Electrical assembly for cryogenic cooling system

Abstract

There is provided an electrical assembly (1) for a cryogenic cooling system, the electrical assembly comprising: a printed circuit board (PCB 2); and a plurality of thermal connectors (6, 7, 8, 9) arranged along the PCB 2. Each of the thermal connectors (6, 7, 8, 9) is separated from an adjacent thermal connector distal end by a respective folded portion (3, 4, 5) of the PCB 2.

Description

Technical Field

[0001] This invention relates to the field of cryogenic cooling systems and to electrical components for such systems. Background Technology

[0002] Cryogenic cooling systems are typically used to cool equipment to temperatures below 100 Kelvin. These systems typically include a vacuum chamber containing multiple spatially dispersed thermal stages (also known as “fins”), and a refrigerator arranged to cool one or more stages. Thermal radiation shielding is also usually provided to protect lower-temperature components from the effects of higher-temperature components in the system. An example of such a system is a dilution refrigerator. Such systems are often used for experimental purposes, where a sample (also referred to herein as a “measuring device”) is mounted on a cryogenic stage (typically a reference temperature stage) and communicatively coupled to a processing device located at a higher temperature location via electrical components. These electrical components are also referred to herein as “interconnectors.”

[0003] Interconnects typically comprise electrical connection components, such as cables, extending from a relatively high-temperature location within a system to a relatively low-temperature location. Interconnects are typically connected to one or more intermediate temperature levels to reduce the thermal load on the lower temperature level. Depending on application requirements, the components and construction of interconnects can vary, but may include coaxial cables, triaxial cables, twisted-pair cables, and microwave waveguides. Relevant considerations when designing interconnects include impedance matching and noise reduction, loss reduction, and minimizing heat conduction along the interconnect.

[0004] Quantum Information Processing (QIP) is an example of an experimental field where there is a growing need to expand the number of electrical connections offered by devices (which, in the context of QIP, might include arrays of qubits). Achieving this within the limited available space of cryogenic cooling systems designed using existing interconnects is becoming increasingly difficult. Summary of the Invention

[0005] A first aspect of the invention is an electrical component for a cryogenic cooling system, comprising: a printed circuit board (PCB); and a plurality of thermal connectors arranged along the PCB, wherein each thermal connector is disposed outside the PCB and includes a region of highly thermally conductive material; wherein each of the thermal connectors is separated from the distal end of an adjacent thermal connector by a corresponding fold portion of the PCB; wherein the electrical component extends along a first axis, the PCB extends substantially along the first axis, and the thermal connectors are separated from each other along the first axis, wherein each of the fold portions extends along two or more planes and includes two overlapping regions of the PCB having a normal to the first axis, the two overlapping regions being interconnected by a connection region of the PCB having a normal to the first axis, wherein the overlapping regions are connected to adjacent thermal connectors by corresponding upper and lower regions of the PCB having a normal to the first axis.

[0006] Therefore, the PCB is used to facilitate the electrical connections throughout the electrical assembly. This provides end users with a scalable and customizable solution that can accommodate higher density electrical connections than traditional interconnects. Thermal connectors can be arranged during use to connect to the corresponding thermal stages of a cryogenic cooling system to thermally ground the PCB and reduce heat conduction on the interconnects. The electrical assembly is configured such that the PCB folds between each pair of adjacent thermal connectors to form corresponding folded portions. This provides several advantages. For example, it increases the creepage distance (i.e., the length of the conductive path along the PCB surface between adjacent thermal connectors), which reduces the effective thermal conductivity of the entire electrical assembly. This ensures that the electrical assembly does not impose unwanted thermal loads on cryogenic components of any systems that may be connected to it during use.

[0007] Flexible PCBs are commonly used to form PCBs. This allows for folding to form folded portions of interconnects, and rigid portions of the PCB can be used to form thermal connectors. Each of these folded portions is preferably deformable to accommodate variations in the spacing between adjacent thermal connectors. This provides a certain mechanical tolerance for the electrical assembly (or “interconnect”) to maintain effective connection to cryogenic cooling system components during thermal cycling (strain is generated on the electrical assembly when the spacing between components at different temperatures in the system may change). The electrical assembly can extend substantially along a first axis. In use, cryogenic cooling systems typically apply a thermal gradient to the electrical assembly, parallel to the first axis. The folded portions of the PCB increase the elastic deformation of the electrical assembly, for example, to allow for variations in the spacing between adjacent thermal connectors along the first axis of ±2 mm. Each of these folded portions of the PCB extends along two or more planes, preferably orthogonal. This helps to reduce the effective thermal conductivity of the entire electrical assembly and increases the elastic deformation of the electrical assembly between adjacent thermal conductors.

[0008] As described above, the electrical components extend along a first axis, and the PCB extends substantially along the first axis. Thermal connectors are spaced apart from each other along the first axis. Each folded portion includes two overlapping regions of the PCB having a normal to the first axis, these two overlapping regions being interconnected by a connection region of the PCB having a normal orthogonal to the first axis. The overlapping regions are connected to adjacent thermal connectors by corresponding upper and lower regions of the PCB having normals orthogonal to the first axis (optionally, also orthogonal to the normal of the connection region). This arrangement increases creepage and elastic deformation of the PCB along the first axis. Furthermore, the conceptual size area of ​​a cutable and foldable PCB board is effectively utilized to form the PCB of the first aspect.

[0009] Electrical components are typically designed as inserts into cryogenic cooling systems. This allows the component to be installed as a single unit into or removed from the cryogenic cooling system. This enables convenient installation into existing cryogenic cooling systems and allows for adjustments to the component on a workbench, such as modifying parts based on experimental requirements.

[0010] The desired outcome is that electrical components will not generate heat leaks, which could prevent the system's low-temperature components from cooling to their intended operating reference temperature. Therefore, low thermal conductivity materials are preferred for forming any electrical transmission lines or "traces" along the PCB, separated from one or more layers of electrically insulating material, which also have low thermal conductivity. Low and limited thermal conductivity can be, for example, 1-50 W / (m²) at 100 K. Between 0.1 and 5 W / ( at 10K) Between 0.01 and 0.75 W / ( at 1K) Between 20K and 30K. Typically, at a temperature of 20K, the effective thermal conductivity of each of the folded portions is less than 50 W / m K. Examples of suitable materials for forming electrical connections in a PCB are copper-nickel alloys, such as constantan (comprising about 55% copper and 45% nickel) or manganin (comprising about 84% copper, 12% manganese, and 4% nickel). Therefore, the PCB preferably includes electrical transmission lines formed of a copper-nickel alloy, optionally also including manganese and / or nickel. Thus, the conductive material forms the wiring material and can be provided as a foil.

[0011] The electrical component has multiple regions of highly thermally conductive material, referred to as thermal connectors. High thermal conductivity can be, for example, at least 100 W / (m²) at or above 10 K. ), and at least 10 W / ( at 1K) An example of a suitable material for thermal connectors is copper. Multiple thermal connectors typically include a first thermal connector and a second thermal connector, wherein the first thermal connector is thermally coupled to a first end of the PCB and the second thermal connector is thermally coupled to a second end of the PCB, wherein the PCB is configured to transmit electrical signals between the first and second ends. Thermal connectors may take the form of a layer or block of highly thermally conductive material. Each thermal connector is disposed on the exterior of the PCB for mechanical connection to components of a cryogenic cooling system. For example, each of the aforementioned thermal connectors is preferably configured to connect to a corresponding fin or "thermal step" of the cryogenic cooling system. One or each thermal connector may be integrally formed within the PCB or may be a separate component applied to the PCB, such as an anchor or clamp. The electrical assembly preferably includes four of the aforementioned thermal connectors, each of the aforementioned thermal connectors for connection to a corresponding thermal step of the cryogenic cooling system.

[0012] Typically, multiple thermal connectors include a first thermal connector and a second thermal connector; the electrical assembly also includes: a first set of electrical components provided at the first thermal connector, and a second set of electrical components provided at the second thermal connector; wherein the first set of electrical components is electrically connected to the second set of electrical components via a PCB. In this scenario, the second thermal connector is typically located at the other end of the electrical assembly opposite the first thermal connector. The second set of electrical components may include one or more electrical connectors, which are preferably communicatively coupled to a measuring device, which may be located on the thermal level of an in-use cryogenic cooling system (typically a reference temperature level). Alternatively, the measuring device may be directly connected to the electrical assembly. For example, the second set of electrical components may include a measuring device capable of being physically connected to a PCB. This provides the advantage of reducing the number of electrical connections / connections to be formed, thereby reducing potential signal integrity losses.

[0013] The measuring device is preferably cooled to below 1K, preferably below 0.5K, more preferably below 50mK or 20mK during use by components of a cryogenic cooling system. The measuring device is preferably part of a quantum processing system, preferably a qubit array comprising one or more qubits. Electrical components are preferably configured to power the measuring device and can be communicatively coupled to perform read / write operations on the device.

[0014] Within a PCB stack, the PCB preferably includes a first conductive material layer, which is separated from a second conductive material layer by an electrically insulating layer. These conductive material layers can be used to form traces. For example, the first layer can form an RF transmission line array, and the second layer can form a backplane. Alternatively (e.g., in adjacent segments of the PCB), the first layer can form a first DC transmission line array, and the second layer can form a second DC transmission line layer. This layered arrangement typically continues uninterrupted throughout the entire PCB, across folds and thermal connectors. The backplane can be a shaded (or “mesh”) ground plane. This reduces the effective width of conduction along the backplane and between adjacent thermal connectors.

[0015] If DC lines are provided, they can be formed from a first conductive material layer and / or a second conductive material layer in a PCB stack. Interconnects preferably include a first DC line array disposed on a first layer of the PCB and a second DC line array disposed on a second layer of the PCB, the first and second layers overlapping. High-density electrical connections can then be provided. Optionally, the first array can provide an input channel for a measuring device, and the second array can provide a return channel. The RF line array and DC line array preferably electrically and communicatively couple the first set of electrical components to the second set of electrical components. Typically, the RF line array is disposed within a first segment of the PCB, and the first and second DC line arrays are disposed within a second segment of the PCB, the second segment preferably adjacent to the first segment. Depending on the thickness of the PCB, these two segments can correspond to different and non-overlapping widths of the PCB. This further facilitates efficient use of available space on the PCB, enabling the inclusion of high-density connections.

[0016] Other aspects of the invention will now be discussed. Any feature discussed in relation to one aspect can be equivalently applied to the remaining aspects and share similar advantages.

[0017] A second aspect of the invention is a cryogenic cooling system comprising: a vacuum chamber; a plurality of thermal steps arranged within the vacuum chamber; a cryogenic cooling device configured to apply thermal gradients on the plurality of thermal steps; and an electrical component according to the first aspect, wherein each of the thermal connectors is connected to a corresponding thermal step.

[0018] The second aspect shares similar advantages with the first aspect discussed above. The cryogenic cooling system of the second aspect can take many different forms. For example, it could be a "wet" system that relies on a cryogenic exchange gas or liquid refrigerant (typically helium or nitrogen contained in a Dewar flask) to provide most of the cooling power. Alternatively, it could be a "dry" or "cryogenic-free" system that relies on one or more mechanical refrigerators (also known as cryogenic coolers, such as pulse tube refrigerators, Stirling coolers for cooling systems, or Gifford McMahon coolers). The cryogenic cooling device preferably includes a pulse tube refrigerator. The cryogenic cooling device may include multiple refrigerators, some of which may be configured to achieve a reference temperature of less than 1 K. For example, the cryogenic cooling device preferably also includes a dilution refrigerator.

[0019] In use, the interface is typically arranged within a vacuum space formed by a vacuum chamber. Multiple thermal stages preferably include a reference temperature stage, which is configured to be cooled to the lowest temperature of the multiple thermal stages by a cryogenic cooling device. The reference temperature stage is thermally coupled to the measuring device, wherein the electrical components are communicatively coupled to the measuring device. Specifically, the measuring device is preferably communicatively coupled or electrically connected to the PCB of the electrical components. The measuring device may be arranged on the reference temperature stage, or, as previously described, on the electrical components themselves. In use, the reference temperature stage is preferably configured to be cooled to below 5K, preferably below 20mK, by a cryogenic cooling device.

[0020] This invention offers specific advantages in the field of QIP (Quantum In-Process) systems, where the demand for expanded electrical connections in cryogenic cooling systems is constantly increasing. Therefore, a third aspect of the invention is a quantum processing system comprising: a cryogenic cooling system according to the second aspect; and a qubit array including one or more qubits communicatively coupled to electrical components. Thus, the qubit array can form an example of a measurement device as described above. QIP systems typically include one or more electronic components configured to perform read / write operations on the qubit array. These components can be inside or outside a vacuum chamber and can include processing devices, such as computers.

[0021] A fourth aspect of the invention is an electrical assembly for a cryogenic cooling system, comprising: a PCB having a plurality of rigid portions arranged along a PCB and one or more flexible portions, each of the rigid portions comprising a material having high thermal conductivity, and each of the flexible portions being connected to an adjacent rigid portion of the PCB. The rigid portions may correspond to the thermal connectors discussed with reference to the first aspect. The flexible portions may be folded to form the folded portions described in the first aspect. Attached Figure Description

[0022] Embodiments of the invention will now be discussed with reference to the following figures, in which:

[0023] Figure 1 This is a first perspective view of an electrical component according to a first embodiment of the present invention;

[0024] Figure 2 This is a second perspective view of the electrical assembly of the first embodiment;

[0025] Figure 3 This is a schematic diagram of the electrical components of the first embodiment installed in a cryogenic cooling system;

[0026] Figure 4 It is the PCB board that forms the electrical components of the first embodiment;

[0027] Figure 5 yes Figure 4 An enlarged view of a portion of the PCB board shown;

[0028] Figure 6 This is a perspective view of the first surface of the PCB board according to the first embodiment; and

[0029] Figure 7 This is a perspective view of the second surface of the PCB board in the first embodiment. Detailed Implementation

[0030] The electrical component or "interconnector" 1 according to the first embodiment of the present invention is as follows: Figure 1 or Figure 3 As shown. Figure 1 A front perspective view of interconnect 1 is shown, while Figure 2 A rear perspective view of interconnect 1 is shown. The interconnect extends substantially along a first direction, as shown in the figure. Figure 1 The vertical axis Z is shown. Interconnect 1 is mainly composed of PCB 2, which extends substantially along a first direction between the first group of electrical components and the second group of electrical components. The first group of electrical components takes the form of a first connector assembly 17, which is arranged at a first end of interconnect 1. The second group of electrical components takes the form of a second connector assembly 19, which is arranged at a second end of interconnect 1. In use, interconnect 1 is installed in a cryogenic cooling system and connected via one or more cryogenic cooling devices 40, 41, 42 (…). Figure 3 A thermal gradient is applied to interconnect 1. The thermal gradient extends along a first direction, with its first end being the hot end of interconnect 1 and its second end being the cold end.

[0031] PCB 2 is connected to first board 10, second board 11, third board 12, and fourth board 13, which are separated from each other and spatially distributed along the Z-axis. Each of the aforementioned boards 10-13 constitutes part of a corresponding thermal stage 30-33 of the cryogenic cooling system and is cooled to a different reference temperature during use. Boards 10-13 are made of a highly thermally conductive material, typically copper. Board assemblies 10-13 may include a series of aligned holes forming sight ports 16 in the boards 10-13. The sight ports are compatible with the existing wiring of the system and form conduits for wiring. However, a unique advantage of interconnect 1 is that PCB 2 can replace this wiring requirement, so the sight ports can be selectively closed (e.g., Figure 1 The first plate 10 in the middle is shown to reduce any thermal radiation along the Z-axis.

[0032] PCB 2 is typically a “flexible PCB”, comprising flexible materials such as polyimide. It is particularly desirable that PCB 2 be suitable for transmitting electrical signals between the first connector assembly 17 and the second connector assembly 19 via one or more transmission lines. It is also desirable that PCB 2 does not impose undesirable thermal loads on any low-temperature components of the system. Therefore, the conductive materials used in PCB 2 exhibit good electrical conductivity and relatively poor thermal conductivity. Copper-nickel alloys, such as constantan, are particularly suitable for this purpose. Therefore, PCB 2 typically comprises one or more copper-nickel layers that form transmission lines and are electrically insulated by one or more polymer layers.

[0033] Components of thermal connectors 6, 7, 8, and 9 are connected to PCB 2 (see...). Figures 2-4Each of the thermal connectors forms a rigid, high thermal conductivity portion of the interconnect 1 for thermal coupling between the PCB 2 and components of the cryogenic cooling system (in this case, corresponding connecting boards 10-13). Thermal connectors 6-9 thermally ground the interconnect 1 to different thermal levels of the cryogenic cooling system. Therefore, in use, the connection portion of the interconnect 1 can be cooled by components of the cryogenic cooling system (such as a cryogenic cooling device). This reduces the thermal conductivity between the hot and cold ends of the interconnect 1. The thermal connectors 6-9 are spatially distributed on the PCB 2 along a first direction and separated from each other by corresponding folded portions 3, 4, 5 of the PCB 2. In the first embodiment, the thermal connectors 6-9 are integrally formed within portions of the PCB 2. For example, the different portions forming the thermal connectors on the PCB 2 may include one or more copper plating layers covering the transmission lines and separated by intermediate cover layers. Thus, the PCB stack can have rigid portions with high thermal conductivity due to the applied copper plating, separated by flexible folded portions 3-5 on the PCB 2 with low thermal conductivity. Standard flexible-rigid PCB manufacturing techniques, such as IPC2223, can be used, with thermal conductors 6-9 forming a stacked rigid portion separated by a flexible portion in the middle of PCB 2. However, as mentioned earlier, a low thermal conductivity material is used to form the transmission lines or "traces" instead of (typically) copper.

[0034] exist Figure 3 In this embodiment, interconnect 1 is mounted on a component of the dilution refrigerator. For clarity, the various components of the dilution refrigerator have been... Figure 3 The portion omitted includes a vacuum chamber, a first cooling stage, and a thermal radiation shield. Each of the first, second, third, and fourth plates 10-13 forms a movable portion of a corresponding thermal stage 30-33, also referred to in the art as a "fin". A highly thermally conductive connection is formed between each plate 10-13 and the corresponding thermal stage 30-33. Several such movable plates can be provided along the thermal stages, thus allowing several interconnects to be housed within a given cryogenic cooling system. (Reference) Figure 3 In operation, the first thermal stage 30 is cooled to a reference temperature of approximately 4 K by the second stage of the two-stage pulse tube refrigerator 40. The second thermal stage 31 is cooled to a reference temperature of approximately 0.5 K–1 K by the distillation apparatus 41 of the dilution refrigerator. The fourth thermal stage 33 is cooled to a reference temperature below 20 mK by the mixing chamber 42 of the dilution refrigerator, and in operation, the third thermal stage 32 typically reaches a reference temperature between the second and fourth thermal stages 31. Although not shown, in practice, it is envisioned that multiple interconnects can be tightly stacked in rows and connected to different thermal stages of the system. Depending on experimental requirements, the interconnects may have slightly different dimensions or electrical components.

[0035] Each thermal connector 6-9 can be directly connected to the corresponding plate 10-13 via a mechanical clamp or anchor. In the first embodiment, the interconnect 1 is connected via the corresponding edge piece 10'-13' ( Figure 1 The interconnect 1 is mechanically connected to each of plates 10-13. During the installation process and removal of edge pieces 10'-13', the interconnect 1 is arranged in the cryogenic cooling system such that the first thermal connector 6, the second thermal connector 7, the third thermal connector 8, and the fourth thermal connector 9 abut against the first plate 10, the second plate 11, the third plate 12, and the fourth plate 13, respectively. The first edge piece 10', the second edge piece 11', the third edge piece 12', and the fourth edge piece 13' are then connected to the first plate 10, the second plate 11, the third plate 12, and the fourth plate 13, respectively, thereby holding the interconnect 1 between the plate and the connected edge pieces. Thermal connectors 6-9 may include one or more folds that assist in forming this mechanical connection. Thus, the interconnect 1 forms an insert for the cryogenic cooling system, which is inserted into the cryogenic cooling system or removed as a single component (where plates 10-13 are typically connected or not connected to the interconnect 1). This facilitates the maintenance or adjustment of the interconnect 1 in a benchtop environment outside the cryogenic cooling system.

[0036] The folded portions 3, 4, and 5 of PCB 2 advantageously reduce the effective thermal conductivity between boards and across interconnect 1. This is achieved by increasing the "creepage" of PCB 2 (the length of PCB 2 between thermal connectors). Therefore, the lengths of folded portions 3, 4, and 5 are greater than the spacing between adjacent thermal steps in the first direction. Folded portions 3-5 also cause a certain amount of elastic deformation in interconnect 1 along the Z-axis. This provides relief for strain caused by thermal contraction and expansion due to manufacturing tolerances or changes in the spacing between adjacent boards. Therefore, folded portions 3-5 help reduce heat conduction to low-temperature components of the system and achieve a reliable mechanical and thermal connection between the system and interconnect 1.

[0037] To maintain signal fidelity, it is desirable that PCB 2 be formed from a single PCB structure without any joints between PCB components. To achieve this, PCB board 2' is cut from a planar PCB blank. PCB blanks typically have relatively limited short dimensions. A PCB blank may be approximately 60cm × 45cm in size and is cut in a meandering shape to form the planar PCB board 2', as shown below. Figure 4As shown. Then, the PCB board 2' is folded along multiple fold lines to form the PCB 2 of the interconnect 1. This can be achieved by clamping a portion of the planar PCB board 2' and bending the remaining board. The shape of the PCB board 2' and the location of the fold lines are chosen to efficiently utilize the available dimensions of the PCB blank (reducing waste) while allowing the interconnect 1 to be adapted to an existing cryogenic cooling system with a pre-defined board spacing. A specific advantage achieved through folding is that it increases the length of the PCB 2 beyond the PCB board 2' on the Z-axis. This allows the PCB 2 of the interconnect 1 to be connected to locations further than its maximum manufacturing area, enabling a single continuous PCB to extend from the top (highest temperature) step of the cryogenic cooling system all the way to the lowest temperature step.

[0038] PCB 2 extends substantially in a first direction between each thermal connector 6-9 in an elongated manner. A first fold portion 3 of PCB 2 connects the first thermal connector 6 to the second thermal connector 7. In this embodiment, the Z-axis spacing between the first board 10 and the second board 11 is greater than the spacing between any other adjacent boards. Therefore, PCB 2' is configured such that the first fold portion 3 is the longest of the fold portions 3-5 along the Z-axis. A second fold portion 4 of PCB 2 connects the second thermal connector 7 to the third thermal connector 8 (which is the shortest of the fold portions 3-5 due to the smaller spacing between adjacent second and third boards 11, 12). A third fold portion 5 of PCB 2 connects the third thermal connector 8 to the fourth thermal connector 9. Each of the fold portions 3-5 has a central fold region 18, which includes two overlapping portions of PCB 2 having a plane perpendicular to the Z-axis. These two overlapping portions are connected by a connecting portion of PCB 2 having a normal orthogonal to the Z-axis. Each central fold region 18 is connected to a corresponding adjacent thermal connector via upper and lower portions of PCB 2. In this embodiment, the upper and lower portions have planes perpendicular to the planes of the overlapping and connecting portions. For example... Figure 2 As shown, one or more additional folds are typically provided at the connection point between PCB 2 and each board 10-13.

[0039] like Figure 3 As shown, the measuring device 45 is connected to the fourth thermal stage 33 and is cooled by the mixing chamber 42 during use. In the context of a quantum information processing (QIP) system, the device 45 typically comprises a qubit array of one or more qubits. The device 45 is communicatively coupled to the interconnect 1 via an electrical connector 47 (such as a cable) that extends between the second connector assembly 19 and the device 45. The presence of any connection between different electrical components introduces a potential point of failure and may introduce signal loss. Therefore, in an alternative embodiment, the device 45 may be formed on the interconnect 1 and directly connected to the transmission line of the PCB 2 without any intermediate electrical connectors or cables 47.

[0040] Interconnector 1 communicatively couples device 45 to an electronic processing device (not shown) located at a higher temperature. This is typically a computer located outside a vacuum chamber of a cryogenic cooling system. In a first embodiment, it is envisioned that interconnector 1 terminates at a first thermal stage 30 (at the hot end) where a first connector assembly 17 is provided. Therefore, since the first connector assembly 17 is located inside the vacuum chamber, additional electrical connections (typically in the form of cables) are required to connect the first connector assembly 17 to the processing device outside the vacuum chamber. However, in an alternative embodiment, the first connector assembly can be located outside the vacuum chamber (e.g., within an hermetically sealed gasket), thereby eliminating the need for any intermediate cables extending inside the vacuum chamber.

[0041] Return to Figure 1 and Figure 2 In the illustrated embodiment, an electrical connector forming part of the first connector assembly 17 is disposed outside the first thermal connector 6, and an electrical connector forming part of the second connector assembly 19 is disposed outside the fourth thermal connector 9. These form branch portions of the transmission lines (traces) in the PCB 2. The electrical connections can be used to transmit power to and / or communicate with the device 45, such as performing read / write operations on the device 45.

[0042] Each of the first and second connector assemblies 17, 19 includes a coaxial RF (radio frequency) connector array for an RF transmission line extending through PCB 2 and a 25-channel miniature D-type connector array for a DC (direct current) transmission line also extending through PCB 2. The specific form of the electrical connectors provided externally to interconnect 1 can vary depending on the application. A direct DC connection can be used to apply DC voltage or low-frequency modes below 100MHz to the measuring device. An RF connection can be used for signal frequencies above 100MHz.

[0043] The PCB stack is configured to accommodate two conductive material layers (typically constantan) separated by an intermediate electrically insulating base layer (typically polymer) to form an RF transmission line and a DC transmission line. Thus, the RF and DC transmission lines are integrally formed within PCB 2 and extend uninterruptedly from the first connector assembly 17 through PCB 2 to the second connector assembly 19.

[0044] Figure 5 It shows passing through, such as Figure 2 The arrangement of RF and DC transmission lines in section "A" of PCB 2 is shown. On the first segment or "width" 56 of PCB 2, there is an array of RF lines 50 formed by a constantan layer. Figure 6 Conductive traces formed by the first constantan layer can also be seen in the image. Figure 6The first surface of PCB 2 region is depicted. RF lines 50 are arranged linearly along PCB 2 (in the first direction, as shown in part A). RF lines 50 can be included at high space densities, such as up to 5 lines per millimeter, and the higher the density, the more susceptible they are to crosstalk.

[0045] It may be required that the RF connection maintain a characteristic impedance, such as 50Ω. This is accomplished by routing a backplane with a certain width on the PCB, so that the impedance (i.e., the square root of the inductance divided by the capacitance) equals 50. Within the PCB stack-up structure, the RF line 50 overlays a mesh backplane 52, which is formed of a second constantan layer and electrically connected to ground potential to create a 50-ohm route. For illustrative purposes, Figure 5 Two layers of traces are shown, although in Figure 6 and Figure 7 Only one layer is shown. Figure 7 The second surface of region 2 of the PCB is depicted, which is related to... Figure 6 The surfaces shown are opposite. For example... Figure 7 As shown, the conductive material 52 in the second layer is arranged in a lattice comprising a grid of orthogonal traces and offset from the conductive material 50 in the first layer. Therefore, the RF lines 50 overlap the conductive traces of the backplane 52 at a 45-degree angle. This mesh arrangement ensures the backplane spans the width of the first segment 56, but reduces the effective width of the conductive material used for heat conduction along the backplane between adjacent thermal connectors. In contrast, if the backplane were provided as a solid layer of conductive material (uninterrupted across the width of the first segment 56), the effective width of the conductive material in the second layer could be approximately three times greater, which could increase the effective thermal conductivity on the folded portions of the PCB 2.

[0046] DC lines 54 and 55 are linearly arranged along PCB 2 (in the first direction, as shown in section A). DC lines 54 and 55 are arranged on a second segment or "width" 58 of PCB 2, which is adjacent to but does not overlap with the first segment 56. Unlike RF lines 50, DC lines do not require a backplane, so DC lines 54 and 55 are composed of a first constantan layer and a second constantan layer. In other words, the DC lines run on both sides of the central polymer base layer within the PCB stack. Figure 6 and Figure 7The reason is visible on both surfaces of PCB2 shown. The density of DC lines can be higher than that of RF lines, for example, up to 14 DC lines per millimeter (including DC wiring on both sides). The width of the DC lines can be customized based on the power and signal strength of the electrical signals transmitted based on the application. In this embodiment, the width of section A is approximately 30 cm, containing 30 RF lines across the first segment 56 and 100 DC lines across the second segment 58 (although schematically shown). This is a much higher electrical connection density than that achievable using interconnects formed using conventional cable assemblies.

[0047] Interconnect 1 can include active or passive electrical components. A particular advantage of Interconnect 1 is that if the user wants to include a new component, such as an active component that requires power, PCB 2 already provides the necessary connections for that component. In contrast, with conventional methods, new cables need to be routed through the interior of the cryogenic cooling system, back and forth between the new components. This is time-consuming, consumes valuable space, and requires impedance matching. PCB-based Interconnect 1 solves this problem by providing a framework or building block for any number of possible experimental setups by using different electrical components that can be directly mounted to PCB 2.

[0048] One or more electronic filters (not shown) may be arranged along interconnect 1, typically along a rigid portion of PCB 2 formed by one of thermal connectors 6, 7, 8, and 9. Rigid copper PCB splitters 6-9 allow electronics to be integrated at any temperature level without signal integrity loss introduced by the connectors. Typically, filters are added along DC transmission lines at intermediate levels (such as a second thermal connector 7 thermally coupled to the second board 11 and / or a third thermal connector 8 thermally coupled to the third board 12 during use). For example, resistors and capacitors may be used to form low-pass filters for DC signals. RF electronics (such as mixers, amplifiers, voltage or current sources) may also be integrated onto PCB 2. Users can select or adjust the exact arrangement of electronic components based on experimental needs. Existing design software can be used to plan the placement of electronic components.

[0049] Therefore, an improved interconnect is provided that allows for higher density electrical connections to measuring devices in cryogenic cooling systems. The use of a large flexible-rigid PCB allows wiring and electronics to be connected on the same medium, reducing the need for interfaces between them. The interconnect includes multiple thermal connectors and flexible portions of the PCB to reduce heat conduction on the PCB and facilitate cryogenic cooling for the measuring devices. During system thermal cycling, the folded portions also enable reliable thermal and mechanical connections between components of the cryogenic cooling system and the interconnect. The folds in the PCB also extend the interconnect distance beyond the maximum size of standard manufactured PCBs. Compared to wiring, the use of a PCB generally reduces the number of electrical connectors or connections that need to be formed, which can improve the fidelity of electrical signals transmitted along the interconnect. Furthermore, the use of a PCB makes the interconnect highly customizable, allowing new electrical components to be easily incorporated into the system without additional wiring. Other advantages are apparent and discussed here.

[0050] This invention offers advantages in numerous applications within the field of cryogenic physics, but provides specific advantages in the context of QIP. Here, the interconnect provides a key-transfer solution for all cryogenic components to support the operation of a quantum computer within a dilution refrigerator.

[0051] Further embodiments of the present invention are provided by the following numbered clauses.

[0052] Clause 1: An electrical component for a cryogenic cooling system, comprising: Printed circuit boards (PCBs); and Multiple thermal connectors arranged along the PCB; Each of the thermal connectors is separated from the distal end of the adjacent thermal connector by a corresponding folded portion of the PCB.

[0053] Clause 2: Electrical components according to Clause 1, wherein each of the said folded portions of the PCB is deformable to allow for variation in the spacing between adjacent thermal connectors.

[0054] Clause 3: Electrical components according to Clause 1 or Clause 2, wherein each of the said folded portions of the PCB extends along two or more planes, preferably orthogonal.

[0055] Clause 4: An electrical assembly according to any of the preceding clauses, wherein the electrical assembly extends on a first axis, the PCB extends substantially along the first axis, and the thermal connectors are spaced apart from each other along the first axis, wherein each of the said folded portions includes two overlapping regions of the PCB having a normal on the first axis, the two overlapping regions being interconnected by a connection region of the PCB having a normal orthogonal to the first axis.

[0056] Clause 5: Electrical components according to Clause 4, wherein the overlapping area is connected to the adjacent thermal connector via corresponding upper and lower areas of a PCB having a normal orthogonal to the first axis.

[0057] Clause 6: An electrical component pursuant to any of the preceding clauses, wherein the component forms an insert for a cryogenic cooling system.

[0058] Clause 7: Electrical components pursuant to any of the preceding clauses, wherein the PCB includes electrical transmission lines formed of a copper-nickel alloy.

[0059] Clause 8: An electrical assembly pursuant to any of the preceding clauses, wherein the plurality of thermal connectors includes a first thermal connector and a second thermal connector; the electrical assembly further includes: The first set of electrical components provided at the first thermal connector; and A second set of electrical components is provided at the second thermal connector; The first group of electrical components is electrically connected to the second group of electrical components via a PCB.

[0060] Clause 9: Electrical components pursuant to Clause 8, wherein the second group of electrical components includes measuring devices.

[0061] Clause 10: An electrical component pursuant to any of the preceding clauses, wherein the PCB includes an RF line array overlapping the mesh plane.

[0062] Clause 11: An electrical component according to any of the preceding clauses, wherein the PCB further includes a first DC line array disposed on a first layer of the PCB and a second DC line array disposed on a second layer of the PCB.

[0063] Clause 12: Electrical components pursuant to Clauses 10 and 11, wherein the RF line array is arranged within a first segment of the PCB, and wherein the first DC line array and the second DC line array are arranged within a second segment of the PCB, the second segment being adjacent to the first segment.

[0064] Clause 13: An electrical assembly pursuant to any of Clauses 1-9, wherein the PCB includes a first conductive material layer separated from a second conductive material layer by an electrically insulating layer; In the first segment of the PCB, the first layer forms the RF transmission line array, and the second layer forms the backplane; and In the second segment of the PCB, the first layer forms a first DC transmission line array, and the second layer forms a second DC transmission line array.

[0065] Clause 14: Electrical components pursuant to Clause 13, wherein the backplane is hashed.

[0066] Clause 15: A cryogenic cooling system comprising: Vacuum chamber; Multiple thermal stages arranged within the vacuum chamber; A cryogenic cooling device configured to apply thermal gradients across multiple thermal levels; and According to the aforementioned terms, electrical components, Each of the thermal connectors is connected to the corresponding thermal stage.

[0067] Clause 16: A cryogenic cooling system according to Clause 15, wherein a plurality of thermal stages includes a reference temperature stage, the reference temperature stage being configured to be cooled to the lowest temperature among the plurality of thermal stages by a cryogenic cooling device, the reference temperature stage being thermally coupled to a measuring device, wherein electrical components are electrically connected to the measuring device.

[0068] Clause 17: A quantum processing system comprising: Cryogenic cooling systems according to Clause 15 or 16; and A qubit array, comprising one or more qubits that are communicatively coupled to an electrical component.

Claims

1. An electrical component (1) for a cryogenic cooling system, comprising: Printed circuit board (PCB) (2); as well as Multiple thermal connectors (6, 7, 8, 9) are arranged along the PCB (2), wherein each thermal connector is arranged on the outside of the PCB and includes a region of high thermal conductivity material; Each of the thermal connectors (6, 7, 8, 9) is separated from the distal end of the adjacent thermal connector by a corresponding folded portion (3, 4, 5) of the PCB (2); The electrical components extend along a first axis, the PCB (2) extends substantially along the first axis, and the thermal connectors (6, 7, 8, 9) are spaced apart from each other along the first axis. Each of the folded portions extends along two or more planes and includes two overlapping regions on the PCB that have a normal to the first axis. The two overlapping regions are interconnected by a connection region of the PCB that has a normal to the first axis. The overlapping regions are connected to adjacent thermal connectors by corresponding upper and lower regions of the PCB that have a normal to the first axis.

2. The electrical component according to claim 1, wherein, Each of the folded portions (3, 4, 5) of the PCB (2) is deformable to allow for variations in the spacing between adjacent thermal connectors (6, 7, 8, 9).

3. The electrical component according to claim 1 or 2, wherein, Each thermal connector includes a layer or block of highly thermally conductive material.

4. The electrical component according to any of the preceding claims, wherein, The overlapping areas are interconnected by a connection portion of the PCB (2) having a normal perpendicular to the first axis, wherein the upper and lower portions have a plane perpendicular to the connection portion.

5. The electrical component according to any of the preceding claims, wherein, The component forms an insert for a cryogenic cooling system.

6. The electrical component according to any one of the preceding claims, wherein, A PCB consists of electrical transmission lines formed from a copper-nickel alloy.

7. The electrical component according to any one of the preceding claims, wherein, The plurality of thermal connectors includes a first thermal connector (6) and a second thermal connector (7); the electrical assembly further includes: The first set of electrical components (17) provided at the first thermal connector (6); and A second set of electrical components (19) is provided at the second thermal connector (7); The first group of electrical components is electrically connected to the second group of electrical components via the PCB (2).

8. The electrical component according to claim 7, wherein, The second group of electrical components includes a measuring device.

9. The electrical component according to any of the preceding claims, wherein, The PCB (2) includes an RF line array (50) that overlaps with the mesh plane (52).

10. The electrical component according to any of the preceding claims, wherein, The PCB also includes a first DC line array (54) arranged on the first layer of the PCB and a second DC line array (58) arranged on the second layer of the PCB.

11. The electrical assembly according to claims 9 and 10, wherein, The RF line array is arranged in the first segment (56) of the PCB (2), wherein the first DC line array (54) and the second DC line array are arranged in the second segment (58) of the PCB, the second segment being adjacent to the first segment (56).

12. The electrical component according to any one of claims 1-11, wherein, The PCB (2) includes a first conductive material layer, which is separated from the second conductive material layer by an electrical insulating layer.

13. The electrical component according to any one of claims 1-8, wherein, The PCB (2) includes a first conductive material layer, which is separated from the second conductive material layer by an electrical insulating layer; In the first segment (56) of the PCB (2), the first layer forms an RF transmission line array (50), and the second layer forms a backplane (52); and In the second segment (58) of the PCB (2), the first layer forms a first DC transmission line array (54), and the second layer forms a second DC transmission line layer.

14. The electrical component according to claim 13, wherein, The backplane (52) is hashed.

15. A cryogenic cooling system, comprising: Vacuum chamber; Multiple thermal stages (30, 31, 32, 33) are arranged in the vacuum chamber. Cryogenic cooling devices (40, 41, 42) configured to apply thermal gradients over the plurality of thermal stages (30, 31, 32, 33); and The electrical assembly (1) according to any of the preceding claims, wherein each of the thermal connectors (6, 7, 8, 9) is connected to the corresponding thermal steps (30, 31, 32, 33).

16. The cryogenic cooling system according to claim 15, wherein, The plurality of thermal stages includes a reference temperature stage (33), which is configured to be cooled to the lowest temperature among the plurality of thermal stages by the cryogenic cooling device, the reference temperature stage being thermally coupled to a measuring device (45), wherein the electrical component (1) is electrically connected to the measuring device.

17. A quantum processing system, comprising: The cryogenic cooling system according to claim 15 or 16; as well as A quantum bit array (45) includes one or more quantum bits that are communicatively coupled to the electrical component (1).

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