Irreversible circuit element and quantum computer

Abstract

The invention provides an irreversible circuit element and a quantum computer. The irreversible circuit element has sufficient heat dissipation 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 region that overlaps the first magnetic body and the second magnetic body when viewed from the thickness direction, and a region that overlaps the first absorber and the second absorber when viewed from the thickness direction. The irreversible circuit element is further provided with an insulating first adhesive layer and a second adhesive layer having a linear expansion coefficient of 35 * 10 <-6 > / K or less at extremely low temperatures, and the first case and the second case are bonded to the first loss layer and the second loss layer, respectively.

Description

Technical Field

[0001] This invention relates to irreversible circuit elements and quantum computers. Background Technology

[0002] Irreversible circuit elements are components that limit the direction of transmission of high-frequency signals. Isolators and circulators are examples of irreversible circuit elements. Irreversible circuit elements are widely used in circuits that transmit high-frequency signals.

[0003] Irreversible circuit elements are used in a wide variety of applications where high-frequency signals are used. For example, Patent Document 1 discloses an isolator that uses a frequency band of several GHz to about 10 GHz.

[0004] Isolators are also used in quantum computers. In various quantum computers, and in the currently most advanced superconducting quantum computers, isolators that function at extremely low temperatures are required for accurate measurement of qubits.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: International Publication No. 2023 / 238310 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] The isolator is placed in the coldest part of the cryo-system of a superconducting quantum computer, closest to the qubit.

[0010] Isolators achieve their isolation properties by converting high-frequency signals into heat, thus inevitably generating heat. Therefore, in order to maintain the extremely low temperature environment around the qubit, the heat generated in the isolator needs to be dissipated rapidly.

[0011] However, the irreversible circuit element disclosed in Patent Document 1 is based on the construction of an isolator that functions at room temperature, which has the problem of insufficient heat dissipation in extremely low temperature environments.

[0012] The present invention was made to solve such existing problems, and its purpose is to provide an irreversible circuit element with sufficient heat dissipation in extremely low temperature environments and a quantum computer having the irreversible circuit element.

[0013] means for solving problems

[0014] To address the aforementioned problems, the present invention provides the following means.

[0015] The irreversible circuit element of this embodiment includes a conductor, a loss layer disposed outside the conductor, and a housing disposed outside the loss layer. The loss layer has a magnetic material and an absorber. The conductor has a region overlapping the magnetic material when viewed in the thickness direction and a region overlapping the absorber when viewed in the thickness direction. The irreversible circuit element also includes an insulating adhesive layer having a density of 35 × 10⁻⁶ at extremely low temperatures. -6 A linear expansion coefficient below / K is used to bond the housing and the loss layer together.

[0016] The effects of the invention

[0017] The present invention provides an irreversible circuit element with sufficient heat dissipation in extremely low temperature environments and a quantum computer having the irreversible circuit element. Attached Figure Description

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

[0019] Figure 2 This is a top view of an irreversible circuit element according to an embodiment of the present invention.

[0020] Figure 3 This is a top view of the loss layer and frame of an irreversible circuit element according to an embodiment of the present invention.

[0021] Figure 4 This is a top view of the adhesive layer and frame of the irreversible circuit element according to an embodiment of the present invention.

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

[0023] Figure 6 This is a top view showing the state in which the loss layer of the irreversible circuit element in an embodiment of the present invention is divided into multiple fragments.

[0024] Figure 7 This is a top view of the center conductor and resonator of the irreversible circuit element according to an embodiment of the present invention.

[0025] Figure 8 This is a top view of the housing and magnet of the irreversible circuit element according to an embodiment of the present invention.

[0026] Figure 9 It is a table that represents the physical properties of various materials.

[0027] Figure 10 This is a schematic diagram of a quantum computer according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 10. Center conductor; 11. Region 1; 12. Region 2; 14. Metal coating; 21. First loss layer; 22. Second loss layer; 25. First magnetic material; 26. First absorber; 27. Second magnetic material; 28. Second absorber; 31. First magnet; 32. Second magnet; 41. Upper shell; 41a, 41b. Heat dissipation surface; 42. Lower shell; 42a, 42b. Heat dissipation surface; 50. Resonator; 61. First frame; 62. 63, 64, gaps; 71, first adhesive layer; 72, second adhesive layer; 100, irreversible circuit element; 200, quantum computer; 201, quantum processor; 202, 203, irreversible circuit element; 204, 205, filter; 206, amplifier; S1, first connecting line; S2, second connecting line; S21, first side; S22, second side; S23, third side; T1, first terminal; T2, second terminal. Detailed Implementation

[0030] The following description uses the accompanying drawings to illustrate embodiments of the irreversible circuit elements and quantum computer of the present invention. Note that the aspect ratios of the constituent elements in the drawings may not necessarily match the actual aspect ratios.

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

[0032] Figure 2 This is a top view of the irreversible circuit element 100 of this embodiment. In this specification, the direction from the first terminal T1 of the center conductor 10 toward the second terminal T2 is defined as the x-direction, the direction orthogonal to the x-direction in the plane extending from the center conductor 10 is defined as the y-direction, and the direction orthogonal to both the x- and y-directions is defined as the z-direction. The thickness direction of each layer is an example of the z-direction. Furthermore, regarding the z-direction, the side where the upper housing 41 exists is defined as the upper side, and the side where the lower housing 42 exists is defined as the lower side.

[0033] Figure 2 The figure is obtained by removing the first loss layer 21, the first magnet 31, the upper housing 41 and the lower housing 42 from the irreversible circuit element 100 and viewing the center conductor 10, the second loss layer 22 and the second frame 62 from above. Figure 1 It means along 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 the top side 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. This gap 63 is used to store the remaining portion of the adhesive generated when the upper housing 41 and the first loss layer 21 are bonded using the first adhesive layer 71. That is, the first adhesive layer 71 is formed to extend 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. This gap 64 is used to store the remaining portion of the adhesive generated when the lower housing 42 and the second loss layer 22 are bonded using the second adhesive layer 72. That is, the second adhesive layer 72 is formed to extend 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 suppress the first adhesive layer 71 from entering the portion other than the gap 63 between the opposite surfaces of the first frame 61 and the first magnetic body 25 along the z direction, between the opposite surfaces of the first frame 61 and the first absorber 26 along the z direction, and between the opposite surfaces of the first magnetic body 25 and the first absorber 26 along the z direction.

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

[0053] Therefore, by storing the first adhesive layer 71 and the second adhesive layer 72 in the gaps 63 and 64, the first magnetic body 25 and the first absorber 26, as well as the second magnetic body 27 and the second absorber 28, are in close contact with each other, thereby stabilizing the isolation characteristics of the irreversible circuit element 100.

[0054] Figure 7 This is a top view of the center conductor 10 and resonator 50 of the irreversible circuit element 100 in this embodiment.

[0055] The center conductor 10 has a first terminal T1 and a second terminal T2 for inputting and outputting high-frequency signals. The first terminal T1 and the second terminal T2 are connected to external terminals.

[0056] The surfaces of the first terminal T1 and the second terminal T2 may also be covered with a metal coating of any of the metals such as nickel (Ni), tin, copper, and silver. For example, by plating these metals onto the surfaces of the first terminal T1 and the second terminal T2 to form a metal coating 14, wettability, connection strength, and conductivity can be ensured when the first terminal T1 and the second terminal T2 are soldered to external terminals.

[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 region that overlaps with the magnetic body when viewed from the thickness direction and a second region that overlaps with the absorber when viewed from the thickness direction. This irreversible circuit element also features an insulating adhesive layer that has a strength of 35 × 10⁻⁶ at extremely low temperatures. -6 A linear expansion coefficient below / K is used to bond the housing and the loss layer together.

2. The irreversible circuit element according to claim 1, characterized in that, The loss layer is divided into multiple fragments within its plane.

3. The irreversible circuit element according to claim 1, characterized in that, The irreversible circuit element also has an insulating frame disposed between the housings, surrounding the loss layer. The adhesive layer is formed to extend between the frame and the loss layer.

4. The irreversible circuit element according to claim 3, characterized in that, The adhesive layer is composed of an insulating adhesive. A gap is formed between the frame and the loss layer to store the remaining portion of the adhesive.

5. 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.

6. The irreversible circuit element according to claim 5, characterized in that, The high thermal conductivity material is copper with a purity of over 99.99%.

7. The irreversible circuit element according to claim 1, characterized in that, The conductor has a first terminal and a second terminal for input and output signals, and the signals are irreversibly transmitted between the first terminal and the second terminal.

8. The irreversible circuit element according to claim 1, characterized in that, The housing has a heat dissipation surface that allows heat generated in the conductor and the loss layer to dissipate.

9. The irreversible circuit element according to claim 8, characterized in that, The housing is mounted on an extremely low-temperature plate that serves as a heat bath inside the refrigeration unit, separated from the heat dissipation surface.

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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