Josephson Parametric Coupler for Wideband Qubit Readout
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Solution Overview
Problem
Existing Josephson parametric amplifiers and converters are limited by low bandwidth and low saturation intensity, which restricts the number of qubits that can be read out in quantum computing systems.
Innovation Solution
A Josephson parametric coupler design using RF SQUIDs, which includes shunt resonators connected by admittance inverters, allows for a bandwidth of several hundred MHz and higher saturation intensity, enabling efficient signal amplification and frequency conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If existing Josephson parametric amplifiers and converters are used, then signal amplification can be achieved, but the bandwidth is limited to low values
Solution Approach 1:
The device is divided into two distinct sections: a first section with a first passband and a second section with a second passband. These sections are coupled through a Josephson junction coupling element, allowing each section to operate independently at different frequency ranges while maintaining overall system functionality.
Solution Approach 2:
The Josephson junction coupling element enables dynamic frequency conversion between the first and second passbands. By applying a pump tone to the coupling element, signals can be converted from one frequency band to another, effectively expanding the operational bandwidth of the amplifier.
2Power
If existing Josephson parametric amplifiers and converters are used, then amplification can be performed, but saturation intensity is low
Solution Approach 1:
The signal path is segmented into distinct frequency passbands handled by separate sections. This segmentation allows each section to be optimized for specific power handling characteristics, with the first section receiving signals from multiple qubits and the second section handling the converted output signals.
Solution Approach 2:
The device utilizes parametric modulation through the Josephson junction coupling element to change the effective impedance and coupling strength dynamically. By adjusting the pump tone parameters, the saturation power can be optimized while maintaining high qubit readout efficiency.
3Productivity
If bandwidth is increased to read out multiple qubits, then readout capacity improves, but noise performance degrades
Solution Approach 1:
Multiple qubit signals in different frequency ranges can be simultaneously amplified in the first section without mutual interference. The Josephson junction coupling element then converts these signals to the second passband, where they can be read out with high fidelity while maintaining near quantum-limited noise performance across the expanded bandwidth.
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 design provides a bandwidth of several hundred MHz with improved saturation power, enhancing the capacity to read out multiple qubits with near quantum-limited noise performance.
Implementation Method 1
a Josephson junction coupling element for parametric coupling between the first section and the second section. The Josephson junction coupling element is configured such that, in response to the input port receiving a first signal at a first frequency lying within the first passband and the Josephson junction coupling element receiving a pump tone, the Josephson junction coupling element converts the first signal into a second signal with a second frequency lying within the second passband
Data Source
AI summary
A Josephson parametric device is presented, which includes an input port, an output port, and a signal path between the input port and the output port. The signal path includes a first section coupled to the input port and having a first passband, a second section coupled to the output port and having a second passband and a Josephson junction coupling element for parametric coupling between the first and second section. The Josephson junction coupling element is coupled to and interposed between the first section and the second section. The Josephson junction coupling element is configured such that, in response to the input port receiving a first signal at a first frequency lying within the first passband and the Josephson junction coupling element receiving a pump tone, the Josephson junction coupling element converts the first signal into a second signal with a second frequency lying within the second passband.