Superconducting DC-Microwave Combiner With Filtered Signal Isolation
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Solution Overview
Problem
Superconducting devices for quantum computing face challenges with large inductances that are difficult to realize, occupy significant space, and introduce signal loss, making it necessary to reduce inductance and improve signal transmission and isolation.
Innovation Solution
The development of a superconducting device with a direct current circuit and a microwave circuit joined by a common circuit, incorporating bandstop or bandpass filters and quarter-wavelength transmission lines, allows for improved bandwidth and isolation by combining or separating direct current and microwave signals, reducing inductance and enabling on-chip implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional superconducting devices use large inductances to combine DC-currents and microwave signals, then signal combination is achieved, but device space occupation increases and signal loss is introduced
Solution Approach 1:
The device is segmented into distinct DC-current circuit and microwave signal circuit portions, each optimized for its specific function. The DC-current circuit includes DC-current sources and bias tees, while the microwave signal circuit includes amplifiers and mixers, allowing each segment to operate with optimal characteristics without compromising the other
Solution Approach 2:
Bias tees serve as intermediary components that enable the combination of DC-currents and microwave signals through a common inductor without direct interference. The bias tee structure with its specific inductor and capacitor arrangement acts as a mediator that separates the DC and RF paths while allowing both to coexist
2Ease of manufacture
If traditional superconducting devices use large inductances for signal combination, then DC-current and microwave signal transmission is enabled, but manufacturing complexity increases
Solution Approach 1:
The circuit is divided into modular segments including DC-current sources, bias tees, microwave amplifiers, and mixers that can be independently designed, fabricated, and tested. This modular approach simplifies the manufacturing process by allowing each segment to be optimized separately
Solution Approach 2:
The device incorporates tunable elements such as variable bias currents and adjustable amplifier gain settings that allow the system to be optimized for different operating conditions. This dynamic capability reduces the need for multiple fixed-design devices
3Reliability
If bandstop circuits are used to block microwave signals in DC-current circuit, then microwave isolation is improved, but bandwidth for DC-current transmission may be affected
Solution Approach 1:
The bandstop filter is applied locally only to the DC-current circuit path where microwave rejection is needed, while the microwave signal circuit maintains its full bandwidth capability. This localized application ensures microwave isolation without compromising the overall system bandwidth
Solution Approach 2:
The bias tee inductor acts as an intermediary that naturally provides frequency separation between DC and microwave signals, working in conjunction with the bandstop filter to enhance isolation while preserving bandwidth
Data Source
AI summary
Techniques that facilitate a superconducting combiner or separator of DC-currents and microwave signals are provided. In one example, a device includes a direct current circuit and a microwave circuit. The direct current circuit comprises a bandstop circuit and provides transmission of a direct current signal. The microwave circuit provides transmission of a microwave signal. The microwave circuit and the direct current circuit that comprises the bandstop circuit are joined by a common circuit that provides transmission of the direct current signal and the microwave signal.