Mirror pair block and quantum-entangled light source device

Abstract

To provide a mirror pair block capable of suppressing an increase in size of a device and reducing time and effort for adjustment, and a quantum entanglement light source device including the mirror pair block.SOLUTION: A mirror pair block according to an embodiment of the present invention is provided in an optical path of a quantum-entangled light source apparatus capable of generating quantum-entangled light using pump light. The mirror pair block includes a block body having a first inclined surface and a second inclined surface, a first mirror bonded to the first inclined surface, and a second mirror bonded to the second inclined surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mirror pair block and a quantum entanglement light source device. [Background technology]

[0002] In recent years, research into new information processing technologies based on the principles of quantum cryptography (hereinafter referred to as "quantum information processing technologies") has been actively conducted. Quantum entangled photon pairs are known as one of the basic technologies for realizing quantum information processing technologies. Quantum entangled photon pairs can be generated, for example, by spontaneous parametric down-conversion (SPDC) using a second-order nonlinear optical medium. When pump light is input into a second-order nonlinear optical medium, SPDC annihilates one pump photon and generates a signal photon and an idler photon. These two photons have a quantum mechanical correlation with respect to their polarization states and generation times. Therefore, these two photons are called a quantum-correlated photon pair. Quantum entangled photon pairs are generated by utilizing this process of generating quantum-correlated photon pairs.

[0003] For example, Patent Document 1 discloses that one of the vertically polarized light and horizontally polarized light obtained by a polarizing beam splitter is input directly to one end of a nonlinear element via a first polarization-maintaining fiber, and the other polarized light is propagated through a second polarization-maintaining fiber twisted by 90° relative to the first polarization-maintaining fiber, thereby inputting the polarized light whose polarization direction has been rotated by 90° to the other end of the nonlinear element, thereby obtaining quantum entangled photon pairs from the nonlinear element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-013348 Summary of the Invention [Problem to be solved by the invention]

[0005] It is conceivable to realize the function of the device described in Patent Document 1 by spatially arranging multiple optical components without using optical fibers. However, when spatially arranging multiple optical components, precise adjustment of the optical path length is required. Precise adjustment of the optical path length requires a dedicated adjustment mechanism for precisely setting the positions of the multiple optical components, which results in problems such as an increase in the size of the device and the labor required for adjustment. Therefore, it is desirable to provide a mirror pair block that can prevent the device from becoming larger and further reduce the labor required for adjustment, and a quantum entanglement light source device equipped with such a mirror pair block. [Means for solving the problem]

[0006] A mirror pair block according to one embodiment of the present invention is provided in the optical path of a quantum entanglement light source device capable of generating quantum entangled light using pump light. The mirror pair block includes a block body having a first inclined surface and a second inclined surface, a first mirror bonded to the first inclined surface, and a second mirror bonded to the second inclined surface.

[0007] A quantum entanglement light source device according to one embodiment of the present invention is a device capable of generating quantum entangled light using pump light. This quantum entanglement light source device includes a pump light generator, a polarization splitter, a polarization direction converter, a wavelength converter, and one or more mirror pair blocks. The pump light generator is capable of generating pump light. The polarization splitter is capable of generating first polarized light and second polarized light having different polarization directions by polarizing and splitting the pump light. The polarization direction converter is capable of converting the first polarized light into third polarized light whose polarization direction is parallel to that of the second polarized light. The wavelength converter has first and second end faces facing each other. When the third polarized light is incident on the first end face and the second polarized light is incident on the second end face, the wavelength converter is capable of emitting fourth polarized light, which is a signal wave and an idler wave, from the first end face and fifth polarized light, which is a signal wave and an idler wave, from the second end face. The first optical path from the polarization splitter to the first end face, including the first polarization direction conversion unit, is an optical path for the first polarized light and the third polarized light. The second optical path from the polarization splitter to the second end face is an optical path for the second polarized light. One or more mirror pair blocks are arranged in at least one of the first optical path and the second optical path so that the optical path lengths of the first optical path and the second optical path are equal to each other. The one or more mirror pair blocks have a block body having a first inclined surface and a second inclined surface, a first mirror bonded to the first inclined surface, and a second mirror bonded to the second inclined surface. [Effects of the Invention]

[0008] According to a mirror pair block and a quantum entanglement light source device according to an embodiment of the present invention, a mirror pair block having a block body with a first inclined surface and a second inclined surface, a first mirror bonded to the first inclined surface, and a second mirror bonded to the second inclined surface is arranged in the optical path of a quantum entanglement light source device capable of generating quantum entangled light using pump light. This eliminates the need to adjust the relative spatial positions of the first mirror and the second mirror. This eliminates the need for an adjustment mechanism for adjusting the relative spatial positions of the first mirror and the second mirror. This prevents the device from becoming too large and reduces the effort required for adjustment. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration example of a quantum entanglement light source device according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram showing the quantum entanglement light output process in the quantum entanglement light source device of FIG. [Figure 3] FIG. 3 is a diagram showing an example of input and output of polarized light to and from the wavelength conversion element of FIGS. [Figure 4] FIG. 4 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 5] FIG. 5 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. [Figure 6] FIG. 6 is a diagram illustrating a schematic configuration example of a quantum entanglement source device according to the second embodiment of the present invention. [Figure 7] FIG. 7 is a diagram showing the quantum entanglement light output process in the quantum entanglement light source device of FIG. [Figure 8] FIG. 8 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 9] FIG. 9 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. [Figure 10] FIG. 10 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 11]FIG. 11 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. [Figure 12] FIG. 12 is a diagram illustrating a schematic configuration example of a quantum entanglement light source device according to the third embodiment of the present invention. [Figure 13] FIG. 13 is a diagram showing the quantum entanglement light output process in the quantum entanglement light source device of FIG. [Figure 14] FIG. 14 is a diagram illustrating a schematic configuration example of a quantum entanglement source device according to the fourth embodiment of the present invention. [Figure 15] FIG. 15 is a diagram showing the quantum entanglement light output process in the quantum entanglement light source device of FIG. [Figure 16] FIG. 16 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 17] FIG. 17 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. [Figure 18] FIG. 18 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 19] FIG. 19 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. [Figure 20] FIG. 20 is a diagram illustrating a schematic configuration example of a quantum entanglement source device according to the fifth embodiment of the present invention. [Figure 21] FIG. 21 is a diagram showing the quantum entanglement light output process in the quantum entanglement light source device of FIG. [Figure 22] FIG. 22 is a perspective view showing an example of the configuration of the mirror pair block shown in FIGS. [Figure 23] FIG. 23 is a diagram illustrating an example of the internal configuration of the mirror pair block in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is one specific example of the present invention, and the present invention is not limited to the following embodiment. Furthermore, the present invention is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each drawing.

[0011] <1. Background> In recent years, research into new information processing technologies based on the principles of quantum cryptography (hereinafter referred to as "quantum information processing technologies") has been actively conducted. Quantum entangled photon pairs are known as one of the basic technologies for realizing quantum information processing technologies. Quantum entangled photon pairs can be generated, for example, by spontaneous parametric down-conversion (SPDC) using a second-order nonlinear optical medium. When pump light is input into a second-order nonlinear optical medium, SPDC annihilates one pump photon and generates a signal photon and an idler photon. These two photons have a quantum mechanical correlation with respect to their polarization states and generation times. Therefore, these two photons are called a quantum-correlated photon pair. Quantum entangled photon pairs are generated by utilizing this process of generating quantum-correlated photon pairs.

[0012] An apparatus capable of generating quantum entangled photon pairs is disclosed, for example, in Patent Document 1. Specifically, Patent Document 1 discloses that one of vertically polarized light and horizontally polarized light obtained by a polarizing beam splitter is input directly to one end of a nonlinear element via a first polarization-maintaining fiber, and the other polarized light is propagated through a second polarization-maintaining fiber twisted by 90° relative to the first polarization-maintaining fiber, thereby rotating the polarization direction by 90° and inputting the polarized light to the other end of the nonlinear element, thereby obtaining quantum entangled photon pairs from the nonlinear element.

[0013] Incidentally, it is conceivable to realize the function of the device described in Patent Document 1 by spatially arranging multiple optical components without using optical fibers. However, when spatially arranging multiple optical components, precise adjustment of the optical path length is required. Precise adjustment of the optical path length requires a dedicated adjustment mechanism for precisely setting the positions of the multiple optical components, which results in problems such as an increase in the size of the device and the effort required for adjustment. Therefore, after extensive research, the inventors of the present application have conceived an invention that can prevent the device from becoming larger and further reduce the effort required for adjustment.

[0014] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is one specific example of the present invention, and the present invention is not limited to the following embodiment. Furthermore, the present invention is not limited to the arrangement, dimensions, dimensional ratios, etc. of each component shown in each drawing.

[0015] 2. First Embodiment [composition] The configuration of a quantum entanglement light source device 100 according to a first embodiment of the present invention will be described. FIGS. 1 and 2 show a schematic configuration example of the quantum entanglement light source device 100. The quantum entanglement light source device 100 is a device capable of generating quantum entangled light L8 using pump light L1. As shown in FIGS. 1 and 2, the quantum entanglement light source device 100 includes, for example, a pump light generating unit 110, a wavelength conversion element 120, and a polarization beam splitter 130.

[0016] The quantum entanglement light source device 100 corresponds to a specific example of a "quantum entanglement light source device" according to an embodiment of the present invention. The pump light generating unit 110 corresponds to a specific example of a "pump light generating unit" according to an embodiment of the present invention. The wavelength conversion element 120 corresponds to a specific example of a "wavelength conversion unit" according to an embodiment of the present invention. The polarizing beam splitter 130 corresponds to a specific example of a "polarization separation unit" according to an embodiment of the present invention. The pump light L1 corresponds to a specific example of a "pump light" according to an embodiment of the present invention.

[0017] The pump light generating unit 110 is capable of generating pump light L1 having an optical frequency fp and an optical wavelength λp (=1 / fp) and inputting the pump light L1 to the polarizing beam splitter 130. The pump light generating unit 110 is configured to include, for example, a semiconductor laser element capable of generating laser light as the pump light L1. The pump light L1 is unpolarized light or linearly polarized light diagonally to the polarizing beam splitter 130.

[0018] The wavelength conversion element 120 is composed of a second-order nonlinear optical medium. For example, as shown in FIG. 3, the second-order nonlinear optical medium has a first end face S1 and a second end face S2 facing each other. An example of the second-order nonlinear optical medium is periodically poled lithium niobate (PPLN). When pump light having an optical frequency fp and an optical wavelength λp is input to both the first end face S1 and the second end face S2 of PPLN, one pump photon is annihilated due to SPDC, and a signal photon (signal wave) having an optical frequency fs and an optical wavelength λs (=1 / fs) and an idler photon (idler wave) having a frequency fi and an optical wavelength λs (=1 / fi) are simultaneously generated from both the first end face S1 and the second end face S2.

[0019] Here, the optical frequencies fs and fi satisfy fp = fs + fi. The optical wavelengths λs and λi satisfy 1 / λp = 1 / λs + 1 / λi. The optical wavelength λp is, for example, 0.755 μm. The optical wavelengths λs and λi are each, for example, 1.55 μm. The pump light incident on the first end face S1 is vertically polarized light and is linearly polarized light equivalent to the polarized light L4 shown in FIGS. 2 and 3. The pump light incident on the first end face S1 corresponds to a specific example of "third polarized light" according to an embodiment of the present invention. The pump light incident on the second end face S2 is vertically polarized light and is linearly polarized light equivalent to the polarized light L3 shown in FIGS. 2 and 3. The pump light incident on the second end face S2 corresponds to a specific example of "second polarized light" according to an embodiment of the present invention. The polarization direction of the pump light (polarized light L4) incident on the first end face S1 and the polarization direction of the pump light (polarized light L3) incident on the second end face S2 are the same.

[0020] The signal photons (signal waves) and idler photons (idler waves) output from the first end face S1 are vertically polarized light and linearly polarized light corresponding to polarized light L5 shown in FIGS. 2 and 3. Polarized light L5 corresponds to a specific example of "fourth polarized light" according to an embodiment of the present invention. The signal photons (signal waves) and idler photons (idler waves) output from the second end face S2 are vertically polarized light and linearly polarized light corresponding to polarized light L6 shown in FIGS. 2 and 3. Polarized light L6 corresponds to a specific example of "fifth polarized light" according to an embodiment of the present invention. The polarization direction of polarized light L5 output from the first end face S1 and the polarization direction of polarized light L6 output from the second end face S2 are identical to each other.

[0021] The polarizing beam splitter 130 is a cube-type beam splitter composed of two right-angle prisms. An optical thin film capable of transmitting s-polarized light and reflecting p-polarized light is deposited on the slant surface of one of the two right-angle prisms, and the slant surfaces of the two right-angle prisms are then joined together to obtain the cube-type beam splitter. The polarizing beam splitter 130 is positioned so that the pump light L1 is incident on the slant surface of the polarizing beam splitter 130 at an incident angle of 45°.

[0022] When pump light L1 is input, the polarized beam splitter 130 transmits a component of the input pump light L1 that vibrates in a direction intersecting the slope of the polarized beam splitter 130 (polarized light L2), and reflects a component of the input pump light L1 that vibrates parallel to the slope of the polarized beam splitter 130 (polarized light L3). Polarized light L2 is a horizontally polarized component contained in the pump light L1, and is emitted in the same direction as the traveling direction of the input pump light L1. Polarized light L3 is a vertically polarized component contained in the pump light L1, and is emitted in a direction at an angle of 90° to the traveling direction of the input pump light L1.

[0023] As shown in FIGS. 1 and 2, the quantum entanglement light source device 100 includes a first optical path P1 from the polarizing beam splitter 130 to the first end face S1, which includes a half-wave plate 140, a mirror pair block 150, and a lens 171. The first optical path P1 corresponds to a specific example of a "first optical path" according to an embodiment of the present invention. The first optical path P1 is an optical path along which the pump light L1, which is transmitted through the polarizing beam splitter 130 (polarized light L2), and the light (polarized light L4) obtained by converting the polarization direction of the polarized light L2 by 90° using the half-wave plate 140, propagate. The half-wave plate 140 corresponds to a specific example of a "first polarization direction conversion unit" according to an embodiment of the present invention. The mirror pair block 150 corresponds to a specific example of a "mirror pair block" or "first mirror pair block" according to an embodiment of the present invention.

[0024] The quantum entanglement light source device 100 further includes, for example, a mirror pair block 160, a reflecting mirror 182, and a lens 172 on a second optical path P2 from the polarizing beam splitter 130 to the second end face S2, as shown in FIGS. 1 and 2. The second optical path P2 corresponds to a specific example of a "second optical path" according to an embodiment of the present invention. The second optical path P2 is an optical path along which light (polarized light L3) reflected by the polarizing beam splitter 130 from the pump light L1 propagates. The mirror pair block 160 corresponds to a specific example of a "mirror pair block" or "first mirror pair block" according to an embodiment of the present invention.

[0025] The half-wave plate 140 is disposed on the first optical path P1 between the polarizing beam splitter 130 and the mirror pair block 150. The half-wave plate 140 is capable of converting the polarization direction of polarized light L2 by 90°. The half-wave plate 140 is capable of converting polarized light L2 into polarized light L4 that is parallel to the polarization direction of polarized light L3. The polarized light L4 is vertically polarized light. The mirror pair block 150 is disposed on the first optical path P1 between the half-wave plate 140 and a lens 171. The lens 171 is disposed between the mirror pair block 150 and the wavelength conversion element 120. The lens 171 is capable of directing polarized light L4 to the first end face S1.

[0026] The mirror pair block 160 is disposed on the second optical path P2 between the polarizing beam splitter 130 and the reflecting mirror 182. The reflecting mirror 182 is disposed between the mirror pair block 160 and the lens 172. The reflecting mirror 182 is capable of reflecting the polarized light L3 in a direction at an angle of 90° with respect to the traveling direction of the input polarized light L3 without changing the polarization direction of the polarized light L3. The lens 172 is disposed between the reflecting mirror 182 and the wavelength conversion element 120. The lens 172 is capable of making the polarized light L3 incident on the second end surface S2. The lenses 171 and 172 (lens group 170) are disposed so as to sandwich the wavelength conversion element 120. The wavelength separation mirror 181 and the reflecting mirror 182 (mirror group 180) may be provided separately from each other, or may be configured as an integrated unit like the mirror pair block 150.

[0027] The first optical path P1 corresponds to a counterclockwise optical path in the process (pump light input process) in which the pump light (polarized light L4) is input to the wavelength conversion element 120. The second optical path P2 corresponds to a clockwise optical path in the process (pump light input process) in which the pump light (polarized light L3) is input to the wavelength conversion element 120. The optical path length (counterclockwise optical path length) of the first optical path P1 and the optical path length (clockwise optical path length) of the second optical path P2 are equal to each other. The mirror pair blocks 150 and 160 are arranged (fine-tuned) so that the optical path lengths of the first optical path P1 and the second optical path P2 are equal to each other.

[0028] The mirror pair blocks 150 and 160 each have a common structure. Below, the mirror pair block 150 will be described as a representative of the mirror pair blocks 150 and 160. The mirror pair block 150 has a block main body 150A, as shown in FIGS. 4 and 5 , for example. The block main body 150A is formed, for example, by cutting a rectangular parallelepiped metal block. The block main body 150A is provided with a first inclined surface 153 and a second inclined surface 154. The block main body 150A corresponds to a specific example of a “first block main body” according to an embodiment of the present invention. The first inclined surface 153 corresponds to a specific example of a “first inclined surface” according to an embodiment of the present invention. The second inclined surface 154 corresponds to a specific example of a “second inclined surface” according to an embodiment of the present invention. The first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals of the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other.

[0029] The block main body 150A further includes a cavity 157 at a location corresponding to the first optical path P1 or the second optical path P2. The cavity 157 is U-shaped, with one end (opening 155) and the other end (opening 156) of the cavity 157 being provided on a side surface of the block main body 150A. The cavity 157 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 151 is bonded to a first inclined surface 153 of the block main body 150A. The reflecting mirror 151 corresponds to a specific example of a "first mirror" according to an embodiment of the present invention. The reflecting mirror 151 is capable of reflecting the polarized light L4, L5 in a direction at 90° relative to the traveling direction of the input polarized light L4, L5 without changing the polarization direction of the polarized light L4, L5. A reflecting mirror 152 is bonded to a second inclined surface 154 of the block main body 150A. Reflecting mirror 152 corresponds to a specific example of a "second mirror" according to an embodiment of the present invention. Reflecting mirror 152 is capable of reflecting polarized light L4, L5 in a direction at 90° to the traveling direction of input polarized light L4, L5 without changing the polarization direction of polarized light L4, L5. Reflecting mirrors 151, 152 (mirror pair block 150) are capable of folding back incident polarized light L4, L5 by reflection by reflecting mirrors 151, 152. In other words, reflecting mirrors 151, 152 are arranged in mirror image inversion positions.

[0030] In the mirror pair block 160, a reflecting mirror 161 is attached to the first inclined surface 153 instead of the reflecting mirror 151, and a reflecting mirror 162 is attached to the second inclined surface 154 instead of the reflecting mirror 152. The reflecting mirror 161 is capable of reflecting the polarized light L3, L6 in a direction at 90° to the traveling direction of the input polarized light L3, L6 without changing the polarization direction of the polarized light L3, L6. The reflecting mirror 162 is capable of reflecting the polarized light L3, L6 in a direction at 90° to the traveling direction of the input polarized light L3, L6 without changing the polarization direction of the polarized light L3, L6. The reflecting mirrors 161, 162 (mirror pair block 160) are capable of folding back the incident polarized light L3, L6 by reflection by the reflecting mirrors 161, 162. In other words, the reflecting mirrors 161, 162 are arranged in mirror image inversion positions.

[0031] An opening communicating with cavity 157 is provided in first inclined surface 153. Reflecting mirror 151 is exposed in the opening provided in first inclined surface 153. An opening communicating with cavity 157 is also provided in second inclined surface 154. Reflecting mirror 152 is exposed in the opening provided in second inclined surface 154. The opening provided in first inclined surface 153 corresponds to a specific example of a "first opening" according to an embodiment of the present invention. The opening provided in second inclined surface 154 corresponds to a specific example of a "second opening" according to an embodiment of the present invention. Cavity 157 is provided as an optical path through which incident polarized light (polarized light L4, polarized light L3) propagating through first optical path P1 or second optical path P2 can be folded back by reflection by reflecting mirror 151 and reflecting mirror 152.

[0032] Block main body 150A is further provided with a plurality of through holes 158, 159 used to fix block main body 150A to the housing of quantum entanglement light source device 100. Through hole 158 corresponds to a specific example of a "first through hole" according to an embodiment of the present invention. Through hole 159 corresponds to a specific example of a "second through hole" according to an embodiment of the present invention. The plurality of through holes 158 extend in a direction intersecting both first inclined surface 153 and second inclined surface 154 at an angle of 45°. The plurality of through holes 159 extend in a direction parallel to both first inclined surface 153 and second inclined surface 154.

[0033] Meanwhile, polarized light L5 emitted from the first end face S1 propagates along the first optical path P1, and light (polarized light L7) obtained by converting the polarization direction of polarized light L5 by 90° using the half-wave plate 140 propagates along the first optical path P1. Meanwhile, polarized light L6 emitted from the second end face S2 propagates along the second optical path P2. As shown in FIG. 2, the polarized beam splitter 130 is capable of generating quantum entangled light L8 by combining polarized light L7, whose polarization direction is orthogonal to that of polarized light L5, with polarized light L6. The quantum entanglement light source device 100 further includes a wavelength separation mirror 181, as shown in FIG. 2, that can output the quantum entangled light L8 generated by the polarized beam splitter 130 to the outside. The wavelength separation mirror 181 is capable of transmitting the pump light L1 and reflecting the quantum entangled light L8, as shown in FIGS. 1 and 2, for example.

[0034] The first optical path P1 corresponds to a clockwise optical path in the process in which quantum entangled light L8 is output to the outside (entangled light output process). The second optical path P2 corresponds to a counterclockwise optical path in the entangled light output process. That is, in this embodiment, the first optical path P1 not only serves as an optical path for propagating polarized light L2 and L4 counterclockwise, but also as an optical path for propagating polarized light L5 and L7 clockwise. The second optical path P2 not only serves as an optical path for propagating polarized light L3 clockwise, but also as an optical path for propagating polarized light L6 counterclockwise.

[0035] [effect] Next, the effects of the quantum entanglement light source device 100 according to this embodiment will be described.

[0036] In this embodiment, mirror pair block 150 is arranged in first optical path P1 of quantum entanglement light source device 100, and mirror pair block 160 is arranged in second optical path P2 of quantum entanglement light source device 100. This eliminates the need to adjust the relative spatial positions of reflecting mirrors 151 and 152 and reflecting mirrors 161 and 162. As a result, it is possible to omit an adjustment mechanism for adjusting the relative spatial positions of reflecting mirrors 151 and 152 and an adjustment mechanism for adjusting the relative spatial positions of reflecting mirrors 161 and 162. This prevents the device from becoming too large, and also reduces the effort required for adjustment.

[0037] In this embodiment, cavity 157 is provided in block main body 150A, openings communicating with cavity 157 are provided in first inclined surfaces 153 and 154, respectively, and reflecting mirror 151 is exposed in the opening provided in first inclined surface 153, and reflecting mirror 152 is exposed in the opening provided in second inclined surface 154. This allows quantum entanglement light source device 100 to be made smaller than when an optical path is configured without providing a cavity in block main body 150A.

[0038] In this embodiment, the block body 150A is provided with a plurality of through holes 158, 159 used when fixing the block body 150A to the housing of the quantum entanglement light source device 100. This allows the mirror pair blocks 150, 160 to be positioned by screwing or the like, thereby reducing the effort required for adjustment.

[0039] In this embodiment, the first inclined surface 153 and the second inclined surface 154 are provided in the block main body 150A at positions where the normals of the first inclined surface 153 and the second inclined surface 154 are orthogonal to each other. Furthermore, a cavity 157 is provided as an optical path through which polarized light L4 or polarized light L5 propagating along the first optical path P1 or the second optical path P2 can be reflected by the reflecting mirrors 151 and 152. This makes it possible to adjust the optical path length of the first optical path P1 or the second optical path P2 simply by adjusting the position of the mirror pair blocks 150 and 160 in a direction parallel to the traveling direction of the polarized light L4 or polarized light L5. As a result, the adjustment effort can be reduced.

[0040] 3. Second Embodiment [composition] Next, the configuration of a quantum entanglement light source device 200 according to a second embodiment of the present invention will be described. FIGS. 6 and 7 show a schematic configuration example of the quantum entanglement light source device 200. The quantum entanglement light source device 200 is a device capable of generating quantum entangled light L8 using pump light L1. As shown in FIGS. 6 and 7, the quantum entanglement light source device 200 includes, for example, a pump light generating unit 110, a wavelength conversion element 120, and a polarization beam splitter 210.

[0041] The polarizing beam splitter 210 is a beam splitter dedicated to the pump light L1 and is provided on the optical path of the pump light L1, and is not provided on the optical paths of the polarized lights L5, L6, and L7. The polarizing beam splitter 210 corresponds to a specific example of a "polarization separation unit" according to an embodiment of the present invention.

[0042] The polarizing beam splitter 210 is a cube-type beam splitter composed of two right-angle prisms. An optical thin film that transmits s-polarized light and reflects p-polarized light is deposited on the slant surface of one of the two right-angle prisms, and the slant surfaces of the two right-angle prisms are then joined together to obtain the cube-type beam splitter. This optical thin film has an optical design suited to the wavelength of the pump light L1. The polarizing beam splitter 210 is positioned so that the pump light L1 is incident on the slant surface of the polarizing beam splitter 210 at an incident angle of 45°.

[0043] When pump light L1 is input, the polarized beam splitter 210 transmits a component of the input pump light L1 that vibrates in a direction intersecting the slope of the polarized beam splitter 210 (polarized light L2), and reflects a component of the input pump light L1 that vibrates parallel to the slope of the polarized beam splitter 210 (polarized light L3). Polarized light L2 is a horizontally polarized component contained in the pump light L1, and is emitted in the same direction as the traveling direction of the input pump light L1. Polarized light L3 is a vertically polarized component contained in the pump light L1, and is emitted in a direction at an angle of 90° to the traveling direction of the input pump light L1.

[0044] As shown in FIGS. 6 and 7 , the quantum entanglement light source device 200 includes a half-wave plate 220, a wavelength separation mirror 242 included in a mirror pair block 240, a reflecting mirror 280, and a lens 171 on a first optical path P1 from a polarizing beam splitter 210 to a first end face S1. The first optical path P1 is an optical path along which the pump light L1 transmitted through the polarizing beam splitter 210 (polarized light L2) and the light obtained by converting the polarization direction of the polarized light L2 by 90° using the half-wave plate 220 (polarized light L4) propagate. The half-wave plate 220 corresponds to a specific example of a “first polarization direction conversion unit” according to an embodiment of the present invention. The mirror pair block 240 corresponds to a specific example of a “mirror pair block” or “second mirror pair block” according to an embodiment of the present invention.

[0045] The half-wave plate 220 is disposed on the first optical path P1 between the polarizing beam splitter 210 and the wavelength separation mirror 242. The half-wave plate 220 is capable of converting the polarization direction of polarized light L2 by 90°. The half-wave plate 220 is capable of converting polarized light L2 into polarized light L4 whose polarization direction is parallel to the polarization direction of polarized light L3. The half-wave plate 220 is a wavelength plate with an optical design suited to the wavelength of polarized light L2. The polarized light L4 is vertically polarized light. The wavelength separation mirror 242 is disposed on the first optical path P1 between the half-wave plate 220 and the reflecting mirror 280. The wavelength separation mirror 242 is capable of reflecting polarized light L4 in a direction at an angle of 90° relative to the propagation direction of the input polarized light L4 without changing the polarization direction of the polarized light L4. The wavelength separation mirror 242 is also capable of transmitting polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirror 280 is disposed between the wavelength separation mirror 242 and the lens 171. The reflecting mirror 280 is capable of reflecting the polarized light L4 in a direction at an angle of 90° relative to the direction of travel of the input polarized light L4 without changing the polarization direction of the polarized light L4. The reflecting mirror 280 is further capable of reflecting the polarized light L5 in a direction at an angle of 90° relative to the direction of travel of the input polarized light L5 without changing the polarization direction of the polarized light L5.

[0046] 6 and 7, the quantum entanglement light source device 100 further includes a mirror pair block 250, a wavelength separation mirror 272 included in the mirror pair block 270, and a lens 172 on a second optical path P2 from the polarizing beam splitter 210 to the second end face S2. The second optical path P2 is an optical path along which light (polarized light L3) reflected by the polarizing beam splitter 210 from the pump light L1 propagates. The mirror pair block 250 corresponds to a specific example of a "mirror pair block" or "first mirror pair block" according to an embodiment of the present invention. The mirror pair block 270 corresponds to a specific example of a "mirror pair block" or "second mirror pair block" according to an embodiment of the present invention.

[0047] The mirror pair block 250 is disposed between the polarizing beam splitter 210 and the wavelength separation mirror 272 on the second optical path P2. The mirror pair block 250 has the same structure as the mirror pair block 150. In the mirror pair block 250, a reflecting mirror 251 is bonded to the first inclined surface 153 instead of the reflecting mirror 151, and a reflecting mirror 252 is bonded to the second inclined surface 154 instead of the reflecting mirror 152. The reflecting mirror 251 is capable of reflecting the polarized light L3 in a direction at an angle of 90° relative to the traveling direction of the input polarized light L3 without changing the polarization direction of the polarized light L3. The reflecting mirrors 252 are capable of reflecting the polarized light L3 in a direction at an angle of 90° relative to the traveling direction of the input polarized light L3 without changing the polarization direction of the polarized light L3. The reflecting mirrors 251 and 252 (mirror pair block 250) are capable of folding back the incident polarized light L3 by reflection by the reflecting mirrors 251 and 252. That is, the reflecting mirrors 251 and 252 are arranged at positions where the mirror images are reversed.

[0048] The wavelength separation mirror 272 is disposed between the mirror pair block 250 and the lens 172. The wavelength separation mirror 272 is capable of reflecting polarized light L3 in a direction at 90° to the direction of propagation of the input polarized light L3 without changing the polarization direction of the polarized light L3. The wavelength separation mirror 272 is also capable of transmitting polarized light L6 without changing the polarization direction of the polarized light L6.

[0049] Quantum entanglement light source device 200 includes, for example, a half-wave plate 230 and a polarizing beam splitter 290, as shown in Figures 6 and 7. Half-wave plate 230 corresponds to a specific example of a "second polarization direction conversion unit" according to an embodiment of the present invention. Polarizing beam splitter 290 corresponds to a specific example of a "polarization synthesis unit" according to an embodiment of the present invention.

[0050] The half-wave plate 230 is disposed between the mirror pair block 240 and the polarizing beam splitter 290 on the third optical path P3 from the first end face S1 to the polarizing beam splitter 290. The half-wave plate 230 is capable of converting the polarization direction of polarized light L5 by 90°. The half-wave plate 230 is capable of converting polarized light L5 into polarized light L7 that is orthogonal to the polarization direction of polarized light L6. The half-wave plate 230 is a wave plate with an optical design suited to the wavelength of polarized light L5. Polarized light L7 is horizontally polarized light.

[0051] The polarizing beam splitter 290 is a dedicated beam splitter for quantum entangled light L8, and is provided on the optical path of the quantum entangled light L8; it is not provided on the optical paths of the polarized light L2, L3, and L4. The polarizing beam splitter 290 is a cube-type beam splitter composed of two right-angle prisms. The cube-type beam splitter is obtained by depositing an optical thin film that transmits s-polarized light and reflects p-polarized light on the slant surface of one of the two right-angle prisms, and then joining the slant surfaces of the two right-angle prisms together. This optical thin film has an optical design suited to the wavelength of the quantum entangled light L8. The polarizing beam splitter 290 is positioned so that the polarized light L6 and the polarized light L7 are incident on the slant surface of the polarizing beam splitter 290 at an incident angle of 45°. The polarized beam splitter 290 is further positioned so that the vibration direction (polarization direction) of the polarized light L6 is parallel to the inclined surface within the polarized beam splitter 290, and the vibration direction (polarization direction) of the polarized light L7 intersects with the inclined surface within the polarized beam splitter 290.

[0052] When polarized light L6 and L7 are input to polarized beam splitter 290, it transmits the input polarized light L7 and also reflects the input polarized light L6 at an inclined surface within polarized beam splitter 290, thereby combining polarized light L6 and polarized light L7 to generate and output quantum entangled light L8. Quantum entangled light L8 is a combined light of polarized light L6 and polarized light L7, and is unpolarized light.

[0053] 6 and 7, the quantum entanglement light source device 200 includes a lens 171, a reflecting mirror 280, a mirror pair block 240, and a half-wave plate 230 on a third optical path P3 from the first end face S1 to the polarizing beam splitter 290. The third optical path P3 corresponds to a specific example of a "third optical path" according to an embodiment of the present invention. The third optical path P3 is an optical path along which polarized light L5, which is a signal photon (signal wave) and an idler photon (idler wave), and light (polarized light L7) obtained by converting the polarization direction of polarized light L5 by 90° using the half-wave plate 230, propagate.

[0054] Quantum entanglement light source device 200 further includes lens 172 and mirror pair blocks 260, 270 on fourth optical path P4 from second end face S2 to polarizing beam splitter 290, as shown in, for example, FIGS. 6 and 7. Fourth optical path P4 corresponds to a specific example of a "fourth optical path" according to an embodiment of the present invention. Fourth optical path P4 is an optical path along which polarized light L6 propagates. Mirror pair block 260 corresponds to a specific example of a "mirror pair block" according to an embodiment of the present invention.

[0055] The mirror pair block 260 has the same structure as the mirror pair block 150. In the mirror pair block 260, a reflecting mirror 261 is attached to the first inclined surface 153 instead of the reflecting mirror 151, and a reflecting mirror 262 is attached to the second inclined surface 154 instead of the reflecting mirror 152. The reflecting mirror 261 is capable of reflecting polarized light L6 in a direction at an angle of 90° relative to the traveling direction of the input polarized light L6 without changing the polarization direction of the polarized light L6. The reflecting mirrors 262 are capable of reflecting polarized light L6 in a direction at an angle of 90° relative to the traveling direction of the input polarized light L6 without changing the polarization direction of the polarized light L6. The reflecting mirrors 261 and 262 (mirror pair block 260) are capable of reflecting the incident polarized light L6 back by reflection by the reflecting mirrors 261 and 262. In other words, the reflecting mirrors 261 and 262 are arranged in mirror image inversion positions.

[0056] The mirror pair block 270 has a block body 270A, for example, as shown in FIGS. 8 and 9 . The block body 270A is formed, for example, by cutting a rectangular parallelepiped metal block. The block body 270A is provided with a first inclined surface 273 and a second inclined surface 274. The block body 270A corresponds to a specific example of a "second block body" according to an embodiment of the present invention. The first inclined surface 273 corresponds to a specific example of a "third inclined surface" according to an embodiment of the present invention. The second inclined surface 274 corresponds to a specific example of a "fourth inclined surface" according to an embodiment of the present invention. The first inclined surface 273 and the second inclined surface 274 are positioned facing each other with a predetermined offset.

[0057] The block main body 270A further includes a cavity 277 at a location corresponding to the fourth optical path P4. The cavity 277 has a crank shape, with one end (opening 275) and the other end (opening 276) of the cavity 277 being provided on a side surface of the block main body 270A. The cavity 277 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 271 is bonded to the first inclined surface 273 of the block main body 270A. The reflecting mirror 271 corresponds to a specific example of a "third mirror" according to an embodiment of the present invention. The reflecting mirror 271 is capable of reflecting the polarized light L6 in a direction at 90° relative to the traveling direction of the input polarized light L6 without changing the polarization direction of the polarized light L6. A wavelength separation mirror 272 is bonded to the second inclined surface 274 of the block main body 270A. The wavelength separation mirror 272 corresponds to a specific example of a "fourth mirror" according to an embodiment of the present invention. The wavelength separation mirror 272 is capable of reflecting polarized light L3 in a direction at 90° to the direction of propagation of the input polarized light L3 without changing the polarization direction of the polarized light L3. The wavelength separation mirror 272 is also capable of transmitting polarized light L6 without changing the polarization direction of the polarized light L6. The reflecting mirror 271 and the wavelength separation mirror 272 are positioned facing each other with a predetermined offset.

[0058] An opening communicating with cavity 277 is provided in first inclined surface 273. Reflecting mirror 271 is exposed in the opening provided in first inclined surface 273. An opening communicating with cavity 277 is also provided in second inclined surface 274. Wavelength separation mirror 272 is exposed in the opening provided in second inclined surface 274. The opening provided in first inclined surface 273 corresponds to a specific example of a "third opening" according to an embodiment of the present invention. The opening provided in second inclined surface 274 corresponds to a specific example of a "fourth opening" according to an embodiment of the present invention. The cavity 277 is provided as an optical path that allows polarized light L6 to pass through the wavelength separation mirror 272 at an incident angle of 45°, and the polarized light L6 that has passed through the wavelength separation mirror 272 at an incident angle of 45° is reflected by the reflecting mirror 271 at an exit angle of 45°, thereby outputting the polarized light L6 in a direction perpendicular to the direction of travel of the polarized light L6 before it entered the wavelength separation mirror 272.

[0059] Block main body 270A is further provided with a plurality of through holes 278, 279 that are used when fixing block main body 270A to the housing of quantum entanglement light source device 200. The plurality of through holes 278 extend in a direction parallel to both first inclined surface 273 and second inclined surface 274. The plurality of through holes 279 extend in a direction intersecting both first inclined surface 273 and second inclined surface 274 at an angle of 45°.

[0060] The mirror pair block 240 has a block body 240A, for example, as shown in FIGS. 10 and 11 . The block body 240A is formed, for example, by cutting a rectangular parallelepiped metal block. The block body 240A is provided with a first inclined surface 243 and a second inclined surface 244. The block body 240A corresponds to a specific example of a "second block body" according to an embodiment of the present invention. The first inclined surface 243 corresponds to a specific example of a "third inclined surface" according to an embodiment of the present invention. The second inclined surface 244 corresponds to a specific example of a "fourth inclined surface" according to an embodiment of the present invention. The first inclined surface 243 and the second inclined surface 244 are positioned facing each other with a predetermined offset.

[0061] The block main body 240A further includes a cavity 247 at a location corresponding to the third optical path P3. The cavity 247 has a crank shape, with one end (opening 245) and the other end (opening 246) of the cavity 247 being provided on a side surface of the block main body 240A. The cavity 247 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 241 is bonded to the first inclined surface 243 of the block main body 240A. The reflecting mirror 241 corresponds to a specific example of a "third mirror" according to an embodiment of the present invention. The reflecting mirror 241 is capable of reflecting the polarized light L5 in a direction at an angle of 90° relative to the traveling direction of the input polarized light L5 without changing the polarization direction of the polarized light L5. A wavelength separation mirror 242 is bonded to the second inclined surface 244 of the block main body 240A. The wavelength separation mirror 242 corresponds to a specific example of a "fourth mirror" according to an embodiment of the present invention. The wavelength separation mirror 242 is capable of reflecting polarized light L4 in a direction at 90° to the direction of propagation of the input polarized light L4 without changing the polarization direction of the polarized light L4. The wavelength separation mirror 242 is also capable of transmitting polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirror 241 and the wavelength separation mirror 242 are positioned facing each other with a predetermined offset.

[0062] An opening communicating with cavity 247 is provided in first inclined surface 243. Reflecting mirror 241 is exposed in the opening provided in first inclined surface 243. An opening communicating with cavity 247 is also provided in second inclined surface 244. Wavelength separation mirror 242 is exposed in the opening provided in second inclined surface 244. The opening provided in first inclined surface 243 corresponds to a specific example of a "third opening" according to an embodiment of the present invention. The opening provided in second inclined surface 244 corresponds to a specific example of a "fourth opening" according to an embodiment of the present invention. The cavity 247 is provided as an optical path that allows polarized light L5 to pass through the wavelength separation mirror 242 at an incident angle of 45°, and the polarized light L5 that has passed through the wavelength separation mirror 242 at an incident angle of 45° is reflected by the reflecting mirror 241 at an exit angle of 45°, thereby outputting the polarized light L5 in a direction perpendicular to the direction of travel of the polarized light L5 before it enters the wavelength separation mirror 242.

[0063] Block main body 240A is further provided with a plurality of through holes 248, 249 that are used when fixing block main body 240A to the housing of quantum entanglement light source device 200. The plurality of through holes 248 extend in a direction parallel to both first inclined surface 243 and second inclined surface 244. The plurality of through holes 249 extend in a direction intersecting both first inclined surface 243 and second inclined surface 244 at an angle of 45°.

[0064] [effect] Next, the effects of the quantum entanglement light source device 200 according to this embodiment will be described.

[0065] In this embodiment, a mirror pair block 250 is arranged in the second optical path P2 of the quantum entanglement light source device 200. This eliminates the need to adjust the relative spatial positions of the reflecting mirrors 251 and 252. As a result, it is possible to omit an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirrors 251 and 252. This makes it possible to prevent the device from becoming too large, and further reduces the effort required for adjustment.

[0066] In this embodiment, a cavity 157 is provided in block body 150A of mirror pair block 250, openings communicating with cavity 157 are provided in first inclined surface 153 and second inclined surface 154 of mirror pair block 250, respectively, and reflective mirror 251 is exposed in the opening provided in first inclined surface 153 of mirror pair block 250, and reflective mirror 252 is exposed in the opening provided in second inclined surface 154 of mirror pair block 250. This allows quantum entanglement light source device 200 to be made smaller than when an optical path is configured without providing a cavity in block body 150A of mirror pair block 250.

[0067] In this embodiment, a plurality of through holes 158, 159 are provided in block body 150A of mirror pair block 250, which are used when fixing block body 150A of mirror pair block 250 to the housing of quantum entanglement light source device 200. This allows positioning of mirror pair block 150 of mirror pair block 250 by screwing or the like, thereby reducing the effort required for adjustment.

[0068] In this embodiment, in the block body 150A of the mirror pair block 250, the first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals to the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other. Furthermore, the cavity 157 of the mirror pair block 250 is provided as an optical path through which the polarized light L3 propagating along the second optical path P2 can be reflected by the reflecting mirrors 151 and 152. This makes it possible to adjust the optical path length of the second optical path P2 simply by adjusting the position of the mirror pair block 250 in a direction parallel to the traveling direction of the polarized light L3. As a result, the adjustment effort can be reduced.

[0069] In this embodiment, mirror pair block 240 is arranged on third optical path P3 of quantum entanglement light source device 200, and mirror pair block 270 is arranged on fourth optical path P4 of quantum entanglement light source device 200. This eliminates the need to adjust the relative spatial positions of reflecting mirrors 241 and 242 and reflecting mirrors 271 and 272. As a result, it is possible to omit an adjustment mechanism for adjusting the relative spatial positions of reflecting mirrors 241 and 242 and reflecting mirrors 271 and 272. This prevents the device from becoming too large, and also reduces the effort required for adjustment.

[0070] In this embodiment, a cavity 247 is provided in block body 240A of mirror pair block 240, and openings communicating with cavity 247 are provided in first inclined surface 243 and second inclined surface 244 of mirror pair block 240. Reflecting mirror 241 is exposed in the opening provided in first inclined surface 243 of mirror pair block 240, and reflecting mirror 242 is exposed in the opening provided in second inclined surface 244 of mirror pair block 240. This allows quantum entanglement light source device 200 to be made more compact than when an optical path is configured without providing a cavity in block body 240A of mirror pair block 240.

[0071] In this embodiment, the first inclined surface 243 and the second inclined surface 244 are positioned in opposing positions in the block body 240A of the mirror pair block 240, offset by a predetermined distance. Furthermore, the cavity 247 of the mirror pair block 250 is provided as an optical path through which polarized light L5 passes through the wavelength separation mirror 242 at an incident angle of 45°, and the polarized light L5 that passes through the wavelength separation mirror 242 at an incident angle of 45° is reflected by the reflecting mirror 241 at an exit angle of 45°, thereby outputting the polarized light L5 in a direction perpendicular to the traveling direction of the polarized light L5 before entering the wavelength separation mirror 242. This allows the optical path length of the third optical path P3 to be adjusted simply by adjusting the position of the mirror pair block 240 in a direction parallel to the traveling direction of the polarized light L5. As a result, the adjustment effort can be reduced.

[0072] In this embodiment, the first inclined surface 273 and the second inclined surface 274 are disposed in positions facing each other with a predetermined offset in the block body 270A of the mirror pair block 270. Furthermore, the cavity 277 of the mirror pair block 270 is provided as an optical path through which polarized light L6 passes through the wavelength separation mirror 272 at an incident angle of 45°, and the polarized light L6 that passes through the wavelength separation mirror 272 at an incident angle of 45° is reflected by the reflecting mirror 271 at an exit angle of 45°, thereby outputting the polarized light L6 in a direction perpendicular to the traveling direction of the polarized light L6 before entering the wavelength separation mirror 272. This allows the optical path length of the fourth optical path P4 to be adjusted simply by adjusting the position of the mirror pair block 270 in a direction parallel to the traveling direction of the polarized light L6. As a result, the adjustment effort can be reduced.

[0073] 4. Third Embodiment [composition] Next, the configuration of a quantum entanglement light source device 300 according to a third embodiment of the present invention will be described. Figures 12 and 13 show a schematic configuration example of the quantum entanglement light source device 300. The quantum entanglement light source device 300 is a device that can generate quantum entangled light L8 by using pump light L1. As shown in Figures 12 and 13, for example, the quantum entanglement light source device 300 has a configuration in which mirror pair blocks 310 and 320 are provided instead of the mirror pair block 240 and the reflecting mirror 280 in the quantum entanglement light source device 200.

[0074] The mirror pair block 310 is disposed between the half-wave plate 220 and the lens 171 on the second optical path P2. The mirror pair block 310 has the same structure as the mirror pair block 150. In the mirror pair block 310, a reflecting mirror 311 is bonded to the first inclined surface 153 instead of the reflecting mirror 151, and a wavelength separation mirror 312 is bonded to the second inclined surface 154 instead of the reflecting mirror 152. The reflecting mirror 311 is capable of reflecting polarized light L4 in a direction at 90° relative to the traveling direction of the input polarized light L4 without changing the polarization direction of the polarized light L4. The wavelength separation mirror 312 is capable of reflecting polarized light L4 in a direction at 90° relative to the traveling direction of the input polarized light L4 without changing the polarization direction of the polarized light L4. The wavelength separation mirror 312 is also capable of transmitting polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirrors 311 and 312 (mirror pair block 310) are capable of folding back the incident polarized light L4 by reflection by the reflecting mirrors 311 and 312. In other words, the reflecting mirrors 311 and 312 are arranged at positions where the mirror images are reversed.

[0075] The mirror pair block 320 is disposed between the wavelength separation mirror 312 and the half-wave plate 230 on the third optical path P3. The mirror pair block 320 has the same structure as the mirror pair block 150. In the mirror pair block 320, a reflecting mirror 321 is bonded to the first inclined surface 153 instead of the reflecting mirror 151, and a reflecting mirror 322 is bonded to the second inclined surface 154 instead of the reflecting mirror 152. The reflecting mirror 321 is capable of reflecting the polarized light L5 in a direction at 90° to the traveling direction of the input polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirror 322 is capable of reflecting the polarized light L5 in a direction at 90° to the traveling direction of the input polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirrors 321 and 322 (mirror pair block 320) are capable of reflecting the incident polarized light L5 back by reflection by the reflecting mirrors 321 and 322. That is, the reflecting mirrors 321 and 322 are arranged at positions where the mirror images are reversed.

[0076] [effect] Next, the effects of the quantum entanglement light source device 300 according to this embodiment will be described.

[0077] In this embodiment, mirror pair block 310 is arranged on first optical path P1 of quantum entanglement light source device 300, and mirror pair block 320 is arranged on third optical path P3 of quantum entanglement light source device 300. This eliminates the need to adjust the relative spatial positions of reflecting mirror 311 and wavelength separation mirror 312 and the relative spatial positions of reflecting mirrors 321 and 322. As a result, it is possible to omit an adjustment mechanism for adjusting the relative spatial positions of reflecting mirror 311 and wavelength separation mirror 312 and the relative spatial positions of reflecting mirrors 321 and 322. This makes it possible to prevent the device from becoming too large, and further reduces the effort required for adjustment.

[0078] In this embodiment, a cavity 157 is provided in the block body 150A of the mirror pair block 310, openings communicating with the cavity 157 are provided in the first inclined surface 153 and the second inclined surface 154 of the mirror pair block 310, and the reflecting mirror 311 is exposed in the opening provided in the first inclined surface 153 of the mirror pair block 310, and the wavelength separation mirror 312 is exposed in the opening provided in the second inclined surface 154 of the mirror pair block 310. This allows the quantum entanglement light source device 300 to be made more compact than when an optical path is configured without providing a cavity in the block body 150A of the mirror pair block 310.

[0079] In this embodiment, a cavity 157 is provided in the block body 150A of the mirror pair block 320, openings communicating with the cavity 157 are provided in the first inclined surface 153 and the second inclined surface 154 of the mirror pair block 320, respectively, and the reflecting mirror 251 is exposed in the opening provided in the first inclined surface 153 of the mirror pair block 320, and the reflecting mirror 252 is exposed in the opening provided in the second inclined surface 154 of the mirror pair block 320. This allows the quantum entanglement light source device 300 to be made more compact than when an optical path is configured without providing a cavity in the block body 150A of the mirror pair block 320.

[0080] In this embodiment, a plurality of through holes 158, 159 are provided in block body 150A of mirror pair block 310, which are used when fixing block body 150A of mirror pair block 310 to the housing of quantum entanglement light source device 300. This allows positioning of mirror pair block 150 of mirror pair block 310 by screwing or the like, thereby reducing the effort required for adjustment.

[0081] In this embodiment, a plurality of through holes 158, 159 are provided in block body 150A of mirror pair block 320, which are used when fixing block body 150A of mirror pair block 320 to the housing of quantum entanglement light source device 300. This allows positioning of mirror pair block 150 of mirror pair block 320 by screwing or the like, thereby reducing the effort required for adjustment.

[0082] In this embodiment, in the block body 150A of the mirror pair block 310, the first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals to the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other. Furthermore, the cavity 157 of the mirror pair block 310 is provided as an optical path along which the polarized light L4 propagating along the first optical path P1 can be reflected by the reflecting mirrors 151 and 152. This makes it possible to adjust the optical path length of the first optical path P1 simply by adjusting the position of the mirror pair block 310 in a direction parallel to the traveling direction of the polarized light L4. As a result, the adjustment effort can be reduced.

[0083] In this embodiment, in the block body 150A of the mirror pair block 320, the first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals to the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other. Furthermore, the cavity 157 of the mirror pair block 320 is provided as an optical path through which the polarized light L5 propagating along the third optical path P3 can be reflected by the reflecting mirrors 151 and 152. This makes it possible to adjust the optical path length of the third optical path P3 simply by adjusting the position of the mirror pair block 320 in a direction parallel to the traveling direction of the polarized light L5. As a result, the adjustment effort can be reduced.

[0084] 5. Fourth Embodiment [composition] Next, the configuration of a quantum entanglement light source device 400 according to a fourth embodiment of the present invention will be described. FIGS. 14 and 15 show a schematic configuration example of the quantum entanglement light source device 400. The quantum entanglement light source device 400 is a device capable of generating quantum entangled light L8 using pump light L1. As shown in FIGS. 14 and 15, the quantum entanglement light source device 400 is configured by replacing the half-wave plate 220 and the wavelength separation mirror 242 of the quantum entanglement light source device 200 with a mirror pair block 410, replacing the half-wave plate 230 and the reflecting mirror 241 with a mirror pair block 420, rotating the mirror pair block 250 by 90° about an axis parallel to the propagation direction of polarized light L3 as the rotation axis, and rotating the mirror pair block 260 by 90° about an axis parallel to the propagation direction of polarized light L6 as the rotation axis.

[0085] Quantum entanglement light source device 400 corresponds to a specific example of a "quantum entanglement light source device" according to an embodiment of the present invention. Mirror pair block 410 corresponds to a specific example of a "mirror pair block" and "first polarization direction conversion unit" according to an embodiment of the present invention. Mirror pair block 420 corresponds to a specific example of a "mirror pair block" and "second polarization direction conversion unit" according to an embodiment of the present invention. Mirror pair block 430 corresponds to a specific example of a "mirror pair block" and "first mirror pair block" according to an embodiment of the present invention.

[0086] The mirror pair block 410 is disposed between the polarizing beam splitter 210 and the reflecting mirror 280 on the first optical path P1. The mirror pair block 410 has a block body 410A, for example, as shown in FIGS. 16 and 17 . The block body 410A is formed, for example, by cutting a rectangular parallelepiped metal block. The block body 410A is provided with a first inclined surface 413 and a second inclined surface 414. The block body 410A corresponds to a specific example of a “fourth block body” according to an embodiment of the present invention. The first inclined surface 413 corresponds to a specific example of a “seventh inclined surface” according to an embodiment of the present invention. The second inclined surface 414 corresponds to a specific example of an “eighth inclined surface” according to an embodiment of the present invention. The first inclined surface 413 and the second inclined surface 414 are arranged in a twisted position corresponding to the position of the two flat plates when the two flat plates are positioned facing each other with a predetermined offset, and one of the two flat plates is rotated 90 degrees around a line segment that intersects the center of each flat plate at 45 degrees as the rotation axis.

[0087] The block main body 410A further includes a cavity 417 at locations corresponding to the first optical path P1 and the third optical path P3. The cavity 417 has a crank shape, with one end (opening 415) and the other end (opening 416) of the cavity 417 being provided on a side surface of the block main body 410A. The cavity 417 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 411 is bonded to the first inclined surface 413 of the block main body 410A. The reflecting mirror 411 corresponds to a specific example of a "seventh mirror" according to an embodiment of the present invention. The reflecting mirror 411 is capable of reflecting the polarized light L2 in a direction at 90° relative to the traveling direction of the input polarized light L2 without changing the polarization direction of the polarized light L2. A wavelength separation mirror 412 is bonded to the second inclined surface 414 of the block main body 410A. Wavelength separation mirror 412 corresponds to a specific example of an "eighth mirror" according to an embodiment of the present invention. Wavelength separation mirror 412 reflects polarized light L2 reflected by reflecting mirror 411 in a direction at an angle of 90° relative to both the direction of propagation of polarized light L2 when it is incident on reflecting mirror 411 and the direction of propagation of polarized light L2 when it is incident on wavelength separation mirror 412, thereby generating and outputting polarized light L4 that is orthogonal to the polarization direction of polarized light L2. In other words, when polarized light L2 is incident on mirror pair block 410 (reflecting mirror 411), reflecting mirror 411 and wavelength separation mirror 412 can output polarized light L4 that is orthogonal to the polarization direction of polarized light L2 in a direction at an angle of 90° relative to the direction of propagation of polarized light L2 when it is incident on mirror pair block 410 (reflecting mirror 411).

[0088] An opening communicating with cavity 417 is provided in first inclined surface 413. Reflecting mirror 411 is exposed in the opening. Second inclined surface 414 is also provided with an opening communicating with cavity 417. Wavelength separation mirror 412 is exposed in the opening. The opening in first inclined surface 413 corresponds to a specific example of a "seventh opening" according to an embodiment of the present invention. The opening in second inclined surface 414 corresponds to a specific example of an "eighth opening" according to an embodiment of the present invention. Cavity 417 is provided as an optical path through which polarized light L2 is reflected by reflecting mirror 411 and wavelength separation mirror 412, and polarized light L4 traveling in a direction perpendicular to the traveling direction of polarized light L2 can be output. Block body 410A is further provided with a plurality of through holes 418 that are used when fixing block body 410A to the housing of quantum entanglement light source device 400.

[0089] The mirror pair block 420 is disposed between the polarizing beam splitter 290 and the mirror pair block 420 (wavelength separation mirror 412) on the third optical path P3. The mirror pair block 420 has a block body 420A, for example, as shown in FIGS. 18 and 19 . The block body 420A is formed, for example, by cutting a rectangular parallelepiped metal block. The block body 420A is provided with a first inclined surface 423 and a second inclined surface 424. The block body 420A corresponds to a specific example of a “third block body” according to an embodiment of the present invention. The first inclined surface 423 corresponds to a specific example of a “fifth inclined surface” according to an embodiment of the present invention. The second inclined surface 424 corresponds to a specific example of a “sixth inclined surface” according to an embodiment of the present invention. The first inclined surface 423 and the second inclined surface 424 are arranged in a twisted position corresponding to the position of the two flat plates when the two flat plates are positioned facing each other with a predetermined offset, and one of the two flat plates is rotated 90 degrees around a line segment (hereinafter referred to as "line segment A") that intersects the center of each flat plate at 45 degrees as the rotation axis.

[0090] The block main body 420A further includes a cavity 427 at a position corresponding to the third optical path P3. The cavity 427 has a crank shape, with one end (opening 425) and the other end (opening 426) of the cavity 427 being provided on a side surface of the block main body 420A. The cavity 427 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 422 is bonded to the second inclined surface 424 of the block main body 420A. The reflecting mirror 422 corresponds to a specific example of a "sixth mirror" according to an embodiment of the present invention. The reflecting mirror 422 reflects the incident polarized light L5 in a direction that is 90° relative to the incident polarized light L5 and parallel to the line segment A, thereby generating and outputting polarized light L7 that is orthogonal to the polarization direction of the polarized light L5. A reflecting mirror 421 is bonded to the first inclined surface 423 of the block main body 420A. Reflecting mirror 421 corresponds to a specific example of a "fifth mirror" according to an embodiment of the present invention. Reflecting mirror 421 can reflect polarized light L7 obtained by reflection by reflecting mirror 422 in a direction at 90° to the traveling direction of input polarized light L7 without changing the polarization direction of polarized light L7. In other words, when polarized light L5 is incident on mirror pair block 420 (reflecting mirror 421), reflecting mirrors 421 and 422 can output polarized light L7 that is orthogonal to the polarization direction of polarized light L5 in a direction at 90° to the traveling direction of polarized light L5 when it is incident on mirror pair block 420 (reflecting mirror 421).

[0091] An opening communicating with cavity 427 is provided in first inclined surface 423. Reflecting mirror 421 is exposed in the opening. Second inclined surface 424 is also provided with an opening communicating with cavity 427. Reflecting mirror 422 is exposed in the opening in second inclined surface 424. The opening in first inclined surface 423 corresponds to a specific example of a "fifth opening" according to an embodiment of the present invention. The opening in second inclined surface 424 corresponds to a specific example of a "sixth opening" according to an embodiment of the present invention. Cavity 427 is provided as an optical path through which polarized light L5 is reflected by reflecting mirror 421 and wavelength separation mirror 422, and polarized light L7 traveling in a direction perpendicular to the traveling direction of polarized light L5 can be output. Block body 420A is further provided with a plurality of through holes 428 that are used when fixing block body 420A to the housing of quantum entanglement light source device 400.

[0092] [effect] Next, the effects of the quantum entanglement light source device 400 according to this embodiment will be described.

[0093] In this embodiment, a mirror pair block 430 is arranged in the second optical path P2 of the quantum entanglement light source device 400. This eliminates the need to adjust the relative spatial positions of the reflecting mirrors 431 and 432. As a result, an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirrors 431 and 432 can be omitted. This prevents the device from becoming too large, and also reduces the effort required for adjustment.

[0094] In this embodiment, a cavity 157 is provided in the block body 150A of the mirror pair block 430, openings communicating with the cavity 157 are provided in the first inclined surface 153 and the second inclined surface 154 of the mirror pair block 430, and a reflecting mirror 431 is exposed in the opening provided in the first inclined surface 153 of the mirror pair block 430, and a reflecting mirror 432 is exposed in the opening provided in the second inclined surface 154 of the mirror pair block 430. This allows the quantum entanglement light source device 400 to be made more compact than when an optical path is configured without providing a cavity in the block body 150A of the mirror pair block 430.

[0095] In this embodiment, a plurality of through holes 158, 159 are provided in block body 150A of mirror pair block 430, which are used when fixing block body 150A of mirror pair block 430 to the housing of quantum entanglement light source device 400. This allows positioning of mirror pair block 150 of mirror pair block 430 by screwing or the like, thereby reducing the effort required for adjustment.

[0096] In this embodiment, in the block body 150A of the mirror pair block 430, the first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals to the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other. Furthermore, the cavity 157 of the mirror pair block 430 is provided as an optical path along which the polarized light L3 propagating along the second optical path P2 can be reflected by the reflecting mirrors 431 and 432. This makes it possible to adjust the optical path length of the second optical path P2 simply by adjusting the position of the mirror pair block 430 in a direction parallel to the traveling direction of the polarized light L3. As a result, the adjustment effort can be reduced.

[0097] In this embodiment, a mirror pair block 410 is disposed in the first optical path P1 of the quantum entanglement light source device 400. This eliminates the need to adjust the relative spatial positions of the reflecting mirror 411 and the wavelength separation mirror 412. As a result, an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirror 411 and the wavelength separation mirror 412 can be omitted. This prevents the device from becoming larger, and also reduces the adjustment effort. In this embodiment, the mirror pair block 410 further functions as a substitute for the half-wave plate 220 and the wavelength separation mirror 242. This allows polarized light L4 that is orthogonal to the polarization direction of polarized light L2 to be obtained by reflection by the reflecting mirror 411 and the wavelength separation mirror 412 without using the half-wave plate 220. As a result, the optical path length of the first optical path P1 can be set with even greater precision.

[0098] In this embodiment, a cavity 417 is provided in block body 410A of mirror pair block 410, openings communicating with cavity 417 are provided in first inclined surface 413 and second inclined surface 414 of mirror pair block 410, and reflective mirror 411 is exposed in the opening provided in first inclined surface 413 of mirror pair block 410, while wavelength separation mirror 412 is exposed in the opening provided in second inclined surface 414 of mirror pair block 410. This allows quantum entanglement light source device 400 to be made smaller than when an optical path is configured without providing a cavity in block body 410A of mirror pair block 410.

[0099] In this embodiment, the first inclined surface 413 and the second inclined surface 414 of the block body 410A of the mirror pair block 410 are positioned at a twisted position corresponding to the position of the two flat plates when the two flat plates are arranged facing each other with a predetermined offset and one of the two flat plates is rotated 90° around a line segment intersecting the center of each plate at a 45° angle as the rotation axis. Furthermore, the cavity 417 of the mirror pair block 410 is provided as an optical path through which polarized light L2 is reflected by the reflecting mirror 411 and the wavelength separation mirror 412, and polarized light L4, which travels in a direction perpendicular to the direction of propagation of the polarized light L2, can be output. This allows the optical path length of the first optical path P1 to be adjusted simply by adjusting the position of the mirror pair block 410 in a direction parallel to the direction of propagation of the polarized light L2. As a result, the adjustment effort can be reduced.

[0100] In this embodiment, a mirror pair block 420 is disposed in the third optical path P3 of the quantum entanglement light source device 400. This eliminates the need to adjust the relative spatial positions of the reflecting mirrors 421 and 422. As a result, an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirrors 421 and 422 can be omitted. This prevents the device from becoming larger, and also reduces the adjustment effort. In this embodiment, the mirror pair block 420 also functions as a substitute for the half-wave plate 230 and the reflecting mirror 241. This allows polarized light L7, which is orthogonal to the polarization direction of polarized light L5, to be obtained by reflection by the reflecting mirrors 421 and 422 without using the half-wave plate 230. As a result, the optical path length of the third optical path P3 can be set with even greater precision.

[0101] In this embodiment, a cavity 427 is provided in a block body 420A of the mirror pair block 420, openings communicating with the cavity 427 are provided in the first inclined surface 423 and the second inclined surface 424 of the mirror pair block 420, respectively, and the reflecting mirror 421 is exposed in the opening provided in the first inclined surface 423 of the mirror pair block 420, and the reflecting mirror 422 is exposed in the opening provided in the second inclined surface 424 of the mirror pair block 420. This allows the quantum entanglement light source device 400 to be made smaller than when an optical path is configured without providing a cavity in the block body 420A of the mirror pair block 420.

[0102] In this embodiment, the first inclined surface 423 and the second inclined surface 424 of the block body 420A of the mirror pair block 420 are positioned at a twisted position corresponding to the position of the two flat plates when the two flat plates are arranged facing each other with a predetermined offset and one of the two flat plates is rotated 90° around a line segment intersecting the center of each plate at a 45° angle. Furthermore, the cavity 427 of the mirror pair block 420 is provided as an optical path through which polarized light L5 is reflected by the reflecting mirrors 421 and 422, and polarized light L7, which travels in a direction perpendicular to the direction of propagation of polarized light L5, can be output. This allows the optical path length of the third optical path P3 to be adjusted simply by adjusting the position of the mirror pair block 420 in a direction parallel to the direction of propagation of polarized light L7. As a result, the adjustment effort can be reduced.

[0103] 6. Fifth Embodiment [composition] Next, the configuration of a quantum entanglement light source device 500 according to a fifth embodiment of the present invention will be described. Figures 20 and 21 show a schematic configuration example of the quantum entanglement light source device 500. The quantum entanglement light source device 500 is a device that can generate quantum entangled light L8 by using pump light L1. As shown in Figures 20 and 21, for example, the quantum entanglement light source device 500 has a configuration in which mirror pair blocks 510 and 520 are provided instead of the mirror pair block 420 and the reflecting mirror 280 in the quantum entanglement light source device 400.

[0104] Quantum entanglement light source device 500 corresponds to a specific example of a "quantum entanglement light source device" according to an embodiment of the present invention. Mirror pair block 510 corresponds to a specific example of a "mirror pair block" and "first polarization direction conversion unit" according to an embodiment of the present invention. Mirror pair block 420 corresponds to a specific example of a "mirror pair block" and "second polarization direction conversion unit" according to an embodiment of the present invention. Mirror pair block 430 corresponds to a specific example of a "mirror pair block" and "first mirror pair block" according to an embodiment of the present invention.

[0105] The mirror pair block 510 is disposed between the lens 171 and the mirror pair block 520 on the third optical path P3. The mirror pair block 510 has the same structure as the mirror pair block 150. In the mirror pair block 510, a wavelength separation mirror 511 is bonded to the first inclined surface 153 instead of the reflecting mirror 151, and a reflecting mirror 512 is bonded to the second inclined surface 154 instead of the reflecting mirror 152. The wavelength separation mirror 511 is capable of reflecting polarized light L4 in a direction at 90° relative to the traveling direction of the input polarized light L4 without changing the polarization direction of the polarized light L5. The wavelength separation mirror 511 is also capable of transmitting polarized light L5 without changing the polarization direction of the polarized light L5. The reflecting mirror 512 is capable of reflecting polarized light L5, which has passed through the wavelength separation mirror 511, in a direction at 90° relative to the traveling direction of the input polarized light L5 without changing the polarization direction of the polarized light L5.

[0106] The mirror pair block 520 is disposed between the mirror pair block 510 and the polarizing beam splitter 290 on the third optical path P3. The mirror pair block 520 has a block body 520A, for example, as shown in FIGS. 22 and 23 . The block body 520A is formed, for example, by cutting a rectangular parallelepiped metal block. The block body 520A is provided with a first inclined surface 523 and a second inclined surface 524. The block body 520A corresponds to a specific example of a “third block body” according to an embodiment of the present invention. The first inclined surface 523 corresponds to a specific example of a “fifth inclined surface” according to an embodiment of the present invention. The second inclined surface 524 corresponds to a specific example of a “sixth inclined surface” according to an embodiment of the present invention. The first inclined surface 523 and the second inclined surface 524 are arranged in a twisted position corresponding to the position of the two flat plates when the two flat plates are positioned facing each other with a predetermined offset, and one of the two flat plates is rotated 90 degrees around a line segment (hereinafter referred to as "line segment B") that intersects the center of each flat plate at 45 degrees as the rotation axis.

[0107] The block main body 520A further includes a cavity 527 at a position corresponding to the third optical path P3. The cavity 527 has a crank shape, with one end (opening 525) and the other end (opening 526) of the cavity 527 being provided on a side surface of the block main body 520A. The cavity 527 corresponds to a specific example of a "cavity" according to an embodiment of the present invention. A reflecting mirror 521 is bonded to the first inclined surface 523 of the block main body 520A. The reflecting mirror 521 corresponds to a specific example of a "fifth mirror" according to an embodiment of the present invention. The reflecting mirror 521 reflects the incident polarized light L5 in a direction that is 90° relative to the incident polarized light L5 and parallel to the line segment B, thereby generating and outputting polarized light L7 that is orthogonal to the polarization direction of the polarized light L5. A reflecting mirror 522 is bonded to the second inclined surface 424 of the block main body 520A. The reflecting mirror 522 corresponds to a specific example of a "sixth mirror" according to an embodiment of the present invention. The reflecting mirror 522 is capable of reflecting polarized light L7 obtained by reflection by the reflecting mirror 521 in a direction at 90° to the traveling direction of the input polarized light L7 without changing the polarization direction of the polarized light L7. In other words, when polarized light L5 is incident on the mirror pair block 520 (reflecting mirror 521), the reflecting mirrors 521 and 522 are capable of outputting polarized light L7 that is orthogonal to the polarization direction of polarized light L5 in a direction at 90° to the traveling direction of polarized light L5 when it is incident on the mirror pair block 520 (reflecting mirror 521).

[0108] An opening communicating with cavity 527 is provided in first inclined surface 523. Reflecting mirror 521 is exposed in the opening. Second inclined surface 524 is also provided with an opening communicating with cavity 527. Reflecting mirror 522 is exposed in the opening in second inclined surface 524. The opening in first inclined surface 523 corresponds to a specific example of a "fifth opening" according to an embodiment of the present invention. The opening in second inclined surface 524 corresponds to a specific example of a "sixth opening" according to an embodiment of the present invention. Cavity 527 is provided as an optical path through which polarized light L5 is reflected by reflecting mirrors 521 and 522, and polarized light L7 traveling in a direction perpendicular to the traveling direction of polarized light L5 can be output. The block body 520A is further provided with a plurality of through holes 528 that are used when fixing the block body 520A to the housing of the quantum entanglement light source device 500.

[0109] [effect] Next, the effects of the quantum entanglement light source device 500 according to this embodiment will be described.

[0110] In this embodiment, the mirror pair block 430 is arranged in the second optical path P2 of the quantum entanglement light source device 500. This eliminates the need to adjust the relative spatial positions of the reflecting mirrors 431 and 432. As a result, it is possible to omit an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirrors 431 and 432. This makes it possible to prevent the device from becoming too large, and further reduces the effort required for adjustment.

[0111] In this embodiment, a cavity 157 is provided in the block body 150A of the mirror pair block 430, openings communicating with the cavity 157 are provided in the first inclined surface 153 and the second inclined surface 154 of the mirror pair block 430, and a reflecting mirror 431 is exposed in the opening provided in the first inclined surface 153 of the mirror pair block 430, and a reflecting mirror 432 is exposed in the opening provided in the second inclined surface 154 of the mirror pair block 430. This allows the quantum entanglement light source device 500 to be made smaller than when an optical path is configured without providing a cavity in the block body 150A of the mirror pair block 430.

[0112] In this embodiment, a plurality of through holes 158, 159 are provided in block body 150A of mirror pair block 430, which are used when fixing block body 150A of mirror pair block 430 to the housing of quantum entanglement light source device 500. This allows positioning of mirror pair block 150 of mirror pair block 430 by screwing or the like, thereby reducing the effort required for adjustment.

[0113] In this embodiment, in the block body 150A of the mirror pair block 430, the first inclined surface 153 and the second inclined surface 154 are provided at positions where the normals to the first inclined surface 153 and the second inclined surface 154 are perpendicular to each other. Furthermore, the cavity 157 of the mirror pair block 430 is provided as an optical path along which the polarized light L3 propagating along the second optical path P2 can be reflected by the reflecting mirrors 431 and 432. This makes it possible to adjust the optical path length of the second optical path P2 simply by adjusting the position of the mirror pair block 430 in a direction parallel to the traveling direction of the polarized light L3. As a result, the adjustment effort can be reduced.

[0114] In this embodiment, a mirror pair block 410 is disposed in the first optical path P1 of the quantum entanglement light source device 500. This eliminates the need to adjust the relative spatial positions of the reflecting mirror 411 and the wavelength separation mirror 412. As a result, an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirror 411 and the wavelength separation mirror 412 can be omitted. This prevents the device from becoming larger, and also reduces the adjustment effort. In this embodiment, the mirror pair block 410 further functions as a substitute for the half-wave plate 220 and the wavelength separation mirror 242. This allows polarized light L4 that is orthogonal to the polarization direction of polarized light L2 to be obtained by reflection by the reflecting mirror 411 and the wavelength separation mirror 412 without using the half-wave plate 220. As a result, the optical path length of the first optical path P1 can be set with even greater precision.

[0115] In this embodiment, a cavity 417 is provided in block body 410A of mirror pair block 410, openings communicating with cavity 417 are provided in first inclined surface 413 and second inclined surface 414 of mirror pair block 410, and reflective mirror 411 is exposed in the opening provided in first inclined surface 413 of mirror pair block 410, while wavelength separation mirror 412 is exposed in the opening provided in second inclined surface 414 of mirror pair block 410. This allows quantum entanglement light source device 500 to be made smaller than when an optical path is configured without providing a cavity in block body 410A of mirror pair block 410.

[0116] In this embodiment, the first inclined surface 413 and the second inclined surface 414 of the block body 410A of the mirror pair block 410 are positioned at a twisted position corresponding to the position of the two flat plates when the two flat plates are arranged facing each other with a predetermined offset and one of the two flat plates is rotated 90° around a line segment intersecting the center of each plate at a 45° angle as the rotation axis. Furthermore, the cavity 417 of the mirror pair block 410 is provided as an optical path through which polarized light L2 is reflected by the reflecting mirror 411 and the wavelength separation mirror 412, and polarized light L4, which travels in a direction perpendicular to the direction of propagation of the polarized light L2, can be output. This allows the optical path length of the first optical path P1 to be adjusted simply by adjusting the position of the mirror pair block 410 in a direction parallel to the direction of propagation of the polarized light L2. As a result, the adjustment effort can be reduced.

[0117] In this embodiment, a mirror pair block 520 is disposed in the third optical path P3 of the quantum entanglement light source device 500. This eliminates the need to adjust the relative spatial positions of the reflecting mirrors 521 and 522. As a result, an adjustment mechanism for adjusting the relative spatial positions of the reflecting mirrors 521 and 522 can be omitted. This prevents the device from becoming larger, and also reduces the adjustment effort. In this embodiment, the mirror pair blocks 510 and 520 further function as a substitute for the mirror pair block 420 and the reflecting mirror 280 (i.e., the half-wave plate 230 and the reflecting mirror 241). This allows polarized light L7, which is orthogonal to the polarization direction of polarized light L5, to be obtained by reflection by the mirror pair blocks 510 and 520 without using the half-wave plate 230. As a result, the optical path length of the third optical path P3 can be set with even greater precision.

[0118] In this embodiment, a cavity 527 is provided in block body 520A of mirror pair block 520, openings communicating with cavity 527 are provided in first inclined surface 523 and second inclined surface 524 of mirror pair block 520, respectively, and reflecting mirror 521 is exposed in the opening provided in first inclined surface 523 of mirror pair block 520, and reflecting mirror 522 is exposed in the opening provided in second inclined surface 524 of mirror pair block 520. This allows quantum entanglement light source device 500 to be made smaller than when an optical path is configured without providing a cavity in block body 520A of mirror pair block 520.

[0119] In this embodiment, the first inclined surface 523 and the second inclined surface 524 of the block body 520A of the mirror pair block 520 are positioned at a twisted position corresponding to the position of the two flat plates when the two flat plates are arranged facing each other with a predetermined offset and one of the two flat plates is rotated 90° around a line segment intersecting the center of each plate at a 45° angle. Furthermore, the cavity 527 of the mirror pair block 520 is provided as an optical path through which polarized light L5 is reflected by the reflecting mirrors 521 and 522, and polarized light L7 traveling in a direction perpendicular to the direction of propagation of the polarized light L5 can be output. This allows the optical path length of the third optical path P3 to be adjusted simply by adjusting the positions of the mirror pair blocks 510 and 520 in a direction parallel to the direction of propagation of the polarized light L7. As a result, the adjustment effort can be reduced.

[0120] Note that the effects described in this specification are merely examples. The effects of the present disclosure are not limited to the effects described in this specification. The present disclosure may have effects other than the effects described in this specification.

[0121] Furthermore, for example, the present disclosure can be configured as follows. <1> A mirror pair block (150, 160, 240, 250, 260, 270, 310, 320, 410, 420, 430, 440, 510, 520) provided in an optical path (P1 to P4) of a quantum entanglement light source device (100 to 500) capable of generating quantum entangled light (L8) using pump light (L1), a block body (150A, 240A, 270A, 410A, 520A) having a first inclined surface (153, 243, 273, 413, 523) and a second inclined surface (154, 244, 274, 414, 524); a first mirror (151, 271, 241, 411, 521) bonded to the first inclined surface (153, 243, 273, 413, 523); a second mirror (152, 242, 272, 412, 522) bonded to the second inclined surface (154, 244, 274, 414, 524); have Mirror vs. Block (150, 160, 240, 250, 260, 270, 310, 320, 410, 420, 430, 440, 510, 520). <2> The block main body (150A, 240A, 270A, 410A, 520A) is provided with cavities (157, 247, 277, 417, 527) at locations corresponding to the optical paths (P1 to P4), The first inclined surface (153, 243, 273, 413, 523) is provided with a first opening communicating with the cavity (157, 247, 277, 417, 527), The second inclined surface (154, 244, 274, 414, 524) is provided with a second opening communicating with the cavity (157, 247, 277, 417, 527), The first mirror (151, 241, 271, 411, 521) is exposed in the first opening, The second mirror (152, 242, 272, 412, 522) is exposed in the second opening. <1> Mirror pair blocks (150, 160, 240, 250, 260, 270, 310, 320, 410, 420, 430, 440, 510, 520) described above. <3> the block main body (150A, 240A, 270A, 410A, 520A) is provided with a plurality of through holes (158, 159, 248, 249, 278, 279, 418, 528) used to fix the block main body (150A, 240A, 270A, 410A, 520A) to a housing of the quantum entanglement light source device (100 to 500); The plurality of through holes (158, 159, 248, 249, 278, 279, 418, 528) are a plurality of first through holes (158, 249, 279, 418, 528) extending in a direction parallel to a first direction intersecting both the first inclined surface (153, 243, 273, 413, 523) and the second inclined surface (154, 244, 274, 414, 524) at 45°. 418, 528), and a plurality of second through holes (159, 248, 278) extending in a direction parallel to both the first inclined surface (153, 243, 273, 413, 523) and the second inclined surface (154, 244, 274, 414, 524), including at least the plurality of first through holes (158, 249, 279, 418, 528). <2> Mirror pair blocks (150, 160, 240, 250, 260, 270, 310, 320, 410, 420, 430, 440, 510, 520) described above. <4> In the block body (150A), The first inclined surface (153) and the second inclined surface (154) are provided at positions where the normals of the first inclined surface (153) and the second inclined surface (154) are perpendicular to each other, and where the incident polarized light (L3, L4, L5, L6) propagating through the optical paths (P1 to P4) can be turned back by reflection by the first mirror (151, 161, 251, 261, 311, 321, 431, 441, 511, 521) and the second mirror (152, 162, 252, 262, 312, 322, 432, 442, 512, 522). <1> Or <3> Mirror pair block (150, 160, 250, 260, 310, 320, 430, 440, 510, 520) according to any one of the above. <5> In the block body (240A, 270A), The first inclined surface (243, 273) and the second inclined surface (244, 274) are positioned to face each other with a predetermined offset, and are positioned so that incident polarized light (L5, L6) propagating through the optical path (P3, P4) passes through the second mirror (242, 272) at an incident angle of 45°, and the incident polarized light (L5, L6) transmitted through the second mirror (242, 272) at an incident angle of 45° is reflected by the first mirror (241, 271) at an exit angle of 45°, thereby outputting reflected polarized light (L5, L6) traveling in a direction perpendicular to the traveling direction of the incident polarized light (L5, L6). <1> Or <3> A mirror pair block (240, 270) according to any one of the preceding claims. <6> In the block body (410A, 520A), The first inclined surface (413, 523) and the second inclined surface (414, 524) are arranged at twisted positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated 90° around a line segment intersecting at 45° with respect to the center of each of the two flat plates as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset, and are also arranged at positions where incident polarized light (L2, L5) propagating through the optical path (P1, P3) is reflected by the first mirror (411, 521) and the second mirror (412, 522) and second reflected polarized light (L4, L7) propagating in a direction perpendicular to the propagation direction of the incident polarized light (L2, L5) can be output. <1> Or <3> A mirror pair block (410, 420, 520) according to any one of the above. <7> A quantum entanglement light source device (100-500) capable of generating quantum entangled light (L8) using pump light (L1), a pump light generating unit (110) capable of generating the pump light (L1); a polarization splitter (130, 210) capable of splitting the pump light (L1) by polarization to generate a first polarized light (L2) and a second polarized light (L3) having mutually different polarization directions; a first polarization direction conversion unit (140, 220, 410) capable of converting the first polarized light (L2) into third polarized light (L4) parallel to the polarization direction of the second polarized light (L3); a wavelength converting unit (120) having a first end face (S1) and a second end face (S2) facing each other, which is capable of emitting a fourth polarized light (L5) which is a signal wave and an idler wave from the first end face (S1) and emitting a fifth polarized light (L6) which is a signal wave and an idler wave from the second end face (S2) when the third polarized light (L4) is incident on the first end face (S1) and the second polarized light (L3) is incident on the second end face (S2); a first optical path (P1) from the polarization splitter (130, 210) to the first end surface (S1), which is an optical path of the first polarized light (L2) and the third polarized light (L4) and includes the first polarization direction converter (140, 220, 410); a second optical path (P2) of the second polarized light (L3) from the polarization splitter (130, 210) to the second end surface (S2); one or more first mirror pair blocks (150, 160, 250, 310, 430) arranged in at least one of the first optical path (P1) and the second optical path (P2) so that the optical path lengths of the first optical path (P1) and the second optical path (P2) are equal to each other; Equipped with The one or more first mirror pair blocks (150, 160, 250, 310, 430) a first block body (150A) having a first inclined surface (153) and a second inclined surface (154); a first mirror (151) bonded to the first inclined surface (153); a second mirror (152) bonded to the second inclined surface (154); have Quantum entanglement light source device (100~500). <8> The first block body (150A) is provided with a cavity (157) at a position corresponding to the first optical path (P1) or the second optical path (P2), The first inclined surface (153) is provided with a first opening communicating with the cavity (157), The second inclined surface (154) is provided with a second opening communicating with the cavity (157), The first mirror (151) is exposed in the first opening, The second mirror (152) is exposed in the second opening. <7> The quantum entanglement light source device (100 to 500) described in <9> the first block body (150A) is provided with a plurality of through holes (158, 159) used when fixing the first block body (150A) to a housing of the quantum entanglement light source device (100 to 500); The plurality of through holes (158, 159) includes at least the plurality of first through holes (158) extending in a direction parallel to a first direction intersecting both the first inclined surface (153) and the second inclined surface (154) at 45°, and the plurality of second through holes (159) extending in a direction parallel to both the first inclined surface (153) and the second inclined surface (154). <8> The quantum entanglement light source device (100 to 500) described in <10> the polarization separation unit (130, 210) is capable of generating the quantum entangled light (L8) by combining the fifth polarized light (L6) with sixth polarized light (L7), which is obtained by converting the fourth polarized light (L5) in the first polarization direction conversion unit (140) and has a polarization direction orthogonal to that of the fourth polarized light (L5); In the one or more first mirror pair blocks (150, 160, 250, 310), The first inclined surface (153) and the second inclined surface (154) are provided at positions where the normals of the first inclined surface (153) and the second inclined surface (154) are perpendicular to each other and where the third polarized light (L4) and the fourth polarized light (L5), or the second polarized light (L3) and the fifth polarized light (L6) can be reflected by the first mirror (151) and the second mirror (152). <7> Or <9> A quantum entanglement source device (100, 200, 300) according to any one of the above. <11> a second polarization direction conversion unit (230) capable of converting the fourth polarized light (L5) into sixth polarized light (L7) whose polarization direction is orthogonal to the polarization direction of the fourth polarized light (L5); a polarization combining unit (290) capable of combining the sixth polarized light (L7) and the fifth polarized light (L6) to generate the quantum entangled light (L8); a third optical path (P3) from the first end face (S1) to the polarization combining unit (290), which is an optical path of the fourth polarized light (L5) and the sixth polarized light (L7) and includes the second polarization direction conversion unit (230); a fourth optical path (P4) that is an optical path of the fifth polarized light (L6) and extends from the second end face (S2) to the polarization combining unit (290); one or more second mirror pair blocks (240, 270) arranged in at least one of the third optical path (P3) and the fourth optical path (P4) so ​​that the optical path lengths of the third optical path (P3) and the fourth optical path (P4) are equal to each other; Further provided with The one or more second mirror pair blocks (240, 270) a second block body (240A, 270A) having a third inclined surface (243, 273) and a fourth inclined surface (244, 274); a third mirror (241, 271) bonded to the third inclined surface (243, 273); a fourth mirror (242, 272) bonded to the fourth inclined surface (244, 274); have <7> A quantum entanglement source device (200, 300) according to claim 1. <12> The second block body (240A, 270A) is provided with a cavity (247, 277) at a position corresponding to the third optical path (P3) or the fourth optical path (P4), The third inclined surface (243, 273) is provided with a third opening communicating with the cavity (247, 277), The fourth inclined surface (244, 274) is provided with a fourth opening communicating with the cavity (247, 277), The third mirror (241, 271) is exposed in the third opening, The fourth mirror (242, 272) is exposed in the fourth opening. <11> A quantum entanglement source device (200, 300) according to claim 1. <13> In the one or more second mirror pair blocks (240, 270), The third inclined surface (243, 273) and the fourth inclined surface (244, 274) are positioned to face each other with a predetermined offset, and are arranged at positions where the fourth polarized light (L5) or the fifth polarized light (L6) can be transmitted through the fourth mirror (242, 272) at an incident angle of 45°, and the fourth polarized light (L5) or the fifth polarized light (L6) transmitted through the fourth mirror (242, 272) at an incident angle of 45° can be reflected by the third mirror (241, 271) at an exit angle of 45°, thereby outputting the fourth polarized light (L5) or the fifth polarized light (L6) in a direction perpendicular to the traveling direction of the fourth polarized light (L5) or the fifth polarized light (L6) before entering the fourth mirror (242, 272). <12> A quantum entanglement source device (200, 300) according to claim 1. <14> a second polarization direction conversion unit (420, 520) capable of converting the fourth polarized light (L5) into a sixth polarized light (L7) whose polarization direction is orthogonal to the polarization direction of the fourth polarized light (L5); a polarization combining unit (290) capable of combining the sixth polarized light (L7) and the fifth polarized light (L6) output from the third polarization direction conversion unit (440) to generate the quantum entangled light (L8); a third optical path (P3) from the first end face (S1) to the polarization combining unit (290), which is an optical path of the fourth polarized light (L5) and the sixth polarized light (L7) and includes the second polarization direction conversion unit (420, 520); a fourth optical path (P4) that is an optical path of the fifth polarized light (L6) and extends from the second end face (S2) to the polarization combining unit (290); Further provided with The second polarization direction conversion unit (420, 520) a third block body (420A, 520A) having a fifth inclined surface (423, 523) and a sixth inclined surface (424, 524); a fifth mirror (421, 521) bonded to the fifth inclined surface (423, 523); a sixth mirror (422, 522) bonded to the sixth inclined surface (424, 524); have <7> A quantum entanglement source device (400, 500) according to claim 1. <15> The third block body (420A, 520A) is provided with a cavity (427, 527) at a position corresponding to the third optical path (P3) or the fourth optical path (P4), The fifth inclined surface (423, 523) is provided with a fifth opening communicating with the cavity (427, 527), The sixth inclined surface (424, 524) is provided with a sixth opening communicating with the cavity (427, 527), The fifth mirror (421, 521) is exposed in the fifth opening, The sixth mirror (422, 522) is exposed in the sixth opening. <14> A quantum entanglement source device (400, 500) according to claim 1. <16> In the third block body (420A, 520A), The fifth inclined surface (423, 523) and the sixth inclined surface (424, 524) are arranged at twisted positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated by 90° around a line segment intersecting at 45° with respect to the center of each of the two flat plates as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset, and are arranged at positions where the fourth polarized light (L5) is reflected by the fifth mirror (421, 521) and the sixth mirror (422, 522), and the sixth polarized light (L7) traveling in a direction perpendicular to the traveling direction of the fourth polarized light (L5) can be output. <15> A quantum entanglement source device (400, 500) according to claim 1. <17> The first polarization direction conversion unit (410) a fourth block body (410A) having a seventh inclined surface (413) and an eighth inclined surface (414); a seventh mirror (411) bonded to the seventh inclined surface (413); an eighth mirror (412) bonded to the eighth inclined surface (414); have <7> A quantum entanglement source device (400, 500) according to claim 1. <18> The fourth block body (410A) is provided with a cavity (417) at a position corresponding to the first optical path (P1), The seventh inclined surface (413) is provided with a seventh opening communicating with the cavity (417), The eighth inclined surface (414) is provided with an eighth opening communicating with the cavity (417), The seventh mirror (411) is exposed in the seventh opening, The eighth mirror (412) is exposed in the eighth opening. <17> A quantum entanglement source device (400, 500) according to claim 1. <19> In the fourth block body (410A), The seventh inclined surface (413) and the eighth inclined surface (414) are provided at twist positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated by 90° around a line segment intersecting the center of each of the two flat plates at an angle of 45° as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset, and at positions where the first polarized light (L2) is reflected by the seventh mirror (411) and the eighth mirror (412), and the third polarized light (L4) traveling in a direction perpendicular to the traveling direction of the first polarized light (L2) and perpendicular to the polarization direction of the first polarized light (L2) can be output. <18> A quantum entanglement source device (400, 500) according to claim 1. [Explanation of symbols]

[0122] 100, 200, 300, 400, 500... quantum entanglement light source device, 110... pump light generator, 120... wavelength conversion element, 130, 210, 290... polarization beam splitter, 140, 220, 230... half-wave plate, 150, 160, 240, 250, 260, 270, 310, 320, 410, 420, 430, 440, 510 ,520...mirror pair block, 150A,270A,410A,520A...block body, 151,152,161,162,182,241,251,252,261,262,271,280,311,321,322,411,421,422,431,432,441,442,512,521,522...reflecting mirror, 153,154,243,244,273,274,413,414,523,524…Slope, 155,156,245,246,275,276,415,4 16,525,526...Opening, 157,247,277,417,527...Cavity, 158,159,248,249,278,279,418,528...Through hole, 1 70...lens group, 171, 172...lenses, 180...mirror group, 181, 242, 272, 312, 412, 511...wavelength separation mirrors, L1...pump light, L2, L3, L4, L5, L6, L7...polarized light, L8...entangled light, P1...first optical path, P2...second optical path, P3...third optical path, P4...fourth optical path, S1...first end face, S2...second end face.

Claims

1. A mirror pair block provided in an optical path of a quantum entanglement light source device capable of generating quantum entangled light by utilizing pump light, a block body having a first inclined surface and a second inclined surface; a first mirror bonded to the first inclined surface; a second mirror bonded to the second inclined surface; have Mirror vs. Block.

2. The block body has a cavity at a location corresponding to the optical path, The first inclined surface is provided with a first opening communicating with the cavity, The second inclined surface is provided with a second opening communicating with the cavity, the first mirror is exposed in the first opening, The second mirror is exposed in the second opening. The mirror pair block according to claim 1 .

3. the block body is provided with a plurality of through holes used when fixing the block body to a housing of the quantum entanglement light source device; The plurality of through holes include at least a plurality of first through holes extending in a direction parallel to a first direction intersecting both the first inclined surface and the second inclined surface at 45°, and a plurality of second through holes extending in a direction parallel to both the first inclined surface and the second inclined surface. The mirror pair block according to claim 2 .

4. In the block body, The first inclined surface and the second inclined surface are provided at positions where normals to the first inclined surface and the second inclined surface are orthogonal to each other and where incident polarized light propagating through the optical path can be folded back by reflection by the first mirror and the second mirror.

4. The mirror pair block according to claim 1.

5. In the block body, The first inclined surface and the second inclined surface are positioned to face each other with a predetermined offset, and are arranged at positions where incident polarized light propagating through the optical path can be transmitted through the second mirror at an incident angle of 45°, and the incident polarized light transmitted through the second mirror at an incident angle of 45° can be reflected by the first mirror at an exit angle of 45°, thereby outputting reflected polarized light that travels in a direction perpendicular to the traveling direction of the incident polarized light.

4. The mirror pair block according to claim 1.

6. In the block body, The first inclined surface and the second inclined surface are provided at twist positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated by 90° around a line segment intersecting the center of each of the two flat plates at an angle of 45° as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset between them, and at positions where incident polarized light propagating through the optical path is reflected by the first mirror and the second mirror, and second reflected polarized light that propagates in a direction perpendicular to the propagation direction of the incident polarized light can be output.

4. The mirror pair block according to claim 1.

7. A quantum entanglement light source device capable of generating quantum entangled light by using pump light, a pump light generating unit capable of generating the pump light; a polarization splitter capable of generating first polarized light and second polarized light having mutually different polarization directions by polarizing and splitting the pump light; a first polarization direction conversion unit capable of converting the first polarized light into third polarized light whose polarization direction is parallel to that of the second polarized light; a wavelength converting unit having a first end face and a second end face facing each other, the wavelength converting unit being capable of emitting fourth polarized light, which is a signal wave and an idler wave, from the first end face and emitting fifth polarized light, which is a signal wave and an idler wave, from the second end face when the third polarized light is incident on the first end face and the second polarized light is incident on the second end face; a first optical path from the polarization splitter to the first end face, the first optical path being an optical path for the first polarized light and the third polarized light and including the first polarization direction conversion unit; a second optical path for the second polarized light, the second optical path extending from the polarization splitter to the second end face; one or more first mirror pair blocks arranged in at least one of the first optical path and the second optical path so that the optical path lengths of the first optical path and the second optical path are equal to each other; Equipped with The one or more first mirror pair blocks include: a first block body having a first inclined surface and a second inclined surface; a first mirror bonded to the first inclined surface; a second mirror bonded to the second inclined surface; have Quantum entanglement light source.

8. a cavity is provided in the first block body at a location corresponding to the first optical path or the second optical path; The first inclined surface is provided with a first opening communicating with the cavity, The second inclined surface is provided with a second opening communicating with the cavity, the first mirror is exposed in the first opening, The second mirror is exposed in the second opening. The quantum entanglement source device according to claim 7 .

9. the first block body is provided with a plurality of through holes used when fixing the first block body to a housing of the quantum entanglement light source device; The plurality of through holes include at least a plurality of first through holes extending in a direction parallel to a first direction intersecting both the first inclined surface and the second inclined surface at 45°, and a plurality of second through holes extending in a direction parallel to both the first inclined surface and the second inclined surface. The quantum entanglement source device according to claim 8 .

10. the polarization separation unit is capable of generating the quantum entangled light by combining sixth polarized light, which is obtained by converting the fourth polarized light in the first polarization direction conversion unit, and the fifth polarized light, and the sixth polarized light is orthogonal to the polarization direction of the fourth polarized light; In the one or more first mirror pair blocks, The first inclined surface and the second inclined surface are provided at positions where normals of the first inclined surface and the second inclined surface are orthogonal to each other and where the third polarized light and the fourth polarized light, or the second polarized light and the fifth polarized light, can be folded back by reflection by the first mirror and the second mirror.

10. The quantum entanglement light source device according to claim 7.

11. a second polarization direction conversion unit capable of converting the fourth polarized light into sixth polarized light whose polarization direction is orthogonal to the polarization direction of the fourth polarized light; a polarization combining unit capable of combining the sixth polarized light and the fifth polarized light to generate the quantum entangled light; a third optical path from the first end face to the polarization combining unit, the third optical path being an optical path for the fourth polarized light and the sixth polarized light and including the second polarization direction conversion unit; a fourth optical path that is an optical path of the fifth polarized light and extends from the second end face to the polarization combining unit; one or more second mirror pair blocks arranged in at least one of the third optical path and the fourth optical path so that the optical path lengths of the third optical path and the fourth optical path are equal to each other; Further provided with The one or more second mirror pair blocks are a second block body having a third inclined surface and a fourth inclined surface; a third mirror bonded to the third inclined surface; a fourth mirror bonded to the fourth inclined surface; have The quantum entanglement source device according to claim 7 .

12. a cavity is provided in the second block body at a location corresponding to the third optical path or the fourth optical path; the third inclined surface is provided with a third opening communicating with the cavity; the fourth inclined surface is provided with a fourth opening communicating with the cavity; the third mirror is exposed in the third opening, The fourth mirror is exposed in the fourth opening. The quantum entanglement source device according to claim 11.

13. In the one or more second mirror pair blocks, The third inclined surface and the fourth inclined surface are positioned to face each other with a predetermined offset, and are provided at positions where the fourth polarized light or the fifth polarized light can be transmitted through the fourth mirror at an incident angle of 45°, and the fourth polarized light or the fifth polarized light transmitted through the fourth mirror at an incident angle of 45° can be reflected by the third mirror at an exit angle of 45°, thereby outputting the fourth polarized light or the fifth polarized light in a direction perpendicular to the traveling direction of the fourth polarized light or the fifth polarized light before being incident on the fourth mirror. The quantum entanglement source device according to claim 12.

14. a second polarization direction conversion unit capable of converting the fourth polarized light into sixth polarized light whose polarization direction is orthogonal to the polarization direction of the fourth polarized light; a polarization combining unit capable of combining the sixth polarized light and the fifth polarized light output from the third polarization direction converting unit to generate the quantum entangled light; a third optical path from the first end face to the polarization combining unit, the third optical path being an optical path for the fourth polarized light and the sixth polarized light and including the second polarization direction conversion unit; a fourth optical path that is an optical path of the fifth polarized light and is from the second end face to the polarization combining unit; Further provided with The second polarization direction conversion unit is a third block body having a fifth inclined surface and a sixth inclined surface; a fifth mirror bonded to the fifth inclined surface; a sixth mirror bonded to the sixth inclined surface; have The quantum entanglement source device according to claim 7 .

15. a cavity is provided in the third block body at a location corresponding to the third optical path or the fourth optical path; the fifth inclined surface is provided with a fifth opening communicating with the cavity, the sixth inclined surface is provided with a sixth opening communicating with the cavity, the fifth mirror is exposed in the fifth opening, The sixth mirror is exposed in the sixth opening. The quantum entanglement source device according to claim 14.

16. In the third block body, The fifth inclined surface and the sixth inclined surface are provided at twist positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated by 90° around a line segment intersecting the center of each of the two flat plates at an angle of 45° as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset between them, and at positions where the fourth polarized light is reflected by the fifth mirror and the sixth mirror, and the sixth polarized light propagating in a direction perpendicular to the propagation direction of the fourth polarized light and perpendicular to the polarization direction of the fourth polarized light can be output. The quantum entanglement source device according to claim 15.

17. The first polarization direction conversion unit is a fourth block body having a seventh inclined surface and an eighth inclined surface; a seventh mirror bonded to the seventh inclined surface; an eighth mirror bonded to the eighth inclined surface; have The quantum entanglement source device according to claim 7 .

18. a cavity is provided in the fourth block body at a location corresponding to the first optical path; a seventh opening communicating with the cavity is provided on the seventh inclined surface; an eighth opening communicating with the cavity is provided in the eighth inclined surface; the seventh mirror is exposed in the seventh opening, The eighth mirror is exposed in the eighth opening. The quantum entanglement source device according to claim 17.

19. In the fourth block body, The seventh inclined surface and the eighth inclined surface are provided at twist positions corresponding to the positions of the two flat plates when one of the two flat plates is rotated by 90° around a line segment intersecting the center of each flat plate at an angle of 45° as a rotation axis, with the two flat plates being positioned opposite each other with a predetermined offset between them, and at positions where the first polarized light is reflected by the seventh mirror and the eighth mirror, and the third polarized light that travels in a direction perpendicular to the traveling direction of the first polarized light and is perpendicular to the polarization direction of the first polarized light can be output. The quantum entanglement source device according to claim 18.

Images