3-axis magnetic field correction coil, physical package, and physical package system

Abstract

The object of this invention is to realize a new magnetic field correction coil that can also be miniaturized or portable in terms of physical packaging. The 3-axis magnetic field correction coil (96) has a first coil group and a second coil group in the X-axis direction passing through the clock transition space where atoms are arranged. The first coil group is a Helmholtz type coil, which is formed in a point-symmetric shape centered on the clock transition space (52). The second coil group is a non-Helmholtz type coil, which is formed in the X-axis direction in a point-symmetric shape centered on the clock transition space (52), and the coil size, coil shape or inter-coil spacing is different from that of the first coil group.

Description

Technical Field

[0001] This invention relates to a 3-axis magnetic field correction coil, physical packaging, physical packaging for optical lattice clocks, physical packaging for atomic clocks, physical packaging for atomic interferometers, physical packaging for quantum information processing devices, and physical packaging systems. Background Technology

[0002] The optical lattice clock is an atomic clock proposed in 2001 by Hidetoshi Katori, one of the inventors of this application. In an optical lattice clock, atomic clusters are enclosed within an optical lattice formed by laser light, measuring the resonant frequency in the visible light region. Therefore, it can perform measurements with 18-bit precision, far exceeding the accuracy of current cesium clocks. The optical lattice clock has not only been the subject of intensive research and development by the inventors, but also by various domestic and international organizations, and is being developed into the next generation of atomic clocks.

[0003] Regarding recent optical lattice clock technology, examples include the following patent documents 1-3. Patent document 1 describes forming a one-dimensional movable optical lattice inside an optical waveguide with a hollow channel. Patent document 2 describes a scheme for setting an effective magic frequency. Furthermore, patent document 3 describes a radiation shielding device that reduces the effects of blackbody radiation emitted from the surrounding walls.

[0004] Optical lattice clocks, due to their high-precision timekeeping, can detect even a 1cm difference in elevation on Earth, based on the general relativistic effects of gravity, as a deviation in the course of time. Therefore, if optical lattice clocks can be made portable for field use outside research facilities, their applications will expand to new geodetic technologies such as underground resource exploration, underground cavern detection, and magma chamber detection. By mass-producing and deploying optical lattice clocks in various locations, continuous monitoring of temporal variations in gravitational potential will enable applications such as crustal movement detection and spatial mapping of gravitational fields. Thus, optical lattice clocks are expected to transcend the limitations of high-precision timekeeping and contribute to society as a new fundamental technology.

[0005] Non-Patent Documents 1-5 describe attempts to make optical lattice clocks portable. For example, Non-Patent Document 4 describes a physical package for an optical lattice clock housed in a frame with a length of 99 cm, a width of 60 cm, and a height of 45 cm. In this physical package, an atomic furnace, a Zeeman reducer, and a vacuum chamber are arranged sequentially along the length direction. Furthermore, on the outside of the vacuum chamber, a pair of square magnetic field correction coils, each with a side width of 30-40 cm, are provided along the three axes of length, width, and height. In order to perform clock transition spectral dispersion of atoms under zero magnetic field, the magnetic field correction coils are used to compensate the magnetic field distribution in the region surrounding the atoms during spectral dispersion to zero.

[0006] Homogenization of the magnetic field using magnetic field correction coils is also performed in the field of NMR (Nuclear Magnetic Resonance). For example, Patent Document 4 describes arranging multiple circular coils of the same size along the quantization axis to achieve magnetic field homogenization in the space where the sample is placed. Here, homogenization is achieved by precisely controlling the spatial micro-component along the quantization axis for the magnetic field. Furthermore, in recent NMR devices, the spatial micro-component along the quantization axis is also precisely controlled for the magnetic field component in the direction orthogonal to the quantization axis.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 6206973

[0010] Patent Document 2: Japanese Patent Publication No. 2018-510494

[0011] Patent Document 3: Japanese Patent Application Publication No. 2019-129166

[0012] Patent Document 4: Japanese Patent No. 3083475

[0013] Non-patent literature

[0014] Non-patent literature 1: Stefan Vogt et al., "A transportable optical lattice clock", Journal of Physics: Conference Series 72301, 2020, 2016.

[0015] Non-patent literature 2: SB Koller et al., "Transportable Optical Lattice Clock with 7×10⁻¹⁷ Uncertainty", Physical Review Letters 118073601, 2017

[0016] Non-patent literature 3: William Bowden et al., "A pyramid MOT with integrated optical cavities as a cold atom platform for an optical lattice clock", Scientific Reports 911704, 2019.

[0017] Non-Patent Literature 4: S. Origlia et al., "Towards an optical clock for space: Compact, high-performance optical lattice clock based on bosonic atoms," Physical Review A 98, 053443, 2018.

[0018] Non-Patent Literature 5: N. Poli et al., "Prospect for a compact strontium opticallattice clock", Proceedings of SPIE 6673, 2007 Summary of the Invention

[0019] The problem the invention aims to solve

[0020] By further miniaturizing or making the optical lattice clocks more portable than those described in the aforementioned non-patent documents 1 to 5, the handling and setup of the optical lattice clocks become easier, and their usability is also improved.

[0021] In particular, the conventional magnetic field correction coils are large, which is a major reason why the physical packaging of optical lattice clocks cannot be miniaturized. Furthermore, large magnetic field correction coils also hinder power saving. However, if the conventional magnetic field correction coils are simply miniaturized and placed close to the space where the trapped atoms are located, the spatial variation of the generated magnetic field will increase, making it difficult to homogenize the magnetic field. Moreover, in miniaturized optical lattice clocks, unlike the NMR devices described in Patent Document 4, it is difficult to ensure sufficient space for placing the correction coils.

[0022] Furthermore, with the pursuit of portability, frequent magnetic field homogenization is required in various magnetic field environments. A magnetic field correction coil is needed to rapidly and accurately correct the magnetic field even when placed in complex magnetic field environments. Even without miniaturization and portability, magnetic field homogenization is crucial for achieving high measurement accuracy. Not only optical lattice clocks, but also high-precision quantum measurement equipment widely requires miniaturization or portability.

[0023] The purpose of this invention is to realize a new magnetic field correction coil that can also be miniaturized or portable in terms of physical packaging.

[0024] Solution for solving the problem

[0025] The 3-axis magnetic field correction coil of the present invention comprises: a first coil group of Helmholtz type, which is formed in a point-symmetric shape about the clock transition space as the center in the direction of the first axis passing through the clock transition space in which atoms are arranged; and a second coil group of non-Helmholtz type, which is formed in a point-symmetric shape about the clock transition space as the center in the direction of the first axis, wherein the coil size, coil shape or inter-coil distance is different from that of the first coil group.

[0026] In one aspect of the invention, currents of different magnitudes and directions can be passed through each coil constituting the first coil group.

[0027] In one embodiment of the invention, the coils constituting the second coil group are electrically connected, and the same magnitude of current flows in the same direction around the first shaft.

[0028] In one embodiment of the invention, the 3-axis magnetic field correction coil includes a non-Helmholtz type third coil group, which is formed in a point-symmetric shape centered on the clock transition space in the direction of the first axis. The coil size, coil shape, or inter-coil distance is different from that of the first and second coil groups. The coils constituting the third coil group are electrically connected, and the same magnitude of current flows in the opposite direction around the first axis.

[0029] In one embodiment of the invention, in each of the directions of a second axis perpendicular to the first axis and a third axis perpendicular to both the first and second axes, the 3-axis magnetic field correction coil comprises: a Helmholtz-type fourth coil group formed in a point-symmetric shape centered on the clock transition space; and a non-Helmholtz-type fifth coil group formed in a point-symmetric shape centered on the clock transition space, wherein the coil size, coil shape, or inter-coil distance differs from that of the fourth coil group.

[0030] In one embodiment of the invention, in the fourth coil group, two composite coils composed of multiple small coils are formed in a point-symmetric shape with the clock transition space as the center. In the two composite coils of the fourth coil group, the multiple small coils are arranged with their centers offset in the direction of the first axis. The two composite coils of the fourth coil group are formed in a shape that becomes equivalent to a Helmholtz type when the current flowing through the multiple small coils is adjusted.

[0031] In one embodiment of the invention, the coils constituting the fifth coil group are electrically connected, and the same magnitude of current flows in the same direction around the axis around which the fifth coil group is arranged.

[0032] In one embodiment of the present invention, the 3-axis magnetic field correction coil is formed in such a shape that it can correct the constant term, the first-order spatial differential term, and the second-order spatial differential term in the direction of the first axis for the magnetic field components in the directions of the first axis, the second axis, and the third axis.

[0033] The physical packaging system of the present invention includes: the 3-axis magnetic field correction coil; and a control device that controls the current flowing through the correction coil of the 3-axis magnetic field.

[0034] In one embodiment of the invention, the vacuum chamber, device, or support member of the physical package includes a portion formed as point-symmetric about the clock transition space, and at least a portion of the coil of the 3-axis magnetic field correction coil is formed on a flexible printed circuit board and assembled at the point-symmetric portion.

[0035] The 3-axis magnetic field correction coil of the present invention can be used in physical packages for optical lattice clocks, physical packages for atomic clocks, physical packages for atomic interferometers, and physical packages for quantum information processing devices targeting atoms or ionized atoms.

[0036] The physical package of the present invention comprises: the 3-axis magnetic field correction coil; and at least one of the following atomic laser cooling technology devices for guiding the atoms to the clock transition space: a Zeeman reducer, a magneto-optical trap, and an optical lattice trap.

[0037] Invention Effects

[0038] According to the present invention, a magnetic field correction coil that can be miniaturized or made portable in terms of physical packaging can be realized. Attached Figure Description

[0039] Figure 1 This is a schematic diagram showing the overall configuration of the optical lattice clock according to an embodiment.

[0040] Figure 2 This is a diagram showing the general configuration of the physical package of an optical lattice clock.

[0041] Figure 3 This is a diagram that roughly shows the appearance of the physical package.

[0042] Figure 4 It is Figure 3 The diagram shows a partial perspective view of the internal physical package.

[0043] Figure 5 This is a diagram showing the overall shape of the 3-axis magnetic field correction coil.

[0044] Figure 6 This is a diagram showing the shape of the first coil group of the X-axis magnetic field correction coil.

[0045] Figure 7 This is a diagram showing the shape of the second coil group of the X-axis magnetic field correction coil.

[0046] Figure 8 This is a diagram showing the shape of the first coil group of the Y-axis magnetic field correction coil.

[0047] Figure 9 This is a diagram showing the shape of the second coil group of the Y-axis magnetic field correction coil.

[0048] Figure 10 This is a diagram showing the shape of the first coil group of the Z-axis magnetic field correction coil.

[0049] Figure 11 This is a diagram showing the shape of the second coil group of the Z-axis magnetic field correction coil.

[0050] Figure 12 This is a diagram showing the shape of the holder of the 3-axis magnetic field correction coil.

[0051] Figure 13 This is a diagram illustrating an example of a correction coil using a flexible printed circuit board.

[0052] Figure 14 This is a diagram showing a cylindrical correction coil using a flexible printed circuit board.

[0053] Figure 15 This is a diagram showing an example of the current flowing through the correction coil.

[0054] Figure 16 It is shown that... Figure 15 The diagram shows the equivalent current flow of the correction coil.

[0055] Figure 17 This is a diagram showing another example of the current flowing through the correction coil.

[0056] Figure 18 It is shown that... Figure 17 The diagram shows the equivalent current flow of the correction coil.

[0057] Figure 19 This is another example of a correction coil using a flexible printed circuit board.

[0058] Figure 20 This is a diagram showing the physical package of a vacuum chamber with a spherical shape.

[0059] Figure 21 This is a diagram showing another example of a 3-axis magnetic field correction coil setup.

[0060] Figure 22 This is an explanation Figure 21 A diagram showing the support method of the 3-axis magnetic field correction coil.

[0061] Figure 23A This is a schematic diagram illustrating the method of magnetic field correction.

[0062] Figure 23B This is a schematic diagram illustrating the method of magnetic field correction.

[0063] Figure 24 This is a flowchart of the calibration process for a 3-axis magnetic field correction coil.

[0064] Figure 25 This is a flowchart illustrating the calibration steps of a 3-axis magnetic field correction coil.

[0065] Figure 26 This is a schematic diagram illustrating another example of how a magnetic field can be corrected.

[0066] Figure 27 This is a diagram showing the compensation for the leakage magnetic field in the refrigeration unit.

[0067] Figure 28 This is a cross-sectional view showing the structure of the Zeeman reducer and the MOT device.

[0068] Figure 29 It is a cross-sectional diagram illustrating the gap in the coil.

[0069] Figure 30 It is shown that... Figure 28 The diagram shows the magnetic field distribution corresponding to the composition of the structure.

[0070] Figure 31A This is a cross-sectional view showing the structure of the Zeeman reducer and the MOT device.

[0071] Figure 31B This is a cross-sectional view showing the structure of the Zeeman reducer and the MOT device.

[0072] Figure 32 It is shown that... Figure 31A , Figure 31B The diagram shows the magnetic field distribution corresponding to the composition of the structure.

[0073] Figure 33A It is shown Figure 31A , Figure 31B A diagram of the structure in the deformation mode.

[0074] Figure 33B It is shown Figure 31A , Figure 31B A diagram of the structure in the deformation mode.

[0075] Figure 34 This is a cross-sectional view of a Zeeman coil with a constant outer diameter.

[0076] Figure 35A This is a cross-sectional view showing the encapsulation of the coil used in the Zeeman reducer.

[0077] Figure 35B This is a cross-sectional view showing the encapsulation of the coil used in the Zeeman reducer. Detailed Implementation

[0078] (1) A general outline of the physical package

[0079] Figure 1 This is a schematic diagram showing the overall structure of the optical lattice clock 10. The optical lattice clock is composed of a physical package 12, an optical system device 14, a control device 16, and a PC (personal computer) 18.

[0080] The physical package 12, as detailed below, is a device that captures atomic clusters, encloses them in an optical lattice, and induces clock transitions. The optical system device 14 is a device equipped with optical devices such as a laser emitter, a laser receiver, and a laser beam splitter. In addition to emitting laser light and transmitting it to the physical package 12, the optical system device 14 also receives light emitted by atomic clusters within the physical package 12 due to clock transitions, converts it into electrical signals, and performs frequency division within a frequency band. The control device 16 is a device that controls the physical package 12 and the optical system device 14. The control device 16 is a computer specifically designed for the optical lattice clock 10, and operates by using software to control computer hardware equipped with a processor and memory. In addition to controlling the operation of, for example, the physical package 12 and the optical system device 14, the control device 16 performs analytical processing such as frequency analysis of the clock transitions obtained through measurement. The physical package 12, the optical system device 14, and the control device 16 work closely together to form the optical lattice clock 10.

[0081] PC18 is a general-purpose computer that operates by using software to control computer hardware equipped with a processor and memory. An application program for controlling the optical lattice clock 10 is installed on PC18. PC18 is connected to control device 16 and controls not only control device 16 but also the entire optical lattice clock 10, including the physical package 12 and the optical system device 14. Furthermore, PC18 serves as the user interface (UI) of the optical lattice clock 10, allowing users to start the optical lattice clock 10, measure time, and confirm results. In this embodiment, the description focuses on the physical package 12. However, the system including the physical package 12 and the components required for its control is sometimes referred to as the physical package system. The components required for control are sometimes included in the control device 16 or PC18, but sometimes they are also built into the physical package 12 itself.

[0082] Figure 2 This is a schematic diagram illustrating the physical package 12 of the optical lattice clock according to an embodiment. Additionally, Figure 3 This is a diagram showing an example of the appearance of the physical package 12. Figure 4 It is Figure 3 The diagram shows a partial perspective view of the internal structure of the physical package 12. Figures 2-4 The diagram (and the following diagrams) shows an XYZ orthogonal linear coordinate system with the origin of the object space (clock transition space 52) where the atoms described later can exist during clock transition spectroscopy, clearly indicating the direction.

[0083] The physical package 12 includes: a vacuum chamber 20, an atomic oven 40, a Zeeman Slower (ZS) coil 44, an optical resonator 46, a MOT (Magneto-Optical Trap) coil 48, a cryogenic bath 54, a thermal connection member 56, a freezer 58, a vacuum pump body 60, and a vacuum pump cartridge 62.

[0084] The vacuum chamber 20 is a container that maintains a vacuum in the main part of the physical encapsulation 12, and is formed in a generally cylindrical shape. Specifically, the vacuum chamber 20 includes: a main body 22, which is formed in a large, generally cylindrical shape; and a protrusion 30, which is formed in a small, generally cylindrical shape protruding from the main body 22. The main body 22 is the part that internally houses the optical resonator 46, etc., which will be described later. The main body 22 includes: a cylindrical wall 24, which forms the side of the cylinder; and a front circular wall 26 and a rear circular wall 28, which form the circular surfaces of the cylinder. The front circular wall 26 is the wall on which the protrusion 30 is provided. The rear circular wall 28 is the wall on the side opposite to the protrusion 30, and is formed in a shape with an enlarged diameter compared to the cylindrical wall 24.

[0085] The protrusion 30 includes: a cylindrical wall 32 forming the side surface of a cylinder; and a front circular wall 34. The front circular wall 34 is a circular surface on the side away from the main body 22. The protrusion 30 is mostly open on the side facing the main body 22, connected to the main body 22, and does not have a wall portion.

[0086] The vacuum chamber 20 is configured to be approximately horizontal with the central axis of the cylinder of the main body 22 (referred to as the Z-axis). In addition, the central axis of the cylinder of the protrusion 30 (which is the beam axis) extends parallel to the Z-axis in the vertical direction above the Z-axis.

[0087] The vacuum chamber 20 is envisioned to be formed to a length of 35 cm or less in the Z-axis direction, and 20 cm or less in both the X and Y axes. Further miniaturization is also conceivable, with the length in the Z-axis direction set to 30 cm or less, 25 cm or less, or 20 cm or less. Additionally, it is entirely possible to set the lengths in the X and Y axes to 15 cm or less, or 10 cm or less. Furthermore, the distance between the beam axis and the Z-axis is set to, for example, 10 to 20 mm.

[0088] In this embodiment, four legs 38 are provided near the four corners of the lower part of the main body 22 of the vacuum chamber 20 to support the vacuum chamber 20. The vacuum chamber 20 is made of a metal such as SUS (stainless steel) and is made strong enough to withstand the pressure difference when the interior becomes a vacuum. The rear circular wall 28 and the front circular wall 34 of the vacuum chamber 20 are formed in a detachable manner and can be disassembled for maintenance and inspection.

[0089] The atomic furnace 40 is a device disposed near the front end of the protrusion 30. The atomic furnace 40 heats the solid metal it contains with a heater, releasing atoms ejected from the metal due to thermal motion through fine pores, forming an atomic beam 42. The beam axis through which the atomic beam 42 passes is set to be parallel to the Z-axis and to intersect the X-axis at a position slightly away from the origin. The intersection position corresponds to the trapping space 50, described later, which is a tiny space where atoms are trapped. The atomic furnace 40 is essentially disposed inside the vacuum chamber 20, but for cooling, a heat sink extends to the outside of the vacuum chamber 20. In the atomic furnace 40, the metal is heated to, for example, 750K. Examples of metals selected include strontium, mercury, cadmium, and ytterbium, but are not particularly limited to these.

[0090] The Zeeman reducer coil 44 is positioned downstream of the beam axis of the atomic furnace 40, extending from the protrusion 30 of the vacuum chamber 20 to the main body 22. The Zeeman reducer coil 44 is a device that integrates a Zeeman reducer for slowing down the atoms in the atomic beam 42 with a Motion-on-Touch (MOT) device for trapping the slowed atoms. Both the Zeeman reducer and the MOT device are based on atomic laser cooling technology. Figure 2 The Zeeman reducer coil 44 shown is configured as a series of coils, including a Zeeman coil used in the Zeeman reducer and one of a pair of MOT coils used in the MOT device. Although it is not possible to clearly distinguish them, generally speaking, most of the coils from the upstream side to the downstream side correspond to the Zeeman coils that generate the magnetic field that contributes to the Zeeman reduction method, while the downstream side corresponds to the MOT coils that generate the gradient magnetic field that contributes to the MOT method.

[0091] In the illustrated example, the Zeeman coil is a decreasing type, with more turns upstream and fewer turns downstream. The Zeeman decelerator uses coil 44 arranged axially symmetrically around the beam axis so that the atomic beam 42 passes inside the Zeeman and MOT coils. Inside the Zeeman coil, a spatially gradient magnetic field is formed and irradiates the Zeeman deceleration beam 82, thereby decelerating the atoms.

[0092] The optical resonator 46 is a cylindrical component arranged around the Z-axis, with an optical lattice formed inside. Multiple optical components are provided in the optical resonator 46. A bowtie-type optical lattice resonator is generated by multiple reflections of the optical lattice light between a total of four mirrors, including one pair of optical mirrors on the X-axis and another pair parallel to it. The atomic clusters captured in the trapping space 50 are enclosed inside this optical lattice. Furthermore, in the optical resonator 46, a moving optical lattice is formed by shifting the relative frequencies of the two (right-hand and left-hand) optical lattice lights incident on the resonator, causing the standing wave of the optical lattice to move. By moving the optical lattice, the atomic clusters are moved to the clock transition space 52. In this embodiment, an optical lattice containing the moving optical lattice is formed on the X-axis. Alternatively, a two-dimensional or three-dimensional optical lattice can be used, with the lattice arranged not only on the X-axis but also on one or both of the Y and Z axes. Thus, the optical resonator 46 can be referred to as an optical lattice forming part. The optical resonator 46 is also a device based on atomic laser cooling technology.

[0093] The MOT device uses coil 48 to generate a gradient magnetic field in the trapping space 50. In the MOT device, MOT light is irradiated along the three axes (X, Y, Z) in the space where the gradient magnetic field is formed. Thus, the MOT device traps atoms into the trapping space 50. The trapping space 50 is positioned along the X-axis. Figure 2 The Zeeman reducer coil 44 shown is configured as a series of coils, comprising a Zeeman coil used in the Zeeman reducer and one of a pair of MOT coils used in the MOT device. In this figure, the gradient magnetic field that contributes to the MOT method is generated together by a portion of the MOT device coil 48 and the Zeeman reducer coil 44.

[0094] The cryogenic bath 54 is formed to surround the clock transition space 52, maintaining the inner space at a low temperature. Consequently, blackbody radiation is reduced in the inner space. A thermally connected member 56, which also serves as a support structure, is fitted into the cryogenic bath 54. The thermally connected member 56 conducts heat from the cryogenic bath 54 to the refrigerator 58. The refrigerator 58 is a device that cools the cryogenic bath 54 via the thermally connected member 56. The refrigerator 58 includes a Peltier element to cool the cryogenic bath 54 to, for example, 190K.

[0095] The vacuum pump body 60 and vacuum pump cylinder 62 are devices used to vacuum the vacuum chamber 20. The vacuum pump body 60 and vacuum pump cylinder 62 are the devices used for subsequently vacuuming the vacuum chamber 20. The vacuum pump body 60 is located on the outer side of the vacuum chamber 20, and the vacuum pump cylinder 62 is located on the inner side of the vacuum chamber 20. The vacuum pump cylinder 62 is activated by heating from a heater located on the vacuum pump body 60 at startup. Thus, the vacuum pump cylinder 62 is activated, and vacuuming is achieved through the adsorption of atoms.

[0096] The vacuum pump cylinder 62 is arranged side-by-side with the Zeeman reducer coil 44 in the main body 22. The Zeeman reducer coil 44 is arranged along a beam axis that is eccentrically positioned in the X-axis direction relative to the central axis of the cylinder of the main body 22. Therefore, there is a relatively large space on the side opposite to the eccentric direction of the Zeeman reducer coil 44. The vacuum pump cylinder 62 is disposed in this space.

[0097] In the physical package 12, as components of the optical system, there are: vacuum-resistant optical windows 64 and 66 for optical lattice light; vacuum-resistant optical window 68 for MOT light; vacuum-resistant optical windows 70 and 72 for Zeeman deceleration light and MOT light; and optical mirrors 74 and 76.

[0098] Vacuum-resistant optical windows 64 and 66 for optical lattice light are vacuum-resistant optical windows that are oppositely arranged on the cylindrical walls 24 facing each other in the main body 22 of the vacuum chamber 20. The vacuum-resistant optical windows 64 and 66 for optical lattice light are provided for incident and emitted optical lattice light.

[0099] The vacuum-resistant optical window 68 for MOT light is provided to allow the MOT light of two of the three axes used in the MOT device to be incident and emitted.

[0100] The vacuum-resistant optical windows 70 and 72 for Zeeman deceleration light and MOT light are provided to allow the Zeeman deceleration light and the MOT light of one axis to be incident and emitted.

[0101] Optical mirrors 74 and 76 are designed to change the direction of the Zeeman deceleration beam and the MOT beam on one axis.

[0102] In addition, the physical package includes the following components for cooling: a furnace cooler 90, a Zeeman reducer cooler 92, and a MOT device cooler 94.

[0103] The reactor cooler 90 is a water-cooling device for cooling the reactor 40. The reactor cooler 90 is located outside the vacuum chamber 20 and cools the heat dissipation section of the reactor 40 that extends to the outside of the vacuum chamber 20. The reactor cooler 90 has metal water-cooled pipes for cooling, and cools the vacuum chamber 20 by circulating cooling water, which is a liquid refrigerant, inside.

[0104] The Zeeman reducer cooler 92 is a device installed in the wall of the vacuum chamber 20 to cool the Zeeman reducer coil 44. The Zeeman reducer cooler 92 has metal pipes through which cooling water circulates to remove the Joule heat generated in the coil of the Zeeman reducer coil 44.

[0105] The MOT device cooler 94 is a heat dissipation section provided on the circular wall of the vacuum chamber 20. In the MOT device coil 48, the coil generates Joule heat, although this Joule heat is less than that in the Zeeman reducer cooler 92 (for example, about 1 / 10th the amount). Therefore, the metal of the MOT device cooler 94 extends from the MOT device coil 48 to the outside of the vacuum chamber 20, releasing heat into the atmosphere.

[0106] Furthermore, the physical package 12 includes, as a component for correcting the magnetic field, a 3-axis magnetic field correction coil 96, a vacuum-resistant electrical connector 98, an independent magnetic field compensation coil 102 for a refrigeration unit, and an independent magnetic field compensation coil 104 for a nuclear reactor.

[0107] The 3-axis magnetic field correction coil 96 is used to uniformly zero the magnetic field in the clock transition space 52. The 3-axis magnetic field correction coil 96 is formed in a three-dimensional shape to correct the magnetic field in the X, Y, and Z axes. Figure 4 In the example shown, the 3-axis magnetic field correction coil 96 is generally formed into a cylindrical shape. Each coil constituting the 3-axis magnetic field correction coil 96 is formed in a point-symmetrical shape with respect to the clock transition space 52 in the direction of each axis.

[0108] The vacuum-resistant electrical connector 98 is a connector used to supply power to the vacuum chamber 20, and is disposed on the circular wall of the vacuum chamber 20. Power is supplied from the vacuum-resistant electrical connector 98 to the Zeeman reducer coil 44, the MOT device coil 48, and the 3-axis magnetic field correction coil 96.

[0109] The independent magnetic field compensation coil 102 for the refrigeration unit is used to compensate for the leakage magnetic field from the refrigeration unit 58 that cools the cryogenic bath 54. The Peltier element in the refrigeration unit 58 is a high-current device that receives a relatively large current, generating a large magnetic field. Although the magnetic field around the Peltier element is shielded by a highly permeable material, it is not completely shielded, and some of the magnetic field leaks out. Therefore, the independent magnetic field compensation coil 102 for the refrigeration unit is configured to compensate for this leakage magnetic field in the clock transition space 52.

[0110] The independent magnetic field compensation coil 104 for the nuclear reactor is used to compensate for the leakage magnetic field from the heater of the nuclear reactor 40. The heater of the nuclear reactor 40 is also a high-current device, and despite shielding with a high-permeability material, the leakage magnetic field can sometimes not be ignored. For example, even when the heater circuit is constructed using non-inductive winding wiring, inductive components may still remain in the wiring via wiring terminals or insulation layers. Furthermore, even when the nuclear reactor is magnetically shielded by covering it with a high-permeability material, there may still be areas that cannot be effectively covered, such as atomic beam openings. Therefore, the independent magnetic field compensation coil 104 for the nuclear reactor is configured to compensate for this leakage magnetic field in the clock transition space 52.

[0111] (2) Physical encapsulation operations

[0112] The basic operation of the physical package 12 will be explained. In the physical package 12, the vacuum pump cylinder 62 inside the vacuum chamber 20 adsorbs atoms, thereby creating a vacuum inside the vacuum chamber 20. Thus, the interior of the vacuum chamber 20 becomes, for example, 10 - 8 A vacuum state of Pa is achieved, eliminating the influence of air components such as nitrogen and oxygen. Pre-treatment is performed depending on the type of vacuum pump to be used. For example, for non-evaporative getter pumps (NEG pumps) or ion pumps, a rough evacuation to a certain vacuum level is required before operation. In this case, a rough evacuation port is provided in the vacuum chamber beforehand, and a thorough rough evacuation is performed from this port, for example, using a turbomolecular pump. Furthermore, for example, when using an NEG pump as the vacuum pump body 60, an activation process involving heating to a high temperature in a vacuum is required beforehand.

[0113] In the atomic furnace 40, the metal is heated to a high temperature by a heater, generating atomic vapor. During this process, the atomic vapor ejected from the metal continuously passes through a fine pore, converges, and translates to form an atomic beam 42. The atomic furnace 40 is configured such that the atomic beam 42 is formed on a beam axis parallel to the Z-axis. Furthermore, in the atomic furnace 40, the furnace body is heated by a heater, but the furnace body and the joint supporting it are insulated from each other by a thermal insulator, and the joint connected to the physical package is cooled by the furnace cooler 90, preventing or reducing the impact of the high temperature on the physical package 12.

[0114] The Zeeman decelerator coil 44 is configured to be axially symmetrical with respect to the beam axis. The interior of the Zeeman decelerator coil 44 is irradiated with a Zeeman decelerated beam 82 and a one-axis MOT beam 84. The Zeeman decelerated beam 82 is incident through a vacuum-resistant optical window 70 for both the Zeeman decelerated beam and the MOT beam, and is reflected by an optical mirror 74 positioned downstream of the beam compared to the MOT device coil 48. Thus, the Zeeman decelerated beam 82 overlaps with the atomic beam 42 and travels upstream of the beam axis, approximately parallel to it. During this process, due to the Zeeman splitting effect proportional to the magnetic field strength and the Doppler shift effect, the atoms in the atomic beam 42 absorb the Zeeman decelerated beam, are imbued with motion in the deceleration direction, and decelerate. The Zeeman decelerated beam is reflected by an optical mirror 76 placed adjacent to the beam axis upstream of the Zeeman decelerator coil 44 and exits through the vacuum-resistant optical window 72 for both the Zeeman decelerated beam and the MOT beam. Furthermore, although Joule heat is generated in the coil 44 of the Zeeman reducer, it is cooled by the Zeeman reducer cooler 92, thus preventing overheating.

[0115] The sufficiently decelerated atomic beam 42 reaches the MOT device formed by the downstream MOT coil of the Zeeman decelerator coil 44 and the MOT device coil 48. Within the MOT device, a magnetic field with a linear spatial gradient is formed centered on the trapping space 50. Furthermore, MOT light is irradiated onto the MOT device from both the positive and negative sides in three axial directions.

[0116] The MOT beam 84 along the Z-axis illuminates in the negative direction of the Z-axis, and is thus reflected outside the vacuum-resistant optical window 72 used for Zeeman deceleration and MOT beams, thereby also illuminating in the positive direction of the Z-axis. The remaining two MOT beams 86a and 86b are illuminated into the MOT device using the vacuum-resistant optical window 68 for MOT beams and an optical mirror (not shown). Figure 4 As shown, these two axes are irradiated in two directions perpendicular to the Z-axis and forming 45-degree angles with the X and Y axes, respectively. By setting the two MOT beams 86a and 86b perpendicular to the Z-axis, the interval between the Zeeman reducer coil 44 and the MOT device coil 48 can be narrowed, which helps to miniaturize the vacuum chamber 20. When the direction of the irradiating MOT beam is set to form 45-degree angles with the Z and Y axes, a large distance needs to be ensured in the beam axis direction to prevent the MOT beam from interfering with the Zeeman reducer or cryogenic chamber. In this case, the size of the device will be larger compared to the case where the two axes of the MOT beam are perpendicular to the Z-axis.

[0117] Within the MOT device, due to the magnetic field gradient, the atomic beam is decelerated by a restoring force centered on the trapping space 50. Thus, the atomic clusters are trapped within the trapping space 50. Furthermore, the position of the trapping space 50 can be fine-tuned by adjusting the offset value of the magnetic field generated by the 3-axis magnetic field correction coil 96. Additionally, the Joule heat generated in the MOT device coil 48 is discharged outside the vacuum chamber 20 via the MOT device cooler 94.

[0118] An optical lattice beam 80 is incident along the X-axis from a vacuum-resistant optical window 64 towards a vacuum-resistant optical window 66. An optical resonator 46 with two optical mirrors is positioned along the X-axis to induce reflection. Therefore, a standing wave is formed inside the optical resonator 46 along the X-axis, creating an optical lattice potential that extends in the X-axis direction. Atom clusters are trapped by this optical lattice potential.

[0119] By slightly altering the wavelength, the optical lattice can be moved along the X-axis. Through the moving unit formed by this moving optical lattice, the atomic clusters are moved to the clock transition space 52. As a result, the clock transition space 52 deviates from the beam axis of the atomic beam 42, thus eliminating the influence of blackbody radiation emitted by the high-temperature atomic furnace 40. Furthermore, the clock transition space 52 is surrounded by a cryogenic chamber 54, shielding it from blackbody radiation emitted by the surrounding room-temperature matter. Generally, since blackbody radiation is proportional to the fourth power of the absolute temperature of matter, the cryogenic treatment brought about by the cryogenic chamber 54 has a significant effect on eliminating the influence of blackbody radiation.

[0120] In the clock transition space 52, atoms are irradiated with a frequency-controlled laser, and high-precision beam splitting (i.e., resonant transition of the atom that becomes the reference for the clock) is performed to measure the inherent and unchanging frequency of the atom. Thus, an accurate atomic clock is achieved. To improve the accuracy of the atomic clock, it is necessary to eliminate disturbances around the atoms and accurately read the frequency. Particularly important is to eliminate the frequency shift caused by the Doppler effect due to the thermal motion of the atoms. In an optical lattice clock, the motion of the atoms is frozen by using an optical lattice generated by the interference of the laser to enclose the atoms in a space much smaller than the wavelength of the clock laser. On the other hand, within the optical lattice, the frequency of the atoms deviates due to the laser forming the optical lattice. Therefore, as the optical lattice beam 80, the influence of the optical lattice on the resonant frequency is eliminated by selecting a specific wavelength and frequency called the "magic wavelength" or "magic frequency".

[0121] Clock transitions are also affected by magnetic fields. Since atoms in a magnetic field cause Zeeman splitting corresponding to the strength of the magnetic field, clock transitions cannot be accurately measured. Therefore, magnetic field correction is performed in the clock transition space 52 to homogenize and reduce the magnetic field to zero. First, the leakage magnetic field caused by the Peltier element of the refrigerator 58 is dynamically compensated by an independent magnetic field compensation coil 102 for the refrigerator, which generates a compensation magnetic field corresponding to the magnitude of the leakage magnetic field. Similarly, the leakage magnetic field caused by the heater of the furnace 40 is set to be dynamically compensated by an independent magnetic field compensation coil 104 for the furnace. Furthermore, regarding the Zeeman reducer coil 44 and the MOT device coil 48, the current signal is cut off at the timing of measuring the frequency of the clock transition, thus protecting them from the influence of magnetic fields. The magnetic field of the clock transition space 52 is further corrected by a 3-axis magnetic field correction coil 96. Multiple 3-axis magnetic field correction coils 96 are arranged in the directions of each axis, which can remove not only the same components of the magnetic field but also components that change spatially.

[0122] In this way, under interference-free conditions, the laser induces a clock transition in the atomic clusters. The light emitted as a result of the clock transition is received by an optical system device, and the frequency is determined by the control device through beam splitting and other processes. The implementation of the physical package 12 will be described in detail below.

[0123] (3) Shape and setting of the magnetic field correction coil

[0124] Reference Figures 5-11 The 3-axis magnetic field correction coil 96 in the physical package 12 will be explained. Here, it is envisioned that the 3-axis magnetic field correction coil 96 is formed into a specified shape by winding a coated wire, which has been insulated by polyimide resin or the like, around a conductor such as copper.

[0125] Figure 5 This is a perspective view showing all the coils of the 3-axis magnetic field correction coil 96. Additionally, Figures 6 to 11 This is a perspective view showing the individual coils constituting the 3-axis magnetic field correction coil. The 3-axis magnetic field correction coil 96 is mounted near the inner wall of the main body 22 of the vacuum chamber 20. Therefore, the 3-axis magnetic field correction coil 96 is formed in a generally cylindrical shape centered on the clock transition space 52. The 3-axis magnetic field correction coil 96 is formed by a first coil group and a second coil group in the directions of the X-axis, Y-axis, and Z-axis, respectively.

[0126] Figure 6This diagram shows the first coil group 120 along the X-axis direction (the direction in which the optical lattice forms one axis, and the direction of movement of the optical lattice). The first coil group 120 includes two coils 122 and 124 separated by a distance c along the X-axis direction with the clock transition space 52 as the center. Both coils 122 and 124 are formed as rectangles with a side length of a in the Y-axis direction and a side length of b in the Z-axis direction. In addition, coils 122 and 124 are formed in a shape symmetrical with respect to the clock transition space 52.

[0127] The first coil group 120 forms coils 122 and 124 as square Helmholtz coils to generate a substantially uniform magnetic field in the X-axis direction at the center. A square Helmholtz coil refers to coils 122 and 124 formed as squares with a = b and c / 2a = 0.5445. Coils 122 and 124 are a pair of Helmholtz coils that generate a highly uniform magnetic field in the X-axis direction when the same magnitude of current flows in the same direction. However, in the embodiment, currents of different magnitudes and directions can flow through coils 122 and 124. Furthermore, the uniformity of the magnetic field can be sufficiently improved when coils 122 and 124 are set to a ≠ b. When a > b, the deviation of the magnetic field distribution in the Y-axis direction tends to be smaller than the deviation in the Z-axis direction; when a < b, the deviation of the magnetic field distribution in the Z-axis direction tends to be smaller than the deviation in the Y-axis direction. When a≠b, the Helmholtz coil optimized for c is called a rectangular Helmholtz coil. The first coil group 120 can also be set as a rectangular Helmholtz coil.

[0128] The first coil group 120 is used to adjust the value of the magnetic field component in the X-axis direction and the spatial first-order differential term in the X-axis direction. First, 1) when the same magnitude of current flows through coils 122 and 124 in the same direction, a uniform magnetic field with almost no gradient in the X-axis direction is generated in the clock transition space 52. On the other hand, 2) when the same magnitude of current flows through coils 122 and 124 in opposite directions, a magnetic field with approximately the same gradient in the X-axis direction is formed in the clock transition space 52. Furthermore, by appropriately changing the magnitude and direction of the current flowing through coils 122 and 124, a magnetic field consisting of the linear sum of 1) and 2) is formed. Therefore, the first coil group 120 can correct the constant term component and the spatial first-order differential term in the X-axis direction of the magnetic field component Bx in the clock transition space 52.

[0129] Figure 7This diagram shows the second coil group 130 in the X-axis direction. The second coil group 130 includes two coils 132 and 134 separated in the X-axis direction with the clock transition space 52 as the center. The coils 132 and 134 are formed such that the square coils are curved and deformed on the same cylindrical surface with radius e, the central angle is set to f, and the height in the Z-axis direction is set to g. This cylindrical surface is formed with a fixed... Figure 6 The first coil group 120 has a cylindrical surface with approximately the same radius, therefore, it is e. 2 ≈(a / 2) 2 +(c / 2) 2 The relationship is as follows. In addition, coils 132 and 134 are formed in a shape that is symmetrical with respect to the clock transition space 52 points.

[0130] The second coil group 130 is a non-Helmholtz type coil with a different shape from the Helmholtz coil. Furthermore, coils 132 and 134 of the second coil group are electrically connected and carry the same magnitude of current in the same direction. That is, in coils 132 and 134, current flows either in the direction of arrow 136 or in the direction of arrow 138. Since the second coil group 130 is a non-Helmholtz type coil, in addition to generating the same components as those of a Helmholtz coil in the clock transition space 52, different components are also generated. However, since the magnitude and direction of the current are the same, the different components are mainly the components of the second-order spatial differential. That is, the second coil group 130 can correct the constant term component and the second-order spatial differential term in the X-axis direction of the magnetic field component Bx in the clock transition space 52.

[0131] The magnetic field component Bx in the X-axis direction of the 3-axis magnetic field correction coil 96 is essentially controlled by the first coil group 120 and the second coil group 130 in the X-axis direction. Therefore, they are collectively referred to as the X-axis magnetic field correction coil. During correction, firstly, the value of the spatial second-order differential term in the X-axis direction is returned to zero through the second coil group 130. Next, the value of the spatial first-order differential term in the X-axis direction is returned to zero through the first coil group 120, and the value of the constant term in the X-axis direction is also adjusted to zero.

[0132] Figure 8This diagram shows the first coil group 140 in the Y-axis direction. The first coil group 140 is formed by deforming square coils in a curved manner and placing them on a cylindrical surface of radius h centered on the clock transition space 52. In the first coil group, composite coils 142 and 145 are separately arranged in the Y-axis direction. Composite coil 142 includes coils 143 and 144, and composite coil 145 includes coils 146 and 147. The center angle of coils 143, 144, 146, and 147 is set to i, and their height in the Z-axis direction is set to j. Coils 143 and 144 are formed such that their end edges overlap or are adjacent to each other. Similarly, coils 146 and 147 are formed such that their end edges overlap or are adjacent to each other. Composite coils 142 and 145 are formed in a point-symmetric manner about the clock transition space 52. In addition, coils 143 and 146, as well as coils 144 and 147, are also formed in a point-symmetric manner with the clock transition space 52 as the center.

[0133] First, consider the case where coils 143 and 144 have the same current flowing in the same direction. In this case, the currents in the overlapping or adjacent portions cancel each other out, and the composite coil 142 operates as a single large coil. Similarly, when coils 146 and 147 also have the same current flowing in the same direction, the composite coil 145 operates as a single large coil. The first coil group 140 is configured such that composite coils 142 and 145 are a pair of Helmholtz-type coils. Figure 8 The Helmholtz coil shown on the cylindrical surface (i.e., a Helmholtz coil formed by bending two square coils and arranging them on the same cylindrical surface) refers to a Helmholtz coil with a central angle set at approximately 120 degrees. The length in the Z-axis direction is not particularly limited, but it is known that the longer the Z-axis length compared to the radius of the cylinder, the higher the magnetic field uniformity at the center. The first coil group 140 can homogenize the Y-axis component of the magnetic field near the center by adjusting the direction and magnitude of the current flowing through it.

[0134] Next, 4) the current in the case of forming the Helmholtz coil is slightly modified. Specifically, the current in coils 143 and 147 is slightly increased in the same direction. In this case, the Y-axis component of the magnetic field will have the value of the first spatial differential term in the X-axis direction. Furthermore, strictly speaking, the magnetic field generated by coils 143 and 147 also has an X-axis component, and when adjusting the first coil group 140, the X-axis magnetic field correction coil also needs to be adjusted.

[0135] Figure 9 This is a diagram showing the second coil group 150 in the Y-axis direction. Figure 9The second coil group 150 shown includes a pair of coils 152 and 154 facing each other in the Y-axis direction. Coils 152 and 154 are non-Helmholtz coils formed with a circular coil of radius k having curvature and situated on a cylindrical surface of radius l centered on the clock transition space 52. In the non-Helmholtz coils, the spatial second-order differential term of the magnetic field is also formed. Therefore, the second coil group 150 is used to control the spatial second-order differential term of the magnetic field component By in the Y-axis direction in the X-axis direction.

[0136] Figure 8 The first coil group 140 shown in the Y-axis direction and Figure 9 The second coil group 150 shown in the Y-axis direction essentially forms a Y-axis magnetic field correction coil for correcting the magnetic field component By in the Y-axis direction. The Y-axis magnetic field correction coil can correct the constant term, the first spatial differential term, and the second spatial differential term of the magnetic field component By in the Y-axis direction.

[0137] Figure 10 This diagram shows the first coil group 160 along the Z-axis. The first coil group 160 is configured such that circular composite coils 162 and 165, each with a radius of m, are spaced apart by a distance n. The composite coils 162 and 165 are point-symmetrical about their center. Furthermore, the composite coil 162 is formed by overlapping or placing adjacent semicircular coils 163 and 164. The semicircular coil 163 is positioned on the positive side of the X-axis, and the semicircular coil 164 is positioned on the negative side of the X-axis. Similarly, the composite coil 165 is formed by combining a semicircular coil 166 located on the positive side of the X-axis with a semicircular coil 167 located on the negative side of the X-axis.

[0138] The dimensions of the composite coils 162 and 165 are set to make them Helmholtz-type coils. A circular Helmholtz coil is in the relationship m=n. The composite coils 162 and 165 are set such that, when the same magnitude of current flows through them in the same direction, the uniformity of the magnetic field in the Z direction near the center is substantially equivalent to that of a Helmholtz coil. However, in the coils 163 and 164 constituting the composite coil 162, the direction and magnitude of the current can be freely changed. Therefore, with... Figure 8 Similarly, the first coil group 160 in the Y direction can correct the constant term of the magnetic field component Bz in the Z direction and the spatial first-order differential term in the X-axis direction.

[0139] Figure 11This diagram shows the second coil group 170 in the Z-axis direction. In the second coil group 170, circular coils 172 and 174 of radius p are arranged opposite each other, separated by a distance q in the Z-axis direction. The second coil group 170 is a non-Helmholtz coil. In a non-Helmholtz coil, there is a different composition. Therefore, it is possible to correct the spatial second-order differential term of the magnetic field component Bz in the Z-axis direction in the X-axis direction.

[0140] Figure 10 The first coil group 160 shown in the Z-axis direction and Figure 11 The second coil group 170 shown in the Z-axis direction essentially forms a Z-axis magnetic field correction coil for correcting the magnetic field component Bz in the Z-axis direction. The Z-axis magnetic field correction coil can correct the constant term, the first spatial differential term, and the second spatial differential term of the magnetic field component Bz in the Z-axis direction.

[0141] Figure 5 The 3-axis magnetic field correction coil 96 shown is formed by combining and controlling an X-axis magnetic field correction coil, a Y-axis magnetic field correction coil, and a Z-axis magnetic field correction coil. The 3-axis magnetic field correction coil 96 can correct the constant term, the first-order spatial differential term, and the second-order spatial differential term for the magnetic field component Bx in the X-axis direction. For the magnetic field component By in the Y-axis direction, it can correct the constant term, the first-order spatial differential term, and the second-order spatial differential term. Furthermore, for the magnetic field component Bz in the Z-axis direction, it can correct the constant term, the first-order spatial differential term, and the second-order spatial differential term.

[0142] In the 3-axis magnetic field correction coil 96, a correction is performed to uniformly reduce the value of the magnetic field in the clock transition space 52 to zero. In the one-dimensional optical lattice, the clock transition space 52 is, for example, set to a size of 10 mm in the X-axis direction (lattice direction) and 1–2 mm in the Y and Z-axis directions. The magnetic field for this space is controlled to, for example, an error within 3 μG, 1 μG, or 0.3 μG. The precision of the Helmholtz-type and non-Helmholtz-type coils used in the 3-axis magnetic field correction coil 96 is set to enable the formation of this magnetic field.

[0143] like Figure 4As shown, the 3-axis magnetic field correction coil 96 is formed with point symmetry around the clock transition space 52, enabling precise magnetic field correction of the clock transition space 52. However, from a macroscopic perspective, the capture space 50 also exists near the center of the 3-axis magnetic field correction coil. Therefore, it can also be used to correct the magnetic field of the capture space 50 generated by the MOT device. That is, during the period when the MOT device is activated to capture atoms from the atomic beam 42, the current is controlled to perform magnetic field correction of the capture space 50. Furthermore, after capture, simply stop supplying power to the Zeeman reducer coil 44 and the MOT device coil 48 and perform magnetic field correction of the clock transition space 52. In this way, the position of the capture space 50 can be adjusted with high precision, efficiently enclosing the atomic clusters within the optical lattice.

[0144] Figure 12 This diagram shows a cylindrical holder 180 for mounting a 3-axis magnetic field correction coil 96. The holder 180 is formed by connecting annular frames 182 and 184 with eight straight frames 186. The 3-axis magnetic field correction coil 96 is mounted on the inner and outer walls of the holder 180. Furthermore, the holder 180 is fixed to the rear circular wall 28 of the main body 22 of the vacuum chamber 20. By mounting the 3-axis magnetic field correction coil 96 to the holder 180, the assembly and maintenance inspection of the physical package 12 become highly efficient.

[0145] The retainer 180 is formed using resin, aluminum, or other materials with low magnetic permeability to avoid affecting the magnetic field generated by the 3-axis magnetic field correction coil 96. Furthermore, the retainer 180 is coaxially disposed inside the main body 22 with the central axis of the cylinder. The retainer 180 is formed to a size similar to the inner diameter of the main body 22. Therefore, the 3-axis magnetic field correction coil 96 and the retainer 180 occupy almost no space inside the main body 22. However, the coils 122 and 124 of the first coil group 120 in the X-axis direction are assembled in a straight line, traversing the inner side of the main body 22.

[0146] The retainer 180 is formed into a sparse structure using a frame. A sparse structure refers to a structure with many gaps between the surfaces. By making the retainer 180 a sparse structure, in addition to reducing weight, it is also easier to prevent interference with lasers incident on or emitted from the vacuum chamber 20.

[0147] The 3-axis magnetic field correction coil 96 can be entirely mounted on the inner wall of the retainer 180, or entirely mounted on the outer wall of the retainer 180, instead of being separately mounted on the inner and outer walls of the retainer 180. In this case, for example, it can be easily fixed using a ring-shaped fastener that presses the 3-axis magnetic field correction coil 96 against the outer wall or a ring-shaped fastener that presses the 3-axis magnetic field correction coil 96 against the inner wall. Alternatively, the 3-axis magnetic field correction coil 96 can also be fixed to the inner wall of the main body 22 without using the retainer 180.

[0148] It is envisioned that the 3-axis magnetic field correction coil 96 shown above is formed by winding the covering wire one or more times. However, part or all of the 3-axis magnetic field correction coil 96 can be formed from a flexible printed circuit board.

[0149] Figure 13 This diagram shows a flexible printed circuit board unfolded on a plane. A correction coil 190 is formed on the flexible printed circuit board. The correction coil 190 includes: a current path 192, which is composed of a printed conductive material such as copper, participating in the formation of a magnetic field; and an insulating portion 194, which is formed of a sheet-like flexible resin, etc. The correction coil 190 is flexibly bendable. Each current path 192 is connected to a wiring path 196 centrally located at one end. The wiring path 196 is also formed by printing conductive material. The wiring path arranges a pair of adjacent current paths that supply current back and forth, canceling out the magnetic field formed around them. The wiring path 196 is connected to a terminal connector 198.

[0150] Figure 14 This diagram shows a calibration coil 190 bent into a cylindrical shape to match the main body 22 of the vacuum chamber 20. The calibration coil 190 has two boundary portions 199 formed by connecting or arranging their end edges adjacent to each other. Furthermore, in... Figure 14 In the original text, wiring path 196 and terminal connector 198 are omitted.

[0151] It is envisioned that, similar to the aforementioned 3-axis magnetic field correction coil 96 formed by winding coated wires, a 3-axis magnetic field correction coil made of a flexible printed circuit board is also mounted on the cylindrical inner wall of the main body 22 or the cylindrical retainer 180. However, in the 3-axis magnetic field correction coil 96, in addition to the current path disposed on the cylindrical surface, there is also a current path detached from the cylindrical surface. Specifically, Figure 6 The side of length a in the first coil group 120 in the X-axis direction shown, and Figure 10 The straight portion of the first coil group 160 in the Z-axis direction shown is detached from the cylindrical surface. Therefore, the following description will illustrate an example where the current path in the current path constituting the 3-axis magnetic field correction coil 96, arranged on the cylindrical surface, is formed by a flexible printed circuit board.

[0152] Figure 15 and Figure 16 It is shown Figure 10 The diagram shows an example of a coil formed from a flexible printed circuit board in the circular portion of the first coil group 160 along the Z-axis direction. Figure 15 As shown, the current path 202 (black line) carries a counter-clockwise current, while the current path 200 (gray line) carries no current. Considering that adjacent currents flowing in opposite directions cancel each other out, this can be considered... Figure 16 The current flowing through the hypothetical current path 203 shown is equivalent.

[0153] Figure 17 and Figure 18 It is shown Figure 8 The diagram shows an example where the outermost coil in the first coil group 140 along the Y-axis is formed from a flexible printed circuit board. Figure 17 In the diagram, current flows counterclockwise in the black current path 206, while no current flows in the gray current path 204. Considering that adjacent currents flowing in opposite directions cancel each other out, this can be considered... Figure 18 The current flowing through the hypothetical current path 208 shown is equivalent.

[0154] In this way, various current paths can be formed in the flexible printed circuit board, such as current paths that flow back around the central axis of the cylinder along the outer periphery of the cylinder surface, and current paths that flow back inside the cylinder surface without flowing around the central axis of the cylinder.

[0155] In flexible printed circuit boards, such as Figure 13 In this way, a pattern consisting of rectangular current paths can be printed in the unfolded diagram. Additionally, it is also possible to... Figure 19 As shown in the calibration coil 210, a composite pattern including rectangular current paths 212 and circular current paths 214 is printed. In the physical package 12, since laser paths, vacuum-resistant optical windows, etc., are located near the walls of the vacuum chamber 20, providing circular current paths 214 to prevent interference is effective. Furthermore, in a flexible printed circuit board, a similar pattern can also be formed. Figure 16 , Figure 18 The coil is as shown. Furthermore, multiple flexible printed circuit boards can be stacked together to form part or all of a 3-axis magnetic field correction coil.

[0156] In flexible printed circuit boards, trace amounts of gas may sometimes be released from the resin in the insulating portion 194. Therefore, the insulating portion 194 is made of a material with low gas release, such as a polyimide-based resin. In addition, in the manufacturing process, besides degassing, defoaming, and cleaning, drying at an appropriate temperature can be considered.

[0157] The 3-axis magnetic field correction coil formed from the flexible printed circuit board can be disposed in the vacuum chamber 20 in various forms. For example, the 3-axis magnetic field correction coil can be disposed in the main body 22 near the inner wall surface in a bent cylindrical shape and fixed by fasteners pressing the 3-axis magnetic field correction coil against the main body 22. Alternatively, it can be mounted on the retainer 180. Alternatively, instead of using the sparsely structured retainer 180, a densely structured retainer with few holes on its surface can be used to provide surface support for the flexible printed circuit board.

[0158] On the other hand, the current path detached from the cylindrical surface can be formed separately using a covered conductor. Alternatively, by changing the structure of the retainer, the current path detached from the cylindrical surface can also be formed using a flexible printed circuit board.

[0159] Compared to the 3-axis magnetic field correction coil 96, which is made by winding the wrapped wire, the 3-axis magnetic field correction coil using a flexible printed circuit board has advantages such as high manufacturing reproducibility and improved product yield, in addition to being easier to install into the vacuum chamber 20.

[0160] Furthermore, the coil shape of the 3-axis magnetic field correction coil can be set in various other ways. For example, a Maxwell-type 3-axis magnetic field correction coil can be formed by arranging a large circular coil between two circular coils on each of the three axes. The Maxwell-type 3-axis magnetic field correction coil can correct the constant term, the first-order spatial differential term, and the second-order spatial differential term of the magnetic field.

[0161] Furthermore, by arranging small circular coils of a predetermined size and spacing outside a pair of large circular coils arranged at predetermined sizes and intervals on each of the three axes, it is possible to form a tetra-type three-axis magnetic field correction coil. In this tetra-type three-axis magnetic field correction coil, corrections can be performed on the components of the constant term, the first-order spatial differential term, the second-order spatial differential term, and the third-order spatial differential term.

[0162] The 3-axis magnetic field correction coil shown above has an overall spherical shape or a slightly deformed spherical shape. Therefore, it can effectively utilize the internal space of the vacuum chamber, especially by mounting it on or near the inner wall of a roughly spherical vacuum chamber.

[0163] Figure 20 Is with Figure 4 The corresponding diagram is a schematic representation of the external appearance and internal structure of the physical package 218. For comparison with... Figure 4 The same or corresponding components are labeled with the same reference numerals. The vacuum chamber 220 of the physical package 218 is formed by a generally spherical main body 222 and a protrusion 30.

[0164] Inside the main body 222, a three-axis magnetic field correction coil 224 formed by circular coils is arranged centered on the clock transition space 52. For the sake of simplicity in the accompanying drawings, ... Figure 20 In the diagram, only one pair of Helmholtz-type coils is shown in each axis direction, but in reality, it is envisioned that one or more pairs of non-Helmholtz-type coils be further provided on each axis. The outer edge of the 3-axis magnetic field correction coil 224 can be set to be approximately spherical. Therefore, by placing it near the inner wall of the approximately spherical main body 222, interference with other components located in the internal space of the main body 222 can be prevented, and the design freedom is also increased.

[0165] Similarly, 3-axis magnetic field correction coils can also be constructed using square coils. Similar to circular coils, it is possible to use Helmholtz-type 3-axis magnetic field correction coils using one pair of square coils, Maxwell-type 3-axis magnetic field correction coils using three square coils, and four-column 3-axis magnetic field correction coils using two pairs of square coils, etc. These 3-axis magnetic field correction coils have an overall cubic shape or a slightly deformed cube shape. Therefore, by mounting them on the inner wall or inner surface of a vacuum chamber that is approximately cubic or approximately cuboid in shape, the internal space of the vacuum chamber can be effectively utilized.

[0166] The 3-axis magnetic field correction coil can also be mounted closer to the clock transition space 52 than the inner wall of the main body 22. Figure 21 It is a simplified representation. Figure 1 The diagram shows the area near the inner side of the optical resonator 46. However, in Figure 21 In this configuration, a cubic 3-axis magnetic field correction coil 230 is installed in the space between the Zeeman reducer coil 44 and the MOT device coil 48 to replace... Figure 1 The 3-axis magnetic field correction coil 96. The 3-axis magnetic field correction coil 230 is arranged centered on the clock transition space 52 inside the cryogenic bath 54. The 3-axis magnetic field correction coil 230 is formed by two pairs of coil groups, each including a square coil, in each of the three axes. One pair of coil groups is a Helmholtz coil, and the other pair is a non-Helmholtz coil. The 3-axis magnetic field correction coil 230 can compensate for magnetic field components up to the third-order spatial differential term without particularly limiting the magnitude and direction of the current. Alternatively, in such cases... Figures 5-11 The 3-axis magnetic field correction coil 96 shown, when the same current flows in the same direction as a non-Helmholtz type coil, can easily compensate for the magnetic field components up to the second-order spatial differential term.

[0167] 3-axis magnetic field correction coil 230 and Figures 5-11The 3-axis magnetic field correction coil 96 shown is very small and located close to the clock transition space 52. Therefore, the magnetic field formed in the clock transition space 52 changes at a relatively small spatial scale. However, the 3-axis magnetic field correction coil 230 can compensate for the constant term and the first-order spatial differential term over a relatively wide range using a Helmholtz-type coil. Furthermore, using a non-Helmholtz-type coil, at least the second-order spatial differential term of the magnetic field can also be compensated. Therefore, the magnetic field of the clock transition space 52 is uniformly zeroed with sufficiently high accuracy. Additionally, because the 3-axis magnetic field correction coil 230 is located close to the clock transition space 52, the current flowing to form the magnetic field is very small, resulting in excellent power efficiency.

[0168] Figure 22 From Figure 21 The side view viewed from direction A. For example... Figure 22 As shown, the capture space 50 is illuminated by two MOT beams 86a and 86b, which are perpendicular to the Z-axis and form 45-degree angles with the X-axis and Y-axis, respectively. Additionally, an MOT beam 84 is also illuminated in a direction perpendicular to the plane of the paper. To adjust the gradient magnetic field formed in and around the capture space 50, a bias coil 234 is arranged centered on the capture space 50. The bias coil 234 includes: a pair of Helmholtz-type circular coils 234a facing each other along the beam axis, a pair of Helmholtz-type square coils 234b facing each other along the X-axis, and a pair of Helmholtz-type square coils 234c facing each other along the Y-axis. The bias coil 234 corrects the gradient magnetic field to the desired distribution by adjusting the constant term components or the components of the first-order spatial differential term using the coils along each axis.

[0169] A light lattice beam 80 is irradiated along the X-axis passing through the capture space 50. A cryogenic tank 54 containing a clock transition space 52 is disposed on the light lattice beam 80. Furthermore, a three-axis magnetic field correction coil 230 is disposed around the cryogenic tank 54, centered on the clock transition space 52. The three-axis magnetic field correction coil 230 consists of a coil group 230b and two coil groups 230a and 230c, wherein the normal of the surface of the coil group 230b is parallel to the Z-axis, and the normals of the surfaces of the two coil groups 230a and 230c are perpendicular to the Z-axis and form a 45-degree angle with the X-axis and Y-axis. That is, the three-axis magnetic field correction coil 230 is configured such that the cubic shape along the X-axis, Y-axis, and Z-axis is rotated 45 degrees around the Z-axis.

[0170] The 3-axis magnetic field correction coil 230 is supported by flanges 44a and 48a, which serve as support members for the MOT device. Therefore, the 3-axis magnetic field correction coil 230 needs to be configured close to the capture space 50, which is the center of the MOT device. On the other hand, the 3-axis magnetic field correction coil 230 needs to be configured to avoid interference with the MOT beams 86a and 86b passing through the capture space 50. Therefore, the 3-axis magnetic field correction coil 230 is configured along the Z-axis and in a shape consistent with the MOT beams 86a and 86b.

[0171] The 3-axis magnetic field correction coil 230 has Helmholtz-type and non-Helmholtz-type coils in each axis direction, enabling wide-space magnetic field homogenization that includes correction of higher-order spatial differential terms. Therefore, the magnetic field can also be corrected with high precision in the X-axis direction, which is the direction of the optical lattice beam 80.

[0172] However, since the 3-axis magnetic field correction coil 230 does not surround the capture space 50, magnetic field correction of the capture space 50 cannot be performed. Therefore, as described above, a bias coil 234 for correcting the gradient magnetic field is provided in the capture space 50.

[0173] exist Figure 20 and Figure 21 The example given is a 3-axis magnetic field correction coil 230 composed of square coils. However, it is also possible to use coils of other shapes, such as circular coils, instead of square coils. Additionally, it is also possible to use... Figures 5-11 The cylindrical 3-axis magnetic field correction coil 96 is shown.

[0174] The 3-axis magnetic field correction coil can also be positioned near the clock transition space 52 and near the inner wall of the main body 22. For example, a Helmholtz-type coil can be positioned near the inner wall of the main body 22, and a non-Helmholtz-type coil can be positioned near the clock transition space 52. By positioning a non-Helmholtz-type coil near the clock transition space 52, correction of magnetic fields with large curvatures can be easily achieved.

[0175] (4) Adjustment of the magnetic field correction coil

[0176] The adjustment of the magnetic field of the 3-axis magnetic field correction coil is explained. Regarding magnetic field correction, the periodic magnetic field distribution around the clock transition space 52 is observed. When the magnetic field distribution is uneven, the current in the 3-axis magnetic field correction coil 96 is operated to cancel it out. The magnetic field distribution is observed by moving the atomic clusters enclosed within the optical lattice. Through these operations, the state in which each atom within the atomic cluster is always under the same zero magnetic field is demonstrated.

[0177] Figure 23A and Figure 23BThis diagram schematically illustrates the adjustment process of a 3-axis magnetic field correction coil. Figure 23A The diagram shows the state in which the atomic cluster 240 enclosed in the moving optical lattice is moved along the X-axis. Additionally, Figure 23B The relationship between fluorescence transitions and clock transitions is shown.

[0178] like Figure 23A As shown, the atomic cluster 240 is enclosed in a lattice extending along the X-axis in a manner with a certain degree of spatial expansion. In the figure, the representative X-coordinate positions of the movement of the atomic cluster 240 are represented as position X1, position X2, position X3, position X4, position X5, and so on. These are positions set within a calibration space 242, which is set for the calibration of the magnetic field. The calibration space 242 is set to encompass a wide range including the clock transition space 52 where the actual measurement is performed. In this embodiment, since a one-dimensional lattice extending along the X-axis is used, and the atomic cluster 240 is distributed in an expanded manner along the X-axis, the goal is specifically to bring the magnetic field in the X-axis direction to zero with high precision. Therefore, the calibration space 242 is set to have an expansion in the X-axis direction. Furthermore, when the optical lattice is formed in two dimensions, it is desirable to set up a correction space that extends the clock transition space 52 in the two-dimensional direction; when the optical lattice is formed in three dimensions, it is desirable to set up a correction space that extends the clock transition space 52 in the three-dimensional direction.

[0179] At each position within the corrected space 242, after relocation, lasers are used to excite clock transitions in the atomic cluster 240. The frequency of the laser is scanned, and the frequency of the clock transition at each position is measured. The excitation rate of the clock transition is observed using the electron shelving method. In the electron shelving method, after the clock transition is excited, the atoms are moved to the fluorescence observation space 243. Figure 23B As shown, when light is irradiated during a fluorescence transition, the atoms emit fluorescence 244 according to their excitation rate, and the fluorescence is observed by a photodetector 246. The clock transition undergoes Zeeman splitting based on the magnitude of the magnetic field at each position. Therefore, the magnetic field distribution at each position can be determined based on the information from the Zeeman splitting. Figure 23A The lower part shows the frequency distribution on the X-axis obtained in this way. Using this method, magnetic fields can be measured even in places where fluorescence cannot be observed (such as inside a cryohead). Furthermore, the excitation rate of clock transitions can be measured not only using the electron placement method but also using non-destructive methods that utilize atomic phase shift measurements.

[0180] Figure 24 and Figure 25 This is a flowchart illustrating the magnetic field correction steps of a 3-axis magnetic field correction coil. First, according to... Figure 24 The steps shown are for calibration. During calibration, the current to all coils constituting the 3-axis magnetic field correction coil is stopped (set to 0A), and the magnetic field distribution in the three axes is measured (S10). In this magnetic field measurement, a magnetic sensor such as a small coil or Hall element is used to measure the magnetic field in the three axes. The measured magnetic field represents the background value without using the 3-axis magnetic field correction coil. Next, a current of the same magnitude is passed through each of the coils (let's say n coils) sequentially (in... Figure 24 The magnetic field distribution along the three axes is measured using a magnetic field sensor (S12~S18). By subtracting the background magnetic field from the obtained magnetic field distribution, the basic magnetic field formed by each coil with a current of 1A can be obtained.

[0181] In this calibration, the magnetic field of the calibration space 242 can also be measured. However, since the calibration space 242 is located in the cryogenic bath 54, setting up the magnetic sensor may not be easy. Therefore, the magnetic field can also be measured near the calibration space 242 and combined with the results of electromagnetic field simulation to estimate the magnetic field. The magnetic field measurement can also be performed in the atmosphere instead of in a vacuum. Thus, the basic magnetic field distribution formed by each coil of the 3-axis magnetic field correction coil with a current of 1A can be determined. In principle, this calibration only needs to be performed once during the creation of the physical package 12.

[0182] Next, according to Figure 25 The magnetic field is corrected according to the steps shown. First, as described above, the atomic cluster 240 is moved using a moving optical lattice, and the frequency of clock transitions at each position in the correction space 242 is measured (S20). Then, the magnetic field distribution in the correction space 242 is determined by estimating the effect of Zeeman splitting (S22). This magnetic field distribution is obtained as the absolute value of the magnetic field.

[0183] Next, optimization techniques such as the least squares method are used to determine the current corresponding to the magnetic field corrected by each coil (S24). That is, a superposition coefficient is found such that the magnetic field formed in the correction space 242 becomes zero when the basic magnetic fields formed by each coil are superimposed. Furthermore, as mentioned above, when using both Helmholtz-type and non-Helmholtz-type coils, firstly, the optimal superposition coefficient is obtained for the higher-order spatial differential terms generated by the non-Helmholtz-type coil using the least squares method. Next, the optimal superposition coefficient is obtained for the constant term and the first-order spatial differential term generated by the Helmholtz-type coil using the least squares method. Thus, the calculation is simplified, and the calculation accuracy is also improved. The obtained superposition coefficients become the direction and magnitude of the current flowing through each coil. By making the obtained current flow through the 3-axis magnetic field correction coil, the magnetic field of the three axes can be corrected (S26).

[0184] Figure 25 The corrections shown do not necessarily need to be performed frequently under normal conditions where the magnetic field does not change significantly. For example, in the case of repeatedly measuring clock transitions in clock transition space 52, it is sufficient to perform the corrections every specified number of times. Figure 25 The correction shown is sufficient. Alternatively, one could consider consistently verifying the size of the Zeeman split while measuring the clock transitions in clock transition space 52, and implementing the correction only if the size exceeds a specified value. Figure 25 The correction shown.

[0185] When the magnetic field of the clock transition space 52 is calibrated using a 3-axis magnetic field calibration coil within the calibration space 242, it is expected that the magnetic field of the clock transition space 52 can be stably zeroed out, compared to when the magnetic field of the clock transition space 52 is calibrated using a 3-axis magnetic field calibration coil within the clock transition space 52. This can be attributed to various minute disturbances, such as slight fluctuations in the magnetic field, errors in magnetic field measurement, and errors in the fundamental magnetic field of each coil, when only a narrow space like the clock transition space 52 is considered. In fact, experiments have shown that calibration using the calibration space 242 improves accuracy.

[0186] exist Figure 23A and Figure 25 In the example shown, a moving optical lattice is used to move the atomic cluster 240 to various positions in the correction space 242. In contrast, Figure 26 This is a diagram schematically illustrating an example of the magnetic field distribution within space 242 for one-time measurement calibration.

[0187] exist Figure 26 In this process, atomic cluster 250 is enclosed within an optical lattice throughout the entire region of the calibration space 242. Using a CCD camera 254, the fluorescence signals 252a, 252b, 252c, 252d, and 252e of atomic cluster 250 are received simultaneously while retaining their spatial position information, and their frequencies are determined. Thus, the magnetic field distribution of the calibration space 242 can be immediately determined.

[0188] (5) Independent magnetic field compensation coil

[0189] As explained in (1) above, for the Peltier element (refrigerator 58) which is a high-current device, an independent magnetic field compensation coil 102 for the refrigeration unit is used to compensate for the magnetic field of the clock transition space 52. Similarly, for the heater of the reactor 40, an independent magnetic field compensation coil 104 for the reactor is used to compensate for the magnetic field of the clock transition space 52. In cases where the large leakage magnetic field from the high-current device is entirely compensated by a 3-axis magnetic field correction coil, it is necessary to increase the order of the 3-axis magnetic field correction coil and increase the current. Therefore, using an independent magnetic field compensation coil to compensate for the magnetic field is effective. Here, the independent magnetic field compensation coil 102 for the refrigeration unit will be used as an example to illustrate this in detail.

[0190] Figure 27 This diagram schematically illustrates an example of the configuration of the cryogenic bath 54, the thermal connection member 56, the refrigerator 58, and the independent magnetic field compensation coil 102 for the refrigerator. The cryogenic bath 54 is a hollow component surrounding the clock transition space 52. Although not shown in the diagram, the wall of the cryogenic bath 54 has an opening along the X-axis for allowing light from the optical lattice to pass into the interior. The cryogenic bath 54 is made of oxygen-free copper or similar materials with high thermal conductivity.

[0191] A thermal connection component 56 is assembled in the cryogenic bath 54. The thermal connection component 56 serves as both a support structure for the cryogenic bath 54 and a path for heat to be carried away from the cryogenic bath 54. The thermal connection component 56 is also made of oxygen-free copper or similar materials with high thermal conductivity.

[0192] The refrigeration unit 58 includes: a Peltier element 58a, a heat sink 58b, a heat insulation component 58c, and permalloy magnetic field shielding components 58d and 58e. The Peltier element 58a is connected to a thermal connection component 56, and heat is carried away from the thermal connection component 56 by a flowing current. The heat sink 58b is a component made of oxygen-free copper or the like, which has high thermal conductivity. The heat sink 58b is disposed on the outer wall of the vacuum chamber 20, and releases the heat transferred from the Peltier element 58a to the outside of the vacuum chamber 20.

[0193] The heat insulation component 58c ensures thermal insulation between the permalloy magnetic field shield 58d and the thermal connection component 56. The heat insulation component 58c is made of a material with low thermal conductivity, such as silicon dioxide, and is spherically shaped to reduce the contact points between the permalloy magnetic field shield 58d and the thermal connection component 56. The permalloy magnetic field shield 58e is a magnetic field shield made of permalloy, which has high thermal conductivity and high magnetic permeability. The permalloy magnetic field shield 58e is positioned between the Peltier element 58a and the heat sink 58b, conducting heat from the Peltier element 58a to the heat sink 58b.

[0194] A temperature sensor 260, which uses thermocouples, thermistors, etc., is installed in the low-temperature bath 54 to input the measured temperature T1 to the control device 262. In addition, a temperature sensor 264 is installed in or around the heat sink 58b to input the measured temperature T2 to the control device 262.

[0195] Control device 262 controls the current to maintain the temperature T1 of the cryogenic bath 54 at a constant low temperature (e.g., 190K). Control is performed, for example, by using PID (Proportional Integral Differential) control, which also takes into account the temperature T2 on the heat sink 58b side. The determined current flows to the Peltier element 58a through current path 266.

[0196] The Peltier element 58a is a thermoelectric element that moves heat according to the current flowing through it. With the current flowing through it, the Peltier element 58a carries away heat from the thermal connection member 56 on the low-temperature side (and the low-temperature tank 54 connected to the thermal connection member 56) and releases heat to the permalloy magnetic field shield 58e on the high-temperature side (and the heat sink 58b connected to the permalloy magnetic field shield 58e).

[0197] A large current, for example several amperes, flows through the Peltier element 58a. This generates a large magnetic field. Most of the Peltier element 58a is covered by permalloy magnetic field shields 58d and 58e, which are made of highly permeable materials. Therefore, most of the generated magnetic field flows inside these components and does not leak to the outside. However, from the viewpoint of heat conduction efficiency, it is not possible to place a magnetic field shield between the thermally connected component 56 and the Peltier element 58a. Therefore, a leakage magnetic field 270 is generated. The leakage magnetic field 270 disrupts the magnetic field in the clock transition space 52 inside the cryogenic tank 54.

[0198] Therefore, in this embodiment, a separate magnetic field compensation coil 102 for the refrigeration unit is provided around the thermal connection member 56, which is an opening where magnetic field shielding is not possible. The separate magnetic field compensation coil 102 for the refrigeration unit generates a compensation magnetic field 272 when current flows through it.

[0199] In the independent magnetic field compensation coil 102 for the refrigeration unit, current flows through the current path 268, which branches off from the current path 266. That is, the Peltier element 58a and the independent magnetic field compensation coil 102 for the refrigeration unit are connected in parallel within the same current path. The resistance of the Peltier element 58a and the resistance of the independent magnetic field compensation coil 102 for the refrigeration unit will vary slightly depending on the temperature, but both can be considered approximately constant under the temperature conditions in which the measurement is performed. Therefore, the current flowing from the control device 262 to the current path 266 is distributed in a constant ratio to the Peltier element 58a and the independent magnetic field compensation coil 102 for the refrigeration unit.

[0200] When the current flowing through the Peltier element 58a increases, the current flowing through the independent magnetic field compensation coil 102 for the refrigeration unit also increases proportionally to the increase. Therefore, when the leakage magnetic field 270 from the Peltier element 58a increases, the compensation magnetic field 272 generated by the independent magnetic field compensation coil 102 for the refrigeration unit also increases by the same amount. The independent magnetic field compensation coil 102 for the refrigeration unit is configured to compensate for the leakage magnetic field 270 in the clock transition space 52 inside the cryogenic tank 54 (generating a magnetic field of the same magnitude in the opposite direction) when a certain magnitude of current flows in the current path 266. Therefore, magnetic field compensation can be performed even when the current changes. Furthermore, although current also flows in the current paths 266 and 268, the current flows back and forth close together in the current paths 266 and 268, so the generated magnetic field is small and does not pose a problem.

[0201] The configuration of current paths 266 and 268 can be described as a compensation current control unit that dynamically changes the current flowing through the independent magnetic field compensation coil 102 of the refrigeration unit according to the leakage magnetic field 270. The compensation current control unit can also be constructed in other ways, for example, by means of a control device 262 that makes the required current, calculated by calculation, flow through the independent magnetic field compensation coil 102 of the refrigeration unit.

[0202] exist Figure 27 In the example shown, the independent magnetic field compensation coil 102 for the refrigeration unit is formed by a coil wound around the thermal connection member 56. In this configuration, since the independent magnetic field compensation coil 102 for the refrigeration unit is located near the wall of the vacuum chamber 20, it is possible to prevent structural complexity near the cryogenic bath 54. However, the location of the independent magnetic field compensation coil 102 for the refrigeration unit is not particularly limited; for example, it can also be located near the cryogenic bath 54. By placing the independent magnetic field compensation coil 102 for the refrigeration unit near the cryogenic bath 54, miniaturization and power saving of the independent magnetic field compensation coil 102 for the refrigeration unit can be achieved.

[0203] The independent magnetic field compensation coil 102 for the refrigeration unit can also be formed by multiple coils instead of a single coil. In cases where the leakage magnetic field distribution in the clock transition space 52 is complex, it may be possible to compensate relatively easily by using multiple coils.

[0204] The magnetic field compensation module consists of a current device, an independent magnetic field compensation coil, and a compensation current control unit. Because the magnetic field compensation module can perform precise magnetic field compensation, it can be applied to various devices, such as the optical lattice clock 10.

[0205] (6) Zeeman reducer

[0206] Figure 28 This is a cross-sectional view of the Zeeman reducer coil 44 and the MOT device coil 48. In the illustrated Zeeman reducer coil 44, a coil 282 is wound around a long cylindrical bobbin 280, which is coaxially arranged with the beam axis. The hollow portion near the center of the bobbin is the space through which the atomic beam 42 flows along the beam axis.

[0207] From a functional point of view, the majority of coil 282 is a reduced-turn Zeeman coil section 284, with the number of turns gradually decreasing from the upstream side of the beam axis towards the downstream side. Furthermore, the downstreammost part of coil 282 in the beam axis direction is a high-turn MOT coil section 286. The covering wires of Zeeman coil section 284 and MOT coil section 286 are continuous. Additionally, the magnetic field generated by Zeeman coil section 284 extends to the vicinity of MOT coil section 286, and the magnetic field generated by MOT coil section 286 extends downstream of Zeeman coil section 284. Therefore, it should be noted that the boundary between Zeeman coil section 284 and MOT coil section 286 cannot be clearly defined.

[0208] A disk-shaped upstream flange 288 with a radius larger than the maximum radius of the Zeeman coil section 284 is provided upstream of the beam axis of the linear axis 280. The upstream flange 288 is fitted onto the cylindrical wall 32 at the protrusion 30 of the vacuum chamber 20. Additionally, a mirror support (not shown) is fitted to the front of the upstream flange 288. An optical mirror 76 is fitted to the front end of the mirror support.

[0209] Downstream of the beam axis of the linear shaft 280, two annular flanges 290 and 292, with the same radius as the MOT coil section 286, are provided. The downstream flange 290 is a thicker annular shape in the beam axis direction and is located near the boundary between the Zeeman coil section 284 and the MOT coil section 286. The downstream flange 292 is a thinner annular shape in the beam axis direction and is located downstream of the MOT coil section 286. The upper parts of the downstream flanges 290 and 292 are mounted to an upper support member 312, and the lower parts are mounted to a lower support member 314. The upper support member 312 and the lower support member 314 are respectively mounted to the rear circular wall 28 of the main body 22 of the vacuum chamber 20.

[0210] The MOT device coil 48 is positioned at a predetermined distance downstream of the Zeeman reducer coil 44. The MOT device coil 48 has an MOT coil 302 wound around a short cylindrical spool 300 coaxial with the beam axis. A thin annular flange 304 with the same radius as the MOT coil 302 is provided upstream of the beam axis of the spool 300. A thicker annular flange 306 with the same radius as the MOT coil 302 is provided downstream of the beam axis of the spool 300. The upper parts of the flanges 304 and 306 are fitted and fixed to the upper support member 312.

[0211] The spool 280, upstream flange 288, and downstream flanges 290 and 292 of the coil 44 in the Zeeman reducer are formed using copper or similar materials with high thermal conductivity and low magnetic permeability. Furthermore, the spool 280, upstream flange 288, and downstream flanges 290 and 292 are joined together with high strength and tightness through welding.

[0212] In the Zeeman reducer coil 44, more coils are wound on the upstream side of the beam axis, and the upstream side is heavier than the downstream side. Therefore, by engaging the upstream flange 288 with the cylindrical wall 32 of the protrusion 30 of the vacuum chamber 20, the Zeeman reducer coil 44 is stably positioned inside the vacuum chamber 20.

[0213] Furthermore, in the Zeeman reducer coil 44, heat is generated due to the current flowing through coil 282. Since the vacuum chamber 20 is a vacuum, unlike in the atmosphere, there is no heat conduction through the gas. Therefore, although a slight cooling effect from blackbody radiation occurs in the Zeeman reducer coil 44, the heat from coil 282 is primarily removed through heat conduction through the solid. The spool 280 is in contact with coil 282, effectively conducting heat from coil 282. Additionally, the large contact area between the upstream flange 288, downstream flanges 290, and 292 and coil 282 further carries away heat from coil 282. Figure 2As shown, the upstream flange 288 is connected to the Zeeman reducer cooler 92 at the cylindrical wall 32 of the protrusion 30. The Zeeman reducer cooler 92 cools the upstream flange 288 by circulating cooling water in water-cooled pipes made of copper or the like. This prevents the Zeeman reducer coil 44 from overheating.

[0214] The spool 300, flanges 304, and 306 of the coil 48 for the MOT device are also formed using copper or similar materials with high thermal conductivity and low magnetic permeability. Furthermore, the spool 300, flanges 304, and 306 are joined together with high strength and tightness through welding. Compared to the coil 282 of the coil 44 for the Zeeman reducer, the MOT coil 302 of the MOT device coil 48 is smaller and lighter, and the overall weight of the MOT device coil 48 is also lighter. Therefore, the MOT device coil 48 is stably mounted to the rear circular wall 28 via an upper support member 312 to which flanges 304 and 306 are fixed.

[0215] Furthermore, the current flowing through the MOT coil 302 of the MOT device coil 48 is smaller and the heat generated is also less compared to the coil 282 of the Zeeman reducer coil 44. Additionally, the MOT coil 302 in the MOT device coil 48 is surrounded by a bobbin 300, flanges 304 and 306 in three directions. Therefore, the heat generated in the MOT coil 302 is transferred to the MOT device cooler 94 via the upper support member 312. It is envisioned that the MOT device cooler 94 is water-cooled. However, if the amount of heat to be removed is small, air cooling can also be used.

[0216] exist Figure 28 In the example, the number of turns in coil 282 decreases almost monotonically, but more specifically, it has irregularities along the beam axis. One reason for this irregularity is to obtain the desired magnetic field strength at specific locations along the beam axis. For example, in the trapping space 50 for trapping atoms, it is necessary to have a zero magnetic field. Another reason, from an energy-saving perspective, is to configure the coil so that no magnetic field is generated in locations where it is not needed. In the Zeeman reducer coil 44, only the magnetic field required to slow down or confine the atoms needs to be generated. Furthermore, reasons for the irregularity include mechanical support requirements and thermal heat dissipation requirements. As the number of turns increases, the weight of the coil increases, making it difficult to support. Additionally, the heat dissipation from the coil increases. Therefore, it is advisable to increase the number of turns in areas where support is advantageous or where heat dissipation efficiency is high. Figure 28In the example shown, the coil 282 of the Zeeman reducer coil 44 is formed with a relatively convex shape with more turns at the contact point with the upstream flange 288, and with a relatively concave shape with fewer turns on its downstream side. Therefore, the center of gravity of the Zeeman reducer coil 44 shifts to the upstream flange 288 side, stabilizing the fixation provided by the upstream flange 288. Furthermore, since the contact area between the coil 282 and the upstream flange 288 also increases, heat conduction from the coil 282 to the upstream flange 288 can be efficiently achieved.

[0217] Here, refer to Figure 29 To explain the void in the coil. Figure 29 This is a cross-sectional view of the upper part of the two Zeeman coils 320 and 330. In Zeeman coil 320, including portion 322, the number of coil turns decreases monotonically in the beam axis direction. On the other hand, in Zeeman coil 330, the number of turns is locally small in portion 332, which is called the gap. However, in Zeeman coil 330, the number of turns is locally large before and after portion 332 in the beam axis direction. Therefore, the distribution of the magnetic field generated by the entire Zeeman coil 330 is substantially equal to the distribution of the magnetic field generated by Zeeman coil 320.

[0218] Theoretically, it is possible to determine how to form the gap and the shape of the coil around it. The magnetic field distribution produced by a unit current component follows the Biot-Savart law. Furthermore, the transformation from magnetic field distribution to current distribution can be treated as a deconvolution method or a generalized inverse problem. A method for finding the solution to the minimum current path through the inverse problem is documented, for example, in Mansfield P, Grannell PK., "NMR diffraction in solids." J Phys C: Solid State Phys 6: L422-L427, 1973. However, if we are not fixated on the minimum current, multiple solutions clearly exist. Figure 29 In this context, assuming that the solution for the minimum current path that satisfies the desired magnetic field distribution is the Zeeman coil 320, then the Zeeman coil 330, which increases the current density around the gap, can also form the desired magnetic field distribution.

[0219] exist Figure 28 In the coil 282 shown, a downstream flange 290 is provided in the middle of the coil 282. This is equivalent to the downstream flange 290 being located at a position with a large gap. Furthermore, by setting the number of turns before and after the beam direction of the downstream flange 290 to be more than the number of turns when the downstream flange 290 is not provided, the influence of the downstream flange 290 is eliminated or reduced.

[0220] Figure 30This is a diagram showing the magnetic field distribution in the Zeeman reducer coil 44 and the MOT device coil 48. The horizontal axis represents the position on the beam axis, with the origin corresponding to the trapping space 50. The vertical axis represents the magnitude of the magnetic field on the beam axis. Because the Zeeman reducer coil 44 and the MOT device coil 48 are formed symmetrically with respect to the beam axis, the magnetic field on the beam axis has only a component in the beam axis direction. The arrangement of coil 282 of the Zeeman reducer coil 44 and the arrangement of MOT coil 302 of the MOT device coil 48 are also shown on the beam axis. The points in the coordinate graph represent the calculated values ​​of the magnetic field, and the thin lines in the coordinate graph represent the values ​​of the ideal magnetic field in terms of slowing the atoms toward the trapping space 50 by Zeeman deceleration.

[0221] The magnetic field reaches its maximum slightly downstream of the upstream end of coil 282. Slightly upstream of this maximum value, the magnetic field decreases sharply, gradually approaching zero further upstream. An ideal magnetic field is one where the magnetic field is zero outside coil 282 and does not leak out to the outside. However, because the magnetic field generated by the current has spatial expansion, it is impossible to make the magnetic field outside coil 282 completely zero, for example, without providing a coil in the opposite direction to compensate for (cancel) the external magnetic field.

[0222] Downstream of the location where the magnetic field reaches its maximum value, the magnetic field monotonically decreases. The number of turns in the coil, as described above, has some irregularities, but the influence of the surrounding coils creates an ideal monotonically decreasing magnetic field for Zeeman deceleration. This magnetic field gradient is approximately consistent with the ideal magnetic field distribution for Zeeman deceleration, indicating that atoms can be steadily decelerated toward the trapping space 50.

[0223] The magnetic field decreases sharply from the downstream end of coil 282. Although the number of turns of the MOT coil section 286 located in this area is large, the value of the magnetic field decreases rapidly because there is no coil further downstream.

[0224] The magnetic field decreases with a roughly constant slope, becoming zero at the trapping space 50. Furthermore, the magnetic field decreases with the same slope, reaching a minimum (a negative value becomes a maximum) near the MOT coil 302 of the MOT device coil 48. This is because current flows through the MOT coil 302 in the opposite direction to that of coil 282. A Helmholtz-type coil is approximately formed from the vicinity of the MOT coil portion 286 of coil 282 to the vicinity of the MOT coil 302. Therefore, by flowing current in the opposite direction in the MOT coil 302, a magnetic field with a constant slope can be formed. Additionally, although not illustrated, a magnetic field with a constant slope is also formed in the direction perpendicular to the beam axis. The MOT beam is irradiated from each of the three axes into this gradient magnetic field formed by the MOT device. Thus, atoms can be trapped in the trapping space 50, which serves as the origin. Further downstream from the MOT coil 302, the magnetic field gradually approaches zero.

[0225] By combining the Zeeman reducer coil 44 with the MOT device coil 48, the beam axis length can be shortened compared to setting the Zeeman reducer and MOT device separately. Furthermore, the overall coil length can be shortened, thus achieving energy savings and reduced heat generation.

[0226] Furthermore, in the presence of a background magnetic field, the position where the magnetic field becomes zero will deviate from the trapping space 50. Therefore, during the process of trapping atoms, by adjusting the 3-axis magnetic field correction coil 96 or the bias coil of the correction gradient magnetic field, it is possible to generate a compensating magnetic field that cancels out the background magnetic field near the trapping space 50.

[0227] Next, refer to Figure 31A and Figure 32 B shows an example of an augmented Zeeman reducer with coil 340. Figure 31A This is a cross-sectional view showing the state before the Zeeman reducer is assembled with coil 340 inside the vacuum chamber 20. Figure 31B It is a cross-sectional view showing the assembled state. Figure 31A The upstream portion of the beam axis in the coil 342 of the shown Zeeman reducer coil 340 is a Zeeman coil section 344, which functions as a Zeeman coil. Additionally, the downstream portion of the coil 342 is a MOT coil section 346, which combines the functions of a Zeeman coil and a MOT coil. In the Zeeman coil section 344, the number of turns monotonically increases from the upstream end towards the downstream end. Furthermore, near the downstream end, after repeated fluctuations, the number of turns reaches its maximum at the downstream end. For convenience, the area with the maximum number of turns is referred to as the MOT coil section 346, but as described above, it also functions as a Zeeman coil.

[0228] The Zeeman reducer uses a coil 340 with a bobbin inside. Additionally, a flange 350 is provided at the upstream end, and a flange 352 is provided midway along the coil 342 near the downstream end, with a flange 354 at the downstream end. Flanges 350, 352, and 354 are welded to the bobbin.

[0229] The uppermost flange 350 is fitted with a mirror support (not shown), and an optical mirror 76 is fixed to the mirror support.

[0230] The flanges 352 and 354 on the downstream side are also connected to each other outside the spool, improving strength. Flange 352 is a thin, large-radius disc. Flange 352 is fitted to a ring-shaped support portion 370. The ring support portion 370 has a water-cooling pipe 372 through which cooling water flows, cooling the coil 342 via the flange 352. In the ring support portion 370, two beams 374 are fitted at the upper part, and two beams 376, which also serve as water-cooling pipes, are fitted at the lower part. Beams 374 and 376 are fitted into the rear circular wall 28 of the main body 22 of the vacuum chamber 20, supporting the entire structure including the Zeeman reducer coil 340. Furthermore, beams 374 and 376 form a heat dissipation path for transferring heat from the coil 342 to the rear circular wall 28. Additionally, the cooling water flowing through beams 376 can also circulate to the heat sink 58b in the chiller 58.

[0231] In this configuration, it is envisioned that the coil 380 for the MOT device is mounted on the rear circular wall 28 via a separately provided support member. Furthermore, it is envisioned that the coil 340 for the Zeeman reducer is positioned with the coil 380 for the MOT device via a positioning mechanism.

[0232] Figure 32 Is with Figure 30 The corresponding figure shows the magnetic distribution when using the augmented Zeeman reducer coil 340 and the MOT device coil 380. The magnetic field gradually increases from the downstream side of coil 342 of the Zeeman reducer coil 340, reaching its maximum value near the MOT coil section 346. This increase in magnetic field closely matches the target curve required to achieve Zeeman reduction. Downstream of the position where the maximum value is reached, the magnetic field decreases rapidly. Furthermore, it decreases from positive to negative with a roughly constant slope before and after the capture space 50, which serves as the origin, reaching zero in the capture space 50. The magnetic field becomes minimum near the MOT device coil 380 and then gradually approaches zero.

[0233] At the locations of the MOT devices before and after constituting the capture space 50, and... Figure 30Compared to the reduced type, the slope of the magnetic field becomes steeper. This is because the number of turns in the MOT coil section 346 of coil 342 is large, and the number of turns in the MOT device coils 380 facing each other is also large. By making the slope of the magnetic field steeper, atoms can be captured at a short distance in the beam axis direction.

[0234] in addition, Figure 32 The illustrated enhanced Zeeman reducer uses coil 340 and Figure 30 Compared to the reduced-type Zeeman reducer using coil 44, the length in the beam axis direction can be shortened. This is because, in the augmented type, atoms can be decelerated efficiently. In the augmented type, compared to the reduced type, the magnetic field required for atom deceleration can be suppressed, thus offering the advantage of energy saving.

[0235] On the other hand, in the enlarged Zeeman reducer coil 340, the capture space 50 side is relatively heavy, making it difficult to support it inside the vacuum chamber 20. Furthermore, in the enlarged type, the large number of coil turns on the capture space 50 side leads to increased heat generation near the center of the vacuum chamber 20, making cooling difficult. However, as described above, the Zeeman reducer coil 340 is supported near the center of the vacuum chamber 20 by a ring support 370 with a cooling function, thus avoiding these problems.

[0236] Figure 31A and Figure 31B The assembly method of coil 340 in the enhanced Zeeman reducer shown is just one example; other methods can also be used. (See reference...) Figure 33A and Figure 33B Let's illustrate with a variation example.

[0237] Figure 33A This is a perspective view showing the state before the Zeeman reducer is assembled with coil 390 inside the vacuum chamber 20. Figure 33B This is a perspective view showing the assembled state. The coil 392 of the Zeeman reducer coil 390 is wound in the same way as the Zeeman reducer coil 340, and its configuration, including the spool and multiple flanges 394, 396, and 398, is also largely the same. However, in the Zeeman reducer coil 390, the flange 396 located near the lower end in the beam direction is a semi-circular shape, roughly the lower half. Furthermore, the portion supporting the flange 396 is a roughly U-shaped semi-circular ring support 400 that divides the ring into two halves. A water-cooling pipe 402 is provided in the semi-circular ring support 400.

[0238] exist Figure 33A and Figure 33BIn the illustrated configuration, by making the flange 396 semi-circular, the cooling performance slightly decreases while maintaining the same level of cooling water circulation. On the other hand, in the Zeeman reducer coil 390, since there is space above the flange 396, it is easier to approach the furnace 40 side from the optical resonator 46 side inside the vacuum chamber 20. Furthermore, since a space is formed above the semi-circular ring support 400, disassembly of the optical resonator 46 becomes easier. Moreover, since the vertical distance of the water-cooling pipe is shortened, turbulence in the flow caused by convection within the water-cooling pipe is more easily prevented. Furthermore, in Figure 33A , 33B The flange 396 shown can be appropriately provided with holes in its surface. While providing holes reduces heat conduction efficiency, it achieves weight reduction. Similarly, in Figure 31A , 31B The flange 352 shown can also have holes in the surface.

[0239] Figure 34 This is a cross-sectional view of an augmented version of the Zeeman reducer coil 410. In the Zeeman reducer coil 410, a spool 412 with varying thickness in the beam direction is used. The cylindrical spool 412 has a constant inner diameter, but its outer diameter gradually decreases in a stepped manner from upstream to downstream in the beam direction. Furthermore, the coil 414 wound around the spool 412 is wound more extensively towards the downstream side in the beam axis direction. Therefore, the outer diameter of the coil 414 is approximately constant in the beam axis direction.

[0240] exist Figure 34 In the configuration shown, by increasing the outer diameter of the spool 412, the contact area between the spool 412 and the coil 414 becomes larger, thus improving the heat conduction efficiency from the coil 414 to the spool 412. Furthermore, since the steps of the spool 412 can be used to wind and cover the wire, the arrangement of the coil 414 becomes easier.

[0241] Furthermore, not limited to this embodiment, if the covering wire constituting the coil 414 is not a round wire with a circular cross-section, but a flat wire with a square cross-section, the heat conduction efficiency with the spool 412, etc., will be further improved. In addition, when the coil 414 is covered by a heat-conductive cover as shown below, since the outer diameter of the coil 414 is constant, it is easy to make the cover fit tightly with the coil 414 and remove heat through the cover.

[0242] The above describes an example of placing a Zeeman reducer inside the vacuum chamber 20. By providing a cooling mechanism to remove Joule heat generated in the coil, the Zeeman reducer can be placed in the vacuum chamber 20 in a thermally stable manner. Below, as another example, an example of sealing part or all of the coil with a cover (i.e., encapsulation) will be described.

[0243] Figure 35A and Figure 35B This is a side cross-sectional view showing the coil 420 and cover 440 for the Zeeman reducer. Figure 35A This diagram shows the state before the cover 440 is assembled onto the coil 420 of the Zeeman reducer. Figure 35B This diagram shows the assembled state. The Zeeman reducer coil 420 is a reduced-turn type where the number of turns gradually decreases in the direction of the beam axis.

[0244] In the Zeeman reducer, the spool 422 of the coil 420 has a flange 424 at the upstream end of the beam axis and a flange 426 at the midpoint of the downstream side. The spool 422 and flanges 424 and 426 are made of copper or the like in the previous example, ensuring high thermal conductivity. Sealing members 428 and 430 made of indium are provided on the outer periphery of flanges 424 and 426. Sealing members 428 and 430 are formed as thin, annular (also called ring-shaped) sheets or as thick-walled, annular shapes. Indium has the characteristic of providing stable vacuum sealing even under large temperature variations. Furthermore, a hermetic connector 432, serving as a vacuum-resistant connector, is provided on flange 426.

[0245] On the spool 422, a coil 434 is wound between flanges 424 and 426, and a coil 436 is wound downstream of flange 426. Both coils 434 and 436 are formed of copper-insulated wire coated with resin. Coils 434 and 436 are electrically connected via a hermetically sealed connector 432.

[0246] The cover 440 is formed in a cylindrical shape. The cover 440 is formed using the same copper as the bobbin 422, flanges 424, 426 and coils 434, 436, which suppresses deformation caused by thermal expansion.

[0247] The cover 440 is configured to cover the flanges 424 to 426. Specifically, a portion of the inner periphery of the upstream end of the cover 440 surrounds a portion of the outer periphery of the flange 424 and is sealed by the sealing member 428. Additionally, a portion of the inner periphery of the downstream end of the cover 440 surrounds a portion of the outer periphery of the flange 426 and is sealed by the sealing member 430. The cover 440 is manufactured with a positive tolerance relative to the length from the flanges 424 to 426, enabling it to reliably cover both flanges.

[0248] The air pressure inside the cover 440 can be freely set, as long as the sealing members 428 and 430 can reliably seal the surface. For example, atmospheric pressure air can be sealed in, or a rough vacuum can be set. A rough vacuum refers to a state of rarefaction achieved using a turbine pump or similar means, for example, set to 1 Pa to 0.1 Pa. When the inside of the cover 440 is set to a rough vacuum, the pressure difference between the inside and outside of the cover 440 decreases when the vacuum chamber 20 is set to a vacuum, thus effectively preventing the sealing surfaces formed by the sealing members 428 and 430 from separating.

[0249] Inert gases such as nitrogen or helium can also be sealed inside the cover 440. The inert gas is chosen to have low reactivity with the resin used in the coil when the coil 434 is heated to a high temperature. The pressure of the inert gas is not particularly limited; for example, it can be 1 atmosphere or a rough vacuum. Alternatively, a lightweight resin such as foamed urethane can be filled inside the cover 440. In this case, the strength of the cover 440 can be improved.

[0250] The Zeeman reducer coil 420 heats up due to Joule heating when energized. Compared to the coil 436 with fewer turns, the coil 434 with more turns generates more Joule heat. Therefore, the coil 434 tends to heat up. As it heats up, trace amounts of gas contained in the resin covering the conductors constituting the coil 434 are released from the resin (this gas is called degassing). However, in the Zeeman reducer coil 420, the coil 434 is sealed by the bobbin 422, flanges 424 and 426, and the cover 440, preventing degassing from leaking into the vacuum chamber 20. Therefore, clock transition errors caused by degassing are prevented. Thus, the Zeeman reducer coil 420, sealed by the cover 440, functions as a convenient vacuum setting coil for installation in a vacuum environment.

[0251] The cover 440 also serves as the heat transfer medium between flanges 424 and 426. That is, heat is transferred between flanges 424 and 426 not only through the spool 422 but also through the cover 440, thus also promoting the cooling of coils 434 and 436.

[0252] In the above description, it is envisioned that the cover 440 covers the outer periphery of the flanges 424 and 426 and does not contact the coil 434. However, it is also possible for the cover 440 to contact part or all of the outer surface of the coil 434. In this case, heat from the coil 434 will be directly conducted to the cover 440, thus improving heat dissipation efficiency. In particular, as Figure 34As shown with coil 414, when the outer diameter of coil 414 is constant, it is easy to seal tightly with the inner circumference of cover 440. In addition, if it is difficult to form a shape that allows cover 440 to contact the outer surface of coil 434, a thermally conductive component can be inserted between cover 440 and coil 434.

[0253] exist Figure 35A and Figure 35B In the illustrated embodiment, the cover 440 does not cover the coil 436. This is because the coil 436 has few turns, reducing the need for measures to address degassing. Furthermore, the coil 436 includes the MOT coil portion constituting the MOT device, and the optical resonator 46 and the like are located nearby; therefore, covering the coil 436 with a cover avoids the need for a large aperture. However, as long as interference with surrounding devices and components can be avoided, the entire assembly, including the coil 436, can be encapsulated with a cover.

[0254] In addition, Figure 35A and Figure 35B The example given is a reduced-type Zeeman reducer using coil 420. However, in the case of an increased-type reducer, it is also possible to encapsulate part or all of the portion containing a large number of turns.

[0255] Furthermore, in the above description, the cover 440 uses indium sealing members 428 and 430 to seal against flanges 424 and 426, thus airtightening the interior. However, sealing members made of materials other than indium can also be used. When using sealing members, for example, the cover 440 can be installed to or removed from flanges 424 and 426 using fixing screws. However, for example, semi-permanent sealing methods such as welding or vacuum brazing can also be used to seal the cover 440 against flanges 424 and 426, thus airtightening the interior.

[0256] In the above description, an optical lattice clock was used as an example. However, those skilled in the art can also apply the techniques of this embodiment to other than optical lattice clocks. Specifically, it can also be applied to atomic clocks other than optical lattice clocks, or to atomic interferometers that use atomic interferometers. Moreover, this embodiment can also be applied to various quantum information processing devices targeting atoms (including ionized atoms). Here, quantum information processing devices refer to devices that use the quantum states of atoms or light to perform measurement, sensing, and information processing. In addition to atomic clocks and atomic interferometers, examples include magnetometers, electric field meters, quantum computers, quantum simulators, and quantum repeaters. In the physical packaging of quantum information processing devices, miniaturization or portability can be achieved in the same way as in the physical packaging of optical lattice clocks, by using the techniques of this embodiment. Furthermore, it should be noted that in such devices, the clock transition space is sometimes not used as a space for clock measurement, but merely as a space that causes the splitting of light due to clock transitions.

[0257] In these devices, for example, by incorporating the 3-axis magnetic field correction coil of this embodiment, it is possible to improve the accuracy of the device. Furthermore, by arranging the three axes of this embodiment within a vacuum chamber, it is possible to achieve miniaturization, portability, or high precision in the physical package. Moreover, by introducing a magnetic field compensation module, the magnetic field distribution can be controlled with high precision. Additionally, in physical packages using a vacuum chamber, incorporating a vacuum setting coil is effective.

[0258] In the above description, specific solutions have been shown for ease of understanding. However, these are merely illustrative embodiments, and various other embodiments can also be adopted.

[0259] The following are notes on this embodiment.

[0260] (Postscript 1)

[0261] A magnetic field compensation module, characterized in that it comprises:

[0262] A current-carrying device is placed inside a vacuum chamber surrounding a clock transition space containing atoms, wherein a current used by the device is circulated to generate a leakage magnetic field.

[0263] A compensation coil, disposed near the current-carrying device, wherein the current used by the coil flows; and

[0264] A control unit dynamically changes the current flowing through the compensation coil to compensate for the leakage magnetic field relative to the clock transition space.

[0265] (Postscript 2)

[0266] According to the magnetic field compensation module described in Appendix 1, it is characterized in that,

[0267] The current device is a Peltier element that cools a cryogenic bath that maintains the clock transition space at a specified low temperature.

[0268] The control unit changes the current used in the coil based on the temperature of the cryogenic bath or the current used by the device flowing through the Peltier element.

[0269] (Note 3)

[0270] According to the magnetic field compensation module described in Appendix 1, it is characterized in that,

[0271] A magnetic field shield made of a high-permeability material is provided around the current device.

[0272] The compensation coil compensates for the leakage magnetic field that leaks out from the magnetic field shield.

[0273] (Note 4)

[0274] According to the magnetic field compensation module described in Appendix 1, it is characterized in that,

[0275] The control unit includes a distribution wire that distributes current to the coil from the current used by the device, and distributes the current to the coil according to the current used by the device.

[0276] (Note 5)

[0277] A physical packaging system for an optical lattice clock, characterized in that,

[0278] It has the magnetic field compensation module described in Appendix 1.

[0279] (Note 6)

[0280] A physical packaging system for atomic clocks, characterized in that,

[0281] It has the magnetic field compensation module described in Appendix 1.

[0282] (Note 7)

[0283] A physical packaging system for an atomic interferometer, characterized in that,

[0284] It has the magnetic field compensation module described in Appendix 1.

[0285] (Postscript 8)

[0286] A physical packaging system for quantum information processing devices targeting atoms or ionized atoms, characterized in that,

[0287] It has the magnetic field compensation module described in Appendix 1.

[0288] (Note 9)

[0289] A physical packaging system, characterized in that it comprises:

[0290] The magnetic field compensation module described in Appendix 1; and

[0291] At least one of the following atomic laser cooling devices, namely a Zeeman speed reducer, a magneto-optical trap, and an optical lattice trap, is used to guide the atoms into the clock transition space.

[0292] (Postscript 10)

[0293] A physical package, characterized in that,

[0294] have:

[0295] Vacuum chamber; and

[0296] A Zeeman reducer comprises: a spool formed in a cylindrical shape, through which an atomic beam flows along a beam axis; and a series of coils wound around the spool, wherein the Zeeman reducer forms a spatially gradient magnetic field within the cylinder.

[0297] A flange is provided on the spool, which enlarges the diameter of the outer surface of the tube at a midpoint in the beam axis direction.

[0298] The series of coils are wound around the spool across the flange.

[0299] The Zeeman reducer is configured to have the flange directly or indirectly mounted in the vacuum chamber, and is located within the vacuum chamber.

[0300] (Postscript 11)

[0301] According to the physical packaging described in Appendix 10, it is characterized in that,

[0302] The series of coils is an increased type with more turns on the downstream side compared to the upstream side of the atomic beam.

[0303] The flange is located on the downstream side of the spool.

[0304] (Postscript 12)

[0305] According to the physical packaging described in Appendix 11, it is characterized in that,

[0306] The vacuum chamber is formed in a generally cylindrical shape with its central axis parallel to the beam axis.

[0307] The flange is indirectly fitted to the cylindrical wall downstream of the atomic beam in the vacuum chamber using a support member.

[0308] (Postscript 13)

[0309] The physical packaging according to Appendix 12 is characterized in that,

[0310] The flange is formed in a generally circular shape.

[0311] The support member has a generally annular support portion that supports the outer edge of the flange.

[0312] A cooling mechanism is provided in the generally annular support portion, in which liquid refrigerant flows through a pipe to cool the flange.

[0313] (Postscript 14)

[0314] The physical packaging according to Appendix 12 is characterized in that,

[0315] The flange is formed into a roughly fan shape with its diameter widened in the direction including the vertical downward direction.

[0316] The support member has a generally U-shaped support portion that supports the outer edge of the flange.

[0317] A cooling mechanism is provided in the generally U-shaped support section, in which liquid refrigerant flows through a pipe to cool the flange.

[0318] (Postscript 15)

[0319] According to the physical packaging described in Appendix 10, it is characterized in that,

[0320] The spool and the flange are made of metal.

[0321] The physical package is provided with a cooling mechanism that directly or indirectly cools the flange.

[0322] (Postscript 16)

[0323] According to the physical packaging described in Appendix 10, it is characterized in that,

[0324] Furthermore, a counter-coil is provided at a position separating from the Zeeman reducer towards the downstream side of the atomic beam, wound around the beam shaft.

[0325] The series of coils and the counterpart coil form an MOT magnetic field between the series of coils and the counterpart coil.

[0326] (Postscript 17)

[0327] A physical package for an optical lattice clock, characterized in that,

[0328] It has the physical packaging described in Appendix 10.

[0329] (Postscript 18)

[0330] A physical encapsulation of an atomic clock, characterized in that,

[0331] It has the physical packaging described in Appendix 10.

[0332] (Postscript 19)

[0333] A physical package for an atomic interferometer, characterized in that,

[0334] It has the physical packaging described in Appendix 10.

[0335] (Postscript 20)

[0336] A physical package for a quantum information processing device targeting atoms or ionized atoms, characterized in that,

[0337] It has the physical packaging described in Appendix 10.

[0338] (Postscript 21)

[0339] A vacuum setting coil, characterized in that it comprises:

[0340] A coil, positioned within a vacuum chamber, is wound around the beam axis through which the atomic beam flows, creating a spatially gradient magnetic field; and

[0341] A hermetically sealed component that hermetically surrounds part or all of the coil.

[0342] (Postscript 22)

[0343] The vacuum setting coil according to Appendix 21 is characterized in that,

[0344] The sealing component is made of metal.

[0345] (Postscript 23)

[0346] The vacuum setting coil according to Appendix 21 is characterized in that,

[0347] The sealing component includes:

[0348] A cylindrical spool is disposed on the inner circumference of the coil, and the coil is wound on it;

[0349] Two flanges, formed by enlarging the diameter of the outer surface of the bobbin, surround the side of the coil in the direction of the beam axis; and

[0350] A cover that surrounds the outer periphery of the coil between the two flanges.

[0351] (Postscript 24)

[0352] The vacuum setting coil according to Appendix 23 is characterized in that,

[0353] The cover surrounds at least a portion of the outer periphery of the two flanges.

[0354] (Postscript 25)

[0355] The vacuum setting coil according to Appendix 23 is characterized in that,

[0356] The cover is in direct contact with a portion or all of the outer periphery of the coil, or indirect contact via a thermally conductive member inserted into the space surrounded by the sealing member.

[0357] (Postscript 26)

[0358] The vacuum setting coil according to Appendix 21 is characterized in that,

[0359] The coils have different numbers of turns in the direction of the beam axis.

[0360] The area surrounded by the sealing member includes the portion of the coil with the largest number of turns.

[0361] (Postscript 27)

[0362] The vacuum setting coil according to Appendix 21 is characterized in that,

[0363] The space surrounded by the sealed component is kept as rarefied as the atmosphere.

[0364] (Postscript 28)

[0365] The vacuum setting coil according to Appendix 21 is characterized in that,

[0366] An inert gas is sealed in the space surrounded by the sealed component.

[0367] (Postscript 29)

[0368] The vacuum setting coil according to Appendix 21 is characterized in that,

[0369] The space surrounded by the sealed component is filled with foamed resin.

[0370] (Postscript 30)

[0371] The vacuum setting coil according to Appendix 21 is characterized in that,

[0372] The sealing component has a vacuum-resistant connector.

[0373] The portion of the coil that is airtightly surrounded by the sealing member and the portion that is not surrounded are electrically connected through the vacuum-resistant connector.

[0374] (Postscript 31)

[0375] A physical package, characterized by comprising:

[0376] The vacuum setting coil described in Appendix 21; and

[0377] The vacuum chamber.

[0378] (Postscript 32)

[0379] According to the physical packaging described in Appendix 31, it is characterized in that,

[0380] The coil is a reduced-turn coil with a relatively small number of turns on the downstream side of the atomic beam.

[0381] The physical package has a counter coil wound around the beam axis at a position separating it from the reduced coil towards the downstream side of the atomic beam.

[0382] The reduced-type coil and the opposing coil form a gradient magnetic field for the MOT device between the reduced-type coil and the opposing coil.

[0383] The sealing member hermetically surrounds the upstream portion of the coil containing the beam axis, but does not surround the downstream portion.

[0384] (Postscript 33)

[0385] According to the physical packaging described in Appendix 31, it is characterized in that,

[0386] The coil is an increased-turn coil with a relatively large number of turns on the downstream side of the atomic beam.

[0387] The physical package has a counter coil wound around the beam axis at a position separating it from the augmented coil towards the downstream side of the atomic beam.

[0388] The augmented coil and the counter coil form a gradient magnetic field for the MOT device between the augmented coil and the counter coil.

[0389] The sealing member airtightly surrounds the portion of the coil containing the downstream side of the beam axis.

[0390] (Postscript 34)

[0391] A physical package for an optical lattice clock, characterized in that,

[0392] It has the physical package described in Appendix 31.

[0393] (Postscript 35)

[0394] A physical encapsulation of an atomic clock, characterized in that,

[0395] It has the physical package described in Appendix 31.

[0396] (Postscript 36)

[0397] A physical package for an atomic interferometer, characterized in that,

[0398] It has the physical package described in Appendix 31.

[0399] (Postscript 37)

[0400] A physical package for a quantum information processing device targeting atoms or ionized atoms, characterized in that,

[0401] It has the physical package described in Appendix 31.

[0402] (Postscript 38)

[0403] A hermetically sealed component is used to seal a coil disposed within a vacuum chamber and wound around a beam axis through which an atomic beam flows to form a spatially gradient magnetic field.

[0404] The sealing component is characterized in that...

[0405] The sealing member is sealed between the coil side and the coil side using indium formed in a ring-shaped sheet or thick-walled shape, thereby hermetically surrounding part or all of the coil.

[0406] Explanation of reference numerals in the attached figures

[0407] 10 Optical lattice clock, 12 Physical package, 14 Optical system device, 16 Control device, 18 PC, 20 Vacuum chamber, 22 Main body, 24 Cylindrical wall, 26 Front circular wall, 28 Rear circular wall, 30 Protrusion, 32 Cylindrical wall, 34 Front circular wall, 38 Leg, 40 Atomic furnace, 42 Atomic beam, 44 Coil for Zeeman reducer, 44a Flange, 46 Optical resonator, 48 Coil for MOT device, 48a Flange, 50 Capture space, 52 Clock transition space 54 Cryogenic bath, 56 Thermal connection component, 58 Cryostat, 58a Peltier element, 58b Heat sink, 58c Thermal insulation component, 58d, 58e Permalloy magnetic field shield, 60 Vacuum pump body, 62 Vacuum pump cylinder, 64, 66 Vacuum-resistant optical window for optical lattice, 68 Vacuum-resistant optical window for MOT, 70, 72 Vacuum-resistant optical window for MOT, 74, 76 Optical mirror, 80 Optical lattice beam, 82 Zeeman decelerating beam, 84, 86a, 86b MOT beam, 90 cooler for nuclear reactor, 92 cooler for Zeeman reducer, 94 cooler for MOT device, 963 axial magnetic field correction coil, 98 vacuum-resistant electrical connector, 102 independent magnetic field compensation coil for refrigeration unit, 104 independent magnetic field compensation coil for nuclear reactor, 120 first coil group, coils 122 and 124, 130 second coil group, coils 132 and 134, arrows 136 and 138, 140 first coil group, 142 composite coil, coils 143 and 144. 145 Composite coil, 146, 147 coils, 150 Second coil group, 152, 154 coils, 160 First coil group, 162 Composite coil, 163, 164 coils, 165 Composite coil, 166, 167 coils, 170 Second coil group, 172, 174 coils, 180 Retaining member, 182, 184, 186 Frame, 190 Correction coil, 192 Current path, 194 Insulation part, 196 Wiring path, 198 Terminal connector, 199 Edge Boundary section, current paths 200, 202, 203, 204, 206, 208, 210 correction coil, current paths 212, 214, 218 physical package, 220 vacuum chamber, 222 main body, 224, 2303 axis magnetic field correction coils, 240 atomic cluster, 242 correction space, 243 fluorescence observation space, 244 fluorescence, 246 photodetector, 250 atomic cluster, 252a, 252b, 252c, 252d, 252e fluorescence, 25 4CCD camera, 260 temperature sensor, 262 control device, 264 temperature sensor, 266 current path, 268 current path, 270 leakage magnetic field, 272 compensation magnetic field, 280 spool, 282 coil, 284 Zeeman coil section, 286 MOT coil section, 288 upstream flange, 290, 292 downstream flanges, 300 spool, 302 MOT coil, 304, 306 flanges, 312 upper support member, 314 lower support member, 320 Zeeman coil.Part 322, Zeeman coil 330, Part 332, Zeeman reducer coil 340, Coil 342, Zeeman coil section 344, MOT coil section 346, Flanges 350, 352, 354, Annular support section 370, Water cooling pipe 372, Beams 374, 376, Coil for MOT device 380, Zeeman reducer coil 390, Coil 392, Flanges 394, 396, 398, Semi-annular support section 400, Water cooling pipe 402, Zeeman reducer coil 410, Bollard 412, Coil 414, Coil 420, Zeeman reducer coil 422, Bollard 424, 426, Flanges 428, 430, Sealing component 432, Airtight connector 434, 436, Coil 440, Cover.

Claims

1. A three-axis magnetic field correction coil, characterized in that, Include: The first coil group of the Helmholtz type is formed in a point-symmetric shape with respect to the clock transition space as the center in each of the following directions: the first axis direction passing through the clock transition space in which atoms are arranged, the second axis direction perpendicular to the first axis direction, and the third axis direction perpendicular to the first axis direction and the second axis direction. as well as The second coil group, which is not Helmholtz type, is formed in a point-symmetric shape centered on the clock transition space in each of the first, second, and third axis directions. Its coil size, shape, or inter-coil spacing differs from that of the first coil group. The first coil group includes a first-axis first coil group formed along the first axis direction, a second-axis first coil group formed along the second axis direction, and a third-axis first coil group formed along the third axis direction. The second coil group includes a first-axis second coil group formed along the first axis direction, a second-axis second coil group formed along the second axis direction, and a third-axis second coil group formed along the third axis direction. The constant term of the magnetic field component in the corresponding axial direction can be adjusted using the first coil group. The first coil group along the first axis allows adjustment of the spatial first-order differential term of the magnetic field component along the first axis. The spatial first-order differential term of the magnetic field component in the direction of the second axis can be adjusted via the first coil group of the second axis. The spatial first-order differential term of the magnetic field component along the third axis can be adjusted via the first coil group along the third axis. The spatial second-order differential term of the magnetic field component along the first axis can be adjusted using the first-axis second coil group. The second coil group along the second axis allows adjustment of the spatial second-order differential term of the magnetic field component along the first axis in the direction of the second axis. The second coil group of the third axis can be used to adjust the spatial second-order differential term of the magnetic field component in the direction of the first axis in the direction of the third axis.

2. The 3-axis magnetic field correction coil according to claim 1, characterized in that, It can conduct currents of different magnitudes and directions through each coil constituting the first coil group.

3. The 3-axis magnetic field correction coil according to claim 1, characterized in that, The coils constituting the second coil group are electrically connected, and the same magnitude of current flows in the same direction around the first shaft.

4. The 3-axis magnetic field correction coil according to claim 3, characterized in that, The 3-axis magnetic field correction coil includes a non-Helmholtz type third coil group, which is formed in a point-symmetric shape centered on the clock transition space along the direction of the first axis. The coil size, shape, and spacing between the coils differ from those of the first and second coil groups. The coils that make up the third coil group are electrically connected, and the same magnitude of current flows in opposite directions around the first shaft.

5. The 3-axis magnetic field correction coil according to claim 1, characterized in that, In each of the directions of the second axis, which passes through the clock transition space and is perpendicular to the first axis, and the third axis, which is perpendicular to both the first and second axes, the 3-axis magnetic field correction coil comprises: The fourth coil group of the Helmholtz type is formed in a point-symmetrical shape centered on the clock transition space; and The fifth coil group, which is not Helmholtz type, is formed in a point-symmetric shape centered on the clock transition space, and its coil size, coil shape, or inter-coil distance is different from that of the fourth coil group.

6. The 3-axis magnetic field correction coil according to claim 5, characterized in that, In the fourth coil group, two composite coils, each composed of multiple small coils, are formed in a point-symmetrical shape centered on the clock transition space. In the two composite coils of the fourth coil group, the plurality of small coils are arranged with their centers offset in the direction of the first axis. The two composite coils of the fourth coil group are formed in the following shape: when the current flowing through the plurality of small coils is adjusted, they become equivalent to the Helmholtz type.

7. The 3-axis magnetic field correction coil according to claim 5, characterized in that, The coils constituting the fifth coil group are electrically connected, and the same magnitude of current flows in the same direction around the axis around which the fifth coil group is arranged.

8. The 3-axis magnetic field correction coil according to claim 5, characterized in that, The 3-axis magnetic field correction coil is formed in the following shape: for the magnetic field components in the directions of the first axis, the second axis and the third axis, it can correct the constant term, the first spatial differential term and the second spatial differential term in the direction of the first axis.

9. A physical packaging system, characterized in that, have: The 3-axis magnetic field correction coil as described in claim 1; and A control device that controls the current flowing through the correction coil of the three-axis magnetic field.

10. The physical packaging system according to claim 9, characterized in that, The physical package includes a vacuum chamber, device, or support structure comprising portions that are point-symmetrical about the clock transition space. At least a portion of the 3-axis magnetic field correction coil is formed on a flexible printed circuit board and assembled at the point-symmetric location.

11. A physical package for an optical lattice clock, characterized in that, It has the 3-axis magnetic field correction coil as described in claim 1.

12. A physical encapsulation for an atomic clock, characterized in that, It has the 3-axis magnetic field correction coil as described in claim 1.

13. A physical package for an atomic interferometer, characterized in that, It has the 3-axis magnetic field correction coil as described in claim 1.

14. A physical package for a quantum information processing device targeting atoms or ionized atoms, characterized in that, It has the 3-axis magnetic field correction coil as described in claim 1.

15. A physical package, characterized in that, have: The 3-axis magnetic field correction coil as described in claim 1; and At least one of the following atomic laser cooling devices, namely a Zeeman speed reducer, a magneto-optical trap, and an optical lattice trap, is used to guide the atoms into the clock transition space.

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