Bandpass Josephson Parametric Amplifier for Qubit Readout Stability
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Solution Overview
Problem
Existing Josephson Traveling Wave Parametric Amplifiers (JTWPAs) suffer from wide amplification bandwidths that amplify irrelevant signals and quantum noise, are sensitive to impedance mismatches causing instability and integration issues, and require bulky, lossy isolators for impedance matching, hindering scalability in quantum computing.
Innovation Solution
A bandpass parametric amplifier circuit with a nonlinear distributed bandpass filter architecture, incorporating linear resonators for phase matching and high characteristic impedance, reducing insertion loss and impedance mismatch sensitivity, and integrating impedance matching networks for medium-range bandwidths centered around qubit readout frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a wide amplification bandwidth is used in JTWPAs, then more signals can be amplified, but irrelevant signals and quantum noise are also amplified
Solution Approach 1:
The amplifier bandwidth is segmented into a specific passband region that selectively amplifies only the qubit readout frequency while rejecting other frequencies. This is achieved through a bandpass filter structure with specific resonant frequencies that create a narrow amplification window, dividing the wide bandwidth into useful and harmful frequency regions.
Solution Approach 2:
The amplifier exhibits different gain characteristics at different frequencies - high gain at the qubit readout frequency and low gain elsewhere. This local quality variation is achieved by designing the bandpass filter to have peak transmission at the target frequency, allowing the amplifier to be highly selective rather than uniformly amplifying all frequencies.
2Reliability
If wideband magnetic-based isolators are added for impedance matching, then impedance mismatch effects are reduced, but device complexity and integration difficulty increase
Solution Approach 1:
The bandpass filter and impedance matching functions are merged into a single integrated structure. The bandpass filter is designed to provide both frequency selectivity and impedance transformation, eliminating the need for separate wideband magnetic isolators. This combines multiple functions into one component, reducing overall device complexity.
Solution Approach 2:
The bandpass filter structure serves multiple functions simultaneously: it provides frequency selectivity for the qubit readout signal, acts as an impedance matching network, and serves as the amplification medium. This multi-functionality replaces what would traditionally require multiple separate components, simplifying the overall device architecture.
3Power
If a large array of Josephson junctions is used for amplification, then amplification gain is improved, but sensitivity to impedance mismatches and instability increase
Solution Approach 1:
The amplifier uses dynamic pumping at a frequency away from the qubit readout frequency to achieve parametric amplification. This dynamic operation allows the system to achieve high gain while the bandpass filter provides static frequency selectivity that stabilizes the system against impedance variations. The combination of dynamic amplification and static filtering resolves the stability-gain tradeoff.
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 provides a directional amplifier with reduced noise, improved signal fidelity, and enhanced stability by focusing on qubit readout signals, reducing unwanted backaction and pump power requirements, while allowing integration with other microwave devices.
Implementation Method 1
The device is formed by a nonlinear transmission line, whose center conductor comprises a large array of Josephson junctions
Implementation Method 2
A bandpass parametric amplifier circuit with a nonlinear distributed bandpass filter architecture, incorporating linear resonators for phase matching
Data Source
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AI summary
A bandpass parametric amplifier circuit includes a plurality of unit cells. At least one unit cell includes a first inductor having a first node coupled to a center conductor and a second node coupled to ground. There is a first capacitor having a first node coupled to the center conductor and a second node coupled to ground. There is a second inductor having a first node coupled to the center conductor. A second capacitor has a first node coupled to a second node of the second inductor. The second capacitor and the second inductor are in series with the center conductor.