Coupled-Line Bus Crosstalk Suppression for Superconducting Qubits
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Solution Overview
Problem
Superconducting quantum computing faces significant challenges in reducing classical crosstalk between qubits in different circuit planes, which affects signal integrity and increases error rates as the number of qubits increases.
Innovation Solution
A coupled-line bus architecture is implemented, where qubits are coupled differentially to excite only the odd mode of the bus, and the control line is orthogonal to the bus at the crossing point to suppress inductive coupling, using a dual strip coplanar waveguide transmission-line resonator, thereby mitigating crosstalk between circuit planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If control lines and coupled-line bus cross on different planes, then quantum computing functionality is enabled with multi-plane architecture, but classical crosstalk increases between qubits
Solution Approach 1:
The patent moves the control line and coupled-line bus from the same plane to different planes (third dimension), allowing them to cross without direct interaction. This spatial separation in the vertical dimension eliminates the crosstalk problem while maintaining the functionality of multi-plane quantum computing architecture.
Solution Approach 2:
The patent introduces an interposer chip as an intermediary layer between the qubit chip and readout chip. The interposer contains the control lines that route signals between qubits on different planes, acting as a mediator that enables multi-plane connectivity while isolating and managing the potential crosstalk through controlled impedance design and orthogonal routing.
2Productivity
If qubit density increases to improve computing power, then quantum processing capability improves, but crosstalk between qubits increases
Solution Approach 1:
The patent transitions from two-dimensional qubit arrangement to three-dimensional multi-plane architecture. Qubits are distributed across multiple vertical planes (qubit chip, interposer chip, readout chip), increasing density and processing capability while using the vertical dimension to spatially separate interacting elements and reduce crosstalk.
Solution Approach 2:
The patent segments the quantum computing system into distinct functional planes: qubit plane, control plane (interposer), and readout plane. This segmentation allows independent optimization of each plane, enabling higher qubit density on the qubit chip while maintaining signal integrity through dedicated control and readout pathways on separate planes.
3Area of stationary object
If control line and coupled-line bus are placed close together for compact design, then device area is reduced, but inductive coupling increases causing crosstalk
Solution Approach 1:
Instead of separating control lines and coupled-line bus in the horizontal plane (which would increase area), the patent separates them in the vertical dimension by placing them on different planes. This maintains compact footprint while eliminating inductive coupling through spatial isolation in the third dimension.
Solution Approach 2:
The patent employs asymmetric routing where the control line on the interposer chip crosses the coupled-line bus on the qubit chip at orthogonal angles. This asymmetric, orthogonal crossing minimizes the parallel overlap area between conductors, reducing inductive coupling while maintaining compact design.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces classical crosstalk by several orders of magnitude, improving signal integrity and fault tolerance in quantum computers by minimizing unwanted microwave coupling between qubits.
Implementation Method 1
the coupled-line bus is configured to transmit differential mode signals between the first and second qubits of the first quantum circuit plane
Implementation Method 2
the control line is orthogonal to the coupled-line bus at the crossing to suppress an inductive coupling between the control line and the coupled-line bus
Implementation Method 3
This approach significantly reduces classical crosstalk by several orders of magnitude, improving signal integrity and fault tolerance in quantum computers by minimizing unwanted microwave coupling between qubits
Data Source
AI summary
A system includes a first quantum circuit plane that includes a first qubit, a second qubit and a third qubit. A coupled-line bus is coupled between the first qubit and the second qubit. A second circuit plane is connected to the first quantum circuit plane, comprising a control line coupled to the third qubit. The control line and the coupled-line bus are on different planes and crossing over each other, and configured to mitigate cross-talk caused by the crossing during signal transmission.