Quantum converter and quantum conversion method

Abstract

To provide a quantum converter and a quantum conversion method capable of reducing the influence of a magnetic field on the outside.SOLUTION: A quantum converter includes a three dimensional cavity resonator, an object of an antiferromagnetic insulator provided in the three dimensional cavity resonator and having an easy magnetization axis along a first axis, and a microwave transmitting and receiving unit configured to transmit and receive a microwave to and from the object, wherein the object is irradiated with laser light from a direction inclined from 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 ferromagnetic materials have been proposed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-512161 [Patent Document 2] Special Publication No. 2022-538247 [Patent Document 3] Special Publication No. 2021-536090 [Patent Document 4] US Patent Application Publication No. 2019 / 0019099 Summary of the Invention [Problem to be solved by the invention]

[0004] Quantum computers include qubits, but if a quantum converter including a ferromagnetic material is used, the qubits may be affected by the magnetic field generated by the ferromagnetic material.

[0005] An object of the present disclosure is to provide a quantum converter and a quantum conversion method that can reduce the influence of an external magnetic field. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a quantum converter including: a three-dimensional cavity resonator; an object made of an antiferromagnetic insulator, the object being disposed within the three-dimensional cavity resonator and having an easy axis of magnetization aligned with a first axis; and a microwave transceiver for transmitting and receiving microwaves between the object and the object, wherein laser light is irradiated onto the object from a direction tilted from the first axis. [Effects of the Invention]

[0007] According to the present disclosure, the influence of external magnetic fields can be reduced. [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. 1 is a diagram showing the relationship between the magnetic field and the resonant frequency in an antiferromagnetic insulator. [Figure 4] FIG. 10 is a schematic diagram showing a quantum converter according to a second embodiment. [Figure 5] FIG. 10 is a schematic diagram showing a quantum converter according to a third embodiment. [Figure 6] FIG. 10 is a schematic diagram illustrating the theory of quantum transformation by a quantum transformer according to a third embodiment. [Figure 7] 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, an antiferromagnetic insulator object 10, an N pole 51, an S pole 52, and an antenna 40.

[0012] The microwave resonator 30 has an inlet 31 and an outlet 32. The object 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 object 10. An optical fiber is connected to the outlet 32, and laser light L2 that has passed through the object 10 is extracted to the outside through the outlet 32. The laser light L1 and L2 are linearly polarized laser beams. The laser light L1 and L2 have components perpendicular to the easy axis of magnetization of an antiferromagnetic insulator included in the object 10. The microwave resonator 30 is an example of a three-dimensional cavity resonator.

[0013] The object 10 has a three-dimensional shape, for example, a rectangular parallelepiped. The length of each side of the object 10 is, for example, approximately 1 μm to 1 mm. The object 10 has a first surface 11, a second surface 12, a third surface 13, a fourth surface 14, a fifth surface 15, and a sixth surface 16. The first surface 11 and the second surface 12 are parallel to each other, the third surface 13 and the fourth surface 14 are parallel to each other, and the fifth surface 15 and the sixth surface 16 are parallel to each other. The third surface 13 faces the inlet 31, and the fourth surface 14 faces the outlet 32. The laser light L1 is irradiated onto the third surface 13 of the object 10, and the laser light L2 is emitted from the fourth surface 14. The object 10 includes an antiferromagnetic insulator, and the antiferromagnetic insulator has an easy axis of magnetization aligned along a first axis perpendicular to the first surface 11 and the second surface 12. The antiferromagnetic insulator includes, for example, α-Fe2O3, MnF2, FeF2, or NiO, or any combination thereof. In Figure 1, the arrows in the object 10 indicate the direction of spin in the antiferromagnetic insulator.

[0014] The north pole 51 and south pole 52 are provided on the outer wall surface of the microwave resonator 30. The north pole 51 faces the first surface 11, and the south pole 52 faces the second surface 12. A magnetic field H directed from the north pole 51 to the south pole 52 is generated between the north pole 51 and the south pole 52. The north pole 51 and the south pole 52 act as magnetic field application units and apply the magnetic field H including a component perpendicular to the first axis to the object 10.

[0015] 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 and transmits and receives microwaves to and from the object 10. In this embodiment, the antenna 40 transmits a microwave MW1 input from outside to the object 10.

[0016] 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 object 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 object 10 with the laser light L1 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.

[0017] 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.

[0018] [Table 1]

[0019] resonance frequency ω α , ω β In terms of the magnetic field and resonant frequency ω in an antiferromagnetic insulator, α , ω β The relationship between the magnetic field and the resonance frequency ω is shown in Figure 3. As shown in Figure 3, when the magnetic field is zero, the resonance frequency ω α , ω β are equal to each other, and the stronger the magnetic field, the higher the resonant frequency ωα is large, and the resonant frequency ω β The resonant frequency ω when the magnetic field is zero α , ω β is on the order of several hundred GHz. Figure 3 also shows the characteristics of a ferromagnetic insulator. In a ferromagnetic insulator, the resonant frequency is zero when the magnetic field is zero, and no resonance occurs. Also, in an antiferromagnetic insulator, there is only one resonant frequency for one magnetic field, but in an antiferromagnetic insulator, there are two resonant frequencies for one magnetic field. For this reason, resonance can occur in an antiferromagnetic insulator over a wider frequency band than in a ferromagnetic insulator.

[0020] In the quantum transformation shown in Figure 2, the equations of motion expressed by equations (1) and (2) hold. The parameters in equations (1) and (2) represent the items shown in Table 2. In addition, κ in equation (1) e is expressed by equation (3).

[0021]

number

[0022] [Table 2]

[0023] In this embodiment, the Hamiltonian H total is the sum of the Hamiltonian of the photons in the microwave resonator 30, the Hamiltonian of the antiferromagnetic magnons, and the Hamiltonian representing the interaction between the photons and the antiferromagnetic magnons in the microwave resonator 30.

[0024] Then, by solving the equations of motion expressed by equations (1) and (2) using the input-output formalism, equation (4) is obtained, which shows the conversion efficiency η. e and magnon susceptibility χ μ are expressed by equations (5) and (6), respectively.

[0025]

number

[0026] 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 β and the magnon-magnon interaction G mm When is 0, the conversion efficiency η is expressed by equation (7).

[0027]

number

[0028] For example, ζ β / 2π is about 3μHz, g β / 2π is about 400MHz, κ e,i / 2π is about 200MHz, κ e,e / 2π is about 200MHz, γ β When / 2π is about 70MHz, the conversion efficiency η is 10 -15 In this way, quantum converter 100 can quantum convert microwave photons of microwave MW1 into optical photons.

[0029] Furthermore, since the object 10 contains an antiferromagnetic insulator, even if a quantum device including a quantum bit or the like is placed near the quantum converter 100, the influence of the magnetic field from the object 10 on the quantum device can be prevented.

[0030] 3, the antiferromagnetic insulator can resonate even in the absence of a magnetic field. Therefore, depending on the resonant frequency of the quantum bit that resonates with the quantum converter 100, the north pole 51 and south pole 52 may not be provided, or the magnetic field H generated by the north pole 51 and south pole 52 may be small. This reduces the effect of the north pole 51 and south pole 52 on the quantum device.

[0031] The shape of the object 10 does not have to be rectangular parallelepiped, but may be spherical or the like.

[0032] (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 4 is a schematic diagram showing the quantum converter according to the second embodiment.

[0033] As shown in Fig. 4, in the quantum converter 200 according to the second embodiment, laser light L3 is irradiated from the outside toward the object 10 through the inlet 31. The laser light L3 is irradiated onto the third surface 13 of the object 10. The outlet 32 ​​does not necessarily have to be provided. The laser light L3 includes two types of linearly polarized laser light whose deflection angles are orthogonal to each other. These linearly polarized laser lights have components perpendicular to the easy axis of magnetization of the antiferromagnetic insulator included in the object 10.

[0034] Other configurations of the second embodiment are similar to those of the first embodiment.

[0035] In the second embodiment, microwaves MW2 corresponding to the polarization of laser light L3 are emitted from the object 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 object 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 object 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.

[0036] The second embodiment can also provide the same effects as the first embodiment.

[0037] (Third embodiment) A third embodiment will be described. The third embodiment differs from the first embodiment mainly in that an optical resonator is provided. Fig. 5 is a schematic diagram showing a quantum converter according to the third embodiment.

[0038] 5, the quantum converter 300 according to the third embodiment has an optical resonator 60. 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 object 10, and the second mirror 62 is provided between the outlet 32 ​​and the object 10.

[0039] An optical fiber is connected to the inlet 31, and laser light L4 is irradiated from the outside toward the object 10 through the inlet 31. An optical fiber is connected to the outlet 32, and laser light L5 that has passed through the object 10 is extracted to the outside through the outlet 32. Laser light L4 is irradiated onto the third surface 13 of the object 10, and laser light L5 is emitted from the fourth surface 14. Laser light L4 and L5 are circularly polarized laser light. Laser light L4 and L5 have a component perpendicular to the easy axis of magnetization of the antiferromagnetic insulator included in the object 10. Optical resonator 60 amplifies the circularly polarized laser light.

[0040] Other configurations of the third embodiment are similar to those of the first embodiment.

[0041] The polarization and the like of the laser light L5 outputted to the outside through the output port 32 are detected. In this way, the microwave photons of the microwave MW1 irradiated onto the object 10 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 object 10 with laser light L4 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.

[0042] Here, we will explain the theory of quantum transformation by the quantum converter 300. Fig. 6 is a schematic diagram showing the theory of quantum transformation by the quantum converter 300 according to the third embodiment. The parameters in Fig. 6 represent the items shown in Table 3.

[0043] [Table 3]

[0044] In the quantum transformation shown in Fig. 6, the equations of motion expressed by equations (8) to (10) hold. o is expressed by equation (11).

[0045]

number

[0046] In this embodiment, the Hamiltonian H total is the sum of a Hamiltonian of photons in the microwave resonator 30, a Hamiltonian of antiferromagnetic magnons, a Hamiltonian representing the interaction between photons and antiferromagnetic magnons in the microwave resonator 30, a Hamiltonian representing the interaction between photons and antiferromagnetic magnons in the optical resonator 60, and a Hamiltonian of photons in the optical resonator 60.

[0047] Then, by solving the equations of motion expressed by equations (8) to (10) using the input-output formalism, equation (12) is obtained, which shows the conversion efficiency η. o is expressed by equation (13), and δω in equation (13) o is expressed by equation (14).

[0048]

number

[0049] 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 β and δω o and the magnon-magnon interaction G mm When is 0, the conversion efficiency η is expressed by equation (15).

[0050]

number

[0051] For example, ζ β / 2π is 1.5×10 -3 About MHz, γ β / 2π is about 1000MHz, κ o,i / 2π and κ o,e / 2π is about 100MHz, g β / 2π is about 600MHz, κ e,i / 2π and κ e,e When / 2π is about 300MHz, the conversion efficiency η is 10 -11 In this way, quantum converter 300 can quantum convert microwave photons of microwave MW1 into optical photons.

[0052] The third embodiment can also provide the same effects as the first embodiment.

[0053] (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. 7 is a schematic diagram showing the quantum converter according to the fourth embodiment.

[0054] As shown in FIG. 7, in the quantum converter 400 according to the fourth embodiment, laser light L6 is irradiated from the outside toward the object 10 through the inlet 31. The laser light L6 is irradiated onto the third surface 13 of the object 10. The outlet 32 ​​does not 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 object 10. The optical resonator 60 amplifies the circularly polarized laser light.

[0055] Other configurations of the fourth embodiment are similar to those of the third embodiment.

[0056] In the fourth embodiment, microwaves MW2 corresponding to the polarization of laser light L6 are emitted from the object 10, and the antenna 40 outputs the microwaves MW2 to the outside. In this way, optical photons of the laser light L6 irradiated onto the object 10 are quantum converted into microwave photons of the microwaves MW2. That is, the quantum conversion method using the quantum converter 400 includes a step of irradiating the object 10 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.

[0057] The fourth embodiment can also provide the same effects as the third embodiment.

[0058] 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.

[0059] 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.

[0060] Various aspects of the present disclosure are summarized below as appendices.

[0061] (Appendix 1) a three-dimensional cavity resonator; a body of antiferromagnetic insulator disposed within the three-dimensional cavity resonator and having an easy axis of magnetization along a first axis; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the object; and A quantum converter in which the object is irradiated with laser light from a direction tilted from the first axis. (Appendix 2) 2. The quantum converter of claim 1, wherein the laser light is irradiated onto the object from a direction perpendicular to the first axis. (Appendix 3) 3. A quantum converter according to claim 1 or 2, comprising a magnetic field application unit that applies a magnetic field including a component parallel to the first axis to the object. (Appendix 4) 4. The quantum converter according to any one of claims 1 to 3, further comprising an optical resonator provided within the three-dimensional cavity resonator, for resonating the laser light. (Appendix 5) 5. The quantum converter according to any one of claims 1 to 4, wherein the three-dimensional cavity resonator is provided with an inlet through which the laser light is introduced from outside. (Appendix 6) 6. The quantum converter according to claim 5, wherein the three-dimensional cavity resonator is provided with an outlet through which the laser light transmitted through the object is guided to the outside. (Appendix 7) 7. The quantum converter according to claim 1, wherein the three-dimensional cavity resonator is a microwave resonator. (Appendix 8) 8. The quantum converter of any one of claims 1 to 7, wherein the antiferromagnetic insulator comprises α-Fe2O3, MnF2, FeF2, or NiO, or any combination thereof. (Appendix 9) a three-dimensional cavity resonator; a body of antiferromagnetic insulator disposed within the three-dimensional cavity resonator and having an easy axis of magnetization along a first axis; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the object; A quantum transformation method using a quantum converter having A quantum conversion method comprising the step of irradiating the object with laser light from a direction tilted from the first axis. [Explanation of symbols]

[0062] 10:Object 30: Microwave resonator 31: Entrance 32: Outlet 35: Support member 40: Antenna 51:N pole 52:S pole 60: Optical resonator 61: 1st mirror 62:Second mirror 100, 200, 300, 400: Quantum Converter

Claims

1. a three-dimensional cavity resonator; a body of antiferromagnetic insulator disposed within the three-dimensional cavity resonator and having an easy axis of magnetization along a first axis; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the object; and A quantum converter in which the object is irradiated with laser light from a direction tilted from the first axis.

2. The quantum converter of claim 1 , wherein the laser light is irradiated onto the object in a direction perpendicular to the first axis.

3. 3. The quantum converter according to claim 1, further comprising a magnetic field applying unit that applies a magnetic field including a component parallel to the first axis to the object.

4. 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.

5. 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.

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

7. a three-dimensional cavity resonator; a body of antiferromagnetic insulator disposed within the three-dimensional cavity resonator and having an easy axis of magnetization along a first axis; a microwave transmitting / receiving unit that transmits and receives microwaves to and from the object; A quantum transformation method using a quantum converter having A quantum conversion method comprising the step of irradiating the object with laser light from a direction tilted from the first axis.

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