CN106871888A - A kind of cold atom Bose Einstein condenses the method for detecting phases of vortex superposition state gyro - Google Patents

Abstract

The present invention relates to the method for detecting phases that a kind of cold atom Bose Einstein condenses vortex superposition state gyro.By the vortex light of superposition state inject Bose Einstein condensed state gas atom group in, so that Bose Einstein cohesion (BEC) atomic group obtains certain orbital angular momentum, the vortex superposition state matter wave of stabilization is produced, the BEC atomic groups in potential well are equivalent to a matter wave interference gyro.The atomic density distribution of BEC can form the interference pattern of stabilization, when system is rotated with certain angular speed, because Sagnac effects can produce certain phase, the scattering of each atom pair photon is fixed, after detection light is added, whole RESONANCE ABSORPTION image is detected by Charged Couple original paper (CCD), scattered light intensity is obtained by spatial operation and temporal calculation, calculate the Density Distribution of BEC atomic groups, and then obtain phase information, and can be subtracted each other by space obtain relative light intensity become be turned to gyro signal, for Estimation System angular speed, sensitivity to system angular speed is realized with this.

Description

A kind of phase-detection of cold atom Bose-Einstein condensation vortex superposition state gyro Method

Technical field

The present invention relates to a kind of method for detecting phases of cold atom Bose-Einstein condensation vortex superposition state gyro, can To be applied to exceed accuracy inertial navigation field.

Technical background

French physician JFoucault in 1850 is in order to study earth rotation, first turning in discovery high-speed rotation Due to effect of inertia, its rotary shaft points to a fixed direction to son forever, and is named as gyroscope.Gyroscope conduct Main inertial navigation testing equipment, has a wide range of applications in fields such as navigation, Aeronautics and Astronautics, guided missiles, and to a country The development of industry, national defence and other high-tech areas there is highly important strategic importance.Traditional electromechanical gyroscope by In the limitation of its mechanism of action, precision sensitivity enters bottleneck, lasergyro, fibre optic gyroscope based on Sagnac effects Precision sensitivity raising and gyroscope volume, there is contradiction between weight, power consumption, likewise entered accuracy and sensitivity Development bottleneck.

The fast development in quantum physics and low temperature physics field in recent years brings to the development of new quantum gyroscope Revolutionary impact, occurs in that a series of Quantum gyroscope of superhigh precision hypersensitivitys, which results in the prosperity such as America and Europe state The attention of family.Advanced project research administration of U.S. Department of Defense has formulated " Precision Inertial Navigation system " (PINS), will be with quantum effect For the quantum inertia sensing technology of core is considered as leading inertial technology of future generation.According to mechanism and motion mode, quantum gyroscope can It is divided into Quantum Spin gyro, quantum interference gyro and quantum microstructures gyro.Quantum Spin gyro has high accuracy with miniaturization Good characteristic, but inevitably there is friction between atom or between molecule and collide, influence and constrain its precision and Sensitivity.Quantum interference gyro has theoretical precision very high, has wide practical use, but there is volume and sensitivity essence Contradiction between degree.Nineteen ninety-five, the experiment of controlled Rb atoms low density gas Bose-Einstein condensation (BEC) is realized, indicated The realization of gas phase atom boson-einstein condensation state, you can realized to gaseous state by the Time Orbiting Potential (TOP) based on magneto-optic The imprison of alkali metal atom, the controllable internal gas atomic group of potential well produces vortex, gyroscopic inertia and precession with gyro.It is cold Atomic gas are pure, thin, and beneficial to detection, interaction is easy to description, and the vortex superposition state gyro based on gaseous state BEC can be realized The high density of vortex of quantum, is easy to miniaturization.

Need the artificial interference loop that builds different from existing interference gyro (such as optical gyroscope and intervening atom gyro), it is cold Atomic BEC vortex superposition state gyro by from into vortex light manipulate loop and instead of the interference loop of structure, this is not only helped In the noise for significantly reducing the introduction of interference loop, and for the high precision test of interference gyro provides possibility.

Detection method on interference gyro, existing optical gyroscope and intervening atom gyro are a certain interference points of detection The phase information at place.For cold atom BEC vortex superposition state tops, if along in this way, will inevitably lose Whole interference pattern information, so as to influence the accuracy of detection of system.

The present invention realizes the sensitivity to angular speed using the Sagnac effects of vortex superposition state matter wave, detects interference pattern Phase information so as to obtain the phase difference of accumulation in the angular speed of system, time t be with detection time, platform angular speed and The topological charge number of vortex is proportional, is fixed for the scattering of photon due to each atom, after detection light is added, passes through Charged Couple original paper (CCD) detection scattered photon distribution, you can the Density Distribution of BEC atomic groups is obtained, so that using light intensity point Cloth obtains phase delta phi, Estimation System angular speed.The whole interference pattern of detection causes scattered photon number N_scGreatly increase, and The time of the carrying out cumulative sensitivity sensitive to improve angular speed.

The content of the invention

Technology solve problem of the invention is：Cold atom BEC is directly applied to for by existing interference gyro detection method Deficiency on vortex superposition state gyro, it is proposed that a kind of utilization space computing and temporal calculation detect the whole interference pattern of gyro Phase information method, greatly improves sensitive sensitivity and the precision of system.

Technical solution of the invention is：

(1) in the vortex light of superposition state being injected into BEC gas atoms group so that BEC atomic groups obtain certain track angle Momentum, produces the vortex superposition state matter wave of stabilization, and the BEC atomic groups in potential well are equivalent to a matter wave interference gyro. The atomic density distribution of BEC can form the interference pattern of stabilization, when system is rotated with certain angular speed, due to Sagnac effects Certain phase can be produced, the scattering of each atom pair photon is fixed, after detection light is added, detect whole by CCD RESONANCE ABSORPTION image, scattered light intensity is obtained by spatial operation and temporal calculation, calculates the Density Distribution of BEC atomic groups, and then obtain To phase information, and can be subtracted each other by space and obtain relative light intensity and become to be turned to gyro signal, for Estimation System angular speed, with This realizes the sensitivity to system angular speed.

(2) utilization space computing and temporal calculation obtain scattered light intensity distribution, calculate the distribution of BEC atomic densities, Jin Erji The method of calculation system angular speed.The sensitivity to angular speed is realized using the Sagnac effects of vortex superposition state matter wave, detection is dry The phase information of pattern is related to so as to obtain the angular speed of system；To interference pattern petal along θ=2m π/4l (m=0,1 ... 4l- 1) it is divided into 4l region Γ_k(k=1,2 ..., 4l), defines I₀It is total light intensity, I₁It is 2l region Γ_k(k=1,3 ..., 4l- 1) total light intensity, I₂It is 2l region Γ_kThe total light intensity of (k=2,4 ..., 4l), the I in experimentation₁And I₂It is tired by the time Plus (1) and space cumulative (2) obtains：

When potential well is rotated, light intensity I is can obtain₁And I₂：

Density Distribution (z=z in BEC cross sections in potential well₀) it is proportional to light distribution：

I(r,θ,z)∝Σ_Ω(r, θ, t)={ 1+cos [2l θ+Δ φ] } | Ψ (r, θ, z) |² (10)

Δ φ can be obtained by BEC cross sections Density Distribution, it is to subtract each other the relative light intensity change for obtaining by space to define δ：

Obtain δ and can be used for Estimation System angular speed：

Because each atom is fixed for the scattering of photon, after detection light is added, RESONANCE ABSORPTION is detected by CCD Image, carries out that the time is cumulative and space is cumulative obtains phase information, and can be subtracted each other by space and obtain δ, for Estimation System angle Speed, detects that whole interference pattern causes scattered photon number N_scGreatly increase, improves sensitivity.

Principle of the invention is：

(1) BEC based on " mexican hat " potential well is vortexed and is superimposed interference technique

For cold atom BEC, after vortex light or other modes obtain certain orbital angular momentum, can be produced in BEC It is raw to be vortexed.When orbital angular momentum exceedes certain limitation, vortex can automatically split into multiple vortexs.In order that BEC vortexs can The orbital angular momentum of acquisition is bigger, utilizes " mexican hat " potential well to capture atomic group, rolls into a ball BEC gas atoms and circlewise divides Cloth, with the automatic division for avoiding being vortexed.So as to form the vortex of bigger orbital angular momentum, and stabilization is kept for the longer time.

" mexican hat " potential well is formed using two beam laser.First with the laser of a branch of red off resonance, by one Cylindrical anamorph forms gesture into " pie " potential well, then by a branch of superfine blue off resonance laser in the center of " pie " potential well Build, so as to form " mexican hat " potential well.As shown in Fig. 2 because its shape is gained the name like mexican hat.By " Mexico Cap " potential well, it is possible to obtain the ring-type Density Distribution of BEC gas atoms group.

(2) STIRAP (Stimulated Raman Adiabatic Passage) excited Raman adiabatic process

Injected during color of wave-einstein condensation state gas atom rolls into a ball using superposition state vortex light, can in BEC generation Matter ripple is superimposed vortex state.The vortex light of superposition state is mainly an excited Raman thermal insulation mistake with the effect of gas atom group in BEC Journey, i.e. STIRAP.Its mechanism is as shown in Figure 3.

The initial irrotationality state of BEC atoms is | 0>, | l>With |-l>Superposition state vortex light inject BEC atomic groups after, atom Group forms two Raman Process, i.e. (Ω in Fig. 3 by external field₊,Ω_c) and (Ω-, Ω_c), Ω_±It is the frequency of Rabbe's test Rate, can finally form |+>With |->Two vortex state superpositions.By the parameter for adjusting superposition state vortex light and external source light so that several All particles are rested on |+>With |-<State, so as to form the matter wave vortex superposition state of stabilization.

(3) angular speed of vortex superposition state is sensitive and detects

Vortex superposition state gyro based on cold atom BEC be realized using the Sagnac effects of vortex superposition state matter wave it is right The sensitivity of angular speed.Therefore, after the interference pattern for producing stabilization, the phase information of interference pattern need to be detected so as to obtain system Angular speed.

Transmitted by the orbital angular momentum of superposition state vortex light, the material of the vortex superposition state of stabilization can be formed in BEC Ripple, produces the standing wave of stabilization.Standing wave is embodied in the Density Distribution of cold atom, and as the Density Distribution of cold atom is in " petal " shape Distribution.

4l region Γ is divided into along θ=2m π/4l (m=0,1 ... 4l-1) to interference pattern petal_k(k=1,2 ..., L4) by taking l=3 as an example, division methods such as Fig. 4.Define I₀It is total light intensity, I₁It is 2l region Γ_k(k=1,3 ..., l4-1's Total light intensity, I₂It is 2l region Γ_kThe total light intensity of (k=2,4 ..., 4l).

The I in experimentation₁And I₂It is cumulative by the timeIt is cumulative with spaceObtain.

Superposition state vortex wave function：

Wherein l is vortex topological charge number, and θ is initial phase, and r and z is wave function location parameter.

Therefore light intensity can be expressed as：I (r, θ, z)=[1+cos (2l θ)] F (r, z), wherein

In z=z₀The total light intensity I at place₀Meet：

Initial time, in the case where potential well is not rotated, has：

Light intensity I can equally be obtained₂,

When potential well is rotated, superposition state vortex wave function：

Wherein Δ φ is Sagnac phases.

The Sagnac phase delta phis of vortex light=2l Ω t, wherein l is the orbital angular momentum amount of vortex light in general theory of relativity Subnumber, t is coherence time, and Ω is potential well turning rate.

Its light distribution is：I (r, θ, z)=[1+cos (2l θ+Δ φ)] F (r, z)

Light intensity I₁：

Also due to total light intensity is constant, light intensity I₂：

Density Distribution (z=z in BEC cross sections in potential well₀) it is proportional to light distribution：

I(r,θ,z)∝Σ_Ω(r, θ, t)={ 1+cos [2l θ+Δ φ] } | Ψ (r, θ, z) |² (18)

Δ φ can be obtained by BEC cross sections Density Distribution, it is to subtract each other the relative light intensity change for obtaining by space to define δ：Can obtainSo as to δ can be used for Estimation System angular speed.

Because each atom is fixed for the scattering of photon, after detection light is added, RESONANCE ABSORPTION is detected by CCD Image, carries out that the time is cumulative and space is cumulative obtains phase, and can be subtracted each other by space and obtain δ, used as system angular speed.Detection Whole interference pattern causes scattered photon number N_scGreatly increase, improves sensitivity.

Compared with existing scheme, major advantage is the solution of the present invention：

(1) simple structure, without complicated light path and various sensing and plant equipment；Quality is small, and device therefor is less And quality is all smaller；Small volume, the development with technology can accomplish chip-scale, and the environment and condition that can be applicable are wider；

(2) time delay that direct fitted figure picture is present is efficiently solved, is cold atom with the potentiality for realizing real-time detection The phase information detection of BEC vortex superposition state gyros provides great convenience；

(3) high precision and tool have greater room for improvement, by volume, the high accuracy of this programme is mainly derived from detection process In to the spatial operation and temporal calculation of whole interference pattern so that scattered photon number greatly increases, and improves angular speed quick The sensitivity of sense, and as the precision of development this programme of technology will obtain bigger lifting；On the other hand, due to structure Simply, error source greatly reduces, and more conventional scheme has great advantage.

Brief description of the drawings

Fig. 1 is method for detecting phases schematic diagram；

Fig. 2 is " mexican hat " potential well schematic diagram；

Fig. 3 is that STIRAP (excited Raman adiabatic process) acts on schematic diagram；

Fig. 4 is interference pattern simulation drawing division methods；

Fig. 5 is BEC vortex superposition state gyroscope structure figures；

Fig. 6 is absorption imaging system structure chart.

Wherein：1 is the light beam with orbital angular momentum；2 is beam expanding lens；3 is 45 ° of total reflective mirrors of 1064nm；4 is band image The computer of capture card；5 is BEC generation devices；6 is 100 times of large-numerical aperture oil immersion objectives；7 is 45 ° of high reflective mirrors of 1064nm； 8 is optical filter；9 is ccd video camera；10 is cooling laser；11 is detection light；12 is polarization beam splitter prism；13 is λ/4 wave plate； 14 is ultrahigh vacuum glass chamber (BEC vortex superposition states gyro)；15 is λ/4 wave plate；16 is cooling laser；17 is polarization beam splitting rib Mirror；18 is ccd video camera.

Specific embodiment

Objective for implementation of the invention is the vortex superposition state gyro based on cold atom BEC, and specific embodiment schematic diagram is such as Shown in Fig. 1, specific implementation step is as follows：

Vortex superposition state gyro (such as Fig. 5) based on cold atom BEC is imitated using the Sagnac of vortex superposition state matter wave The sensitivity to angular speed should be realized.Therefore, after the interference pattern for producing stabilization, need to detect the phase information of interference pattern so as to Obtain the angular speed of system.

Transmitted by the orbital angular momentum of superposition state vortex light, the material of the vortex superposition state of stabilization can be formed in BEC Ripple, produces the standing wave of stabilization.Standing wave is embodied in the Density Distribution of cold atom, and as the Density Distribution of cold atom is in " petal " shape Distribution.Because each atom is fixed for the scattering of photon, after detection light is added, is detected by ccd video camera and resonated Absorption image (detection means such as Fig. 6), carries out that the time is cumulative and space is cumulative obtains phase, and can be subtracted each other by space and obtain δ, As system angular speed.The whole interference pattern of detection causes scattered photon number N_scGreatly increase, improves sensitivity.

4l region Γ is divided into along θ=2m π/4l (m=0,1 ... 4l-1) to interference pattern petal_k(k=1,2 ..., L4) by taking l=3 as an example, division methods such as Fig. 4.Define I₀It is total light intensity, I₁It is 2l region Γ_k(k=1,3 ..., l4-1's Total light intensity, I₂It is 2l region Γ_kThe total light intensity of (k=2,4 ..., 4l).

The I in experimentation₁And I₂It is cumulative by the timeIt is cumulative with spaceObtain.

Superposition state vortex wave function：

Wherein l is vortex topological charge number, and θ is initial phase, and r and z is wave function location parameter.

Therefore light intensity can be expressed as：

I (r, θ, z)=[1+cos (2l θ)] F (r, z) (20)

Wherein

In z=z₀The total light intensity I at place₀Meet：

Initial time, in the case where potential well is not rotated, has：

Light intensity I can equally be obtained₂,

When potential well is rotated, superposition state vortex wave function：

Wherein Δ φ is Sagnac phases.

The Sagnac phase delta phis of vortex light=2l Ω t, wherein l is the orbital angular momentum amount of vortex light in general theory of relativity Subnumber, t is coherence time, and Ω is potential well turning rate.

Its light distribution is：

I (r, θ, z)=[1+cos (2l θ+Δ φ)] F (r, z) (25)

Light intensity I₁：

Also due to total light intensity is constant, light intensity I₂：

Density Distribution (z=z in BEC cross sections in potential well₀) it is proportional to light distribution：

I(r,θ,z)∝Σ_Ω(r, θ, t)={ 1+cos [2l θ+Δ φ] } | Ψ (r, θ, z) |² (28)

Δ φ can be obtained by BEC cross sections Density Distribution, it is to subtract each other the relative light intensity change for obtaining by space to define δ：

Can obtain：

So as to δ can be used for Estimation System angular speed.

The above is only the preferred embodiment of the present invention, it is noted that for the ordinary skill people of the art For member, some improvement can also be made under the premise without departing from the principles of the invention, these improvement also should be regarded as of the invention Protection domain.The content not being described in detail in present specification belongs to prior art known to professional and technical personnel in the field.

Claims (2)

1. the present invention relates to a kind of method for detecting phases of cold atom Bose-Einstein condensation vortex superposition state gyro, will be folded Plus during the vortex light of state injects Bose-Einstein condensation (BEC) gas atom group so that BEC atomic groups obtain certain rail Road angular momentum, produces the vortex superposition state matter wave of stabilization, and the BEC atomic groups in potential well are equivalent to a matter wave interference top Spiral shell；The atomic density distribution of BEC can form the interference pattern of stabilization, when system is rotated with certain angular speed, due to Sagnac Effect can produce certain phase, and the scattering of each atom pair photon is fixed, after detection light is added, by Charged Couple Original paper (CCD) detects whole RESONANCE ABSORPTION image, and scattered light intensity is obtained by spatial operation and temporal calculation, calculates BEC atomic groups Density Distribution, and then obtain phase information, and can subtract each other by space and obtain relative light intensity and become to be turned to gyro signal, be used for Estimation System angular speed, the sensitivity to system angular speed is realized with this.

2. a kind of method for detecting phases of cold atom BEC vortexs superposition state gyro according to claim 1, proposes using empty Between computing and temporal calculation obtain scattered light intensity distribution, calculate the distribution of BEC atomic densities, so computing system angular speed side Method, it is characterised in that：The sensitivity to angular speed is realized using the Sagnac effects of vortex superposition state matter wave, interference pattern is detected Phase information so as to obtain the angular speed of system；Interference pattern petal is divided into along θ=2m π/4l (m=0,1 ... 4l-1) 4l region Γ_k(k=1,2 .l.., 4 determine) and justice I₀It is total light intensity, I₁It is 2l region Γ_k(k=1,3's ..., l4-1) is total Light intensity, I₂It is 2l region Γ_kThe total light intensity of (k=2,4 ..., 4l), the I in experimentation₁And I₂(1) is added up by the time Obtained with space cumulative (2)：

$\begin{array}{cc}{I}_{k1}={\mathrm{\&Sigma;}}_{t=0}^T{I}_{k1}\left(t\right)& I_{k2}={\mathrm{\&Sigma;}}_{t=0}^T{I}_{k2}\left(t\right)\end{array}---\left(1\right)$

$\begin{array}{cc}{I}_1={\mathrm{\&Sigma;}}_{k=1}^{2l}{I}_{k1}& I_2={\mathrm{\&Sigma;}}_{k=1}^{2l}{I}_{k2}\end{array}---\left(2\right)$

When potential well is rotated, light intensity I is can obtain₁And I₂：

$\begin{array}{c}{I}_1=I_0(\frac{1}{2}+\frac{1}{\mathrm{\&pi;}}sin\mathrm{\&Delta;}\mathrm{\&phi;})\\ I_2=I_0(\frac{1}{2}-\frac{1}{\mathrm{\&pi;}}sin\mathrm{\&Delta;}\mathrm{\&phi;})\end{array}---\left(3\right)$

Density Distribution (z=z in BEC cross sections in potential well₀) it is proportional to light distribution：

I(r,θ,z)∝Σ_Ω(r, θ, t)={ 1+cos [2l θ+Δ φ] } | Ψ (r, θ, z) |² (4)

Δ φ can be obtained by BEC cross sections Density Distribution, it is to subtract each other the relative light intensity change for obtaining by space to define δ：

$\mathrm{\&delta;}=\frac{I_1-I_2}{I_1+I_2}---\left(5\right)$

Obtain δ and can be used for Estimation System angular speed：

$\mathrm{\&delta;}=\frac{2}{\mathrm{\&pi;}}sin\mathrm{\&Delta;}\mathrm{\&phi;}=\frac{2}{\mathrm{\&pi;}}sin\left(2l\mathrm{\&Omega;}t\right)\&ap;\frac{4l\mathrm{\&Omega;}t}{\mathrm{\&pi;}}---\left(6\right)$

Because each atom is fixed for the scattering of photon, after detection light is added, RESONANCE ABSORPTION figure is detected by CCD Picture, carries out that the time is cumulative and space is cumulative obtains phase information, and can be subtracted each other by space and obtain δ, for Estimation System angle speed Rate, detects that whole interference pattern causes scattered photon number N_scGreatly increase, improves sensitivity.