Optical circuit, quantum computing device, and method for manufacturing an optical circuit

Abstract

An optical circuit (1) comprises: a first optical waveguide (11) that extends in a first direction and that contains diamond as a material; a plurality of second optical waveguides (12) that each contain diamond as a material and include a color center (30), and that are each connected to the first optical waveguide (11) and extend in a direction different from the first direction; and a third optical waveguide (21) that is formed of a material having a refractive index lower than that of diamond, and is connected to the first optical waveguide (11).

Description

Technical Field

[0001] The disclosed technology relates to an optical circuit and a method for manufacturing an optical circuit.

Background Art

[0002] As technologies related to optical circuits, the following are known. For example, a photonic integrated circuit including a substrate, a waveguide array integrated with the substrate, and a solid-state chip integrated on the substrate in alignment with the waveguide array is known. The solid-state chip includes an array of quantum emitters that emit single photons formed within the solid chip.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] [ A quantum computing device that utilizes a color center, which is a composite defect composed of a vacancy in which carbon atoms in a diamond single crystal are missing and an impurity atom adjacent thereto, can be expected to operate at high temperatures and achieve high integration, and in recent years, research and development has been active. In this type of quantum computing device, the color center functions as a quantum bit, and light is irradiated onto the color center for quantum bit operations. The quantum computing device may include an optical circuit including a first optical waveguide (nanobeam) made of diamond containing a color center and a second optical waveguide made of a material having a lower refractive index than the diamond connected to the first optical waveguide (nanobeam). The light emitted from the color center is guided to a photodetector through the second optical waveguide.

[0005] Color centers are formed by injecting impurities into a diamond substrate. However, it is difficult to form highly luminous color centers at desired locations within the diamond substrate. Therefore, the first optical waveguide (nanobeam) is fabricated by selecting highly luminous color centers from the diamond substrate and cutting out regions containing the selected color centers one by one from the diamond substrate. The second optical waveguide is fabricated separately from the first optical waveguide (nanobeam) and connected to the first optical waveguide (nanobeam). With the optical circuit fabricated by the above method, only one nanobeam (qubit) is connected to each optical waveguide. Therefore, the size of the optical circuit increases significantly with increasing bit count, making large-scale integration difficult.

[0006] The disclosed technology aims to enable large-scale integration in optical circuits, including color centers. [Means for solving the problem]

[0007] The optical circuit relating to the disclosed technology includes a first optical waveguide extending in a first direction and made of diamond, a plurality of second optical waveguides, each made of diamond and containing a color center, connected to the first optical waveguide and extending in a direction different from the first direction, and a third optical waveguide made of a material with a lower refractive index than diamond and connected to the first optical waveguide. [Effects of the Invention]

[0008] According to the disclosed technology, large-scale integration becomes possible in optical circuits, including color centers. [Brief explanation of the drawing]

[0009] [Figure 1A] This is a plan view showing an example of the configuration of an optical circuit according to an embodiment of the disclosed technology. [Figure 1B] This is a cross-sectional view along the line 1B-1B in Figure 1A. [Figure 2]This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 3A] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3B] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3C] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3D] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3E] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3F] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 3G] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 4] This is a plan view showing an example of the configuration of an optical circuit related to a comparative example. [Figure 5A] This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 5B] This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 5C] This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 6A] This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 6B] This is a plan view showing an example of the configuration of a first optical circuit according to an embodiment of the disclosed technology. [Figure 7A] This is a plan view showing an example of the configuration of an optical circuit according to an embodiment of the disclosed technology. [Figure 7B] This is a cross-sectional view along the line 7B-7B in Figure 7A. [Figure 8A] This is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 8B] It is a cross-sectional view taken along line 8B-8B in FIG. 8A. [Figure 9A] It is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 9B] It is a cross-sectional view taken along line 9B-9B in FIG. 9A. [Figure 10A] It is a plan view showing an example of a method for manufacturing an optical circuit according to an embodiment of the disclosed technology. [Figure 10B] It is a cross-sectional view taken along line 10B-10B in FIG. 10A. [Figure 11] It is a plan view showing an example of the configuration of a first optical circuit according to another embodiment of the disclosed technology. [Figure 12] It is a diagram showing an example of the configuration of a quantum computing device according to an embodiment of the disclosed technology. [Figure 13] It is a diagram showing an example of the configuration of a quantum computing device according to an embodiment of the disclosed technology.

Mode for Carrying Out the Invention

[0010] Hereinafter, an example of an embodiment of the disclosed technology will be described with reference to the drawings. In each of the drawings, the same or equivalent components and parts are denoted by the same reference numerals, and redundant descriptions are omitted.

[0011] [First Embodiment] FIG. 1A is a plan view showing an example of the configuration of an optical circuit 1 according to an embodiment of the disclosed technology. FIG. 1B is a cross-sectional view taken along line 1B-1B in FIG. 1A. The optical circuit 1 has a substrate 40, and a first optical circuit 10 and a second optical circuit 20 provided on the substrate 40. The substrate 40 is not particularly limited, and for example, a silicon substrate can be used. The silicon substrate may be one having a silicon oxide film (such as a SiO2 film) provided on the surface of the silicon layer.

[0012] The first optical circuit 10 has a first optical waveguide 11 and a plurality of second optical waveguides 12. The first optical waveguide 11 and the second optical waveguides 12 are integrally configured. The first optical waveguide 11 is a straight optical waveguide made of diamond. The first optical waveguide 11 may be bent or curved. Each of the plurality of second optical waveguides 12 is made of diamond containing a color center 30. The color center 30 is a composite defect composed of a vacancy in the diamond crystal where a carbon atom is missing and an impurity atom adjacent to the vacancy. The impurity may be, for example, nitrogen, germanium, silicon, tin, or lead. The color center 30 functions as a qubit in a quantum computing device configured including the optical circuit 1.

[0013] Each of the multiple second optical waveguides 12 contains a single color center 30. That is, no single second optical waveguide 12 contains more than one color center. This makes it possible to correspond one second optical waveguide 12 to one qubit. Furthermore, the first optical waveguide 11 does not contain a color center. If a color center is present in the first optical waveguide 11, the light emitted from that color center becomes noise. By not including a color center in the first optical waveguide 11, the noise component can be eliminated.

[0014] The second optical waveguide 12 is connected to multiple locations along the extension direction of the first optical waveguide 11 and extends in a direction intersecting the extension direction of the first optical waveguide 11. The multiple second optical waveguides 12 are connected to both sides of each other's opposing edges along the extension direction of the first optical waveguide 11. Light emitted from the color center 30 is guided to the first optical waveguide 11 via the second optical waveguides 12. In the first optical circuit 10, the second optical waveguides 12 constitute a nanobeam and function as a bus line integrating the first optical waveguide 11 and multiple nanobeams.

[0015] Each of the multiple second optical waveguides 12 is connected to the first optical waveguide 11 in such a way that the direction of propagation of the light emitted from the color center 30 in the first optical waveguide 11 is the same for all of them. That is, the direction of propagation of the light emitted from the color center 30 in each of the second optical waveguides 12 has the same directional component as the direction of propagation of the light in the first optical waveguide 11. For example, as shown in Figure 2, the direction of propagation D2 of the light emitted from the color center 30 in the second optical waveguides 12a and 12b has the same directional component D2x as the direction of propagation D1 of the light in the first optical waveguide 11. Note that the width of the first optical waveguide 11 and the second optical waveguides 12 may be greater than the height in order to propagate the polarization component (TE mode) in the plane direction. Furthermore, in order to propagate polarization components (TM modes) in a direction perpendicular to the plane direction, the width of the first optical waveguide 11 and the second optical waveguide 12 in the plane direction may be smaller than the height of these optical waveguides.

[0016] The second optical circuit 20 has a third optical waveguide 21 connected to the extension end of the first optical waveguide 11. The third optical waveguide 21 has a first portion 22 connected to one end of the first optical waveguide 11 in the extension direction, and a second portion 23 connected to the other end of the first optical waveguide 11 in the extension direction. As shown in Figure 1B, the optical circuit 1 has a structure in which the first optical waveguide 11 and the third optical waveguide 21 are stacked. A cavity 25 is formed in the region between the first portion 22 and the second portion 23 of the third optical waveguide 21, and between the first optical waveguide 11 and the substrate 40. The third optical waveguide 21 is made of a material with a refractive index lower than that of diamond. As the material for the third optical waveguide 21, for example, sapphire (Al2O3), silicon oxide (SiO2, etc.), silicon nitride (SiN, etc.), or silicon carbide (SiC, etc.) can be used. Light emitted from the color center 30 is guided to the third optical waveguide 21 via the second optical waveguide 12 and the first optical waveguide 11. By making the third optical waveguide 21 a material with a lower refractive index than diamond, which is the material of the first optical circuit 10, reflection of light at the interface between the first optical waveguide 11 and the third optical waveguide 21 can be suppressed, thereby suppressing optical loss. The third optical waveguide 21 may, for example, guide the light emitted from the color center 30 to a photodetector (not shown).

[0017] The method for manufacturing the optical circuit 1 according to this embodiment will be described below. Figures 3A to 3G are plan views showing an example of the method for manufacturing the optical circuit 1.

[0018] First, a diamond substrate 50, which will be the material for the first optical circuit 10, is prepared (Figure 3A). Next, a resist 51 is formed on the diamond substrate 50 to cover the planned location for the formation of the first optical waveguide 11 (Figure 3B).

[0019] Next, impurity atoms are implanted into the diamond substrate 50 via the resist 51 by ion implantation. The impurities may be, for example, nitrogen, germanium, silicon, tin, or lead. Multiple color centers 30 are formed in the diamond substrate 50 by impurity implantation. Color centers are not formed in the portion of the diamond substrate 50 covered with the resist 51, i.e., in the location where the first optical waveguide 11 is to be formed. After impurity implantation, the resist 51 is removed (Figure 3C).

[0020] The luminescence characteristics of the multiple color centers 30 formed on the diamond substrate 50 are not uniform, with some having good luminescence characteristics and others not. Therefore, from among the multiple color centers 30 formed on the diamond substrate 50, those that satisfy predetermined conditions regarding luminescence characteristics are selected. For example, by irradiating the diamond substrate 50 with laser light, color centers 30 whose emitted light intensity is above a threshold may be selected. In other words, color centers 30 exhibiting good luminescence characteristics are picked out.

[0021] Next, taking into account the selection results of the color centers 30, the pattern 10P of the first optical circuit 10 to be cut from the diamond substrate 50 is formulated (Figure 3D). That is, the region of the diamond substrate 50 that does not contain the color centers is defined as the region of the first optical waveguide 11. Furthermore, the layout of the multiple second optical waveguides 12 is formulated such that each of the multiple second optical waveguides 12 contains a color center 30 that satisfies predetermined conditions, is connected to multiple locations along the extension direction of the first optical waveguide 11, and has a pattern that extends in a direction intersecting the extension direction of the first optical waveguide 11.

[0022] Next, the diamond substrate 50 is etched to cut out a first optical circuit 10 having the pattern 10P formulated in the above process (Figure 3E). That is, the first optical circuit 10 includes a first optical waveguide 11 that does not include color centers. The first optical circuit 10 also includes a plurality of second optical waveguides 12, each containing a color center 30 that satisfies predetermined conditions regarding emission characteristics, connected to a plurality of locations along the extension direction of the first optical waveguide 11, and extending in a direction intersecting the extension direction of the first optical waveguide 11.

[0023] Next, a second optical circuit 20 is formed separately from the first optical circuit 10. Specifically, a substrate 40 is prepared having a low refractive index material layer on its surface, which has a lower refractive index than diamond. The low refractive index material layer may include, for example, sapphire (Al2O3), silicon oxide (SiO2, etc.), silicon nitride (SiN, etc.), or silicon carbide (SiC, etc.). Next, the second optical circuit 20, which includes a third optical waveguide 21, is formed on the substrate 40 by patterning the low refractive index material layer by etching or the like (Figure 3F).

[0024] Next, the first optical circuit 10 is mounted on top of the second optical circuit 20. The first optical circuit 10 and the second optical circuit 20 are coupled by intermolecular forces. The first portion 22 of the third optical waveguide 21 is connected to one end of the first optical waveguide 11, and the second portion 23 of the third optical waveguide 21 is connected to the other end of the first optical waveguide 11 (Figure 3G).

[0025] Here, Figure 4 is a plan view showing an example of the configuration of optical circuit 1X according to the comparative example. Optical circuit 1X according to the comparative example has a plurality of optical waveguides 61 (nanobeams) made of diamond material containing color centers 60, and a plurality of optical waveguides 62 provided corresponding to each of the optical waveguides 61 and made of a material with a lower refractive index than diamond. As described above, color centers are formed by injecting impurities into a diamond substrate. However, it is difficult to form color centers with high luminescence efficiency at desired positions within the diamond substrate. For this reason, the first optical waveguide (nanobeam) is fabricated by selecting color centers with high luminescence efficiency from the diamond substrate and cutting out regions containing the selected color centers one by one from the diamond substrate. Optical waveguides 62 are fabricated separately from optical waveguides 61 (nanobeams) and connected to optical waveguides 61 (nanobeams). According to optical circuit 1X according to the comparative example, only one nanobeam (qubit) is connected to each optical waveguide. For this reason, the size of the optical circuit increases significantly with increasing the number of bits, making large-scale integration difficult.

[0026] On the other hand, the optical circuit 1 according to an embodiment of the disclosed technology has a first optical waveguide 11 made of diamond. The optical circuit 1 also has a plurality of second optical waveguides 12, each containing a color center 30 and made of diamond, connected to a plurality of locations along the extension direction of the first optical waveguide and extending in a direction intersecting the extension direction of the first optical waveguide 11. The optical circuit 1 also has a third optical waveguide 21 made of a material with a lower refractive index than diamond and connected to the end of the first optical waveguide 11 in the extension direction.

[0027] According to the optical circuit 1 of the disclosed technology, since multiple nanobeams (qubits) are connected to a single optical waveguide, the expansion of the optical circuit size associated with an increase in the number of bits can be suppressed, enabling large-scale integration.

[0028] In the above description, the configuration of the first optical circuit 10 is illustrated in which a plurality of second optical waveguides 12 are connected to both sides of the first optical waveguide 11 along the extension direction, opposite to each other. However, the configuration is not limited to this example. Figures 5A, 5B, and 5C are plan views showing an example of a modified configuration of the first optical circuit 10. As shown in Figures 5A to 5C, in the first optical circuit 10, the plurality of second optical waveguides 12 may be connected to only one side of the first optical waveguide 11 along the extension direction, opposite to each other. Furthermore, the angle θ between the first optical waveguide 11 and the second optical waveguide 12 can be any size. Figure 5A is an example where the angle θ is relatively large, and Figure 5B is an example where the angle θ is relatively small. From the viewpoint of reducing optical loss at the connection between the first optical waveguide 11 and the second optical waveguide 12, a smaller angle θ is preferable. Furthermore, as shown in Figure 5C, the angle θ may be non-uniform. If the optical loss at the connection between the first optical waveguide 11 and the second optical waveguide 12 can be sufficiently reduced, it is preferable to adjust the angle θ appropriately to bring more color centers 30 into the first optical circuit 10.

[0029] Figure 6A is a plan view showing a configuration in which the second optical waveguides 12a and 12b are connected to opposite sides of the first optical waveguide 11, and the connection points of the second optical waveguides 12a and 12b with the first optical waveguide 11 are close together. In this case, some of the light emitted from the color center 30 contained in the second optical waveguide 12a propagates to the second optical waveguide 12b, resulting in loss. As shown in Figure 6B, by having tapered sections 13 in which the width gradually decreases toward the connection point with the first optical waveguide 11, the propagation of light emitted from the color center 30 of the second optical waveguide 12a to the second optical waveguide 12b can be avoided. This is because the tapered section 13 changes the coupling characteristics of the light in the second optical waveguide 12b. Furthermore, the pattern of the first optical circuit 10 may be designed so that the connection points of the second optical waveguides 12a and 12b with the first optical waveguide 11 are not in close proximity.

[0030] Figure 7A is a plan view showing an example of the configuration of the modified optical circuit 1, and Figure 7B is a cross-sectional view along the line 7B-7B in Figure 7. The third optical waveguide 21 includes a first portion 22 connected to one end of the first optical waveguide 11 in the extension direction, and a second portion 23 connected to the other end of the first optical waveguide 11 in the extension direction. The optical circuit 1 according to this modified example has a support portion 70 between the first portion 22 and the second portion 23 of the third optical waveguide 21 that supports the first optical circuit 10 (i.e., the first optical waveguide 11 and the second optical waveguide 12). The support portion 70 is provided between the first optical circuit 10 and the substrate 40 and supports the first optical circuit 10 from the bottom side. By providing the support portion 70, the load-bearing capacity of the first optical circuit 10 can be increased.

[0031] Figures 8A, 9A, and 10A are plan views showing other examples of the manufacturing method of the optical circuit 1. Figure 8B is a cross-sectional view along the line 8B-8B in Figure 8A, Figure 9B is a cross-sectional view along the line 9B-9B in Figure 9A, and Figure 10B is a cross-sectional view along the line 10B-10B in Figure 10A.

[0032] First, a substrate 40 is prepared, consisting of a diamond layer 40A and a low refractive index material layer 40B made of a material with a lower refractive index than diamond. Next, impurity atoms are implanted into the diamond layer 40A by ion implantation to form multiple color centers 30 in the diamond layer 40A. Then, from among the multiple color centers 30 formed in the diamond layer 40A, those that satisfy predetermined conditions regarding luminescence characteristics are selected. Next, considering the selection results of the color centers 30, a pattern 10P of the first optical circuit 10 to be cut out from the diamond layer 40A is formulated (Figure 8A).

[0033] Next, the diamond layer 40A is etched to cut out the first optical circuit 10 having the pattern 10P formulated in the above process from the diamond layer 40A. That is, the first optical circuit 10 is formed on the surface of the low refractive index material layer 40B (Figures 9A and 9B).

[0034] Next, the third optical waveguide 21 is cut out from the low refractive index material layer 40B by etching the low refractive index material layer 40B. For example, the third optical waveguide 21 is formed by etching the low refractive index material layer 40B in such a way that it separates the third optical waveguide 21 from the rest of the material (Figures 10A and 10B). By using a substrate 40 in which the diamond layer 40A and the low refractive index material layer 40B are laminated, the step of connecting the first optical circuit 10 and the second optical circuit 20 can be omitted.

[0035] [Second Embodiment] Figure 11 is a plan view showing an example of the configuration of a first optical circuit 10A according to a second embodiment of the disclosed technology. Similar to the first optical circuit 10 according to the first embodiment, the first optical circuit 10A according to this embodiment includes a first optical waveguide 11 that functions as a bus line and a plurality of second optical waveguides 12 that constitute a nanobeam.

[0036] In the first optical circuit 10A according to this embodiment, at least one of the plurality of second optical waveguides 12 has a fourth optical waveguide 14 connected to the first optical waveguide 11 and extending in a direction intersecting the extension direction of the first optical waveguide 11. Preferably, the fourth optical waveguide 14 does not include a color center. The first optical circuit 10A also has a plurality of fifth optical waveguides 15, each including a color center 30 and connected to a plurality of portions along the extension direction of the fourth optical waveguide 14. That is, the first optical circuit 10A has the configuration of the first optical circuit 10 according to the first embodiment as the configuration of the second optical waveguide 12.

[0037] According to the first optical circuit 10A of this embodiment, the number of nanobeams (qubits) connected to a single optical waveguide can be increased, thus enabling further large-scale integration.

[0038] [Third Embodiment] Figure 12 shows an example of the configuration of a quantum computing device 100 according to a third embodiment of the disclosed technology. The quantum computing device 100 is a diamond spin type quantum computing device that utilizes the electron spins of color centers 30 included in the first optical circuit 10 as qubits. The quantum computing device 100 includes an excitation light source 101, an optical system 102, a microwave generator 103, a magnetic field generator 104, a photodetector 105, and a signal processing device 106.

[0039] The excitation light source 101 outputs light for qubit manipulation. The light output from the excitation light source 101 is irradiated onto a color center 30 formed in the first optical circuit 10 via the optical system 102. The optical system 102 may include a focusing lens that concentrates the light output from the excitation light source 101 onto the color center 30. The color center 30 is excited by the light irradiation and generates light.

[0040] The microwave generator 103 and the magnetic field generator 104 generate microwaves and magnetic fields, respectively, in conjunction with the irradiation of light from the excitation light source 101. The substrate 40 functions as a microwave generation circuit and a magnetic field generation circuit. The microwaves and magnetic fields output from the microwave generator 103 and the magnetic field generator 104 act on the color center 30 via the substrate 40.

[0041] Light emitted from the color center 30 is guided to the photodetector 105 via the third optical waveguide 21. The photodetector 105 is a single-photon detector and detects the light emitted from the color center 30. The photodetector 105 may be mounted on the substrate 40. The signal processing device 106 outputs an electrical signal in response to the light detected by the photodetector 105.

[0042] Figure 13 shows another example of the configuration of the quantum computing device 100. As shown in Figure 13, the light output from the excitation light source 101 may be introduced into the third optical waveguide 21 via the optical fiber 107 to excite the color center 30. [Explanation of symbols]

[0043] 1, 1X optical circuit 10, 10A First optical circuit 11. First Optical Waveguide 12, 12a, 12b Second optical waveguide 13 Tapered section 14. The fourth optical waveguide 15. The fifth optical waveguide 20. Second Optical Circuit 21. Third Optical Waveguide 22 Part 1 23 Part 2 30 Color Center 40 circuit boards 40A Diamond Layer 40B Low refractive index material layer 50 Diamond substrates 51 Resist 70 Support part 100 Quantum computing device 101 Excitation light source 105 Photodetector

Claims

1. A first optical waveguide extending in a first direction and made of diamond, Each of the following is a plurality of second optical waveguides, each made of diamond, containing a color center, connected to the first optical waveguide, and extending in a direction different from the first direction. A third optical waveguide, made of a material with a lower refractive index than diamond, extending in the first direction and connected to the first optical waveguide, It has, The first optical waveguide does not include a color center. Each of the plurality of second optical waveguides includes a single color center. optical circuit.

2. Each of the plurality of second optical waveguides is connected to the first optical waveguide in such a way that the direction of propagation of the light emitted from the color center in the first optical waveguide is the same for all of them. The optical circuit according to claim 1.

3. The plurality of second optical waveguides are connected to both sides of the first optical waveguide that are opposite to each other along the first direction. The optical circuit according to claim 1.

4. At least one of the plurality of second optical waveguides has a tapered portion whose width gradually decreases toward the connection point with the first optical waveguide. The optical circuit according to claim 3.

5. The first optical waveguide and the second optical waveguide are configured as an integrated unit. The optical circuit according to claim 1.

6. The structure has a first optical waveguide and a third optical waveguide stacked on top of each other. The optical circuit according to claim 1.

7. The third optical waveguide includes a first portion connected to one end of the first optical waveguide in the first direction, and a second portion connected to the other end of the first optical waveguide in the first direction. The first part and the second part further include a support portion for supporting the first optical waveguide and the second optical waveguide. The optical circuit according to claim 6.

8. At least one of the plurality of second optical waveguides is A fourth optical waveguide is connected to the first optical waveguide and extends in a second direction different from the first direction, Each includes a color center and a plurality of fifth optical waveguides connected to the fourth optical waveguide, The optical circuit according to claim 1, having the following features.

9. A step of forming a plurality of color centers in a first member made of diamond by injecting impurities into the first member, A step of obtaining an optical circuit from the first member, which includes a first optical waveguide extending in a first direction, and a plurality of second optical waveguides, each containing at least one of the plurality of color centers, connected to the first optical waveguide, and extending in a direction different from the first direction; A step of connecting a third optical waveguide, made of a material with a lower refractive index than diamond and extending in the first direction, to the first optical waveguide, It has, The first optical waveguide does not include a color center. Each of the plurality of second optical waveguides includes a single color center. A method for manufacturing optical circuits.

10. Prior to the step of acquiring the optical circuit, the process further includes a step of identifying among the plurality of color centers that satisfy predetermined conditions regarding emission characteristics. A method for manufacturing an optical circuit according to claim 9.

11. The impurities are injected into the first member via a resist that covers the planned location for forming the first optical waveguide of the diamond. The manufacturing method according to claim 9.

12. An optical circuit including a first optical waveguide and a second optical waveguide is obtained from the diamond layer of the first member, which is made of a diamond layer and a low refractive index material layer made of a material with a lower refractive index than diamond. The third optical waveguide is obtained from the low refractive index material layer. The manufacturing method according to claim 9.

13. Optical circuit including color center, A light source for exciting the aforementioned color center, A photodetector that detects light emitted from the aforementioned color center, Includes, The optical circuit is A first optical waveguide extending in a first direction and made of diamond, Each of the following is a plurality of second optical waveguides, each made of diamond, containing a color center, connected to the first optical waveguide, and extending in a direction different from the first direction. A third optical waveguide, made of a material with a lower refractive index than diamond, extending in the first direction and connected to the first optical waveguide, It has, The first optical waveguide does not include a color center. Each of the plurality of second optical waveguides includes a single color center. Quantum computing device.

14. Light emitted from color centers formed in each of the plurality of second optical waveguides is propagated in common to the third optical waveguide via the first optical waveguide. The optical circuit according to claim 1.

15. A first optical waveguide extending in a first direction and made of diamond, Each of the following is a plurality of second optical waveguides, each made of diamond, containing a color center, connected to the first optical waveguide, and extending in a direction different from the first direction. A third optical waveguide, made of a material with a lower refractive index than diamond, extending in the first direction and connected to the first optical waveguide, It has, An optical circuit characterized in that the connection angle between each of the plurality of second optical waveguides and the first optical waveguide is obtuse on the downstream side in the direction of propagation of light propagating through the first optical waveguide.

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