Magneto-optical trap device

Abstract

This magneto-optical trap device comprises a vacuum vessel in which atoms to be cooled and captured are enclosed, an optical element which, on the basis of laser light supplied from a light source, generates a pair of parallel light beams of circularly polarized light that travel in mutually opposite directions and that have electric field vectors having rotational directions that are the same direction when facing in the respective directions of travel, and a diffraction element which has a plurality of diffractive elements that are arranged with n-fold symmetry (n is an integer of 3 or more) on a plane perpendicular to the directions of travel of the pair of parallel light beams, and which, in response to the incidence of at least one of the pair of parallel light beams, emits diffracted light beams of circularly polarized light having rotation directions that are the opposite directions to those of the incident parallel light beams, and having a prescribed diffraction angle, and the atoms are cooled and captured in a region inside the vacuum container in which the pair of parallel light beams and the diffracted light beams overlap.

Description

Magneto-optical trap device

[0001] The present disclosure relates to magneto-optical trapping devices used to cool and trap atoms.

[0002] Using atoms cooled to cryogenic temperatures, atomic clocks, atomic interferometers, cooled-atom quantum computers, etc. Magneto-optical traps (MOTs) are known as a method for cooling and trapping atoms to cryogenic temperatures.

[0003] As an example of a magneto-optical trap, a technique is disclosed in Patent Document 1 or Non-Patent Document 1, in which an incident laser beam is diffracted using a diffraction grating, the diffracted beam intersects with the incident laser beam, and atoms are cooled and trapped at the center of the intersecting plane. This technique is called a grating magneto-optical trap (GMOT), and enables the miniaturization of magneto-optical trap devices.

[0004] U.S. Pat. No. 1,027,8275

[0005] "A surface-patterned chip as a strong source of ultracold atoms for quantum technologies", CC Nshii et al., Nature Nanotechnology 8, 321 (2013)

[0006] Alkali metal elements and alkaline earth metal elements are considered to be suitable atoms for use in magneto-optical traps. However, in the invention disclosed in Patent Document 1, the types of alkali metal atoms that can be cooled and trapped are limited ( ７ Li, ８７ Rb, ８５ Rb, etc.) For this reason, there is a demand for highly efficient cooling and capture of a wide range of atomic species.

[0007] An object of the present disclosure is to provide a magneto-optical trapping device that is compact and capable of cooling and trapping a wide range of atomic species with high efficiency.

[0008] A magneto-optical trapping device according to one aspect of the present disclosure includes a vacuum vessel enclosing atoms to be cooled and captured; an optical element that generates, based on laser light supplied from a light source, a pair of parallel beams of circularly polarized light that travel in opposite directions and whose electric field vectors rotate in the same direction when facing the respective traveling directions; and a diffraction element having a plurality of diffractive elements arranged in n-fold symmetry (n is an integer of 3 or greater) on a plane perpendicular to the traveling directions of the pair of parallel beams, and that emits diffracted light that is circularly polarized at a predetermined diffraction angle and whose rotation direction is opposite to that of the incident parallel beams, based on the incidence of at least one of the pair of parallel beams. The magneto-optical trapping device cools and captures the atoms in a region inside the vacuum vessel where the pair of parallel beams and the diffracted light overlap.

[0009] According to the present disclosure, a magneto-optical trapping device can be miniaturized and a wide range of atomic species can be cooled and trapped with high efficiency.

[0010] FIG. 1 is a block diagram illustrating a functional configuration of a magneto-optical trapping device according to an embodiment of the present disclosure; FIG. 2 is a flowchart illustrating an example of an operation of the magneto-optical trapping device; FIG. 3 is a diagram illustrating a first configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure; FIG. 4 is a diagram illustrating a first specific example of a plurality of diffractive elements included in a diffraction element; FIG. 5 is a diagram illustrating a second specific example of a plurality of diffractive elements included in a diffraction element; FIG. 6 is a diagram illustrating a third specific example of a plurality of diffractive elements included in a diffraction element; FIG. 7 is a diagram illustrating a fourth specific example of a plurality of diffractive elements included in a diffraction element; FIG. 8 is a diagram illustrating a state of laser light incident on a specific region in a vacuum vessel in a magneto-optical trapping device of a comparative example; FIG. 9 is a diagram illustrating a second configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure; FIG. 10 is a diagram illustrating a modification of the second configuration example; FIG. 11 is a block diagram of optical elements in a magneto-optical trapping device of a third configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure; FIG. 1 is a diagram for explaining a third configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure. FIG. 2 is a block diagram of optical elements in a magneto-optical trapping device according to a fourth configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure. FIG. 3 is a block diagram of optical elements in a magneto-optical trapping device according to a fifth configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure. FIG. 4 is a diagram for explaining the fifth configuration example of a magneto-optical trapping device according to an embodiment of the present disclosure. FIG. 5 is a diagram for explaining an example of a magneto-optical trapping device according to an embodiment of the present disclosure. FIG. 6 is a diagram for explaining an example of a magneto-optical trapping device according to an embodiment of the present disclosure.

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. However, more detailed explanation than necessary, such as detailed explanation of already well-known matters and redundant explanation of substantially the same configuration, may be omitted.

[0012] 1 is a block diagram illustrating the functional configuration of a magneto-optical trap device 100 according to an embodiment of the present disclosure. As shown in FIG. 1, the magneto-optical trap device 100 includes a vacuum vessel 1, a repumping light source 2, a cooling light source 3, a pump 4, a magnetic field generator 5, a control unit 6, an optical element 7, and a diffraction element 8.

[0013] The vacuum vessel 1 is a vessel in which atoms to be cooled and captured are sealed. The inside of the vacuum vessel 1 can be kept at a vacuum by a pump 4. In this embodiment, the inside of the vacuum vessel 1 is kept at an ultra-high vacuum (10 －５ Pa or less), and more preferably, 10 －６ It has the ability to maintain the temperature at or below 100 Pa.

[0014] At least a part of the vacuum vessel 1 is made of a material that is transparent to the laser light generated by the re-pumping light source 2 and the cooling light source 3. An example of the material of the vacuum vessel 1 is glass.

[0015] In the present embodiment, examples of atoms to be cooled and captured include alkali metal atoms, more specifically, Li, K, Rb, Cs, etc.

[0016] The repump light source 2 emits repump light. The repump light source 2 is a light source capable of adjusting the laser frequency near the resonance frequency of the atoms to be cooled and trapped. The repump light source 2 is composed of, for example, an external cavity semiconductor laser. The repump light emitted from the repump light source 2 is incident on a specific region Rs (see Figure 3B described below) inside the vacuum vessel 1. The specific region Rs is a region where atoms are cooled and trapped. Details of the specific region Rs will be described later. The repump light is light for returning atoms that can no longer absorb the cooling laser light described below due to spontaneous emission to a level where they can be trapped.

[0017] The cooling light source 3 emits a cooling laser beam for cooling and trapping atoms. The cooling light source 3 is a light source capable of adjusting the laser frequency near the resonance frequency of the atoms to be cooled and trapped. The cooling light source 3 is configured, for example, by an external cavity semiconductor laser. The cooling laser beam emitted from the cooling light source 3 is converted into a pair of parallel beams by an optical element 7 and enters a specific region Rs inside the vacuum vessel 1. The wavelength of the laser beam generated by the cooling light source 3 may be set based on the atomic species to be cooled and trapped.

[0018] The pump 4 pumps the inside of the vacuum vessel 1 －６ The chamber is evacuated to a vacuum of not more than Pa. Examples of the pump 4 include an ion pump and a getter pump, but other pumps may also be used.

[0019] The magnetic field generating device 5 generates a quadrupole magnetic field for a specific region Rs inside the vacuum vessel 1. The magnetic field generating device 5 is, for example, a pair of anti-Helmholtz coils arranged at positions symmetrical to each other with respect to the specific region Rs inside the vacuum vessel 1.

[0020] The control unit 6 controls the operations of the repumping light source 2, the cooling light source 3, the pump 4, and the magnetic field generator 5. The control unit 6 controls each component of the magneto-optical trap device 100 according to a pre-created program. The control unit 6 may also control each component based on the operation of the user of the magneto-optical trap device 100.

[0021] The optical element 7 generates a pair of parallel beams of light traveling in opposite directions based on the cooling laser light generated by the cooling light source 3 .

[0022] Diffraction element 8 has a plurality of diffractive elements arranged on a plane perpendicular to the traveling direction of the pair of parallel beams, with n-fold symmetry (n is an integer equal to or greater than 3) with respect to a central optical axis. The central optical axis is the central optical axis of the magneto-optical trap formed by magneto-optical trap device 100, and is an optical axis that passes through specific region Rs and is parallel to the traveling direction of the parallel beams.

[0023] The diffraction element 8 emits diffracted light, based on the incidence of at least one of a pair of parallel beams of light, by a plurality of diffraction elements, which travels obliquely with respect to the traveling direction of the parallel beams toward a specific region Rs inside the vacuum vessel 1. The diffraction elements are elements that have a structure with a period approximately equal to the wavelength of light and diffract light. The plurality of diffraction elements arranged with n-fold symmetry with respect to the central optical axis means that when all of the plurality of diffraction elements included in the diffraction element 8 are rotated 360 / n degrees about the central optical axis, they overlap all of the original plurality of diffraction elements.

[0024] With this configuration, the diffraction element 8 emits n-component diffracted light beams (i.e., n components) having the same diffraction angle and diffraction efficiency based on the incidence of at least one of a pair of parallel beams. As a result, the n-component diffracted light beams are incident on the specific region Rs from directions that are n-fold symmetric with respect to the central optical axis. Note that the n-component diffracted light beams are incident from directions that are n-fold symmetric with respect to the central optical axis means that when the incident n-component diffracted light beams are rotated 360 / n degrees around the central optical axis, they overlap with the original diffracted light beams.

[0025] Furthermore, the diffraction element 8 rotates the circularly polarized light of the emitted diffracted light in the opposite direction to the circularly polarized light of the incident light. In this specification, when a certain light is circularly polarized, the rotation direction of the electric field vector when it is oriented in the traveling direction of the light is referred to as the rotation direction of the circularly polarized light of the light.

[0026] In the present disclosure, the diffraction element 8 is configured as either a reflective diffraction element that emits diffracted light on the same side as the incident light, or a transmissive diffraction element that emits diffracted light on the side opposite to the incident light.

[0027] An example of a reflective diffraction element is a thin metal film (such as gold) with periodic concaves and convexes as the diffraction elements. An example of a transmissive diffraction element is a dielectric nanostructure in which a dielectric material with a high refractive index is periodically arranged on a substrate as the diffraction elements. When the diffraction element 8 is placed inside the vacuum vessel 1, it is desirable that it be made of a material that does not react with the alkali metal atoms to be cooled and captured.

[0028] The optical element 7 and the diffraction element 8 will be described in detail in the configuration examples given later.

[0029] 1 , the optical element 7 and the diffraction element 8 are disposed between the vacuum vessel 1 and the cooled-light source 3, but the present disclosure is not limited to this. For example, at least one of the optical element 7 and the diffraction element 8 may be disposed on the opposite side of the vacuum vessel 1 from the cooled-light source 3. Furthermore, at least one of the optical element 7 and the diffraction element 8 may be disposed inside the vacuum vessel 1.

[0030] In the example shown in FIG. 1, the vacuum vessel 1 and the pump 4 are shown as separate components, but for example, a mechanism that functions as the pump 4 may be incorporated into the vacuum vessel 1.

[0031] FIG. 2 is a flowchart for explaining an example of the operation of the magneto-optical trap device 100. In FIG.

[0032] In step S1, the control unit 6 operates the pump 4 to create a vacuum (10 －６ In the following steps, the pump 4 continues to operate.

[0033] In step S2, the control unit 6 supplies the alkali metal atomic gas to be cooled and captured into the vacuum vessel 1 from a predetermined supply source.

[0034] In step S3, the control unit 6 operates the magnetic field generating device 5 to apply a quadrupole magnetic field to the specific region Rs inside the vacuum vessel 1.

[0035] In step S4, the control unit 6 operates the repumping light source 2 and the cooling light source 3 to form a magneto-optical trap in the specific region Rs inside the vacuum vessel 1. As a result, atoms to be cooled are cooled and trapped in the specific region Rs.

[0036] <Configuration Example of Magneto-Optical Trap Device> A specific configuration example of the magneto-optical trap device 100 according to the embodiment of the present disclosure will be described below.

[0037] 3A and 3B are diagrams illustrating a first configuration example of the magneto-optical trap device 100 according to an embodiment of the present disclosure. FIG. 3A is a block diagram of the optical element 7 in the magneto-optical trap device 100 of the first configuration example. FIG. 3B shows laser light incident on the specific region Rs in the first configuration example. FIG. 3B is a schematic perspective view of the interior of the vacuum vessel 1. Although not shown, a quadrupole magnetic field is applied to the interior of the vacuum vessel 1 by the magnetic field generator 5. Although not shown, repump light is incident on the specific region Rs from the repump light source 2 of FIG. 1.

[0038] 3A , the optical element 7 includes a first collimated light generating unit 71 and a second collimated light generating unit 72. The first collimated light generating unit 71 generates a first collimated light Lp1 based on the laser light generated by the cooling light source 3. The second collimated light generating unit 72 generates a second collimated light Lp2 based on the laser light generated by the cooling light source 3. The first collimated light Lp1 and the second collimated light Lp2 are either of a pair of collimated lights traveling in opposite directions. The first collimated light Lp1 and the second collimated light Lp2 are circularly polarized lights whose electric field vectors rotate in the same direction when facing their respective traveling directions.

[0039] The pair of parallel beams generated by the first parallel beam generating unit 71 and the second parallel beam generating unit 72 are incident on the vacuum chamber 1 so as to face each other. In the following description, the traveling direction of the first parallel beam Lp1 is referred to as the first direction, and the traveling direction of the second parallel beam Lp2 is referred to as the second direction. The first direction and the second direction are opposite to each other. Note that in FIG. 3B , the first parallel beam Lp1 and the second parallel beam Lp2, which are parallel beams, are illustrated as solid arrows pointing toward the specific region Rs. The first parallel beam generating unit 71 and the second parallel beam generating unit 72 are not illustrated in FIG. 3B .

[0040] 3B, the first parallel light Lp1 and the second parallel light Lp2 are incident in opposing directions toward the inside of the vacuum vessel 1. The first direction, which is the traveling direction of the first parallel light Lp1, and the second direction, which is the traveling direction of the second parallel light Lp2, are opposing directions along the central optical axis.

[0041] In the first configuration example, the diffraction element 8 is disposed between the specific region Rs and the second collimated light generating unit 72. The diffraction element 8 may be disposed either inside or outside the vacuum vessel 1. The diffraction element 8 is disposed on a plane P perpendicular to the propagation directions (i.e., the first and second directions) of the pair of collimated light beams generated by the first collimated light generating unit 71 and the second collimated light generating unit 72. The diffraction element 8 is a reflective diffraction element. The first collimated light beam Lp1 is incident on the diffraction element 8 (from the top of the paper in FIG. 3B ) and the diffraction element 8 emits diffracted light beam Ld on the same side as the incident side. Based on the incidence of at least one of the pair of collimated light beams (here, the first collimated light beam Lp1), the diffraction element 8 emits diffracted light beam Ld, which is circularly polarized light with a rotation direction opposite to that of the incident collimated light beam (the first collimated light beam Lp1) at a predetermined diffraction angle.

[0042] 3B, the diffraction element 8 is formed in a circular ring shape with an opening 81 at its center. The opening 81 is provided to allow the second parallel light Lp2 to pass through. The second parallel light Lp2 passes through the opening 81 of the diffraction element 8 and enters the specific region Rs (from the lower side of the paper in FIG. 3B).

[0043] 4A to 4D are diagrams for explaining specific examples of multiple diffractive elements possessed by a diffractive element. FIGS. 4A to 4D show top views and schematic diagrams of specific examples of the diffractive element 8. FIG. 4A shows a diffractive element 82 as a first specific example of the diffractive element 8. As shown in FIG. 4A, the diffractive element 82 has multiple grooves 82a arranged concentrically and periodically as diffractive elements, and circular openings 82b. While the multiple grooves 82a appear to be spaced relatively far apart in FIG. 4A, in reality, the distance between the grooves 82a is approximately the wavelength of light. The diffractive element 82 shown in FIG. 4A is the diffractive element 8 shown in FIG. 3B, and the openings 82b shown in FIG. 4A correspond to the openings 81 shown in FIG. 3B. Although not shown in FIG. 3B, the diffractive element 8 shown in FIG. 3B actually has grooves 82a as diffractive elements, as shown in FIG. 4A.

[0044] As shown in FIG. 3B , the diffraction element 8 reflects the first parallel light Lp1 to emit diffracted light Ld at a predetermined diffraction angle relative to the central optical axis of the magneto-optical trap (which coincides with the central axis of the annular shape). Here, since the diffraction element 8 shown in FIG. 3B is an annular diffraction element 82 having grooves 82a that are concentric diffracting elements, the diffraction element 8 (82) can emit diffracted light Ld that travels toward the specific region Rs from all directions around its circumference. In FIG. 3B , the diffracted light Ld emitted by the annular diffraction element 8 is indicated by four hollow arrows. The predetermined diffraction angle can be appropriately adjusted depending on the position of the diffraction element 8 (82) so that the diffracted light Ld travels toward the specific region Rs.

[0045] The specific region Rs is a region inside the vacuum vessel 1 where a pair of parallel beams (first parallel beam Lp1 and second parallel beam Lp2) and the diffracted beam Ld overlap. The specific region Rs is also located approximately at the center of the pair of coils that make up the magnetic field generating device 5. Atoms inside the vacuum vessel 1 are cooled and captured near the center of the quadrupole magnetic field due to radiation pressure caused by the parallel beams and diffracted beams, as well as the influence of the quadrupole magnetic field.

[0046] The diffraction element 8 may be disposed inside the vacuum vessel 1 or outside the vacuum vessel 1 .

[0047] As described above, in the first configuration example, the diffraction element 82 has grooves 82a as multiple diffraction elements on a plane perpendicular to the traveling direction of the pair of parallel light beams. Here, the diffraction element 82 is disposed at a position where the specific region Rs is the center of symmetry of the multiple diffraction elements when the specific region Rs is projected onto the plane P on which the diffraction element 82 is disposed. In the example shown in Fig. 4A, the grooves 82a as the diffraction elements of the diffraction element 82 are disposed concentrically. The grooves 82a shown in Fig. 4A are an example of multiple diffraction elements in the present disclosure that are disposed with n-fold symmetry with respect to the central optical axis.

[0048] With this configuration, in the first configuration example, the diffraction element 8 (82) can cause the diffracted light Ld to be incident on the specific region Rs from all directions around its circumference (i.e., from n-fold symmetric directions when n = ∞). Furthermore, because the diffraction element 82 has the grooves 82a arranged concentrically and periodically, the diffraction element 8 (82) can emit n components of diffracted light Ld, each with the same diffraction angle and diffraction efficiency.

[0049] Furthermore, the diffraction element 8 rotates the circularly polarized light of the emitted diffracted light in the opposite direction to the circularly polarized light of the incident light (here, the first parallel light Lp1).

[0050] When the specific region Rs is projected onto the plane P on which the diffraction element 8 is disposed, the position of the specific region Rs is the center position of the annular and concentric diffraction elements of the diffraction element 8. As a result, diffracted light Ld is incident on the specific region Rs from all circumferential directions of the diffraction element 8.

[0051] The structure of the diffraction element in the present disclosure is not limited to the above-described example. In the present disclosure, the outer shape of the diffraction element and the shape of the opening may be rotationally symmetric with respect to the central optical axis, but are not particularly limited thereto, and any appropriate shape may be adopted. Furthermore, the shape of the diffractive elements of the diffraction element does not have to be the shape of grooves arranged concentrically.

[0052] Other examples of diffractive elements in the present disclosure include regular n-gonal grooves or four-fold symmetric recesses arranged on a square lattice. Fig. 4B shows a diffractive element 83 as a second specific example of a diffractive element. As shown in Fig. 4B, the diffractive element 83 has grooves 83a arranged in the shape of an equilateral triangle around the central optical axis as diffractive elements, and equilateral triangular openings 83b.

[0053] 4C shows a third specific example of a diffraction element, namely, a diffraction element 84. As shown in FIG. 4C, the diffraction element 84 has square recesses 84a and square openings 84b arranged on a square lattice as diffraction elements.

[0054] 4D shows a diffraction element 85 as a fourth specific example of a diffraction element. As shown in FIG. 4D, the diffraction element 85 has circular recesses 85a and square openings 85b arranged in a square lattice as diffraction elements. In this way, even the diffraction elements 83, 84, and 85 having diffraction elements of various shapes (grooves 83a, recesses 84a, and recesses 85a) can emit diffracted light beams traveling in each direction with n-fold symmetry toward the specific region Rs.

[0055] With this configuration, a pair of parallel light beams, a first parallel light beam Lp1 and a second parallel light beam Lp2, traveling in opposite directions are incident on the specific region Rs inside the vacuum vessel 1. In addition to these, diffracted light beam Ld traveling in an oblique direction relative to the central optical axis is incident on the specific region Rs. The diffracted light beam Ld is incident on the specific region Rs from all around the circumference of the diffraction element 8. The rotation directions of the circularly polarized light of the first parallel light beam Lp1 and the second parallel light beam Lp2 are the same, and the rotation directions of the circularly polarized light of the first parallel light beam Lp1 and the diffracted light beam Ld are opposite to each other.

[0056] As a result, atoms to be cooled and captured within the vacuum chamber 1 are subjected to radiation pressure from the first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld. The first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld each travel toward the specific region Rs. The frequencies of these lights are set slightly lower than the resonant frequency of the atoms. Due to the Doppler effect, the frequency of light seen from the atoms is closer to the resonant frequency of the atoms in the direction opposite to the direction of the atoms' velocity than in the direction of the atoms' velocity. Therefore, the atoms are subjected to stronger radiation pressure from the light traveling in the opposite direction. This causes the atoms to decelerate. Furthermore, due to the shift in the resonant frequency of the atoms caused by the magnetic field, the frequency of light traveling toward the center of the quadrupole magnetic field is closer to the resonant frequency of the atoms than the frequency of light traveling away from the center. Therefore, the atoms are subjected to stronger radiation pressure toward the center of the quadrupole magnetic field, and are concentrated near the center of the quadrupole magnetic field within the specific region Rs.

[0057] In order for atoms to be suitably cooled and trapped within the specific region Rs and at the center of the quadrupole magnetic field, the intensities of the first parallel light Lp1 and the second parallel light Lp2, as well as the optical characteristics of the optical element 7 and the diffraction element 8 (such as the diffraction efficiency and diffraction angle of the diffraction element 8), must be appropriately set so as to maintain a balance between the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld incident on the specific region Rs. These parameters may be experimentally set based on the atomic species to be cooled and trapped, the characteristics of the cooling laser light used, and the like. This allows the magneto-optical trap device 100 to efficiently cool and trap atoms in the specific region Rs.

[0058] (Comparison between the first configuration example and the comparative example) The effect of the magneto-optical trap device 100 according to the embodiment of the present disclosure will be explained by comparing the first configuration example of the magneto-optical trap device 100 according to the embodiment of the present disclosure shown in FIG. 3 with the comparative example.

[0059] 5 is a diagram showing the cooling laser light incident on a specific region Rs in a vacuum vessel in a magneto-optical trap device 500 of the comparative example. In the magneto-optical trap device 500 of the comparative example, parallel light Lp, which is parallel light traveling in a first direction, and diffracted light Ld, which is obtained by reflecting the parallel light Lp by a diffraction element 507, are incident on the specific region Rs. Therefore, the comparative example differs from the first exemplary configuration of the magneto-optical trap device 100 according to the embodiment of the present disclosure shown in FIG. 3B in that there is no opening in the diffraction element and no incidence of second parallel light Lp2. Note that in FIG. 5, the traveling direction of the parallel light Lp is shown as the first direction, and the opposite direction is shown as the second direction.

[0060] As described above, in order to efficiently cool and trap atoms in a magneto-optical trapping device, the radiation pressure of the laser beam applied to the specific region Rs must be three-dimensionally symmetric and the intensity of the radiation pressure must be balanced. In the comparative magneto-optical trapping device 500 shown in FIG. 5 , the radiation pressure of the laser beam applied to the specific region Rs includes a first-direction component due to the parallel light Lp, a second-direction component due to the diffracted light Ld, and multiple directional components perpendicular to the second direction. Because the diffractive elements of the diffraction element 507 are concentrically arranged, the intensity of the multiple directional components perpendicular to the second direction due to the diffracted light Ld is balanced. Therefore, in the comparative magneto-optical trapping device 500, it is assumed that atoms can be cooled and trapped in the specific region Rs by maintaining an intensity balance between the first-direction component of the radiation pressure due to the parallel light Lp and the second-direction component of the radiation pressure due to the diffracted light Ld.

[0061] However, since the intensity of the diffracted light Ld generated by reflection is generally weaker than that of the incident light, when only the parallel light Lp and the diffracted light Ld are incident on the specific region Rs, as in the comparative example of Figure 5, it may be difficult to maintain the balance of the radiation pressure in the specific region Rs.

[0062] 3, the second parallel light Lp2 is further incident on the specific region Rs, which makes it easier to maintain the balance of the radiation pressure in the specific region Rs compared to the comparative example in which the second parallel light Lp2 is not incident, thereby improving the performance of trapping atoms in the specific region Rs.

[0063] In a magneto-optical trapping device that cools and traps atoms by irradiating a specific region Rs with parallel light traveling in one direction and diffracted light traveling obliquely relative to that direction, as shown in Figure 5, recent research has revealed that the larger the atomic number, the larger the nuclear spin, making it more difficult to cool and trap atoms. ７ Li, ８７ Rb, ８５Although atoms such as Rb can be cooled, it is known that it is difficult to suitably cool Cs, which has a higher atomic number.

[0064] In a first configuration example of the magneto-optical trap device 100 according to the embodiment of the present disclosure, not only the first parallel light Lp1 but also a second parallel light Lp2 traveling in the opposite direction to the first parallel light Lp1 is incident on the specific region Rs. This makes it possible to compensate for the radiation pressure in the second direction generated by the second parallel light Lp2, thereby increasing the number of atomic species that can be cooled and trapped. Specifically, in the first configuration example of the magneto-optical trap device 100 according to the embodiment of the present disclosure, the intensities of the first parallel light Lp1 and the second parallel light, the diffraction efficiency of the diffraction element 8, which is a reflective diffraction element, and the like are adjusted, and then the intensity ratio between these is adjusted. １３３ Experiments have shown that it is possible to cool and capture Cs.

[0065] As described above, according to the first exemplary configuration of the magneto-optical trap device 100 according to the embodiment of the present disclosure, the second parallel light Lp2 traveling in the opposite direction to the first parallel light Lp1 is further incident, which makes it easier to maintain the balance of the radiation pressure of the laser light acting on the specific region Rs, thereby increasing the number of atomic species that can be cooled and trapped, and achieving efficient cooling.

[0066] (Second Configuration Example) The magneto-optical trap device according to the present disclosure is not limited to the first configuration example described above, and may have a number of configurations. Below, a second configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure will be described.

[0067] 6A and 6B are diagrams illustrating a second configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure. Fig. 6A is a block diagram of optical element 7 in magneto-optical trap device 100 of the second configuration example. Fig. 6B shows laser light incident on specific region Rs in the second configuration example. Fig. 6B is a schematic perspective view of the interior of vacuum vessel 1.

[0068] 6A, in the second configuration example of magneto-optical trap device 100, second collimated light generating section 72 of optical element 7 has a mirror 721 and a quarter-wave plate 722. Mirror 721 reflects first collimated light Lp1 to generate second collimated light Lp2.

[0069] 6B , the mirror 721 and the quarter-wave plate 722 are disposed on a side of the specific region Rs opposite to the side on which the first parallel light Lp1 is incident (hereinafter referred to as the incident side). The mirror 721 is disposed perpendicular to the traveling direction (first direction) of the first parallel light Lp1. The quarter-wave plate 722 is disposed adjacent to the mirror 721 on the incident side of the mirror 721.

[0070] The quarter-wave plate 722 imparts a phase difference of π / 2 between the two orthogonal polarization components of the first collimated light Lp1. The first collimated light Lp1 passes through the quarter-wave plate 722 before and after reflection by the mirror 721, and as a result, the rotation direction of the circularly polarized light of the second collimated light Lp2 becomes the same as the rotation direction of the circularly polarized light of the first collimated light Lp1.

[0071] In the second configuration example, the second collimated light generating unit 72 of the optical element 7 reflects the first collimated light Lp1 that has passed through the specific region Rs using a mirror 721, and emits the second collimated light Lp2 of the pair of collimated lights.

[0072] That is, in the second configuration example, the specific region Rs is incident with the first parallel light Lp1, the diffracted light Ld emitted from the diffraction element 8 based on the first parallel light Lp1, and the second parallel light Lp2 obtained by reflecting the first parallel light Lp1 by the mirror 721. The first parallel light Lp1 travels along the first direction, and the second parallel light Lp2 travels along the second direction. As a result, the first parallel light Lp1 and the second parallel light Lp2 are incident on the specific region Rs in directions opposing each other.

[0073] The diffraction element 8 is a reflective diffraction element, similar to the first configuration example. The diffraction element 8 is disposed on a plane P perpendicular to the first direction and the second direction. By reflecting the first parallel light Lp1, the diffraction element 8 emits diffracted light Ld that travels in an oblique direction with respect to the central optical axis.

[0074] 6B , the shape of the diffraction element 8 is annular, but the present disclosure is not limited to this, and the outer shape of the diffraction element 8 may be any shape. Also, similar to the first configuration example, the diffraction element 8 has a plurality of diffraction elements arranged in n-fold symmetry (n is an integer of 3 or more) with respect to the central optical axis.

[0075] The opening 81 of the diffraction element 8 is provided to allow the first parallel light Lp1 incident on the mirror 721 and the quarter-wave plate 722 and the second parallel light Lp2 reflected by the mirror 721 to pass through.

[0076] The second configuration example can also achieve the same effect as the first configuration example. That is, a pair of parallel light beams, a first parallel light beam Lp1 and a second parallel light beam Lp2, traveling in opposite directions are incident on a specific region Rs inside the vacuum vessel 1. In addition, the diffraction element 8 reflects the first parallel light beam Lp1 to emit diffracted light beam Ld. The diffracted light beam Ld travels obliquely with respect to the central optical axis from the entire circumferential direction of the diffraction element 8 and enters the specific region Rs. The circularly polarized light beams of the first parallel light beam Lp1 and the second parallel light beam Lp2 rotate in the same direction, but the circularly polarized light beams of the first parallel light beam Lp1 and the diffracted light beam Ld rotate in opposite directions.

[0077] In this way, due to the influence of each light beam incident on the specific region Rs and the quadrupole magnetic field, the atoms are subjected to radiation pressure in a direction toward the center of the quadrupole magnetic field, and are suitably cooled and trapped.

[0078] As in the first configuration example, the intensities of the first parallel light Lp1 and the second parallel light Lp2, as well as the optical characteristics of the optical element 7 and the diffraction element 8 (such as the reflectivity of the mirror 721 and the diffraction efficiency and diffraction angle of the diffraction element 8) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld incident on the specific region Rs. This allows the magneto-optical trap device 100 to efficiently cool and trap atoms in the specific region Rs.

[0079] (Modification of Second Configuration Example) Note that, in the example shown in Fig. 6B, the mirror 721 and the quarter-wave plate 722 are disposed at positions separate from the diffraction element 8, but the present disclosure is not limited to this. Figs. 7A and 7B are diagrams for explaining a modification of the second configuration example in which the mirror 721 and the quarter-wave plate 722 included in the optical element 7 are integrally configured with the diffraction element 8. Fig. 7 is a schematic side view of the interior of the vacuum vessel 1.

[0080] 7A shows a modified example in which a quarter-wave plate 722 and a mirror 721 are arranged on the surface opposite the incident side of the diffraction element 8 so as to cover the opening 81. Also, FIG. 7B shows a modified example in which a quarter-wave plate 722 and a mirror 721 of the same size as the opening 81 of the diffraction element 8 in FIG. 7A are arranged on the incident side of the diffraction element 8, which does not have an opening. Even with these modified examples, it is possible to obtain the same effect as the second configuration example. In this way, by creating an optical device in which the mirror 721, the quarter-wave plate 722, and the diffraction element 8 are integrated and then arranging the optical device adjacent to the vacuum vessel 1, for example, outside the vacuum vessel 1, it is possible to obtain the same effect as the second configuration example.

[0081] It is also possible to prepare in advance a plurality of optical devices each having different optical properties, such as the mirror 721, the quarter-wave plate 722, and the diffraction element 8. In this case, it becomes possible to appropriately replace optical devices having various optical properties in accordance with the atomic species to be cooled.

[0082] (Third Configuration Example) A third configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure will be described. Figures 8A and 8B are diagrams for explaining the third configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure. The third configuration example of magneto-optical trap device 100 differs from the first and second configuration examples in that diffraction element 8 is a transmissive diffraction element.

[0083] Fig. 8A is a block diagram of optical element 7 in magneto-optical trap device 100 of the third configuration example. Fig. 8B shows the cooling laser light incident on specific region Rs in the third configuration example. Fig. 8B is a schematic perspective view of the inside of vacuum vessel 1.

[0084] 8A , in the third configuration example, similar to the first configuration example, the optical element 7 includes a first collimated light generating unit 71 and a second collimated light generating unit 72. The first collimated light generating unit 71 generates a first collimated light Lp1 based on the laser light generated by the cooling light source 3. The second collimated light generating unit 72 generates a second collimated light Lp2 based on the laser light generated by the cooling light source 3. The first collimated light Lp1 and the second collimated light Lp2 are either of a pair of collimated lights traveling in opposite directions. The first collimated light Lp1 and the second collimated light Lp2 are circularly polarized lights whose electric field vectors rotate in the same direction when facing their respective traveling directions.

[0085] As a result, the pair of parallel beams of light generated by the optical element 7 enter the vacuum vessel 1 so as to face each other.

[0086] The diffraction element 8, which is a transmissive diffraction element, receives incident light and emits diffracted light Ld on the side opposite to the incident light. The diffraction element 8 is disposed on a plane P perpendicular to the first and second directions. In the example shown in FIG. 8B , the shape of the diffraction element 8 is annular, but the present disclosure is not limited to this, and the outer shape of the diffraction element 8 may be any shape. Similar to other configuration examples, the diffraction element 8 has multiple diffraction elements arranged in n-fold symmetry (n is an integer greater than or equal to 3) with respect to the central optical axis. The diffraction element 8 may, for example, have a dielectric nanostructure in which a dielectric material with a high refractive index is periodically arranged on a substrate as the diffraction elements.

[0087] The diffraction element 8 emits diffracted light Ld, which travels in an oblique direction relative to the central optical axis, from all directions around the circumference of the annular shape. In this case, the diffraction element 8 rotates the circularly polarized light of the incident light in the opposite direction to the circularly polarized light of the outgoing diffracted light.

[0088] The opening 81 of the diffraction element 8 is provided to allow the first parallel light Lp1 incident on the specific region Rs to pass through.

[0089] The third configuration example can also achieve the same effects as the other configuration examples. That is, a pair of parallel light beams, a first parallel light beam Lp1 and a second parallel light beam Lp2, traveling in opposite directions, are incident on the specific region Rs inside the vacuum vessel 1. In addition, diffracted light Ld, which is emitted by the diffraction element 8 after transmitting the first parallel light beam Lp1, and travels in a direction oblique to the central optical axis, is incident on the specific region Rs. The first parallel light beam Lp1 and the second parallel light beam Lp2 have the same rotation direction of the circularly polarized light, while the rotation direction of the circularly polarized light of the first parallel light beam Lp1 and the circularly polarized light of the diffracted light Ld are opposite to each other.

[0090] In this way, due to the influence of each light beam incident on the specific region Rs and the quadrupole magnetic field, the atoms are subjected to radiation pressure in a direction toward the center of the quadrupole magnetic field, and are suitably cooled and trapped.

[0091] As in the other configuration examples, the intensities of the first parallel light Lp1 and the second parallel light Lp2, as well as the optical characteristics of the optical element 7 and the diffraction element 8 (such as the transmittance and diffraction angle of the diffraction element 8) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, and the diffracted light Ld incident on the specific region Rs. This allows the magneto-optical trap device 100 to efficiently cool and trap atoms in the specific region Rs.

[0092] (Fourth Configuration Example) A fourth configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure will be described. In the fourth configuration example, a first parallel light beam traveling along a first direction is reflected by mirror 721, and the parallel light beam is transmitted by diffraction element 8, which is a transmissive diffraction element, to emit diffracted light.

[0093] 9A and 9B are diagrams illustrating a fourth configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure. Fig. 9A is a block diagram of optical element 7 in magneto-optical trap device 100 of the fourth configuration example. Fig. 9B shows laser light incident on specific region Rs in the fourth configuration example. Fig. 9B is a schematic diagram of the inside of vacuum vessel 1 as viewed from the side.

[0094] 9A , in the fourth configuration example of the magneto-optical trap device 100, similarly to the second configuration example, the second collimated light generating unit 72 of the optical element 7 has a mirror 721 and a quarter-wave plate 722. The mirror 721 reflects the first collimated light Lp to generate the second collimated light Lr.

[0095] 9B , the mirror 721 and the quarter-wave plate 722 are disposed on the side of the specific region Rs opposite to the side (incident side) on which the first parallel light Lp is incident. The mirror 721 is disposed perpendicular to the traveling direction (first direction) of the parallel light Lp. The quarter-wave plate 722 is disposed adjacent to the mirror 721 on the incident side of the mirror 721.

[0096] 9B , in the fourth configuration example, the specific region Rs is incident with the first parallel light Lp, the diffracted light Ld emitted from the diffraction element 8 in response to the incidence of the first parallel light Lp, and the second parallel light Lr obtained by reflecting the first parallel light Lp by the mirror 721. The first parallel light Lp travels along the first direction, and the second parallel light Lr travels along the second direction. As a result, the first parallel light Lp and the second parallel light Lr are incident on the specific region Rs in directions opposing each other.

[0097] The diffraction element 8 is a transmissive diffraction element, similar to the third configuration example. The diffraction element 8 transmits the first parallel light Lp and thereby emits diffracted light Ld. The diffraction element 8 is disposed on a plane P perpendicular to the first direction and the second direction. In the example shown in FIG. 9B , the shape of the diffraction element 8 is annular, but the present disclosure is not limited thereto, and the outer shape of the diffraction element 8 may be any shape. Also, similar to the other configuration examples, the diffraction element 8 has multiple diffraction elements arranged in n-fold symmetry (n is an integer greater than or equal to 3) with respect to the central optical axis.

[0098] The diffraction element 8 emits diffracted light Ld, which travels in an oblique direction relative to the central optical axis, from all directions around the circumference of the annular shape. In this case, the diffraction element 8 rotates the circularly polarized light of the incident light in the opposite direction to the circularly polarized light of the outgoing diffracted light.

[0099] The opening 81 of the diffraction element 8 is provided to allow the first parallel light Lp incident on the specific region Rs, the mirror 721 and the quarter-wave plate 722 to pass through.

[0100] The fourth configuration example can also achieve the same effects as the other configuration examples. That is, a pair of parallel light beams, a first parallel light beam Lp and a second parallel light beam Lr, traveling in opposite directions, are incident on the specific region Rs inside the vacuum vessel 1. In addition, diffracted light Ld traveling in an oblique direction relative to the central optical axis is incident on the specific region Rs. The diffracted light Ld is obtained by diffracting the first parallel light beam Lp incident on the diffraction element 8 and emitting it in the opposite direction. The rotation directions of the circularly polarized light of the first parallel light beam Lp and the second parallel light beam Lr are the same, and the rotation directions of the circularly polarized light of the first parallel light beam Lp and the diffracted light Ld are opposite to each other.

[0101] In this way, due to the influence of each light beam incident on the specific region Rs and the quadrupole magnetic field, the atoms are subjected to radiation pressure in a direction toward the center of the quadrupole magnetic field, and are suitably cooled and trapped.

[0102] As in the other configuration examples, the intensities of the first parallel light Lp and the second parallel light Lr and the optical characteristics of the optical element 7 and the diffraction element 8 (such as the reflectance of the mirror 721 and the transmittance and diffraction angle of the diffraction element 8) may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first parallel light Lp, the second parallel light Lr, and the diffracted light Ld incident on the specific region Rs. This allows the magneto-optical trap device 100 to efficiently cool and trap atoms in the specific region Rs.

[0103] (Fifth Configuration Example) A fifth configuration example of the magneto-optical trap device 100 according to an embodiment of the present disclosure will be described. In the fifth configuration example, a first parallel light beam and a second parallel light beam traveling in two opposing directions are transmitted through a diffraction element 8, which is a transmissive diffraction element, to emit diffracted light beams. The diffraction element 8 is similar to those in the third and fourth configuration examples.

[0104] 10A and 10B are diagrams illustrating a fifth configuration example of magneto-optical trap device 100 according to an embodiment of the present disclosure. Fig. 10A is a block diagram of optical element 7 in magneto-optical trap device 100 of the fifth configuration example. Fig. 10B shows laser light incident on specific region Rs in the fifth configuration example. Fig. 10B is a schematic diagram of the inside of vacuum vessel 1 as viewed from the side.

[0105] 10A , in the fifth configuration example, similar to the first configuration example, the optical element 7 includes a first collimated light generating unit 71 and a second collimated light generating unit 72. The first collimated light generating unit 71 generates a first collimated light Lp1 based on the laser light generated by the cooling light source 3 (see FIG. 1 ). The second collimated light generating unit 72 generates a second collimated light Lp2 based on the laser light generated by the cooling light source 3. The first collimated light Lp1 and the second collimated light Lp2 are either of a pair of collimated lights traveling in opposite directions. The first collimated light Lp1 and the second collimated light Lp2 are circularly polarized lights whose electric field vectors rotate in the same direction when facing their respective traveling directions.

[0106] As a result, the pair of parallel beams of light generated by the optical element 7 enter the vacuum vessel 1 so as to face each other.

[0107] The two diffraction elements 8A and 8B are transmissive diffraction elements. As shown in FIG. 10B , in the fifth configuration example, the diffraction element 8A is disposed between the incident side of the first parallel light Lp1 and the specific region Rs. The diffraction element 8B is disposed between the incident side of the second parallel light Lp2 and the specific region Rs. The diffraction element 8A diffracts the incident first parallel light Lp1 and emits the first diffracted light Ld1 obliquely relative to the central optical axis, which enters the specific region Rs. The diffraction element 8B diffracts the incident second parallel light Lp2 and emits the second diffracted light Ld2 obliquely relative to the central optical axis, which enters the specific region Rs. The rotation direction of the circularly polarized light of the first parallel light Lp1 and the first diffracted light Ld1 are opposite to each other. The rotation direction of the circularly polarized light of the second parallel light Lp2 and the second diffracted light Ld2 are opposite to each other.

[0108] The diffraction element 8 has openings 81A and 81B which are provided to allow the first parallel light Lp1 and the second parallel light Lp2 to pass through, respectively.

[0109] The fifth configuration example also achieves the same effects as the other configuration examples. That is, a pair of parallel light beams, a first parallel light beam Lp1 and a second parallel light beam Lp2, traveling in opposite directions, are incident on a specific region Rs inside the vacuum vessel 1. In addition, a first diffracted light beam Ld1 traveling in an oblique direction with respect to the central optical axis obtained by diffracting the first parallel light beam Lp1 and outputting it from the diffraction element 8A, and a second diffracted light beam Ld2 traveling in an oblique direction with respect to the central optical axis obtained by diffracting the second parallel light beam Lp2 and outputting it from the diffraction element 8B, are incident on the specific region Rs. The first parallel light beam Lp1 and the second parallel light beam Lp2 have the same rotation direction of the circularly polarized light, and the rotation direction of the circularly polarized light of the first parallel light beam Lp1 and the second parallel light beam Lp2 is opposite to that of the first diffracted light beam Ld1 and the second diffracted light beam Ld2.

[0110] In this way, due to the influence of the first parallel light Lp1, the second parallel light Lp2, the first diffracted light Ld1 and the second diffracted light Ld2 incident on the specific region Rs and the quadrupole magnetic field, the atoms are subjected to radiation pressure in a direction toward the center of the quadrupole magnetic field, and are suitably cooled and captured.

[0111] In the fifth configuration example, similarly to the other configuration examples, the intensities of the first parallel light Lp1 and the second parallel light Lp2, the first diffracted light Ld1, and the second diffracted light Ld2 incident on the specific region Rs may be appropriately set so as to maintain a balance among the intensities of the radiation pressures caused by the first parallel light Lp1, the second parallel light Lp2, the first diffracted light Ld1, and the second diffracted light Ld2. This allows the magneto-optical trap device 100 to efficiently cool and trap atoms in the specific region Rs.

[0112] According to the fifth configuration example, the number of diffracted light components incident on the specific region Rs is increased compared to the other configuration examples, which makes it easier to maintain the balance of the radiation pressure that cools atoms in the specific region Rs. This is thought to enable the cooling of more atomic species.

[0113] <Example> As an example of the magneto-optical trap device of the present disclosure, the results of an experiment conducted on the second configuration example described above (in which parallel light is reflected using a mirror and diffracted light based on the reflection of the parallel light is emitted using a reflective diffraction element) will be described.

[0114] 11A to 11C are diagrams for explaining an example of a magneto-optical trap device according to the present disclosure. Fig. 11A is a schematic diagram showing the arrangement of a vacuum vessel, a diffraction element, and a mirror in the example. Fig. 11A shows the vacuum vessel as viewed from the side.

[0115] In this example, a vacuum chamber with a high degree of vacuum was filled with Cs gas, and an optical device was placed on the outer surface of the vacuum chamber facing the laser light incident side. The optical device was composed of four reflective diffraction elements, each 22 mm square with small circular depressions periodically arranged in a square lattice pattern on the surface. A square opening 10 mm on a side was provided in the center of the optical device. Figure 11B shows the arrangement of the diffraction elements. Figure 11B shows the diffraction element as viewed from the incident side.

[0116] Circularly polarized parallel light detuned approximately 10 MHz negatively from the resonance frequency of the Cs atoms was incident on the entrance side of the vacuum chamber. Under this condition, a magnetic field generator (not shown in Fig. 11) was operated to generate a quadrupole magnetic field inside the vacuum chamber. Furthermore, repump light (not shown in Fig. 11) was incident on the specific region.

[0117] Fig. 11C shows a CMOS camera image of fluorescence from a group of Cs atoms cooled in a specific region. Similar to Fig. 11A, Fig. 11C shows a side view of the interior of the vacuum chamber. As shown in Fig. 11C, the magneto-optical trapping device of the present disclosure can effectively cool and trap Cs atoms.

[0118] The disclosures of the specification, drawings and abstract contained in Japanese Patent Application No. 2024-147567, filed on August 29, 2024, are incorporated herein by reference in their entirety.

[0119] The present disclosure is useful for miniaturizing magneto-optical trapping devices for cooling a variety of atomic species.

[0120] REFERENCE SIGNS LIST 100 Magneto-optical trap device 1 Vacuum vessel 2 Repumping light source 3 Cooling light source 4 Pump 5 Magnetic field generator 6 Control unit 7 Optical element 71 First parallel light generating unit 72 Second parallel light generating unit 721 Mirror 722 1 / 4 wavelength plate 8 Diffraction element 81 Aperture Rs Specific region

Claims

1. A magneto-optical trap device comprising: a vacuum vessel that encloses atoms to be cooled and captured; an optical element that generates, based on laser light supplied from a light source, a pair of parallel beams of circularly polarized light that travel in opposite directions and have the same rotation direction of their electric field vectors when facing in their respective directions of travel; and a diffraction element having a plurality of diffractive elements arranged in n-fold symmetry (n is an integer of 3 or more) on a plane perpendicular to the direction of travel of the pair of parallel beams, and that emits diffracted light that is circularly polarized and has the opposite rotation direction to the incident parallel beam at a predetermined diffraction angle based on the incidence of at least one of the pair of parallel beams; and 2. The magneto-optical trap device of claim 1, wherein the diffraction element is positioned on the side opposite to the side where one of the pair of parallel beams enters the region, and has an opening that diffracts the one of the incident parallel beams toward the incident side and emits diffracted light, and passes the other of the pair of parallel beams, and the one of the parallel beams, the other of the pair of parallel beams that has passed through the opening, and the diffracted light emitted by the diffraction element are incident on the region.

3. The magneto-optical trap device according to claim 1, wherein the diffraction element is arranged on the side opposite to the side where one of the pair of parallel beams enters the region, diffracts the one of the incident parallel beams toward the incident side and emits diffracted beams, and has an opening that passes the one of the parallel beams and the other of the parallel beams, and the optical element has a mirror and a quarter-wave plate that reflects the one of the parallel beams that has passed through the opening to make it the other of the pair of parallel beams, and the one of the parallel beams, the other of the parallel beams generated by reflection by the optical element, and the diffracted beam emitted by the diffraction element are incident on the region.

4. The magneto-optical trap device of claim 1, wherein the diffraction element is disposed between the region and the optical element that generates one of the pair of parallel beams, and has an opening that diffracts the one of the parallel beams incident thereon in the direction opposite to the incident side to emit the diffracted beam, and that passes the one of the parallel beams, and the one of the parallel beams that has passed through the opening, the other of the pair of parallel beams, and the diffracted beam emitted by the diffraction element are incident on the region.

5. The magneto-optical trap device of claim 1, wherein the diffraction element is disposed between the region and the optical element that generates one of the pair of parallel beams, and has an opening that diffracts the one of the parallel beams incident thereon in the direction opposite to the incident side to emit diffracted beam and passes the one of the parallel beams, and the optical element has a mirror and a quarter-wave plate that reflect the one of the parallel beams that has passed through the opening to generate the other of the pair of parallel beams, and the one of the parallel beams that has passed through the opening, the other of the pair of parallel beams generated by reflection by the optical element, and the diffracted beam emitted by the diffraction element are incident on the region.

6. A magneto-optical trap device as described in claim 1, comprising two of the diffraction elements, each of which is arranged at an opposing position between the region and the optical element that generates the pair of parallel beams, and which diffracts one and the other of the incident parallel beams to the opposite side from the incident side to emit diffracted beams, and has an opening that passes each of the pair of parallel beams, and into which the pair of parallel beams that have passed through the openings and the diffracted beams emitted by the two diffraction elements are incident.

7. The magneto-optical trap device according to claim 1, wherein said diffraction element emits n components of diffracted light, each having the same diffraction angle and diffraction efficiency, toward said region based on the incidence of at least one of said pair of parallel beams.

8. A magneto-optical trap device as described in claim 7, wherein the diffraction element, based on the incidence of at least one of the pair of parallel beams, emits the n-component diffracted beams that pass through the region and enter the region from directions that are n-fold symmetric with respect to a central optical axis parallel to the propagation direction.

9. A magneto-optical trap device as described in claim 1, wherein the optical element comprises: a first parallel light generating unit that generates a first parallel light of the pair of parallel light beams that travels along a first direction based on the laser light; and a second parallel light generating unit that generates a second parallel light of the pair of parallel light beams that travels along a second direction opposite to the first direction based on the laser light.

10. A magneto-optical trap device as described in claim 9, wherein the first collimated light generating unit and the second collimated light generating unit have the rotation direction of the circularly polarized light of the first collimated light and the rotation direction of the circularly polarized light of the second collimated light in the same direction.

11. A magneto-optical trap device as described in claim 10, wherein the second collimated light generating unit includes: a mirror that reflects the first collimated light to generate the second collimated light; and a wavelength plate that aligns the rotation direction of the circularly polarized light of the first collimated light with the rotation direction of the circularly polarized light of the second collimated light.

12. A magneto-optical trap device according to any one of claims 1, 7 and 8, wherein the diffraction element is constituted by a reflective diffraction element that emits the diffracted light on the same side as the incident side of at least one of the pair of parallel beams.

13. A magneto-optical trap device according to any one of claims 1, 7 and 8, wherein the diffraction element is configured as a transmission type diffraction element that outputs the diffracted light to the side opposite to the incident side of at least one of the pair of parallel beams.

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