Josephson Microwave Power Source With Variable-Resistance Biasing
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Solution Overview
Problem
Existing Josephson oscillators have modest efficiency in converting DC power into microwave power, with 85% dissipation as heat, which overloads cooling capacity and causes local heating, affecting signal quality and phase-noise properties, especially in large-scale quantum computing systems.
Innovation Solution
A microwave power source with a controllable bias circuit that includes a current path with variable resistance, responsive to control signals or bias signals, allowing precise adjustment of resistance values to optimize DC-to-microwave conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional bias circuit with fixed resistance is used in a Josephson oscillator, then the circuit structure is simple, but the DC-to-microwave conversion efficiency is low (around 15%) and heat dissipation is high (85% of input power)
Solution Approach 1:
The bias circuit incorporates a variable resistance element that can be dynamically adjusted to different resistance values. This dynamic adjustment allows the circuit to optimize the bias current flowing through the Josephson junction, thereby maximizing the DC-to-microwave conversion efficiency and minimizing heat dissipation in the biasing resistor, while maintaining manageable circuit complexity through controlled variability.
Solution Approach 2:
The invention changes the resistance parameter of the bias circuit from a fixed value to a variable value that can be tuned. By adjusting the resistance value, the bias current is optimized to achieve near-100% conversion efficiency. This parameter change transforms the bias circuit from a simple but inefficient structure to a tunable structure that minimizes energy loss while adding controlled complexity.
2Temperature
If the cooling capacity is increased to handle the heat dissipation from conventional Josephson oscillators, then the heat dissipation problem is solved, but the system complexity and cost increase
Solution Approach 1:
The invention converts the harmful heat dissipation in the biasing resistor into a beneficial outcome by using a variable resistance to minimize this dissipation. By optimizing the bias current through resistance adjustment, the heat generation is reduced to minimal levels, transforming the previously harmful thermal load into a manageable parameter that does not require excessive cooling capacity, thus avoiding increased cryostat complexity.
3Productivity
If a variable resistance bias circuit is used to optimize efficiency, then DC-to-microwave conversion efficiency reaches near 100%, but the bias circuit complexity increases
Solution Approach 1:
The bias circuit uses a variable resistance element that can be dynamically adjusted to optimize the bias current for maximum power conversion efficiency. This dynamic control allows the system to achieve near-100% efficiency by tuning the resistance to the optimal value, while the added complexity is limited to the variable resistance component and its control mechanism, which is manageable compared to the performance gain.
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
The solution achieves near-100% efficiency in DC-to-microwave power conversion, reducing heat dissipation and maintaining stable phase-locked operation, thereby improving signal quality and reducing cooling demands.
Implementation Method 1
A microwave power source for converting DC power into microwave, millimetre wave, and/or submillimetre wave signals comprises a Josephson junction or junction array
Implementation Method 2
a resonant tank circuit coupled to the Josephson junction and configured to resonate at one or more frequencies of Josephson oscillation generated in the Josephson junction
Implementation Method 3
Said bias circuit comprises a current path of variable resistance between a bias input of the microwave power source and a reference potential
Data Source
AI summary
A microwave power source comprises a Josephson junction or junction array and a resonant tank circuit coupled thereto and configured to resonate at one or more frequencies of Josephson oscillation. An output coupler is coupled to said resonant tank circuit for outputting microwave power from said resonant tank circuit. A bias circuit is coupled to the Josephson junction and configured to produce a bias voltage across the Josephson junction. Said bias circuit comprises a current path of variable resistance between a bias input of the microwave power source and a reference potential.