Superconductive filament core coaxial cable

Abstract

To provide a coaxial cable having a superconductive filament core, a method of manufacturing such coaxial cable, a method of using one or more of such coaxial cable and a system comprising one or more of such coaxial cable.SOLUTION: A coaxial cable comprises an inner conductor (or core), an outer conductor, and an insulator. The outer conductor is made of a first electroconductive material. The insulator is provided between the inner conductor and the outer conductor. The inner conductor comprises a filament and a mantle (or matrix). The filament is made of a second electroconductive material. The mantle is made of a third electroconductive material and the mantle surrounds the filament. The filament, in particular the second electroconductive material, comprises a superconductive material.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to coaxial cables having superconducting filament cores, methods of making such coaxial cables, and methods of using one or more of such coaxial cables. [Background technology]

[0002] Quantum effects are used in novel applications. These applications are realized in cryogenic systems, such as quantum sensing systems or quantum computing systems (quantum computers). In such cryogenic systems, superconducting signal lines, specifically superconducting coaxial cables, are used to transmit signals containing DC current components. A major concern in such cryogenic systems is Joule heating of the superconducting signal lines.

[0003] For example, in the case of quantum computers, it is necessary to provide a quantum processing unit containing one or more qubits. This is currently done via a superconducting quantum processor. In such a processor, multiple transmission lines realized by multiple coaxial cables are connected in series to a signal generator. The coaxial cables comprise a superconducting inner conductor or core, an insulator, and a superconducting outer conductor. The coaxial cables are further connected to each other and to the signal generator by connectors.

[0004] Coaxial cables are very expensive due to the high cost of the superconducting materials that make up the inner and outer conductors. Furthermore, special cost-intensive and labor-intensive joining processes, such as gold plating, must be applied to join the superconducting material of the coaxial cable with the connector. In addition to the high cost of the coaxial cable and the joining process, the joint between the coaxial cable and the connector is prone to error. Summary of the Invention [Problem to be solved by the invention]

[0005] The subject of the present invention is to obviate or at least mitigate the above-mentioned drawbacks and problems. Furthermore, there is provided a coaxial cable according to a first aspect of the invention, which is the subject of independent claim 1, a method for manufacturing a coaxial cable according to a second aspect of the invention, a method for using a coaxial cable according to a third aspect of the invention, and a system comprising a coaxial cable according to a fourth aspect of the invention, which are the subject of further independent claims. Improvements and further developments of the invention are the subject of the respective dependent claims. [Means for solving the problem]

[0006] A coaxial cable according to a first aspect of the present invention comprises an inner conductor (or core), an outer conductor, and an insulator. The outer conductor is made of a first conductive material. An insulator is provided between the inner and outer conductors. The inner conductor comprises a filament and a mantle (or matrix). The filament is made of a second conductive material. The mantle is made of a third conductive material, and the mantle surrounds (or embeds) the filament. The filament, and in particular the second conductive material, comprises a superconducting material.

[0007] The coaxial cable according to the first aspect of the present invention is a superconducting filament core coaxial cable. The inner conductor or core of the coaxial cable according to the first aspect of the present invention is a superconducting filament core.

[0008] A method of manufacturing a coaxial cable according to a second aspect of the present invention includes the steps of providing a filament, surrounding the filament with a mantle, coating the inner conductor, and encasing the insulation with the outer conductor. In the step of providing a filament, a filament made of a second conductive material is provided. The second conductive material includes a superconducting material. In the step of surrounding the filament with a mantle, the filament is surrounded by a mantle (or matrix) made of a third conductive material to form the inner conductor (or core). In the step of coating the inner conductor with an insulation, the inner conductor is coated with the insulation. In the step of encasing the insulation with the outer conductor, the insulation is encased by the outer conductor made of the first conductive material.

[0009] The method according to the second aspect of the present invention may in particular be a method for manufacturing a coaxial cable according to the first aspect of the present invention, ie a superconducting filament core coaxial cable.

[0010] In a method according to a third aspect of the present invention, one or more coaxial cables according to the first aspect of the present invention are used in a quantum device, particularly a quantum computer in a quantum processing unit (QPU) of the quantum computer, and the coaxial cables are particularly used to provide transmission lines for providing signals to qubits of the QPU.

[0011] A system according to a fourth aspect of the invention comprises one or more coaxial cables according to the first aspect of the invention for providing a transmission line for providing signals to the qubits.

[0012] The coaxial cable according to the first aspect of the invention, manufactured according to the second aspect of the invention, used according to the third aspect of the invention, and configured by the system according to the fourth aspect of the invention is a coaxial transmission line particularly suitable for signals comprising DC current with a higher frequency overlay, the coaxial cable further providing a superconducting transmission line as needed, for example to provide signals to qubits in quantum computing.

[0013] An inner conductor or core filament made of a second conductive material may be provided along the centerline of the coaxial cable.

[0014] The second conductive material includes, or specifically is, a superconductive or superconducting material that provides superconductivity below a certain temperature. The terms superconducting and superconducting are used synonymously in the context of the present invention. A superconducting material may be any material that provides superconducting properties, such as a superconducting metal, ceramic, organic material, or heavily doped semiconductor that conducts electricity without resistance. Specifically, the superconducting material may be a high-temperature superconducting material, in other words, a high-temperature superconductor (HTS). Thus, a filament made of the second conductive material can provide superconductivity when provided with appropriate cooling, and thus provide a transmission line suitable for use in cryogenic systems and quantum applications, such as quantum sensing systems or quantum computers.

[0015] The filaments are surrounded by or embedded in a mantle or matrix made of a third conductive material. Specifically, the filaments may be surrounded / embedded in a mantle / matrix such that the second conductive material (superconducting material) is circumferentially surrounded by a third conductive material (non-superconducting). The filaments and mantle / matrix may provide a concentric structure of the inner conductor / core in the cross-sectional direction.

[0016] The third conductive material may be a common conductive material such as a metal, alloy, or semiconductor that does not provide superconductivity when cryogenically cooled (e.g., with liquid N2 or liquid He). In other words, the third conductive material may be a "non-superconducting" material. Thus, the mantle or matrix can be joined to the connector using common welding or soldering techniques.

[0017] The mantle, or rather the inner conductor, is covered or coated with an insulator. Specifically, the insulator may circumferentially cover the inner conductor. The insulator and the inner conductor may form a concentric structure in the cross-sectional direction. Specifically, the filament, the mantle, and the insulator may form a concentric structure in the cross-sectional direction.

[0018] The insulator may be made of any dielectric material, such as a synthetic material or ceramics, including, in particular, polytetrafluoroethylene (PTFE), polyethylene (PE), polyamide (PA), perfluoroalkoxy (PFA), etc.

[0019] The inner conductor may be in direct contact with the insulator, or alternatively, the inner conductor may not be in direct contact with the insulator, and one or more additional layers may be provided between the inner conductor and the insulator.

[0020] The insulator is wrapped with an outer conductor made of a first conductive material. Specifically, the outer conductor may circumferentially surround the insulator. The insulator electrically and spatially separates the inner conductor from the outer conductor. The outer conductor and the insulator may form a concentric structure in the cross-sectional direction. Specifically, the inner conductor, or rather the filament and mantle, the insulator, and the outer conductor may form a concentric structure in the cross-sectional direction.

[0021] The first conductive material may be a common conductive material, such as a metal, alloy, or semiconductor, that does not exhibit superconductivity when cooled with liquid Ni or liquid He. In other words, the first conductive material may be a "non-superconducting" material. Therefore, the outer conductor can be joined to the connector using common welding or soldering techniques.

[0022] The insulator may be in direct contact with the outer conductor, or the insulator may not be in direct contact with the outer conductor, and one or more additional layers may be provided between the insulator and the outer conductor.

[0023] The inner core, or rather the superconducting filament core, of the coaxial cable according to the present invention provides superconductivity and can be used as a transmission line with minimal Joule heating. Therefore, the coaxial cable according to the present invention is particularly suitable for use in cryogenic systems and quantum applications, such as quantum sensing and quantum computing. Furthermore, the coaxial cable according to the present invention is significantly cheaper than a typical superconducting coaxial cable, since only a relatively small amount of superconducting material is required to provide the filament. The remaining conductive parts are made of much cheaper "non-superconducting" materials. Furthermore, the coaxial cable according to the present invention can be easily and reliably joined to a connector, since common joining processes such as welding or soldering can be used.

[0024] According to a refinement of the invention, the first conductive material comprises copper (Cu), a copper alloy (e.g., copper-nickel (cupronickel, CuNi) or phosphor bronze), stainless steel, silver-plated stainless steel, or tungsten (Wolfram, W), or a combination thereof.

[0025] According to a refinement of the invention, the third conductive material comprises copper (Cu), a copper alloy (e.g., copper-nickel (cupronickel, CuNi) or phosphor bronze), stainless steel, silver-plated stainless steel, or tungsten (Wolfram, W), or a combination thereof.

[0026] According to a refinement of the invention, the first conductive material and the third conductive material are the same or different.

[0027] Providing the first and / or third conductive material from copper (Cu), a copper alloy, (silver-plated) stainless steel, or tungsten (W), or a combination thereof, results in a particularly easy and reliable processability of the coaxial cable, as well as a low cost.

[0028] According to a refinement of the invention, the filament comprises two or more layers of a second conductive material containing a superconducting material.

[0029] The filament may comprise two or more concentric layers of different second conductive materials, including different superconducting materials. The layers may have alternating or mutually different second conductive layers including different superconducting materials.

[0030] By using a different second conductive material for the filament, the properties of the filament can be specifically fine-tuned.

[0031] According to the improvement of the present invention, the superconducting material comprises a niobium alloy, in particular niobium-titanium (NbTi), niobium-tantalum (NbTa), niobium-tin (Nb3Sn), or a combination thereof.

[0032] Niobium alloys offer excellent superconductivity and good processability for drawing filaments.

[0033] According to a refinement of the invention, the diameter of the filament is between 1% and 95% of the diameter of the inner conductor.

[0034] Depending on the amperage of the current introduced into the filament, the diameter of the filament can be selected to a suitable size without changing the overall diameter of the inner conductor, which provides high adaptability without changing the layout of the respective system.

[0035] According to a refinement of the invention, the coaxial cable may further comprise an outer insulation surrounding the outer conductor.

[0036] According to a further refinement of the invention, the method may further comprise the step of sheathing the outer conductor with an outer insulation.

[0037] The outer conductor may be partially or completely sheathed or coated with an outer insulation. Specifically, the outer insulation may circumferentially surround the outer conductor. The outer insulation and the outer conductor may form a concentric structure in the cross-sectional direction.

[0038] The outer insulator may be made of any dielectric material, such as a synthetic material or ceramic, including, in particular, polytetrafluoroethylene (PTFE), polyethylene (PE), polyamide (PA), perfluoroalkoxy (PFA), etc.

[0039] The outer conductor may be in direct contact with the outer insulation, or alternatively, the outer conductor may not be in direct contact with the outer insulation, and one or more additional layers may be provided between the outer conductor and the outer insulation.

[0040] The outer insulation provides more safety and protection for the outer conductor.

[0041] According to a refinement of the invention, the inner conductor comprises only one filament surrounded by a mantle.

[0042] According to a further refinement of the present invention, in the step of providing the filament, only one filament is provided, and further, in the step of surrounding the filament with a mantle, only one filament is surrounded by the mantle.

[0043] One filament is sufficient to provide the superconductivity necessary for a transmission line suitable for use in applications requiring signals containing DC current with a higher frequency overlay, such as quantum sensing or quantum computing.

[0044] Therefore, a coaxial cable with only one filament with superconductivity in the inner conductor offers the best cost-value ratio for quantum applications.

[0045] According to a refinement of the invention, the inner conductor comprises a plurality of filaments surrounded by a mantle.

[0046] According to a further refinement of the invention, the step of providing a filament comprises providing a plurality of filaments, and the step of surrounding the filament with a mantle comprises surrounding the plurality of filaments with a mantle.

[0047] The number of filaments, the (different) diameters of the filaments, and the (different) materials of the filaments can be selected based on the respective requirements of the system in which the coaxial cable is used. Furthermore, the multiple filaments can be arranged in different ways along the cross section of the inner conductor within the mantle or matrix. For example, the filaments can be arranged in a circular, octagonal, hexagonal, rectangular, or triangular shape with one or more central filaments and one or more surrounding rings, octagonal, hexagonal, rectangular, or triangular shapes of filaments.

[0048] Multiple filaments within the inner conductor provide maximum flexibility for different applications.

[0049] According to a refinement of the invention, at least two filaments of the plurality of filaments are made of different second conductive materials, including different superconducting materials.

[0050] By selecting different second conductive materials, including different superconducting materials, the properties of the coaxial cable can be fine-tuned to suit the needs of each superior system.

[0051] The following preferred embodiments and configurations of the present invention will be described in more detail with reference to the accompanying drawings to provide a better understanding of the present invention. These embodiments and configurations are merely exemplary and should not be construed as limiting the scope of protection. Rather, the enclosed claims exclusively define the scope of protection. [Brief explanation of the drawings]

[0052] [Figure 1] 1 shows a first exemplary embodiment of a coaxial cable according to a first aspect of the present invention; [Figure 2a] FIG. 2 shows a second exemplary embodiment of a coaxial cable according to the first aspect of the present invention. [Figure 2b] FIG. 2 shows a second exemplary embodiment of a coaxial cable according to the first aspect of the present invention. [Figure 3] 4 is a flowchart illustrating an exemplary method for manufacturing a coaxial cable according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0053] 1 shows a coaxial cable 10, specifically a superconducting filament core coaxial cable. Different portions of the coaxial cable 10 are shown partially "uncovered" or "stripped." However, this is only for better presentation of each portion of the coaxial cable 10 and does not represent a default configuration.

[0054] The coaxial cable 10 comprises an inner conductor, an insulator 3, and an outer conductor 4. The inner conductor comprises filaments 1 and a mantle or matrix 2. The filaments 1 and mantle 2 of the inner conductor are arranged in a concentric configuration in the direction of the cross section of the inner conductor. The inner conductor, i.e., the filaments 1 and mantle 2, as well as the insulator 3 and outer conductor 4, are arranged in a concentric configuration in the direction of the cross section of the coaxial cable 10.

[0055] A filament 1 is provided along the centerline of coaxial cable 10. Filament 1 is made of a second conductive material that includes, or specifically is, a superconducting material. Filament 1 provides the superconductivity necessary to provide a transmission line suitable for use in cryogenic systems or quantum applications, specifically quantum computers.

[0056] The filament 1 is partially or completely surrounded by or embedded in a mantle 2. The mantle 2 is made of a third conductive material that is a "non-superconducting" material, i.e., a common conductive material such as a metal, alloy, semiconductor, etc. that does not provide superconductivity when cooled to a low temperature. Optionally, the mantle 2 can be made of two or more third conductive materials, i.e., different third conductive materials. The mantle 2 can be easily joined with a connector by welding or soldering.

[0057] The mantle 2, or rather the inner conductor, is covered or coated with an insulator 3. The insulator 3 is made of a dielectric material. The inner conductor and the outer conductor 4 are spatially and electrically separated by the insulator 3.

[0058] The outer conductor 4 surrounds the insulator 3 and is made of a first conductive material that is "non-superconducting." The first and third conductive materials may be the same or different materials. The outer conductor 4 can be easily joined to a connector by welding or soldering.

[0059] Coaxial cable 10 provides superconductivity, for example, to provide a transmission line within a quantum processor of a quantum computer using a very small amount of superconducting material. Therefore, the cost of coaxial cable 10 is significantly lower than that of typical superconducting coaxial cables. Furthermore, compared to the labor-intensive and expensive special joining processes required for typical superconducting cables (e.g., gold plating), coaxial cable 10 can be more easily and reliably joined to connectors by common joining processes such as welding or soldering.

[0060] 2a and 2b, a coaxial cable 11, specifically a superconducting filament core coaxial cable, is shown. The coaxial cable 11 differs from the coaxial cable of FIG. 1 above only in the structure of the inner conductor. Therefore, to avoid redundant explanation, only the differences between the two coaxial cables are described below. In FIG. 2a, different portions of the coaxial cable 11 are shown partially "uncovered" or "stripped." However, this is merely for better presentation of each portion of the coaxial cable 11 and does not represent the default configuration.

[0061] The coaxial cable 11 comprises an inner conductor, an insulator 3, and an outer conductor 4. The inner conductor comprises a plurality of filaments 1a...1i and a mantle or matrix 2.

[0062] Here, nine filaments 1a...1i are provided in the inner conductor. However, this number of filaments is merely an example, and the inner conductor may be provided with a plurality of filaments less than or greater than nine. The filaments 1a...1i of the inner conductor and the mantle 2 are arranged in a concentric circular configuration in the cross-sectional direction of the inner conductor. The nine filaments are arranged in a circular configuration in the cross-sectional direction of the inner conductor, while one central filament 1i is surrounded by eight filaments 1a...1h arranged along a circle. The inner conductor, i.e., the plurality of filaments 1a...1i and the mantle 2, as well as the insulator 3 and the outer conductor 4, are arranged in a concentric circular configuration in the cross-sectional direction of the coaxial cable 11.

[0063] Filaments 1a...1i are made of a second conductive material that includes, or specifically is, a superconducting material. Each filament may be of a different diameter and / or may be of a different second conductive material that includes, or specifically is, a different superconducting material. Filaments 1a...1i provide the superconductivity necessary to provide a transmission line suitable for use in cryogenic systems and quantum applications such as quantum computers.

[0064] The plurality of filaments 1a...1i are partially or completely surrounded or embedded in a mantle 2. The mantle 2 is made of a third conductive material, which is a "non-superconducting" material. Optionally, the mantle 2 can be made of two or more third conductive materials, i.e., different third conductive materials. The mantle 2 can be easily joined with a connector by welding or soldering.

[0065] Coaxial cable 11 offers the same advantages as the coaxial cable of FIG. 1 above, and additionally offers better stability of the superconducting state in high magnetic field environments, and greater stability at higher currents.

[0066] A flowchart illustrating a method for manufacturing a coaxial cable is shown in Figure 3. The method includes step 21 of providing a filament, step 22 of surrounding the filament with a mantle, step 23 of covering the inner conductor with insulation, and step 24 of wrapping the insulation with an outer conductor, as well as the optional step 25 of sheathing the outer conductor with an outer insulation. Some or all of steps 21-25 may or may not occur simultaneously as the cable is put together.

[0067] In the step of providing filaments 21, filaments made of a second conductive material are provided. The second conductive material includes, or specifically is, a superconducting material. Either only one filament or multiple filaments, i.e., two or more filaments, can be provided. The filaments of the multiple filaments can be made of different second conductive materials, including different superconducting materials. The additional diameter of one or more of the filaments, or each of them, can be different from the remaining filaments.

[0068] In Surround Filament with Mantle step 22, the filament or filaments are surrounded by a mantle or matrix made of a third conductive material to form an inner conductor. The third conductive material is a "non-superconducting" material.

[0069] In a cover inner conductor step 23, the inner conductor is covered or coated with an insulator, which may be made of any dielectric material.

[0070] In step 24 of wrapping the insulator, the insulator is wrapped with an outer conductor made of a first conductive material. The first conductive material is a "non-superconducting" material. The first and third conductive materials may be the same material or different materials.

[0071] In optional step 25 of sheathing the outer conductor, the outer conductor is sheathed or coated with an outer insulation, which may be made of any dielectric material.

[0072] Coaxial cables manufactured by the method according to Figure 3 offer the same advantages as the coaxial cables of Figures 1 and 2a and 2b, as described above.

Claims

1. A coaxial cable (10, 11), an inner conductor; an outer conductor (4) made of a first conductive material; an insulator (3) provided between the inner conductor and the outer conductor; The inner conductor is a filament (1) made of a second conductive material; a mantle (2) made of a third conductive material surrounding the filament; The filament (1), in particular the second conductive material, comprises a superconducting material.

2. 2. The coaxial cable (10, 11) of claim 1, wherein the first conductive material comprises copper (Cu), a copper alloy, stainless steel, silver-plated stainless steel, or tungsten (W), or a combination thereof.

3. 2. The coaxial cable (10, 11) of claim 1, wherein the third conductive material comprises copper (Cu), a copper alloy, stainless steel, silver-plated stainless steel, or tungsten (W), or a combination thereof.

4. 2. The coaxial cable (10, 11) of claim 1, wherein the first conductive material and the third conductive material are the same or different.

5. 2. The coaxial cable (10, 11) of claim 1, wherein the filament (1) comprises two or more layers of a second conductive material comprising a superconducting material.

6. The coaxial cable (10, 11) of claim 1, wherein the superconducting material comprises a niobium alloy, in particular niobium-titanium NbTi, niobium-tantalum NbTa, niobium-tin Nb3Sn, or a combination thereof.

7. 2. The coaxial cable (10, 11) according to claim 1, wherein the diameter of the filament (1) is 1% to 95% of the diameter of the inner conductor.

8. The coaxial cable (10, 11) according to claim 1, further comprising an outer insulation surrounding the outer conductor (4).

9. 2. The coaxial cable (10) of claim 1, wherein the inner conductor comprises only one filament (1) surrounded by the mantle (2).

10. 2. The coaxial cable (11) according to claim 1, wherein the inner conductor comprises a plurality of filaments (1a...1i) surrounded by the mantle (2).

11. 11. The coaxial cable (11) according to claim 10, wherein at least two filaments of the plurality of filaments (1a...1i) are made of different second conductive materials, including a superconducting material.

12. A method for manufacturing a coaxial cable (10), in particular a coaxial cable according to any one of claims 1 to 11, comprising: Providing (21) a filament (1) made of a second conductive material, the second conductive material comprising a superconducting material; Surrounding (22) said filament with a mantle (2) made of a third conductive material to form an inner conductor; covering the inner conductor with an insulator (3) (23); and wrapping (24) the insulator with an outer conductor (4) made of a first conductive material.

13. In the step (21) of providing the filaments, only one filament (1) or several filaments (1a...1i) are provided, 13. The method of claim 12, wherein in the step (22) of surrounding the filament with a mantle, only the one filament or the plurality of filaments are surrounded by the mantle (2).

14. 12. Use of one or more coaxial cables (10, 11) according to any one of claims 1 to 11 for providing a transmission line for signals to quantum devices, in particular quantum computers, more particularly qubits, in a quantum processing unit QPU of said quantum computer.

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