Optical communication system for quantum computer, quantum computer, and method for manufacturing quantum computer

Abstract

An optical communication system 6A comprises: a plurality of modulators 63 that each generate a plurality of optical control signals on the basis of a plurality of first microwave control signals; an image fiber 64A that includes a plurality of second single-core optical fibers 645A that propagate the plurality of optical control signals, and a tubular member 641 that houses the plurality of second single-core optical fibers 645A; and a light-receiving substrate 65 that receives the plurality of optical control signals from the plurality of second single-core optical fibers 645A, converts the plurality of optical control signals into a plurality of second microwave control signals, and transmits the plurality of second microwave control signals to a quantum circuit 2.

Description

Optical communication system for quantum computers, quantum computers, and methods for manufacturing quantum computers

[0001] The present invention relates to an optical communication system for a quantum computer, a quantum computer, and a method for manufacturing a quantum computer. For designated countries where incorporation by reference of documents is permitted, the content of Japanese Patent Application No. 2024-099973, filed in Japan on June 20, 2024, is incorporated by reference into this specification and made a part of the description of this specification.

[0002] In quantum computing, a signal distribution system including a photonic link is known (see, for example, Patent Document 1 and Non-Patent Document 1). The operating environment of this signal distribution system includes a cryogenic environment, a continuous wave (CW) laser, a microwave generator, an electro-optic modulator, an optical fiber arranged in the cryogenic environment, and a photodetector (see, for example, Figure 5 of Patent Document 1 and Figure 1 of Non-Patent Document).

[0003] U.S. Pat. No. 1,1742,955

[0004] Lecocq et al. “Control and readout of a superconducting qubit using a photonic link”, 2021, Nature

[0005] In the above-mentioned Patent Document 1 and Non-Patent Document 1, light emitted from a plurality of CW laser light sources with different wavelengths is coupled to a single-core optical fiber for transmission. Therefore, it is necessary to use WDM (Wavelength Division Multiplexing) as the communication method for the optical signal input to the single-core optical fiber, and it is therefore necessary to place a wavelength multiplexer and a wavelength demultiplexer at the upstream and downstream stages of the single-core optical fiber, respectively. However, there is a problem in that the wavelength multiplexer and wavelength demultiplexer have large volumes, which results in an increase in the size of the signal distribution system.

[0006] The problem to be solved by the present invention is to provide an optical communication system for a quantum computer, a quantum computer, and a method for manufacturing the same that can reduce space.

[0007] [1] Aspect 1 of the present invention is an optical communication system for a quantum computer comprising: an optical signal generator that generates a plurality of optical control signals based on a plurality of first microwave control signals; an image fiber including a plurality of optical fibers that transmit the plurality of optical control signals, respectively, and a tubular member that houses the plurality of optical fibers; and a plurality of photodetectors that receive the plurality of optical control signals from the plurality of optical fibers, convert the plurality of optical control signals into a plurality of second microwave control signals, respectively, and transmit the second microwave control signals to a quantum circuit.

[0008] [2] A second aspect of the present invention may be an optical communication system for a quantum computer according to the first aspect, wherein at least a part of the image fiber is disposed inside a refrigerator of the quantum computer.

[0009] [3] Aspect 3 of the present invention may be an optical communication system for a quantum computer according to aspect 1 or 2, wherein the optical fiber includes an emission end that emits the optical control signal, and the emission ends are arranged on the end face of the image fiber so as to face the light receiving elements, respectively.

[0010] [4] Aspect 4 of the present invention may be an optical communication system for a quantum computer according to aspect 3, wherein the plurality of photodetectors are arranged two-dimensionally, and the plurality of emission ends are arranged two-dimensionally to correspond to the arrangement of the plurality of photodetectors.

[0011] [5] Aspect 5 of the present invention may be an optical communication system for a quantum computer according to aspect 3 or 4, wherein the image fiber includes a plurality of linear filling members that fill the gap between the inner surface of the tubular member and the optical fiber, and the plurality of filling members fix the optical fiber inside the tubular member so that the emission end faces the light receiving element.

[0012] [6] A sixth aspect of the present invention may be the optical communication system for a quantum computer according to the fifth aspect, wherein the filler member is a glass rod.

[0013] [7] Aspect 7 of the present invention may be an optical communication system for quantum computers according to any one of aspects 1 to 6, wherein the material constituting the tubular member is metal, glass, or ceramic.

[0014] [8] Aspect 8 of the present invention may be an optical communication system for a quantum computer according to any one of aspects 1 to 7, wherein the optical signal generator includes a carrier generator that generates a plurality of carrier waves, and a plurality of modulators that generate the plurality of optical control signals by superimposing the plurality of first microwave control signals on the plurality of carrier waves, respectively.

[0015] [9] A ninth aspect of the present invention may be an optical communication system for a quantum computer according to the eighth aspect, wherein the wavelengths of the plurality of carrier waves generated by the carrier wave generator are the same.

[0016]

[10] Aspect 10 of the present invention may be an optical communication system for quantum computers according to aspect 8 or 9, wherein the carrier wave generator includes a plurality of light-emitting elements that respectively generate the plurality of carrier waves.

[0017]

[11] Aspect 11 of the present invention may be an optical communication system for a quantum computer according to any one of aspects 1 to 7, wherein the optical signal generator comprises a laser driver and a plurality of light-emitting elements, the laser driver generates and transmits a plurality of modulated signals suitable for each of the plurality of light-emitting elements based on the plurality of first microwave control signals, and the plurality of light-emitting elements generate the plurality of optical control signals based on the plurality of modulated signals transmitted from the laser driver.

[0018]

[12] Aspect 12 of the present invention may be an optical communication system for a quantum computer according to aspect 11, wherein the plurality of light-emitting elements are arranged two-dimensionally, the optical fibers are arranged two-dimensionally to correspond to the arrangement of the plurality of light-emitting elements, and the optical fiber includes a plurality of incident ends into which the plurality of optical control signals are incident.

[0019]

[13] Aspect 13 of the present invention is a quantum computer comprising the quantum computer optical communication system of any one of aspects 1 to 12, a quantum circuit, and a refrigerator that houses the quantum circuit and cools the quantum circuit.

[0020]

[14] A fourteenth aspect of the present invention may be the quantum computer of the thirteenth aspect, further comprising a plurality of microwave generators that generate a plurality of first microwave control signals and transmit the plurality of first microwave control signals to the plurality of optical signal generators, respectively.

[0021]

[15] Aspect 15 of the present invention is a quantum computer according to aspect 13 or 14, wherein the refrigerator includes a plurality of freezing chambers and a plurality of metal plates arranged so as to separate the plurality of freezing chambers, the metal plates include through holes through which the image fibers are inserted, and the tubular member may be joined to the metal plates at the through holes.

[0022]

[16] A sixteenth aspect of the present invention is a method for manufacturing a quantum computer, comprising a first step of incorporating the quantum computer optical communication system according to any one of aspects 1 to 12 into a refrigerator.

[0023]

[17] Aspect 17 of the present invention may be a quantum computer manufacturing method according to aspect 16, wherein the refrigerator includes a plurality of freezing chambers and a plurality of metal plates arranged to separate the plurality of freezing chambers, the metal plates include through holes for inserting the image fibers, and the first step includes inserting the image fibers into the through holes and joining the metal plates and the tubular member at the through holes.

[0024] In the present invention, a plurality of optical control signals are transmitted by image fibers each having a plurality of optical fibers, which eliminates the need for multiplexers and demultiplexers, thereby enabling space saving.

[0025] FIG. 1 is a schematic diagram showing an example of a quantum computer according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. FIG. 3(a) is a perspective view showing a light-emitting substrate and a first single-core optical fiber according to the first embodiment of the present invention. FIG. 3(b) is a side view showing a light-emitting substrate and a first single-core optical fiber according to the first embodiment of the present invention. FIG. 3(c) is a perspective view showing an image fiber and a light-receiving substrate according to the first embodiment of the present invention. FIG. 3(d) is a side view showing an image fiber and a light-receiving substrate according to the first embodiment of the present invention. FIG. 4 is an enlarged cross-sectional view showing a portion IV in FIG. 2. FIG. 5 is a schematic diagram showing an example of a quantum computer according to a second embodiment of the present invention. FIG. 6 is a cross-sectional view showing a modified example of the connection structure between the image fiber and the modulator according to the first embodiment of the present invention. FIG. 7 is a cross-sectional view showing a modified example of the image fiber according to the first and second embodiments of the present invention.

[0026] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0027] First Embodiment

[0028] FIG. 1 is a schematic diagram showing an example of a quantum computer 1A according to this embodiment, and FIG. 2 is a cross-sectional view taken along line II-II in FIG.

[0029] As shown in Fig. 1, the quantum computer 1A in this embodiment includes a quantum circuit 2, a dilution refrigerator 3, and a control system 4. The quantum circuit 2 has a plurality of integrated quantum bits and input / output terminals for controlling and reading out the quantum bits. The quantum bits are, for example, superconducting, semiconductor spin, or annealing quantum bits, and operate in an extremely low temperature environment. The quantum circuit 2 in this embodiment performs calculations, initialization, etc. under the control of the control system 4.

[0030] The quantum circuit 2 is housed in a dilution refrigerator 3. The dilution refrigerator 3 is a refrigerator capable of cooling the interior to extremely low temperatures, and cools the quantum circuit 2. The dilution refrigerator 3 in this embodiment is, but is not limited to, a refrigerator that uses a mixed solution of helium-3 and helium-4. The dilution refrigerator 3 corresponds to an example of a "refrigerator" in an aspect of the present invention.

[0031] This dilution refrigerator 3 includes a plurality of freezing chambers 31 to 33 and a plurality of metal plates 34. Note that, although the number of freezing chambers in this embodiment is three, the number is not limited to this.

[0032] Freezing chambers 31 to 33 are closed spaces partitioned by a metal plate 34 and a cylindrical radiation plate (not shown), and the interiors can be cooled to several mK to several K. Although not particularly shown, freezing chambers 31 to 33 have a nested structure, with freezing chamber 31 being located on the outermost side, freezing chamber 32 being located between freezing chambers 31 and 33, and freezing chamber 33 being located on the innermost side. The diameters of freezing chambers 31 to 33 become smaller as they are positioned on the -Z direction side, with freezing chamber 31 having the largest diameter and freezing chamber 33 having the smallest diameter. Freezing chamber 33 is located inside freezing chamber 32, and freezing chamber 31 is located inside freezing chamber 32.

[0033] The internal temperatures of freezer compartments 31 to 33 decrease stepwise toward the center. That is, the internal temperature of freezer compartment 33 is the lowest among freezer compartments 31 to 33, the internal temperature of freezer compartment 32 is higher than the internal temperature of freezer compartment 33 but lower than the internal temperature of freezer compartment 31, and the internal temperature of freezer compartment 33 is the highest. The quantum circuit 2 is placed inside freezer compartment 33, which has the lowest temperature.

[0034] The plurality of metal plates 34 are arranged so as to separate the plurality of freezing chambers 31 to 33. As shown in Fig. 2, the metal plates 34 include through holes 341 for inserting image fibers 64A, which will be described later.

[0035] 1, the control system 4 is a system for controlling the quantum bits included in the quantum circuit 2. In this embodiment, the control system 4 controls the quantum bits using a control signal (a second microwave control signal, which will be described later) generated based on microwaves. Although not specifically shown, the quantum computer 1A also includes an output system that outputs an output signal from the quantum circuit 2 in response to the second microwave control signal.

[0036] The control system 4 in this embodiment includes a microwave generating unit 5 and an optical communication system 6A. The microwave generating unit 5 generates a first microwave control signal and transmits the first microwave control signal to the optical communication system 6A. The microwave generating unit 5 in this embodiment includes a plurality of microwave generators 51. Each microwave generator 51 is electrically connected to a modulator 63, which will be described later, and outputs a first microwave control signal to the modulator 63.

[0037] The optical communication system 6A is a system for outputting a second microwave control signal to the quantum circuit 2 by means of a carrier wave. This optical communication system 6A is provided from the outside to the inside of the dilution refrigerator 3. The optical communication system 6A corresponds to an example of an "optical communication system for a quantum computer" in an aspect of the present invention.

[0038] The optical communication system 6A in this embodiment includes a light emitting substrate 61, a plurality of first single-core optical fibers 62, a plurality of modulators 63, an image fiber 64A, and a light receiving substrate 65. The light emitting substrate 61, the plurality of first single-core optical fibers 62, and the plurality of modulators 63 correspond to an example of an "optical signal generator" in an aspect of the present invention.

[0039] Figure 3(a) is an oblique view showing the light emitting substrate 61 and the first single-core optical fiber 62 in this embodiment, and Figure 3(b) is a side view showing the light emitting substrate 61 and the first single-core optical fiber 62 in an embodiment of the present invention.

[0040] As shown in Figures 1, 3(a), and 3(b), the light-emitting substrate 61 is disposed outside the dilution refrigerator 3. This light-emitting substrate 61 includes a first substrate 611 and a plurality of light-emitting elements 612. The first substrate 611 is a circuit board. In this embodiment, four light-emitting elements 612 are mounted on a main surface of the first substrate 611. Such a light-emitting substrate 61 corresponds to an example of a "carrier wave generator" in accordance with an aspect of the present invention.

[0041] The plurality of light-emitting elements 612 are two-dimensionally arranged on the main surface of the first substrate 611. Specifically, the plurality of light-emitting elements 612 in this embodiment are arranged in a lattice pattern of two rows and two columns. The number of light-emitting elements 612 is not particularly limited as long as it is two or more. Furthermore, the arrangement of the plurality of light-emitting elements 612 is not limited to a lattice pattern as long as it is a two-dimensional arrangement. For example, the plurality of light-emitting elements 612 may be arranged irregularly.

[0042] The light-emitting elements 612 in this embodiment generate light of a single wavelength. By using light-emitting elements 612 that generate light of a single wavelength in this manner, costs can be reduced compared to using a light source that generates light of multiple wavelengths. Furthermore, in this embodiment, the wavelengths of light generated by the light-emitting elements 612 are the same. However, the wavelengths of light generated by the light-emitting elements 612 may be different from each other. Examples of such light-emitting elements 612 include light-emitting diodes (LEDs) and laser diodes (LDs) such as vertical cavity surface-emitting lasers (VCSELs).

[0043] The light-emitting elements 612 in this embodiment are elements capable of surface emission, and can emit light in a direction perpendicular to the main surface of the first substrate 611 in this embodiment. Light generated by each light-emitting element 612 is used as a carrier wave that carries a signal. Note that the light-emitting elements 612 may also be elements capable of edge emission. In this case, the light-emitting elements 612 emit light in a direction perpendicular to the edge surface (side surface) of the first substrate 611.

[0044] 1 , the plurality of first single-core optical fibers 62 are respectively arranged between the light-emitting element 612 and the modulator 63 outside the dilution refrigerator 3. The first single-core optical fibers 62 transmit the light emitted from the light-emitting substrate 61 to the modulator 63.

[0045] 3( a) and 3(b), the number of the plurality of first single-core optical fibers 62 is the same as the number of the light-emitting elements 612, and the first single-core optical fibers 62 are arranged such that the incident ends 621 of the first single-core optical fibers 62 face the light-emitting elements 612. As a result, the light emitted from the light-emitting elements 612 enters the inside of the first single-core optical fiber 62 from the incident ends 621.

[0046] The incident end 621 of the first single-core optical fiber 62 does not have to face the light-emitting element 612. When the incident end 621 does not face the light-emitting element 612, light emitted from the light-emitting element 612 may be guided to the incident end 621 by an optical element such as a mirror. Also, the light-emitting substrate 61 may be provided with a single light-emitting element, and multiple first single-core optical fibers 62 may be arranged to face this single light-emitting element. In other words, since the light generated by the light-emitting element has a single wavelength, multiple first single-core optical fibers 62 may share one light source.

[0047] 1, the multiple modulators 63 are arranged outside the dilution refrigerator 3. The number of the modulators 63 is the same as the number of the first single-core optical fibers 62. To each of the modulators 63, an exit end 622 of the first single-core optical fiber 62 is connected.

[0048] The modulator 63 modulates the carrier wave input from the exit end 622 of the first single-core optical fiber 62 to generate an optical control signal. The modulator 63 in this embodiment is an electro-optic modulator (EOM). The modulator 63 generates an optical control signal by superimposing the first microwave control signal input from the microwave generator 51 on the light (carrier wave) input from the first single-core optical fiber 62. Then, the modulator 63 outputs the generated optical control signal to the second single-core optical fiber 645A of the image fiber 64A.

[0049] The image fiber 64A is arranged from the outside to the inside of the dilution refrigerator 3. That is, in this embodiment, the image fiber 64A using multiple single-core optical fibers is used as a means for transmitting an optical control signal from the outside to the inside of the dilution refrigerator 3.

[0050] The above-mentioned Patent Document 1 and Non-Patent Document 1 also describe the use of coaxial cables as a means for transmitting electrical control signals inside the dilution refrigerator, but for integration of 1000 quantum bits or more, the wiring volume and heat inflow of the coaxial cables are too large. Note that heat inflow refers to the inflow of heat between adjacent freezing chambers of a multi-stage dilution refrigerator.

[0051] On the other hand, the image fiber 64A using optical fiber can reduce the wiring volume compared to a coaxial cable. Furthermore, since the heat inflow into the dilution refrigerator 3 through the image fiber 64A is much smaller than the heat inflow through a coaxial cable, this embodiment can significantly reduce the heat inflow into the dilution refrigerator 3, enabling stable operation of the quantum circuit 2. For example, the thermal conductivity of the glass that makes up the optical fiber is about 1 / 400 of the thermal conductivity of the copper that makes up the coaxial cable, so the heat inflow can be significantly reduced. Furthermore, by significantly reducing the heat inflow, the load on the dilution refrigerator 3 can also be reduced.

[0052] The image fiber 64A includes a tubular member 641, a plurality of second single-core optical fibers 645A, and a glass rod 648. The second single-core optical fiber 645A corresponds to an example of the "optical fiber" in this aspect of the present invention, and the glass rod 648 corresponds to an example of the "filler member" in this aspect of the present invention.

[0053] 2, the tubular member 641 in this embodiment is a cylindrical member. The material constituting the tubular member 641 in this embodiment is not particularly limited, but examples thereof include resin, metal, glass, and ceramic.

[0054] These materials shrink less in a low-temperature environment than resin materials, and therefore the lateral pressure applied to the second single-core optical fiber 645A can be reduced, thereby suppressing an increase in transmission loss in the second single-core optical fiber 645A.

[0055] In this embodiment, the tubular member 641 has a single-layer structure, but is not limited to this. The tubular member 641 may have a multi-layer structure, for example, in which a metal layer is coated on the outer surface of a glass tube or a ceramic tube.

[0056] 1 , this tubular member 641 extends from the outside to the inside of the dilution refrigerator 3, and is inserted into the through-holes 341 of the two metal plates 34 inside the dilution refrigerator 3. In this embodiment, a first end 642 of the tubular member 641 is exposed to the outside of the dilution refrigerator 3, and a second end 643 of the tubular member 641 faces a light-receiving substrate 65 (described below) inside the freezing chamber 33.

[0057] 2, an outer peripheral surface 644 of the tubular member 641 is joined and fixed to the metal plate 34 at the through hole 341. The outer peripheral surface 644 may be joined directly to the metal plate 34 by welding, indirectly to the metal plate 34 via brazing, or indirectly to the metal plate 34 via a resin adhesive or the like, for example.

[0058] In this way, since the outer surface 644 of the tubular member 641 is joined to the metal plate 34, no gap is formed between the image fiber 64A and the metal plate 34, and therefore the heat flow between the freezer compartments 31 to 33 through the through hole 341 can be further reduced.

[0059] A plurality of second single-core optical fibers 645A are housed in this tubular member 641. The second single-core optical fibers 645A are small-diameter single-core optical fibers, and extend along the extending direction of the tubular member 641. The characteristics of the second single-core optical fibers 645A are set to characteristics suitable for communication wavelengths.

[0060] Examples of such a second single-core optical fiber 645A include, but are not limited to, a bare fiber, a fiber strand, and a fiber core. For example, a bare fiber is composed of a cylindrical core and a cylindrical cladding that covers the outer surface of the core. Both the core and the cladding are made of glass materials. A fiber strand is composed of a bare fiber and an ultraviolet-cured resin layer that covers the outer surface of the bare fiber. A fiber core is composed of a fiber strand and a thermoplastic resin layer that covers the outer surface of the fiber strand.

[0061] In this embodiment, the diameter of the second single-core optical fiber 645A is smaller than the diameter of the first single-core optical fiber 62. For example, the diameter of the second single-core optical fiber 645A is not particularly limited, but may be several tens of μm. In this way, by using a single-core optical fiber with a small diameter as the second single-core optical fiber 645A used in the image fiber 64A, the volume of the image fiber 64A can be further reduced.

[0062] As shown in FIG. 1, the input end 646 of the second single-core optical fiber 645A is connected to the modulator 63, and the optical control signal generated by the modulator 63 is input from this input end 646 to the second single-core optical fiber 645A.

[0063] FIG. 3(c) is a perspective view showing the image fiber 64A and the light receiving substrate 65 in this embodiment, and FIG. 3(d) is a side view showing the image fiber 64A and the light receiving substrate 65 in this embodiment.

[0064] 3(c) and 3(d), the emission ends 647 of the second single-core optical fibers 645A are also two-dimensionally arranged on the end face of the image fiber 64A in the same arrangement as in the cross section shown in Fig. 2. Specifically, the plurality of emission ends 647 in this embodiment are arranged in a lattice pattern of two rows and two columns so as to correspond to the positions of the light-receiving elements 652 described below, and face the light-receiving elements 652 on the end face of the image fiber 64A.

[0065] Fig. 4 is an enlarged cross-sectional view showing a portion IV in Fig. 2. As shown in Fig. 4, the glass rod 648 is a rod-shaped glass member extending along the extending direction of the second single-core optical fiber 645A. The refractive index of this glass rod 648 is equal to or less than the refractive index of the cladding of the second single-core optical fiber 645A. The glass rod 648 is arranged so as to fill the gap between the tubular member 641 and the second single-core optical fiber 645A.

[0066] The glass rods 648 are arranged such that some of the glass rods 648 are in contact with the outer circumferential surface of the second single-core optical fiber 645A. At least some of the glass rods 648 are fused to other glass rods 648, and the plurality of glass rods 648 are fixed to one another. In this way, the plurality of glass rods 648 fix the second single-core optical fiber 645A.

[0067] In this embodiment, by using a glass rod 648 to fix the second single-core optical fiber 645A inside the tubular member 641, the image fiber 64A can be made to have less heat inflow compared to a coaxial cable.

[0068] 1, 3(c), and 3(d), the light-receiving substrate 65 is disposed inside the freezing chamber 33 so as to face the end face of the image fiber 64A. As shown in FIGS. 3(c) and 3(d), the light-receiving substrate 65 includes a second substrate 651 and a plurality of light-receiving elements 652.

[0069] The second substrate 651 is a circuit board. In this embodiment, four light receiving elements 652, the same number as the light emitting elements 612, are mounted on the main surface of the second substrate 651. The multiple light receiving elements 652 are two-dimensionally arranged on the main surface of the second substrate 651. Specifically, in this embodiment, the multiple light receiving elements 652 are arranged in a lattice pattern of two rows and two columns. The number of light receiving elements 652 is not particularly limited as long as it is two or more. The multiple light receiving elements 652 may also be arranged irregularly.

[0070] The light receiving element 652 converts an optical signal into an electrical signal and outputs the electrical signal to the quantum circuit 2. Such a light receiving element 652 is not particularly limited, but examples thereof include a PIN photodiode and an avalanche photodiode.

[0071] This light-receiving element 652 is electrically connected to the quantum bit of the quantum circuit 2 via an electric circuit or the like. The light-receiving element 652 converts the control signal made up of light into a control signal made up of electricity (a second microwave control signal) and outputs it to the quantum circuit 2. In this way, the quantum bit of the quantum circuit 2 is controlled.

[0072] In the present embodiment as described above, multiple optical control signals are individually transmitted through the multiple second single-core optical fibers 645A of the image fiber 64A, eliminating the need to convert the optical control signals to a WDM system. This eliminates the need for a demultiplexer and a multiplexer, reducing the volume occupied by the optical communication system 6A and enabling space saving. Furthermore, eliminating the need for a demultiplexer and a multiplexer reduces costs and eliminates insertion loss in the demultiplexer and the multiplexer.

[0073] In addition, in this embodiment, the multiple light-emitting elements 612, the multiple second single-core optical fibers 645A, and the multiple light-receiving elements 652 are all integrated, thereby further reducing the space required for the optical communication system 6A.

[0074] Next, a method for manufacturing the quantum computer 1A of this embodiment will be described. The method for manufacturing the quantum computer 1A of this embodiment includes a first step of incorporating an optical communication system 6A as shown in FIG.

[0075] Specifically, this first step includes inserting the image fiber 64A into the through-hole 341 of the metal plate 34 of the dilution refrigerator 3, and joining the metal plate 34 and the tubular member 641 at the through-hole 341. Note that examples of the method for joining the metal plate 34 and the tubular member 641 include the above-mentioned method of joining them directly by welding, the indirect brazing method, and the indirect bonding method using an adhesive.

[0076] Second Embodiment

[0077] 5 is a schematic diagram showing an example of a quantum computer 1B according to the second embodiment. The quantum computer 1B according to the second embodiment differs from the first embodiment in that it includes a direct modulation optical communication system 6B. Only the differences between the quantum computer 1B according to the second embodiment and the first embodiment will be described below, and parts having the same configuration as the first embodiment will be assigned the same reference numerals and their description will be omitted.

[0078] The optical communication system 6B in the second embodiment includes, instead of the external modulation type modulator 63, a laser driver 68 electrically connected to the microwave generating unit 5, and a light emitting substrate 61 electrically connected to the laser driver 68. The laser driver 68 and the light emitting substrate 61 correspond to an example of the "optical signal generator" in the aspects of the present invention.

[0079] The laser driver 68 receives a plurality of first microwave control signals from the plurality of microwave generators 51 of the microwave generating unit 5. The laser driver 68 generates and transmits modulation signals suitable for the plurality of light-emitting elements 612 of the light-emitting substrate 61 based on the plurality of first microwave control signals received.

[0080] The light emitting substrate 61 in the second embodiment is electrically connected to a laser driver 68. Each light emitting element 612 of the light emitting substrate 61 generates an optical control signal based on each modulation signal transmitted from the laser driver 68.

[0081] The light-emitting element 612 in the second embodiment faces the first end 642 of the image fiber 64A. Therefore, the optical control signal emitted from the light-emitting substrate 61 is incident on the second single-core optical fiber 645A at the first end 642. Note that the light-emitting element 612 does not have to face the first end 642. In that case, the optical control signal emitted from the light-emitting element 612 may be guided to the second single-core optical fiber 645A by an optical element such as a mirror.

[0082] In the second embodiment, similarly to the first embodiment, multiple optical control signals are individually transmitted through the multiple second single-core optical fibers 645A of the image fiber 64A, and therefore conversion of the optical control signals to the WDM system is not required. Therefore, a demultiplexer and a multiplexer are not required, so the volume occupied by the optical communication system 6A can be reduced, thereby achieving space savings. Furthermore, since a demultiplexer and a multiplexer are not required, costs can be reduced, and insertion loss in the demultiplexer and the multiplexer is not generated.

[0083] Furthermore, in the second embodiment, the structure of the optical communication system 6B inside the dilution refrigerator 3 is the same as that in the first embodiment. Therefore, the quantum computer 1B in the second embodiment can be manufactured by the same manufacturing method as the quantum computer 1A in the first embodiment.

[0084] It should be noted that the above-described embodiments have been described to facilitate understanding of the present invention, and are not intended to limit the present invention. Therefore, the elements disclosed in the above embodiments are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0085] For example, in the first embodiment, the second single-core optical fiber 645A of the image fiber 64A is directly connected to the modulator 63, but the present invention is not limited to this.

[0086] Fig. 6 is a cross-sectional view showing a modified example of the connection structure between the image fiber 64A and the modulator 63 (see Fig. 1) in the first embodiment. As shown in Fig. 6, a connector 66 may be interposed between the second single-core optical fiber 645A and the modulator 63. This connector 66 is a FiFo (Fan-in / Fan-out) device. This connector 66 includes a capillary 661 and a plurality of third single-core optical fibers 662.

[0087] The capillary 661 is made of a material such as glass. The capillary 661 holds a plurality of third single-core optical fibers 662.

[0088] The third single-core optical fiber 662 is a single-core optical fiber. The third single-core optical fiber 662 has an interposed portion 663 that is thinned toward the tip by etching, and the tip of the third single-core optical fiber 662 is fixed in the capillary 661 with an adhesive. The number of third single-core optical fibers 662 is the same as the number of modulators 63. One end of the third single-core optical fiber 662 is optically connected to the modulator 63, and the other end of the third single-core optical fiber 662 is optically connected to the second single-core optical fiber 645A of the image fiber 64A.

[0089] Because a Fifo device such as the connector 66 is a fiber-type device, it is small and easy to integrate. Therefore, compared to when a demultiplexer and a multiplexer are used, this modification also allows for space saving in the optical communication systems 6A and 6B. Furthermore, since the insertion loss of a Fifo device is smaller than when a demultiplexer and a multiplexer are used, it is also possible to reduce the insertion loss. Furthermore, such a connector 66 may be interposed between the image fiber 64A and the light-receiving substrate 65.

[0090] In the second embodiment, the connector 66 may be interposed between the image fiber 64A and the light-emitting substrate 61. Similarly, the connector 66 may be interposed between the image fiber 64A and the light-receiving substrate 65.

[0091] Furthermore, in the first and second embodiments, for convenience, an example is shown in which four control signals are input to the quantum circuit 2, but the number of control signals, the number of light-emitting elements 612, the number of first and second single-core optical fibers 62, 645A, the number of modulators 63, and the number of light-receiving elements 652 are not limited to this. The number of wirings for transmitting the control signals can be changed depending on the number of quantum bits and is not particularly limited, but may be about two to four per quantum bit.

[0092] In particular, the image fiber 64A in the first and second embodiments transmits one optical control signal through one second single-core optical fiber 645A, but is not limited to this. As will be described in the modified example shown in Fig. 7 below, one optical control signal may be transmitted through multiple second single-core optical fibers 645B.

[0093] Fig. 7 is a cross-sectional view showing a modified example of the imaging fiber 64A in the first and second embodiments. As shown in Fig. 7, the imaging fiber 64B includes a tubular member 641 and a plurality of second single-core optical fibers 645B.

[0094] The tubular member 641 has the same configuration as the image fiber 64A described above. The inside of this tubular member 641 is filled with a plurality of second single-core optical fibers 645B. The second single-core optical fibers 645B are, but are not particularly limited to, bare optical fibers. The diameter of these bare optical fibers is equal to the diameter of the light-emitting surface of the light-emitting element 612 (in this example, the optical control signal S in FIG. 7). １ ~S ４ The diameter of the electrode is smaller than that of the electrode itself, for example, several micrometers.

[0095] Such an image fiber 64B is an image transmission path, and can transmit the image of the received multiple optical control signals as is, and can also transmit multiple optical control signals without changing the relative positional relationship between the multiple optical control signals. For example, if this image fiber 64B is applied to the image fiber 64A shown in the second embodiment (see FIG. 5), the multiple optical control signals S １ ~S ４ The positional relationship of the plurality of light-emitting elements 612 corresponds to the positional relationship of the plurality of light-emitting elements 612. Similarly, the plurality of light control signals S １ ~S ４ The positional relationship of the light receiving elements 652 corresponds to the positional relationship of the light receiving elements 652 (see FIG. 3C).

[0096] In the first and second embodiments, for convenience, the optical communication systems 6A, 6B are illustrated as including one image fiber 64A, 64B, but the present invention is not limited to this. The optical communication systems 6A, 6B may include a plurality of image fibers 64A, 64B, and the plurality of image fibers 64A, 64B may be inserted into the through holes 341 of the respective metal plates 34.

[0097] Although the first and second embodiments illustrate the case where a plurality of light-emitting elements 612 are provided as light sources, the present invention is not limited to this. For example, a single light source and a splitter may be provided, and the light emitted from the single light source may be split by the splitter into a plurality of carrier waves having the same wavelength to generate an optical control signal.

[0098] 1A, 1B...Quantum computer 2...Quantum circuit 3...Dilution refrigerator 31-33...Freezing chamber 34...Metal plate 341...Through-hole 4...Control system 5...Microwave generating unit 51...Microwave generator 6A, 6B...Optical communication system 61...Light-emitting substrate 611...First substrate 612...Light-emitting element 62...First single-core optical fiber 621...Input end 622...Output end 63...Modulator 64A, 64B...Image fiber 641...Tubular member 642...First end 643...Second end 644...Outer surface 645A, 645B...Second single-core optical fiber 646...Input end 647...Output end 648...Glass rod 65...Light-receiving substrate 651...Second substrate 652...Light-receiving element 66...Connector 661...Capillary 662...Third single-core optical fiber 663...Interposition portion

Claims

1. An optical communication system for a quantum computer comprising: an optical signal generator that generates a plurality of optical control signals based on a plurality of first microwave control signals; an image fiber including a plurality of optical fibers that transmit the plurality of optical control signals, respectively, and a tubular member that houses the plurality of optical fibers; and a plurality of photodetectors that receive the plurality of optical control signals from the plurality of optical fibers, convert the plurality of optical control signals into a plurality of second microwave control signals, respectively, and transmit them to a quantum circuit.

2. An optical communication system for a quantum computer according to claim 1, wherein at least a portion of the image fiber is disposed inside a refrigerator of the quantum computer.

3. An optical communication system for a quantum computer according to claim 1 or 2, wherein the optical fiber includes an emission end that emits the optical control signal, and the emission ends are arranged on the end face of the image fiber so as to face the light-receiving elements, respectively.

4. An optical communication system for a quantum computer according to claim 3, wherein the plurality of light receiving elements are arranged two-dimensionally, and the plurality of emission ends are arranged two-dimensionally to correspond to the arrangement of the plurality of light receiving elements.

5. An optical communication system for a quantum computer according to claim 3 or 4, wherein the image fiber includes a plurality of linear filling members that fill the gap between the inner surface of the tubular member and the optical fiber, and the plurality of filling members fix the optical fiber inside the tubular member so that the emission end faces the light-receiving element.

6. An optical communication system for a quantum computer according to claim 5, wherein the filling member is a glass rod.

7. An optical communication system for a quantum computer according to any one of claims 1 to 6, wherein the material constituting the tubular member is metal, glass, or ceramic.

8. An optical communication system for a quantum computer according to any one of claims 1 to 7, wherein the optical signal generator includes: a carrier generator that generates a plurality of carrier waves; and a plurality of modulators that generate the plurality of optical control signals by superimposing the plurality of first microwave control signals respectively on the plurality of carrier waves.

9. An optical communication system for a quantum computer according to claim 8, wherein the wavelengths of the plurality of carrier waves generated by the carrier wave generator are the same.

10. An optical communication system for a quantum computer according to claim 8 or 9, wherein the carrier wave generator comprises a plurality of light-emitting elements that respectively generate the plurality of carrier waves.

11. An optical communication system for a quantum computer according to any one of claims 1 to 7, wherein the optical signal generator comprises a laser driver and a plurality of light-emitting elements, the laser driver generates and transmits a plurality of modulated signals suited to each of the plurality of light-emitting elements based on the plurality of first microwave control signals, and the plurality of light-emitting elements generate the plurality of optical control signals based on the plurality of modulated signals transmitted from the laser driver.

12. An optical communication system for a quantum computer as described in claim 11, wherein the plurality of light-emitting elements are arranged two-dimensionally, and the optical fibers are arranged two-dimensionally to correspond to the arrangement of the plurality of light-emitting elements, and include a plurality of input ends to which the plurality of optical control signals are input.

13. A quantum computer comprising: an optical communication system for a quantum computer according to any one of claims 1 to 12; a quantum circuit; and a refrigerator that houses the quantum circuit and cools the quantum circuit.

14. The quantum computer of claim 13, further comprising a plurality of microwave generators that generate a plurality of first microwave control signals and transmit the plurality of first microwave control signals to the plurality of optical signal generators, respectively.

15. A quantum computer as set forth in claim 13 or 14, wherein the refrigerator includes a plurality of freezing chambers and a plurality of metal plates arranged to separate the plurality of freezing chambers, the metal plates include through holes for inserting the image fibers, and the tubular member is joined to the metal plates at the through holes.

16. A method for manufacturing a quantum computer, comprising a first step of incorporating the optical communication system for a quantum computer according to any one of claims 1 to 12 into a refrigerator.

17. A method for manufacturing a quantum computer as described in claim 16, wherein the refrigerator includes a plurality of freezing chambers and a plurality of metal plates arranged to separate the plurality of freezing chambers, the metal plates include through holes for inserting the image fibers, and the first step includes inserting the image fibers into the through holes and joining the metal plates and the tubular member at the through holes.

Images