Ground-Plane Josephson Coupler Layout for Four-Qubit Interaction
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Solution Overview
Problem
The existing superconducting quantum circuit apparatuses face challenges in increasing the strength of four-body interactions due to the effect of floating capacitance, which limits the coupling strength between qubits.
Innovation Solution
A superconducting quantum circuit apparatus is designed with a coupler configuration where the nonlinear element, including Josephson junctions, is arranged in a region surrounded by a ground plane, with extended electrodes and opposing portions to reduce floating capacitance, thereby enhancing the coupling strength by optimizing the capacitive coupling between qubits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional coupler configuration is used with qubits arranged on a planar circuit, then the device structure is simple and easy to manufacture, but the floating capacitance reduces the strength of four-body interactions between qubits
Solution Approach 1:
The patent transitions from a planar two-dimensional circuit layout to a three-dimensional configuration by positioning the coupler above the ground plane with electrodes extending in opposite directions. This vertical dimensionality change allows the coupler to interact with multiple qubits simultaneously while reducing parasitic floating capacitance effects that plague planar designs.
Solution Approach 2:
The coupler is divided into distinct functional segments: a first electrode with first and second opposing portions extending toward different qubits, and a second electrode with third and fourth opposing portions. This segmentation allows independent optimization of coupling paths to different qubits and facilitates better control over capacitance distribution.
2Strength
If the coupler electrodes are extended toward multiple qubits to increase coupling strength, then the four-body interaction strength increases, but the floating capacitance effect becomes more significant
Solution Approach 1:
The coupler acts as an intermediary element positioned between multiple qubits, with its electrodes extending toward but not directly contacting the qubits. This intermediary configuration enables indirect capacitive coupling that maintains strong interaction while reducing direct parasitic capacitance paths to ground.
Solution Approach 2:
The patent optimizes geometric parameters of the coupler electrodes including their length, width, spacing, and positioning relative to the ground plane and qubits. By carefully adjusting these parameters, the design achieves maximum coupling strength while minimizing floating capacitance effects that would otherwise cause energy loss.
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 configuration effectively suppresses the impact of floating capacitance, increasing the strength of four-body interactions and improving the coupling efficiency between qubits, leading to enhanced quantum computation capabilities.
Implementation Method 1
a nonlinear element including at least one Josephson junction bridged between the first electrode and the second electrode
Implementation Method 2
arranged in a region surrounded by a ground plane, with extended electrodes and opposing portions to reduce floating capacitance
Data Source
AI summary
A superconducting quantum circuit apparatus includes first through fourth qubits; and a coupler arranged in a region surrounded by a ground plane. The coupler includes: first and second electrodes opposed to each other; and a nonlinear element including at least one Josephson junction bridged between the first electrode and the second electrode between the first and second electrode, the first electrode including first and second opposing portions extended toward the first and second qubits, the second electrode including third and fourth opposing portions extended toward third and fourth qubit, the first through fourth opposing portions having ends for capacitive coupling with the first through fourth qubits, respectively. The ends of the first through fourth opposing portions are disposed within the region surrounded by the ground plane.