Quantum converter and quantum conversion method

Abstract

To provide a quantum converter and a quantum conversion method capable of improving conversion efficiency even when light with low loss in an optical fiber is used.SOLUTION: The quantum transducer includes a three dimensional cavity resonator, and a nonmagnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film that are provided in the three dimensional cavity resonator and are stacked on each other, A laminate including an interface between the first insulator film and the second insulator film, a magnetic field application unit configured to apply a magnetic field including a component perpendicular to the interface to the laminate, and a microwave transmission and reception unit configured to transmit and receive microwaves to and from the laminate, wherein the first insulator film and the second insulator film do not include a topological insulator, the second insulator film has an easy magnetization axis along a first axis perpendicular to the interface, and the laminate is irradiated with laser light from a direction inclined with respect to the first axis. Quantum converters can be used, for example, in quantum computing.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to quantum transducers and methods of quantum transformation. [Background technology]

[0002] Quantum computers may perform quantum conversion between microwave photons and optical photons, and quantum converters involving topological insulators have been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-546863 [Patent Document 2] Special Publication No. 2022-538247 [Patent Document 3] U.S. Patent Application Publication No. 2021 / 0114864 [Patent Document 4] US Patent Application Publication No. 2020 / 0412457 Summary of the Invention [Problem to be solved by the invention]

[0004] Quantum converters containing topological insulators can improve conversion efficiency, but the frequencies of light that can be used are limited, and the loss of that light in optical fibers is large.

[0005] An object of the present disclosure is to provide a quantum converter and a quantum conversion method that can improve conversion efficiency even when light with low loss in an optical fiber is used. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a quantum converter comprising: a three-dimensional cavity resonator; a stack provided within the three-dimensional cavity resonator, the stack including a non-magnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film stacked on top of each other, the stack having an interface between the first insulator film and the second insulator film; a magnetic field application unit that applies a magnetic field including a component perpendicular to the interface to the stack; and a microwave transceiver unit that transmits and receives microwaves to and from the stack, wherein the first insulator film and the second insulator film do not include a topological insulator, the second insulator film has an easy axis of magnetization along a first axis perpendicular to the interface, and the stack is irradiated with laser light from a direction tilted from the first axis. [Effects of the Invention]

[0007] According to the present disclosure, conversion efficiency can be improved even when light with low loss in optical fibers is used. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a quantum converter according to a first embodiment. [Figure 2] 1 is a schematic diagram illustrating the theory of quantum transformation by a quantum transformer according to a first embodiment. FIG. [Figure 3] FIG. 4 is a diagram showing the relationship between the number of second insulator films and conversion efficiency in the first embodiment. [Figure 4] FIG. 4 is a diagram showing the relationship between thickness parameters and conversion efficiency in the first embodiment. [Figure 5] FIG. 10 is a schematic diagram showing a quantum converter according to a second embodiment. [Figure 6] FIG. 10 is a schematic diagram showing a quantum converter according to a third embodiment. [Figure 7] FIG. 10 is a schematic diagram illustrating the theory of quantum transformation by a quantum transformer according to a third embodiment. [Figure 8] FIG. 10 is a diagram showing the relationship between the number of second insulator films and conversion efficiency in the third embodiment. [Figure 9] FIG. 11 is a diagram showing the relationship between thickness parameters and conversion efficiency in the third embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a quantum converter according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description may be omitted.

[0010] (First embodiment) A first embodiment will be described. The first embodiment relates to a quantum converter. The quantum converter according to the first embodiment converts microwave photons into optical photons. FIG. 1 is a schematic diagram showing the quantum converter according to the first embodiment.

[0011] As shown in FIG. 1, the quantum converter 100 according to the first embodiment includes a microwave resonator 30, a laminate 10, an N pole 51, an S pole 52, an antenna 40, and an optical resonator 60.

[0012] The microwave resonator 30 is provided with an inlet 31 and an outlet 32. The laminate 10 is fixed inside the microwave resonator 30 by a support member 35. An optical fiber is connected to the inlet 31, and laser light L1 is introduced from the outside through the inlet 31, and the laser light L1 is irradiated toward the laminate 10. An optical fiber is connected to the outlet 32, and laser light L2 that has passed through the laminate 10 is output to the outside through the outlet 32. The laser light L1 and L2 are circularly polarized laser light. The microwave resonator 30 is an example of a three-dimensional cavity resonator.

[0013] The optical resonator 60 has a first mirror 61 and a second mirror 62. The first mirror 61 is provided between the inlet 31 and the laminate 10, and the second mirror 62 is provided between the outlet 32 ​​and the laminate 10. The optical resonator 60 amplifies the circularly polarized laser light.

[0014] The stack 10 includes a first insulator film 11 and a second insulator film 12 stacked on top of each other. The first insulator film 11 and the second insulator film 12 are in contact with each other, and the stack 10 has an interface 13 between the first insulator film 11 and the second insulator film 12. The first insulator film 11 and the second insulator film 12 do not contain a topological insulator.

[0015] The first insulator film 11 is a non-magnetic insulator film and does not contain a topological insulator. For example, the first insulator film 11 contains SrTiO3, Al2O3, or both. The relative permeability of the first insulator film 11 is 1.02 or less.

[0016] The second insulator film 12 is a ferromagnetic insulator film. The second insulator film 12 has an easy axis of magnetization along a first axis perpendicular to the interface 13. The laser beams L1 and L2 have components perpendicular to the easy axis of magnetization of the ferromagnetic insulator contained in the second insulator film 12. For example, the second insulator film 12 is made of Y3Fe5O 12 (YIG), Tm3Fe5O 12 (TIG), EuS, Cr2Ge2Te6 or BaFe 12 O 19 1, the arrows in the second insulator film 12 indicate the direction of spin in the ferromagnetic insulator.

[0017] The N pole 51 and the S pole 52 are provided on the outer wall surface of the microwave resonator 30. A magnetic field H directed from the N pole 51 to the S pole 52 is generated between the N pole 51 and the S pole 52. The N pole 51 and the S pole 52 act as magnetic field application units and apply the magnetic field H including a component parallel to the first axis to the laminate 10.

[0018] The antenna 40 is provided on the outer wall surface of the microwave resonator 30. The antenna 40 serves as a microwave transmitting / receiving unit, transmitting and receiving microwaves to and from the laminate 10. In this embodiment, the antenna 40 transmits a microwave MW1 input from the outside to the laminate 10.

[0019] The polarization and the like of the laser light L2 output to the outside through the output port 32 are detected. In this way, the microwave photons of the microwave MW1 irradiated onto the laminate 10 through the antenna 40 are quantum converted into optical photons. That is, the quantum conversion method using the quantum converter 100 includes a step of irradiating the laser light L1 onto the laminate 10 from a direction tilted from the first axis. For example, microwave photons having a frequency of about 1 GHz to 100 GHz are converted into optical photons having a frequency of about 200 THz.

[0020] Here, we will explain the theory of quantum transformation by the quantum converter 100. Fig. 2 is a schematic diagram showing the theory of quantum transformation by the quantum converter 100 according to the first embodiment. The parameters in Fig. 2 represent the items shown in Table 1.

[0021] [Table 1]

[0022] The interaction ζ between photons and ferromagnetic magnons in the optical resonator 60 is expressed by equation (1), and the interaction g between photons and ferromagnetic magnons in the microwave resonator 30 is expressed by equation (2).

[0023]

number

[0024] N in formulas (1) and (2) L indicates the number of second insulating films 12. ζ0 in formula (1) is the number of second insulating films 12 with a volume of 1 mm 3 The strength of the interaction when the second insulating film 12 is a single layer film of 1 mm 3 The thickness parameter D in equations (1) and (2) indicates the strength of the interaction when the film is a single layer. γ is the number of spins N contained in the second insulator film 12 S The volume of the second insulating film 12 is 1 mm 3 If N is the number of spins involved, S0 This is the value obtained by dividing by

[0025] The conversion efficiency η is expressed by the formula (3). The microwave susceptibility χ in the formula (3) e , magnon susceptibility χ m and optical susceptibility χ o δω o are expressed by equations (4) to (6), respectively, and δω o is expressed by equation (7).

[0026]

number

[0027] When the resonance condition is satisfied, i.e., the frequency ω of the itinerant microwave photons and the resonant frequency ω of the microwave resonator 30 e and the resonant frequency ω of the ferromagnetic insulator m and δω o When the number N of the second insulating films 12 is equal to the number N of the second insulating films 12, as shown in FIG. L 3 shows the relationship between the number N of the second insulating films 12 in the first embodiment. L 1 is a diagram showing the relationship between the number of second insulator films 12 and the conversion efficiency η. In this way, the quantum converter 100 can quantum convert microwave photons of the microwave MW1 into optical photons. Furthermore, in the quantum converter 100, the conversion efficiency η is L Therefore, the number N of the second insulating films 12 is proportional to the square of L The larger the thickness parameter D, the higher the conversion efficiency η. γ is 0.001, ζ0 / 2π is about 20kHz, γ / 2π is about 3MHz, g0 / 2π is about 20MHz, κ o,e / 2π is about 50MHz, κ e,e / 2π is about 150MHz, κ o,i / 2π is about 1450MHz, κ e,i / 2π is assumed to be around 100 MHz.

[0028] Furthermore, since the first insulator film 11 and the second insulator film 12 do not contain a topological insulator, light with a frequency of about 200 THz can be used, which means that light with low loss during transmission through an optical fiber can be used.

[0029] Number N of second insulating films 12 L If is constant, the thickness parameter D γ The relationship between the thickness parameter D and the conversion efficiency η is shown in FIG. γ 4 shows the relationship between the thickness parameter D and the conversion efficiency η. γ above a certain threshold, the thickness parameter D γ The smaller the thickness parameter D, the higher the conversion efficiency η. γ The thickness of the second insulating film 12 corresponding to the threshold value is about 100 nm. L is 10, ζ0 / 2π is about 20kHz, γ / 2π is about 3MHz, g0 / 2π is about 20MHz, κ o,e / 2π is about 50MHz, κ e,e / 2π is about 150MHz, κ o,i / 2π is about 1450MHz, κ e,i / 2π is assumed to be around 100 MHz.

[0030] (Second embodiment) A second embodiment will now be described. The second embodiment relates to a quantum converter. The quantum converter according to the second embodiment converts optical photons into microwave photons. Figure 5 is a schematic diagram showing the quantum converter according to the second embodiment.

[0031] As shown in FIG. 5, in the quantum converter 200 according to the second embodiment, laser light L3 is irradiated from the outside toward the stack 10 through an inlet 31. An outlet 32 ​​does not necessarily have to be provided. The laser light L3 includes linearly polarized laser light and circularly polarized laser light. The linearly polarized laser light and the circularly polarized laser light have components perpendicular to the easy axis of magnetization of the ferromagnetic insulator included in the second insulator film 12. An optical resonator 60 amplifies the circularly polarized laser light.

[0032] Other configurations of the second embodiment are similar to those of the first embodiment.

[0033] In the second embodiment, microwaves MW2 corresponding to the polarization of laser light L3 are emitted from the laminate 10, and the antenna 40 outputs the microwaves MW2 to the outside. In this way, optical photons of the laser light L3 irradiated onto the laminate 10 are quantum converted into microwave photons of the microwaves MW2. That is, the quantum conversion method using the quantum converter 200 includes a step of irradiating the laminate 10 with laser light L3 from a direction tilted from the first axis. For example, optical photons with a frequency of about 200 THz are converted into microwave photons with a frequency of about 1 GHz to 100 GHz.

[0034] The second embodiment can also provide the same effects as the first embodiment.

[0035] (Third embodiment) A third embodiment will be described. The third embodiment differs from the first embodiment mainly in the configuration of the stack. Fig. 6 is a schematic diagram showing a quantum converter according to the third embodiment.

[0036] As shown in FIG. 6, a quantum converter 300 according to the third embodiment has a stack 20 instead of the stack 10.

[0037] The stack 20 includes a first insulator film 11 and a second insulator film 22 stacked on top of each other. The first insulator film 11 and the second insulator film 22 are in contact with each other, and the stack 20 has an interface 23 between the first insulator film 11 and the second insulator film 22. The first insulator film 11 and the second insulator film 22 do not contain a topological insulator.

[0038] The second insulator film 22 is an antiferromagnetic insulator film. The second insulator film 22 has an easy axis of magnetization along a first axis perpendicular to the interface 23. Laser light L4 is irradiated from the outside toward the stack 20 through the inlet 31, and laser light L5 transmitted through the stack 20 is output to the outside through the outlet 32. The laser light L4 and L5 are circularly polarized laser beams. The laser light L4 and L5 have a component perpendicular to the easy axis of magnetization of the antiferromagnetic insulator contained in the second insulator film 22. For example, the second insulator film 22 contains α-Fe2O3, MnF2, FeF2, NiO, or any combination thereof. In FIG. 6, the arrows in the second insulator film 22 indicate the direction of spin in the antiferromagnetic insulator.

[0039] Other configurations of the third embodiment are similar to those of the first embodiment.

[0040] The polarization and the like of the laser light L2 output to the outside through the output port 32 are detected. In this way, the microwave photons of the microwave MW1 irradiated onto the laminate 20 through the antenna 40 are quantum converted into optical photons. That is, the quantum conversion method using the quantum converter 300 includes a step of irradiating the laser light L1 onto the laminate 20 from a direction tilted from the first axis. For example, microwave photons having a frequency of about 1 GHz to 100 GHz are converted into optical photons having a frequency of about 200 THz.

[0041] Here, we will explain the theory of quantum transformation by the quantum converter 300. Fig. 7 is a schematic diagram showing the theory of quantum transformation by the quantum converter 300 according to the third embodiment. The parameters in Fig. 7 represent the items shown in Table 2.

[0042] [Table 2]

[0043] Interaction ζ between photons and ferromagnetic magnons in an optical cavity 60 μ is expressed by equation (8), and the interaction g between photons and ferromagnetic magnons in the microwave resonator 30 μ is expressed by equation (9) (μ=α,β).

[0044]

number

[0045] N in equations (8) and (9) L indicates the number of second insulating films 12. ζ in formula (8) 0,μ The second insulating film 12 has a volume of 1 mm 3 The strength of the interaction when the film is a single layer is shown in equation (9). 0,μ The second insulating film 12 has a volume of 1 mm 3 The thickness parameter D in equations (8) and (9) indicates the strength of the interaction when the film is a single layer. γ is the number of spins N contained in the second insulator film 12 S The volume of the second insulating film 12 is 1 mm 3 If N is the number of spins involved, S0 This is the value obtained by dividing by

[0046] The conversion efficiency η is expressed by equation (10). The magnon susceptibility χ in equation (10) μ is expressed by equation (11).

[0047]

number

[0048] When the resonance condition is satisfied, i.e., the frequency ω of the itinerant microwave photons and the resonant frequency ω of the microwave resonator 30 e and the resonant frequency ω of the antiferromagnetic insulator μ and δω o When the number N of the second insulating films 22 is equal to the number N of the second insulating films 22, as shown in FIG. L 8 shows the relationship between the number N of the second insulating films 22 in the third embodiment. L 1 is a diagram showing the relationship between the number of second insulator films 22 and the conversion efficiency η. In this way, the quantum converter 300 can quantum convert microwave photons of the microwave MW1 into optical photons. Furthermore, in the quantum converter 300, the conversion efficiency η is LTherefore, the number N of the second insulating films 22 is proportional to the square of L As the thickness parameter D increases, the conversion efficiency η increases significantly. γ is 0.001, ζ 0,α / 2π and ζ 0,β / 2π is about 1.5kHz, γ α / 2π and γ β / 2π is about 1000MHz, g 0,α / 2π and g 0,β / 2π is about 600MHz, κ o,i / 2π and κ o,e / 2π is about 100MHz, κ e,i / 2π and κ e,e / 2π is approximately 300 MHz.

[0049] Furthermore, since the first insulator film 11 and the second insulator film 22 do not contain a topological insulator, light with a frequency of about 200 THz can be used, which means that light with low loss during transmission through an optical fiber can be used.

[0050] Number N of second insulating films 22 L If is constant, the thickness parameter D γ The relationship between the thickness parameter D and the conversion efficiency η is shown in FIG. γ 9 is a graph showing the relationship between the thickness parameter D and the conversion efficiency η. γ above a certain threshold, the thickness parameter D γ The smaller the thickness parameter D, the higher the conversion efficiency η. γ The thickness of the second insulating film 22 corresponding to the threshold value is about 1 nm. L is 10, ζ 0,α / 2π and ζ 0,β / 2π is about 1.5kHz, γ α / 2π and γ β / 2π is about 1000MHz, g 0,α / 2π and g 0,β / 2π is about 600MHz, κ o,i / 2π and κ o,e / 2π is about 100MHz, κe,i / 2π and κ e,e / 2π is approximately 300 MHz.

[0051] (Fourth embodiment) A fourth embodiment will now be described. The fourth embodiment relates to a quantum converter. The quantum converter according to the fourth embodiment converts optical photons into microwave photons. FIG. 10 is a schematic diagram showing the quantum converter according to the fourth embodiment.

[0052] 10 , in the quantum converter 400 according to the fourth embodiment, laser light L6 is irradiated from the outside toward the stack 20 through the inlet 31. The outlet 32 ​​does not necessarily have to be provided. The laser light L6 includes linearly polarized laser light and circularly polarized laser light. The linearly polarized laser light and the circularly polarized laser light have components perpendicular to the easy axis of magnetization of the antiferromagnetic insulator included in the second insulator film 22.

[0053] Other configurations of the fourth embodiment are similar to those of the third embodiment.

[0054] In the fourth embodiment, microwaves MW2 corresponding to the polarization of laser light L3 are emitted from the laminate 20, and the antenna 40 outputs the microwaves MW2 to the outside. In this way, optical photons of the laser light L3 irradiated onto the laminate 20 are quantum converted into microwave photons of the microwaves MW2. That is, the quantum conversion method using the quantum converter 200 includes a step of irradiating the laminate 20 with laser light L6 from a direction tilted from the first axis. For example, optical photons with a frequency of about 200 THz are converted into microwave photons with a frequency of about 1 GHz to 100 GHz.

[0055] The fourth embodiment can also provide the same effects as the third embodiment.

[0056] The quantum converter according to the present disclosure can be used, for example, for communication between superconducting qubits housed in a plurality of refrigerators. However, the use of the quantum converter according to the present disclosure is not limited to communication between superconducting qubits. The quantum converter can also be used for quantum computing.

[0057] The above describes in detail preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0058] Various aspects of the present disclosure are summarized below as appendices.

[0059] (Appendix 1) a three-dimensional cavity resonator; a laminate provided in the three-dimensional cavity resonator, the laminate including a non-magnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film stacked on top of each other, the laminate having an interface between the first insulator film and the second insulator film; a magnetic field applying unit that applies a magnetic field including a component perpendicular to the interface to the stack; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the laminate; and the first insulator film and the second insulator film do not contain a topological insulator; the second insulator film has an easy axis of magnetization along a first axis perpendicular to the interface; A quantum converter in which laser light is irradiated onto the stack from a direction tilted from the first axis. (Appendix 2) 2. The quantum converter according to claim 1, wherein the laser light is irradiated onto the stack from a direction perpendicular to the first axis. (Appendix 3) 3. The quantum converter according to claim 1, further comprising an optical resonator provided within the three-dimensional cavity resonator for resonating the laser light. (Appendix 4) 4. The quantum converter according to claim 1, wherein the three-dimensional cavity resonator is provided with an inlet through which the laser light is introduced from the outside. (Appendix 5) 5. The quantum converter according to claim 4, wherein the three-dimensional cavity resonator is provided with an outlet through which the laser light transmitted through the stack is guided to the outside. (Appendix 6) 6. The quantum converter according to any one of claims 1 to 5, wherein the three-dimensional cavity resonator is a microwave resonator. (Appendix 7) 7. The quantum converter according to claim 1, wherein the second insulating film is a ferromagnetic insulating film. (Appendix 8) The second insulating film is Y3Fe5O 12 , TmFeO 12 , EuS, Cr2Ge2Te6 or BaFe 12 O 19 or any combination thereof. (Appendix 9) 7. The quantum converter according to claim 1, wherein the second insulating film is an antiferromagnetic insulating film. (Appendix 10) 10. The quantum converter of claim 9, wherein the second insulator film comprises α-Fe2O3, MnF2, FeF2, or NiO, or any combination thereof. (Appendix 11) 11. The quantum converter of claim 1, wherein the first insulator film comprises SrTiO3, Al2O3, or both. (Appendix 12) a three-dimensional cavity resonator; a laminate provided in the three-dimensional cavity resonator, the laminate including a non-magnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film stacked on top of each other, the laminate having an interface between the first insulator film and the second insulator film; a magnetic field applying unit that applies a magnetic field including a component perpendicular to the interface to the stack; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the laminate; and the first insulator film and the second insulator film do not contain a topological insulator; The second insulator film has an easy axis of magnetization along a first axis perpendicular to the interface. A quantum conversion method comprising the step of irradiating the stack with laser light from a direction tilted from the first axis. [Explanation of symbols]

[0060] 10, 20: Laminate 11: First insulating film 12, 22: Second insulating film 13, 23: Interface 30: Microwave resonator 31: Entrance 32: Outlet 35: Support member 40: Antenna 51:N pole 52:S pole 60: Optical resonator 100, 200, 300, 400: Quantum Converter

Claims

1. a three-dimensional cavity resonator; a laminate provided in the three-dimensional cavity resonator, the laminate including a non-magnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film stacked on top of each other, the laminate having an interface between the first insulator film and the second insulator film; a magnetic field applying unit that applies a magnetic field including a component perpendicular to the interface to the stack; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the laminate; and the first insulator film and the second insulator film do not contain a topological insulator, the second insulator film has an easy axis of magnetization along a first axis perpendicular to the interface; A quantum converter in which laser light is irradiated onto the stack from a direction tilted from the first axis.

2. The quantum converter according to claim 1 , wherein the laser light is irradiated onto the stack from a direction perpendicular to the first axis.

3. 3. The quantum converter according to claim 1, further comprising an optical resonator provided within the three-dimensional cavity resonator for resonating the laser light.

4. 3. The quantum converter according to claim 1, wherein the three-dimensional cavity resonator is provided with an inlet through which the laser light is introduced from the outside.

5. 5. The quantum converter according to claim 4, wherein the three-dimensional cavity resonator is provided with an outlet through which the laser light transmitted through the laminate is guided to the outside.

6. 3. The quantum converter according to claim 1, wherein the second insulating film is a ferromagnetic insulating film.

7. 3. The quantum converter according to claim 1, wherein the second insulating film is an antiferromagnetic insulating film.

8. a three-dimensional cavity resonator; a laminate provided in the three-dimensional cavity resonator, the laminate including a non-magnetic first insulator film and a ferromagnetic or antiferromagnetic second insulator film stacked on top of each other, the laminate having an interface between the first insulator film and the second insulator film; a magnetic field applying unit that applies a magnetic field including a component perpendicular to the interface to the stack; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the laminate; and the first insulator film and the second insulator film do not contain a topological insulator, a quantum converter using the quantum converter, wherein the second insulator film has an easy axis of magnetization along a first axis perpendicular to the interface, A quantum conversion method comprising the step of irradiating the stack with laser light from a direction tilted from the first axis.

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