A cable connector assembly

Abstract

The disclosure describes electrical wiring in an assembly comprising a receptacle and a plug. The disclosed solution allows to electrically connect a substrate to signal cables with very low contact resistance and small footprint. Such connection enables more current to flow to the quantum chip improving thereby the operation of the quantum devices.

Description

[0001] A CABLE CONNECTOR ASSEMBLY

[0002] FIELD OF THE DISCLOSURE

[0003] This disclosure relates to cable connector assemblies and more particularly to connector assemblies at cryogenic temperatures. The present disclosure further concerns electrical wiring in assemblies comprising a receptacle and a plug.

[0004] BACKGROUND OF THE DISCLOSURE

[0005] A quantum computer is a computer that uses the properties of quantum mechanics to perform calculations and store data. There are different types of quantum computers. These include superconducting quantum computers, photonic quantum computers, neutral atom quantum computers, trapped ion quantum computers, and quantum dot quantum computers. The key component in a quantum computer is the quantum processing unit (QPU) chip (a.k.a. quantum chip) which is designed to manipulate and process information using qubits.

[0006] A superconducting quantum computer is a quantum computer that uses superconducting circuits to perform quantum computations. As superconductivity is a phenomenon that occurs at very low temperatures, superconducting quantum computers utilize sophisticated cryogenic systems to cool the qubits and associated components to extremely low temperatures.

[0007] Installing a quantum chip in a quantum computing system involves a series of precise and controlled steps. The process can vary depending on the specific quantum computing architecture and technology. For example, after a quantum chip is fabricated using semiconductor fabrication techniques, the chip is carefully extracted from the fabrication environment, then integrated into the quantum computer cryostat. The chip may be first attached and electrically connected, in a cleanroom, to a printed circuit board (PCB) of a sample holder which also houses electrical connectors. The sample holder may then be installed in the cryostat, and the electrical cables in the cryostat may be connected to the quantum chip via the connectors on the sample holder. As the number of physical qubits on one quantum processing chip has increased to tens or hundreds, the number of electrical input and output lines has increased as well. Effective routing of these lines requires high-density multi-conductor connectors on the PCB surface. However, conventional connectors made of normal metal exhibit a finite contact resistance, causing a part of each control signal to turn into heat. When the number of control signals is sufficiently high, the combined heating effect may significantly increase the local temperature of the quantum chip, thereby leading to performance degradation.

[0008] Assemblies for connecting coaxial cables to a circuit board so that the center conductors are inserted within a conductive hole forming part of the board structure are commonly used. These assemblies may include a spring contact member which serves as part of the grounding means to effectively ground the shield members of the coaxial cables to the board's ground. However, such connection configuration is unsuitable for applications at cryogenic temperatures as it may induce high contact resistance which causes Joule heating and ultimately high temperature of the quantum chip. This leads to degraded performance for the quantum devices on the quantum chip.

[0009] BRIEF DESCRIPTION OF THE DISCLOSURE

[0010] An object of the present disclosure is to provide a solution to the problem described above.

[0011] The disclosed solution allows to electrically connect conductor traces on a substrate to signal cables with very low contact resistance and small footprint. Examples provided in this disclosure describe ways to implement the solution. The improvement is achieved by features of a receptacle, a plug for co-operation with the receptacle, and an assembly comprising the receptacle and the plug.

[0012] The object of the disclosure is achieved by arrangements which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

[0013] The disclosure is based on the idea of using deformable contact metal structures to electrically connect the signal cables to conductor traces on the substrate. Such connection induces low contact resistance enabling more current to flow to the quantum chip improving thereby the operation of the quantum devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the following, the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

[0015] Figure 1 a shows a simplified illustration of a receptacle comprising a cable support block and a set of signal cables;

[0016] Figure 1 b illustrates an example of the cross-section of a signal cable located within an aperture of the cable support block in accordance with one embodiment of the invention;

[0017] Figures 2a-2c illustrate examples of the cross-section of signal cables located within apertures of the cable support block in accordance with other embodiments of the invention;

[0018] Figure 3a illustrates an example of a top view of a plug comprising a first deformable metal structure;

[0019] Figure 3b shows an enlarged section of the plug illustrated in figure 3a;

[0020] Figure 3c shows a simplified illustration of the cross-section of a portion of the plug in figure 3a;

[0021] Figure 4a illustrates an example of a top view of a plug comprising a second deformable metal structure in accordance with one embodiment of the invention;

[0022] Figure 4b shows an enlarged section of the plug illustrated in figure 4a;

[0023] Figure 5a illustrates another example of a top view of a plug comprising a second deformable metal structure in accordance with another embodiment of the invention;

[0024] Figure 5b shows an enlarged section of the plug illustrated in figure 5a;

[0025] Figures 6a illustrate an example of a top view of a plug comprising a setting for receiving a quantum chip;

[0026] Figures 6b illustrates an example of a quantum chip attached to the plug via the setting for receiving a quantum chip;

[0027] Figure 7 illustrates a simplified example of the cross section of a plug comprising substrate vias;

[0028] Figures 8a illustrates an assembly before the receptacle and the plug are connected;

[0029] Figures 8b illustrates the assembly shown in figure 8a after the receptacle and the plug are connected; Figures 9 illustrates the cross section of an assembly portion showing details of the signal cable as being connected to the substrate;

[0030] DETAILED DESCRIPTION OF THE DISCLOSURE

[0031] The disclosure describes a receptacle for an electrical interface at cryogenic temperatures. The receptacle comprises a cable support block. The cable support block has a top surface and a bottom surface, and the top surface of the cable support block defines a horizontal xy-plane and a vertical z-direction which is perpendicular to the xy-plane. The cable support block comprises at least one aperture, and the at least one aperture extends along the z-direction from the top surface of the cable support block to the bottom surface of the cable support block. The receptacle further comprises a set of cables and the set of cables comprises at least one signal cable. The receptacle further comprises a first set of means for mechanical connection. The at least one signal cable comprises a first conductor and the at least one signal cable is positioned within the at least one aperture of the cable support block so that the first conductor extends through the whole depth of the at least one aperture.

[0032] The receptacle may further comprise at least one cast, wherein the at least one cast is located within the at least one aperture so that the at least one signal cable is fixed within the at least one aperture by the at least one cast.

[0033] Any direction or plane which is parallel to the xy-plane defined by the cable support block can be called horizontal. The direction which is perpendicular to the xy-plane can be called vertical direction. Expressions such as “top”, “bottom”, “above”, “below”, “up” and “down” refer in this disclosure to differences in the vertical z-coordinate.

[0034] In an implementation form, the receptacle may comprise a plurality of signal cables and the cable support block may comprise a plurality of apertures. Figure 1a shows a simplified illustration of a receptacle 100 comprising a cable support block 101 and a set of signal cables comprising a plurality of signal cables 102. Note that figure 1a (and other figures in this disclosure) shows the cables only partly, i.e., the signal cables are longer than what is shown and were cut in the figure for illustrative and clarity purposes. The cable support block 101 may be made of an electrically conductive material including, but not limited to, oxygen-free copper, aluminium, or titanium. This option may apply to any embodiment in this disclosure. Alternatively, the cable support block 101 may be made of an insulating material including, but not limited to, ceramics and polymers. The receptacle 100 further comprises a first set of means for mechanical connection 103. The cable support block 101 comprises a plurality of apertures which extend along the z-direction from the top surface of the cable support block to the bottom surface of the cable support block. At least one signal cable 102 in the set of cables comprises a first conductor. Each signal cable is positioned within a respective aperture of the cable support block so that the first conductor extends through the whole depth of the aperture. In this example, the receptacle 100 further comprises a plurality of casts 104. Each cast 104 is located within an aperture so that each signal cable 102 is fixed within an aperture by one cast 104.

[0035] The signal cables 102 together with the apertures may be substantially evenly distributed within the cable support block 101. They may be arranged in a 2D lattice to achieve maximal cable density. For example, they may be arranged in rows in the xy-plane so that they form a substantially rectangular or hexagonal lattice in the xy-plane, or they may be arranged in a substantially circular shape in the xy-plane.

[0036] Figure 1 b illustrates an example of the cross-section of a signal cable 102 located within an aperture 107 of the cable support block 101. The signal cable 102 comprises a first conductor 105 and an insulating layer 106 surrounding the first conductor 105. The first conductor 105 extends in the z-direction through the whole depth of the aperture 107 and its end is essentially aligned with the bottom surface of the cable support block 101. The insulating layer 106 may cover only a portion of the first conductor 105. In other words, the insulating layer 106 may terminate at the top of the aperture 107 or extend through a portion of the aperture depth. These options may apply to any embodiment in this disclosure. In this example, the insulating layer 106 terminates at the top of the aperture 107. The first conductor 105 may comprise a superconducting material such as indium, tin, lead, aluminum, niobium, niobium-titanium compound, or niobium-titanium nitride. These options may apply to any embodiment in this disclosure. The first conductor may be fully superconducting, or it may comprise a coating of superconductive material. The signal cable 102 may be fixed within the aperture 107 of the cable support block 101 by a cast 104 so that the cast 104 surrounds the portion of first conductor 105 which is positioned in the aperture 107. The cast 104 may comprise an electrically insulating resin such as epoxy resin, silicone resin, or polyurethane resin. These options may apply to any embodiment in this disclosure. In the assembly process, the resin is cured to form a solid cast. Depending on the resin, curing may be done using additives, such as a hardener, or without additives.

[0037] The at least one signal cable may further comprise a second conductor, wherein the second conductor terminates in the cable support block. The second conductor may comprise a superconducting material such as indium, tin, lead, aluminum, niobium, niobium-titanium compound, or niobium-titanium nitride. These options may apply to any embodiment in this disclosure. The second conductor may be fully superconducting, or it may comprise a coating of superconductive material. The second conductor may be soldered to the substrate. This option may apply to any embodiment in this disclosure.

[0038] In an implementation form, the at least one signal cable may for example be a two-core cable. Alternatively, the at least one signal cable may be a coaxial cable comprising a center conductor and a shield, wherein the first conductor is the center conductor and the second conductor is the shield. The coaxial cable may be a semi-rigid coaxial cable.

[0039] Figure 2a illustrates an example of the cross-section of a signal cable 202 located within an aperture 207 of the cable support block 201. The signal cable 202 comprises a first conductor 205 and a second conductor 208. The first conductor 205 extends in the z- direction through the whole depth of the aperture 207 and its end is essentially aligned with the bottom surface of the cable support block 201. The second conductor 208 may terminate in the cable support block 201. The signal cable 202 further comprises a first insulating layer 206 surrounding the first conductor 205 and a second insulating layer 209 surrounding the second conductor 208. The first insulating layer 206 and the second insulating layer 209 may terminate at the top of the aperture 207 or extend through a portion of the aperture depth. In this example, the first insulating layer 206 and the second insulating layer 209 terminate at the top of the aperture 207. The signal cable 202 is fixed within the aperture 207 of the cable support block 201 by a cast 204 so that the cast surrounds the portion of first conductor 205 which is positioned in the aperture 207. The signal cable 202 may for example be a two-core cable.

[0040] Figure 2b illustrates another example of the cross-section of a signal cable 212 located within an aperture 217 of the cable support block 21 1. In this example, the signal cable 212 is a coaxial cable comprising a center conductor and a shield. The first conductor 215 is the center conductor, and the second conductor 218 is the shield. The signal cable 212 further comprises an insulating layer 216 surrounding the center conductor. The first conductor 215 extends in the z-direction through the whole depth of the aperture 217 and its end is essentially aligned with the bottom surface of the cable support block 211 . The shield terminates in the cable support block 211 so that it is in contact with the inner surface of the aperture 217. The shield 218 may be electrically coupled to the cable support block 211. In this example, the signal cable 212 is fixed within the aperture 217 of the cable support block 211 by a cast 214. The cast 214 may comprise an electrically insulating resin.

[0041] Alternatively, the cast may comprise solder. Figure 2c illustrates another example of the cross-section of a signal cable 222 located within an aperture 227 of the cable support block 221. In this example, the signal cable 222 is a coaxial cable comprising a center conductor and a shield, wherein the first conductor 225 is the center conductor and the second conductor 228 is the shield. The signal cable 222 is fixed within the aperture 227 of the cable support block 221 by a cast 2210. The cast 2210 may be formed by metal solder which fixes the shield conductor to the inner walls of the aperture 227. In this example, the second conductor 228 is galvanically connected to the cable support block 221 via the conductive solder cast 2210. Reference number 226 in figure 2c corresponds to reference numbers 216 in figure 2b.

[0042] The disclosure further describes a plug for co-operation with the receptacle. The plug comprises a substrate, wherein the substrate has a top surface and a bottom surface. The substrate comprises at least one electrical connection.

[0043] The plug further comprises a second set of means for mechanical connection with the receptacle. The top surface of the substrate comprises at least one contact area. The plug further comprises a deformable contact metal structure. The deformable contact metal structure is located in the at least one contact area, and the deformable contact metal structure extends upwards from the top surface of the substrate. The deformable contact metal structure is electrically coupled to the at least one electrical connection of the substrate.

[0044] The at least one electrical connection of the substrate may comprise any conductive pathway on top or bottom surface of the substrate or sandwiched between substrate layers in an intermediate wiring layer. Alternatively or additionally, the at least one electrical connection may comprise a conductive pathway extending in z-direction at least partially through the substrate thickness (i.e. a substrate via). The at least one electrical connection may also comprise bonding pads, i.e. conductor areas on the top or bottom surface of the substrate, intended for attaching bonding wires that lead to the quantum chip.

[0045] The plug may co-operate with the receptacle. Co-operation refers to a situation where the plug may be connected to the receptacle either permanently or releasably.

[0046] The substrate may be a printed circuit board (PCB) such as FR-4 PCB, alumina PCB, PTFE-based laminate PCB or other PCBs such as Rogers® 4350B™ PCB. Alternatively, the substrate may be a co-fired ceramic substrate. These options may apply to any embodiment in this disclosure.

[0047] The deformable contact metal structure may be substantially spherical. The deformable contact metal structure may comprise a superconducting material. The superconducting material may comprise indium, and / or any other superconducting soft metal such as tin, lead, indium-copper-silver alloy, other soft superconducting alloys, or indium solders. The deformable contact metal structure may be formed by a variety of deposition methods such as sputtering, chemical vapor deposition, electron beam physical vapor evaporation, laser metal deposition, solder mask stencils, gaskets, electroplating or electroless plating. These options may apply to any embodiment in this disclosure.

[0048] In an implementation form, the plug may comprise a plurality of deformable contact metal structures. Figure 3a illustrates an example of a top view of a plug 3011 comprising a substrate 3012, a plurality of deformable contact metal structures 3014, and a second set of means for mechanical connection 3013 with the receptacle. The deformable contact metal structures 3014 extend upwards from the top surface of the substrate 3012. The deformable contact metal structures may be substantially evenly distributed within the top surface of the substrate. They may be arranged in the same shape in the xy-plane as the signal cables and the apertures in the cable support block. This option may apply to any embodiment in this disclosure. In this example, the deformable contact metal structures 3014 are symmetrically arranged within the top surface of the substrate 3012 so that they form a square-like shape.

[0049] Figure 3b shows an enlargement of the highlighted portion (dash lines) of the plug is figure 3a. In this example, the deformable contact metal structures 3014 have a spherical shape. Alternatively, the deformable contact metal structures may have a cylindrical bump, spheroid bump, pillar bump, or cubic-like shape. Alternatively, the deformable contact metal structures may comprise multiple small spheroids or metal powder suspended in paste. These options may apply to any embodiment in this disclosure.

[0050] Figure 3c shows a simplified illustration of the cross-section of a portion of the plug shown in figure 3a. In this example, the plug 3011 comprises two electrical connections 3015 in the substrate 3012. The substrate 3012 may have a multi-layer structure comprising several intermediate wiring layers 3016 which are electrically coupled to the electrical connections 3015. At least one deformable contact metal structure 3014 is electrically coupled to one electrical connection 3015 in the substrate 3012. In this example, the two electrical connections 3015 are substrate vias. Although here the substrate vias extend through all the layers of the substrate, it is possible to have substrate vias that extend through only a part of the layers (i.e., “blind vias”).

[0051] The top surface of the substrate may further comprise at least one grounding area, wherein the at least one grounding area is adjacent to the at least one contact area. The plug may further comprise a deformable grounding metal structure, wherein the deformable grounding metal structure is located in the at least one grounding area. The deformable grounding metal structure extends upwards from the top surface of the substrate. The deformable grounding metal structure may be at ground potential. The at least one grounding area may surround the at least one contact area.

[0052] In a possible implementation form, the deformable grounding metal structure may be a single point-like contact for the common ground located on the top surface of the substate. Alternatively, the deformable grounding metal structure may be multiple point-like contacts distributed across the unoccupied area of the top surface of the substrate. In another implementation form, the deformable grounding metal structure may be a continuous ring surrounding the contact area.

[0053] Figure 4a illustrates an example of a top view of a plug 4011 comprising a substrate 4012, a plurality of deformable contact metal structures 4014, and a second set of means for mechanical connection 4013 with the receptacle. The deformable contact metal structures 4014 extend upwards from the top surface of the substrate 4012. In this example, the deformable contact metal structures 4014 are symmetrically arranged within the top surface of the substrate 4012 so that they form a square-like shape. The plug further comprises a plurality of deformable grounding metal structures 4017. In this example, each deformable grounding metal structure 4017 has a continuous ring shape and surrounds a deformable contact metal structure 4014. The deformable grounding metal structures 4017 extend upwards from the top surface of the substrate 4012. The deformable grounding metal structures 4017 may be at ground potential. The ground potential is the electrical potential that is used as a common reference potential in the connector assembly (i.e. signal ground), and the ground potential may be essentially at earth ground potential or alternatively differ from it (i.e. floating ground). The deformable grounding metal structures may comprise a superconducting material. The superconducting material may comprise indium, and / or any other superconducting or normally conducting soft metal such as copper, tin, lead, indium-copper-silver alloy, other soft superconducting alloys, or indium solders. The deformable grounding metal structure may be formed by a variety of deposition methods such as sputtering, chemical vapor deposition, electron beam physical vapor evaporation, laser metal deposition, solder mask stencils, gaskets, electroplating or electroless plating. These options may apply to any embodiment in this disclosure.

[0054] Figure 4b shows an enlargement of the highlighted portion (dash lines) of the plug in figure 4a. Each deformable contact metal structures 4014 is surrounded by a deformable grounding metal structure 4017. In this example, the deformable contact metal structures 4014 have a spherical shape, whereas the deformable grounding metal structures 4017 have a continuous ring shape.

[0055] In a further implementation form, the deformable grounding metal structure may comprise multiple bumps, and the multiple bumps surround the contact area. Figure 5a illustrates an example of a top view of a plug 5011 comprising a substrate 5012, a plurality of deformable contact metal structures 5014, and a second set of means for mechanical connection 5013 with the receptacle. The deformable contact metal structures 5014 extend upwards from the top surface of the substrate 5012. In this example, the deformable contact metal structures 5014 are symmetrically arranged within the top surface of the substrate 5012 so that they form a square-like shape. The plug further comprises a plurality of deformable grounding metal structures 5017. In this example, each deformable grounding metal structure 5017 comprises multiple bumps which surround a deformable contact metal structure 5014. The deformable grounding metal structures 5017 extend upwards from the top surface of the substrate 5012.

[0056] Figure 5b shows an enlargement of the highlighted portion (dash lines) of the plug is figure 5a. Each deformable contact metal structures 5014 is surrounded by a deformable grounding metal structure 5017. In this example, the deformable contact metal structures 5014 have a spherical shape. Each deformable grounding metal structure 5017 comprises multiple bumps which surround a deformable contact metal structure 5014.

[0057] The plug may further comprise a setting for receiving a quantum chip. The setting for receiving a quantum chip may be attached to the substrate. Figure 6a illustrates an example of a top view of a plug 6011 comprising a setting 6018 for receiving a quantum chip. In this example, the setting 6018 for receiving a quantum chip is an opening in the substrate 6012, exposing the bottom surface of a support structure (not shown in this figure) onto which a quantum chip may be attached. Alternatively, the setting for receiving the quantum chip may be a partially milled recess in the substrate extending only through a portion of the substrate thickness. As another alternative, the setting for receiving the quantum chip may be an area on the top surface of the substrate, dedicated for receiving a quantum chip. Reference numbers 6013, 6014 and 6017 in figure 6a correspond to reference numbers 4013, 4014 and 4017, respectively, in figure 4a.

[0058] The plug may further comprise a quantum chip, wherein the quantum chip is attached to the setting for receiving a quantum chip, and wherein the quantum chip is electrically coupled to the at least one electrical connection. Figures 6b illustrates an example of a quantum chip 6119 attached to the plug 6011 via the setting 6018 for receiving a quantum chip. The electrical signal may be routed via a circuit trace on the top surface of the substrate from the deformable contact metal structure to quantum chip. In this example, the quantum chip is electrically connected to the circuit trace using bonding wires. Alternatively, any other method known in the field for electrical connection between a semiconductor chip and a printed circuit board may be used, such as flip-chip. Reference numbers 6012, 6013, 6014 and 6017 in figure 6b correspond to reference numbers 4012, 4013, 4014 and 4017, respectively, in figure 4a.

[0059] The quantum chip may be a quantum processing unit (QPU) chip that houses physical qubits (such as transmon qubits, flux qubits, fluxonium qubits, charge qubits, spin qubits, or any other qubit type that may be implemented on a semiconductor chip), and other circuit elements (such as readout resonators, flux bias lines, qubit drive lines, coupling buses, tunable couplers, and / or any other auxiliary circuit elements). As an alternative to a QPU chip, the quantum chip may be a chip that houses other types of quantum circuitry, such as quantum sensors, various test structures, near-quantum-limited amplifiers (such as traveling wave parametric amplifiers, TWPAs), or any other circuitry that utilizes quantum mechanical phenomena. The quantum chip may comprise a die (such as silicon or sapphire), onto which circuit structures are patterned using e.g. optical lithography, electron beam lithography or ion milling. The circuit structures on the quantum chip may comprise e.g. Josephson junctions, coplanar waveguides, capacitors, inductors, ground planes, or bonding pads. The quantum chip may comprise a single die or several dies that are bonded together (e.g. using flip-chip bonding).

[0060] The substrate may further comprise at least one substrate via, wherein the at least one substrate via is located in the at least one contact area. The at least one substrate via may extend in the z-direction from the top surface of the substrate through at least a portion of the thickness of the substrate. The deformable contact metal structure may be electrically coupled to the at least one electrical connection through the at least one substrate via. The at least one substrate via may be a hole through one or more layers of the substrate, wherein its inner surface is plated with a conductive material. Alternatively, the hole may be at least partially filled with a conductive material. The substrate vias enable routing of electrical signals in one or more intermediate patterned metallized layers sandwiched between substrate layers. Figure 7 illustrates a simplified example of the cross section of a plug comprising substrate vias. The plug 7011 comprises a substrate 7012, and the substrate 7012 comprises a plurality of substrate vias 7020. The substrate vias 7020 may be symmetrically arranged within the substrate 7012. The plug 7011 further comprises a plurality of deformable contact metal structures 7014. Each deformable contact metal structures 7014 may be deposited on top of a substrate via 7020. Alternatively, the deformable contact metal structures 7014 may be deposited in the vicinity of the substrate vias 7020 as shown in this figure. If the deformable contact metal structure 7014 is deposited in the vicinity of the substrate via 7020, an electrical connection between the deformable contact metal structure 7014 and the substrate via 7020 is established using a conductor trace (not shown in this figure) on the top surface of the substrate 7012.

[0061] The disclosure further describes an assembly comprising a receptacle and a plug. The receptacle is mechanically connected to the plug via the first set and the second set of means for mechanical connection so that the first conductor in the at least one signal cable is aligned with the deformable contact metal structure and connected to the deformable contact metal structure. The deformable contact metal structure is deformed when the plug and receptacle are connected to each other.

[0062] The receptacle in the assembly may be any receptacle described in this disclosure. The plug in the assembly may be any plug described in this disclosure.

[0063] Figures 8a illustrates the assembly before the receptacle 800 and the plug 8011 are connected. The plug 8011 comprises a substrate 8012 attached to a support structure 8023 using fastening means, such as screws 8024 in this example. The receptacle 800 is placed on top of the plug 8011 so that the substrate is parallel to the xy-plane and each signal cable 802 is vertically aligned with a deformable contact metal structure 8014, i.e. their x- and y-coordinates are essentially equal. Means for alignment 8022, such as bolts or pins, may be used to ensure that the end of each first conductor in an aperture of the cable support block 801 meets a deformable contact metal structure 8014. The receptacle 800 and the plug 8011 are after that connected via the first set of means for mechanical connection 803 and the second set of means for mechanical connection 8013, so that the deformable contact metal structure 8014 is pressed and deformed by the first conductor. In this example, the signal cables are coaxial cables comprising a center conductor and a shield. When the receptacle 800 and the plug 8011 are connected, each center conductor is pressed against a deformable contact metal structure 8014 so that the center conductor is electrically coupled to an electrical connection in the substrate 8012 via the deformable contact metal structure 8014, and the deformable grounding metal structures 8017 are pressed against the bottom surface of the cable support block 801. The ground plane of the substrate is electrically connected to the shield in each coaxial cable via the cable support block 801 and a deformable grounding metal structure 8017. Such connection induces low contact resistance enabling more current to flow to the quantum chip improving thereby the operation of the quantum devices. In this example, the plug 8011 and the receptacle 800 are connected together using screws 8021 . Alternatively, they may be connected by other means, including, but not limited to, bolts and nuts, rivets, or clamps.

[0064] Figures 8b illustrates the assembly 8125 after the receptacle 800 and the plug 8011 are connected. The assembly 8125 may be installed directly in a cryogenic system such as a quantum computer cryostat. A quantum computing system may comprise one or more assemblies.

[0065] In any embodiment presented in this disclosure, the cryogenic system may be a 3-He / 4- He dilution refrigerator, and the assembly 8125 may be thermally coupled to the mixing chamber stage of the 3-He / 4-He dilution refrigerator. Thermal coupling between the assembly 8125 and the mixing chamber stage of the refrigerator may be achieved by a mechanical contact, possibly with additional support structures made of a thermally conductive material, such as copper, in between. Alternatively, the assembly 8125 may be coupled to any other stage of the 3-He / 4-He dilution refrigerator, such as still stage, an intermediate stage between the mixing chamber stage and the still stage, or any stage of a pulse tube cooler.

[0066] Instead of a 3-He / 4-He dilution refrigerator, the cryogenic system may alternatively comprise any other refrigerator type, such as a 3-He refrigerator, adiabatic demagnetization refrigerator, Pomeranchuk cooling, Cifford-McMahon cryocooler, Joule- Thomson cooler, Stirling cryocooler, liquid helium, or liquid nitrogen. The assembly 8125 may be thermally coupled to any temperature stage of such refrigerators, e.g. to the lowest temperature stage or to some intermediate temperature stage.

[0067] Figures 9 illustrates the cross section of an assembly portion showing details of the signal cable as being connected to the substrate. In this example, the signal cable 902 is a coaxial cable wherein the first conductor 905 is the center conductor and the second conductor 908 is the shield. The center conductor 905 terminates at the bottom surface of the cable support block 901 , and the shield 908 terminates in the cable support block 901 . The signal cable 902 further comprises an insulating layer 906. The signal cable 902 is fixed within an aperture of the cable support block 901 by a cast 904 which surrounds the center conductor 905. In this example, the substrate 9012 comprises a substrate via 9020. A deformable contact metal structure 9014 is located on the substrate via 9020. The center conductor 905 is in contact with the deformable contact metal structure 9014 so that it is electrically coupled to the electrical connection 9016 in the substrate 9012. The shield 908 is grounded via the cable support block 901 and the deformable grounding metal structure 9017.

Claims

CLAIMS1 . A receptacle for an electrical interface at cryogenic temperatures comprising:- a cable support block, wherein the cable support block has a top surface and a bottom surface, and the top surface of the cable support block defines a horizontal xy-plane and a vertical z-direction which is perpendicular to the xy- plane, and wherein the cable support block comprises at least one aperture, and the at least one aperture extends along the z-direction from the top surface of the cable support block to the bottom surface of the cable support block,- a set of cables, wherein the set of cables comprises at least one signal cable,- a first set of means for mechanical connection, characterized in that the at least one signal cable comprises a first conductor, and wherein the at least one signal cable is positioned within the at least one aperture of the cable support block so that the first conductor extends through the whole depth of the at least one aperture.

2. A receptacle according to any of claim 1 , wherein the at least one signal cable further comprises a second conductor, wherein the second conductor terminates in the cable support block.

3. A receptacle according to claim 2, wherein the at least one signal cable is a coaxial cable comprising a center conductor and a shield, and wherein the first conductor is the center conductor and the second conductor is the shield.

4. A receptacle according to claims 1-3, wherein the receptacle further comprises at least one cast, wherein the at least one cast is located within the at least one aperture so that the at least one signal cable is fixed within the at least one aperture by the at least one cast.

5. A receptacle according to claim 4, wherein the at least one cast comprises an electrically insulating resin.

6. A receptacle according to claim 4, wherein the at least one cast comprises solder.

7. A receptacle according to any of claims 1-6, wherein the first conductor comprises a superconducting material.

8. A receptacle according to any of claims 2-7, wherein the second conductor comprises a superconducting material.

9. A plug for co-operation with the receptacle in claim 1 , wherein the plug comprises: a substrate, wherein the substrate has a top surface and a bottom surface, and wherein the substrate comprises at least one electrical connection, a second set of means for mechanical connection with the receptacle in claim 1 , characterized in that the top surface of the substrate comprises at least one contact area, and wherein the plug further comprises a deformable contact metal structure, wherein the deformable contact metal structure is located in the at least one contact area, and the deformable contact metal structure extends upwards from the top surface of the substrate, and wherein the deformable contact metal structure is electrically coupled to the at least one electrical connection of the substrate.

10. A plug according to claim 9, wherein the deformable contact metal structure comprises a superconducting material.

11. A plug according to claim 10, wherein the superconducting material comprises indium.

12. A plug according to claims 9-11 , wherein the deformable contact metal structure is substantially spherical.

13. A plug according to claims 9-12, wherein the top surface of the substrate further comprises at least one grounding area, wherein the at least one grounding area is adjacent to the at least one contact area, and wherein the plug further comprises a deformable grounding metal structure and the deformable grounding metal structure is located in the at least one grounding area, andwherein the deformable grounding metal structure extends upwards from the top surface of the substrate and the deformable grounding metal structure is at ground potential.

14. A plug according to claim 13, wherein the at least one grounding area surrounds the at least one contact area.

15. A plug according to claims 13-14, wherein the deformable grounding metal structure is a continuous ring surrounding the contact area.

16. A plug according to claims 13-14, wherein the deformable grounding metal structure comprises multiple bumps, and the multiple bumps surround the contact area.

17. A plug according to any of claims 9-16, wherein the plug further comprises a setting for receiving a quantum chip, and wherein the setting for receiving a quantum chip is attached to the substrate.

18. A plug according to claim 17, wherein the plug further comprises a quantum chip, wherein the quantum chip is attached to the setting for receiving a quantum chip, and wherein the quantum chip is electrically coupled to the at least one electrical connection.

19. A plug according to any of claims 9-18, wherein the substrate further comprises at least one substrate via, wherein the at least one substrate via is located in the at least one contact area, and wherein at least one substrate via extends in the z-direction from the top surface of the substrate through at least a portion of the thickness of the substrate, and wherein the deformable contact metal structure is electrically coupled to the at least one electrical connection through the at least one substrate via.

20. An assembly comprising a receptacle according to any of claims 1-8 and a plug according to any of claims 9-19, wherein the receptacle is mechanically connected to the plug via the first set and the second set of means for mechanical connection so that the first conductor in the at least one signal cable is aligned with the deformable contact metal structure and connected to the deformable contact metal structure, and wherein the deformable contact metal structure is deformed when the plug and receptacle are connected to each other.

21. A quantum computing system comprising one or more assemblies according to claim 20.

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