Quantum computing device and quantum computing device manufacturing method

Abstract

An optical waveguide is produced that includes a first section with a light incident face and a second section with a light emitting face. An indentation is formed with a profile corresponding to a profile of the first section at a mounting position for the optical waveguide of a substrate to be mounted with the optical waveguide. The optical waveguide is mounted on the substrate by arranging the first section in the recess. A crystal body is formed that is connected to the second section and includes a color center. A photodetector is formed on the substrate to detect light emitted from the light emitting face. The first section has side faces that intersect with the light incident face and are inclined with respect to the light incident face such that a surface area of a cross-section of the first section intersecting with a progression direction of light gradually reduces along the light progression direction. A center axis of the first section and a center axis of the second section are present on a straight line.

Description

QUANTUM COMPUTING DEVICE AND QUANTUM COMPUTING DEVICE MANUFACTURING METHOD

[0001] The technology disclosed herein relates to a quantum computing device and to a manufacturing method of a quantum computing device.

[0002] The following technology is known as technology related to optical waveguides. For example, technology is known in which a first waveguide core section and a second waveguide core section are connected together by a taper shaped waveguide core section having a curved taper profile.

[0003] Moreover, in optical equipment having an optical fiber connected to a waveguide optical device, technology is known that includes an optical-fiber-side spot-size-converter section equipped with a core that, at a vicinity to a connection portion of an optical fiber to a waveguide optical device, gradually reduces in cross-sectional area from the optical fiber toward the waveguide optical device.

[0004] Japanese Patent Application Laid-Open (JP-A) No. 2010-277048JP-A No. 2004-252153

[0005] There are expectations of high temperature operation and a higher degree of integration in quantum computing devices utilizing color centers, which are configured by a hole where a carbon atom is missing in a diamond single crystal and an impurity atom adjacent thereto, and recently there is active research and development in this area. In this type of quantum computing device, light is shone onto a crystal body having a color center in order to perform a qubit operation. The shining of light onto the crystal body is performed by guiding light emitted from an optical fiber onto the crystal body through an optical waveguide. The width of the optical waveguide employed in a quantum computing device is assumed to be 1 μm or less. A core diameter of an optical fiber is, however, assumed to be at least 3 μm. In order to optically couple the optical fiber and the optical waveguide together with low loss, the light incident face of the optical waveguide is preferably a size that is equivalent to the core diameter of the optical fiber. In such cases, an optical waveguide obtained is configured such that the surface area of the light incident face is larger than the surface area of the light emitting face. Namely, an optical waveguide obtained includes a taper shaped section configured such that a surface area of cross-section intersecting with a progression direction of light changes along the light progression direction. An optical waveguide configured in this manner suffers from an issue of a loss in the light propagating along the optical waveguide.

[0006] An object of the technology disclosed herein is, in a quantum computing device equipped with an optical waveguide, to suppress loss of light propagating along the optical waveguide.

[0007] A manufacturing method of a quantum computing device according to technology disclosed herein includes a process of producing an optical waveguide including a first section with a light incident face and a second section with a light emitting face. The manufacturing method also includes a process of forming an indentation having a profile corresponding to a profile of the first section at a mounting position for the optical waveguide of a substrate, and a process of mounting the optical waveguide on the substrate by arranging the first section in the recess. The manufacturing method also includes a process of forming a crystal body that is connected to the second section and includes a color center, and a process of forming a photodetector on the substrate to detect light emitted from the light emitting face. The first section has side faces that intersect with the light incident face and are inclined with respect to the light incident face such that a surface area of a cross-section of the first section intersecting with a progression direction of light gradually reduces along the light progression direction, and a center axis of the first section and a center axis of the second section are present on a straight line.

[0008] The technology disclosed herein enables, in a quantum computing device equipped with an optical waveguide having a taper shaped section, loss of light propagating along the optical waveguide to be suppressed.

[0009] Fig. 1 is a perspective view illustrating an example of a configuration of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 2 is a cross-section of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 3 is a perspective view illustrating an example of a configuration of an optical waveguide according to an exemplary embodiment of technology disclosed herein.Fig. 4 is a cross-section illustrating a manner in which light of a specific wavelength is shone through an optical waveguide and onto a crystal body using a fiber.Fig. 5A is a perspective view illustrating an example of a manufacturing method of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 5B is a perspective view illustrating an example of a manufacturing method of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 5C is a perspective view illustrating an example of a manufacturing method of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 5D is a perspective view illustrating an example of a manufacturing method of a quantum computing device according to an exemplary embodiment of technology disclosed herein.Fig. 6 is a perspective view illustrating an example of a configuration of a quantum computing device according to a comparative example.Fig. 7 is a cross-section illustrating an example of a configuration of a quantum computing device according to a comparative example.Fig. 8 is a perspective view illustrating an example of a manufacturing method of a quantum computing device according to a comparative example.Fig. 9 is a perspective view illustrating an example of a configuration of a quantum computing device according to another exemplary embodiment of technology disclosed herein.Fig. 10 is a cross-section illustrating an example of a configuration of a quantum computing device according to another exemplary embodiment of technology disclosed herein.Fig. 11 is a cross-section of an optical waveguide according to another exemplary embodiment of technology.Fig. 12 is a perspective view illustrating an example of a configuration of a quantum computing device according to another exemplary embodiment of technology disclosed herein.Fig. 13 is a cross-section of a quantum computing device according to another exemplary embodiment of technology disclosed herein.Fig. 14 is a cross-section of an optical waveguide according to another exemplary embodiment of technology disclosed herein.

[0010] Description follows regarding an example of an exemplary embodiment of the present invention, with reference to the drawings. Note that the same or equivalent configuration elements and parts are appended with the same reference numerals in the drawings, and duplicate explanation thereof will be omitted. Note that in the drawings a progression direction of light propagating inside an optical waveguide, described later, is a Z direction, and two directions orthogonal to the Z direction and having an orthogonal relationship to each other are an X direction and a Y direction. The X direction is a width direction of the optical waveguide, and the Y direction is the height direction of the optical waveguide.

[0011] First Exemplary Embodiment Fig. 1 is a perspective view illustrating an example of a configuration of a quantum computing device 1 according to a first exemplary embodiment of technology disclosed herein. Fig. 2 is a Y-Z cross-section of the quantum computing device 1. The quantum computing device 1 includes a substrate 10, an optical waveguide 20, a crystal body 30, and a photodetector 40. The optical waveguide 20 and the photodetector 40 are provided on a surface of the substrate 10, and the crystal body 30 is provided on a surface of the optical waveguide 20. Fig. 3 is a perspective view in which only the optical waveguide 20 has been extracted from out of the above configuration elements configuring the quantum computing device 1.

[0012] The optical waveguide 20 is, for example, obtained by configuring from a single crystal material having optical transparency, such as Al2O3(sapphire), SiO2, Si3N4, SiC, or the like. The optical waveguide 20 includes a first section 21 with a light incident face 23, and a second section 22 with a light emitting face 24. The second section 22 is integrally provided to the first section 21.

[0013] The first section 21 of the optical waveguide 20 has respective side faces inclined with respect to the light incident face 23 and intersecting with the light incident face 23 of the first section 21, such that the surface area of a cross-section intersecting with the light progression direction (hereafter referred to as a light path cross-section) gradually reduces along the light progression direction. In the present exemplary embodiment, the profile of the first section 21 is a truncated pyramid, and the first section 21 includes flat first to fourth faces 25A, 25B, 25C, 25D as the side faces intersecting with the light incident face 23 of the first section 21 (see Fig. 3). The first face 25A is a face that contacts a bottom face of a recess 11 provided in the substrate 10. The second face 25B is a face that opposes the first face 25A. The third face 25C is a face intersecting with the first face 25A and the second face 25B. The fourth face 25D is a face opposing the third face 25C. The first to fourth faces 25A to 25D are each inclined with respect to the light incident face 23.

[0014] The second section 22 of the optical waveguide 20 has a constant surface area of light path cross-section. In the present exemplary embodiment the profile of the second section 22 is a square column shape. The surface area of the light path cross-section of the second section 22 is smaller than the surface area of the light incident face 23, and matches the surface area of the light path cross-section at the connection portion 29 between the first section 21 and the second section 22. The first section 21 has a surface area of light path cross-section that gradually diminishes along the light progression direction in a segment from the light incident face 23 to the connection portion 29, and functions as a size conversion element that matches to the surface area of the light path cross-section of the second section 22. In the optical waveguide 20, a center axis 26A of the first section 21 and a center axis 26B of the second section 22 are present on a straight line. Namely, light introduced into the optical waveguide 20 from the light incident face 23 has a straight ahead progression direction without bending and is emitted from the light emitting face 24.

[0015] The substrate 10 is preferably configured by a material having a lower refractive index that that of the optical waveguide 20. This thereby enables light to be suppressed from leaking from the optical waveguide 20. An example of a material that may be employed for the substrate 10 is SiO2. The substrate 10 may also be a layered body configured by layering plural materials. For example, a layered body configured by layering SiO2on a surface of Al2O3may be employed for the substrate 10. The substrate 10 includes the recess 11 having a profile at a mounting position of the optical waveguide 20 that is a profile corresponding to the profile of the first section 21 of the optical waveguide 20. The optical waveguide 20 is mounted to the substrate 10 in a state in which the first section 21 is fitted into the recess 11 of the substrate 10.

[0016] A bottom face 12 of the recess 11 is inclined with respect to a main face 13 of the substrate 10, and contacts the first face 25A of the optical waveguide 20. The second section 22 of the optical waveguide 20 contacts the main face 13 of the substrate 10. The first section 21 of the optical waveguide 20 is fitted into the recess 11, and in a state in which the optical waveguide 20 is mounted to the substrate 10, a center axis of the optical waveguide 20 (the center axis 26A of the first section 21 and the center axis 26B of the second section 22) is parallel to the main face 13 of the substrate 10. The light incident face 23 is disposed within a plane extending from a side face of the substrate 10.

[0017] The photodetector 40 detects light emitted from the light emitting face 24 of the optical waveguide 20. The photodetector 40 is, for example, a photodiode, and outputs an electrical signal according to an intensity of the light detected.

[0018] The crystal body 30 is connected to the second section 22 of the optical waveguide 20. The crystal body 30 is, for example, a diamond single crystal, including, in the crystal, a color center (NV center) configured by a hole where a carbon atom is missing and an impurity atom (for example, a nitrogen atom) adjacent to the hole. The color center functions as a qubit. Light generation from the color center propagates through the optical waveguide 20 and is detected by the photodetector 40. Reading of quantum information is implemented thereby.

[0019] Qubit operation is performed by employing an optical fiber to shine external light of a specific wavelength onto the crystal body 30 through the optical waveguide 20. Fig. 4 is a Y-Z cross-section illustrating a manner in which external light of a specific wavelength is shone onto the crystal body 30 through the optical waveguide 20 using an optical fiber 200. The light emitted from the optical fiber 200 is shone onto the light incident face 23 of the optical waveguide 20, and is introduced into the optical waveguide 20. The optical fiber 200 is, for example, a single mode optical fiber, with a core diameter φ1 that is, for example, about 3 μm. A width and height Y1 of the light incident face 23 at the first section 21 of the optical waveguide 20 is equivalent to the core diameter φ1 of the optical fiber 200. A width and height Y2 of the second section 22 of the optical waveguide 20 are each 1 μm or less. Suppose the optical waveguide 20 was configured with the second section 22 alone, then the width and height of the optical waveguide 20 would be significantly smaller than the core diameter φ1 of the optical fiber 200, and so there would be a great light loss. The optical waveguide 20 is provided with the first section 21 having the light incident face 23 of a size equivalent to the core diameter φ1 of the optical fiber 200, thereby enabling light loss to be suppressed from occurring. The center axis 26A of the first section 21 and the center axis 26B of the second section 22 are present on a straight line, and so light introduced from the light incident face 23 into the optical waveguide 20 has a straight ahead progression direction without bending and is emitted from the light emitting face 24.

[0020] Description follows regarding a manufacturing method of the quantum computing device 1 according to the present exemplary embodiment. Fig. 5A to Fig. 5D are perspective views illustrating an example of a manufacturing method of the quantum computing device 1.

[0021] A crystal block 27 that is a source material for the optical waveguide 20 is prepared. Examples of materials that may be employed as the crystal block 27 include blocks of Al2O3(sapphire), SiO2, Si3N4, SiC, or the like. Next the optical waveguide 20 is cut out from the crystal block 27 by performing cutting processing on the crystal block 27 (Fig. 5A). The optical waveguide 20 is cut out from the crystal block 27 in a state in which the first section 21 and the second section 22 are integrated together. The cutting processing may be performed by, for example, laser processing or focused ion beam (FIB) processing.

[0022] Next the substrate 10 is prepared, and the substrate 10 is preferably configured from a source material having a lower refractive index than that of the optical waveguide 20. Examples of materials that may be employed for the source material of the substrate 10 include SiO2. Next, the recess 11 is formed in the substrate 10 at the mounting position of the optical waveguide 20, with a profile corresponding to the profile of the first section 21 of the optical waveguide 20 (Fig. 5B). The bottom face 12 of the recess 11 is inclined with respect to the main face 13 of the substrate 10 so as to correspond to the inclination of the first face 25A of the first section 21 of the optical waveguide 20. The recess 11 may, for example, be formed by laser processing or FIB processing.

[0023] Next, the optical waveguide 20 is mounted to substrate 10 by the first section 21 of the optical waveguide 20 produced by the previous processes being fitted into the recess 11 of the substrate 10. The substrate 10 and the optical waveguide 20 are closely adhered by intermolecular forces (see Fig. 5C).

[0024] Next, the crystal body 30 is formed on the upper face of the second section 22 of the optical waveguide 20 (Fig. 5D). The crystal body 30 may, for example, be formed using a known diamond synthesizing technology such as, for example, a chemical vapor deposition (CVD) method, a high pressure high temperature (HPHT) method, or the like. The color center (NV center) may be formed inside the crystal body 30 by adding trace quantities of nitrogen to the source gas during diamond synthesis, or by ions implantation of nitrogen atoms, and performing a final annealing process thereafter. Next the photodetector 40 is formed on the substrate 10 at a position adjacent to the light emitting face 24 of the optical waveguide 20 (Fig. 5D). A photodetector 40 formed on a different substrate to the substrate 10 may also be mounted on the substrate 10.

[0025] Fig. 6 is a perspective view illustrating an example of a configuration of a quantum computing device 1X according to a comparative example, and Fig. 7 is a Y-Z cross-section of the quantum computing device 1X according to the comparative example. A substrate 10 in the quantum computing device 1X according to the comparative example lacks a recess into which to fit a first section 21 of the optical waveguide 20. Namely, in the quantum computing device 1X according to the comparative example, the optical waveguide 20 is mounted to a flat surface of the substrate 10, and a face of the first section 21 of the optical waveguide 20 that contacts the substrate 10 and a face of the second section 22 of the optical waveguide 20 that contacts the substrate 10 both extend in the same plane. Moreover, in the quantum computing device 1X according to the comparative example, a center axis 26A of the first section 21 of the optical waveguide 20 and a center axis 26B of the second section 22 of the optical waveguide 20 are not present on a straight line. Namely, the center axis of the optical waveguide 20 is bent at a connection portion 29 between the first section 21 and the second section 22. A loss accordingly arises in light propagating through the optical waveguide 20.

[0026] However, in the quantum computing device 1 according to the exemplary embodiment of technology disclosed herein, the substrate 10 includes the recess 11 having a profile at the optical waveguide 20 mounting position corresponding to the profile of the first section 21 of the optical waveguide 20, and so the optical waveguide 20 is mounted in a state in which the first section 21 is fitted into the recess 11. A configuration equipped with the optical waveguide 20 including the first section 21 having a taper profile with all four side faces (the first to fourth faces 25A to 25D) being inclined faces is accordingly achieved, enabling the center axis 26A of the first section 21 and the center axis 26B of the second section 22 to be present on a straight line. Making the center axis of a path of the optical waveguide 20 from the light incident face 23 to the light emitting face 24 a straight line enables a loss of light propagating along the optical waveguide 20 to be suppressed from occurring.

[0027] A gain arising due to the mode propagation method is computed for the first section 21 of the optical waveguide 20. The conditions of calculation are as follows. The profile of the first section 21 is a truncated pyramid. A length of the first section 21 in the light progression direction is 40 μm. A size of the light incident face 23 is 3 μm × 3 μm. A size of the light path cross-section at the connection portion 29 between the first section 21 and the second section 22 is 0.5 μm × 0.5 μm. Under the above conditions a power of light propagating through the second section 22 for a case in which the center axis of a path of the optical waveguide 20 from the light incident face to the light emitting face is bent was 79% of the light incident to the light incident face 23 (gain: -1.04 dB). However, under the same conditions, the power of light propagating through the second section 22 for a case in which the center axis of a path of the optical waveguide 20 from the light incident face to the light emitting face is a straight line was 89.3% of the light incident to the light incident face 23 (gain: -0.49 dB).

[0028] The following method is another conceivable method for forming a structure in which the first section 21 of the optical waveguide 20 is fitted into the recess 11 of the substrate 10. For example, as illustrated in Fig. 8, after the recess 11 has been formed in the substrate 10 with a profile at the mounting position of the optical waveguide 20 corresponding to the profile of the first section 21, a single crystal material 20A for forming the optical waveguide 20 is deposited on the surface of the substrate 10 using a CVD method. Then the optical waveguide 20 is formed on the substrate 10 by processing the single crystal material 20A so as to achieve a desired profile. However, a plane direction of crystal as exhibited at a bottom face of the recess 11 is different to a plane direction of the main face of the substrate 10, and so it is difficult to deposit a high quality single crystal material 20A on the surface of the substrate 10 using a crystal growth method. Namely, a structure in which the center axis 26A of the first section 21 and the center axis 26B of the second section 22 are present on a straight line is difficult to implement with the above method.

[0029] However, in the manufacturing method according to the exemplary embodiment of technology disclosed herein the optical waveguide 20 produced independently from the substrate 10 is mounted to the substrate 10. Namely, the optical waveguide 20 is provided on the substrate 10 without employing a crystal growth method. This thereby enables a structure to be formed in which the first section 21 of the optical waveguide 20 is fitted into the recess 11 of the substrate 10, enabling a structure to be realized in which the center axis 26A of the first section 21 and the center axis 26B of the second section 22 are present on a straight line.

[0030] Second Exemplary Embodiment The loss of light propagating along the optical waveguide 20 diminishes as the inclination of the side faces of the first section 21 of the optical waveguide 20 becomes shallower. In other words, the light loss is smaller as the length of the first section 21 of the optical waveguide 20 becomes longer in the light progression direction. However, a longer length for the first section 21 makes it difficult to achieve a higher degree of integration in a quantum computing device. A quantum computing device according to a second exemplary embodiment described below is one that improves a tradeoff relationship between a light progression direction length of the first section 21 of the optical waveguide 20 and light loss.

[0031] Fig. 9 is a perspective view illustrating an example of a configuration of a quantum computing device 1A according to the second exemplary embodiment of technology disclosed herein. Fig. 10 is a Y-Z cross-section of the quantum computing device 1A. The quantum computing device 1 according to the first exemplary embodiment as described above (see Fig. 1 and Fig. 2) has a first section 21 of an optical waveguide 20 having side faces (a first face 25A to a fourth face 25D) inclined with respect to the light incident face 23 that are each respectively flat faces. In contrast thereto, the quantum computing device 1A according to the second exemplary embodiment includes an optical waveguide 20 having side faces inclined with respect to the light incident face 23 of the first section 21 that are each respectively curved faces. The quantum computing device 1A is similar to the quantum computing device 1 according to the first exemplary embodiment from the perspective of the center axis 26A of the first section 21 and the center axis 26B of the second section 22 being present on a straight line, and from the perspective of the optical waveguide 20 being mounted to the substrate 10 in a state in which the first section 21 is fitted into the recess 11 of the substrate 10.

[0032] An X-Z cross-section of an optical waveguide 20 according to a second exemplary embodiment is illustrated at the top of Fig. 11, and a Y-Z cross-section of the optical waveguide 20 according to the second exemplary embodiment is illustrated at the bottom of Fig. 11. The profile of side faces of the first section 21 of the optical waveguide 20 according to the present exemplary embodiment is expressed by the following Equation (1) and Equation (2). In Equation (1) X(z) is the X direction length at an Z direction position z of the first section 21. X1 is the X direction length of the light incident face 23. X2 is the X direction length at the connection portion 29 between the first section 21 and the second section 22 (see the top of Fig. 11). Y(z) in Equation (2) is the Y direction length at the Z direction position z of the first section 21. Y1 is the Y direction length of the light incident face 23. Y2 is the Y direction length at the connection portion 29 between the first section 21 and the second section 22. In Equation (1) and Equation (2), a is an integer of 2 or higher. L is the Z direction length from the light incident face 23 to the connection portion 29. As indicated by Equation (1) and Equation (2), the side faces inclined with respect to the light incident face 23 of the first section 21 are expressed by a polynomial equation having an order of 2 or higher.

[0033]

[0034]

[0035] The gain according to the mode propagation method was computed for the first section 21 of the optical waveguide 20 having curved side faces. The conditions of calculation are as follows. The side faces of the first section 21 are curved faces expressed by a third order polynomial. The light progression direction length of the first section 21 is 40 μm. The size of the light incident face 23 is 3 μm × 3 μm. The size of the light path cross-section at the connection portion 29 between the first section 21 and the second section 22 is 0.5 μm × 0.5 μm. Under the above conditions, the power of light propagating through the second section 22 for a case in which the center axis of a path of the optical waveguide 20 from the light incident face to the light emitting face is bent was 88% of the light incident to the light incident face 23 (gain: -0.55 dB). However, under the same conditions the power of light propagating through the second section 22 for a case in which the center axis of a path of the optical waveguide 20 from the light incident face to the light emitting face is a straight line was 89.9% of the light incident to the light incident face 23 (gain: -0.46 dB). Namely, the power of light propagating through the second section 22 is increased from that of the optical waveguide 20 according to the first exemplary embodiment. The quantum computing device 1A according to the second exemplary embodiment enables an improvement to be achieved in the tradeoff relationship between the light progression direction length of the first section 21 of the optical waveguide 20 and light loss.

[0036] Third Exemplary Embodiment Fig. 12 is a perspective view illustrating an example of a configuration of a quantum computing device 1B according to a third exemplary embodiment of technology disclosed herein. Fig. 13 is a Y-Z cross-section of the quantum computing device 1B. The quantum computing device 1B according to the third exemplary embodiment is a configuration in which the side faces of the optical waveguide 20 inclined with respect to the light incident face 23 of the first section 21 are configured by connecting plural curved faces expressed by mutually different polynomials together along the light progression direction (Z direction). The quantum computing device 1B is similar to the quantum computing device 1 according to the first exemplary embodiment from the perspective of the center axis 26A of the first section 21 and the center axis 26B of the second section 22 being present on a straight line, and from the perspective of the optical waveguide 20 being mounted to the substrate 10 in a state in which the first section 21 is fitted into the recess 11 of the substrate 10.

[0037] An X-Z cross-section of the optical waveguide 20 according to the third exemplary embodiment is illustrated at the top of Fig. 14, and an Y-Z cross-section of the optical waveguide 20 according to the third exemplary embodiment is illustrated at the bottom of Fig. 14. The profile of side faces of the first section 21 of the optical waveguide 20 according to the present exemplary embodiment is expressed by Equation (3) and Equation (4). In Equation (3), X(z) is an X direction length of the first section 21 at the Z direction position z. X1 is an X direction length of the light incident face 23. X2 is an X direction length at a connection portion 29A between curved faces connected together in the light progression direction (Z direction). X3 is an X direction length at a connection portion 29B between the first section 21 and the second section 22. In Equation (4) Y(z) is a Y direction length at the Z direction position z of the first section 21. Y1 is a Y direction length of the light incident face 23. Y2 is a Y direction length at a connection portion 29A between curved faces connected together in the light progression direction (Z direction). Y3 is a Y direction length at the connection portion 29B between the first section 21 and the second section 22. In Equation (3) and Equation (4), a and b are integers of 2 or higher. L1 is the Z direction length from the light incident face 23 to the connection portion 29A. L2 is the Z direction length from the light incident face 23 to the connection portion 29B.

[0038]

[0039]

[0040] The quantum computing device 1B according to the present exemplary embodiment enables the loss of light propagating along the optical waveguide 20 to be made even smaller.

[0041] 1, 1A, 1B quantum computing device 10 substrate 11 recess 20 optical waveguide 21 first section 22 second section 23 light incident face 24 light emitting face 25A first face 25B second face 25C third face 25D fourth face 26A, 26B center axis 30 crystal body 40 photodetector

Claims

1. A manufacturing method of a quantum computing device comprising: a process of producing an optical waveguide including a first section with a light incident face and a second section with a light emitting face; a process of forming an indentation having a profile corresponding to a profile of the first section at a mounting position for the optical waveguide of a substrate; a process of mounting the optical waveguide on the substrate by arranging the first section in the recess; a process of forming a crystal body that is connected to the second section and includes a color center; and a process of forming a photodetector on the substrate to detect light emitted from the light emitting face, wherein: the first section has side faces that intersect with the light incident face and are inclined with respect to the light incident face such that a surface area of a cross-section of the first section intersecting with a progression direction of light gradually reduces along the light progression direction; and a center axis of the first section and a center axis of the second section are present on a straight line.

2. The manufacturing method of claim 1, wherein: the side faces of the first section that intersect with the light incident face include a first face contacting a bottom face of the recess, a second face opposing the first face, a third face intersecting with the first face and the second face, and a fourth face opposing the third face, with the first to the fourth faces each being inclined with respect to the light incident face; the bottom face of the recess is inclined with respect to a main face of the substrate; and the center axis of the first section and the center axis of the second section are parallel to the main face of the substrate.

3. The manufacturing method of claim 2, wherein the optical waveguide is produced by cutting processing performed on a crystal block having optical transparency.

4. The manufacturing method of claim 2 or claim 3, wherein the first to fourth faces are flat faces.

5. A manufacturing method of claim 2 or claim 3, wherein the first to fourth faces are curved faces.

6. A manufacturing method of claim 2 or claim 3 wherein the substrate is configured from a source material having a lower refractive index than that of the optical waveguide.

7. A quantum computing device comprising: an optical waveguide including a first section with a light incident face and a second section with a light emitting face; a substrate that includes an indentation having a profile corresponding to a profile of the first section at a mounting position for the optical waveguide and that is mounted with the optical waveguide in a state in which the first section is arranged in the recess; a crystal body including a color center connected to the second section; a photodetector that detects light emitted from the light emitting face, wherein: the first section has side faces that intersect with the light incident face and are inclined with respect to the light incident face such that a surface area of a cross-section of the first section intersecting with a progression direction of light gradually reduces along the light progression direction; and a center axis of the first section and a center axis of the second section are present on a straight line.

8. The quantum computing device of claim 7, wherein: the side faces of the first section that intersect with the light incident face include a first face contacting a bottom face of the recess, a second face opposing the first face, a third face intersecting with the first face and the second face, and a fourth face opposing the third face, with the first to the fourth faces each being inclined with respect to the light incident face; the bottom face of the recess is inclined with respect to a main face of the substrate; and the center axis of the first section and the center axis of the second section are parallel to the main face of the substrate.

9. The quantum computing device of claim 7 or claim 8, wherein the first to fourth faces are flat faces.

10. The quantum computing device of claim 7 or claim 8, wherein the first to fourth faces are curved faces.

11. The quantum computing device of claim 7 or claim 8, wherein the substrate is configured by a source material having a lower refractive index than that of the optical waveguide.

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