Lumped Josephson Resonator Readout Without Fundamental-Mode Loss
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Solution Overview
Problem
Distributed constant-type nonlinear oscillators occupy a large area, making them unsuitable for integration in quantum computers, and existing methods for reducing loss and reading out states are not applicable to lumped constant-type oscillators.
Innovation Solution
A lumped constant-type oscillation apparatus with a resonator and magnetic-field generating means, including a loop circuit and capacitor, connected through a filter that restricts signal transmission in a specific frequency band, allowing for reduced loss and easy state reading by adjusting current values and frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If distributed constant-type nonlinear oscillators are used to reduce loss, then the loss of the fundamental mode is reduced, but the area occupied by the resonator becomes very large
Solution Approach 1:
The patent changes the type of oscillator from distributed constant-type to lumped constant-type, fundamentally altering the structural parameters. This allows the resonator to achieve low loss without requiring a large waveguide length, as the lumped constant-type design uses discrete circuit elements (inductors, capacitors, Josephson junctions) arranged in a compact configuration rather than a distributed transmission line structure.
Solution Approach 2:
The patent introduces a filter as an intermediary component between the lumped constant-type nonlinear oscillator and the read-out line. This filter selectively transmits the nth order mode while blocking the fundamental mode, enabling the oscillator to maintain low loss during operation while still allowing for effective read-out of the oscillator state through the filter's frequency-selective properties.
2Ease of operation
If coupling between nonlinear oscillator and read-out unit is made strong to enable reading-out, then reading-out becomes easy, but the loss of the nonlinear oscillator increases
Solution Approach 1:
The filter serves as a mediator that resolves the contradiction between strong coupling for easy read-out and weak coupling for low loss. By placing the filter between the oscillator and read-out unit, the system can have strong coupling overall while the filter's frequency selectivity ensures that only the nth order mode (not the fundamental mode) is transmitted to the read-out unit, thus maintaining low loss in the oscillator.
Solution Approach 2:
The patent applies local quality by making the coupling characteristics frequency-dependent through the filter. The coupling is strong for the nth order mode (enabling read-out) but weak for the fundamental mode (preserving low loss). This localized differentiation of coupling strength at different frequencies resolves the contradiction between ease of reading-out and loss reduction.
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 reduces loss and facilitates easy state reading of nonlinear oscillators, preventing the circuit from occupying a large area and enabling integration in quantum computers.
Implementation Method 1
a first Josephson junction, a second Josephson junction
Implementation Method 2
magnetic-field generating means configured to apply a magnetic field to the loop circuit
Implementation Method 3
a filter configured to restrict transmission of a signal in a predetermined frequency band
Implementation Method 4
the resonator including a loop circuit and a capacitor... the oscillator being configured to perform parametric oscillation
Data Source
AI summary
An oscillation apparatus includes: an oscillator including a resonator and a magnetic-field generating unit, the resonator including a loop circuit and a capacitor, the loop circuit including a first superconducting line, a first Josephson junction, a second superconducting line, and a second Josephson junction connected in a ring shape, the magnetic-field generating unit being configured to apply a magnetic field to the loop circuit, and the oscillator being configured to perform parametric oscillation; a read-out unit for reading out an internal state of the oscillator; and a filter configured to restrict transmission of a signal in a predetermined frequency band. A circuit in which the capacitor and the loop circuit are connected in a ring shape is connected to the read-out unit through the filter.