volume. Compared with the prior art, the beneficial effects of the atomic gravimeter provided in this application are the same as those of the gravity measurement method provided in the above embodiments, and other technical features of this atomic gravimeter are the same as those disclosed in the previous embodiment method, and will not be repeated here.

[0109] It should be understood that the various parts disclosed in this application can be implemented using hardware, software, firmware, or a combination thereof. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0110] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0111] The above description is only a part of the embodiments of this application and does not limit the patent scope of this application. All equivalent structural transformations made under the technical concept of this application and using the contents of the specification and drawings of this application, or direct / indirect applications in other related technical fields, are included in the patent protection scope of this application.

Claims

1. A gravity measurement method, characterized in that, The method is applied to an atomic gravimeter, which has a magneto-optical trap coil, a state selection coil, and a bias magnetic field coil arranged sequentially along the axial direction of the vacuum cavity. The magneto-optical trap coil is used to cool the atomic clusters. The state selection coil includes an upper state selection coil and a lower state selection coil, which are used to generate a state selection magnetic field to form a state selection region. The state selection region is used to select the atomic clusters. The bias magnetic field coil is used to generate a uniform bias magnetic field to form a bias magnetic field region. The state-selected atomic clusters interfere with each other in the bias magnetic field region. The interfering atomic clusters enter the detection region for detection, and gravity measurement results are obtained. The method includes: During the interference phase, a first driving current is applied to the upper selected state coil, and a second driving current is applied to the lower selected state coil. There is a first preset ratio between the first driving current and the second driving current, so that the upper selected state coil and the lower selected state coil jointly generate a first selected state magnetic field to form a first selected state region. A third driving current is applied to the bias magnetic field coil, so that the bias magnetic field coil generates a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction of the atomic clusters in the interference. Wherein, the first selected state region overlaps with at least a portion of the bias magnetic field region to form an overlapping region. The overlapping region extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

2. The method as described in claim 1, characterized in that, The steps prior to the interference phase also include: During the state selection phase, a fourth driving current is applied to the upper state selection coil and a fifth driving current is applied to the lower state selection coil, so that the upper state selection coil and the lower state selection coil jointly generate a second state selection magnetic field to form a second state selection region.

3. The method as described in claim 2, characterized in that, During the state selection phase, a sixth driving current is applied to the bias magnetic field coil to generate a bias magnetic field, providing a biased stable quantization axis for the atomic group in the state selection phase.

4. The method as described in claim 2 or claim 3, characterized in that, There is a second preset ratio between the fourth driving current and the fifth driving current.

5. The method as described in claim 4, characterized in that, The steps prior to the state selection phase also include: During the cooling phase, a seventh driving current is applied to the magneto-optical trap coil to generate a cooling magnetic field to form a cooling region, thereby cooling and trapping the atomic clusters.

6. The method as described in claim 5, characterized in that, Following the step of providing a bias-stabilized quantization axis to the atomic group in the selected state, the method further includes: During the detection phase, the first driving current applied to the upper-selection coil and the second driving current applied to the lower-selection coil are stopped, and the third driving current of the bias magnetic field coil is maintained or disconnected according to the preset detection mode; The interference fringe information of the atomic group during the detection phase is obtained, and the gravity measurement result is obtained based on the interference fringe information.

7. The method as described in claim 6, characterized in that, After the steps of acquiring the interference fringe information of the atomic group during the detection phase and obtaining the gravity measurement result based on the interference fringe information, the method further includes: Obtain the free evolution time of the atomic group during the interference process; Based on the free evolution time and the magnetic field distribution data of the atomic cluster in the extended bias magnetic field region, the phase shift introduced by the second-order Zeeman effect in the interference stage of the atomic cluster is obtained; wherein, the extended bias magnetic field region includes the bias magnetic field region and the overlapping region; The gravity measurement results are corrected based on the phase shift.

8. A gravity measuring device, characterized in that, The device includes: In the interference phase, the current control module applies a first driving current to the upper selection coil and a second driving current to the lower selection coil. A first preset ratio exists between the first driving current and the second driving current, so that the upper selection coil and the lower selection coil jointly generate a first selection magnetic field to form a first selection region. A third driving current is applied to the bias magnetic field coil to generate a bias magnetic field to form a bias magnetic field region, thereby maintaining the quantization axis direction for the atomic clusters in the interference. Wherein, the first selected state region overlaps with at least a portion of the bias magnetic field region to form an overlapping region. The overlapping region extends axially uniformly as the bias magnetic field region to extend the bias magnetic field region. The selected atomic clusters complete interference in the extended bias magnetic field region.

9. An atomic gravimeter, characterized in that, The atomic gravimeter includes: a magneto-optical trap coil, a state selection coil, and a bias magnetic field coil arranged sequentially along the axial direction of the vacuum cavity; the magneto-optical trap coil is used to cool the atomic clusters; the state selection coil includes an upper state selection coil and a lower state selection coil, used to generate a state selection magnetic field to form a state selection region, the state selection region being used to select the state of the atomic clusters; the bias magnetic field coil is used to generate a uniform bias magnetic field to form a bias magnetic field region, the state-selected atomic clusters interfering in the bias magnetic field region; the interfering atomic clusters then enter the detection region for detection, obtaining gravity measurement results; The atomic gravimeter further includes: a memory, a processor, and a computer program stored in the memory and executable on the processor, the computer program being configured to implement the steps of the gravity measurement method as described in any one of claims 1 to 7.

10. The atomic gravimeter as described in claim 9, characterized in that, The atomic gravimeter further includes an inner magnetic shield and an outer magnetic shield. The inner magnetic shield is disposed outside the bias magnetic field coil, and the outer magnetic shield is disposed outside the vacuum cavity. The inner magnetic shield constrains the edge magnetic field of the bias magnetic field coil to increase the uniform magnetic field range of the bias magnetic field coil. The outer magnetic shield attenuates the ambient magnetic field outside the vacuum cavity.

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