Tunable Floating Coupler Flux Parking for Superconducting Qubits
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Solution Overview
Problem
Existing quantum computing systems face challenges in maintaining consistent coupling strengths between qubits due to fabrication variations, leading to issues such as high 'always-on' coupling or weak coupling, which affects gate fidelity and scalability.
Innovation Solution
Implementing a tunable floating coupler device with asymmetric Josephson junctions that allows for adjustable coupling strength between qubits, controlled by magnetic flux bias, enabling activation and deactivation of qubit interactions to optimize gate fidelity and scalability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If static direct capacitive coupling is used between qubits, then coupling strength is maintained, but fabrication variations cause inconsistent coupling leading to high 'always-on' coupling or weak coupling
Solution Approach 1:
The patent implements a tunable coupler device that allows dynamic adjustment of coupling strength between qubits. The coupler's effective coupling strength can be tuned by adjusting its transition frequency or applying magnetic flux bias, enabling the system to compensate for fabrication variations and achieve consistent coupling despite manufacturing tolerances.
Solution Approach 2:
The patent changes the coupling parameter from a fixed static value to a tunable variable. By adjusting the coupler's transition frequency or magnetic flux bias, the effective coupling strength can be dynamically modified to achieve target coupling values, thereby compensating for fabrication-induced variations in capacitor values and qubit frequencies.
2Reliability
If tunable floating coupler device is implemented, then coupling strength can be adjusted to optimize gate fidelity, but device complexity increases
Solution Approach 1:
The tunable coupler device serves multiple functions: it enables selective activation/deactivation of qubit interactions, allows tuning of coupling strength to optimize gate fidelity, and can be integrated into scalable quantum processor architectures. The same coupler structure can be used for different coupling requirements by adjusting its operational parameters.
3Adaptability or versatility
If direct capacitive coupling is eliminated, then scalability is improved, but coupling control becomes more challenging
Solution Approach 1:
The patent introduces a tunable coupler device as an intermediary element between qubits. This coupler mediates the interaction between qubits, allowing coupling to be activated or deactivated as needed. The coupler's transition frequency can be tuned to enable or disable coupling, providing scalable control without requiring direct capacitive coupling between all qubit pairs.
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 tunable floating coupler device enhances quantum logic gate performance by compensating for fabrication-induced coupling variations, enabling faster and more stable operations, and allows for a scalable quantum processor architecture by eliminating the need for static direct capacitive coupling.
Implementation Method 1
The tunable floating coupler device includes asymmetric Josephson junctions that allows for adjustable coupling strength between qubits, controlled by magnetic flux bias
Data Source
AI summary
In a general aspect, a superconducting quantum processing unit includes a first qubit device, a second qubit device, and a tunable floating coupler device coupled between the first and second qubit devices. Values of a coupling strength of the first and second qubit devices at a plurality of operating points of the tunable floating coupler device are measured. The operating points correspond to respective values of a magnetic flux applied to the tunable floating coupler device. Based on the measured values of the coupling strength, a parking value of the magnetic flux is identified. The parking value of the magnetic flux corresponds to a magnitude of the coupling strength being less than or equal to a threshold value; the threshold value is associated with a target gate fidelity for the superconducting quantum processing unit.