Large-momentum transfer two-component atom interferometer based on four-wave double diffraction raman

Abstract

This invention discloses a two-component atomic interferometer for large momentum transfer based on four-wave dual-diffraction Raman spectroscopy. It includes a vacuum system, within which cold atomic clusters comprise two components. First, second, and third Raman lasers incident on the vacuum system constitute the Raman light of the first component, while first, second, and fourth Raman lasers constitute the Raman light of the second component. Frequency variations in the third and fourth Raman lasers compensate for the Doppler frequency shift caused by the difference in recoil velocity during the large momentum transfer of the two atomic components. This invention utilizes the insensitivity of the two-component atomic interferometer to the third frequency of the Raman laser. By independently adjusting the frequency of the non-shared lasers of the two-component atomic interferometer, it achieves large momentum transfer in the two-component atomic interferometer while ensuring common-mode suppression of phase noise in the two-component atoms, and without limiting the number of recoil photons by the Doppler frequency shift difference, thus improving the accuracy of differential measurements.

Description

Technical Field

[0001] This invention relates to the fields of cold atom physics and quantum precision measurement, specifically to a large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman. Background Technology

[0002] With the development of cold atom manipulation and atomic interferometry techniques, atomic interferometers have become powerful tools for fundamental physics (such as equivalence principle testing) and precision inertial sensing (such as gravity, gravity gradient measurement, and inertial navigation). Improving the measurement accuracy of atomic interferometers by increasing the magnitude of momentum transferred during the interaction between light and atoms (Large Momentum Transfer, LMT) is an effective method (Peter Asenbaum et al., Physical Review Letters, Vol. 125, No. 191101, 2020). Significant progress has been made in large momentum transfer experiments using single-component atomic interferometers (using the same type of atom), with the maximum transfer momentum reaching 408. ( To reduce Planck's constant, (representing the wave vector), while for two-component atomic interferometers (using two different types of atoms) used in experiments such as equivalence principle testing and gravity gradient measurement, the maximum reported transfer moment is only 12. How to improve the measurement accuracy of a two-component atomic interferometer by increasing photon momentum transfer is a current research hotspot in atomic interferometers.

[0003] Current research mainly focuses on extended single-diffraction Raman pulse sequences, Bragg diffraction, and Bloch oscillation schemes, as well as their combined schemes. These techniques, applied to two-component atomic interferometers to achieve greater momentum transfer, all have limitations, primarily in the following aspects:

[0004] In the extended single-diffraction Raman pulse sequence scheme, non-uniform light intensity leads to non-uniform distribution of Rabi frequency and decoherence caused by spontaneous emission, which reduces the contrast and signal-to-noise ratio of interference fringes. Furthermore, in the interference loop, the different internal states of atoms can be significantly affected by electromagnetic field noise from the environment. When applied to two-component atomic interferometers, it is constrained by compatibility issues caused by differences in atomic physical properties.

[0005] In Bragg diffraction schemes, the required laser power increases almost exponentially with the Bragg diffraction order. A typical 10th-order Bragg diffraction requires more than 3 W of optical power, and the fringe contrast is severely attenuated. The biggest challenge is that, for two-component atomic interferometers, due to the mass differences between the different atoms, it is difficult to simultaneously achieve large momentum transfer of two-component atoms through high-order Bragg diffraction.

[0006] The Bloch oscillation scheme enables single-component atomic interferometers to achieve high photon transfer momentum, but for two-component atomic interferometers, the mass difference between different atoms means that the same set of laser pulses cannot simultaneously achieve high momentum transfer for both types of atoms. Furthermore, the scheme is severely limited by lattice beam wavefront distortion and laser phase noise.

[0007] In summary, while existing large momentum transfer schemes have achieved success in single-component atomic interferometers, their application in two-component atomic interferometers is generally limited by compatibility issues caused by differences in atomic physical properties. Specifically, when the two components of atoms do not share a laser, this scheme allows both interferometers to achieve large momentum transfer, but the phase noise of different lasers will severely impact the differential measurement accuracy. For non-isotopic atoms, the common-mode effect is even worse due to the greater difference in wave vectors. When the two components of atoms share a laser, this scheme can effectively suppress laser phase noise, but due to the mass difference between the two components, it becomes difficult to resonate with both types of atoms simultaneously with the increase in photon momentum transfer using the same laser pulse. For differential measurements in two-component atomic interferometers, sharing a laser better leverages its common-mode characteristics. Therefore, how to effectively address the limited number of recoil photons during large momentum transfer in two-component atomic interferometers while simultaneously suppressing noise and common-mode effects is the core issue of current large momentum transfer technology in two-component atomic interferometers. Summary of the Invention

[0008] To address the issue that existing two-component atomic interferometers suffer from Doppler frequency shift differences due to varying recoil magnitudes caused by the mass difference between the two types of atoms during large momentum transfer, which limits the photon recoil number in large momentum transfer and thus affects measurement sensitivity, this invention proposes a two-component atomic interferometer for large momentum transfer based on four-wave dual-diffraction Raman spectroscopy.

[0009] The above-mentioned objective of this invention is achieved through the following technical solution:

[0010] A large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman spectroscopy, including a vacuum system,

[0011] The upper part of the vacuum system is fitted with a magnetic shielding system, which has an opening at the top. The lower region inside the vacuum system is the ejection zone and the detection zone. The detection zone is located above the ejection zone, and the initial position of the cold atom cluster is located in the ejection zone. The cold atom cluster consists of two components. A fluorescence collection system and an imaging CCD are sequentially arranged outside the vacuum system and at the position corresponding to the detection zone. A cooling laser is arranged on the outside of the vacuum system at the position corresponding to the ejection zone. The first branch beam of the third Raman laser, the first branch beam of the fourth Raman laser, the detection laser, and the first Raman laser are incident into the vacuum system from the top. The second branch beam of the third Raman laser, the second branch beam of the fourth Raman laser, and the second Raman laser are reflected by a compensation mirror arranged below the bottom of the vacuum system and then incident into the vacuum system from the bottom and propagate towards the top of the vacuum system.

[0012] The first Raman laser, the second Raman laser, and the third Raman laser constitute the first component of Raman light, and the first Raman laser, the second Raman laser, and the fourth Raman laser constitute the second component of Raman light.

[0013] The frequency variations of the third and fourth Raman lasers are used to compensate for the Doppler shift caused by the difference in recoil velocity during the high momentum transfer of atoms in the two components.

[0014] The gravity difference measurement method includes the following steps:

[0015] Step 1: Construct a large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman, and set the initial frequencies and light intensities of the first, second, third, and fourth Raman lasers;

[0016] Step 2: Cooling and emitting cold atomic clusters using a cooling laser;

[0017] Step 3: Implement an extended Mach-Zehnder interferometric sequence using the first, second, third, and fourth Raman lasers. The extended Mach-Zehnder interferometric sequence includes, in sequence:

[0018] First π / Pulse, first π pulse group, first free evolution duration T, second π pulse group π pulse, third π pulse group, second free evolution duration T, fourth π pulse group, second π / pulse;

[0019] The first π pulse group, the second π pulse group, the third π pulse group, and the fourth π pulse group all include A series of π pulses;

[0020] Each pulse consists of all Raman lasers acting simultaneously; the pulse includes π / Pulse, π pulse and π pulse, all Raman lasers including the first Raman laser, the second Raman laser, the two split beams in the third Raman laser and the two split beams in the fourth Raman laser;

[0021] Step 4: Excite the cold atom clusters sequentially with quenching light and probe laser, and capture the shear interference fringe images of the first component and the second component using an imaging CCD.

[0022] Step 5: Extract the corresponding interferometer fringes from the sheared interference fringe images of each component using the principal component analysis method, extract the corresponding interference phase from the interferometer fringes of each component, and obtain the differential phase from the difference between the interference phases of the two components.

[0023] As mentioned above, the cold atom group comprises two components, respectively Atoms and The initial frequencies of the first, second, third, and fourth Raman lasers satisfy the following condition:

[0024] ,

[0025] ,

[0026] ,

[0027] in, The initial frequencies of the first Raman laser are respectively The initial frequency of the fourth Raman laser;

[0028] and They are In atomic energy levels lines The energy level difference between the two ground states of the energy level and In atomic energy levels lines The energy level difference between the two ground states of an energy level;

[0029] This is a preset frequency difference limit.

[0030] As described above, the initial frequencies of the first, second, third, and fourth Raman lasers satisfy the following condition:

[0031] ,

[0032] ,

[0033] ,

[0034] in, As the frequency reference zero, equal to Atom The transition frequency of the line |F=3>-|F'=4>.

[0035] As described above, the light intensities of the first, second, third, and fourth Raman lasers satisfy the following condition:

[0036] ,

[0037] in, The light intensity of the first Raman laser The intensity of the fourth Raman laser.

[0038] As mentioned above, the two split beams in the third Raman laser, the two split beams in the fourth Raman laser, the first Raman laser, and the second Raman laser are all chirped. The chirp rate of the fourth Raman laser and the first Raman laser is... The chirp rates of the second and third Raman lasers are... The numerical value of chirp rate , It is an effective wave vector. It is gravitational acceleration.

[0039] As mentioned above, the first π / pulse, π pulse, second π / The frequency of the third Raman laser corresponding to the pulse is the initial frequency of the third Raman laser. ;

[0040] First π / pulse, π pulse, second π / The frequency of the fourth Raman laser corresponding to the pulse is the initial frequency of the fourth Raman laser. ;

[0041] In the π pulse group with odd serial numbers, the first The frequencies of the third and fourth Raman lasers corresponding to the π pulses are as follows:

[0042] ,

[0043] ,

[0044] in,

[0045] The π pulse groups with odd numbers are the first π pulse group and the third π pulse group;

[0046] This indicates the π pulse group with odd numbers. The frequency of the third Raman laser in each π pulse;

[0047] This indicates the π pulse group with odd numbers. The frequency of the fourth Raman laser in the π pulses;

[0048] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser;

[0049] This indicates the π pulse group with odd numbers. The frequency change of the fourth Raman laser corresponding to each π pulse:

[0050] ,

[0051] ,

[0052] The sequence number of the π pulses in a π pulse group with an odd sequence number , This represents the total number of π pulses in a π pulse group. Indicates rounding up;

[0053] yes Atomic Doppler shift;

[0054] yes Atomic Doppler shift;

[0055] In the even-numbered π pulse group, the first... The frequencies of the third and fourth Raman lasers in the π pulses are as follows:

[0056] ,

[0057] ,

[0058] in,

[0059] The π pulse groups with even numbers are the second π pulse group and the fourth π pulse group;

[0060] This indicates the π pulse group with even numbers. The frequency of the third Raman laser in each π pulse;

[0061] This indicates the π pulse group with even numbers. The frequency of the fourth Raman laser in the π pulses;

[0062] This indicates the π pulse group with even numbers. Each π pulse corresponds to the frequency change of the third Raman laser;

[0063] This indicates the π pulse group with even numbers. The frequency change of the fourth Raman laser corresponding to each π pulse:

[0064] ,

[0065] ,

[0066] The sequence number of the π pulses in a π pulse group with an even sequence number ,

[0067] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser;

[0068] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the fourth Raman laser.

[0069] As described above, step 2 specifically includes the following steps:

[0070] Using cooled lasers and 3D magneto-optical traps (3D-MOTs) Atoms and Atoms are simultaneously cooled and loaded, and the cooling laser forms an atomic fountain with a (0,0,1) configuration; the loaded cold atom clusters are either allowed to fall freely or thrown vertically downwards, and then thrown vertically upwards.

[0071] Compared with the prior art, the present invention has the following beneficial effects:

[0072] Achieving simultaneous high momentum transfer in a dual-component system: By combining a four-wave dual-diffraction Raman beam configuration and extending the pulse sequence, the frequency of the third and fourth Raman lasers is adjusted using the four-wave dual-diffraction 4WDR scheme. This enables independent compensation for the recoil Doppler frequency shift during high momentum transfer in a dual-component system, allowing two different atoms to simultaneously achieve high momentum transfer far exceeding current levels.

[0073] Enhanced measurement sensitivity: The achieved large momentum transfer directly amplifies the phase response of the atomic interferometer to inertial effects. times, of which The total number of π pulses in a π pulse group (compared to π / - π-π / Compared to pulse sequences, this significantly improves measurement sensitivity, laying the foundation for higher-precision basic physical testing and inertial sensing applications.

[0074] This invention utilizes the insensitivity of a two-component atomic interferometer to the third frequency of Raman lasers. By independently adjusting the frequency of the non-shared laser in the two-component atomic interferometer, it compensates for the Doppler frequency shift difference caused by the large momentum transfer process between the two components of atoms. This solves the problem of limited photon back impulse quantity in traditional large momentum transfer schemes of two-component atomic interferometers due to the mass difference between the two types of atoms. Simultaneously, this invention maintains the common-mode suppression characteristics of the four-wave dual-diffraction scheme while conducting large momentum transfer experiments with the two-component atomic interferometer, improving the measurement sensitivity and accuracy of the two-component interferometer. This invention overcomes the technical bottleneck of traditional two-component atomic interferometer techniques being incompatible with the large momentum transfer of two types of atoms, laying the foundation for future fundamental research such as higher-precision equivalence principle verification and applications such as inertial measurement.

[0075] Maintaining common-mode noise suppression: The dual diffraction scheme and shared Raman optical path design ensure that intrinsic common-mode laser phase noise is suppressed. Through precise control, the differential wave vector effect that may be introduced during large momentum transfer is minimized, thereby effectively suppressing the influence of common-mode noise such as environmental vibrations on differential measurements, ensuring the stability and accuracy of the measurements. Attached Figure Description

[0076] Figure 1 This is a schematic diagram of the high momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman spectroscopy of the present invention.

[0077] Among them, 101-cold atom cluster, 102-vacuum system, 103-magnetic shielding system, 104-cooling laser, 105-probe laser, 106-first Raman laser, 107-second Raman laser, 108-third Raman laser, 109-fourth Raman laser, 110-fluorescence collection system, 111-imaging CCD, 112-compensating reflector;

[0078] Figure 2 A schematic diagram showing the frequency configuration of each Raman laser beam; F represents the total angular momentum quantum number of the ground state, and F' represents the total angular momentum quantum number of the excited state; The initial frequencies of the first Raman laser are respectively The initial frequency of the fourth Raman laser; The light intensity of the first Raman laser is respectively The light intensity of the fourth Raman laser;

[0079] Figure 3 To expand the spatiotemporal schematic diagram of a dual-diffraction Raman pulse sequence atomic interferometer; π / , π and π represent π / pulse, π pulse and π pulse; The total number of π pulses in a π pulse group; T is the duration of free evolution;

[0080] Figure 4 The phase shift of the fringes was extracted for EMCCD imaging and principal component analysis of the interferometer fringes; where (a) is a two-dimensional interferometric image acquired by the EMCCD camera, (b) is a one-dimensional interferometric image of the two components, and (c) is the two-component interferometric fringes;

[0081] Figure 5 This is a flowchart of the two-component high momentum transfer atom interferometer based on four-wave dual-diffraction Raman spectroscopy of the present invention. Detailed Implementation

[0082] To facilitate understanding and implementation of the present invention by those skilled in the art, the present invention will be further described in detail below with reference to embodiments. The embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0083] Example 1

[0084] A large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman spectroscopy, such as Figure 1 As shown, it includes cold atomic group 101 (cold atomic group 101 includes two component atomic groups; in this embodiment, the first component is...). Atoms, the second component is (atomic atoms), vacuum system 102, magnetic shielding system 103, cooling laser 104, detection laser 105, first Raman laser 106, second Raman laser 107, third Raman laser 108 and fourth Raman laser 109, fluorescence collection system 110, imaging CCD 111, angle with ground The compensation mirror 112 is placed therein, in which both the third Raman laser 108 and the fourth Raman laser 109 include two split beams. The specific structure is as follows:

[0085] The upper outer casing of the vacuum system 102 is equipped with a magnetic shielding system 103, with an opening at the top. The lower region inside the vacuum system 102 is the ejection zone and the detection zone. The initial position of the cold atom cluster 101 is located in the ejection zone, and the detection zone is located above the ejection zone. Outside the vacuum system 102, corresponding to the detection zone, a fluorescence collection system 110 and an imaging CCD 111 are sequentially arranged. On the outer side of the vacuum system 102, corresponding to the ejection zone, are three pairs of cooling lasers 104 (each pair is perpendicular to the other). Figure 1 Only two pairs of horizontally propagating cooling lasers 104 are shown in the diagram. In another pair of cooling lasers 104, two beams propagate relative to each other along the extension direction of the vacuum system 102. The first branch beam of the third Raman laser 108, the first branch beam of the fourth Raman laser 109, the probe laser 105, and the first Raman laser 106 are incident from the top of the vacuum system 102 into the vacuum system 102. A compensation reflector 112 is provided below the bottom of the vacuum system 102. The second branch beam of the third Raman laser 108, the second branch beam of the fourth Raman laser 109, and the second Raman laser 107 are reflected by the compensation reflector 112 and then incident from the bottom of the vacuum system 102 into the vacuum system 102, and then propagate upward along a direction parallel to the central axis of the vacuum system 102. By rotating the compensating reflector 112, the second branch beam of the third Raman laser 108, the second branch beam of the fourth Raman laser 109, and the second Raman laser 107 are aligned in the positive z-axis direction, i.e., from the bottom to the top of the vacuum system 102. Figure 1 As shown, the first branch beam in the third Raman laser 108 and the first branch beam in the fourth Raman laser 109, as well as the first Raman laser 106, point in the negative z-axis direction.

[0086] The imaging CCD 111 used in this embodiment is an EMCCD camera.

[0087] The first Raman laser 106, the second Raman laser 107, and the third Raman laser 108 constitute the first component (in this embodiment, ...). The Raman light of atoms, the first Raman laser 106, the second Raman laser 107 and the fourth Raman laser 109 constitute the second component (in this embodiment, the Raman light of atoms). Raman light of atoms.

[0088] This invention will Atoms and The first Raman laser 106 and the second Raman laser 107, which are shared by atoms, are used as chirped lasers to compensate for the Doppler frequency shift caused by gravity during the atomic motion process in the cold atom cluster 101. The frequencies of the third Raman laser 108 and the fourth Raman laser 109 are adjusted to compensate for the Doppler frequency shift caused by the difference in recoil velocity during the high momentum transfer process of the atoms of the two components. The specific process is described in Example 2.

[0089] Example 2

[0090] The gravity differential measurement method utilizes the large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman as described in Example 1. It uses the first Raman laser 106 and the second Raman laser 107 as chirped lasers to compensate for the Doppler frequency shift caused by gravity during atomic motion. The frequencies of the third Raman laser 108 and the fourth Raman laser 109 are adjusted to compensate for the Doppler frequency shift caused by the difference in recoil velocity during the large momentum transfer of the two types of atoms. The momentum of the transferred photons is gradually increased by adding Raman laser pulse sequences, thus realizing a large momentum transfer two-component atomic interferometer. Finally, high-precision gravity differential measurement is achieved through specific optical structures and operating methods. Figure 5 As shown, the specific steps are as follows:

[0091] Step 1: Construct a large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman, and set the initial frequency and intensity of the first Raman laser 106, the second Raman laser 107, the third Raman laser 108, and the fourth Raman laser 109.

[0092] Set the initial frequency:

[0093] The four-wave dual diffraction (4WDR) scheme is adopted according to Atoms and The energy level structure of the atom is represented by the first Raman laser 106, the second Raman laser 107, the third Raman laser 108, and the fourth Raman laser 109 (wave vectors are denoted as follows). The initial frequencies are denoted as follows: After frequency, intensity, and polarization control, the Raman laser is injected into the interference region of the vacuum system 102 through an optical fiber. The interference region is located above the detection region, and the relative frequency relationship of each Raman laser is as follows:

[0094] ,

[0095] ,

[0096] ,

[0097] in, These are the initial frequencies of the first Raman laser to the fourth Raman laser, respectively.

[0098] and They are In atomic energy levels lines The energy level difference between the two ground states of the energy level and In atomic energy levels lines The energy level difference between the two ground states of an energy level; , ;

[0099] A preset frequency difference limit value is used to limit the frequency difference. and near, and near, and near.

[0100] In this embodiment, the absolute frequencies of the six Raman laser beams are set as follows: Figure 2 As shown, specifically:

[0101] set up Atom The transition frequency of the line |F=3>-|F'=4> is the frequency reference zero. ,

[0102] ;

[0103] ;

[0104] ;

[0105] Set the light intensities of the first Raman laser 106, the second Raman laser 107, the third Raman laser 108, and the fourth Raman laser 109:

[0106] The intensity ratio of each Raman laser beam is as follows: , The light intensity of the first Raman laser The intensity of the fourth Raman laser.

[0107] Furthermore, to compensate for the Doppler frequency shift of the vertically projectile motion of the atoms, all six Raman laser beams (two branch beams in the third Raman laser 108, two branch beams in the fourth Raman laser 109, the first Raman laser 106, and the second Raman laser 107) are chirped. The chirp rate of the fourth Raman laser 109 (including the two branch beams in the fourth Raman laser 109) and the first Raman laser 106 is... The chirp rate of the second Raman laser 107 and the third Raman laser 108 (including the two split beams in the third Raman laser 108) is The numerical value of chirp rate , ,in It is an effective wave vector. It is gravitational acceleration. It is the average value of the initial wave vector, which is equal to the average value of the initial wave vectors of the first Raman laser 106 to the fourth Raman laser 109.

[0108] Step 2: Atom preparation and emission.

[0109] In step 2, the cold atom cluster 101 is cooled and emitted using a cooling laser 104. In this embodiment, the specific process is as follows:

[0110] Using cooled laser 104 and three-dimensional magneto-optical trap 3D-MOT to Atoms and Atoms were simultaneously cooled and loaded. Four cooling laser beams 104 were placed horizontally, while the other two beams propagated along the positive and negative z-axis directions, respectively, forming an atomic fountain with a (0,0,1) configuration. The experimental setup is shown in Figure 1. For the cooling lasers 104, the intensity balance of each beam was ensured by stabilizing the laser power, further suppressing fluctuations in the center position of the cold atom cluster 101. After loading... Atoms and The corresponding cold atom cluster 101 is subjected to free fall or vertical downward throwing, followed by vertical upward throwing. This prolongs the interaction time between the cold atom cluster 101 and the cooling laser 104 at the intersection center and allows for sufficient acceleration. Here, the cold atom cluster 101 initially moves a very short distance downward (without hitting the bottom of the vacuum system 102). The purpose is to ensure full contact with the cooling laser 104 and to perform secondary polarization gradient cooling (PGC) during the movement of the optical adhesive. This further reduces the temperature of the cold atom cluster 101 and increases the intensity of the falling atom signal.

[0111] Step 3: Two-component atomic interferometer large momentum transfer.

[0112] An extended Mach-Zehnder interference sequence was constructed by extending the double-diffraction high-momentum pulse sequence. This extended Mach-Zehnder interference sequence was implemented using a first Raman laser 106, a second Raman laser 107, a third Raman laser 108, and a fourth Raman laser 109. The extended Mach-Zehnder interference sequence includes, in sequence:

[0113] First π / Pulse, first π pulse group, first free evolution duration T, second π pulse group π pulse, third π pulse group, second free evolution duration T, fourth π pulse group, second π / pulse;

[0114] Among them, all π pulse groups (i.e., the first π pulse group, the second π pulse group, the third π pulse group, and the fourth π pulse group) include A series of consecutive π pulses; each pulse (i.e., π / Pulse, π pulse and The π pulses are all Raman lasers (i.e., including the two split beams in the third Raman laser 108, the two split beams in the fourth Raman laser 109, the first Raman laser 106, and the second Raman laser 107) acting simultaneously, but The atom resonates only with the first Raman laser 106, the second Raman laser 107, and the third Raman laser 108. (The atoms resonate only with the first Raman laser 106, the second Raman laser 107, and the fourth Raman laser 109), and both types of atoms are measured simultaneously. For positive integers, the total momentum transfer is .

[0115] First π / pulse, π pulse, second π / The frequency of the third Raman laser 108 corresponding to the pulse is the initial frequency of the third Raman laser. ;

[0116] First π / pulse, π pulse, second π / The frequency of the fourth Raman laser 109 corresponding to the pulse is the initial frequency of the fourth Raman laser. ;

[0117] In the π pulse groups with odd numbers (the π pulse groups with odd numbers are the first π pulse group and the third π pulse group), the first... The frequencies of the third Raman laser 108 and the fourth Raman laser 109 corresponding to the π pulses are as follows:

[0118] ,

[0119] ,

[0120] in,

[0121] This indicates the π pulse group with odd numbers. The frequency of the third Raman laser in each π pulse;

[0122] This indicates the π pulse group with odd numbers. The frequency of the fourth Raman laser in the π pulses;

[0123] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser;

[0124] This indicates the π pulse group with odd numbers. The frequency change of the fourth Raman laser corresponding to each π pulse:

[0125] ,

[0126] ,

[0127] The sequence number of the π pulses in a π pulse group with an odd sequence number , This represents the total number of π pulses in a π pulse group. Indicates rounding up;

[0128] yes Atomic Doppler shift, kilohertz;

[0129] yes Atomic Doppler shift, kilohertz;

[0130] In the even-numbered π pulse groups (the even-numbered π pulse groups are the second and fourth π pulse groups), the first... The frequencies of the third Raman laser 108 and the fourth Raman laser 109 in the π pulses are respectively:

[0131] ,

[0132] ,

[0133] in,

[0134] This indicates the π pulse group with even numbers. The frequency of the third Raman laser in each π pulse;

[0135] This indicates the π pulse group with even numbers. The frequency of the fourth Raman laser in the π pulses;

[0136] This indicates the π pulse group with even numbers. The frequency change of the third Raman laser corresponding to each π pulse:

[0137] This indicates the π pulse group with even numbers. The frequency change of the fourth Raman laser corresponding to each π pulse:

[0138] ,

[0139] ,

[0140] The sequence number of the π pulses in a π pulse group with an even sequence number ,

[0141] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser;

[0142] This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the fourth Raman laser.

[0143] This embodiment uses Taking the changes of the third Raman laser 108 in the atomic high momentum process as an example, the total number of π pulses in a π pulse group is 3. The atom has an initial momentum of Moving in the positive z-axis direction

[0144] Initial first π / After pulsed application, the cold atom cluster 101 is split into two beams, and the upper interference arm is activated. The momentum change of atomic absorption two-photon lasers (corresponding to the first Raman laser 106 and the third Raman laser 108) is ( Reduce Planck's constant, for (The initial motion of the atom corresponds to the wave vector of the de Broglie wave), upper interference arm The Doppler frequency shift corresponding to the atom is (in, Represents the speed of light. express (mass of atoms); lower interference arm The momentum change of atomic absorption two-photon lasers (second Raman laser 107 and third Raman laser 108) Lower interference arm Atom correspondence The atomic Doppler frequency shift change is Upper and lower interference arms Atomic momentum splitting ;

[0145] The frequency of the third Raman laser 108 corresponding to the first π pulse in the first π pulse group increases. (Right now , Due to the Doppler frequency shift, the upper interferometer arm The atom resonates only with the first Raman laser 106 and the third Raman laser 108. Atomic momentum becomes Similarly, the lower interference arm The atom resonates only with the second Raman laser 107 and the third Raman laser 108. Atomic momentum becomes upper and lower interference arms Atomic momentum splits into ;

[0146] The frequency of the third Raman laser 108 corresponding to the second π pulse in the first π pulse group increases. (Right now , Upper interference arm Atomic momentum becomes Lower interference arm Atomic momentum becomes upper and lower interference arms Atomic momentum splitting into ;

[0147] The frequency of the third Raman laser 108 corresponding to the third π pulse in the first π pulse group increases. (Right now , Upper interference arm Atomic momentum becomes Lower interference arm Atomic momentum becomes upper and lower interference arms Atomic momentum splits into Atomic interferometer High-momentum splitting, corresponding to Figure 3 The absolute value of the slope of the middle curve is the largest;

[0148] Atoms each time After pulse interaction, the internal states of the atom will flip ( atom The hyperfine level of the ground state has two states.

[0149] After a period of free evolution T

[0150] The frequencies of the individual π pulses in the second π pulse group (the frequencies of the third Raman laser 108 are, in order) are: , , Sequentially connect the upper and lower interference arms Atomic momentum splitting decreases to ;

[0151] The middle The π pulse is a four-photon process (at this time) The frequency of the third Raman laser 108 in the π pulse recovers to the initial frequency of the third Raman laser. ), with the upper and lower interference arms Atomic momentum splitting change Become However, the internal states of the atom do not change;

[0152] The frequencies of the individual π pulses in the third π pulse group (the frequencies of the third Raman laser 108 are, in order) are: , , ) The upper and lower interference arms The atomic momentum splitting changes sequentially to After a free evolution period T,

[0153] The frequencies of the individual π pulses in the fourth π pulse group (the third Raman laser 108) are as follows: , , ) The upper and lower interference arms Atomic momentum splitting changes sequentially - Thus, without introducing an additional phase shift, a second π / is finally applied. Pulse-upper and lower interferometer arms With atoms having the same momentum, atomic wave packets are re-bundled.

[0154] This embodiment is based on the four-wave dual diffraction (4WDR) scheme. Atom-pair fourth Raman laser 109, To compensate for the insensitivity of the third Raman laser 108, the frequencies of the third Raman laser 108 and the fourth Raman laser 109 are adjusted respectively to compensate for the difference in Raman light k-wave loss caused by the difference in atomic mass during the large momentum transfer process of the two-component atomic interferometer, so that the two interferometers can obtain large momentum transfer simultaneously and ensure the common mode nature of the synchronous two-component atomic interferometer.

[0155] Step 4: Atomic detection and signal extraction.

[0156] After the cold atom cluster 101 has been freely flying for a period of time, it is then excited sequentially with quenching light and probe laser 105, as follows: Figure 4 As shown in (a) and (b), the imaging CCD 111 captures the first component (i.e., ...) using EMCCD imaging. Shearing interference fringe image of atoms and the second component (i.e. The shearing interference fringe image of the two atoms is obtained, thus showing the two atoms in two output states (in this embodiment, i.e., atom The ground state and the line atom The atomic number distribution of the line in its ground state.

[0157] Step 5: Differential phase measurement and analysis.

[0158] Perform long-term measurements for tens of hours, such as Figure 4As shown in (c), the corresponding interferometer fringes are extracted from the shearing interference fringe images of each component using the principal component analysis method. The corresponding interference phases are extracted from the interferometer fringes of each component. The difference phase is obtained from the difference between the interference phases of the two components.

[0159] In this embodiment, from Extraction of atomic shearing interference fringe images Interferometer fringes of atoms and Extraction of atomic shearing interference fringe images Interferometer fringes of atoms; extracted Interferometer fringes of atoms and Interference fringes of atoms, extracted separately Atom interference phase and Atom interference phase ; Calculate the differential phase The differential phase It is insensitive to common-mode noise (such as laser phase noise and plateau vibration), but sensitive to atom-dependent effects (such as signal destruction by the equivalence principle and gravitational gradients). A series of differential phases are obtained from multiple measurements using Allan variance data processing. This yields the confidence interval for gravity differential measurement data. Due to the realization of large momentum transfer, the scaling factor increases and the sensitivity improves.

[0160] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A gravity difference measurement method, characterized in that, Includes the following steps: Step 1: Construct a large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman, and set the initial frequencies and light intensities of the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109); Step 2: Cool and emit cold atomic clusters (101) using a cooling laser (104); Step 3: Implement an extended Mach-Zehnder type interference sequence using the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109); Step 4: Excite the cold atom cluster (101) sequentially with quenching light and probe laser (105), and capture the shear interference fringe images of the first component and the second component with imaging CCD (111). Step 5: Extract the corresponding interferometer fringes from the sheared interference fringe images of each component using principal component analysis. Extract the corresponding interference phase from the interferometer fringes of each component. Obtain the differential phase from the difference between the interference phases of the two components. The large momentum transfer two-component atomic interferometer based on four-wave dual-diffraction Raman includes a vacuum system (102). A magnetic shielding system (103) is installed on the upper part of the vacuum system (102), with an opening at the top. The lower region inside the vacuum system (102) is a projection zone and a detection zone. The detection zone is located above the projection zone. The initial position of the cold atom cluster (101) is located in the projection zone. The cold atom cluster (101) consists of two components. A fluorescence collection system (110) and an imaging CCD are sequentially installed outside the vacuum system (102) at a position corresponding to the detection zone. (111); A cooling laser (104) is set on the outside of the vacuum system (102) at a position corresponding to the ejection area. The first branch beam of the third Raman laser (108), the first branch beam of the fourth Raman laser (109), the detection laser (105) and the first Raman laser (106) are incident into the vacuum system (102) from the top. The second branch beam of the third Raman laser (108), the second branch beam of the fourth Raman laser (109) and the second Raman laser (107) are reflected by the compensation reflector (112) set below the bottom of the vacuum system (102) and then incident into the vacuum system (102) from the bottom and propagate towards the top of the vacuum system (102). The first Raman laser (106), the second Raman laser (107), and the third Raman laser (108) constitute the first component of Raman light, and the first Raman laser (106), the second Raman laser (107), and the fourth Raman laser (109) constitute the second component of Raman light; The two split beams in the third Raman laser (108), the two split beams in the fourth Raman laser (109), the first Raman laser (106), and the second Raman laser (107) are all chirped. The chirp rate of the fourth Raman laser (109) and the first Raman laser (106) is... The chirp rates of the second Raman laser (107) and the third Raman laser (108) are... The numerical value of chirp rate , It is an effective wave vector. It is gravitational acceleration.

2. The gravity difference measurement method according to claim 1, characterized in that, The extended Mach-Zehnder type interferometry sequence includes, in sequence: First π / Pulse, first π pulse group, first free evolution duration T, second π pulse group π pulse, third π pulse group, second free evolution duration T, fourth π pulse group, second π / pulse; The first π pulse group, the second π pulse group, the third π pulse group, and the fourth π pulse group all include A series of π pulses; Each pulse consists of all Raman lasers acting simultaneously; the pulse includes π / Pulse, π pulse and π pulses, all Raman lasers including two split beams in the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109).

3. The gravity difference measurement method according to claim 2, characterized in that, The cold atom group (101) includes two components, respectively Atoms and The initial frequencies of the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109) satisfy the following condition: ， ， ， in, The initial frequencies of the first Raman laser are respectively The initial frequency of the fourth Raman laser; and They are In atomic energy levels lines The energy level difference between the two ground states of the energy level and In atomic energy levels lines The energy level difference between the two ground states of an energy level; This is a preset frequency difference limit.

4. The gravity difference measurement method according to claim 3, characterized in that, The initial frequencies of the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109) satisfy the following conditions: ， ， ， in, As the frequency reference zero, equal to Atom The transition frequency of the line |F=3>-|F'=4>.

5. The gravity difference measurement method according to claim 4, characterized in that, The light intensities of the first Raman laser (106), the second Raman laser (107), the third Raman laser (108), and the fourth Raman laser (109) satisfy the following conditions: ， in, The light intensity of the first Raman laser The intensity of the fourth Raman laser.

6. The gravity difference measurement method according to claim 3 or 4, characterized in that: The first π / pulse, π pulse, second π / The frequency of the third Raman laser (108) corresponding to the pulse is the initial frequency of the third Raman laser. ; First π / pulse, π pulse, second π / The frequency of the fourth Raman laser (109) corresponding to the pulse is the initial frequency of the fourth Raman laser. ; In the π pulse group with odd serial numbers, the first The frequencies of the third Raman laser (108) and the fourth Raman laser (109) corresponding to the π pulses are respectively: ， ， in, The π pulse groups with odd numbers are the first π pulse group and the third π pulse group; This indicates the π pulse group with odd numbers. The frequency of the third Raman laser in each π pulse; This indicates the π pulse group with odd numbers. The frequency of the fourth Raman laser in the π pulses; This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser; This indicates the π pulse group with odd numbers. The frequency change of the fourth Raman laser corresponding to each π pulse: ， ， The sequence number of the π pulses in a π pulse group with an odd sequence number , This represents the total number of π pulses in a π pulse group. Indicates rounding up; yes Atomic Doppler shift; yes Atomic Doppler shift; In the even-numbered π pulse group, the first... The frequencies of the third Raman laser (108) and the fourth Raman laser (109) in the π pulses are respectively: ， ， in, The π pulse groups with even numbers are the second π pulse group and the fourth π pulse group; This indicates the π pulse group with even numbers. The frequency of the third Raman laser in each π pulse; This indicates the π pulse group with even numbers. The frequency of the fourth Raman laser in the π pulses; This indicates the π pulse group with even numbers. Each π pulse corresponds to the frequency change of the third Raman laser; This indicates the π pulse group with even numbers. The frequency change of the fourth Raman laser corresponding to each π pulse: ， ， The sequence number of the π pulses in a π pulse group with an even sequence number , This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the third Raman laser; This indicates the π pulse group with odd numbers. Each π pulse corresponds to the frequency change of the fourth Raman laser.

7. The gravity difference measurement method according to claim 1, characterized in that: Step 2 specifically includes the following steps: Using a cooled laser (104) and a three-dimensional magneto-optical trap (3D-MOT) to... Atoms and Atoms are simultaneously cooled and loaded, and the cooling laser (104) forms an atomic fountain with a (0,0,1) configuration; the loaded cold atom clusters (101) are subjected to free fall or vertical downward throwing, and then vertical upward throwing.

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