Double-layer atomic chip gyroscope and cold atomic group annular beam forming method thereof

Abstract

A double-layer atomic chip gyroscope is composed of two layers of atomic chips, and a surface chip structure can generate closed and smooth annular magnetic guidance without a magnetic field zero point in the center; the bottom chip can generate graded transition magnetic traps, so that cold atomic groups are stably and efficiently loaded into the annular magnetic guide from the macroscopic magneto-optical trap, and meanwhile, the constraint of the magnetic traps in the angular direction of the annular waveguide is increased. Through time sequence cooperation of the two layers of chips, when annular magnetic guidance is loaded into a dimp trap formed by the bottom layer chip of a cold atomic group, angular constraint of the magnetic trap on the cold atomic group disappears, radial constraint of the magnetic trap is increased, extra angular momentum is provided for the cold atomic group, and the annular beam of the cold atomic group and the gyroscope effect of detecting matter waves are achieved. The two layers of chip wires are arranged in a planar structure, are easy to etch on the surface of the chip and are convenient to debug, and the system robustness is high.

Description

Technical Field

[0001] The present invention is applied to the field of atomic precision measurement, especially the field of atomic gyroscopes, in which cold atomic groups are required to generate annular matter wave interference, specifically a double-layer atomic chip gyroscope, which generates annular magnetic guidance that can load cold atomic groups to form annular beams of cold atomic groups. Background Art

[0002] In order to realize a guided atomic chip gyroscope, a core challenge is to construct a circular magnetic potential well that can guide cold atomic groups to interfere along a closed loop. Although Ling Yun-Long et al. (2020, Acta Phys. Sin. 69 (10) 100301) proposed an atomic chip structure that can produce a closed and smooth guided circular magnetic guide with no magnetic field zero point in the center. The structure is composed of three wires containing Archimedean spirals and circular arcs, which are arranged alternately at intervals of π / 3. Among them, the Archimedean spiral part is used to generate circular magnetic guidance, and the circular arc part is used to connect the current, which solves the gap problem of circular magnetic guidance.

[0003] However, this scheme faces significant limitations in practical applications. First, although the structure can produce the required annular magnetic guidance, the fluctuations of its central magnetic potential energy exceed the two-photon kinetic energy range that the split beam laser can provide. This means that without an additional kinetic energy replenishment mechanism, it is difficult for the cold atom cluster to smoothly complete a full circle of movement in the annular magnetic guidance, and it is impossible to form the necessary annular beam and detect the matter wave gyroscope effect. Secondly, from the perspective of cold atom loading, the complexity and divergence of the three-wire Archimedean spiral structure bring additional challenges. The cold atoms captured in the macroscopic magneto-optical trap need to be transferred to the annular magnetic trap through the transition magnetic trap, but due to the particularity of the structure, it is difficult to effectively wire around it to produce other magnetic traps besides the annular magnetic guidance, which greatly limits the flexibility and efficiency of the loading process.

[0004] Therefore, how to solve the problems of cold atom loading and kinetic energy replenishment while maintaining the advantages of toroidal magnetic guidance has become a bottleneck in the current technological development. Summary of the invention

[0005] In order to overcome the deficiencies of the above-mentioned prior art, the present invention proposes a double-layer atomic chip gyroscope, which can solve the problem that cold atomic clusters are difficult to move completely in the annular magnetic guidance generated by the three-wire Archimedean spiral structure to form an annular beam when relying solely on the kinetic energy of split laser two-photons, as well as the challenge of efficiently transferring cold atomic clusters from a macroscopic magneto-optical trap to annular magnetic guidance.

[0006] The technical solution of the present invention is as follows:

[0007] On the one hand, the present invention provides a double-layer atomic chip gyroscope, which is characterized in that it is formed by pasting a surface chip and a bottom chip together, wherein the surface chip is used to generate a circular magnetic guide with a closed and smooth guide center and no magnetic field zero point; the bottom chip is used to generate a graded transition magnetic trap to achieve the transfer of cold atomic clusters from a macroscopic magneto-optical trap to the circular magnetic guide, and further cool them during the transfer process; the surface chip and the bottom chip provide additional angular momentum for the cold atomic clusters through timing coordination and changes in the magnetic trap structure, thereby realizing a circular beam for detecting the matter wave gyroscope effect.

[0008] Furthermore, the surface chip is composed of three wires of the same shape arranged alternately on the atomic chip substrate at a rotation angle of π / 3, and each wire is composed of a first straight wire segment, a first Archimedean spiral wire segment, a first circular arc wire segment, a second circular arc wire segment, a second Archimedean spiral wire segment and a second straight wire segment in sequence; wherein the first straight wire segment and the second straight wire segment are respectively used for input and output of current; and the first Archimedean spiral wire segment and the second Archimedean spiral wire segment are used to generate a circular magnetic field guidance.

[0009] Further, the expression of the center of the first Archimedean spiral wire segment and the second Archimedean spiral wire segment in polar coordinates is:

[0010] r=5+(0.3 / π)θ, where r is the radius of the center of the Archimedean spiral wire segment, and θ is the rotation angle.

[0011] Furthermore, the first circular arc wire segment is connected to the starting point of the first Archimedean spiral wire segment, and the first straight wire segment is connected to the end point of the first Archimedean spiral wire segment and is tangent to each other; the second circular arc wire segment is connected to the starting point of the second Archimedean spiral wire segment, and the second straight wire segment is connected to the end point of the second Archimedean spiral wire segment and is tangent to each other.

[0012] Furthermore, the bottom chip is arranged on the atomic chip substrate by five mutually parallel wires and a sixth wire that vertically runs through the five wires. By loading different currents on the wires, multiple Z-shaped wire structures are constructed to generate graded transition magnetic traps, including macroscopic Z-traps, Z-shaped micromagnetic traps and dimple traps, thereby achieving a smooth transfer of cold atomic clusters from macroscopic magneto-optical traps to annular magnetic guidance.

[0013] Furthermore, the five wires are respectively a first wire, a second wire, a third wire, a fourth wire and a fifth wire, wherein the third wire is arranged at the center of the atomic chip substrate with a width of 0.1 mm, the second wire and the fourth wire are symmetrically distributed with the third wire as the center axis, and the spacing between the two is 2 mm, and the width is 0.2 mm; the first wire and the fifth wire are symmetrically distributed with the third wire as the center axis, and the spacing between the two is 6 mm, and the width is 0.5 mm; the sixth wire is arranged at the lower part of the atomic chip substrate, and is 14.8 mm away from the lower edge of the atomic chip substrate, and has a width of 0.5 mm.

[0014] The wire layouts of both layers of the chip are planar structures, which are easy to etch on the chip surface and convenient for debugging, and the system has strong robustness.

[0015] On the other hand, the present invention also provides a method for generating an annular beam using the above-mentioned double-layer atomic chip gyroscope, characterized in that:

[0016] First, current is applied through the wires of the bottom chip to form a macroscopic Z-trap, which receives the cold atomic clusters in the macroscopic magneto-optical trap.

[0017] Then, the current is gradually adjusted to move the magnetic trap toward the chip surface and compress it, eventually loading the cold atomic clusters into the dimple trap;

[0018] The current and bias magnetic field of the bottom chip are turned off, and the three wires of the surface chip are loaded with modulated current to form a circular magnetic guide under the surface chip. At this time, the cold atomic clusters are loaded from the dimple trap into the circular magnetic guide, and the cold atomic clusters gain additional momentum in the angular direction to form a circular beam.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) After the surface chip is loaded with modulated current, a closed and smooth circular magnetic guide with no magnetic field zero point in the center can be generated. The magnetic guide can be used to enable cold atomic groups to achieve loop interference and detect the material wave gyroscope effect. The surface chip wire is a planar structure, which is convenient for processing and manufacturing;

[0021] 2) The bottom chip can be used to generate a zero-point magnetic potential well with no magnetic field, which is gradually compressed in the x direction, the magnetic trap frequency is gradually increased, and the center of the magnetic trap is gradually close to the chip surface, so that the cold atomic groups can be efficiently transferred from the macroscopic magneto-optical trap to the annular magnetic guide. The bottom chip wire is also a planar structure, which is convenient for processing and manufacturing;

[0022] 3) When the cold atomic clusters are loaded from the dimple trap formed by the bottom chip into the annular magnetic guide formed by the surface chip, the angular restraint of the magnetic trap on the cold atomic clusters disappears, and the radial restraint increases, providing the cold atomic clusters with additional angular momentum and realizing an annular beam of the cold atomic clusters. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of the surface chip of the double-layer atomic chip gyroscope of the present invention;

[0024] Figure 2 It is a schematic diagram of the structure of a single wire in the surface chip of the double-layer atomic chip gyroscope of the present invention;

[0025] Figure 3 It is a schematic structural diagram of the bottom chip of the double-layer atomic chip gyroscope of the present invention;

[0026] Figure 4 It is an overall assembly diagram of the surface chip and the bottom chip of the double-layer atomic chip gyroscope of the present invention. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and embodiments, but this should not limit the protection scope of the present invention.

[0028] A double-layer atomic chip gyroscope is made of two layers of atomic chips, namely the surface chip and the bottom chip. The surface chip is used to generate a circular magnetic guide with no magnetic field zero point in the center of a closed and smooth guide; the bottom chip is responsible for generating a graded transition magnetic trap to achieve a smooth and efficient transfer of cold atomic groups from the macroscopic magneto-optical trap to the circular magnetic guide, and further cooling during the transfer process. The two layers of atomic chips provide additional angular momentum for the cold atomic groups through timing coordination and changes in the magnetic trap structure, thereby realizing a circular beam for detecting the matter wave gyroscope effect.

[0029] See also Figure 1 , Figure 1It is a schematic diagram of the structure of the surface chip of the double-layer atomic chip gyroscope of the present invention. As shown in the figure, the surface chip is composed of three wires of the same shape arranged alternately on the atomic chip substrate at a rotation angle of π / 3, and the spacing between the centers of adjacent wires is maintained at 0.1mm. The starting end 11 of the first wire, the starting end 21 of the second wire and the starting end 31 of the third wire are current input terminals; the terminating end 16 of the first wire, the terminating end 26 of the second wire and the terminating end 36 of the third wire are current output terminals. In this embodiment, the size of the chip substrate is 30.0mm×30.0mm, the width of the three wires is 90μm, the groove width between each wire is 10μm, the groove width in the non-functional area is widened to 100μm, the insulation resistance between each wire is>200MΩ, the working current is greater than 1A, and the duration of the current loading of each wire at the same time is up to 20s. The atomic chip substrate has three layers. The top layer is a gold (Au) layer with a thickness greater than 4μm, and the surface can provide a reflectivity of ≥90%@780nm (the reference value of the root mean square roughness of the chip surface is ≤10nm); the second layer is SiO2 with a thickness of 0.5μm; the third layer is Si with a thickness of 300μm. Gold easily absorbs the working element rubidium. After long-term use, a layer of misty rubidium powder will adhere to the surface of this chip, affecting the reflective quality of the gold layer. Therefore, after the production is completed, a quartz film is plated on the functional area of ​​20.0mm×20.0mm. The film thickness is 10nm to prevent the functional area from absorbing rubidium atoms.

[0030] Figure 2 It is a schematic diagram of the structure of a single wire in the surface chip of the double-layer atomic chip gyroscope of the present invention. As shown in the figure, each wire includes: a first straight wire segment 1, a first Archimedean spiral wire segment 2, a first arc wire segment 3, a second arc wire segment 4, a second Archimedean spiral wire segment 5 and a second straight wire segment 6. Among them, the first straight wire segment 1 and the second straight wire segment 6 are used for input and output of current respectively; the first Archimedean spiral wire segment 2 and the second Archimedean spiral wire segment 5 are responsible for generating a circular magnetic field guidance; the first arc wire segment 3 and the second arc wire segment 4 are used to connect different parts.

[0031] Each wire has central symmetry, and each segment of the spiral, arc and straight wire has a smooth transition. The expression of the center of the Archimedean spiral wire segment in polar coordinates in this structure is:

[0032] r=5+(0.3 / π)θ, where r is the radius (mm) of the Archimedean spiral wire segment center, θ is the rotation angle, and the set rotation angle is 0 to 17π / 18. According to the expression, the starting radius of the Archimedean spiral wire segment center is 5mm, and the radius increases by 0.3mm for every increase of π in the angle. The center of the arc wire segment is a semicircle with a diameter of 5mm connected to the starting point of the Archimedean spiral wire segment; the straight wire segment is connected to the end point of the Archimedean spiral wire segment and is tangent.

[0033] See also Figure 3 , Figure 3 It is a structural schematic diagram of the bottom chip of the double-layer atomic chip gyroscope of the present invention. As shown in the figure, the bottom chip consists of five first wires 41, second wires 42, third wires 43, fourth wires 44 and fifth wires 45 arranged in parallel on the atomic chip substrate, and a sixth wire 46 that vertically penetrates the five wires. Among them, the third wire 43 is arranged at the center of the atomic chip substrate, with a width of 0.1mm, and can pass a maximum current greater than 2A. The second wire 42 and the fourth wire 44 are symmetrically distributed with the third wire 43 as the central axis, and the spacing between the two is 2mm, the width is 0.2mm, and the maximum current that can be loaded is greater than 4A. The first wire 41 and the fifth wire 45 are symmetrically distributed with the third wire 43 as the central axis, and the spacing between the two is 6mm, the width is 0.5mm, and can carry a maximum current of more than 10A. The sixth wire 46 is arranged at the lower part of the atomic chip substrate, and is 14.8mm away from the lower edge of the atomic chip substrate, with a width of 0.5mm, and can also carry a maximum current of more than 10A.

[0034] The material of the Atom chip substrate can be immersion gold PCB, which is easy to process and dissipate heat. The size of the immersion gold board is 40.0mm×40.0mm, the surface immersion gold thickness is 1μm, the lower copper surface thickness is 35μm, and the bottom layer is a 1mm thick PCB board.

[0035] Use vacuum glue to stick the bottom chip conductor surface and the surface chip back surface together. The distance between the edge of the surface chip and the edge of the bottom chip is 5mm. Figure 4 a, wherein the center of the sixth wire 46 of the bottom chip and the center of the first Archimedean spiral wire segment 2 of the second wire in the surface chip are projected in the direction perpendicular to the chip as shown in FIG. Figure 4 b.

[0036] The two-layer chip can be turned on step by step to realize the efficient transfer of cold atomic groups from the macroscopic magneto-optical trap to the annular magnetic guide and form an annular beam. The specific steps are as follows:

[0037] Step 1: The bottom chip is used to generate a hierarchical transition magnetic trap to realize the transfer of cold atomic groups from the macroscopic magneto-optical trap to the macroscopic Z trap to the Z-shaped micro-magnetic trap and the dimple trap to the location of the annular magnetic guide. The process is as follows:

[0038] 1. Under the condition of 0.5 mT bias magnetic field in y direction, the first wire 41 and the fifth wire 45 are turned on, and when carrying 10 A current, the magnetic trap is located 1.5 mm below the surface chip, and the formed macro Z trap is connected to the cold atomic groups in the macro magneto-optical trap to transfer to the chip surface;

[0039] 2. Keep the bias magnetic field unchanged, gradually reduce the current of the first wire 41 and the fifth wire 45, increase the current of the second wire 42 and the fourth wire 44, realize the compression of the magnetic trap in the x direction, and reduce the wire current to 4A. When the current of the first wire 41 and the fifth wire 45 gradually decreases to 0, the magnetic trap frequency increases, and the magnetic trap position is located 0.5mm below the surface chip. At this time, optical pumping is performed to load the cold atomic group into the Z-shaped micro magnetic trap;

[0040] 3. When the bias magnetic field remains unchanged and the current of the second wire 42 and the fourth wire 44 continues to decrease to 2A, the magnetic trap frequency further increases, and the magnetic trap position is 0.1mm below the surface chip, that is, the position where the annular magnetic guide is formed;

[0041] 4. The third wire 43 in the middle is turned on, and the currents of the second wire 42 and the fourth wire 44 are gradually reduced to 0, and a dimple well is formed in cooperation with the bias magnetic field to keep the magnetic well 0.1 mm below the surface chip, and increase the x-direction constraint of the magnetic well. Here, the center of the sixth wire 46 is tangent to the center of the annular magnetic guide, so the x-direction is the angular direction of the annular magnetic guide. At the same time, evaporative cooling is performed to increase the density of the cold atomic clusters to prepare for loading into the annular magnetic guide.

[0042] Step 2: Turn off the bias magnetic field, turn off the current of the bottom chip wire, and load the modulation current on the three wires of the surface chip. The modulation current expressions are:

[0043] I1=I a +I b sin(ω b t+φ),

[0044] I2=-I a -I b sin(ω b t),

[0045] I3=I a +I b sin(ω b t-φ),

[0046] Among them I a is the DC size, I b is the AC size, t is the time, ω b is the modulation frequency, and φ is the phase difference of the modulation current loaded on different wires.

[0047] After testing, set I a / I b =10, which can suppress the fluctuation of the magnetic guide center size. When the loading current I a 1A, I bWhen the current is 0.1A, the magnetic field in the center of the annular magnetic guide is about 0.25mT, and the fluctuation is about 0.005mT. As the angle θ changes, the relative positions of the three wires in the surface chip are constantly changing. In order to ensure that the current phase difference of the three wires remains consistent within a loop, the current phase difference φ is set to 2π / 3. The magnetic field size felt by atoms trapped in the magnetic trap is a time average value and has nothing to do with the modulation frequency. However, the adiabatic approximation condition of atomic motion requires that the modulation frequency of the magnetic trap should be less than the Larmor oscillation frequency and greater than the frequency of the magnetic trap itself. 87 Rb(5 2 S 1 / 2 , F = 2, m F =2), its Larmor frequency at the magnetic guidance center is about ω L ≈2π×5.2MHz, the frequency of the annular magnetic guide trap is about ω t ≈2π×30Hz, so choose ω b =2π×10kHz.

[0048] After the surface chip wire is loaded with modulated current, an annular magnetic guide is formed 0.1mm below the surface chip, and the cold atomic clusters are transferred from the dimple trap to the annular magnetic guide. The angular confinement disappears, and the radial confinement increases, realizing the atomic cluster beam splitting circulation. a 1A, I b When the current is 0.1A, the magnetic field in the center of the annular magnetic guide is about 0.25mT, the fluctuation is about 0.005mT, and the shallowest depth of the magnetic well is about 0.3mT. 87 Rb(5 2 S 1 / 2 , F = 2, m F =2), the fluctuation of the magnetic field of the annular magnetic guide is about 3.4μK, and the shallowest depth of the magnetic trap is about 200μK. After the evaporative cooling in the previous stage, the temperature of the cold atom group is generally lower than 10μK, so the depth of the magnetic trap can completely restrain the cold atom group from moving in the magnetic trap, and the cold atoms heated by the movement will also escape, which can play a filtering role. 87 Rb(5 2 S 1 / 2 , F = 2, m F =2) of the 780nm split laser two-photon momentum It is about 1μK, which is smaller than the magnetic field fluctuation. However, since the cold atom group is loaded from the dimple trap into the annular magnetic guide, the angular restraint disappears and the radial restraint becomes larger. The change in the magnetic trap structure will make the cold atoms gain additional momentum in the angular direction, and the initial position of the cold atom group loaded in the annular guide is not the lowest point of the entire guidance potential energy. The magnetic field fluctuation can also be reduced by reducing the modulation current to achieve the purpose of the cold atom group to smoothly form an annular beam and detect the matter wave gyro effect.

[0049] This embodiment realizes the efficient transfer of cold atomic clusters from macroscopic magneto-optical traps to annular magnetic guidance through the graded transition magnetic trap of the bottom chip, and further cools them during the transfer process. The wire layout design of the surface chip and the use of modulated current suppress the fluctuation of the magnetic field in the center of the magnetic guidance. The bottom chip and the surface chip provide additional angular momentum for the cold atomic clusters through timing coordination and changes in the magnetic trap structure, thereby ensuring that the cold atomic clusters can stably form annular beams. The wire layout of the two-layer chip is a planar structure, which is easy to etch on the chip surface and convenient for debugging and maintenance.

Claims

1. A double-layer atomic chip gyroscope, characterized in that: It is made of a surface chip and a bottom chip pasted together. The surface chip is used to generate a circular magnetic guide with a closed and smooth guide center and no magnetic field zero point; the bottom chip is used to generate a graded transition magnetic trap to achieve the transfer of cold atomic clusters from the macroscopic magneto-optical trap to the circular magnetic guide, and further cool them during the transfer process; the surface chip and the bottom chip provide additional angular momentum for the cold atomic clusters through timing coordination and changes in the magnetic trap structure, thereby realizing a circular beam for detecting the matter wave gyroscope effect.

2. A double-layer atomic chip gyroscope according to claim 1, characterized in that: The surface chip comprises three wires of the same shape arranged alternately on an atomic chip substrate at a rotation angle of π / 3, each wire being sequentially composed of a first straight wire segment (1), a first Archimedean spiral wire segment (2), a first circular arc wire segment (3), a second circular arc wire segment (4), a second Archimedean spiral wire segment (5) and a second straight wire segment (6); wherein the first straight wire segment (1) and the second straight wire segment (6) are respectively used for input and output of current; and the first Archimedean spiral wire segment (2) and the second Archimedean spiral wire segment (5) are used for generating a circular magnetic field guidance.

3. A double-layer atomic chip gyroscope according to claim 2, characterized in that: The expression of the center of the first Archimedean spiral wire segment (2) and the second Archimedean spiral wire segment (5) in polar coordinates is: r=5+(0.3 / π)θ, Where r is the radius of the Archimedean spiral segment center, and θ is the rotation angle.

4. A double-layer atomic chip gyroscope according to claim 2, characterized in that: The first circular arc wire segment is connected to the starting point of the first Archimedean spiral wire segment, and the first straight wire segment is connected to the end point of the first Archimedean spiral wire segment and is tangent to each other; the second circular arc wire segment is connected to the starting point of the second Archimedean spiral wire segment, and the second straight wire segment is connected to the end point of the second Archimedean spiral wire segment and is tangent to each other.

5. The double-layer atomic chip gyroscope according to claim 1, characterized in that: The bottom chip is composed of five parallel wires and a sixth wire that vertically runs through the five wires, arranged on the atomic chip substrate. By loading different currents on the wires, multiple Z-shaped wire structures are constructed to generate graded transition magnetic traps, including macroscopic Z traps, Z-shaped micromagnetic traps and dimple traps, thereby achieving a smooth transfer of cold atomic clusters from macroscopic magneto-optical traps to annular magnetic guidance.

6. A double-layer atomic chip gyroscope according to claim 5, characterized in that: The five wires are respectively a first wire (41), a second wire (42), a third wire (43), a fourth wire (44) and a fifth wire (45), wherein the third wire (43) is arranged at the center of the atomic chip substrate and has a width of 0.1 mm; the second wire (42) and the fourth wire (44) are symmetrically distributed with the third wire (43) as the central axis, and the spacing between the two is 2 mm, and the width is 0.2 mm; the first wire (41) and the fifth wire (45) are symmetrically distributed with the third wire (43) as the central axis, and the spacing between the two is 6 mm, and the width is 0.5 mm; the sixth wire (46) is arranged at the lower part of the atomic chip substrate, and is 14.8 mm away from the lower edge of the atomic chip substrate, and has a width of 0.5 mm.

7. A method for generating an annular beam using the double-layer atomic chip gyroscope according to any one of claims 1 to 6, characterized in that: First, current is applied through the wires of the bottom chip to form a macroscopic Z-trap, which receives the cold atomic clusters in the macroscopic magneto-optical trap. Then, the current is gradually adjusted to move the magnetic trap toward the chip surface and compress it, eventually loading the cold atomic clusters into the dimple trap; The current and bias magnetic field of the bottom chip are turned off, and the three wires of the surface chip are loaded with modulated current to form a circular magnetic guide under the surface chip. At this time, the cold atomic clusters are loaded from the dimple trap into the circular magnetic guide, and the cold atomic clusters gain additional momentum in the angular direction to form a circular beam.

8. The method for generating annular beam by a double-layer atomic chip gyroscope according to claim 7, characterized in that: The three wires of the surface chip are loaded with modulation current, and the modulation current expressions are: I1=I a +I b sin(ω b t+φ), I2=-I a -I b sin(ω b t), I3=I a +I b sin(ω b t-φ), Among them I a is the DC size, I b is the AC size, t is the time, ω b is the modulation frequency, and φ is the phase difference of the modulation current loaded on different wires.

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