JP7555064B2 - Coil for vacuum installation, physics package, physics package for optical lattice clock, physics package for atomic clock, physics package for atomic interferometer, physics package for quantum information processing device, and sealing member - Google Patents

Description

The present invention relates to a vacuum installation coil, a physics package, a physics package for an optical lattice clock, a physics package for an atomic clock, a physics package for an atomic interferometer, a physics package for a quantum information processing device, and a sealing member.

The optical lattice clock is an atomic clock proposed in 2001 by Katori Hidetoshi, one of the inventors of this application. Optical lattice clocks confine an atomic group in an optical lattice formed by laser light to measure the resonant frequency in the visible light range, making it possible to measure with an accuracy of 18 orders of magnitude, far surpassing the accuracy of current cesium clocks. Optical lattice clocks have been actively researched and developed by the inventors' group, as well as by various other groups both in Japan and overseas, and are being developed into the next-generation atomic clock.

Recent optical lattice clock technology can be found, for example, in the following Patent Documents 1 to 3. Patent Document 1 describes the formation of a one-dimensional moving optical lattice inside an optical waveguide having a hollow passage. Patent Document 2 describes a method for setting an effective magic frequency. Furthermore, Patent Document 3 describes a radiation shield that reduces the effects of blackbody radiation emitted from surrounding walls.

Optical lattice clocks measure time with such high precision that a difference in altitude of 1 cm on Earth, which is due to the general relativistic effect of gravity, can be detected as a deviation in the passage of time. Therefore, if optical lattice clocks could be made portable and used in the field outside of laboratories, it would open up new possibilities for application to geodetic technologies, such as exploring for underground resources, detecting underground cavities, and detecting magma pools. By mass-producing optical lattice clocks and deploying them in various locations to continuously monitor the time fluctuations of gravitational potential, it would also be possible to detect crustal movements and map the spatial gravity field. In this way, optical lattice clocks are expected to contribute to society as a new fundamental technology that goes beyond the scope of high-precision time measurement.

The following non-patent documents 1 to 5 describe attempts to make optical lattice clocks portable. For example, non-patent document 4 describes a physics package of an optical lattice clock housed in a frame that is 99 cm long, 60 cm wide, and 45 cm high. In this physics package, an atomic oven, a Zeeman decelerator, and a vacuum chamber are arranged in that order in the length direction. On the outside of the vacuum chamber, a pair of square magnetic field correction coils with sides of about 30 to 40 cm are installed in the three directions of length, width, and height. The magnetic field correction coils are used to compensate the magnetic field distribution in the area around the atoms during spectroscopy to be uniform and to a zero value, in order to perform clock transition spectroscopy on the atoms under a zero magnetic field.

Patent No. 6206973 Special table 2018-510494 publication JP 2019-129166 A

Stefan Vogt et al. “A transportable optical lattice clock” Journal of Physics: Conference Series 723 012020, 2016 S. B. Koller et al. “Transportable Optical Lattice Clock with 7 × 10-17 Uncertainty” Physical review letters 118 073601, 2017 William Bowden et al. “A pyramid MOT with integrated optical cavities as a cold atom platform for an optical lattice clock” Scientific Reports 9 11704, 2019 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 N. Poli et al. “Prospect for a compact strontium optical lattice clock” Proceedings of SPIE 6673, 2007

By making the optical lattice clock even more compact and portable than the optical lattice clocks described in the above-mentioned non-patent documents 1 to 5, it will become easier to transport and install the optical lattice clock, and its usability will also be improved.

To make the physics package of the optical lattice clock more compact and portable, we are considering installing a Zeeman reducer inside a vacuum chamber. In a Zeeman reducer, a relatively large current flows through the coil, which can cause Joule heat to heat the coil and lead to the release of outgassing from the resin in the coated conductor that makes up the coil. Outgassing can cause a decrease in the accuracy of the optical lattice clock. The release of outgassing can also be a problem in physics packages other than optical lattice clocks.

The objective of the present invention is to realize a new coil that can be installed inside a vacuum chamber.

The vacuum installation coil of the present invention is installed in a vacuum chamber and includes a coil wound around the beam axis through which an atomic beam flows to form a spatially gradient magnetic field, and a sealing member that hermetically surrounds part or all of the coil.

In one aspect of the present invention, the sealing member is made of metal.

In one aspect of the present invention, the sealing member includes a cylindrical bobbin provided on the inner periphery of the coil and around which the coil is wound, two flanges that enlarge the outer diameter of the bobbin tube and surround the side of the coil in the direction of the beam axis, and a cover that surrounds the outer periphery of the coil between the two flanges.

In one aspect of the present invention, the cover surrounds at least a portion of the outer periphery of the two flanges.

In one aspect of the present invention, the cover is in direct contact with part or all of the outer periphery of the coil, or indirect contact with the coil via a thermally conductive member inserted into the space surrounded by the sealing member.

In one aspect of the present invention, the coil has a different number of turns in the direction of the beam axis, and the area surrounded by the sealing member includes the part of the coil with the maximum number of turns.

In one aspect of the present invention, the space enclosed by the sealing member is kept at a low concentration compared to the atmosphere.

In one aspect of the present invention, an inert gas is sealed in the space enclosed by the sealing member.

In one aspect of the present invention, the space surrounded by the sealing member is filled with a foamable resin.

In one aspect of the present invention, the sealing member is equipped with a vacuum-resistant connector, and the portion of the coil that is hermetically surrounded by the sealing member and the portion that is not surrounded by the sealing member are electrically connected through the vacuum-resistant connector.

The physics package of the present invention comprises the vacuum installation coil and the vacuum chamber.

In one aspect of the present invention, the coil is a decreasing coil with a relatively small number of turns downstream of the atomic beam, and the physics package includes a counterpart coil wound around the beam axis at a position spaced from the decreasing coil downstream of the atomic beam, the decreasing coil and the counterpart coil form a gradient magnetic field for an MOT device between the decreasing coil and the counterpart coil, and the sealing member hermetically surrounds a portion of the coil including the most upstream side of the beam axis and does not surround a portion including the most downstream side.

In one aspect of the present invention, the coil is an increasing coil with a relatively large number of turns downstream of the atomic beam, and the physics package includes a counterpart coil wound around the beam axis at a position spaced from the increasing coil downstream of the atomic beam, the increasing coil and the counterpart coil form a gradient magnetic field for an MOT device between the increasing coil and the counterpart coil, and the sealing member hermetically surrounds a portion of the coil including the most downstream side of the beam axis.

The physics package of the present invention can be used as a physics package for optical lattice clocks, a physics package for atomic clocks, a physics package for atomic interferometers, and a physics package for quantum information processing devices for atoms or ionized atoms.

The sealing member of the present invention is a sealing member that provides a seal for a coil that is installed in a vacuum chamber and wound around the beam axis through which an atomic beam flows, forming a spatially gradient magnetic field, and seals the space between the coil and the side with indium formed into a ring-shaped sheet or thick-walled shape, hermetically surrounding part or all of the coil.

The present invention makes it possible to prevent outgassing from the coil installed inside the vacuum chamber.

1 is a schematic diagram showing the overall configuration of an optical lattice clock according to an embodiment. FIG. 1 is a diagram showing a schematic configuration of a physics package of an optical lattice clock. FIG. 2 is a diagram illustrating an external view of a physics package. FIG. 4 is a partially perspective view showing the inside of the physics package in FIG. 3 . FIG. 2 is a diagram showing the overall shape of a three-axis magnetic field correction coil. FIG. 13 is a diagram showing the shape of a first coil group of X-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a second coil group of the X-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a first coil group of Y-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a second coil group of the Y-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a first coil group of Z-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a second coil group of the Z-axis magnetic field correction coils. FIG. 13 is a diagram showing the shape of a holder for a three-axis magnetic field correction coil. FIG. 13 is a diagram showing an example of a correction coil using a flexible printed circuit board. FIG. 13 is a diagram showing a cylindrical correction coil using a flexible printed circuit board. FIG. 13 is a diagram illustrating an example of a current flowing through a correction coil. FIG. 16 is a diagram showing the current flow equivalent to the correction coil of FIG. 15 . FIG. 13 is a diagram showing another example of a current flowing through a correction coil. FIG. 18 is a diagram showing a current flow equivalent to the correction coil of FIG. 17. FIG. 13 is a diagram showing another example of a correction coil using a flexible printed circuit board. FIG. 1 illustrates a physics package comprising a spherical shaped vacuum chamber. FIG. 13 is a diagram showing another example of installation of the three-axis magnetic field correction coils. 22 is a diagram for explaining a supporting manner of the triaxial magnetic field correction coil in FIG. 21. FIG. 13 is a schematic diagram showing a manner of correction of a magnetic field. FIG. 13 is a schematic diagram showing a manner of correction of a magnetic field. 13 is a flowchart of the calibration of the three-axis magnetic field correction coils. 13 is a flowchart showing a correction procedure for the three-axis magnetic field correction coils. FIG. 11 is a schematic diagram showing another example of a magnetic field correction mode. FIG. 13 is a diagram showing compensation of a leakage magnetic field in a refrigerator. 1 is a cross-sectional view showing the structure of a Zeeman reducer and an MOT device. FIG. 11 is a cross-sectional view illustrating a void in a coil. FIG. 29 is a diagram showing a magnetic field distribution corresponding to the configuration of FIG. 28. 1 is a cross-sectional view showing the structure of a Zeeman reducer and an MOT device. 1 is a cross-sectional view showing the structure of a Zeeman reducer and an MOT device. FIG. 31C is a diagram showing a magnetic field distribution corresponding to the configurations of FIGS. 31A and 31B. FIG. 31C is a diagram showing a structure according to a modified embodiment of FIGS. 31A and 31B. FIG. 31C is a diagram showing a structure according to a modified embodiment of FIGS. 31A and 31B. FIG. 1 is a cross-sectional view of a Zeeman coil with a constant outer diameter. FIG. 11 is a cross-sectional view showing encapsulation of a coil for a Zeeman reducer. FIG. 11 is a cross-sectional view showing encapsulation of a coil for a Zeeman reducer.

(1) Schematic Configuration of the Physics Package Fig. 1 is a schematic diagram showing the overall configuration of an optical lattice clock 10. The optical lattice clock is configured by combining a physics package 12, an optical system device 14, a control device 16, and a PC (Personal Computer) 18.

The physics package 12 is a device that captures an atomic group, confines it in an optical lattice, and causes a clock transition, as described in detail below. The optical device 14 is a device equipped with optical equipment such as a laser emitter, a laser receiver, and a laser spectrometer. The optical device 14 emits a laser and sends it to the physics package 12, and also receives light emitted by the atomic group in the physics package 12 due to the clock transition, converts it into an electrical signal, and performs processing such as splitting it into frequency bands. The control device 16 is a device that controls the physics package 12 and the optical device 14. The control device 16 is a computer specialized for the optical lattice clock 10, and operates by controlling computer hardware equipped with a processor and memory by software. The control device 16, for example, controls the operation of the physics package 12 and the optical device 14, and also performs analysis processing such as frequency analysis of the clock transition obtained by measurement. The physics package 12, the optical device 14, and the control device 16 work closely together to form the optical lattice clock 10.

The PC 18 is a general-purpose computer, and operates by controlling computer hardware equipped with a processor and memory by software. An application program for controlling the optical lattice clock 10 is installed in the PC 18. The PC 18 is connected to the control device 16, and controls not only the control device 16 but also the entire optical lattice clock 10 including the physics package 12 and the optical system device 14. The PC 18 also serves as the UI (User Interface) of the optical lattice clock 10, and the user can start the optical lattice clock 10, measure time, check results, and so on through the PC 18. In this embodiment, the explanation will be centered on the physics package 12. Note that the physics package 12 and the components required for its control may be called a physics package system. The components required for control may be included in the control device 16 or the PC 18, but may also be built into the physics package 12 itself.

Figure 2 is a schematic diagram of the physics package 12 of the optical lattice clock according to the embodiment. Also, Figure 3 is a diagram showing an example of the external appearance of the physics package 12, and Figure 4 is a diagram showing a partial perspective view of the internal structure of the physics package 12 shown in Figure 3. Figures 2 to 4 (and subsequent figures) show an XYZ orthogonal linear coordinate system with the object space (clock transition space 52) in which atoms described below may exist during clock transition spectroscopy as its origin, to clearly indicate the directions.

The physics package 12 includes a vacuum chamber 20, an atomic oven 40, a coil 44 for the Zeeman decelerator, an optical resonator 46, a coil 48 for the MOT device, a low-temperature chamber 54, a thermal link member 56, a refrigerator 58, a vacuum pump main body 60, and a vacuum pump cartridge 62.

The vacuum chamber 20 is a container that keeps the main part of the physics package 12 under vacuum, and is formed in a roughly cylindrical shape. In detail, the vacuum chamber 20 comprises a large, roughly cylindrical main body 22, and a small, roughly cylindrical protrusion 30 that protrudes from the main body 22. The main body 22 is a portion that houses an optical resonator 46 (described later) and the like. The main body 22 comprises a cylindrical wall 24 that forms the side surface of the cylinder, and a front circular wall 26 and a rear circular wall 28 that form the circular surfaces of the cylinder. The front circular wall 26 is a wall on which the protrusion 30 is provided. The rear circular wall 28 is a wall on the opposite side to the protrusion 30, and is formed in a shape with a larger diameter than the cylindrical wall 24.

The protrusion 30 comprises a cylindrical wall 32 that forms the side of the cylinder, and a front circular wall 34. The front circular wall 34 is the circular surface on the side farther from the main body 22. The side of the protrusion 30 facing the main body 22 is mostly open and connected to the main body 22, and does not have a wall.

The vacuum chamber 20 is positioned so that the central axis of the cylinder of the main body 22 (this axis is called the Z-axis) is approximately horizontal. In addition, the central axis of the cylinder of the protrusion 30 (this axis is the beam axis) extends vertically below and parallel to the Z-axis.

The vacuum chamber 20 is expected to be formed, for example, to be approximately 35 cm or less in the Z-axis direction and approximately 20 cm or less in the X-axis and Y-axis directions. It is expected that the length in the Z-axis direction can be further reduced to approximately 30 cm or less, approximately 25 cm or less, or approximately 20 cm or less. It is also expected that it will be possible to reduce the length in the X-axis and Y-axis directions to approximately 15 cm or less, or approximately 10 cm or less. The distance between the beam axis and the Z-axis is set, for example, to approximately 10 to 20 mm.

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) to be sufficiently robust so as to withstand the pressure difference when a vacuum is created inside. The rear circular wall 28 and front circular wall 34 of the vacuum chamber 20 are formed so as to be removable, and are removed during maintenance and inspection.

The atomic oven 40 is a device provided near the tip of the protrusion 30. The atomic oven 40 heats the placed solid metal with a heater, and emits atoms that fly out of the metal due to thermal motion through a fine hole to form an atomic beam 42. The beam axis along which the atomic beam 42 passes is set parallel to the Z axis and is set to intersect with the X axis at a position slightly away from the origin. The intersecting position corresponds to a capture space 50, which is a minute space in which atoms are captured, as described below. The atomic oven 40 is basically provided inside the vacuum chamber 20, but the heat dissipation section extends to the outside of the vacuum chamber 20 for cooling. In the atomic oven 40, the metal is heated to, for example, about 750 K. As the metal, for example, strontium, mercury, cadmium, ytterbium, etc. are selected, but are not limited to these.

The Zeeman decelerator coil 44 is arranged on the downstream side of the beam axis of the atomic oven 40, from the protrusion 30 of the vacuum chamber 20 to the main body 22. The Zeeman decelerator coil 44 is a device that combines a Zeeman decelerator that decelerates the atoms of the atomic beam 42 with an MOT device that captures the decelerated atoms. Both the Zeeman decelerator and the MOT device are devices based on atomic laser cooling technology. The Zeeman decelerator coil 44 shown in FIG. 2 is provided as a series of coils, including a Zeeman coil used in the Zeeman decelerator and one of a pair of MOT coils used in the MOT device. Although it is not possible to make a clear division, roughly speaking, most of the coils from the upstream side to the downstream side correspond to the Zeeman coil that generates a magnetic field that contributes to the Zeeman deceleration method, and the most downstream side corresponds to the MOT coil that generates a gradient magnetic field that contributes to the MOT method.

In the illustrated example, the Zeeman coil is of a decelerating type, with more turns on the upstream side and fewer turns on the downstream side. The Zeeman decelerator coil 44 is arranged axially symmetrically around the beam axis so that the atomic beam 42 passes inside the Zeeman coil and the MOT coil. A spatially gradient magnetic field is formed inside the Zeeman coil, and the atoms are decelerated by irradiating it with a Zeeman deceleration light beam 82.

The optical resonator 46 is a cylindrical part arranged around the Z axis, and an optical lattice is formed inside. The optical resonator 46 is equipped with a pair of optical mirrors on the X axis and another pair of optical mirrors in parallel thereto, and a bowtie-type optical lattice resonator is generated by multiple reflection of the optical lattice light between a total of four mirrors. The atomic group captured in the capture space 50 is confined inside this optical lattice. In addition, in the optical resonator 46, when the relative frequency of the two optical lattice lights (clockwise and counterclockwise) that are input to the resonator is shifted, a moving optical lattice is formed in which the standing wave of the optical lattice moves. The moving optical lattice moves the atomic group to the clock transition space 52. In the embodiment, an optical lattice including a moving optical lattice is set to be formed on the X axis. Note that, as the optical lattice, it is also possible to adopt a two-dimensional or three-dimensional one in which lattices are arranged on one or both of the Y axis and the Z axis in addition to the X axis. In this way, the optical resonator 46 can be said to be an optical lattice forming part that forms an optical lattice. The optical resonator 46 is also a device based on atomic laser cooling technology.

The MOT device coil 48 generates a gradient magnetic field for the capture space 50. In the MOT device, MOT light is irradiated along the three axes X, Y and Z into the space in which the gradient magnetic field is formed. As a result, the MOT device captures atoms in the capture space 50. The capture space 50 is set on the X axis. The Zeeman reducer coil 44 shown in FIG. 2 is provided with a Zeeman coil used in the Zeeman reducer and one of a pair of MOT coils used in the MOT device as a series of coils. In this figure, the gradient magnetic field contributing to the MOT method is generated by combining the MOT device coil 48 and a part of the Zeeman reducer coil 44.

The low-temperature chamber 54 is formed to surround the clock transition space 52, and keeps the inner space at a low temperature. This reduces blackbody radiation in the inner space. A thermal link member 56, which also serves as a support structure, is attached to the low-temperature chamber 54. The thermal link member 56 conducts heat from the low-temperature chamber 54 to the refrigerator 58. The refrigerator 58 is a device that lowers the temperature of the low-temperature chamber 54 via the thermal link member 56. The refrigerator 58 is equipped with a Peltier element, and cools the low-temperature chamber 54 to, for example, about 190K.

The vacuum pump body 60 and the vacuum pump cartridge 62 are devices for evacuating the vacuum chamber 20. The vacuum pump body 60 and the vacuum pump cartridge 62 are devices that subsequently evacuate the vacuum chamber 20. The vacuum pump body 60 is provided outside the vacuum chamber 20, and the vacuum pump cartridge 62 is provided inside the vacuum chamber 20. When the vacuum pump cartridge 62 begins to be started up, it is heated and activated by a heater provided in the vacuum pump body 60. This activates the vacuum pump cartridge 62, which then adsorbs atoms to create a vacuum.

The vacuum pump cartridge 62 is installed in the main body 22 so as to be juxtaposed with the Zeeman reducer coil 44. The Zeeman reducer coil 44 is arranged along a beam axis that is eccentric in the X-axis direction with respect to the central axis of the cylinder of the main body 22. Therefore, there is a relatively large space on the opposite side to the eccentric direction of the Zeeman reducer coil 44. The vacuum pump cartridge 62 is installed in this space.

The physics package 12 includes vacuum-resistant optical windows 64, 66 for optical lattice light, a vacuum-resistant optical window 68 for MOT light, vacuum-resistant optical windows 70, 72 for Zeeman deceleration light and MOT light, and optical mirrors 74, 76 as optical system components.

The vacuum-resistant optical windows 64, 66 for the optical lattice light are vacuum-resistant optical windows provided facing the opposing cylindrical walls 24 in the main body 22 of the vacuum chamber 20. The vacuum-resistant optical windows 64, 66 for the optical lattice light are provided to allow the optical lattice light to enter and exit.

The vacuum-resistant optical window 68 for MOT light is provided to allow two of the three axes of MOT light used in the MOT device to enter and exit.

The vacuum-resistant optical windows 70, 72 for Zeeman-decelerated light and MOT light are provided for the input and output of Zeeman-decelerated light and one-axis MOT light.

Optical mirrors 74 and 76 are provided to change the direction of the Zeeman deceleration light and the one-axis MOT light.

The physics package also includes cooling components, such as a cooler 90 for the atomic oven, a cooler 92 for the Zeeman decelerator, and a cooler 94 for the MOT device.

The atomic oven cooler 90 is a water-cooling device that cools the atomic oven 40. The atomic oven cooler 90 is provided outside the vacuum chamber 20, and cools the heat dissipation portion of the atomic oven 40 that extends outside the vacuum chamber 20. The atomic oven cooler 90 is equipped with a metallic water-cooled pipe that is a cooling pipe, and cools the vacuum chamber 20 by flowing cooling water, which is a liquid refrigerant, inside the pipe.

The Zeeman reducer cooler 92 is provided on the wall of the vacuum chamber 20 and is a device that cools the Zeeman reducer coil 44. The Zeeman reducer cooler 92 is equipped with a metal pipe, and by running cooling water through it, it removes Joule heat generated in the coil of the Zeeman reducer coil 44.

The MOT device cooler 94 is a heat dissipation unit provided in the circular wall of the vacuum chamber 20. In the MOT device coil 48, Joule heat is generated in the coil, although it is smaller (e.g., about 1/10) than the Zeeman reducer cooler 92. Therefore, the metal of the MOT device cooler 94 extends from the MOT device coil 48 to the outside of the vacuum chamber 20 and releases heat into the atmosphere.

The physics package 12 further includes components for correcting the magnetic field, such as a three-axis magnetic field compensation coil 96, a vacuum-resistant electrical connector 98, an individual magnetic field compensation coil 102 for the refrigerator, and an individual magnetic field compensation coil 104 for the atomic oven.

The three-axis magnetic field correction coil 96 is a coil for uniformly zeroing out the magnetic field in the clock transition space 52. The three-axis magnetic field correction coil 96 is formed in a three-dimensional shape so as to correct the magnetic fields in the three axial directions of X, Y and Z. In the example shown in FIG. 4, the three-axis magnetic field correction coil 96 is formed in an approximately cylindrical shape as a whole. Each coil constituting the three-axis magnetic field correction coil 96 is formed in a point-symmetric shape in each axial direction with the clock transition space 52 as the center.

The vacuum-resistant electrical connector 98 is a connector for supplying power into the vacuum chamber 20 and is provided 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 three-axis magnetic field correction coil 96.

The refrigerator individual magnetic field compensation coil 102 is a coil for compensating for the leakage magnetic field from the refrigerator 58 that cools the low-temperature bath 54. The Peltier element provided in the refrigerator 58 is a high-current device through which a relatively large current flows, and generates a large magnetic field. The Peltier element is surrounded by a high-permeability material to shield the magnetic field, but it is not completely shielded and some of the magnetic field leaks out. Therefore, the refrigerator individual magnetic field compensation coil 102 is set to compensate for this leakage magnetic field in the clock transition space 52.

The individual magnetic field compensation coil 104 for the atomic oven is a coil for compensating for the leakage magnetic field from the heater of the atomic oven 40. The heater of the atomic oven 40 is also a large current device, and the leakage magnetic field may not be negligible despite shielding by a high magnetic permeability material. For example, even if the heater circuit is constructed with non-inductive winding wiring, inductive components may actually remain in the wiring terminals and wiring through an insulating layer. Also, for example, even if the atomic oven is covered with a high magnetic permeability material to achieve magnetic shielding, there may be parts that cannot actually be covered, such as the atomic beam opening. Therefore, the individual magnetic field compensation coil 104 for the atomic oven is set to compensate for this leakage magnetic field in the clock transition space 52.

(2) Operation of the Physics Package The basic operation of the physics package 12 will be described. In the physics package 12, the vacuum pump cartridge 62 provided inside the vacuum chamber 20 adsorbs atoms, and the inside of the vacuum chamber 20 is evacuated. As a result, the inside of the vacuum chamber 20 is in a vacuum state of, for example, about 10 ⁻⁸ Pa, and the influence of air components such as nitrogen and oxygen is eliminated. Pretreatment is performed in advance depending on the type of vacuum pump to be used. For example, in the case of a non-evaporable getter pump (NEG pump) or an ion pump, it is necessary to roughly evacuate the atmosphere to a certain degree of vacuum before operating it. In this case, a roughing port is provided in the vacuum chamber, and sufficient roughing is performed from the port using, for example, a turbo molecular pump. In addition, for example, when an NEG pump is used as the vacuum pump main body 60, a process of activation in which the pump is heated to a high temperature in a vacuum must be performed in advance.

In the atomic oven 40, the metal is heated by the heater to a high temperature, generating atomic vapor. The atomic vapor released from the metal in this process passes through the pores one after another, is focused and translated, and forms an atomic beam 42. The atomic oven 40 is installed so that the atomic beam 42 is formed on a beam axis parallel to the Z axis. In the atomic oven 40, the atomic oven body is heated by the heater, but the atomic oven body and the joints supporting it are thermally insulated via thermal insulators, and the joints connected to the physics package are cooled by the atomic oven cooler 90, preventing or reducing the effect of high temperatures on the physics package 12.

The Zeeman decelerator coil 44 is installed so as to be axially symmetrical with respect to the beam axis. The Zeeman decelerator coil 44 is irradiated with a Zeeman decelerated light beam 82 and a one-axis MOT light beam 84. The Zeeman decelerated light beam 82 is incident from a vacuum-resistant optical window 70 for Zeeman decelerated light and MOT light, and is reflected by an optical mirror 74 installed downstream of the beam from the MOT device coil 48. As a result, the Zeeman decelerated light beam 82 overlaps with the atomic beam 42 and travels upstream of the beam axis almost parallel to the beam axis. In this process, the atoms in the atomic beam 42 absorb the Zeeman decelerated light and are given momentum in the decelerating direction and decelerate due to the effect of Zeeman splitting proportional to the strength of the magnetic field and the effect of Doppler shift. The Zeeman decelerated light is reflected by an optical mirror 76 placed to the side of the beam axis upstream of the Zeeman decelerator coil 44, and is emitted from a vacuum-resistant optical window 72 for Zeeman decelerated light and MOT light. Note that Joule heat is generated in the Zeeman decelerator coil 44, but it is cooled by the Zeeman decelerator cooler 92, so it is prevented from becoming too hot.

The sufficiently decelerated atomic beam 42 reaches the MOT device formed by the MOT coil on the most downstream side of the Zeeman decelerator coil 44 and the MOT device coil 48. Inside the MOT device, a magnetic field with a linear spatial gradient is formed around the trapping space 50. In addition, the MOT device is irradiated with MOT light from the positive and negative sides in three axial directions.

The MOT light beam 84 in the Z-axis direction is irradiated in the negative direction of the Z-axis, and is also irradiated in the positive direction of the Z-axis by being reflected outside the vacuum-resistant optical window 72 for Zeeman deceleration light and MOT light. The remaining two MOT light beams 86a and 86b are irradiated into the MOT device by the vacuum-resistant optical window 68 for MOT light and an optical mirror (not shown). As shown in FIG. 4, these two axes are irradiated in two directions perpendicular to the Z-axis and at 45 degrees to the X-axis and Y-axis, respectively. By making the two MOT light beams 86a and 86b perpendicular to the Z-axis, the distance between the Zeeman deceleration coil 44 and the MOT device coil 48 can be narrowed, which contributes to the miniaturization of the vacuum chamber 20. When the direction of irradiation of the MOT light beam is set at an angle of 45 degrees to the Z-axis and Y-axis, it is necessary to increase the distance in the beam axis direction so that the MOT light beam does not interfere with the Zeeman decelerator or the cryostat. In this case, the size of the device becomes larger than when the two axes of the MOT light are perpendicular to the Z-axis.

In the MOT device, the atomic beam is decelerated by a restoring force caused by the magnetic field gradient around the trapping space 50. This causes the atomic group to be trapped in the trapping space 50. The position of the trapping space 50 can be fine-tuned by adjusting the offset value of the magnetic field generated by the three-axis magnetic field correction coil 96. Joule heat generated in the MOT device coil 48 is discharged outside the vacuum chamber 20 by the MOT device cooler 94.

The optical lattice light beam 80 is incident on the X-axis from the vacuum-resistant optical window 64 for optical lattice light to the vacuum-resistant optical window 66 for optical lattice light. An optical resonator 46 equipped with two optical mirrors is installed on the X-axis, causing reflection. Therefore, on the X-axis, an optical lattice potential is formed inside the optical resonator 46, with standing waves connected in the X-axis direction. The atomic group is captured by the optical lattice potential.

The optical lattice can be moved along the X-axis by slightly changing the wavelength. The atomic group is moved to the clock transition space 52 by this moving optical lattice. As a result, the clock transition space 52 is moved out of the beam axis of the atomic beam 42, and the effects of blackbody radiation emitted by the high-temperature atomic oven 40 can be eliminated. The clock transition space 52 is also surrounded by a low-temperature chamber 54, and is shielded from blackbody radiation emitted by the surrounding room-temperature materials. Generally, blackbody radiation is proportional to the fourth power of the absolute temperature of the material, so lowering the temperature by the low-temperature chamber 54 is highly effective in eliminating the effects of blackbody radiation.

In the clock transition space 52, an atom is irradiated with laser light with a controlled optical frequency, and the clock transition (i.e., the atomic resonance transition that serves as the clock reference) is analyzed with high precision to measure the specific and invariant frequency of the atom. This realizes an accurate atomic clock. To improve the accuracy of an atomic clock, it is necessary to eliminate the perturbations surrounding the atom and accurately read out the frequency. What is particularly important is to remove the frequency shift caused by the Doppler effect due to the thermal motion of the atom. In an optical lattice clock, the movement of the atom is frozen by confining the atom in an optical lattice created by the interference of laser light in a space that is sufficiently smaller than the wavelength of the clock laser. On the other hand, within the optical lattice, the frequency of the atom is shifted by the laser light that forms the optical lattice. Therefore, a specific wavelength/frequency called the "magic wavelength" or "magic frequency" is selected as the optical lattice light beam 80 to eliminate the effect of the optical lattice on the resonance frequency.

The clock transition is also affected by the magnetic field. Atoms in a magnetic field undergo Zeeman splitting according to the strength of the magnetic field, making it impossible to accurately measure the clock transition. Therefore, in the clock transition space 52, the magnetic field is corrected to make the magnetic field uniform and zero. First, the leakage magnetic field caused by the Peltier element of the refrigerator 58 is dynamically compensated for by the refrigerator individual magnetic field compensation coil 102, which generates a compensation magnetic field according to the magnitude of the leakage magnetic field. Similarly, the leakage magnetic field caused by the heater of the atomic oven 40 is set so that it can be dynamically compensated for by the atomic oven individual magnetic field compensation coil 104. Note that, for the Zeeman reducer coil 44 and the MOT device coil 48, the current signal is turned OFF at the timing when the frequency of the clock transition is measured, so that they are not affected by the magnetic field. The magnetic field in the clock transition space 52 is further corrected by the three-axis magnetic field correction coil 96. A plurality of three-axis magnetic field correction coils 96 are provided in the direction of each axis, and it is possible to remove not only the uniform component of the magnetic field but also the spatially changing component.

In this way, with disturbances removed, the atomic ensemble is induced to undergo a clock transition by the laser light. The light emitted as a result of the clock transition is received by an optical system device and subjected to spectroscopic processing by a control device to determine the frequency. An embodiment of the physics package 12 is described in detail below.

5 to 11, the triaxial magnetic field correction coil 96 in the physics package 12 will be described. Here, it is assumed that the triaxial magnetic field correction coil 96 is formed into a predetermined shape by winding a coated conductor insulated with polyimide resin or the like around a conductor such as copper.

Figure 5 is a perspective view showing all the coils of the triaxial magnetic field correction coil 96. Figures 6 to 11 are perspective views showing the individual coils that make up the triaxial magnetic field correction coil. The triaxial magnetic field correction coil 96 is attached near the inner wall of the main body 22 of the vacuum chamber 20. For this reason, the triaxial magnetic field correction coil 96 is formed in a substantially cylindrical shape with the clock transition space 52 at its center. The triaxial magnetic field correction coil 96 is formed by a first coil group and a second coil group in each of the X-axis, Y-axis, and Z-axis directions, respectively.

Figure 6 is a diagram showing the first coil group 120 in the X-axis direction (the direction in which a one-axis optical lattice is formed and the direction in which the moving optical lattice moves). The first coil group 120 consists of two coils 122, 124 that are placed a distance c apart in the X-axis direction, with the clock transition space 52 at the center. Both coils 122, 124 are formed in a rectangular shape with the side length in the Y-axis direction set to a and the side length in the Z-axis direction set to b. Furthermore, coils 122, 124 are formed in a shape that is point-symmetric with respect to the clock transition space 52.

In the first coil group 120, the coils 122 and 124 are formed as square Helmholtz coils so that the magnetic field in the X-axis direction at the center can be generated approximately uniformly. A square Helmholtz coil refers to a coil in which the coils 122 and 124 are formed as a square with a = b and c/2a = approximately 0.5445. When currents of the same magnitude are passed through the coils 122 and 124 in the same direction, the coils 122 and 124 become a Helmholtz coil pair that forms a magnetic field with high uniformity in the X-axis direction. However, in the embodiment, currents of different magnitudes and directions can be passed through the coils 122 and 124. Note that the coils 122 and 124 can sufficiently increase the uniformity of the magnetic field even when a ≠ b. When a>b, the deviation of the magnetic field distribution in the Y-axis direction tends to be smaller than that in the Z-axis direction, and when a<b, the deviation of the magnetic field distribution in the Z-axis direction tends to be smaller than that in the Y-axis direction. When a ≠ b, the coil with c optimized is called a rectangular Helmholtz coil. It is also possible for the first coil group 120 to be a rectangular Helmholtz coil.

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 current magnitude is passed through the 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 current magnitude is passed through the coils 122 and 124 in the opposite directions, a magnetic field with an almost uniform gradient in the X-axis direction is formed in the clock transition space 52. Then, when the magnitude and direction of the current passed through the coils 122 and 124 are appropriately changed, 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 for the magnetic field component Bx in the X-axis direction in the clock transition space 52.

7 is a diagram showing the second coil group 130 in the X-axis direction. The second coil group 130 is composed of two coils 132 and 134 that are installed at a distance in the X-axis direction with the clock transition space 52 as the center. The coils 132 and 134 are formed in a shape that is deformed by giving a curvature to a rectangular coil so that it fits on the same cylindrical surface of radius e, and 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 radius approximately the same as that of the cylindrical surface to which the first coil group 120 in FIG. 6 is fixed, so that there is a relationship of e ² ≒ (a/2) ² + (c/2) ^2. In addition, the coils 132 and 134 are formed in a shape that is point-symmetric with respect to the clock transition space 52.

The second coil group 130 is a non-Helmholtz coil with a different shape from the Helmholtz coil. The coils 132 and 134 of the second coil group are electrically connected, and currents of the same magnitude flow in the same direction. That is, currents flow in both coils 132 and 134 in the direction of arrow 136, or currents flow in both coils 132 and 134 in the direction of arrow 138. Since the second coil group 130 is a non-Helmholtz coil, in addition to the uniform component equivalent to the Helmholtz coil, a non-uniform component is also generated in the central clock transition space 52. However, since the magnitude and direction of the current are the same, the non-uniform component is mainly a component of the spatial second derivative term. That is, the second coil group 130 can correct the constant term component and the spatial second derivative term in the X-axis direction for the magnetic field component Bx in the X-axis direction in the clock transition space 52.

Of the three-axis magnetic field correction coils 96, the first coil group 120 and the second coil group 130 in the X-axis direction basically control the magnetic field component Bx in the X-axis direction. Therefore, these are collectively referred to as the X-axis magnetic field correction coils. When making the correction, the second coil group 130 first sets the value of the spatial second-order differential term in the X-axis direction to zero. Next, the first coil group 120 sets the value of the spatial first-order differential term in the X-axis direction to zero, and adjusts the value of the constant term in the X-axis direction to zero.

Figure 8 is a diagram showing the first coil group 140 in the Y-axis direction. The first coil group 140 is formed so that the rectangular coil is deformed to have a curvature and is placed on a cylindrical surface of radius h centered on the clock transition space 52. The first coil group includes a composite coil 142 consisting of coils 143 and 144, and a composite coil 145 consisting of coils 146 and 147, which are installed at a distance in the Y-axis direction. The coils 143, 144, 146, and 147 are set to a central angle of i and a height in the Z-axis direction of j. The coils 143 and 144 are formed with their ends overlapping or adjacent to each other. Similarly, the coils 146 and 147 are formed with their ends overlapping or adjacent to each other. The composite coil 142 and the composite coil 145 are formed point-symmetrically with the clock transition space 52 as the center. Additionally, coils 143 and 146, and coils 144 and 147 are also formed point-symmetrically with respect to clock transition space 52.

First, consider 3) the case where currents of the same magnitude are passed through the coils 143 and 144 in the same direction. In this case, the currents of the overlapping or adjacent parts cancel each other out, and the entire composite coil 142 behaves like one large coil. Similarly, when currents of the same magnitude are passed through the coils 146 and 147 in the same direction, the entire composite coil 145 behaves like one large coil. The first coil group 140 is set so that the composite coils 142 and 145 form a pair of Helmholtz-type coils. The Helmholtz-type coil on a cylindrical surface shown in FIG. 8 (i.e., a Helmholtz-type coil in which two square coils are bent and placed on the same cylindrical surface) has a central angle set to about 120 degrees. The length in the Z-axis direction is not particularly limited, but it is known that the longer the length in the Z-axis direction is compared to the radius of the cylinder, the higher the magnetic field uniformity in 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 passed through it.

Next, 4) make some changes to the current when forming a Helmholtz coil. Specifically, only the current in coils 143 and 147 is made slightly larger in the same direction. In this case, the Y-axis component of the magnetic field has the value of the spatial first derivative term in the X-axis direction. Strictly speaking, the magnetic field created by coils 143 and 147 also has an X-axis component, and when adjusting the first coil group 140, it is also necessary to adjust the X-axis magnetic field correction coil.

Figure 9 is a diagram showing the second coil group 150 in the Y-axis direction. The second coil group 150 shown in Figure 9 consists of a pair of coils 152, 154 facing each other in the Y-axis direction. Each of the coils 152, 154 is a non-Helmholtz type coil formed by giving a curvature to a circular coil of radius k and placing it on a cylindrical surface of radius l centered on the clock transition space 52. In a non-Helmholtz type coil, a component of the spatial second derivative term of the magnetic field is also formed. Therefore, the second coil group 150 is used to control the spatial second derivative term in the X-axis direction of the magnetic field component By in the Y-axis direction.

The first coil group 140 in the Y-axis direction shown in FIG. 8 and the second coil group 150 in the Y-axis direction shown in FIG. 9 basically form a Y-axis magnetic field correction coil that corrects the magnetic field component By in the Y-axis direction. The Y-axis magnetic field correction coil can correct the constant term of the magnetic field component By in the Y-axis direction, the spatial first-order differential term in the X-axis direction, and the spatial second-order differential term in the X-axis direction.

Figure 10 is a diagram showing the first coil group 160 in the Z-axis direction. In the first coil group 160, circular composite coils 162 and 165 with a radius of m are arranged facing each other at a distance n. The composite coils 162 and 165 are in a point-symmetric relationship with respect to the center. The composite coil 162 is formed by overlapping or adjacent to the strings of the semicircular coils 163 and 164. The semicircular coil 163 is arranged on the positive side of the X-axis, and the semicircular coil 164 is arranged on the negative side of the X-axis. Similarly, the composite coil 165 is formed by combining a semicircular coil 166 on the positive side of the X-axis and a semicircular coil 167 on the negative side of the X-axis.

The size of the composite coils 162 and 165 is set so that they are Helmholtz-type coils. A circular Helmholtz coil has a relationship of m = n. The composite coils 162 and 165 are set in a range in which the uniformity of the magnetic field in the Z direction near the center is substantially equivalent to that of a Helmholtz coil when currents of the same magnitude and direction are passed through both of them. However, the direction and magnitude of the current can be freely changed in the coils 163 and 164 that make up the composite coil 162. Therefore, in the same way as the first coil group 140 in the Y direction shown in Figure 8, the first coil group 160 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.

Figure 11 is a diagram showing the second coil group 170 in the Z-axis direction. The second coil group 170 is made up of circular coils 172 and 174 of radius p, which are arranged facing each other and spaced a distance q apart in the Z-axis direction. The second coil group 170 is a non-Helmholtz type coil. A non-Helmholtz type coil has non-uniform components. For this reason, it is possible to correct the spatial second derivative term in the X-axis direction of the magnetic field component Bz in the Z-axis direction.

The first coil group 160 in the Z-axis direction shown in FIG. 10 and the second coil group 170 in the Z-axis direction shown in FIG. 11 basically form a Z-axis magnetic field correction coil that corrects the magnetic field component Bz in the Z-axis direction. The Z-axis magnetic field correction coil can correct the constant term of the magnetic field component Bz in the Z-axis direction, the spatial first-order differential term in the X-axis direction, and the spatial second-order differential term in the X-axis direction.

The three-axis magnetic field correction coil 96 shown in FIG. 5 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 three-axis magnetic field correction coil 96 can correct the constant term, the spatial first-order differential term in the X-axis direction, and the spatial second-order differential term in the X-axis direction for the magnetic field component Bx in the X-axis direction. The three-axis magnetic field correction coil 96 can correct the constant term, the spatial first-order differential term in the X-axis direction, and the spatial second-order differential term in the X-axis direction for the magnetic field component By in the Y-axis direction. And, the constant term, the spatial first-order differential term in the X-axis direction, and the spatial second-order differential term in the X-axis direction for the magnetic field component Bz in the Z-axis direction can be corrected.

The three-axis magnetic field correction coil 96 performs correction to uniformly set the magnetic field value in the clock transition space 52 to zero. In the case of a one-dimensional optical lattice, the clock transition space 52 is set to a size of, for example, 10 mm in the X-axis direction (lattice direction) and 1 to 2 mm in the Y-axis and Z-axis directions. The magnetic field in this space is controlled so that the magnetic field error is within 3 μG, 1 μG, or 0.3 μG, for example. The Helmholtz-type coils and non-Helmholtz-type coils used in the three-axis magnetic field correction coil 96 are set to a precision that allows them to form this magnetic field.

As shown in FIG. 4, the three-axis magnetic field correction coil 96 is formed in a shape that has point symmetry with respect to the clock transition space 52, and it is possible to perform accurate magnetic field correction of the clock transition space 52. However, from a macroscopic perspective, the trapping space 50 is also located near the center of the three-axis magnetic field correction coil. Therefore, it can also be used to correct the magnetic field of the trapping space 50 by the MOT device. That is, during the period when the MOT device is started and atoms are captured from the atomic beam 42, the current is controlled to perform magnetic field correction of the trapping space 50. Then, after the capture is completed, the power transmission to the Zeeman decelerator coil 44 and the MOT device coil 48 is stopped, and the magnetic field correction of the clock transition space 52 is performed. In this way, it is possible to adjust the position of the trapping space 50 with high precision and efficiently confine the atomic group in the optical lattice.

Figure 12 is a diagram showing a cylindrical holder 180 to which the three-axis magnetic field correction coil 96 is attached. The holder 180 is formed by connecting annular frames 182, 184 with eight linear frames 186. The three-axis magnetic field correction coil 96 is attached to the inner and outer walls of the holder 180. The holder 180 is then fixed to the rear circular wall 28 of the main body 22 of the vacuum chamber 20. By attaching the three-axis magnetic field correction coil 96 to the holder 180, the assembly and maintenance work of the physics package 12 is made more efficient.

The holder 180 is formed using a low magnetic permeability material such as resin or aluminum so as not to affect the magnetic field generated by the triaxial magnetic field correction coil 96. The holder 180 is installed inside the main body 22, coaxial with the central axis of the cylinder of the main body 22. The holder 180 is formed to a size close to the inner diameter of the main body 22. Therefore, the triaxial magnetic field correction coil 96 and the holder 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 attached linearly across the inside of the main body 22.

The holder 180 is formed into a sparse structure using a frame. A sparse structure is a structure in which there are many gaps on each surface. By making the holder 180 into a sparse structure, it is possible to reduce the weight and also to easily prevent interference with laser light and the like that enters and leaves the vacuum chamber 20.

Instead of distributing the three-axis magnetic field correction coils 96 on the inner and outer walls of the holder 180, for example, all of the three-axis magnetic field correction coils 96 may be attached to the inner wall of the holder 180, or all of the three-axis magnetic field correction coils 96 may be attached to the outer wall of the holder 180. In this case, the three-axis magnetic field correction coils 96 can be easily fixed using, for example, a ring-shaped fastener that presses the three-axis magnetic field correction coils 96 against the outer wall, or a ring-shaped fastener that presses the three-axis magnetic field correction coils 96 against the inner wall. The three-axis magnetic field correction coils 96 can also be fixed to the inner wall of the main body 22 without using the holder 180.

The three-axis magnetic field correction coil 96 described above is assumed to be formed by winding a coated conductor wire one or more times. However, the three-axis magnetic field correction coil 96 can be formed in part or in whole from a flexible printed circuit board.

Figure 13 is a diagram showing a flexible printed circuit board developed on a plane. A correction coil 190 is formed on the flexible printed circuit board. The correction coil 190 is made of a current path 192 made of printed copper or other electrical conductor that participates in the formation of a magnetic field, and an insulating part 194 made of a sheet-like flexible resin or the like, and can be flexibly bent. Each current path 192 is connected to a wiring path 196 that is provided in a concentrated manner at one end. The wiring path 196 is also formed by printing an electrical conductor. The wiring path is arranged in pairs adjacent to each other, through which current travels back and forth, to cancel out the magnetic field formed in the surrounding area. The wiring path 196 is connected to a terminal connector 198.

Figure 14 shows a correction coil 190 bent into a cylindrical shape to fit the main body 22 of the vacuum chamber 20. The correction coil 190 has a boundary portion 199 where two ends are connected or adjacently arranged. Note that the wiring path 196 and the terminal connector 198 are omitted in Figure 14.

Like the above-mentioned three-axis magnetic field correction coil 96 wound with coated conductor wire, the three-axis magnetic field correction coil made of a flexible printed circuit board is also assumed to be attached to the cylindrical inner wall of the main body 22 or the cylindrical holder 180. However, in the three-axis magnetic field correction coil 96, in addition to the current path arranged on the cylindrical surface, there is a current path that is free from the cylindrical surface. Specifically, the side of length a in the first coil group 120 in the X-axis direction shown in FIG. 6 and the straight part of the first coil group 160 in the Z-axis direction shown in FIG. 10 are free from the cylindrical surface. Therefore, in the following, an example will be described in which the current path arranged on the cylindrical surface among the current paths that make up the three-axis magnetic field correction coil 96 is formed from a flexible printed circuit board.

Figures 15 and 16 are diagrams showing an example in which the coils of the circular portion of the first coil group 160 in the Z-axis direction shown in Figure 10 are formed from a flexible printed circuit board. As shown in Figure 15, a counterclockwise current flows through the black current path 202, and no current flows through the gray current path 200. Considering that adjacent currents flowing in opposite directions cancel each other out, this is considered to be equivalent to the case in which a current flows through the virtual current path 203 shown in Figure 16.

Figures 17 and 18 are diagrams showing an example in which the outermost coils in the first coil group 140 in the Y-axis direction shown in Figure 8 are formed from a flexible printed circuit board. In Figure 17, a counterclockwise current flows through the current path 206 shown by the black line, and no current flows through the current path 204 shown by the gray line. Considering that adjacent currents flowing in opposite directions cancel each other out, this is considered to be equivalent to the case in which a current flows through the virtual current path 208 shown in Figure 18.

In this way, various current paths can be formed in a flexible printed circuit board, such as a current path that circulates around the outer periphery of the cylindrical surface, around the central axis of the cylinder, and a current path that circulates within the cylindrical surface without circling around the central axis of the cylinder.

In the flexible printed circuit board, a pattern consisting of a rectangular current path in the development view can be printed as shown in FIG. 13. Also, a composite pattern including a rectangular current path 212 and a circular current path 214 can be printed as shown in FIG. 19, as in the correction coil 210. In the physics package 12, since a laser light path, a vacuum-resistant optical window, etc. are provided near the wall surface of the vacuum chamber 20, it is effective to provide a circular current path 214 to prevent interference. Also, in the flexible printed circuit board, coils such as those shown in FIG. 16 and FIG. 18 may be formed. Also, multiple flexible printed circuit boards can be used by stacking them, and multiple sheets can be used to form part or all of the three-axis magnetic field correction coil.

In flexible printed circuit boards, a small amount of gas may be released from the resin of the insulating section 194. Therefore, a material that releases a small amount of gas, such as a polyimide resin, is selected for the insulating section 194. In addition, during the manufacturing process, degassing, defoaming, cleaning, etc. may be performed, and baking at an appropriate temperature may also be performed.

The triaxial magnetic field correction coil formed from a flexible printed circuit board can be installed in the vacuum chamber 20 in various forms. For example, the triaxial magnetic field correction coil can be bent into a cylindrical shape and installed near the inner wall surface of the main body 22, and fixed with a fastener that presses the triaxial magnetic field correction coil against the main body 22. Alternatively, it may be installed by attaching it to the holder 180. Instead of the sparsely structured holder 180, a densely structured holder with few holes on its surface may be used so that the flexible printed circuit board can be supported over a surface area.

On the other hand, the current path that is free from the cylindrical surface can be formed separately using coated conductor wire. Alternatively, by changing the structure of the holder, it is possible to form the current path that is free from the cylindrical surface using a flexible printed circuit board.

A three-axis magnetic field correction coil using a flexible printed circuit board is easier to install in the vacuum chamber 20 than a three-axis magnetic field correction coil 96 wound with coated conductor wire, and has other advantages, such as high manufacturing reproducibility and improved product yield.

The coil shape of the three-axis magnetic field correction coil can be set in various other ways. For example, a Maxwell-type three-axis magnetic field correction coil can be formed by arranging a large circular coil between two circular coils on each of the three axes. In a Maxwell-type three-axis magnetic field correction coil, the constant term, the spatial first derivative term, and the spatial second derivative term of the magnetic field can be corrected.

Furthermore, a tetrahedral axial magnetic field correction coil can be formed by placing small circular coils of a specified size and spacing on the outside of a pair of large circular coils of a specified size and spacing on each of the three axes. A tetrahedral three-axis magnetic field correction coil makes it possible to correct the components of the constant term, the spatial first-order differential term, the spatial second-order differential term, and the spatial third-order differential term.

The axial magnetic field correction coils shown above have an overall spherical or slightly distorted spherical shape. Therefore, by attaching them to or near the inner wall of a vacuum chamber that is approximately spherical, it becomes possible to effectively utilize the internal space of the vacuum chamber.

Figure 20 corresponds to Figure 4 and is a diagram showing the exterior and interior of the physics package 218. The same reference numerals are used for configurations that are the same as or correspond to those in Figure 4. The vacuum chamber 220 of the physics package 218 is formed by a substantially spherical main body portion 222 and a protrusion portion 30.

Inside the main body 222, a three-axis magnetic field correction coil 224 is provided, which is formed of a circular coil and is centered on the clock transition space 52. For the sake of simplicity, FIG. 20 only illustrates a pair of Helmholtz-type coils in each axial direction, but in reality, it is assumed that one or more pairs of non-Helmholtz-type coils are also provided on each axis. The outer edge of the three-axis magnetic field correction coil 224 can be set to be approximately spherical. Therefore, by installing it near the inner wall of the approximately spherical main body 222, it is possible to prevent interference with other components installed in the internal space of the main body 222, and the degree of design freedom is also increased.

Similarly, a three-axis magnetic field correction coil can also be constructed using square coils. As with the circular coil, a Helmholtz-type three-axis magnetic field correction coil using a pair of square coils, a Maxwell-type three-axis magnetic field correction coil using three square coils, a tetrahedral-type three-axis magnetic field correction coil using two pairs of square coils, etc. can be used. These three-axis magnetic field correction coils have an overall cube or a slightly distorted cube shape. Therefore, by attaching them to the inner wall or inner wall surface of a vacuum chamber that is approximately cubic or approximately rectangular, it is possible to effectively utilize the internal space of the vacuum chamber.

The three-axis magnetic field correction coil can also be attached closer to the clock transition space 52 than the inner wall of the main body 22. FIG. 21 is a simplified diagram showing the inner side of the optical resonator 46 shown in FIG. 1. However, in FIG. 21, instead of the three-axis magnetic field correction coil 96 in FIG. 1, a cube-shaped three-axis magnetic field correction coil 230 is provided in the space between the Zeeman decelerator coil 44 and the MOT device coil 48. The three-axis magnetic field correction coil 230 is arranged around the clock transition space 52 inside the cryostat 54. The three-axis magnetic field correction coil 230 is formed of two pairs of coil groups consisting of square coils in all three axial directions. One pair of the two pairs of coil groups is a Helmholtz type coil, and the other pair is a non-Helmholtz type coil. The three-axis magnetic field correction coil 230 can compensate for magnetic field components up to the spatial third differential term when the magnitude and direction of the current are not particularly limited. Alternatively, if currents of the same magnitude are passed in the same direction, as in the non-Helmholtz type coils of the three-axis magnetic field correction coils 96 shown in Figures 5 to 11, magnetic field components up to the spatial second derivative term can be easily compensated for.

The three-axis magnetic field correction coil 230 is very small and close to the clock transition space 52 compared to the three-axis magnetic field correction coil 96 shown in Figures 5 to 11. Therefore, the magnetic field formed in the clock transition space 52 changes on a relatively small spatial scale. However, the three-axis magnetic field correction coil 230 can compensate for the constant term component and the spatial first differential term component over a relatively wide range by using a Helmholtz-type coil. In addition, the non-Helmholtz-type coil can also compensate for at least the magnetic field component of the spatial second differential term. Therefore, the magnetic field in the clock transition space 52 is uniformly zeroed out with sufficiently high accuracy. In addition, since the three-axis magnetic field correction coil 230 is located close to the clock transition space 52, it is possible to make the current flowing to form the magnetic field very small, and it is excellent in power saving.

22 is a side view seen from the direction of A in FIG. 21. As shown in FIG. 22, two MOT light beams 86a and 86b are irradiated into the trapping space 50, which are perpendicular to the Z axis and form angles of 45 degrees with the X axis and Y axis, respectively. In addition, an MOT light beam 84 is also irradiated in a direction perpendicular to the paper surface. In order to adjust the gradient magnetic field formed in and around this trapping space 50, a bias coil 234 is arranged with the trapping space 50 at its center. The bias coil 234 is composed of 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 a desired distribution by adjusting the constant term component or the spatial first-order differential term component by the coils of each axis.

The X-axis passing through the capture space 50 is irradiated with an optical lattice light beam 80. The cryostat 54, which includes the clock transition space 52, is provided on this optical lattice light beam 80. The three-axis magnetic field correction coil 230 is provided around the cryostat 54, with the clock transition space 52 at the center. The three-axis magnetic field correction coil 230 is composed of a coil group 230b whose surface normal is parallel to the Z-axis, and two coil groups 230a and 230c whose surface normals are perpendicular to the Z-axis and form a 45-degree angle with the X-axis and Y-axis. In other words, the three-axis magnetic field correction coil 230 is arranged in a state where a cube shape along the X-axis, Y-axis, and Z-axis is rotated 45 degrees around the Z-axis.

The three-axis magnetic field correction coil 230 is supported by flanges 44a and 48a, which are support members that support the MOT device. Therefore, the three-axis magnetic field correction coil 230 needs to be placed close to the capture space 50, which is the center of the MOT device. On the other hand, the three-axis magnetic field correction coil 230 needs to be placed so as to avoid interference with the MOT light beams 86a and 86b passing through the capture space 50. Therefore, the three-axis magnetic field correction coil 230 is placed in a shape that is aligned with the Z axis and the MOT light beams 86a and 86b.

The three-axis magnetic field correction coil 230 is equipped with a Helmholtz coil and a non-Helmholtz coil in each axial direction, and is capable of homogenizing the magnetic field over a wide space, including correcting spatial higher-order differential terms. This makes it possible to correct the magnetic field with high precision even in the X-axis direction, which is the direction of the optical lattice light beam 80.

However, because the three-axis magnetic field correction coil 230 does not surround the capture space 50, it is not possible to perform magnetic field correction for the capture space 50. For this reason, as described above, the capture space 50 is provided with a bias coil 234 that corrects the gradient magnetic field.

20 and 21 show an example of a triaxial magnetic field correction coil 230 made of a square coil. However, it is also possible to use coils of other shapes, such as a circular coil instead of a square coil. Also, for example, the cylindrical triaxial magnetic field correction coil 96 shown in FIGS. 5 to 11 may be used.

The three-axis magnetic field correction coils can be provided both near the clock transition space 52 and near the inner wall of the main body 22. For example, a Helmholtz-type coil can be provided near the inner wall of the main body 22, and a non-Helmholtz-type coil can be provided near the clock transition space 52. By providing a non-Helmholtz-type coil near the clock transition space 52, it becomes easier to correct a magnetic field with a large curvature.

(4) Adjustment of the magnetic field correction coils The adjustment of the magnetic field using the three-axis magnetic field correction coils will now be described. The magnetic field is corrected by periodically observing the magnetic field distribution around the clock transition space 52, and manipulating the current in the three-axis magnetic field correction coils 96 to offset any non-uniform magnetic field distribution. The magnetic field distribution is observed by moving the atomic group trapped in the optical lattice using an optical moving optical lattice. These operations realize a situation in which each atom in the atomic group is always placed under the same zero magnetic field.

Figures 23A and 23B are schematic diagrams showing the adjustment process of the three-axis magnetic field correction coil. Figure 23A shows the state in which an atomic group 240 confined in a moving optical lattice is moved along the X-axis. Figure 23B also shows the relationship between the fluorescence transition and the clock transition.

As shown in FIG. 23A, the atomic group 240 is confined in a lattice connected in the X-axis direction with a certain degree of spatial expansion. In the figure, the representative positions on the X-coordinate to which the atomic group 240 moves are shown as positions X1, X2, X3, X4, and X5. These are positions set in the correction space 242 set for correcting the magnetic field. The correction space 242 is set in a wide range including the clock transition space 52 where the actual measurement is performed. In the embodiment, the optical lattice is a one-dimensional lattice extending in the X-axis direction, and since the atomic group 240 is distributed spreading in the X-axis direction, it is particularly aimed at uniformly zeroing out the magnetic field in the X-axis direction with high precision. Therefore, the correction space 242 is set with an expansion in the X-axis direction. Note that when the optical lattice is formed two-dimensionally, it is desirable to set a correction space in which the clock transition space 52 is expanded in the two-dimensional direction, and when the optical lattice is formed three-dimensionally, it is desirable to set a correction space in which the clock transition space 52 is expanded in the three-dimensional direction.

At each position in the moved correction space 242, the atomic group 240 is irradiated with a laser light that excites the clock transition, and the clock transition is excited. The frequency of the laser light is swept to measure the frequency of the clock transition at each position. The electron shelving method is used to observe the excitation rate of the clock transition. In the electron shelving method, after exciting the clock transition, the atoms are moved to the fluorescence observation space 243. As shown in FIG. 24B, by irradiating the light of the fluorescence transition, the atoms emit fluorescence 244 according to the excitation rate, and the fluorescence is observed by the photodetector 246. The clock transition is Zeeman split by the magnitude of the magnetic field at each position. Therefore, the magnetic field distribution at each position can be obtained from the information of the Zeeman splitting. The lower part of FIG. 23A shows the frequency distribution on the X-axis obtained in this way. This method makes it possible to measure the magnetic field even in places where fluorescence cannot be observed (such as inside a cryohead). In addition to the electron shelving method, non-destructive measurement methods using the measurement of the phase shift of atoms can also be applied to measure the excitation rate of the clock transition.

24 and 25 are flow charts for explaining the procedure for correcting the magnetic field using the three-axis magnetic field correction coil. First, calibration is performed according to the procedure shown in FIG. 24. In the calibration, the current of all coils constituting the three-axis magnetic field correction coil is stopped (set to 0 A), and the distribution of the magnetic field in the three-axis direction is measured (S10). For example, the magnetic field is measured in the three-axis direction using a magnetic sensor such as a small coil or a Hall element. The measured magnetic field represents the background value in the state where the three-axis magnetic field correction coil is not used. Next, the same amount of current (1 A in FIG. 24) is passed through all coils (n coils), and the magnetic field distribution in the three-axis direction is measured by a magnetic field sensor or the like (S12 to 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 1 A can be obtained.

In this calibration, the magnetic field in the correction space 242 may be measured. However, the correction space 242 is inside the low-temperature chamber 54, and it is not necessarily easy to install a magnetic sensor. Therefore, the magnetic field may be measured near the correction space 242 and estimated based on the results of the electromagnetic field simulation. The magnetic field may also be measured in the atmosphere rather than in a vacuum. This makes it possible to grasp the basic magnetic field distribution formed by each coil of the three-axis magnetic field correction coil with a current of 1 A. In principle, it is sufficient to perform this calibration once when the physics package 12 is created.

Next, the magnetic field is corrected according to the procedure shown in FIG. 25. First, as described above, the atomic ensemble 240 is moved by the moving optical lattice to measure the frequency of the clock transition at each position in the correction space 242 (S20). Then, the effect of Zeeman splitting is estimated to determine the magnetic field distribution in the correction space 242 (S22). This magnetic field distribution is obtained as the absolute value of the magnetic field.

Next, the current corresponding to the magnetic field corrected by each coil is determined using an optimization method such as the least squares method (S24). That is, a coefficient of superposition is obtained such that the magnetic field formed in the correction space 242 becomes uniformly zero when the basic magnetic fields formed by each coil are superposed. As described above, when both Helmholtz-type coils and non-Helmholtz-type coils are used, the optimal coefficient of superposition is first obtained by the least squares method or the like for the spatial higher-order differential terms generated by the non-Helmholtz-type coils. Next, the optimal superposition is obtained by the least squares method or the like for the constant terms and spatial first-order differential terms generated by the Helmholtz-type coils. This simplifies the calculation and also increases the accuracy of the calculation. The coefficient of superposition obtained is the direction and magnitude of the current flowing through each coil. The three-axis magnetic field can be corrected by passing the obtained current through the three-axis magnetic field correction coil (S26).

The correction shown in FIG. 25 does not necessarily have to be performed frequently under normal conditions where the magnetic field does not fluctuate much. For example, when repeatedly measuring clock transitions in clock transition space 52, it is sufficient to perform the correction shown in FIG. 25 every specified number of times. In addition, when measuring clock transitions in clock transition space 52, it is also possible to constantly check the magnitude of the Zeeman splitting, and perform the correction shown in FIG. 25 when it becomes a specified magnitude or greater.

When the magnetic field correction in the three-axis magnetic field correction coil is performed within the range of the correction space 242, it is expected that the magnetic field in the clock transition space 52 can be uniformly zeroed out more stably than when it is performed within the range of the clock transition space 52. This is thought to be because, for example, when only a narrow space such as the clock transition space 52 is targeted, it is affected by various fine-scale disturbances such as slight fluctuations in the magnetic field, errors in magnetic field measurement, and errors in the basic magnetic field of each coil. In fact, experimental results have shown that accuracy is improved by performing corrections within the correction space 242.

In the examples shown in Figures 23A and 25, a moving optical lattice is used to move the atomic group 240 to various locations in the correction space 242. In contrast, Figure 26 is a schematic diagram showing an example in which the magnetic field distribution in the correction space 242 is measured in one go.

In FIG. 26, an atomic group 250 is confined in an optical lattice throughout the entire correction space 242. Fluorescence light 252a, 252b, 252c, 252d, and 252e from the atomic group 250 is received all at once by a CCD camera 254 while retaining spatial position information, and the frequency is determined. This allows the magnetic field distribution in the correction space 242 to be immediately determined.

(5) Individual magnetic field compensation coils As explained in (1) above, for the Peltier element (refrigerator 58) which is a large current device, an individual magnetic field compensation coil 102 for the refrigerator is provided to compensate for the magnetic field in the clock transition space 52. For the heater of the atomic oven 40, an individual magnetic field compensation coil 104 for the atomic oven is provided to compensate for the magnetic field in the clock transition space 52. When compensating for all the large leakage magnetic fields from the large current devices with the three-axis magnetic field compensation coils, it is necessary to make the three-axis magnetic field compensation coils higher order and increase the current. Therefore, it is effective to provide individual magnetic field compensation coils to compensate for the magnetic field. Here, a detailed explanation will be given using the individual magnetic field compensation coil 102 for the refrigerator as an example.

Figure 27 is a schematic diagram showing an example of the configuration of the cryostat 54, heat link member 56, refrigerator 58, and refrigerator individual magnetic field compensation coil 102. The cryostat 54 is a hollow part that surrounds the clock transition space 52. Although not shown, an opening is provided along the X-axis in the wall of the cryostat 54 for passing optical lattice light inside. The cryostat 54 is made of oxygen-free copper, which has high thermal conductivity.

A thermal link member 56 is attached to the low-temperature chamber 54. The thermal link member 56 is a member that serves both as a support structure for supporting the low-temperature chamber 54 and as a path for removing heat from the low-temperature chamber 54. The thermal link member 56 is also made of oxygen-free copper, which has high thermal conductivity.

The refrigerator 58 comprises a Peltier element 58a, a heat sink 58b, a heat insulating member 58c, and Permalloy magnetic field shields 58d and 58e. The Peltier element 58a is connected to the thermal link member 56, and absorbs heat from the thermal link member 56 when a current is passed through it. The heat sink 58b is a member made of oxygen-free copper or the like, which has high thermal conductivity. The heat sink 58b is provided on the outer wall of the vacuum chamber 20, and dissipates the heat transferred from the Peltier element 58a to the outside of the vacuum chamber 20.

The heat insulating member 58c ensures heat insulation between the permalloy magnetic field shield 58d and the heat link member 56. The heat insulating member 58c is made of a material such as silica that has low thermal conductivity, and is formed into a spherical shape to reduce the number of contact points between the permalloy magnetic field shield 58d and the heat link member 56. The permalloy magnetic field shield 58e is a magnetic field shield, and is made of permalloy, which has high thermal conductivity and high magnetic permeability. The permalloy magnetic field shield 58e is provided between the Peltier element 58a and the heat sink 58b, and conducts heat from the Peltier element 58a to the heat sink 58b.

The low-temperature chamber 54 is provided with a temperature sensor 260 using a thermocouple, thermistor, or the like, and the measured temperature T1 is input to the control device 262. In addition, a temperature sensor 264 is provided on the heat sink 58b or its periphery, and the measured temperature T2 is input to the control device 262.

The control device 262 controls the current so that the temperature T1 of the low-temperature chamber 54 is always kept at a constant low temperature (e.g., 190 K). The control is performed, for example, by PID (Proportional Integral Differential) control that also takes into account the temperature T2 on the heat sink 58b side. The determined current is passed through the current path 266 to the Peltier element 58a.

The Peltier element 58a is a thermoelectric element that transfers heat in response to the current that flows through it. When a current flows through it, the Peltier element 58a absorbs heat from the low-temperature side heat link member 56 (and the low-temperature bath 54 connected to the heat link member 56) and releases the heat to the high-temperature side permalloy magnetic field shield 58e (and the heat sink 58b connected to the permalloy magnetic field shield 58e).

A large current, for example of several amperes, flows through the Peltier element 58a. This causes a large magnetic field to be generated. The Peltier element 58a is mostly covered by Permalloy magnetic field shield 58d and Permalloy magnetic field shield 58e, which are made of high magnetic permeability material. Therefore, most of the generated magnetic field flows inside these components and does not leak out to the outside. However, from the perspective of thermal conduction efficiency, a magnetic field shield cannot be provided between the thermal link member 56 and the Peltier element 58a. This causes a leakage magnetic field 270. The leakage magnetic field 270 disrupts the magnetic field in the clock transition space 52 inside the cryostat 54.

Therefore, in the embodiment, a refrigerator individual magnetic field compensation coil 102 is provided around the heat link member 56, which is an opening portion where magnetic field shielding is not possible. The refrigerator individual magnetic field compensation coil 102 generates a compensation magnetic field 272 when a current is passed through it.

Current flows through the refrigerator individual magnetic field compensation coil 102 via a current path 268 branching off from the current path 266. That is, the Peltier element 58a and the refrigerator individual magnetic field compensation coil 102 are connected in parallel to the same current path. The electrical resistance of the Peltier element 58a and the electrical resistance of the refrigerator individual magnetic field compensation coil 102 vary slightly with temperature, but both can be considered to be approximately constant values in the temperature environment in which the measurements are performed. Therefore, the current flowing from the control device 262 to the current path 266 is distributed at a constant rate to the Peltier element 58a and the refrigerator individual magnetic field compensation coil 102.

When the current flowing through the Peltier element 58a increases, the current flowing through the refrigerator-use individual magnetic field compensation coil 102 also increases in proportion to the increase in the current. Therefore, when the leakage magnetic field 270 from the Peltier element 58a increases, the compensation magnetic field 272 generated by the refrigerator-use individual magnetic field compensation coil 102 also increases by the same amount. The refrigerator-use individual magnetic field compensation coil 102 is formed so that when a current of a certain magnitude flows through the current path 266, it compensates for the leakage magnetic field 270 in the clock transition space 52 inside the cryostat 54 (generating a magnetic field of the same magnitude in the opposite direction). Therefore, even if the current changes, the magnetic field can be compensated. Note that current also flows through the current paths 266 and 268, but since the currents flowing back and forth in the current paths 266 and 268 flow close to each other, the magnetic field generated is small and does not pose a problem.

The arrangement of the current paths 266, 268 can be said to be a compensation current control means that dynamically changes the current flowing through the refrigerator individual magnetic field compensation coil 102 in response to the leakage magnetic field 270. The compensation current control means can also be constructed in other forms, such as a mode in which the control device 262 flows the necessary current calculated by calculation through the refrigerator individual magnetic field compensation coil 102.

In the example shown in FIG. 27, the refrigerator individual magnetic field compensation coil 102 is formed by a single coil wound around the thermal link member 56. In this configuration, the refrigerator individual magnetic field compensation coil 102 is provided near the wall of the vacuum chamber 20, which prevents the configuration near the low-temperature bath 54 from becoming complicated. However, the installation location of the refrigerator individual magnetic field compensation coil 102 is not particularly limited, and it is also possible to install it near the low-temperature bath 54, for example. When the refrigerator individual magnetic field compensation coil 102 is installed near the low-temperature bath 54, it is possible to reduce the size and power consumption of the refrigerator individual magnetic field compensation coil 102.

The individual magnetic field compensation coil 102 for the refrigerator may be formed by multiple coils rather than a single coil. If the distribution of the leakage magnetic field in the clock transition space 52 is complex, it may be possible to compensate relatively easily by using multiple coils.

The current device, the individual magnetic field compensation coil, and the compensation current control means constitute a magnetic field compensation module. The magnetic field compensation module enables precise magnetic field compensation and can be applied to various devices including the optical lattice clock 10.

(6) Zeeman reducer Fig. 28 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 arranged coaxially with the beam axis. The hollow part near the center of the bobbin is a space through which the atomic beam 42 flows along the beam axis.

From a functional point of view, most of the coil 282 is a decreasing type Zeeman coil section 284 in which the number of turns gradually decreases from the upstream side to the downstream side of the beam axis. The most downstream part of the coil 282 in the beam axis direction is an MOT coil section 286 with a large number of turns. The coated conductors of the Zeeman coil section 284 and the MOT coil section 286 are continuous, and the magnetic field generated by the Zeeman coil section 284 spreads to the vicinity of the MOT coil section 286, and the magnetic field generated by the MOT coil section 286 spreads to the downstream side of the Zeeman coil section 284. Therefore, please note that the boundary between the Zeeman coil section 284 and the MOT coil section 286 cannot be clearly defined.

A disk-shaped upstream flange 288 with a radius larger than the maximum radius of the Zeeman coil section 284 is provided on the upstream side of the beam axis of the bobbin 280. The upstream flange 288 is attached to the cylindrical wall 32 of the protrusion 30 of the vacuum chamber 20. A mirror support (not shown) is attached to the front of the upstream flange 288. An optical mirror 76 is attached to the tip of the mirror support.

On the downstream side of the beam axis of the bobbin 280, two circular downstream flanges 290, 292 are provided, each having a radius similar to that of the MOT coil section 286. The downstream flange 290 is formed in a relatively thick circular shape in the beam axis direction and is provided near the boundary between the Zeeman coil section 284 and the MOT coil section 286. The downstream flange 292 is formed in a relatively thin circular shape in the beam axis direction and is provided downstream of the MOT coil section 286. The downstream flanges 290, 292 are attached at their upper parts to an upper support member 312 and at their lower parts to a lower support member 314. The upper support member 312 and the lower support member 314 are each attached to the rear circular wall 28 of the main body section 22 of the vacuum chamber 20.

The MOT device coil 48 is disposed downstream of the Zeeman reducer coil 44 at a predetermined distance. The MOT device coil 48 is formed by winding an MOT coil 302 around a short cylindrical bobbin 300 that is coaxial with the beam axis. A thin ring-shaped flange 304 having a radius similar to that of the MOT coil 302 is provided on the upstream side of the bobbin 300 in the beam axis direction. A relatively thick ring-shaped flange 306 having a radius similar to that of the MOT coil 302 is provided on the downstream side of the bobbin 300 in the beam axis direction. The upper parts of the flanges 304 and 306 are attached and fixed to an upper support member 312.

The Zeeman reducer coil 44 is made of a bobbin 280, an upstream flange 288, and downstream flanges 290, 292, which have high thermal conductivity and low magnetic permeability, such as copper. The bobbin 280, the upstream flange 288, and the downstream flanges 290, 292 are joined by welding with high strength and close contact.

In the Zeeman decelerator coil 44, many coils are wound on the upstream side of the beam axis, and the weight of the upstream side is heavier than that of the downstream side. Therefore, by connecting the upstream flange 288 to the cylindrical wall 32 of the protrusion 30 of the vacuum chamber 20, the Zeeman decelerator coil 44 is stably positioned inside the vacuum chamber 20.

In addition, the Zeeman reducer coil 44 generates heat due to the current flowing through the coil 282. Since the vacuum chamber 20 is a vacuum, unlike the atmosphere, heat conduction through gas does not occur. For this reason, in the Zeeman reducer coil 44, although some cooling action occurs due to blackbody radiation, the heat of the coil 282 must be mainly removed by heat conduction through a solid. The bobbin 280 is in contact with the coil 282, and heat is effectively conducted from the coil 282. In addition, the upstream flange 288 and the downstream flanges 290 and 292 also have a large contact area with the coil 282, and remove heat from the coil 282. As shown in FIG. 2, 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 through a water-cooled tube made of copper or the like. This prevents the Zeeman reducer coil 44 from becoming excessively hot.

The bobbin 300 and flanges 304, 306 of the MOT device coil 48 are also made of copper, which has high thermal conductivity and low magnetic permeability. The bobbin 300 and flanges 304, 306 are also joined by welding with high strength and close contact. The MOT coil 302 of the MOT device coil 48 is smaller and lighter than the coil 282 of the Zeeman reducer coil 44, and the entire MOT device coil 48 is also lighter. For this reason, the MOT device coil 48 is stably attached to the rear circular wall 28 via the upper support member 312 to which the flanges 304, 306 are fixed.

In addition, the MOT coil 302 of the MOT device coil 48 has a smaller current flowing therethrough and generates less heat than the coil 282 of the Zeeman reducer coil 44. In addition, in the MOT device coil 48, the MOT coil 302 is surrounded on three sides by the bobbin 300 and flanges 304 and 306. 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 assumed that the MOT device cooler 94 will be water-cooled. However, if the amount of heat to be removed is small, it may be air-cooled.

In the example of FIG. 28, the number of turns of the coil 282 is roughly decreased in a monotonous manner, but in detail, unevenness is formed in the beam axis direction. One of the reasons for providing unevenness is to obtain a desired magnetic field strength at a specific position on the beam axis. For example, in the capture space 50 where atoms are captured, the magnetic field needs to be zero. Another reason is that, from the viewpoint of power saving, a configuration is used in which a magnetic field is not generated at a position where a magnetic field is not required. In the Zeeman decelerator coil 44, it is sufficient to generate a magnetic field necessary to decelerate atoms or to restrain atoms. Another reason for providing unevenness is the requirement for mechanical support or thermal heat dissipation. As the number of turns increases, the weight of the coil increases, making support difficult. In addition, the amount of heat dissipated from the coil increases. For this reason, it is possible to increase the number of turns of the coil in a portion that is favorable for support or a portion where heat dissipation efficiency is high. In the example shown in FIG. 28, the coil 282 of the Zeeman reducer coil 44 is formed in a relatively convex shape with a large number of turns at the portion in contact with the upstream flange 288, and is formed in a relatively concave shape with a relatively small number of turns downstream. As a result, the center of gravity of the Zeeman reducer coil 44 moves toward the upstream flange 288, stabilizing the fixation by the upstream flange 288. In addition, the contact area between the coil 282 and the upstream flange 288 is also increased, allowing efficient heat conduction from the coil 282 to the upstream flange 288.

Now, referring to FIG. 29, we will explain the voids in the coil. FIG. 29 is a cross-sectional view of the upper part of the two Zeeman coils 320, 330. The number of coil turns in the Zeeman coil 320, including the portion 322, decreases monotonically in the beam axis direction. On the other hand, the number of turns in the Zeeman coil 330 is locally small in the portion 332 called a void. However, in the Zeeman coil 330, the number of turns is locally large before and after the portion 332 in the beam axis direction. Therefore, the distribution of the magnetic field created by the entire Zeeman coil 330 is substantially equal to the distribution of the magnetic field created by the Zeeman coil 320.

It is possible to theoretically determine how to form the void and the coil shape around it. The magnetic field distribution generated by the unit current component follows the Biot-Savart law. The conversion from the magnetic field distribution to the current distribution can be handled by the deconvolution method or more broadly as an inverse problem. A method for finding a solution to the minimum current path by an inverse problem is described, for example, in Mansfield P, Grannell PK, "NMR diffraction in solids," J Phys C: Solid State Phys 6:L422-L427, 1973. However, if one does not care about the minimum current, it is self-evident that there are several overlapping solutions. In FIG. 29, assuming that the solution of the minimum current path that satisfies the desired magnetic field distribution is the Zeeman coil 320, the Zeeman coil 330 with the increased current density around the void can also form the desired magnetic field distribution.

In the coil 282 shown in FIG. 28, a downstream flange 290 is provided midway through the coil 282. This corresponds to the downstream flange 290 being provided at the position of a large void. And, by setting the number of turns before and after the downstream flange 290 in the beam direction to be greater than when the downstream flange 290 is not provided, the effect of the downstream flange 290 is eliminated or reduced.

Figure 30 shows the magnetic field distribution in the Zeeman decelerator coil 44 and the MOT device coil 48. The horizontal axis represents the position on the beam axis, and the origin corresponds to the capture space 50. The vertical axis represents the magnitude of the magnetic field on the beam axis. Since the Zeeman decelerator 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 position on the beam axis where the coil 282 of the Zeeman decelerator coil 44 is located and the position where the MOT coil 302 of the MOT device coil 48 is located are also shown. The points in the graph represent the magnetic field values calculated, and the thin lines in the graph represent the ideal magnetic field values for decelerating atoms toward the capture space 50 by Zeeman deceleration.

The magnetic field is at its maximum slightly downstream of the upstream end of coil 282. The magnetic field value decreases sharply slightly upstream of the maximum value, and gradually approaches zero further upstream. An ideal magnetic field is one in which the magnetic field is zero outside coil 282 and does not leak out. However, because the magnetic field generated by the current has a spatial spread, for example, unless a coil in the opposite direction is provided to compensate for (cancel) the external magnetic field, it is not possible to make the magnetic field outside coil 282 completely zero.

Downstream from the position where the magnetic field is at its maximum value, the magnetic field decreases monotonically. As mentioned above, the number of turns in the coil is slightly uneven, but due to the influence of the surrounding coils, a monotonically decreasing magnetic field that is ideal for Zeeman deceleration is created. This magnetic field with a gradient is almost identical to the ideal magnetic field distribution for Zeeman deceleration, indicating that atoms can be steadily decelerated toward the capture space 50.

The magnetic field decreases rapidly just before the downstream end of coil 282. The MOT coil section 286 in this vicinity has a large number of turns, but since there are no coils further downstream, the value of the magnetic field decreases rapidly.

The magnetic field decreases with a nearly constant gradient and becomes zero in the capture space 50. Furthermore, the magnetic field decreases with the same gradient and becomes a minimum value (maximum negative value) near the MOT coil 302 of the coil 48 for the MOT device. This is because the MOT coil 302 passes a current in the opposite direction to the coil 282. Approximately, a Helmholtz-type coil is formed from near the MOT coil part 286 of the coil 282 to near the MOT coil 302. Therefore, by passing a current in the opposite direction to the MOT coil 302, a magnetic field with a constant gradient can be formed. Although not shown, a magnetic field with a constant gradient is also formed in the direction perpendicular to the beam axis. In this gradient magnetic field formed by the MOT device, MOT light beams are irradiated from each of the three axes. This makes it possible to capture atoms in the capture space 50, which is the origin. Downstream of the MOT coil 302, the magnetic field gradually approaches zero.

In this way, by combining and installing the Zeeman reducer coil 44 and the MOT device coil 48, it is possible to shorten the length in the beam axis direction compared to when the Zeeman reducer and the MOT device are installed separately. In addition, the overall coil length can be shortened, which allows for power saving and reduced heat generation.

When a background magnetic field is present, the position where the magnetic field becomes zero shifts from the capture space 50. Therefore, during the process of trapping atoms, the three-axis magnetic field correction coil 96 or the bias coil that corrects the gradient magnetic field can be adjusted to generate a compensation magnetic field that cancels out the background magnetic field near the capture space 50.

Next, referring to Figures 31A and 32B, an example of an increasing type Zeeman reducer coil 340 is shown. Figure 31A is a cross-sectional view showing the state before the Zeeman reducer coil 340 is attached inside the vacuum chamber 20, and Figure 31B is a cross-sectional view showing the state after attachment. The coil 342 of the Zeeman reducer coil 340 shown in Figure 31A is a Zeeman coil section 344 that has the function of a Zeeman coil in most part of the upstream side of the beam axis. In addition, the most downstream side of the coil 342 is an MOT coil section 346 that combines the function of a Zeeman coil and the function of an MOT coil. In the Zeeman coil section 344, the number of turns of the coil increases monotonically from the upstream end to the downstream side. Then, near the downstream end, after repeated unevenness, the number of turns becomes maximum at the most downstream side. For convenience, the section with the maximum number of turns is called the MOT coil section 346, but as mentioned above, it also functions as a Zeeman coil.

The Zeeman reducer coil 340 has a bobbin on the inside. It also has a flange 350 at the upstream end, a flange 352 midway along the coil 342 near the downstream end, and a flange 354 at the downstream end. The flanges 350, 352, and 354 are welded to the bobbin.

A mirror support (not shown) is attached to the upstream flange 350, and an optical mirror 76 is fixed to the mirror support.

The downstream flanges 352, 354 are connected to each other at parts other than the bobbin to increase their strength. The flange 352 is a thin disk with a large radius. The flange 352 is attached to a ring-shaped annular support part 370. The ring of the annular support part 370 is equipped with a water-cooled pipe 372 through which cooling water flows, and cools the coil 342 through the flange 352. Two beams 374 are attached to the upper part of the annular support part 370, one on the left and one on the right, and two beams 376, which also serve as water-cooled pipes, are attached to the lower part. The beams 374, 376 are attached to the rear circular wall 28 in the main body part 22 of the vacuum chamber 20, and support the entire structure including the Zeeman reducer coil 340. The beams 374, 376 also serve as a heat exhaust path that transfers heat from the coil 342 to the rear circular wall 28. In addition, the cooling water flowing through the beam 376 can also be circulated to the heat sink 58b in the refrigerator 58.

In this configuration, it is assumed that the MOT device coil 380 is attached to the rear circular wall 28 by a separately provided support member. It is also assumed that the Zeeman reducer coil 340 is positioned relative to the MOT device coil 380 by a positioning mechanism.

Figure 32 corresponds to Figure 30 and shows the magnetic distribution when an increasing type Zeeman reducer coil 340 and an MOT device coil 380 are used. The magnetic field gradually increases from downstream of the coil 342 of the Zeeman reducer coil 340, and reaches a maximum value near the MOT coil section 346. This increase in magnetic field matches well with the target curve required to realize Zeeman deceleration. Downstream of the position where the maximum value is reached, the magnetic field rapidly decreases. Then, before and after the capture space 50, which is the origin, it decreases from positive to negative with an almost constant slope, and becomes zero at the capture space 50. The magnetic field reaches a minimum near the MOT device coil 380, and then gradually approaches zero.

In the parts of the MOT device before and after the capture space 50, the gradient of the magnetic field is steeper than in the decreasing type of FIG. 30. This is because the number of turns of the MOT coil section 346 in the coil 342 is large, and the number of turns of the coil for the MOT device 380 facing it is also large. By making the gradient of the magnetic field steeper, atoms can be captured over a short distance in the beam axis direction.

The increasing type Zeeman decelerator coil 340 shown in FIG. 32 can reduce the length in the beam axis direction compared to the decreasing type Zeeman decelerator coil 44 in FIG. 30. This is because the increasing type can decelerate atoms efficiently. The increasing type has the advantage of being able to reduce power consumption because the magnetic field required to decelerate atoms can be suppressed compared to the decreasing type.

On the other hand, in the increasing type Zeeman reducer coil 340, the side facing the capture space 50 is heavier, making it difficult to support it inside the vacuum chamber 20. Also, in the increasing type, the number of coil turns on the side facing the capture space 50 is greater, which creates an issue of increased heat generation near the center of the vacuum chamber 20 and makes cooling more difficult. However, as described above, the Zeeman reducer coil 340 is supported near the center of the vacuum chamber 20 by the annular support part 370 with cooling function, so these problems do not arise.

The mounting manner of the coil 340 for the increasing type Zeeman reducer shown in Figures 31A and 31B is merely one example, and other configurations are also possible. A modified example will be described with reference to Figures 33A and 33B.

Figure 33A is a perspective view showing the state before the Zeeman reducer coil 390 is attached inside the vacuum chamber 20, and Figure 33B is a perspective view showing the state after attachment. The coil 392 of the Zeeman reducer coil 390 is wound in the same manner as the Zeeman reducer coil 340, and the configuration including the bobbin and multiple flanges 394, 396, 398 is also almost the same. However, in the Zeeman reducer coil 390, the flange 396 provided near the lower end in the beam direction has a semicircular shape of about the lower half. The part that supports the flange 396 is also a semicircular ring support part 400 that is approximately U-shaped, half a ring. The semicircular ring support part 400 is provided with a water cooling tube 402.

In the embodiment shown in Fig. 33A and Fig. 33B, the flange 396 is semicircular, so that the cooling performance is slightly reduced when the circulation of the cooling water is the same. On the other hand, in the coil 390 for the Zeeman decelerator, since there is a space above the flange 396, it is easy to access the atomic oven 40 side from the optical resonator 46 side inside the vacuum chamber 20. In addition, since there is a space above the semicircular ring support part 400, it is easy to remove the optical resonator 46. Furthermore, since the vertical distance of the water cooling tube is shortened, it is easy to prevent the flow disturbance caused by convection in the water cooling tube. In addition, the flange 396 shown in Fig. 33A and Fig. 33B can be provided with holes as appropriate in the surface. When holes are provided, the efficiency of heat conduction is reduced, but it is possible to reduce the weight. Similarly, holes can be provided in the surface of the flange 352 shown in Fig. 31A and Fig. 31B.

Figure 34 is a cross-sectional view of an increasing type Zeeman reducer coil 410 according to another embodiment. The Zeeman reducer coil 410 uses a bobbin 412 with a thickness that varies in the beam direction. The cylindrical bobbin 412 has a constant inner diameter, but the outer diameter gradually decreases in a stepped manner from the upstream to the downstream in the beam direction. The coil 414 wound around the bobbin 412 is wound more on the downstream side in the beam axis direction. Therefore, the outer diameter of the coil 414 is almost constant in the beam axis direction.

In the configuration shown in FIG. 34, the contact area between the bobbin 412 and the coil 414 is increased by increasing the outer diameter of the bobbin 412, improving the efficiency of heat conduction from the coil 414 to the bobbin 412. In addition, the step of the bobbin 412 can be used to wind the coated conductor wire, making it easier to install the coil 414.

Although not limited to this embodiment, the efficiency of thermal conduction with the bobbin 412 and the like is further improved by using a rectangular wire with a square cross section for the coated conductor that constitutes the coil 414, rather than a round wire with a round cross section. Also, as shown below, when the coil 414 is covered with a thermally conductive cover, since the outer diameter of the coil 414 is constant, the cover can be brought into close contact with the coil 414, making it easy to remove heat through the cover.

So far, we have described an example in which the Zeeman reducer is installed inside the vacuum chamber 20. By providing a cooling mechanism that removes Joule heat generated by the coil, the Zeeman reducer can be installed in the vacuum chamber 20 in a thermally stable manner. Below, we will describe another example in which part or all of the coil is sealed with a cover (i.e., encapsulated).

Figures 35A and 35B are side cross-sectional views showing the Zeeman reducer coil 420 and the cover 440. Figure 35A shows the state before the cover 440 is attached to the Zeeman reducer coil 420, and Figure 35B shows the state after attachment. The Zeeman reducer coil 420 is a decreasing type in which the number of coil turns gradually decreases in the direction of the beam axis.

The bobbin 422 of the Zeeman reducer coil 420 is provided with a flange 424 at the upstream end of the beam axis, and a flange 426 at the downstream end. As in the above example, the bobbin 422 and the flanges 424 and 426 are made of copper or the like to ensure high thermal conductivity. The flanges 424 and 426 are provided with sealing members 428 and 430 made of indium on their outer peripheries. The sealing members 428 and 430 are formed in a relatively thin annular (also called ring-shaped) sheet shape, or in a relatively thick annular shape. Indium has the characteristic of enabling stable vacuum sealing even in the presence of large temperature changes. The flange 426 is also provided with a hermetic connector 432, which is a vacuum-resistant connector.

A coil 434 is wound around the bobbin 422 between the flanges 424 and 426, and a coil 436 is wound around the downstream side of the flange 426. Both coils 434 and 436 are formed from coated conductor wires insulated with copper resin. The coils 434 and 436 are electrically connected via a hermetic connector 432.

The cover 440 is formed in a cylindrical shape. The cover 440 is made of the same copper as the bobbin 422, the flanges 424, 426, and the coils 434, 436, and is prevented from deformation due to thermal expansion.

Cover 440 is installed so as to cover the area from flange 424 to flange 426. That is, part of the inner circumference of the upstream end of cover 440 surrounds part of the outer circumference of flange 424 and is sealed with seal member 428. Also, part of the inner circumference of the downstream end of cover 440 surrounds part of the outer circumference of flange 426 and is sealed with seal member 430. Cover 440 is made to have a positive tolerance for the length from flange 424 to flange 426, so that it can reliably surround both.

The air pressure inside the cover 440 can be freely set as long as the sealing members 428, 430 can reliably seal. For example, air at atmospheric pressure may be sealed inside, or a rough vacuum may be used. A rough vacuum is a rarefied state using a turbo pump or the like, and is set to, for example, about 1 Pa to 0.1 Pa. When a rough vacuum is used inside the cover 440, the pressure difference between the inside and outside of the cover 440 becomes small when the vacuum chamber 20 is evacuated, so that the sealing surfaces of the sealing members 428, 430 can be strongly prevented from being pulled apart.

It is also possible to fill the inside of the cover 440 with an inert gas such as nitrogen or helium. The inert gas is selected to be one that is less reactive with the resin used in the coil 434 when the coil becomes hot. The pressure of the inert gas is not particularly limited, and may be, for example, 1 atmosphere, or a rough vacuum state. The inside of the cover 440 may also be filled with a lightweight resin such as urethane foam. In this case, it is possible to increase the strength of the cover 440.

When current is applied, the Zeeman reducer coil 420 heats up due to Joule heat. More Joule heat is generated in the coil 434, which has a larger number of turns, than in the coil 436, which has a smaller number of turns. For this reason, the coil 434 tends to heat up. When the temperature rises, a small amount of gas contained in the resin of the coated conductor that constitutes the coil 434 is released from the resin (this gas is called outgassing). However, in the Zeeman reducer coil 420, the coil 434 is sealed by the bobbin 422, flanges 424, 426, and cover 440, and the outgas does not leak into the vacuum chamber 20. For this reason, the occurrence of errors in clock transition due to outgassing is prevented. Therefore, the Zeeman reducer coil 420 sealed by the cover 440 functions as a vacuum installation coil that is highly convenient when installed in a vacuum.

The cover 440 also serves as a heat conducting medium between the flange 424 and the flange 426. In other words, heat is conducted between the flange 424 and the flange 426 not only through the bobbin 422 but also through the cover 440, which also has the effect of promoting cooling of the coils 434 and 436.

In the above description, it is assumed that the cover 440 covers the outer periphery of the flanges 424, 426 and does not contact the coil 434. However, the cover 440 may be in contact with a part or all of the outer surface of the coil 434. In this case, the heat from the coil 434 is directly thermally conducted to the cover 440, improving the heat dissipation efficiency. In particular, when the outer diameter of the coil 414 is constant, as in the coil 414 shown in FIG. 34, it is easy to make the cover 440 adhere closely to the inner circumference of the cover 440. In addition, when it is difficult to form a shape that brings the cover 440 into contact with the outer surface of the coil 434, a thermally conductive member may be inserted between the cover 440 and the coil 434.

In the embodiment shown in Figures 35A and 35B, the cover 440 does not cover the coil 434. This is because the number of turns of the coil 434 is small, and there is little need to take measures against the release of outgassing. In addition, the coil 434 is a part that includes the MOT coil portion that constitutes the MOT device, and since the optical resonator 46 and the like are arranged nearby, the coil 434 is covered to avoid increasing its diameter. However, if interference with surrounding devices and parts can be avoided, the entire device including the coil 434 may be encapsulated by covering it.

In the examples of Figures 35A and 35B, a coil 420 for a decreasing type Zeeman reducer is used as an example. However, even in the case of an increasing type, it is possible to encapsulate a part or the whole, including the part with a large number of turns.

In the above description, the cover 440 is attached to the flanges 424, 426 using indium sealing members 428, 430 to make the inside airtight. However, sealing members made of other materials may be used instead of indium. When sealing members are used, for example, it is possible to attach and detach the cover 440 to the flanges 424, 426 using fixing screws. However, for example, the cover 440 and the flanges 424, 426 may be attached to each other using a semi-permanent sealing method such as welding or vacuum brazing to make the inside airtight.

In the above explanation, an optical lattice clock is taken as an example. However, the techniques of this embodiment can be applied to devices other than optical lattice clocks by those skilled in the art. Specifically, they can be applied to atomic clocks other than optical lattice clocks, or atomic interferometers, which are interferometers using atoms. Furthermore, this embodiment can be applied to various quantum information processing devices for atoms (including ionized atoms). Here, a quantum information processing device refers to a device that performs measurement, sensing, and information processing using the quantum state of atoms and light, and examples of such devices include magnetic field meters, electric field meters, quantum computers, quantum simulators, and quantum repeaters in addition to atomic clocks and atomic interferometers. In the physics package of a quantum information processing device, by using the technology of this embodiment, it is possible to achieve miniaturization or portability, similar to the physics package of an optical lattice clock. Note that in such devices, the clock transition space may be treated simply as a space in which clock transition spectroscopy occurs, rather than a space intended for clock measurement.

In these devices, for example, by providing the three-axis magnetic field correction coil according to this embodiment, it may be possible to improve the accuracy of the device. Furthermore, by providing the three axes according to this embodiment inside a vacuum chamber, it may be possible to realize a physics package that is smaller, more portable, or more accurate. Furthermore, by introducing a magnetic field compensation module, it becomes possible to control the magnetic field distribution with high accuracy. Furthermore, in a physics package that uses a vacuum chamber, it is effective to provide a vacuum installation coil.

In the above explanation, specific embodiments have been shown to facilitate understanding. However, these are merely examples of embodiments, and various other embodiments are possible.

10 Optical lattice clock, 12 Physics package, 14 Optical system, 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 oven, 42 Atomic beam, 44 Coil for Zeeman reducer, 44a Flange, 46 Optical resonator, 48 Coil for MOT device, 48a Flange, 50 Trapping space, 52 Clock transition space, 54 Cryostat, 56 Heat link member, 58 Refrigerator, 58a Peltier element, 58b Heat sink, 58c Heat insulating member, 58d, 58e Permalloy magnetic field shield, 60 Vacuum pump body, 62 Vacuum pump cartridge, 64, 66 Vacuum-resistant optical window for optical lattice light, 68 Vacuum-resistant optical window for MOT light, 70, 72 Vacuum-resistant optical window for MOT light, 74, 76 Optical mirror, 80 Optical lattice light beam, 82 Zeeman deceleration light beam, 84, 86a, 86b MOT light beam, 90 Cooler for atomic oven, 92 Cooler for Zeeman deceleration, 94 Cooler for MOT device, 96 Three-axis magnetic field correction coil, 98 Vacuum-resistant electrical connector, 102 Individual magnetic field compensation coil for refrigerator, 104 Individual magnetic field compensation coil for atomic oven, 120 First coil group, 122, 124 Coil, 130 Second coil group, 132, 134 Coil, 136, 138 Arrow, 140 First coil group, 142 Composite coil, 143, 144 Coil, 145 Composite coil, 146, 147 Coil, 150 Second coil group, 152, 154 Coil, 160 First coil group, 162 Composite coil, 163, 164 Coil, 165 Composite coil, 166, 167 Coil, 170 Second coil group, 172, 174 Coil, 180 Holder, 182, 184, 186 Frame, 190 Correction coil, 192 Current path, 194 Insulation, 196 Wiring path, 198 Terminal connector, 199 Boundary, 200, 202, 203, 204, 206, 208 Current path, 210 Correction coil, 212, 214 Current path, 218 Physics package, 220 Vacuum chamber, 222 Main body, 224, 230 Three-axis magnetic field correction coil, 240 Atomic group, 242 Correction space, 243 Fluorescence observation space, 244 Fluorescence, 246 Photodetector, 250 Atomic group, 252a, 252b, 252c, 252d, 252e Fluorescence, 254 CCD 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 Bobbin, 282 Coil, 284 Zeeman coil section, 286 MOT coil section, 288 Upstream flange, 290, 292 Downstream flange, 300 Bobbin, 302 MOT coil, 304, 306 Flange, 312 Upper support member, 314 Lower support member, 320 Zeeman coil, 322 Part, 330 Zeeman coil, 332 Part, 340 Zeeman reducer coil, 342 Coil, 344 Zeeman coil section, 346 MOT coil section, 350, 352, 354 flange, 370 annular support section, 372 water-cooled tube, 374, 376 beam, 380 MOT device coil, 390 Zeeman reducer coil, 392 coil, 394, 396, 398 flange, 400 semi-annular support section, 402 water-cooled tube, 410 Zeeman reducer coil, 412 bobbin, 414 coil, 420 Zeeman reducer coil, 422 bobbin, 424, 426 flange, 428, 430 seal member, 432 hermetic connector, 434, 436 coil, 440 cover.

Claims (18)

a coil disposed in the vacuum chamber and wound around a beam axis along which the atomic beam flows to form a spatially gradient magnetic field;
A sealing member that airtightly surrounds a part or all of the coil;
A coil for vacuum installation comprising: 2. The vacuum installation coil according to claim 1,
13. A vacuum installation coil, comprising: a sealing member formed of metal. 2. The vacuum installation coil according to claim 1,
The sealing member is
a cylindrical bobbin provided on an inner circumferential side of the coil and around which the coil is wound;
The outer surface of the bobbin tube is expanded to form two flanges surrounding the side surfaces of the coil in the direction of the beam axis;
a cover that surrounds an outer circumferential side of the coil between the two flanges;
A coil for vacuum installation, comprising: 4. The vacuum installation coil according to claim 3,
A vacuum installation coil, characterized in that the cover surrounds at least a portion of the outer periphery of the two flanges. 4. The vacuum installation coil according to claim 3,
A coil for vacuum installation, characterized in that the cover is in direct contact with part or all of the outer periphery of the coil, or indirectly in contact with it via a thermally conductive member inserted into the space surrounded by the sealing member. 2. The vacuum installation coil according to claim 1,
The coil has a different number of turns in the direction of the beam axis,
A coil for vacuum installation, characterized in that the area surrounded by the sealing member includes the part of the coil having the maximum number of turns. 2. The vacuum installation coil according to claim 1,
A coil for vacuum installation, characterized in that the space surrounded by the sealing member is kept at a low pressure compared to the atmosphere. 2. The vacuum installation coil according to claim 1,
A coil for vacuum installation, characterized in that an inert gas is sealed in the space surrounded by the sealing member. 2. The vacuum installation coil according to claim 1,
A coil for vacuum installation, characterized in that the space surrounded by the sealing member is filled with a foamable resin. 2. The vacuum installation coil according to claim 1,
the sealing member comprises a vacuum resistant connector;
A coil for vacuum installation, characterized in that the portion of the coil that is airtightly surrounded by the sealing member and the portion that is not surrounded by the sealing member are electrically connected through the vacuum-resistant connector. A vacuum installation coil according to claim 1;
and a vacuum chamber. 12. The physics package of claim 11,
the coil is a decreasing type coil having a relatively small number of turns downstream of the atomic beam,
the physics package further comprising a counter coil wound around the beam axis at a position spaced downstream of the atomic beam from the decreasing coil;
the decreasing coil and the opposing coil form a gradient magnetic field for a MOT device between the decreasing coil and the opposing coil;
A physics package characterized in that the sealing member airtightly surrounds a portion of the coil including the most upstream side of the beam axis, but does not surround a portion of the coil including the most downstream side. 12. The physics package of claim 11,
the coil is an increasing type coil having a relatively large number of turns on a downstream side of the atomic beam,
the physics package further comprising a counter coil wound around the beam axis at a position spaced downstream of the atomic beam from the increasing coil;
the increasing coil and the opposing coil form a gradient magnetic field for a MOT device between the increasing coil and the opposing coil;
A physics package characterized in that the sealing member airtightly surrounds a portion of the coil including the downstreammost side of the beam axis. A physics package for an optical lattice clock, comprising the physics package described in claim 11. A physics package for an atomic clock, comprising the physics package according to claim 11. A physics package for an atom interferometer comprising the physics package according to claim 11. A physics package for a quantum information processing device for atoms or ionized atoms, comprising the physics package according to claim 11. A sealing member that provides a seal to a coil that is installed in a vacuum chamber and wound around a beam axis through which an atomic beam flows, and that forms a spatially gradient magnetic field,
A sealing member characterized by sealing the space between the coil and the side with indium formed into an annular sheet shape or thick-walled shape, thereby airtightly surrounding part or all of the coil.

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