Superconducting Qubit Coupler Layout for Stronger Four-Body Interaction
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Solution Overview
Problem
Existing superconducting quantum circuits face challenges in strengthening four-body interactions without requiring external inputs, as previous configurations either do not enhance this interaction or necessitate additional external signals.
Innovation Solution
A superconducting quantum circuit design that includes first to fourth qubits and a coupler with specific capacitance relationships, utilizing a nonlinear element and Josephson junctions to enhance four-body interactions through circuit configuration alone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a simple Josephson junction configuration is used for four-body interaction, then the device structure is simple, but the four-body interaction strength is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the capacitance values in the coupler circuit. Specifically, it introduces a relationship where C_J > C_g > C, where C_J is the capacitance of the parallel capacitor, C_g is the capacitance of the coupling capacitor, and C is the self-capacitance of each qubit. This parameter optimization enhances the four-body interaction strength while maintaining circuit simplicity.
2Force
If external microwave drive signals are used to enhance four-body interaction, then the interaction strength can be adjusted, but the device operation becomes more complex
Solution Approach 1:
The patent implements self-service by designing the coupler with specific capacitance relationships that automatically generate enhanced four-body interactions without requiring external control signals. The circuit configuration itself (with C_J > C_g > C) creates the necessary coupling conditions, eliminating the need for complex external microwave drive signal management.
3Force
If the capacitance values are optimized to strengthen four-body interaction, then the coupling constant increases, but other unwanted interactions may be enhanced
Solution Approach 1:
The patent applies local quality by assigning different capacitance values to different parts of the coupler circuit. The coupling capacitors have capacitance C_g, the parallel capacitors have capacitance C_J, and each qubit has self-capacitance C, with the specific relationship C_J > C_g > C. This localized differentiation of capacitance values enables selective enhancement of four-body interactions while suppressing unwanted two-body and other interactions.
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 circuit effectively strengthens four-body interactions by adjusting capacitance values, enhancing the coupling constant without requiring external inputs, while minimizing other interactions.
Implementation Method 1
a nonlinear element including a Josephson junction and bridging the first and second electrodes
Implementation Method 2
a capacitor connected in parallel to the loop circuit of each of the first to fourth qubits
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
To provide a superconducting quantum circuit enabled to strengthen four-body interaction by the circuit configuration itself, without requiring another external input. A superconducting quantum circuit includes first to fourth qubits, and a coupler that couples the first to fourth qubits with a four-body interaction, wherein the coupler includes first and second electrodes and a nonlinear element, the first and second electrodes being arranged opposed to each other, the nonlinear element including a Josephson junction and bridging the first and second electrodes, wherein each of the first to fourth qubits includes a resonator that includes a loop circuit with a first superconducting line, a first Josephson junction, a second superconducting line and a second Josephson junction connected in a ring-shape and a capacitor connected in parallel to the loop circuit, the first and second qubits are capacitively coupled to the first electrode of the coupler, the third and fourth qubits are capacitively coupled to the second electrode of the coupler, wherein a magnitude relationship among a capacitance value C of a capacitive coupling between each of the first to fourth qubits and the coupler, a capacitance value CJ of the capacitor connected in parallel to the loop circuit for each of the first to fourth qubits, and a capacitance value Cg between the first and second electrodes of the coupler, is set to CJ > Cg > C.