Buried Electrode Geometry for Superconducting Microwave Circuits
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Solution Overview
Problem
Superconducting microwave circuits face challenges in reducing microwave photon interactions with the environment, particularly at the substrate-to-air interface, which limits qubit lifetimes and coherence times, making it difficult to achieve efficient quantum computing architectures.
Innovation Solution
The design features a superconducting microwave circuit with a substrate having raised portions and electrodes with complementary protruding structures that confine the electromagnetic field energy within the substrate, reducing the participation ratio of the substrate-to-air interface and minimizing microwave losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If planar qubit and coplanar waveguide designs are made larger to reduce interface loss, then qubit T1 times are improved, but device scalability and packaging become compromised
Solution Approach 1:
The patent transitions from two-dimensional planar electrode designs to three-dimensional structures by forming electrodes that protrude into recesses of the substrate. This vertical dimensionality change allows the electromagnetic field to be confined within the substrate volume, reducing the participation ratio of the substrate-to-air interface while maintaining compact lateral dimensions suitable for scalability.
Solution Approach 2:
The electrode structures are nested within recesses formed in the substrate. The protruding electrode portions are positioned within the substrate volume, creating a nested configuration where the electrode is partially embedded in the substrate. This nesting approach reduces the effective interface area exposed to air while maintaining electrical functionality.
2Loss of energy
If qubit size is increased to reduce participation ratio of interface layers, then interface loss is reduced, but only logarithmic improvement is achieved and scalability is compromised
Solution Approach 1:
Instead of increasing lateral dimensions to reduce participation ratio, the patent utilizes the vertical dimension by forming recesses in the substrate and positioning electrodes within these recesses. This approach confines the electromagnetic field energy density within the substrate volume, achieving exponential reduction in participation ratio rather than logarithmic improvement through size increase.
Solution Approach 2:
The patent applies different geometric configurations to different regions: the substrate has recesses formed at specific locations where electrodes will be positioned. This local structural modification creates regions of high field confinement within the substrate while maintaining standard planar regions elsewhere, optimizing the overall loss characteristics without requiring universal size increase.
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 effectively reduces microwave losses and enhances qubit coherence times by confining electromagnetic fields within the substrate, allowing for smaller qubit sizes while maintaining improved quality factors and scalability.
Implementation Method 1
The design features a superconducting microwave circuit with a substrate having raised portions and electrodes with complementary protruding structures that confine the electromagnetic field energy within the substrate
Implementation Method 2
Each of the electrodes comprises a structure that includes a potentially superconducting material
Data Source
AI summary
Embodiments are directed to a superconducting microwave circuit. The circuit includes a substrate and two electrodes. The latter form an electrode pair dimensioned so as to support an electromagnetic field, which allows the circuit to be operated in the microwave domain. The substrate exhibits a raised portion, which includes a top surface and two lateral surfaces. The top surface connects the two lateral surfaces, which show respective undercuts (on the lateral sides of the raised portions). Each of the electrodes includes a structure that includes a potentially superconducting material. Two protruding structures are accordingly formed, which are shaped complementarily to the respective undercuts. This way, the shaped structure of each of the electrodes protrudes toward the other one of the electrodes of the pair.