Josephson Parametric Converter Arrays for Scalable Qubit Readout
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Solution Overview
Problem
Conventional Josephson parametric converters (JPCs) suffer from limited dynamical bandwidth and dynamic range, making them unsuitable for scalable qubit readout architectures, with bandwidths around 10 MHz and maximum input power of a few photons at 20 dB of gain, which restricts their applicability.
Innovation Solution
Incorporating arrays of large Josephson junctions in Josephson ring modulators and using lumped-element capacitances to form resonators, enhancing the participation ratio and reducing the quality factor of the resonators to achieve a larger dynamical bandwidth and dynamic range, while maintaining a high critical current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional Josephson parametric converters are used, then device simplicity is maintained, but dynamical bandwidth is limited to around 10 MHz
Solution Approach 1:
The patent divides the Josephson junction array into multiple segments arranged in a ring configuration with distinct nodes. This segmentation allows independent tuning of different parts of the device, enabling broader bandwidth operation while maintaining manageable complexity through modular design
Solution Approach 2:
The patent transitions from conventional planar microstrip resonator geometry to a three-dimensional lumped-element capacitor configuration. This dimensional change enables higher participation ratios and lower quality factors, achieving over 100 MHz bandwidth without proportionally increasing device footprint
2Quantity of substance
If conventional Josephson parametric converters are used, then manufacturing simplicity is maintained, but dynamic range is limited to a few photons at 20 dB gain
Solution Approach 1:
The patent changes key operating parameters by using arrays of large Josephson junctions with high critical current rather than conventional single junctions. This parameter change enables the device to handle larger signal powers (dynamic range > -120 dBm at 20 dB gain) while the junction arrays are fabricated using standard superconducting thin-film techniques
Solution Approach 2:
The patent employs composite structures combining Josephson junction arrays with lumped-element capacitors formed from superconducting materials. This composite approach achieves enhanced dynamic range through the synergistic combination of nonlinear Josephson elements and linear capacitive elements, both compatible with existing superconducting fabrication processes
3Area of moving object
If conventional microstrip JPCs are used, then device footprint is maintained, but participation ratio is low and quality factor is high
Solution Approach 1:
The patent replaces extended microstrip resonator structures with compact lumped-element capacitor configurations. This dimensional transformation concentrates the electromagnetic field interaction in a small volume, achieving high participation ratios in a compact footprint suitable for scalable qubit readout architectures
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 configuration increases the dynamical bandwidth to over 100 MHz and dynamic range to more than −120 dBm at 20 dB of gain, enabling scalable qubit readout architectures and reducing the device footprint by approximately 300 times compared to microstrip JPCs.
Implementation Method 1
A Josephson ring modulator (JRM) is a nonlinear dispersive element based on Josephson tunnel junctions that can perform three-wave mixing of microwave signals at the quantum limit
Implementation Method 2
the JRM is incorporated into two microwave resonators at an RF-current anti-node of their fundamental Eigenmodes
Data Source
AI summary
A Josephson parametric converter is provided. The Josephson parametric converter includes a multi-Josephson junction ring modulator having arrays of Josephson junctions arranged in a ring configuration with ring nodes inter-dispersed between the arrays and a center node inter-connecting the ring nodes. The Josephson parametric also includes resonators formed from capacitors that shunt the multi-Josephson junction ring modulator and enable respective modes of the Josephson parametric converter.