Irreversible circuit element and quantum computer

Abstract

The invention provides an irreversible circuit element and a quantum computer. The irreversible circuit element can sufficiently suppress heat generation in an extremely low temperature environment, and the quantum computer is provided with the irreversible circuit element. The irreversible circuit element includes a center conductor, a first loss layer and a second loss layer disposed on an outer side of the center conductor, and a first housing and a second housing disposed on an outer side of the first loss layer and the second loss layer. The first loss layer has a first magnetic body and a first absorber, and the second loss layer has a second magnetic body and a second absorber. The center conductor has a first terminal and a second terminal for inputting and outputting signals, a region that overlaps the first magnetic body and the second magnetic body when viewed from the thickness direction and is continuous between the first terminal and the second terminal, and a region that overlaps the first absorber and the second absorber when viewed from the thickness direction. The center conductor irreversibly transmits a signal between the first terminal and the second terminal. At least a portion of the central conductor is a superconductor.

Description

TECHNICAL FIELD

[0001] The present application relates to an irreversible circuit element and a quantum computer. BACKGROUND

[0002] An irreversible circuit element is an element that defines a direction of transmission of a high-frequency signal. An isolator, a circulator are examples of an irreversible circuit element. Irreversible circuit elements are widely used in circuits that transmit high-frequency signals.

[0003] Irreversible circuit elements are used in a variety of places where high-frequency signals are used. For example, an isolator that uses several GHz to about 10 GHz as a usage band is disclosed in Patent Literature 1.

[0004] Isolators are also used in quantum computers. Among various quantum computers, in the currently most advantageous superconducting quantum computer, in order to perform accurate measurement of a quantum bit, an isolator that functions at an extremely low temperature is required.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: International Publication No. 2023 / 238310 SUMMARY OF THE INVENTION

[0008] PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] The isolator is disposed at a position closest to the quantum bit in a part of the refrigerator possessed by the superconducting quantum computer where the temperature is the lowest.

[0010] Since the isolator realizes an isolation characteristic by converting a high-frequency signal into heat, generation of heat cannot be avoided. Therefore, in order to maintain an extremely low-temperature environment around the quantum bit, it is necessary to minimize the heat generation in the isolator.

[0011] However, the irreversible circuit element disclosed in Patent Literature 1 is based on the configuration of an isolator that functions at room temperature, and has a problem that heat generation cannot be sufficiently suppressed in an extremely low-temperature environment.

[0012] The present application was completed in order to solve such a conventional problem, and aims to provide an irreversible circuit element that can sufficiently suppress heat generation in an extremely low-temperature environment and a quantum computer provided with the irreversible circuit element.

[0013] MEANS FOR SOLVING THE PROBLEM

[0014] The present application provides the following means in order to solve the above problem.

[0015] The irreversible circuit element of the present embodiment includes a conductor, a loss layer disposed outside the conductor, and a housing disposed outside the loss layer. The loss layer includes a magnetic body and an absorber. The conductor includes a first terminal and a second terminal that input and output a signal, a region that overlaps the magnetic body when viewed in a thickness direction and is continuous between the first terminal and the second terminal, and a region that overlaps the absorber when viewed in the thickness direction, and the conductor irreversibly transmits the signal between the first terminal and the second terminal. At least a part of the conductor is a superconductor.

[0016] Effects of the Invention

[0017] The present invention provides an irreversible circuit element that can sufficiently suppress heat generation in an extremely low temperature environment and a quantum computer including the irreversible circuit element. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a cross-sectional view (1) of the irreversible circuit element of the present embodiment.

[0019] Figure 2 is a plan view of the irreversible circuit element of the present embodiment.

[0020] Figure 3 is a plan view of a loss layer and a frame of the irreversible circuit element of the present embodiment.

[0021] Figure 4 is a plan view of an adhesive layer and a frame of the irreversible circuit element of the present embodiment.

[0022] Figure 5 is a cross-sectional view (2) of the irreversible circuit element of the present embodiment.

[0023] Figure 6 is a plan view showing a state in which the loss layer of the irreversible circuit element of the present embodiment is divided into a plurality of pieces.

[0024] Figure 7 is a plan view of a center conductor and a resonator of the irreversible circuit element of the present embodiment.

[0025] Figure 8 is a plan view of a housing and a magnet of the irreversible circuit element of the present embodiment.

[0026] Figure 9 is a table showing physical properties of various materials.

[0027] Figure 10 is a schematic view of the quantum computer of the present embodiment.

[0028] Explanation of Reference Signs

[0029] 10, center conductor; 11, 1st region; 12, 2nd region; 14, metal coating; 21, 1st loss layer; 22, 2nd loss layer; 25, 1st magnetic body; 26, 1st absorber; 27, 2nd magnetic body; 28, 2nd absorber; 31, 1st magnet; 32, 2nd magnet; 41, upper housing; 41a, 41b, heat dissipation surface; 42, lower housing; 42a, 42b, heat dissipation surface; 50, resonator; 61, 1st frame; 62, 2nd frame; 63, 64, gap; 71, 1st adhesive layer; 72, 2nd adhesive layer; 100, irreversible circuit element; 200, quantum computer; 201, quantum processor; 202, 203, irreversible circuit element; 204, 205, filter; 206, amplifier; S1, 1st connection line; S2, 2nd connection line; S21, 1st side; S22, 2nd side; S23, 3rd side; T1, 1st terminal; T2, 2nd terminal. DETAILED DESCRIPTION

[0030] Embodiments of the irreversible circuit element and the quantum computer of the present application will be described below with reference to the drawings. Note that the dimensional ratios of the respective components in each drawing are not necessarily the same as the actual dimensional ratios.

[0031] Figure 1 is a cross-sectional view of the irreversible circuit element 100 of this embodiment. The irreversible circuit element 100 includes, for example, a center conductor 10, a 1st loss layer 21, a 2nd loss layer 22, a 1st magnet 31, a 2nd magnet 32, an upper housing 41 as a 1st housing, a lower housing 42 as a 2nd housing, a resonator 50, a 1st frame 61, and a 2nd frame 62. The irreversible circuit element 100 functions as an isolator, for example.

[0032] Figure 2 is a plan view of the irreversible circuit element 100 of this embodiment. In this specification, the direction from a 1st terminal T1 toward a 2nd terminal T2 of the center conductor 10 is set as an x direction, the direction orthogonal to the x direction in the plane in which the center conductor 10 extends is set as a y direction, and the direction orthogonal to the x direction and the y direction is set as a z direction. The thickness direction of each layer is an example of the z direction. In addition, with respect to the z direction, the side on which the upper housing 41 exists is set as the upper side, and the side on which the lower housing 42 exists is set as the lower side.

[0033] Figure 2 is a view obtained by removing the 1st loss layer 21, the 1st magnet 31, the upper housing 41, and the lower housing 42 from the irreversible circuit element 100 and viewing the center conductor 10, the 2nd loss layer 22, and the 2nd frame 62 from the upper side. Figure 1 is a view showing the magnetic field distribution along the x direction of the irreversible circuit element 100. Figure 2A cross-sectional view of the section obtained by cutting along line AA.

[0034] Figure 3 From Figure 2 The figure is obtained by further removing the center conductor 10 and looking down from above at the second loss layer 22 and the second type frame 62. Figure 4 From Figure 3 The figure is obtained by further removing the second loss layer 22 and viewing the second adhesive layer 72 and the second frame 62 (described later) from above. Figure 5 It means along Figure 2 A cross-sectional view of the section obtained by cutting along the BB line.

[0035] The first loss layer 21 and the second loss layer 22 are respectively disposed outside the center conductor 10 and the resonator 50, sandwiching them in the z-direction. The first loss layer 21 includes a first magnetic body 25 and a first absorber 26. The second loss layer 22 includes a second magnetic body 27 and a second absorber 28. The shapes of the first loss layer 21 and the second loss layer 22 are approximately the same, symmetrically sandwiching the center conductor 10 and the resonator 50. The first loss layer 21 is located between the center conductor 10 and the first magnet 31. The second loss layer 22 is located between the center conductor 10 and the second magnet 32.

[0036] The upper housing 41 and the lower housing 42 are respectively disposed outside the first loss layer 21 and the second loss layer 22, sandwiching them in the z-direction. The upper housing 41 is sandwiched between the first magnet 31 and the first loss layer 21. The lower housing 42 is sandwiched between the second magnet 32 ​​and the second loss layer 22. The upper housing 41 or the lower housing 42 is conductive, for example, grounded to a reference potential. The reference potential is, for example, ground.

[0037] like Figure 1 As shown, the upper housing 41 has heat dissipation surfaces 41a and 41b, which dissipate heat generated in the central conductor 10, the first loss layer 21, and the second loss layer 22. Similarly, the lower housing 42 has heat dissipation surfaces 42a and 42b, which dissipate heat generated in the central conductor 10, the first loss layer 21, and the second loss layer 22. The heat dissipation surfaces 41a, 41b, 42a, and 42b are parallel to the xz plane.

[0038] The upper housing 41 is mounted across heat dissipation surfaces 41a and 41b to an extremely low-temperature plate that serves as a heat bath inside a refrigerator (not shown). Similarly, the lower housing 42 is mounted across heat dissipation surfaces 42a and 42b to an extremely low-temperature plate inside a refrigerator (not shown).

[0039] The upper shell 41 and the lower shell 42 are made of a high thermal conductivity material having a thermal conductivity of 300 W / m·K or higher at extremely low temperatures below 4 K. The high thermal conductivity material constituting the upper shell 41 and the lower shell 42 is, for example, any one of the metals such as gold (Au), silver (Ag), copper (Cu), platinum (Pt), palladium (Pd), indium (In) and aluminum (Al).

[0040] By constructing the upper housing 41 and the lower housing 42 in this way, the irreversible circuit element 100 can maintain thermal conductivity at extremely low temperatures, thereby improving heat dissipation and reducing Johnson noise (thermal noise). Therefore, the irreversible circuit element 100 improves insertion loss, thus contributing to accurate measurement of qubits when used in quantum computers.

[0041] In particular, copper with a purity of 4N (99.99%) or higher is preferred as a highly thermally conductive material constituting the upper shell 41 and the lower shell 42, as it effectively increases thermal conductivity at extremely low temperatures. Figure 9 As shown, copper with a purity of 4N exhibits a thermal conductivity of 330 W / m·K at 4K. Furthermore, nearly 100% copper with a purity higher than 4N exhibits a thermal conductivity of 11800 W / m·K at 4K. Additionally, in Figure 9 In Chinese, "pure" means approximately 100% purity.

[0042] The upper housing 41 and the first loss layer 21 are bonded together using a first adhesive layer 71 made of an insulating adhesive. Similarly, the lower housing 42 and the second loss layer 22 are bonded together using a second adhesive layer 72 made of an insulating adhesive. Alternatively, it is also possible that only one of the groups of the upper housing 41 and the first loss layer 21 and the lower housing 42 and the second loss layer 22 is bonded together using either the first adhesive layer 71 or the second adhesive layer 72.

[0043] like Figure 6 As shown, at least one of the first loss layer 21 and the second loss layer 22 may be broken into multiple fragments due to impact or thermal expansion and contraction. In such a case, the first adhesive layer 71 or the second adhesive layer 72 can fix the aforementioned multiple fragments so that they will not fall off between the upper housing 41 and the lower housing 42.

[0044] Therefore, in the irreversible circuit element 100, even if at least one of the first loss layer 21 and the second loss layer 22 breaks irregularly, the isolation characteristics of the irreversible circuit element 100 can be maintained.

[0045] The first adhesive layer 71 and the second adhesive layer 72 have a temperature of 35 × 10⁻⁶ at extremely low temperatures below 4 K. -6The coefficient of linear expansion is below / K. For example, Henkel's STYCAST 2850FT or STYCAST 2850GT can be used as the first adhesive layer 71 and the second adhesive layer 72. Figure 9 As shown, the coefficient of linear expansion of the STYCAST 2850FT is 31 × 10⁻⁶. -6 / K, The coefficient of linear expansion of the STYCAST 2850GT is 25×10. -6 / K is particularly close to the coefficient of linear expansion of metals such as aluminum (Al), copper, solder, and brass.

[0046] The first adhesive layer 71 and the second adhesive layer 72, which have a coefficient of linear expansion close to that of metal, are less prone to film peeling from the upper housing 41 and the lower housing 42, and have excellent adhesion to the upper housing 41 and the lower housing 42.

[0047] In addition, such as Figure 9 As shown, the thermal conductivity of the STYCAST 2850FT is 0.053 W / m·K at 4K, and that of the STYCAST 2850GT is 0.1 W / m·K at 4K, both higher than that of air and vacuum. It can be seen that the thermal conductivity of air is 0.026 W / m·K at 300K, decreasing further at 4K to about 1 / 10 of the thermal conductivity of the STYCAST 2850FT at 4K. The thermal conductivity of vacuum is 0.002 W / m·K at 300K, and almost zero at 4K. Furthermore, the internal environment of the refrigeration unit is a high vacuum.

[0048] Therefore, the first adhesive layer 71 and the second adhesive layer 72, which are made of resin-based adhesives such as STYCAST 2850FT, do not reduce the adhesion at the interface with the upper housing 41, the lower housing 42, the first loss layer 21 and the second loss layer 22 at extremely low temperatures below 4K, and can maintain a higher thermal conductivity than air, thereby improving the heat dissipation of the irreversible circuit element 100.

[0049] Type 1 frame 61 and Type 2 frame 62 are disposed between the upper housing 41 and the lower housing 42, and are insulating frames surrounding the first loss layer 21 and the second loss layer 22, respectively. For example, Teflon (registered trademark) can be used as Type 1 frame 61 and Type 2 frame 62.

[0050] like Figure 5As shown, a gap 63 is formed between the first type frame 61 and the first loss layer 21, and the gap 63 is used to store a remaining portion of an adhesive generated when the upper case 41 and the first loss layer 21 are bonded by the first adhesive layer 71. That is, the first adhesive layer 71 is formed so as to extend to between the first type frame 61 and the first loss layer 21. Similarly, a gap 64 is formed between the second type frame 62 and the second loss layer 22, and the gap 64 is used to store a remaining portion of an adhesive generated when the lower case 42 and the second loss layer 22 are bonded by the second adhesive layer 72. That is, the second adhesive layer 72 is formed so as to extend to between the second type frame 62 and the second loss layer 22.

[0051] The surface tension of the first adhesive layer 71 stored in the gap 63 is used to inhibit the first adhesive layer 71 from entering between the opposing surfaces of the first type frame 61 and the first magnetic body 25 along the z direction, between the opposing surfaces of the first type frame 61 and the first absorber 26 along the z direction, and between the opposing surfaces of the first magnetic body 25 and the first absorber 26 along the z direction, other than the portion of the gap 63.

[0052] Similarly, the surface tension of the second adhesive layer 72 stored in the gap 64 is used to inhibit the second adhesive layer 72 from entering between the opposing surfaces of the second type frame 62 and the second magnetic body 27 along the z direction, between the opposing surfaces of the second type frame 62 and the second absorber 28 along the z direction, and between the opposing surfaces of the second magnetic body 27 and the second absorber 28 along the z direction, other than the portion of the gap 64.

[0053] Thus, by the first adhesive layer 71 and the second adhesive layer 72 being stored in the gaps 63, 64, the first magnetic body 25 and the first absorber 26 and the second magnetic body 27 and the second absorber 28 are in close contact with each other, and thus the isolation characteristics of the irreversible circuit element 100 can be stabilized.

[0054] Figure 7 is a plan view of the center conductor 10 and the resonator 50 of the irreversible circuit element 100 of the present embodiment.

[0055] The center conductor 10 has a first terminal T1 and a second terminal T2 that input and output high-frequency signals. The first terminal T1 and the second terminal T2 are connected to terminals outside.

[0056] The surfaces of the first terminal T1 and the second terminal T2 can also be covered with a metal film of any one of nickel (Ni), tin, copper, silver, or the like. For example, the metal film 14 is formed by plating these metals on the surfaces of the first terminal T1 and the second terminal T2, and thus wettability, connection strength, and conductivity can be ensured when the first terminal T1 and the second terminal T2 are soldered to terminals outside.

[0057] The center conductor 10 irreversibly transmits high-frequency signals between the first terminal T1 and the second terminal T2. "Irreversible transmission of high-frequency signals" means that the signal transmission efficiency varies depending on the direction. For example, the situation where the center conductor 10 transmits signals with low loss in the positive direction but almost no signal in the negative direction is equivalent to "irreversible transmission of high-frequency signals." The transmission direction of the high-frequency signals in the center conductor 10 is controlled by the first loss layer 21 and the second loss layer 22.

[0058] The high-frequency signal input from terminal T1 is transmitted to terminal T2 with low loss. The high-frequency signal input from terminal T2 is almost entirely absorbed by the first absorber 26 and the second absorber 28. That is, almost no high-frequency signal is transmitted from terminal T2 to terminal T1.

[0059] The center conductor 10 only needs to efficiently transmit high-frequency signals, and can be made of metals such as aluminum, copper, silver, gold, stainless steel (SUS), or beryllium copper (BeCu). The center conductor 10 can also be a component made by plating non-conductors or conductors with high resistance (such as phosphor bronze) with aluminum, copper, silver, gold, or stainless steel.

[0060] Alternatively, the center conductor 10 can also be a superconductor that exhibits superconductivity at extremely low temperatures below 4K, such as aluminum, niobium (Nb), tantalum (Ta), etc. The center conductor 10 can also be a component made by plating a non-conductor, high-resistivity conductor (such as phosphor bronze) with superconductors such as aluminum, niobium, tantalum, etc.

[0061] Especially when using aluminum with a purity of 4N (99.99%) or higher as the superconductor constituting the central conductor 10, it is preferred because it can not only reduce residual resistance but also increase thermal conductivity. For example... Figure 9 As shown, aluminum with a purity of 4N exhibits a thermal conductivity of 1600 W / m·K at 4K. Aluminum with a purity of 5N exhibits a thermal conductivity of 11000 W / m·K at 4K. Furthermore, almost 100% aluminum with a purity higher than 5N exhibits a thermal conductivity of 17000 W / m·K at 4K.

[0062] Since the central conductor 10, which is at least partially composed of a superconductor, has almost zero resistance at extremely low temperatures, it can suppress heating, thus reducing Johnson noise (thermal noise). Therefore, the irreversible circuit element 100 improves insertion loss, which can help in the accurate measurement of qubits when used in quantum computers.

[0063] The center conductor 10 has a first region 11 and a second region 12. The center conductor 10 may also have regions other than the first region 11 and the second region 12. The first region 11 is the region that overlaps with the first magnetic body 25 and the second magnetic body 27 when viewed from the z-direction. The first region 11 extends continuously between the first terminal T1 and the second terminal T2. The first region 11 is sandwiched between the first magnetic body 25 and the second magnetic body 27 in the z-direction. The second region 12 is the region that overlaps with the first absorber 26 and the second absorber 28 when viewed from the z-direction. The second region 12 is sandwiched between the first absorber 26 and the second absorber 28 in the z-direction. The boundary between the first region 11 and the second region 12 coincides, for example, with the boundary between the first magnetic body 25 and the first absorber 26 when viewed from the z-direction.

[0064] like Figure 7 As shown, the center conductor 10 has a first connecting line S1 and a second connecting line S2 on its outer periphery when viewed from the z-direction. The first connecting line S1 and the second connecting line S2 are lines that connect the first terminal T1 and the second terminal T2, respectively. The first connecting line S1 and the second connecting line S2 together form the outer periphery of the center conductor 10 when viewed from the z-direction.

[0065] The first connecting line S1 is an edge of the first region 11. The first connecting line S1 can be a straight line or a curve. Figure 7 In the example shown, the first connecting line S1 is a straight line parallel to the straight line L1 that connects the first terminal T1 and the second terminal T2.

[0066] The second connecting line S2 exists across the first region 11 and the second region 12. The second connecting line S2 has, for example, a first side S21 and a second side S22 spanning from the first region 11 to the second region 12, and a third side S23 as a side of the second region 12. The first side S21, the second side S22, and the third side S23 can be straight lines or curves.

[0067] The resonator 50 encloses a portion of the high-frequency signal transmitted along the second connecting line S2 within a certain space. The resonator 50 is located within the range reached by the high-frequency signal transmitted along the second connecting line S2. The resonator 50 is connected to the center conductor 10, for example. The resonator 50 and the center conductor 10 can also be integrated. The resonator 50 may have one or more protrusions extending from the third side S23, for example.

[0068] Figure 7 The resonator 50 shown is a quarter-wavelength resonator. The quarter-wavelength resonator satisfies the following relationship (1).

[0069] L≤1 / 4f0(ε0μ0ε γ μ γ ) 1 / 2··· (1)

[0070] In equation (1), L is the length of the quarter-wavelength resonator, f0 is the resonant frequency, ε0 ​​is the permittivity of vacuum, μ0 is the permeability of vacuum, and ε γ It is the dielectric constant of the first absorber 26 and the second absorber 28, μ γ It is the permeability of the first absorber 26 and the second absorber 28. The resonator 50 blocks high-frequency signals when the length L of the resonator 50 is an integer multiple of 1 / 4 wavelength of the high frequency transmitted along the second connecting line S2. The length L is the length of the resonator 50 in the protruding direction from the third side S23.

[0071] When viewed from the z-direction, the resonator 50 overlaps with the first absorber 26 and the second absorber 28. The resonator 50 is sandwiched between the first absorber 26 and the second absorber 28 in the z-direction.

[0072] The resonator 50 is made of a conductor. The resonator 50 can, for example, use the same material as the center conductor 10.

[0073] Figure 7 The resonator 50 shown is, for example, symmetrical in the x-direction with respect to the center line CL1. The center line CL1 is a line that passes through the center of the straight line connecting the first terminal T1 and the second terminal T2 and is orthogonal to the straight line. The resonator 50 symmetrical with respect to the center line CL1 is easy to form and has excellent versatility.

[0074] The first magnetic body 25 and the first absorber 26 are located at different positions in the xy plane when viewed from the z direction. Similarly, the second magnetic body 27 and the second absorber 28 are located at different positions in the xy plane when viewed from the z direction. The first magnetic body 25 and the second magnetic body 27 are located at a position overlapping with the first region 11 of the central conductor 10 in the z direction. The first magnetic body 25 and the second magnetic body 27 sandwich the first region 11 in the z direction. The first absorber 26 and the second absorber 28 are located at a position overlapping with the second region 12 of the central conductor 10 and the resonator 50 in the z direction. The first absorber 26 and the second absorber 28 sandwich the second region 12 and the resonator 50 in the z direction.

[0075] The shapes of the first magnetic body 25 and the second magnetic body 27 are not limited as long as they can cover the first region 11. The shapes of the first absorber 26 and the second absorber 28 are not limited as long as they can cover the second region 12 and the resonator 50. For example, they could also be... Figure 3 As shown, the first magnetic body 25 and the first absorber 26 are both rectangular in shape when viewed from the z-direction.

[0076] By applying a DC magnetic field to the first magnetic body 25 and the second magnetic body 27, the high-frequency signal passing through the central conductor 10 is transmitted with a unilateral offset in the direction of travel. For example, the high-frequency signal input from the first terminal T1 is offset towards the vicinity of the first connecting line S1 and transmitted along the first connecting line S1 to the second terminal T2. On the other hand, the high-frequency signal input to the second terminal T2 is offset towards the vicinity of the second connecting line S2 and transmitted along the second connecting line S2 to the first terminal T1. At this time, the high-frequency signal input to the second terminal T2 is absorbed by the first absorber 26 and the second absorber 28, and is attenuated to a large extent. In addition, the high-frequency signal input to the second terminal T2 is captured by the resonator 50, and the intensity of the high-frequency signal captured by the resonator 50 is attenuated to a large extent.

[0077] The first magnetic body 25 and the second magnetic body 27 comprise magnetic materials. The first magnetic body 25 and the second magnetic body 27 can be conductors or insulators. The first magnetic body 25 and the second magnetic body 27, for example, are soft magnetic materials. The first magnetic body 25 and the second magnetic body 27, for example, comprise materials selected from Co-based amorphous materials, ferrites, and Fe... 85 Si2B8P4Cu, Fe 86 AlB8P4Cu, Fe 78 Si9B 13 Any of the groups consisting of yttrium iron garnet (YIG). Examples of YIG include Y3Fe2(FeO4)3 and Y3Fe5O. 12 .

[0078] The first magnetic material 25 and the second magnetic material 27 can also be formed by mixing magnetic particles with resin. Magnetic particles may include, for example, iron, silicon steel (Fe-Si), permalloy (Ni-Fe), perminite (Fe-Co), iron-silicon-aluminum magnetic alloy (Fe-Si-Al), electromagnetic stainless steel, amorphous iron-based alloys (Fe-BC system, Fe-Co system), manganese-zinc ferrite, nickel-zinc ferrite, etc. The first magnetic material 25 and the second magnetic material 27 can also be formed by mixing ferrite particles with resin.

[0079] When dispersing magnetic materials within insulating materials (such as resins, rubbers, coatings, etc.), it is preferable to set the volume ratio of the magnetic material to be 10% or more and 70% or less. If the volume of the magnetic material is relatively small, its electromagnetic wave absorption capacity is relatively low. If the volume of the magnetic material is relatively large, it is difficult to disperse it into the insulating material.

[0080] The first absorber 26 and the second absorber 28 contain materials whose magnetic field loss rate is greater than that of the first magnet 25 and the second magnet 27. The first absorber 26 and the second absorber 28 contain, for example, any material selected from the group consisting of iron, BN, conductive carbon, SiC, and Ni-based ferrites.

[0081] When the first loss layer 21 and the second loss layer 22 are conductors, an insulating layer is provided between the first loss layer 21 and the center conductor 10, and between the second loss layer 22 and the center conductor 10. A known insulating layer can be used.

[0082] The first magnet 31 and the second magnet 32 ​​sandwich the center conductor 10, the first loss layer 21, and the second loss layer 22 in the z-direction. The first magnet 31 and the center conductor 10 sandwich the first loss layer 21 in the z-direction. The second magnet 32 ​​and the center conductor 10 sandwich the second loss layer 22 in the z-direction. The first magnet 31 and the second magnet 32 ​​apply a DC magnetic field to the first magnetic body 25 and the second magnetic body 27.

[0083] Figure 8 This diagram is a top-down view of the lower housing 42 and the second magnet 32. When viewed from the z-direction, the first magnet 31 and the second magnet 32 ​​overlap with the first magnetic body 25 and the second magnetic body 27. Alternatively, portions of the first magnet 31 and the second magnet 32 ​​may overlap with the first absorber 26 and the second absorber 28 when viewed from the z-direction.

[0084] The first magnet 31 and the second magnet 32 ​​are, for example, hard magnetic materials. The first magnet 31 and the second magnet 32 ​​can be either insulators or conductors. The first magnet 31 and the second magnet 32 ​​may include, for example, any of the following groups: ferrite magnets with insulating properties, rare-earth magnets with conductive properties, TbFeCo, GdFeCo, SmFeCo, [Co / Pt] multilayer films, and [Co / Pd] multilayer films. If the first magnet 31 and the second magnet 32 ​​are conductors, the upper housing 41 and the lower housing 42 may be omitted.

[0085] The first magnet 31 and the second magnet 32 ​​are examples of magnetic field sources. The magnetic field source is not limited to the first magnet 31 and the second magnet 32, as long as it can apply a DC magnetic field to the first magnet 25 and the second magnet 27 through the upper housing 41 and the lower housing 42 respectively.

[0086] The irreversible circuit element 100 of this embodiment has excellent isolation characteristics due to the presence of the resonator 50. The resonator 50 encloses a portion of the high-frequency signal input from the second terminal T2 within the resonator 50, preventing the high-frequency signal input from the second terminal T2 from reaching the first terminal T1. The lower the intensity of the high-frequency signal reaching the first terminal T1 from the second terminal T2, the higher the isolation characteristics of the irreversible circuit element 100.

[0087] The irreversible circuit element 100 of this embodiment can be applied, for example, to a quantum computer. Figure 10This is a schematic diagram of a quantum computer according to this embodiment. The quantum computer 200 includes, for example, a quantum processor 201, irreversible circuit elements 202 and 203, filters 204 and 205, and an amplifier 206.

[0088] Quantum processor 201 performs quantum computing. Irreversible circuit elements 202 and 203 deliver read signals of qubits from quantum processor 201. Irreversible circuit element 202 is a circulator. Irreversible circuit element 203 is an isolator. Irreversible circuit element 100 of this embodiment can be applied to irreversible circuit element 203. Amplifier 206 amplifies the read signals.

[0089] For example, superconducting quantum computers operate under extremely low temperature conditions. Therefore, the quantum processor 201 and irreversible circuit elements 202 and 203 are also positioned in environments exposed to extremely low temperatures. Maintaining a large volume of space in extremely low-temperature environments is difficult, necessitating miniaturization of the irreversible circuit elements 202 and 203. The irreversible circuit element 100 in this embodiment is small and has excellent heat dissipation, thus enabling high performance and stable operation of the quantum computer.

Claims

1. An irreversible circuit element, characterized in that, The irreversible circuit element includes a conductor, a loss layer disposed on the outside of the conductor, and a housing disposed on the outside of the loss layer. The loss layer has a magnetic material and an absorber. The conductor has a first terminal and a second terminal for input and output signals, a first region that overlaps with the magnetic body when viewed from the thickness direction and is continuous between the first terminal and the second terminal, and a second region that overlaps with the absorber when viewed from the thickness direction. The conductor irreversibly transmits the signals between the first terminal and the second terminal. At least a portion of the conductor is a superconductor.

2. The irreversible circuit element according to claim 1, characterized in that, The superconductor is any one of aluminum, niobium, and tantalum.

3. The irreversible circuit element according to claim 1, characterized in that, The superconductor is aluminum with a purity of 99.99% or higher.

4. The irreversible circuit element according to claim 1, characterized in that, The conductor is a component made by plating phosphor bronze with aluminum, niobium, or tantalum.

5. The irreversible circuit element according to claim 1, characterized in that, The surfaces of the first terminal and the second terminal have a metal coating.

6. The irreversible circuit element according to claim 5, characterized in that, The metal coating is any one of nickel, tin, copper, and silver.

7. The irreversible circuit element according to claim 1, characterized in that, The shell is made of a highly thermally conductive material having a thermal conductivity of over 300 W / m·K at extremely low temperatures.

8. The irreversible circuit element according to claim 7, characterized in that, The high thermal conductivity material is any one of gold, silver, copper, platinum, palladium, indium, and aluminum.

9. The irreversible circuit element according to claim 7, characterized in that, The high thermal conductivity material is copper with a purity of over 99.99%.

10. A quantum computer, characterized in that, The quantum computer comprises the irreversible circuit elements as described in any one of claims 1 to 9.

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