Superconducting Quantum Circuit Step-Impedance Control Line
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Solution Overview
Problem
In quantum information processing circuits, internal losses in resonators due to oscillation signal leakage to control ports are significant, complicating the suppression of internal loss, which is crucial for maintaining accuracy.
Innovation Solution
A superconducting quantum circuit design incorporating a control line with step-impedance characteristics, where different impedance segments are strategically positioned to minimize energy transmission to the control port, utilizing a step-impedance resonator to filter and reflect resonance energy, thereby reducing internal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a control line is connected to a control port to enable external control of resonance frequency, then the resonance frequency can be externally controlled, but oscillation signal leaks to the control port causing internal loss
Solution Approach 1:
The control line is divided into multiple sections with different characteristic impedances (first line with first impedance value, second line with second impedance value closer to the SQUID). This segmentation creates impedance discontinuities that reflect oscillation signals back toward the resonator, preventing them from reaching the control port and causing loss.
Solution Approach 2:
Different sections of the control line are assigned different local properties (different characteristic impedances) based on their position. The section closer to the SQUID has a different impedance than the section farther away, creating a stepped impedance profile that optimally reflects signals at each location while maintaining control functionality.
2Device complexity
If a simple control line is used for frequency control, then the device complexity is low, but oscillation signal transmission to control port increases internal loss
Solution Approach 1:
Instead of a uniform control line, the invention segments the control line into multiple portions with different characteristic impedances. This segmented structure remains relatively simple to fabricate while effectively reducing signal transmission to the control port through impedance-based reflection.
Solution Approach 2:
The characteristic impedance parameter of the control line is changed at different locations to create a stepped impedance profile. This parameter variation along the control line enables signal reflection without requiring complex active components or structures.
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 design effectively suppresses internal loss by reducing energy transmission to the control port, enhancing the circuit's efficiency and accuracy in quantum information processing.
Implementation Method 1
a control line configured to be connected to a first control port and magnetically coupled to the superconducting quantum interference device
Implementation Method 2
the control line includes at least a first line configured to have a characteristic impedance that indicates a first impedance value and a second line configured to be provided closer to a portion magnetically coupled to the superconducting quantum interference device than the first line and have a characteristic impedance that indicates a second impedance value being different from the first impedance value
Data Source
AI summary
A superconducting quantum circuit includes: a first resonator having a superconducting quantum interference device and a capacitor that forms a closed loop together with the superconducting quantum interference device; and a control line being connected to a first control port and magnetically coupled to the superconducting quantum interference device, wherein the control line includes at least a first line having a characteristic impedance that indicates a first impedance value, and a second line being provided closer to a portion magnetically coupled to the superconducting quantum interference device than the first line and having a characteristic impedance that indicates a second impedance value being different from the first impedance value.