Fully common-mode rejection two-component atom interferometer and method for differential measurement of gravity

Abstract

The application discloses a complete common-mode rejection two-component atomic interferometer, comprising a vacuum system, a probe laser, a second Raman laser, a third Raman laser and compensation light arranged above the top of the vacuum system, and a mirror arranged below the bottom of the vacuum system, wherein the first Raman laser and the fourth Raman laser are reflected by the mirror and then enter the vacuum system from the bottom of the vacuum system and propagate upwards along a direction parallel to the central axis of the vacuum system; the two-component atomic interferometer can realize complete suppression of common-mode noise during differential measurement by setting the specific frequency relationship, the light intensity proportion relationship and the spatial position relationship of the Raman lasers corresponding to the first component and the second component of the cold atomic group in the vacuum system. The application solves the technical bottleneck problem that the measurement precision is limited due to the fact that the internal state controllable two-component atomic interferometer noise cannot be completely suppressed common mode.

Description

Technical Field

[0001] The present invention relates to the field of quantum precision measurement, and in particular to a complete common-mode suppression two-component atom interferometer and a gravity differential measurement method. Background Art

[0002] At present, traditional single-component atom interferometers have matured and are widely used in basic and applied fields; two-component atom interferometers are mainly used in equivalence principle test experiments, but they also have great potential in other basic and applied research fields in the future.

[0003] In the two-component experiment, due to and There are differences in the ground state hyperfine structure. The corresponding frequency intervals in the line transitions are approximately 3.0357 GHz and 6.8347 GHz, respectively, which requires that the respective Raman laser systems must independently match the appropriate frequency difference. The existing two-component atom interferometer scheme has the following drawbacks:

[0004] Bragg transition single diffraction scheme:

[0005] It can simultaneously achieve coherent manipulation and complete common-mode suppression of two-component atoms; they are always in the same internal state during the interference process, which brings great advantages such as insensitivity to magnetic, optical and other system effects and complete common-mode suppression of vibration and phase noise, but also makes it difficult to effectively manipulate the internal state of atoms; in order to obtain sufficient diffraction efficiency and coherence, Bragg diffraction usually requires an ultracold atomic source with a narrower momentum distribution, which increases the complexity and cost of the experimental system and limits its wide application.

[0006] Bragg transition double diffraction scheme:

[0007] Similar to the single-diffraction Bragg scheme, the double-diffraction Bragg scheme offers advantages in terms of improving momentum transfer efficiency and achieving large-area interference. It also achieves complete common-mode rejection and is insensitive to system effects. However, its core drawback is that the Bragg transition does not alter the atomic internal state, making internal state manipulation and detection difficult. The need for an ultracold atomic source limits its widespread application.

[0008] Stimulated Raman transition single diffraction scheme:

[0009] It is possible to achieve relatively independent coherent manipulation of two-component atoms simultaneously, but because there is only one common laser and the two groups of Raman lasers have a frequency difference. Currently, the vibration noise common mode suppression ratio of this scheme is only 10 -1 ~10 -5The common-mode rejection ratio of phase noise is lower, only slightly better than absolute measurement. Although internal state marker detection can be achieved, the different internal states of the upper and lower interferometer arms during the interference process make it sensitive to magnetic and optical system effects, limiting its measurement accuracy.

[0010] Stimulated Raman transition double diffraction scheme:

[0011] It can simultaneously realize relatively independent coherent manipulation of two-component atoms; share chirp lasers to achieve common-mode suppression of laser phase noise; its interference process is always in the same internal state and is insensitive to magnetic, optical and other system effects; it can realize internal state label detection. However, due to the frequency difference between the two groups of Raman lasers, the common-mode suppression ratio of vibration noise of this scheme is less than 10 -5 level, it is impossible to achieve complete common-mode suppression of noise, and it will also introduce systematic errors such as wave vector difference, limiting the measurement accuracy. Summary of the Invention

[0012] Due to the existence of existing technology and There is a frequency difference between the two groups of Raman lasers of atoms, which results in the inability to achieve complete common-mode suppression of vibration and phase noise in the stimulated Raman transition double diffraction scheme, and at the same time leads to systematic errors caused by wave vector differences, limiting the high precision of its measurement. The present invention provides a complete common-mode suppression two-component atom interferometer and a gravity differential measurement method.

[0013] The technical solutions of the present invention are as follows:

[0014] A completely common-mode suppressed two-component atom interferometer comprises a vacuum system, wherein the upper outer shell of the vacuum system is provided with a magnetic shielding system, and the top of the magnetic shielding system is open; the bottom area within the vacuum system is an ejection area, and the initial position of the cold atomic cluster is located in the ejection area, and the cold atomic cluster includes atomic clusters of two components; a detection area is provided at the lower part of the vacuum system, and the detection area is located above the ejection area; a fluorescence collection system and an imaging CCD are sequentially provided at a position outside the vacuum system and corresponding to the detection area; a cooling laser is provided at a position outside the vacuum system corresponding to the ejection area, and a detection laser, a second Raman laser, a third Raman laser and compensation light are provided above the top of the vacuum system, and the compensation light is used to reduce the AC Stark frequency shift error; a reflector is provided below the bottom of the vacuum system, and the first Raman laser and the fourth Raman laser are reflected by the reflector and incident on the vacuum system from the bottom of the vacuum system, and then propagate upward along a direction parallel to the central axis of the vacuum system.

[0015] As described above, the frequency difference between the first Raman laser and the second Raman laser is related to the The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser is The detuning of the single photon between the ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the second Raman laser is in direct contact with the first component. The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value;

[0016] The frequency difference between the third Raman laser and the fourth Raman laser is the same as that of the first component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the third Raman laser is the same as the first component. The detuning of the single photon between the upper ground state energy level and the highest energy level in the intermediate state is greater than the preset detuning limit value, and the fourth Raman laser is detuned with the first component. The single-photon detuning between the lower ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value;

[0017] The frequency difference between the first Raman laser and the third Raman laser is related to the frequency of the second component The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser and the second component The single photon detuning between the upper ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the third Raman laser is closely related to the second component. The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value;

[0018] The frequency difference between the second Raman laser and the fourth Raman laser is related to the The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the second Raman laser is The detuning of the single photon between the upper ground state energy level and the highest energy level in the intermediate state is greater than the preset detuning limit value, and the fourth Raman laser is detuned with the second component. The single-photon detuning between the lower ground state energy level of the line and the highest energy level in the intermediate state is greater than the preset detuning limit value.

[0019] As mentioned above, the first component of the cold atomic group is , the second group is divided into ; and of In the two-photon process of line transition, The two ground state energy levels of energy level splitting, namely the lower ground state |g> energy level and the upper ground state |e> energy level, are the final states of the two-photon process. The lower ground state |g> energy level is the lower state, and the upper ground state |e> energy level is the upper state. The four energy levels of energy level splitting |a>, |b>, |c> and |d> are the intermediate states of the two-photon process.

[0020] As described above, the absolute frequencies and intensities of the first Raman laser, the second Raman laser, the third Raman laser, the fourth Raman laser, and the compensation light are specifically set according to the following steps:

[0021] Step A2.1: Based on the following constraints and the frequency difference between the four Raman laser beams, calculate the frequency of the first Raman laser beam, the frequency of the compensation light beam, and the ratio of the electric field intensity of the four Raman laser beams to the compensation light beam. , thereby offsetting the frequency shift caused by the AC Stark effect. The four Raman lasers include the first Raman laser, the second Raman laser, the third Raman laser, and the fourth Raman laser:

[0022] ,

[0023] in:

[0024] It is the preset Rabi frequency difference limit value, which is used to limit the use of and All close;

[0025] yes The Rabi frequency under the action of the first Raman laser and the second Raman laser,

[0026] yes The Rabi frequency under the action of the third Raman laser and the fourth Raman laser,

[0027] yes The Rabi frequency under the action of the first Raman laser and the third Raman laser,

[0028] yes The Rabi frequency under the action of the second Raman laser and the fourth Raman laser,

[0029] yes The relative optical frequency shift of the atomic |g> and |e> energy levels,

[0030] yes The relative optical frequency shift of the atomic |g> and |e> energy levels,

[0031] The electric field intensity of the first Raman laser to the electric field intensity of the fourth Raman laser,

[0032] To compensate for the electric field intensity of light;

[0033] Step A2.2: According to the set intensity of the first Raman laser, the electric field intensity ratio as well as The second Raman laser, the third Raman laser, the fourth Raman laser and the compensation light intensity are obtained; wherein, when the laser sequence number , It is The intensity of the Raman laser is , is the intensity of the compensation light;

[0034] According to the frequency of the first Raman laser beam calculated in step A2.1 and the frequency differences between the four Raman laser beams, the absolute value of the frequency of each Raman laser beam is determined.

[0035] As mentioned above 、 、 and Calculate using the following formulas:

[0036] ,

[0037] ,

[0038] ,

[0039] ,

[0040] When the laser serial number , It is The frequency of the Raman laser,

[0041] yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level,

[0042] yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level,

[0043] m is the ground state energy level symbol g or e,

[0044] n is the symbol of the intermediate state energy level a, b, c, d,

[0045] yes The energy difference between the atomic |b> level and the |e> level,

[0046] yes The energy difference between the atomic |c> level and the |e> level,

[0047] yes The energy difference between the atomic |b> level and the |e> level,

[0048] yes The energy difference between the atomic |c> level and the |e> level,

[0049] is the reduced Planck constant.

[0050] As mentioned above and Calculate using the following formulas:

[0051] ,

[0052] ,

[0053] ,

[0054] ,

[0055] ,

[0056] ,

[0057] When the laser serial number , is the frequency of the compensation light;

[0058] yes The optical frequency shift of the atomic |g> energy level,

[0059] yes Frequency shift of light at atomic |e> energy levels,

[0060] yes The optical frequency shift of the atomic |g> energy level,

[0061] yes Frequency shift of light across atomic |e> energy levels.

[0062] As described above, the relative frequency relationship between the first Raman laser, the second Raman laser, the third Raman laser, and the fourth Raman laser satisfies:

[0063] ,

[0064] ,

[0065] ,

[0066] When the laser serial number , It is The frequency of the Raman laser.

[0067] A gravity differential measurement method, using any of the above complete common-mode rejection two-component atom interferometers, specifically comprises the following steps:

[0068] Step B1, building a two-component atom interferometer with complete common-mode suppression;

[0069] Step B2: The cold atomic clusters are cooled and trapped at the bottom of the vacuum system by a cooling laser, and then thrown upward to form an atomic fountain;

[0070] Step B3, realize Mach-Zehnder atomic interferometer by π / 2-π-π / 2 triple pulse, the cold atomic group At the moment, the first π / 2 Raman pulse is applied to realize the beam splitting of one atom; after the free evolution time T, At the same time, a π Raman pulse is applied to realize the reflection of atoms in two paths; after a free evolution time T, At this moment, the second π / 2 Raman pulse acts to combine the atomic paths and thus achieve atomic interference. Both the π / 2 Raman pulse and the π Raman pulse are composed of four Raman laser beams and compensation light.

[0071] Step B4: applying quenching light and detection laser in sequence, and capturing interference fringes of atoms corresponding to the two components respectively through a fluorescence collection system and an imaging CCD;

[0072] Extract the interference phase of the atoms corresponding to the two components respectively;

[0073] The phase difference is obtained by the difference in the interference phase of the atoms corresponding to the two components. ,according to Get the differential acceleration due to gravity , is the effective wave vector, T is the free evolution time,

[0074] ,

[0075] ,

[0076] ,

[0077] It is The wave vector of Raman laser corresponds to the laser serial number ;

[0078] yes The effective wave vector of yes The effective wave vector.

[0079] Compared with the prior art, the present invention has the following beneficial effects:

[0080] The present invention considers of Line transition and of Line transition, by designing the frequency and intensity of four Raman laser beams, introducing the fifth beam as compensation light, and optimizing the propagation direction of Raman laser, ensure and The Rabi frequencies are close, the relative AC Stark frequency shifts are close to zero, and the effective k wave vectors are completely consistent, achieving complete common-mode suppression, eliminating the noise and system errors caused by wave vector differences from the root.

[0081] Effectively eliminate the system error caused by wave vector difference: four-beam Raman laser frequency is precisely configured to make and A completely consistent effective k-wave vector is obtained in the double-diffraction interference process, which completely eliminates the systematic error caused by wave vector mismatch, thereby greatly improving the contrast and stability of the interference signal.

[0082] Precise compensation of AC Stark frequency shift: By adjusting the laser intensity ratio and introducing compensating light, the AC Stark frequency shifts of the two groups of atoms are precisely complemented, so that the Rabi oscillation frequency in the two-component system remains consistent, further reducing the error caused by light intensity drift and ensuring high-precision interferometric phase measurement.

[0083] The accuracy of gravity differential measurement is greatly improved: the fully common-mode Raman laser solution effectively suppresses the joint influence of the external environment (such as mechanical vibration and temperature changes) on the two groups of atoms. In gravity differential measurement, the sensitivity and stability of gravitational acceleration measurement are improved by differential calculation of the interference phase of the two groups of atoms.

[0084] In general, the present invention solves the technical difficulties in common-mode suppression of vibration noise and laser phase noise in a two-component atom interferometer with controllable internal states in a simple way, achieves complete common-mode suppression in the two-component atomic system, improves measurement stability, and can be extended to differential measurement experiments of atoms with other isotopic components. It is suitable for high-precision measurement of two-component atom interferometers and related application fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] Figure 1 This is a schematic diagram of the structure of a two-component atom interferometer with complete common-mode suppression.

[0086] Wherein, 101 - cold atom group, 102 - vacuum system, 103 - magnetic shielding system, 104 - cooling laser, 105 - probe laser, 106 - first Raman laser, 107 - fourth Raman laser, 108 - second Raman laser, 109 - third Raman laser, 110 - fluorescence collection system, 111 - imaging CCD, 112 - mirror, 113 - compensation light;

[0087] Figure 2 For the Raman laser energy level configuration in the two-component atom interferometer with complete common mode rejection in the embodiment of the application,

[0088] Wherein, And Both represent the electronic configuration, The two ground state energy levels of energy level splitting, i.e. the lower ground state |g> energy level and the upper ground state |e> energy level, are the final states of the two-photon process, the lower ground state |g> energy level is the lower state, and the upper ground state |e> energy level is the upper state, The four energy levels |a>, |b>, |c> and |d> of energy level splitting are the intermediate states of the two-photon process;

[0089] Figure 3 For the frequency and light intensity configuration diagram of the Raman laser and the compensation light in the embodiment of the application,

[0090] Wherein, Chirp rate is represented, 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 frequency of the Raman laser is the first Laser number ;

[0091] Figure 4 For the Rabi frequency and the first Raman laser misadjustment relationship diagram in the embodiment of the application,

[0092] Wherein The Rabi frequency under the action of the first Raman laser and the second Raman laser is

[0093] The Rabi frequency under the action of the third Raman laser and the fourth Raman laser is The Rabi frequency under the action of the first Raman laser and the third Raman laser is

[0094] The Rabi frequency under the action of the second Raman laser and the fourth Raman laser is

[0095] The Rabi frequency under the action of the second Raman laser and the fourth Raman laser is ;

[0096] ​​​ Figure 5 The complete common mode suppression dual-component atom interferometer in the embodiment of the present invention is Interference loop; For the Raman laser wave vector, corresponding laser serial number ;m F represents the magnetic quantum number, and the up and down arrows represent the corresponding direction of light propagation; The moment is the first π / 2 Raman pulse action moment, The time is the time when the π Raman pulse acts, The moment is the second π / 2 Raman pulse action moment;

[0097] Figure 6 The complete common mode suppression dual-component atom interferometer in the embodiment of the present invention is Interference loop; For the Raman laser wave vector, corresponding laser serial number ;m F represents the magnetic quantum number, and the up and down arrows represent the corresponding direction of light propagation; The moment is the first π / 2 Raman pulse action moment, The time is the time when the π Raman pulse acts, The moment is the second π / 2 Raman pulse action moment;

[0098] Figure 7 Schematic diagram of the flow of the gravity differential measurement method using a completely common-mode suppressed two-component atom interferometer in the present invention. DETAILED DESCRIPTION

[0099] In order to facilitate those skilled in the art to understand and implement the present invention, the present invention is further described in detail below with reference to the embodiments. The embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0100] Example 1

[0101] Complete common-mode rejection two-component atom interferometer, such as Figure 1 As shown, the cold atomic group 101 includes two components of atomic groups. In this embodiment, the first component is , the second group is divided into ), vacuum system 102, magnetic shielding system 103, cooling laser 104, detection laser 105, first Raman laser 106, fourth Raman laser 107, second Raman laser 108 and third Raman laser 109, fluorescence collection system 110, imaging CCD 111, angle with the ground The reflector 112 and the compensation light 113 are placed, and the specific structure is as follows:

[0102] The upper outer shell of the vacuum system 102 is provided with a magnetic shielding system 103, and the top of the magnetic shielding system 103 is open; the bottom area of ​​the vacuum system 102 is the ejection area, and the cold atomic group 101 is initially located in the ejection area. The lower part of the vacuum system 102 is provided with a detection area, which is located above the ejection area. A fluorescence collection system 110 and an imaging CCD 111 are sequentially provided outside the vacuum system 102 and at a position corresponding to the detection area; cooling lasers 104 are provided on the outside of the vacuum system 102 and at a position corresponding to the ejection area (three pairs of cooling lasers 104 are arranged, and each pair is perpendicular to each other, Figure 1 Only two pairs of horizontally propagating cooling lasers 104 are drawn in the figure. The two beams of light in the other pair of cooling lasers 104 propagate relative to each other along the extension direction of the vacuum system 102). A detection laser 105, a second Raman laser 108, a third Raman laser 109, and a compensation light 113 are arranged above the top of the vacuum system 102. A reflector 112 is arranged below the bottom of the vacuum system 102. The horizontal first Raman laser 106 and the fourth Raman laser 107 are reflected by the reflector 112, enter the vacuum system 102 from the bottom, and then propagate upward along the extension direction parallel to the central axis of the vacuum system 102.

[0103] Figure 2 This is the Raman laser energy level configuration in a two-component atom interferometer with complete common-mode suppression. The red solid line represents the four-beam Raman laser pair. and of Two-photon process of line transition, The two ground state energy levels of energy level splitting, namely the lower ground state |g> energy level and the upper ground state |e> energy level, are the final states of the two-photon process. The lower ground state |g> energy level is the lower state, and the upper ground state |e> energy level is the upper state. The four energy levels of energy level splitting |a>, |b>, |c> and |d> are the intermediate states of the two-photon process.

[0104] The present invention precisely configures the directional light intensity and frequency of four Raman laser beams to make them consistent with the Rabi frequency of the interaction between atoms and lasers. At the same time, compensation light is introduced to ensure that the optical frequency shifts of the upper and lower energy levels are consistent and the same as the effective wave vector of the interferometer, thus realizing a two-component double-diffraction atom interferometer with complete common-mode suppression.

[0105] In this embodiment, four Raman laser beams with frequency differences of 3.036 GHz, 3.799 GHz, and 3.036 GHz are used (i.e., the frequency difference between the first Raman laser 106 and the second Raman laser 108 is 3.036 GHz, the frequency difference between the second Raman laser 108 and the third Raman laser 109 is 3.799 GHz, and the frequency difference between the third Raman laser 109 and the fourth Raman laser 107 is 3.036 GHz). Figure 3 The frequency and intensity configuration diagram of the Raman laser and the compensation light in the embodiment of the present invention enables the two cold atomic groups 101 to achieve synchronous double-diffraction atomic interference in the vacuum system 102; at the same time, an additional fifth laser beam, namely the compensation light 113, is added, as shown in FIG. Figure 1 As shown, the light intensity ratios of the first Raman laser 106, the second Raman laser 108, the third Raman laser 109, the fourth Raman laser 107 and the compensation light 113 are set to 1.00: 2.01: 3.42: 4.04: 0.700, respectively, to offset the optical frequency shift during atomic interference and keep the four Rabi frequencies consistent during the interaction between the two atoms and the Raman laser, thereby achieving complete suppression of common mode noise. Finally, by Figure 1 The device structure shown achieves gravity differential measurement with complete suppression of common-mode noise.

[0106] The first Raman laser 106, the second Raman laser 108, the third Raman laser 109, the fourth Raman laser 107 and the compensation light 113 are specifically set according to the following steps:

[0107] Step A1: Determination of the relative frequency configuration of Raman laser

[0108] According to the frequency difference between the upper and lower energy levels of the two components and the atomic interferometer in the experiment, the relative frequency configuration of the four Raman lasers is determined to achieve synchronous resonance of the two-component atoms:

[0109] The frequency difference between the first Raman laser 106 and the second Raman laser 108 is related to the The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser 106 and the first component The detuning of the single photon of the ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the second Raman laser 108 is closer to the first component. The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value;

[0110] The frequency difference between the third Raman laser 109 and the fourth Raman laser 107 is the same as that of the first component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the third Raman laser 109 is the same as the first component. The detuning of the single photon between the upper ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value, and the fourth Raman laser 107 and the first component The single-photon detuning between the lower ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value;

[0111] The frequency difference between the first Raman laser 106 and the third Raman laser 109 is related to the frequency of the second component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser 106 and the second component The detuning of the single photon of the ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the third Raman laser 109 and the second component The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value;

[0112] The frequency difference between the second Raman laser 108 and the fourth Raman laser 107 is proportional to the frequency of the second component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the second Raman laser 108 is the same as the second component. The detuning of the single photon between the ground state energy level of the line and the highest energy level in the intermediate state is greater than the preset detuning limit value, and the fourth Raman laser 107 and the second component The single-photon detuning between the lower ground state energy level of the line and the highest energy level in the intermediate state is greater than the preset detuning limit value.

[0113] In this embodiment, four Raman laser beams are used, wherein the relative frequency relationship satisfies:

[0114] ,

[0115] ,

[0116] ,

[0117] When the laser serial number , It is The frequency of Raman laser; The wave vector of Raman laser is denoted as ;

[0118] This frequency relationship is for and of The frequency difference between the upper and lower energy levels of the two-photon process of the line transition is set so that the frequency difference between the first Raman laser 106 and the second Raman laser 108 is the same as that of the first component of The frequency difference between the two ground state energy levels of the line (the lower ground state |g> energy level and the upper ground state |e> energy level) is the same, the two-photon detuning is zero, and the detuning between the first Raman laser 106 and the upper ground state |e> energy level and the single photon of the intermediate state is less than a preset detuning limit value, and the detuning between the second Raman laser 108 and the lower ground state |g> energy level and the single photon of the intermediate state is less than a preset detuning limit value;

[0119] The frequency difference between the third Raman laser 109 and the fourth Raman laser 107 is the same as that of the first component of The frequency difference between the two ground state energy levels of the line (the lower ground state |g> energy level and the upper ground state |e> energy level) is the same, the two-photon detuning is zero, and the single-photon detuning of the third Raman laser 109 with the upper ground state |e> energy level and the highest energy level in the intermediate state (i.e., the |d> energy level) is greater than a preset detuning limit value, and the single-photon detuning of the fourth Raman laser 107 with the lower ground state |g> energy level and the highest energy level in the intermediate state (i.e., the |d> energy level) is greater than a preset detuning limit value;

[0120] The frequency difference between the first Raman laser 106 and the third Raman laser 109 is related to the second component of The frequency difference between the two ground state energy levels (the lower ground state |g> energy level and the upper ground state |e> energy level) of the line is the same, the two-photon detuning is zero, and the detuning between the first Raman laser 106 and the upper ground state |e> energy level and the single photon of the intermediate state is less than a preset detuning limit value, and the detuning between the third Raman laser 109 and the lower ground state |g> energy level and the single photon of the intermediate state is less than a preset detuning limit value;

[0121] The frequency difference between the second Raman laser 108 and the fourth Raman laser 107 is related to the second component of The frequency difference between the two ground state energy levels of the line (the lower ground state |g> energy level and the upper ground state |e> energy level) is the same, the two-photon detuning is zero, and the single-photon detuning of the second Raman laser 108 with the upper ground state |e> energy level and the highest energy level in the intermediate state (i.e., the |d> energy level) is greater than a preset detuning limit value, and the single-photon detuning of the fourth Raman laser 107 with the lower ground state |g> energy level and the highest energy level in the intermediate state (i.e., the |d> energy level) is greater than a preset detuning limit value.

[0122] This ensures that all four Raman laser beams can nearly resonate with the two atoms and achieve double-diffraction Raman transitions.

[0123] Step A2: Determine the absolute frequency of the Raman laser, adjust the intensity, and perform AC Stark compensation

[0124] Assuming that the light intensities of the four Raman laser beams (i.e., the first Raman laser 106, the second Raman laser 108, the third Raman laser 109, and the fourth Raman laser 107) and the absolute frequency of the first Raman laser 106 are variables, the light intensities of the four Raman laser beams are adjusted so that and The Rabi frequencies of the two groups of atoms are matched as much as possible, so that the interference process of the two groups of atoms proceeds synchronously. The specific operation is as follows:

[0125] Step A2.1: Based on the following constraints and the frequency difference between the four Raman laser beams, calculate the frequency of the first Raman laser 106, the frequency of the compensation light 113, and the ratio of the electric field intensity of the four Raman laser beams to the compensation light 113. , thereby canceling the frequency shift caused by the AC Stark effect:

[0126]

[0127] in:

[0128] It is the preset Rabi frequency difference limit value, which is used to limit the use of and All close;

[0129] yes The Rabi frequency under the action of the first Raman laser and the second Raman laser,

[0130] yes The Rabi frequency under the action of the third Raman laser and the fourth Raman laser,

[0131] yes The Rabi frequency under the action of the first Raman laser and the third Raman laser,

[0132] yes The Rabi frequency under the action of the second Raman laser and the fourth Raman laser,

[0133] yes The relative optical frequency shift of the atomic |g> and |e> energy levels,

[0134] yes The relative optical frequency shift of the atomic |g> and |e> energy levels,

[0135] The electric field intensity of the first Raman laser to the electric field intensity of the fourth Raman laser,

[0136] To compensate for the electric field intensity of light;

[0137] (1) For the first type of constraints (i.e., the four Rabi frequencies are close):

[0138] 、 、 and Calculate using the following formulas:

[0139] ,

[0140] ,

[0141] ,

[0142] ,

[0143] When the laser serial number , It is The electric field intensity of Raman laser is , is the electric field intensity of the compensation light;

[0144] When the laser serial number , It is The frequency of the Raman laser is , is the frequency of the compensation light;

[0145] yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level,

[0146] yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level;

[0147] m is the ground state energy level symbol g or e,

[0148] n is the intermediate energy level symbol a, b, c, d, where |g>, |e>, |a>, |b>, |c>, |d> energy levels are as follows Figure 2 As shown, the energy levels of |g>, |e>, |a>, |b>, |c>, and |d> are from low to high;

[0149] yes The energy difference between the atomic |b> level and the |e> level,

[0150] yes The energy difference between the atomic |c> level and the |e> level,

[0151] yes The energy difference between the atomic |b> level and the |e> level,

[0152] yes The energy difference between the atomic |c> level and the |e> level;

[0153] is the reduced Planck constant.

[0154] (2) For the second type of constraint (i.e., the relative optical frequency shift approaches zero):

[0155] In order to reduce the AC Stark frequency shift error caused by the light field, a compensation light 113 is introduced into the system (the wave vector corresponding to the compensation light 113 is denoted as , corresponding to the laser serial number ),like Figure 1 As shown, let the absolute frequency and intensity of the compensation light 113 be variables, and calculate and The relative optical frequency shift of the ground state |g> and |e> energy levels, such as Figure 2 shown.

[0156] and Calculate using the following formulas:

[0157] ,

[0158] ,

[0159] ;

[0160] ,

[0161] ,

[0162] ;

[0163] yes The optical frequency shift of the atomic |g> energy level,

[0164] yes Frequency shift of light at atomic |e> energy levels,

[0165] yes The optical frequency shift of the atomic |g> energy level,

[0166] yes Frequency shift of light across atomic |e> energy levels.

[0167] The step A2.1 is performed by approaching the four Rabi frequencies, and when the relative optical frequency shift approaches zero (i.e., taking |+| | minimum value), so that the frequency shifts of the two groups of atoms due to the AC Stark effect cancel each other out, thereby obtaining the electric field intensity ratio of the four Raman lasers and the compensation light ;

[0168] Step A2.2, according to the set intensity of the first Raman laser 106 (denoted as the intensity of the first Raman laser ), the electric field strength ratio as well as (When the laser serial number , It is The intensity of the Raman laser is , is the intensity of the compensation light) to obtain the intensity of the second Raman laser 108, the third Raman laser 109, the fourth Raman laser 107 and the compensation light 113;

[0169] The frequency of the first Raman laser 106 calculated in step A2.1 And the frequency difference of the four Raman laser beams in step A1 is used to determine the absolute value of the frequency of each Raman laser.

[0170] This step ensures the contrast of the interference signal and the accuracy of the phase measurement.

[0171] In this embodiment, the intensity of the first Raman laser is set to ,like Figure 1 As shown, substitute into this design and Parameters, to obtain the optimal light intensity and frequency configuration, = For the convenience of observation, this embodiment is set of In the line transition, |F=3>-|F'=4> is the frequency reference zero point, and the corresponding frequency of the first Raman laser is , the frequency of the compensation light , determine the absolute frequencies of the Raman laser and the compensation light based on the relative frequencies in step 1. Under this configuration, ,| Compared with the typical frequency shift in traditional schemes, this scheme reduces the relative AC Stark frequency shift to below the kHz level, such as Figure 4 As shown, when the frequency of the first Raman laser Optimized to 4.080 GHz, and The Rabi frequency curve reaches equilibrium at the intersection point.

[0172] Example 2

[0173] The gravity differential measurement method utilizes the fully common-mode suppressed two-component atom interferometer described in Example 1. Figure 7 Schematic diagram of the flow of the gravity differential measurement method using a completely common-mode suppressed two-component atom interferometer in the present invention:

[0174] Step B1: Build the optical path and dual diffraction wave vector configuration of the fully common-mode suppressed two-component atom interferometer

[0175] Optical path alignment: four Raman lasers are fixed on the same optical platform by precise optical adjustment, and the four Raman lasers, compensation light 113 and probe light 105 are introduced into the vacuum system 102 through optical fibers:

[0176] By precisely adjusting the incident angle and propagation direction of each laser beam, the first Raman laser 106 The fourth Raman laser 107 is upward, the second Raman laser 108 is downward, and the third Raman laser 109 is downward, Figure 1 as shown.

[0177] For System: Figure 5 The complete common mode rejection dual-component atom interferometer in the embodiment of the application The interference loop, the first Raman laser 106 and the second Raman laser 108 provide positive momentum pulses, the third Raman laser 109 and the fourth Raman laser 107 provide negative momentum pulses, and the effective wave vector :

[0178]

[0179] For System: Figure 6 The complete common mode rejection dual-component atom interferometer in the embodiment of the application The interference loop, the first Raman laser 106 and the third Raman laser 109 provide positive momentum pulses, the second Raman laser 108 and the fourth Raman laser 107 provide negative momentum pulses, and the effective wave vector :

[0180]

[0181] The effective wave vectors of the two groups of atoms are completely consistent, and common mode rejection is achieved.

[0182] Double diffraction implementation: using the above optical path, a double diffraction scheme is formed, so that the atoms realize the same internal state and diffraction in two directions when affected by the Raman pulse. This configuration doubles the effective wave vector and amplifies the cumulative effect of the interference phase, reduces the phase noise caused by the external environment (such as mechanical vibration), and at the same time makes the two groups of atoms in the same laser field environment.

[0183] Step B2, atom preparation and loading:

[0184] and ​​The corresponding cold atomic cluster 101 is cooled and trapped by the cooling laser 104 at the bottom of the vacuum system 102, and then thrown upward to form an atomic fountain. During the upward throwing process, the cold atomic cluster 101 enters the corresponding area of ​​the magnetic shielding system 103. At this time, Atoms and The atom is mainly in the first final state (the first final state is the upper ground state |e> or the lower ground state |g>). The energy level structure of the atom is as follows Figure 2 shown.

[0185] Step B3: Perform two-component double-diffraction atomic interferometry:

[0186] Atoms and After the atoms enter the magnetic shielding system 103, the traditional π / 2-π-π / 2 triple pulse is used to realize the Mach-Zehnder atomic interferometer. The process is as follows: Figure 4 As shown. Cold atom cluster 101 At the moment, the first π / 2 Raman pulse is applied to realize the beam splitting of one atom; after the free evolution time T, At the same time, a π Raman pulse is applied to realize the reflection of atoms in two paths; after a free evolution time T, At this moment, the second π / 2 Raman pulse acts to achieve the beam combination of the atomic paths, thereby achieving atomic interference. and The atoms are mainly in the second final state. The π / 2 Raman pulse and the π Raman pulse are both composed of four Raman laser beams and compensation light 113, which can realize the two-photon Raman transition of atoms in the upper ground state |e> and the lower ground state |g>.

[0187] Step B4: Gravity differential measurement:

[0188] Apply quenching light and The atom returns to the first final state and uses the Detection light, The detection light, fluorescence collection system 110 and imaging CCD 111 capture Atomic interference fringes and Atomic interference fringes;

[0189] Extracted through data processing module The atomic interference phase and Interference phase of atoms;

[0190] Depend on The atomic interference phase and The difference in the interference phase of the atoms is the phase difference ,according to Get the differential acceleration due to gravity .

[0191] Due to the fully common-mode Raman laser configuration, the phase difference caused by gravity exist and The atoms are recorded synchronously, while non-common mode noise is effectively suppressed. is the effective wave vector, and the Raman laser is completely common mode, that is, , T is the free evolution time, , and They are The free evolution time of atoms and The free evolution time of atoms. For a two-component system, we can obtain The atomic interference phase and The interference phase of the atoms, and then calculate the phase difference between the two Phase difference The difference from the acceleration due to gravity The differential acceleration of gravity can be obtained by calibration and data fitting. The measurement results verify the common-mode rejection effect.

[0192] Complete common-mode rejection technology ensures that external environmental interference (such as vibration and temperature drift) has the same impact on the two-component atoms, thereby canceling each other out in the differential, greatly improving measurement accuracy.

[0193] The specific embodiments described herein are merely illustrative of the spirit of the present invention. Persons skilled in the art may make various modifications, additions, or substitutions to the described specific embodiments without departing from the spirit of the present invention or exceeding the scope of the appended claims.

Claims

1. Complete common-mode suppression two-component atom interferometer, characterized by: The invention comprises a vacuum system (102), wherein the upper outer shell of the vacuum system (102) is provided with a magnetic shielding system (103), and the top of the magnetic shielding system (103) is open; the bottom area in the vacuum system (102) is an ejection area, and the initial position of the cold atomic group (101) is located in the ejection area, and the cold atomic group (101) includes atomic groups of two components; a detection area is provided in the lower part of the vacuum system (102), and the detection area is located above the ejection area; a fluorescence collection system (110) and an imaging CCD (111) are sequentially provided outside the vacuum system (102) and at a position corresponding to the detection area; a cooling laser (104) is provided outside the vacuum system (102) and at a position corresponding to the ejection area; a detection laser (105), a second Raman laser (108), a third Raman laser (109) and a compensation light (113) are provided above the top of the vacuum system (102), and the compensation light (113) is used to reduce AC Stark frequency shift error, a reflector (112) is provided below the bottom of the vacuum system (102), the first Raman laser (106) and the fourth Raman laser (107) are reflected by the reflector (112), enter the vacuum system (102) from the bottom of the vacuum system (102), and then propagate upward along a direction parallel to the central axis of the vacuum system (102). The first component of the cold atomic group (101) is , the second group is divided into , ， ， It is The wave vector of Raman laser corresponds to the laser serial number , yes The effective wave vector of yes The effective wave vector.

2. The complete common-mode suppression two-component atom interferometer according to claim 1, characterized in that: described The frequency difference between the first Raman laser (106) and the second Raman laser (108) is related to the frequency of the first component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser (106) is the same as the first component. The single photon detuning between the ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the second Raman laser (108) is The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value; The frequency difference between the third Raman laser (109) and the fourth Raman laser (107) is the same as that of the first component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the third Raman laser (109) is the same as the first component. The single photon detuning between the upper ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value, and the fourth Raman laser (107) is The single-photon detuning between the lower ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value; The frequency difference between the first Raman laser (106) and the third Raman laser (109) is related to the frequency of the second component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the first Raman laser (106) is the same as the second component. The single photon detuning between the ground state energy level and the intermediate state of the line is less than the preset detuning limit value, and the third Raman laser (109) is The single-photon detuning between the lower ground state energy level and the intermediate state of the line is less than the preset detuning limit value; The frequency difference between the second Raman laser (108) and the fourth Raman laser (107) is related to the frequency of the second component. The frequency difference between the two ground state energy levels of the line is the same, the two-photon detuning is zero, and the second Raman laser (108) is the same as the second component. The single photon detuning between the upper ground state energy level and the highest energy level in the intermediate state of the line is greater than the preset detuning limit value, and the fourth Raman laser (107) is The single-photon detuning between the lower ground state energy level of the line and the highest energy level in the intermediate state is greater than the preset detuning limit value.

3. The complete common-mode suppression two-component atom interferometer according to claim 2, characterized in that: and of In the two-photon process of line transition, 5 The two ground state energy levels of energy level splitting, namely the lower ground state |g> energy level and the upper ground state |e> energy level, are the final states of the two-photon process. The lower ground state |g> energy level is the lower state, and the upper ground state |e> energy level is the upper state. The four energy levels of energy level splitting |a>, |b>, |c> and |d> are the intermediate states of the two-photon process.

4. The complete common-mode suppression two-component atom interferometer according to claim 3, characterized in that: The absolute frequencies and light intensities of the first Raman laser (106), the second Raman laser (108), the third Raman laser (109), the fourth Raman laser (107), and the compensation light (113) are specifically set according to the following steps: Step A2.1, based on the following constraints and the frequency difference between the four Raman laser beams, solve the frequency of the first Raman laser (106), the frequency of the compensation light (113), and the ratio of the electric field intensity of the four Raman laser beams to the compensation light (113): , thereby achieving the purpose of offsetting the frequency shift caused by the AC Stark effect, the four Raman lasers include a first Raman laser (106), a second Raman laser (108), a third Raman laser (109), and a fourth Raman laser (107): ， in: It is the preset Rabi frequency difference limit value, which is used to limit the use of and All close; yes The Rabi frequency under the action of the first Raman laser and the second Raman laser, yes The Rabi frequency under the action of the third Raman laser and the fourth Raman laser, yes The Rabi frequency under the action of the first Raman laser and the third Raman laser, yes The Rabi frequency under the action of the second Raman laser and the fourth Raman laser, yes The relative optical frequency shift of the atomic |g> and |e> energy levels, yes The relative optical frequency shift of the atomic |g> and |e> energy levels, The electric field intensity of the first Raman laser to the electric field intensity of the fourth Raman laser, To compensate for the electric field intensity of light; Step A2.2: According to the set intensity of the first Raman laser (106), the electric field intensity ratio as well as The light intensities of the second Raman laser (108), the third Raman laser (109), the fourth Raman laser (107) and the compensation light (113) are obtained; wherein, when the laser sequence number , It is The intensity of the Raman laser is , is the intensity of the compensation light; According to the frequency of the first Raman laser (106) calculated in step A2.1 and the frequency differences between the four Raman lasers, the absolute value of the frequency of each Raman laser is determined.

5. The complete common-mode suppression two-component atom interferometer according to claim 4, characterized in that: described 、 、 and Calculate using the following formulas: ， ， ， ， When the laser serial number , It is The frequency of the Raman laser, yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level, yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level, m is the ground state energy level symbol g or e, n is the intermediate energy level symbol a, b, c, d, yes The energy difference between the atomic |b> level and the |e> level, yes The energy difference between the atomic |c> level and the |e> level, yes The energy difference between the atomic |b> level and the |e> level, yes The energy difference between the atomic |c> level and the |e> level, is the reduced Planck constant.

6. The complete common-mode suppression two-component atom interferometer according to claim 4, characterized in that: described and Calculate using the following formulas: ， ， ， ， ， ， When the laser serial number , It is The frequency of the Raman laser; when the laser serial number , is the frequency of the compensation light; yes The optical frequency shift of the atomic |g> energy level, yes Frequency shift of light at atomic |e> energy levels, yes The optical frequency shift of the atomic |g> energy level, yes Frequency shift of light at atomic |e> energy levels, yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level, yes The electric dipole moment of the transition from the |m> energy level to the |n> energy level, m is the ground state energy level symbol g or e, n is the intermediate energy level symbol a, b, c, d, yes The energy difference from the |m> energy level to the |n> energy level transition, yes The energy difference between the |m> level and the |n> level.

7. The complete common-mode suppression two-component atom interferometer according to claim 3, characterized in that: The relative frequency relationship among the first Raman laser (106), the second Raman laser (108), the third Raman laser (109), and the fourth Raman laser (107) satisfies: ， ， ， When the laser serial number , It is The frequency of the Raman laser.

8. A gravity differential measurement method using the complete common-mode suppression two-component atom interferometer according to any one of claims 1 to 7, comprising the following steps: Step B1, building a two-component atom interferometer with complete common-mode suppression; Step B2: The cold atomic cluster (101) is cooled and trapped at the bottom of the vacuum system (102) by a cooling laser (104), and then thrown upward to form an atomic fountain; Step B3, realize Mach-Zehnder atomic interferometer by π / 2-π-π / 2 triple pulse, the cold atomic cluster (101) At the moment, the first π / 2 Raman pulse is applied to realize the beam splitting of one atom; after the free evolution time T, At the same time, a π Raman pulse is applied to realize the reflection of atoms in two paths; after a free evolution time T, The second π / 2 Raman pulse at the moment acts to combine the atomic paths and thus achieve atomic interference; Both π / 2 Raman pulses and π Raman pulses consist of four Raman laser beams and compensation light (113); Step B4, applying quenching light and detection laser (105) in sequence, and capturing interference fringes of atoms corresponding to the two components respectively through the fluorescence collection system (110) and the imaging CCD (111); Extract the interference phase of the atoms corresponding to the two components respectively; The phase difference is obtained by the difference in the interference phase of the atoms corresponding to the two components. ,according to Get the differential acceleration due to gravity , is the effective wave vector, T is the free evolution time, ， ， ， It is The wave vector of Raman laser corresponds to the laser serial number ; yes The effective wave vector of yes The effective wave vector.

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