US-20260128193-A1 - Flexible Cables for Communicating Electrical Signals in a Cryogenic System

US20260128193A1US 20260128193 A1US20260128193 A1US 20260128193A1US-20260128193-A1

Abstract

In a general aspect, a flexible cable communicates electromagnetic signals in a cryogenic system. In some aspects, the flexible cable includes a signal layer and a ground layer. The signal layer includes signal lines embedded in adhesive material. Each signal line includes a multilayer structure. The multilayer structure includes a layer of non-superconducting material and a layer of rhenium metal. The ground layer is laminated to the signal layer.

Inventors

David Pappas

Assignees

RIGETTI & CO, LLC

Dates

Publication Date: 20260507
Application Date: 20250829

Claims (20)

1 . A flexible cable for communicating signals in a cryogenic system, the flexible cable comprising: a signal layer comprising signal lines embedded in adhesive material, each signal line comprising a multilayer structure comprising a layer of non-superconducting material and a layer of rhenium metal; and a ground layer laminated to the signal layer.
2 . The flexible cable of claim 1 , wherein the non-superconducting material comprises a noble metal.
3 . The flexible cable of claim 2 , wherein the noble metal comprises gold.
4 . The flexible cable of claim 2 , wherein the multilayer structure comprises a termination layer.
5 . The flexible cable of claim 4 , wherein the termination layer comprises a layer of gold.
6 . The flexible cable of claim 2 , wherein the noble metal comprises one or more of copper, silver, nickel, platinum, or palladium.
7 . The flexible cable of claim 1 , wherein the ground layer comprises a multilayer structure comprising a layer of non-superconducting material and a layer of rhenium metal.
8 . The flexible cable of claim 1 , wherein the ground layer is a first ground layer, the flexible cable comprises a second ground layer laminated to the signal layer, such that the signal layer resides between the first and second ground layers.
9 . The flexible cable of claim 8 , comprising: a plurality of conductive vias extending through the signal layer and the first and second ground layers.
10 . The flexible cable of claim 9 , wherein the plurality of conductive vias pass between neighboring signal lines in the signal layer.
11 . The flexible cable of claim 9 , wherein each of the plurality of conductive vias comprises a multilayer structure comprising a layer of non-superconducting material and a layer of rhenium metal.
12 . The flexible cable of claim 1 , wherein the ground layer is laminated to the signal layer via a flexible insulating film.
13 . The flexible cable of claim 12 , wherein the flexible insulating film comprises polyimide.
14 . The flexible cable of claim 1 , wherein the rhenium metal has an amorphous structure.
15 . The flexible cable of claim 1 , wherein the signal layer is a first signal layer, the flexible cable comprises a second signal layer, the ground layer is laminated between the first and second signal layers.
16 - 26 . (canceled)
27 . A method of fabricating a flexible cable configured to communicate signals in a cryogenic system, the method comprising: forming a signal layer comprising signal lines embedded in an adhesive material, wherein forming the signal layer comprises forming a multilayer structure of each signal line, the multilayer structure of each signal line comprising a layer of non-superconducting material and a layer of rhenium metal; and laminating a ground layer to the signal layer.
28 . The method of claim 27 , wherein forming the multilayer structure comprises: electroplating the layer of non-superconducting material on a surface of a substrate; and electroplating the layer of rhenium metal on the layer of non-superconducting material.
29 . The method of claim 28 , wherein the layer of non-superconducting material is a first layer, and the method comprises: electroplating a second layer of non-superconducting material on the layer of rhenium metal.
30 . The method of claim 28 , wherein the substrate is a first substrate, and the method comprises: forming a ground layer on a surface of a second substrate; attaching the ground layer to a first surface of a flexible insulating film via an adhesive layer comprising the adhesive material; and removing the second substrate to expose the second, opposite surface of the flexible insulating film.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63/488,370, filed Mar. 3, 2023, entitled “Flexible Cables for Communicating Electrical Signals in a Cryogenic System.” The above-referenced priority document is incorporated herein by reference in its entirety. TECHNICAL FIELD The following description relates to formation and operation of flexible cables for communicating electrical signals in a cryogenic system. BACKGROUND Quantum computers can perform computational tasks by storing and processing information within quantum states of quantum systems. For example, qubits (i.e., quantum bits) can be stored in and represented by an effective two-level sub-manifold of a quantum coherent physical system. A variety of physical systems have been proposed for quantum computing applications. Examples include superconducting circuits, trapped ions, spin systems and others. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an example computing environment. FIG. 2 is a block diagram showing aspects of an example cryostat. FIG. 3 includes a top view and cross-sectional view diagrams showing aspects of an example flexible cable. FIG. 4 is a flow chart showing aspects of an example process. FIG. 5A is an optical image showing aspects of an example flexible cable. FIG. 5B includes microscopic images and an electron microscopic image showing cross-sectional views of the example flexible cable shown in FIG. 5A. FIG. 6 is a plot showing the resistance value in Ohms as a function of the temperature in Kelvin. FIG. 7A is a schematic diagram showing aspects of an example flexible cable. FIG. 7B is a schematic diagram showing aspects of an example flexible cable. DETAILED DESCRIPTION In some example quantum computing systems, electromagnetic signals (e.g., radio or microwave frequency signals) are used to control and read qubit devices or other types of system components. These signals can be routed from controller and signal hardware through a set of interconnects that link stages of a cryogenic payload (including both DC and microwave components). The payload may include, for example, circulators, isolators, high-frequency filters, DC filters, amplifiers (solid-state low-noise amplifiers and/or Josephson Parametric Amplifiers), etc. In some implementations, the interconnects are flexible cables. In some aspects of what is described here, a flexible cable includes a signal layer laminated and sandwiched between two ground layers. The signal layer may include multiple signal lines running in parallel and extending between opposite ends of the flexible cable. The signal lines may be implemented, for example, as striplines, micro-strips, or coplanar waveguides. Each ground layer may include a ground plane laminated on a flexible insulating film. In some instances, two neighboring signal and ground layers are separated by a flexible insulating film. The signal lines and the ground planes of the flexible cable may include a multilayer structure with periodic stacks of alternating thin layers of at least two different materials. Each stack can include at least one superconducting material and at least one non-superconducting material. In certain examples, the superconducting material includes rhenium metal. In certain instances, the rhenium metal of the multilayer structure may include an amorphous structure. In some examples, the multilayered structure is formed using electroplating. In some instances, the periodic stacks in the multilayer structure includes at least three stacks of alternating thin layers of gold and rhenium. In some instances, the flexible cable having superconductivity at a cryogenic temperature can be used in a cryogenic system. The flexible cable may be solder-connected to high-density electrical connectors that allow electrical connection of the flexible cable to a quantum processing unit residing on a lowest-temperature thermalization stage. In some cases, the systems and methods described here can be used to address challenges introduced by the growth in the number of qubits in a quantum computing system. For example, the flexible cable described here can provide a higher density of signal lines at a lower cost than some other types of hardware, in some instances. For another example, the flexible cable may provide a lower thermal load; may be easily assembled and disassembled; and may be compact in size. Other advantages and improvements may be achieved in some cases. FIG. 1 is a block diagram of an example computing environment 100. The example computing environment 100 shown in FIG. 1 includes a computing system 101 and user devices 110A, 110B, 110C. A computing environment may include additional or different features, and the components of a computing environment may operate as described with respect to FIG. 1 or in another manner. The example computing system 101 includes classical and quantum computing resources and exposes