Superconducting Qubit Layout for Longer Coherence and 3D Wiring
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Solution Overview
Problem
The coherence time of superconducting qubits in quantum computing systems is reduced due to strong electromagnetic coupling, particularly with linear arrangements that easily radiate energy, and scaling to a large number of qubits is hindered by spatial accommodation issues with in-plane wiring.
Innovation Solution
A superconducting qubit with coaxial electrodes and out-of-plane control and readout elements, reducing electromagnetic coupling and allowing for scalable multi-qubit systems by minimizing far-field radiation and enabling efficient control and measurement without requiring additional plane space.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If linear arrangement of superconducting electrodes is used, then coupling to control signals is improved, but electromagnetic coupling to environment increases and coherence time decreases
Solution Approach 1:
The patent transitions from a planar (2D) electrode arrangement to a three-dimensional (3D) configuration where electrodes are positioned at different heights above the substrate. This vertical dimensionality change allows control signals to be coupled effectively while isolating the qubit from environmental electromagnetic fields in the horizontal plane, thereby resolving the contradiction between ease of operation and reliability.
2Adaptability or versatility
If in-plane couplings and wiring are used, then qubit interconnections are achieved, but spatial accommodation becomes difficult as system size increases
Solution Approach 1:
The patent utilizes the vertical dimension to route control and readout wiring above and below the qubit array plane. This allows multiple qubits to be interconnected without requiring proportional increases in chip area, as connections extend in the third dimension rather than competing for surface space, thus resolving the contradiction between adaptability and area consumption.
Solution Approach 2:
The patent employs a layered architecture where control and readout elements are nested above and below the qubit plane. This nesting approach allows multiple functional layers to coexist in a compact volume, enabling complex qubit interconnections while minimizing the footprint of the quantum processor.
3Reliability
If qubits are embedded in high quality electromagnetic resonators, then environmental control is improved, but system complexity increases
Solution Approach 1:
The patent extracts the qubit from traditional planar resonator structures and positions it vertically above the substrate at a specific height. This extraction allows the qubit to be decoupled from environmental fields while maintaining simpler resonator configurations, reducing system complexity while preserving environmental control through the vertical positioning strategy.
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 significantly increases the coherence time of qubits and facilitates the scaling of quantum information processing systems to a larger number of qubits, improving the practicality of building a scalable quantum computer.
Implementation Method 1
a single Josephson junction in parallel with a capacitor... The Josephson junction combined with the capacitance between these electrodes implements a charge qubit
Implementation Method 2
a linear arrangement of the superconducting electrodes of a qubit typically mean that it couples strongly to the environment, particularly to electromagnetic fields... the coherence time of the quantum superposition state of the qubit... is reduced. This is because it is easy for the qubit to radiate energy
Implementation Method 3
embed the qubits within, or strongly couple them to, high quality electromagnetic resonators, either on-chip or in 3D, with resonant frequencies that are different from the qubit frequencies, thus preventing this energy leakage
Data Source
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AI summary
A building block (1) for a quantum information processing system includes a superconducting qubit (2) having a Josephson junction (5) connected between two superconducting electrodes (3, 4). The two superconducting electrodes (3, 4) are coaxial and coplanar. The building block (1) also includes a control line (6) coupled to the superconducting qubit (2) and arranged to control the state of the superconducting qubit (2), and/or a readout element (8) coupled to the superconducting qubit (2) and arranged to measure the state of the superconducting qubit (2). The control line (6) and/or the readout element (8) are arranged out of plane with respect to the two superconducting electrodes (3, 4).