Ultra-cold atom differential interference gyroscope based on time orbit potential well

Abstract

The invention discloses an ultra-cold atom differential interference gyroscope based on a time orbit potential well, and belongs to the field of ultra-cold atom and angular velocity measurement. The device comprises an optical platform, a cooling laser light source, a light trap light source, a Bragg pulse light source, a vacuum cavity, an arbitrary wave generator, a signal generator and six magnetic field coils. The vacuum cavity is positioned above the optical platform; the six magnetic field coils are located around the vacuum cavity and used for generating an alternating-current magnetic field. The signal generator is used for providing alternating current for the magnetic field coil; the cooling light is in three orthogonal directions, and two beams of opposite light are arranged in each direction; the Bragg pulse light is one-dimensional standing wave light; the light trap light and the Bragg pulsed light are two beams of orthogonal light, and the light beam directions of the light trap light and the Bragg pulsed light coincide; the arbitrary wave generator is used for generating a pulse time sequence of the pulsed light. According to the invention, ultra-cold atoms with lower temperature are utilized, so that a larger interference area and higher angular velocity sensitivity can be realized in a smaller volume, and the sensor is suitable for a moving carrier.

Description

Technical Field

[0001] The invention relates to an ultracold atom differential interferometer gyroscope based on a time orbit potential well, and belongs to the field of ultracold atom and angular velocity measurement. Background Art

[0002] In addition to rotor gyroscopes, optical gyroscopes, and vibrating gyroscopes, the angular velocity measurement system based on the principle of atomic interference is the focus of research in this direction. The angular velocity measurement in atomic interference mainly uses Sagnac interferometry. This method manipulates the splitting of atomic wave packets, passes through two paths surrounding an area, and then recombine. The interference signal generated depends on the rotation rate of the system and the area of ​​the area surrounded by the path. Although the optical Sagnac interferometer is an important component of angular velocity measurement today, its sensitivity and stability are limited. Up-throw, opposite-throw, and continuous beam atom interferometers are inherently more sensitive and exhibit superior gyroscope performance. But their benefits are not enough to offset the substantial increase in the size and complexity of the equipment required for the atomic system. These problems can be overcome using atoms confined in a guide potential or potential well, as opposed to atoms falling into free space. Potential wells can support atoms against gravity, so long measurement times can be achieved without requiring a large falling distance. Potential wells can also control the trajectory of atoms so that they form a closed interference loop, providing a large closed area for a given linear dimension, which is suitable for measurement on a moving carrier. In addition, the temperature of cold atoms used in traditional atomic interferometers is on the order of 10 microkelvins. The lower the temperature, the higher the measurement accuracy. This patent proposes the use of Bose-Einstein condensates, which can reach below 100 nanokelvins, with lower temperatures and higher coherence times, which can further improve measurement accuracy. Summary of the invention

[0003] In order to solve the problem that the equipment size and complexity required by the prior art cannot be taken into account together with the angular velocity measurement accuracy, the purpose of the present invention is to provide an ultracold atom interferometer based on a time-orbit potential well, which utilizes ultracold atoms with lower temperatures, has a longer coherence time than cold atoms, and has a higher sensitivity. It can achieve a larger interference area and higher angular velocity sensitivity in a smaller volume, and is suitable for moving carriers.

[0004] The objective of the present invention is achieved through the following technical solutions:

[0005] The ultracold atom differential interferometer gyroscope based on time orbit potential well disclosed by the present invention comprises an optical platform, a cooling laser light source, a light trap light source, a Bragg pulse light source, a vacuum cavity, an arbitrary wave generator, a signal generator and 6 magnetic field coils.

[0006] The vacuum cavity is located on the optical platform; 6 magnetic field coils are located around the vacuum cavity and are used to generate an AC magnetic field; a signal generator is used to provide an AC current to the magnetic field coil; a cooling laser light source, a light trap light source, and a Bragg pulse light source are used to generate cooling light, light trap light, and Bragg pulse light, respectively; the cooling light is in three orthogonal directions, and each direction has two beams of opposite light; the Bragg pulse light is a one-dimensional standing wave light; the light trap light and the Bragg pulse light are both two beams of orthogonal light, and the beam directions of the light trap light and the Bragg pulse light coincide; an arbitrary wave generator is used to generate a pulse timing of the pulse light.

[0007] The method for realizing angular velocity measurement by using the ultracold atomic differential interferometer gyroscope comprises the following steps:

[0008] Step 1: Use cooling light to preliminarily cool the atoms to obtain optical clumps, and then use light traps to perform evaporative cooling to obtain ultracold atoms;

[0009] Step 2: Slowly reduce the light intensity of the light trap to adiabatically load the ultracold atoms into the time orbit potential well;

[0010] Step 3: Use orthogonal Bragg pulses to act on the ultracold atoms twice to divide them into four atomic clusters, so that each atomic cluster moves in a circular motion in the time orbit potential well; when the atomic clusters overlap, apply the third Bragg pulse, which has the same direction and timing as the second pulse, to obtain the interference result;

[0011] Step 4: Finally, use the absorption imaging method to obtain the atomic density distribution information and calculate the interference result S Δ and Repeat steps 1 to 3 10 times to obtain 10 sets of interference results S Δ and Finally, the Sagnac phase Φ was obtained by ellipse fitting using 10 sets of interference results. s , and then the system angular velocity Ω is obtained:

[0012]

[0013] Where, Ω is the angular velocity of the system; A is the area of ​​the Sagnac interference path, m is the atomic mass, is the reduced Planck constant, k 0 is the pulse light lattice wave vector, ω 0 is the resonator well frequency.

[0014] Specific implementation method of step three:

[0015] A. Use cooling light to obtain cold atoms, then load the cold atoms into a light trap, and then perform evaporative cooling to obtain ultracold atoms;

[0016] The light intensity is then linearly reduced through the light trap, and the ultracold atoms are adiabatically transferred to the center of the time orbit potential well.

[0017] B. At t = 0, The Bragg pulse is applied to the ultracold atoms in the direction of ±v B The two groups, along Direction is simple harmonic motion, speed where k 0 is the Bragg pulse light lattice laser wave vector, is the reduced Planck constant, and n is a positive integer representing the number of recoil kinetic forces applied to the atom by the Bragg pulse.

[0018] C. At t = π / (2ω 0 ) moment, the two groups of ultracold atoms move to the maximum displacement of simple harmonic oscillation. Bragg pulses are applied to two groups of ultracold atoms in the direction of It is also divided into two groups in terms of direction.

[0019] D. There are four atomic groups at this time. The two groups of ultracold atoms on the top interfere with each other, and the two groups of ultracold atoms on the bottom interfere with each other. The two groups of atoms on the top represent The quantum state generated by the Bragg pulse in the direction +|v B ,Δ> and -|v B , Δ>, respectively, moving in a counterclockwise and clockwise direction. The following two groups of atoms represent Quantum states generated by directional Bragg pulses and Make circular motions in clockwise and counterclockwise directions respectively;

[0020] E. At t = 2π / ω 0 At this moment, the four groups of atoms return to their initial positions after one movement. The third Bragg pulse is applied to obtain the interference results S of the ratio of the upper and lower zero-state atoms. Δ and Repeat the above steps 10 times to obtain 10 sets of interference results, and then use ellipse fitting to obtain the Sagnac phase Φ s , calculate the system angular velocity according to step 4.

[0021] Specific implementation method of step 4:

[0022] A. Due to the Sagnac effect, after the two groups of atoms move in opposite directions for one circle, the phase difference between the two groups of atoms will add a Sagnac phase:

[0023]

[0024] in, is the reduced Planck constant, ΔL is the angular momentum difference of the quantum state, Ω is the angular velocity vector of the system, m is the mass of the ultracold atom, Ω is the angular velocity of the system in the direction of rotation, and the loop area of ​​the atomic wave packet motion A=πR 2 , R is the radius of the circular interference loop. The phase difference between the two groups of atoms below will add the Sagnac phase -Φ s ; Due to system noise, the interference phase in the upper and lower interference processes will produce a certain deviation Φ′, so the phase of the two groups of atoms above Φ Δ And the phase of the two atoms below They are:

[0025] Φ Δ =Φ s +Φ′

[0026]

[0027] Perform differential processing to obtain the differential phase δΦ:

[0028]

[0029] B. After the third Bragg pulse, the interference result S is obtained Δ and The upper part of the atom will have S Δ =cos 2 (Φ Δ / 2) is transferred to a quantum state with zero momentum, and the lower part of the atoms will have The ratio of is transferred to a quantum state with zero momentum, through the formula Changes to Repeat the measurement 10 times, combine the measurement results, and fit S Δ , About Φ s , Φ Δ Ellipse parameter equation, get Sagnac phase Φ s , and then through the formula Calculate the system angular velocity.

[0030] Beneficial effects:

[0031] 1. The ultracold atom differential interferometer gyroscope based on time orbit potential well disclosed by the present invention utilizes ultracold atoms with lower temperature to replace cold atoms. Compared with the interferometer realized by cold atoms, the coherence time of ultracold atoms is longer, which is conducive to achieving longer interference and thus achieving a larger interference area, which is conducive to improving the accuracy of angular velocity measurement.

[0032] 2. The ultracold atom differential interferometer gyroscope based on time orbit potential well disclosed by the present invention adopts the method of differentiating two sets of ultracold atom interferometers to achieve common-mode suppression of the phase noise that masks the rotation signal, improve the signal-to-noise ratio, and further improve the accuracy of angular velocity signal extraction.

[0033] 3. The ultracold atom differential interferometer gyroscope based on the time orbit potential well disclosed by the present invention uses the time orbit potential well to control the trajectory of the ultracold atoms to form a closed interference loop, which significantly reduces the difficulty of calibrating the peripheral carrier plane perpendicular to gravity.

[0034] 4. The ultracold atom differential interferometer gyroscope based on time orbit potential well disclosed by the present invention adopts the method of confining ultracold atoms in potential well. Compared with the traditional upward-throwing cold atom interferometer gyroscope, this method can achieve a larger interference area and higher angular velocity sensitivity in a smaller volume.

[0035] 5. The traditional upward-throwing cold atom gyroscope cannot detect normally on a moving carrier, because during the movement, the atoms will hit the vacuum wall, the interference process will be destroyed, and there will be no measurement results. The ultracold atom differential interferometer gyroscope based on the time orbit potential well disclosed by the present invention will perform the interference process in the potential field, and the measurement process will not be affected by the movement of the carrier, so it can be used on a moving carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a composition diagram of the ultracold atom differential interferometer gyroscope based on time orbit potential well disclosed in the present invention;

[0037] Figure 2 The present invention discloses a flow chart of an ultracold atom differential interferometer gyroscope based on a time-orbit potential well.

[0038] Figure 3 Schematic diagram of the atomic interference process.

[0039] Among them: 1-optical platform, 2-cooling laser light source, 3-light trap light source, 4-Bragg pulse light source, 5-vacuum cavity, 6-arbitrary wave generator, 7-signal generator, 8-magnetic field coil. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose and advantages of the present invention, the invention is further described below with reference to the accompanying drawings and examples.

[0041] Embodiment 1:

[0042] like Figure 1As shown, the ultracold atom differential interferometer gyroscope based on the time orbit potential well disclosed in this embodiment is mainly composed of an optical platform 1, a cooling laser light source 2, a light trap light source 3, a Bragg pulse light source 4, a vacuum cavity 5, an arbitrary wave generator 6, a signal generator 7, and a magnetic field coil 8. Among them, the six magnetic field coils 8 are located around the vacuum cavity 5, and are used to generate an alternating magnetic field to form a time orbit potential well; the signal generator 7 is used to provide an alternating current to the magnetic field coil 8; the cooling laser light source 2, the light trap light source 3, and the Bragg pulse light source 4 are used to generate cooling light, light trap light, and Bragg pulse light respectively; the arbitrary wave generator 7 is used to generate a pulse sequence for the Bragg pulse light source; these are all located on the optical platform 1.

[0043] like Figure 2 As shown, the method for realizing angular velocity measurement by the ultracold atom differential interferometer gyroscope based on the time orbit potential well disclosed in this embodiment is: first, the cooling light generated by the cooling laser light source 2 is used to preliminarily cool the atoms to obtain cold atoms, and then the ultracold atoms with a temperature lower than 100nK are obtained by evaporative cooling through the orthogonal light trap generated by the light trap light source 3, and then the light trap light intensity is slowly reduced, and the ultracold atoms are adiabatically loaded into the time orbit potential well. Then, the arbitrary wave generator 6 is used to generate a pulse signal to the Bragg pulse light source 4 to realize the application of the first Bragg pulse to the ultracold atoms. Under the action of the pulse, the ultracold atoms will be divided into two atomic groups with equal number of atoms and opposite speeds until the speed of the atomic group is consumed to zero by the potential well. At this time, the atoms will be separated by a distance. At this time, the arbitrary wave generator 6 generates a second pulse signal to the Bragg pulse light source 4, and each ultracold atom will be divided into two atomic groups with equal number of atoms and opposite speeds, that is, there are a total of four atomic groups. Due to the action of the time orbit potential well, the four atomic groups will move in a circle. At this time, the relative phase of the signal generator 7 controls the magnetic field coil 8 to close the motion trajectory of the four groups of atoms. After the atomic group moves for one circle, the arbitrary wave generator 6 generates a pulse signal to the Bragg pulse light source 4 to generate the third Bragg pulse, and the interference result is obtained: the ratio of the upper and lower zero-state atoms S Δ and Finally, the phase information is obtained through the interference result and the angular velocity is calculated. Figure 3 As shown, the angular velocity of the system to be measured is Ω.

[0044] The method for realizing angular velocity measurement by ultracold atomic differential interferometer gyroscope based on time orbit potential well disclosed in this embodiment has the following specific implementation steps:

[0045] A. First, use the cooling laser light source 2 to generate cooling light to obtain cold atoms, then use the light trap light source 3 to load the atoms into the light trap, and then use the light trap to perform evaporative cooling to obtain ultracold atoms, and finally transfer the ultracold atoms adiabatically to the center of the time orbit potential well, as shown in Figure 3 As shown in a.

[0046] B. Use the arbitrary wave generator 6 to generate a pulse signal to the Bragg pulse light source 4 to achieve The Bragg pulse is applied to the atoms in the direction of ±v B The two groups, along Direction is simple harmonic motion, speed where k 0 is the Bragg pulse light lattice laser wave vector, is the reduced Planck constant; n is a positive integer, representing the number of recoil motive forces applied to the atom by the Bragg pulse. The trajectory motion equation y(t) of the ultracold atom in the direction is

[0047] y(t)=±Rsin(ω 0 t),

[0048] The rotation interference radius R = v B / ω 0 ,ω 0 is the well frequency.

[0049] C. At t = π / (2ω 0 ), the two groups of atoms move to the maximum displacement of simple harmonic oscillation. At this time, the arbitrary wave generator 6 generates a pulse signal to the Bragg pulse light source 4 to achieve If Bragg pulses are applied to two groups of atoms simultaneously, the atoms will It is also divided into two groups in terms of direction.

[0050] D. There are four groups of atoms in total, of which the top two groups (in Figure 3 d is indicated by "Δ" The quantum state generated by the Bragg pulse in the direction +|v B , Δ> (grey in the figure) and -|v B , Δ> (white in the figure), respectively, in counterclockwise and clockwise circular motion, the trajectory motion equation is y(t) = R cos(ω 0 t) and x(t) = ±R sin(ω 0 t). For the following two groups of atoms exist Figure 3 D Mark), and make circular motion in clockwise and counterclockwise directions respectively.

[0051] E. At t = 2π / ω 0 At this moment, the four atoms return to their initial positions (x = 0, y = ±R, as Figure 3 e). Using the arbitrary wave generator 6 to generate a pulse signal to the Bragg pulse light source 4, the third The Bragg pulse in the direction acts on the ultracold atoms, and the upper part of the atoms will have S Δ =cos 2 (Φ Δ / 2) is transferred to a quantum state with zero momentum, and the same is true for the lower atoms. And expressed as

[0052] F. Interference results S Δ and The parametric equation of the ellipse is formed, and it is related to Φ Δ , Φ s Finally, the atomic density distribution information is obtained by using the absorption imaging method, and the interference result S is calculated. Δ and The measurement was repeated 10 times. Using 10 sets of interference data, the Sagnac phase Φ was obtained by ellipse fitting. s , and the system angular velocity Ω is calculated by the following formula.

[0053]

[0054] Where A is the Sagnac interference path area, m is the atomic mass, is the reduced Planck constant, k 0 is the pulse light lattice wave vector, ω 0 is the trap frequency, and n is the number of recoil momentum applied to the atoms by the Bragg pulse. From the above formula, it can be seen that in order to improve the angular velocity sensitivity of the system, by applying a higher order n recoil momentum pulse and a lower trap frequency ω 0 This method is different from the method of increasing the sensitivity of the gyroscope by increasing the falling time of atoms and increasing the height of the device. This method can be used to improve the sensitivity in a limited space and is not restricted in the moving carrier.

[0055] The specific description above further illustrates the purpose, technical solutions and beneficial effects of the invention in detail. It should be understood that the above is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. Ultracold atomic differential interferometer gyroscope based on time orbit potential well, characterized by: It includes an optical platform, a cooling laser light source, a light trap light source, a Bragg pulse light source, a vacuum cavity, an arbitrary wave generator, a signal generator and 6 magnetic field coils; The vacuum cavity is located on the optical platform; 6 magnetic field coils are located around the vacuum cavity and are used to generate an AC magnetic field; a signal generator is used to provide an AC current to the magnetic field coil; a cooling laser light source, a light trap light source, and a Bragg pulse light source are used to generate cooling light, light trap light, and Bragg pulse light, respectively; the cooling light is in three orthogonal directions, with two beams of opposite light in each direction; the Bragg pulse light is a one-dimensional standing wave light; the light trap light and the Bragg pulse light are both two orthogonal beams, and the beam directions of the light trap light and the Bragg pulse light coincide; an arbitrary wave generator is used to generate a pulse timing of the pulse light.

2. A method for measuring angular velocity using the ultracold atomic differential interferometer gyroscope as claimed in claim 1, characterized in that: The following steps are included: Step 1: Use cooling light to preliminarily cool the atoms to obtain optical clumps, and then use light traps to perform evaporative cooling to obtain ultracold atoms; Step 2: Slowly reduce the light intensity of the light trap to adiabatically load the ultracold atoms into the time orbit potential well; Step 3: Use orthogonal Bragg pulses to act on the ultracold atoms twice to divide them into four atomic clusters, so that each atomic cluster moves in a circular motion in the time orbit potential well; when the atomic clusters overlap, apply the third Bragg pulse, which has the same direction and timing as the second pulse, to obtain the interference result; Step 4: Use the absorption imaging method to process the interference results to obtain atomic density distribution information. Repeat steps 1 to 3 10 times to obtain 10 sets of processed interference results. Use the 10 sets of interference results to perform ellipse fitting to obtain the Sagnac phase Φ s , and then get the system angular velocity Ω: Where, Ω is the angular velocity of the system; A is the area of ​​the Sagnac interference path, m is the atomic mass, is the reduced Planck constant, k0 is the pulse light lattice wave vector, and ω0 is the resonator well frequency.

3. The method according to claim 2, characterized in that: Specific implementation method of step three: A. Use cooling light to obtain cold atoms, then load the cold atoms into a light trap, and then perform evaporative cooling to obtain ultracold atoms; Then, the light intensity is linearly reduced through the light trap, and the ultracold atoms are adiabatically transferred to the center of the time orbit potential well; B. At t = 0, The Bragg pulse is applied to the ultracold atoms in the direction of ±v B The two groups, along Direction is simple harmonic motion, speed Where k0 is the Bragg pulse light lattice laser wave vector, is the reduced Planck constant, n is a positive integer, representing the number of recoil kinetic forces applied to the atom by the Bragg pulse; C. At t = π / (2ω0), the two groups of ultracold atoms move to the maximum displacement of simple harmonic oscillation respectively; at this time Bragg pulses are applied to two groups of ultracold atoms in the direction of In terms of direction, it is also divided into two groups; D. There are four atomic groups at this time; the two groups of ultracold atoms on the top interfere with each other, and the two groups of ultracold atoms on the bottom interfere with each other; the two groups of atoms on the top represent The quantum state generated by the Bragg pulse in the direction +|v B ,Δ> and -|v B , Δ>, respectively, moving in a counterclockwise and clockwise direction; the following two groups of atoms represent Quantum states generated by directional Bragg pulses and Make circular motions in clockwise and counterclockwise directions respectively; E. At t = 2π / ω0, the four groups of atoms return to their initial positions after one movement. The third Bragg pulse is applied to obtain the interference results S of the ratio of the upper and lower zero-state atoms. Δ and Repeat the above steps 10 times to obtain 10 sets of interference results S Δ and Then the Sagnac phase Φ is obtained by ellipse fitting S , calculate the system angular velocity according to step 4.

4. The method according to claim 3, characterized in that: The specific implementation method of step 4 is: A. Due to the Sagnac effect, after the two groups of atoms move in opposite directions for one circle, the phase difference between the two groups of atoms will add a Sagnac phase: in, is the reduced Planck constant, ΔL is the angular momentum difference of the quantum state, Ω is the angular velocity vector of the system, m is the mass of the ultracold atom, Ω is the angular velocity of the system in the direction of rotation, and the loop area of ​​the atomic wave packet motion A=πR 2 , R is the radius of the circular interference loop; and the phase difference between the two groups of atoms below will add the Sagnac phase -Φ s ; Due to system noise, the interference phase in the upper and lower interference processes will produce a certain deviation Φ′, so the phase of the two groups of atoms above Φ Δ And the phase of the two atoms below They are: F Δ =Φ S +Φ′ Perform differential processing to obtain the differential phase δΦ: B. After the third Bragg pulse, the interference result S is obtained Δ and The upper part of the atom will have S Δ =cos 2 (Φ Δ / 2) is transferred to a quantum state with zero momentum, and the lower part of the atoms will have The ratio of is transferred to a quantum state with zero momentum, through the formula Changes to Repeat the same steps 10 times to obtain 10 sets of data; use the 10 sets of data to fit S Δ , About Φ S , Φ Δ Ellipse parameter equation, get Sagnac phase Φ S , and then through the formula Calculate the system angular velocity.

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