Flux-Tuned Multimode Coupler for Low-Crosstalk Qubit Gates
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Solution Overview
Problem
Superconducting quantum computing systems face challenges in scaling due to unwanted crosstalk, particularly static ZZ interactions and exchange interactions between superconducting qubits, which affect the fidelity of quantum gate operations and entanglement gate operations.
Innovation Solution
A multimode coupler circuit is introduced, which can operate in two states to either suppress or enable interactions between superconducting qubits, using mode-selective exchange coupling to minimize crosstalk during single-qubit gate operations and facilitate high-fidelity entanglement gate operations by altering the coupling modes in response to flux tuning control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If superconducting qubits are coupled directly for quantum gate operations, then entanglement gate operations can be performed, but unwanted crosstalk and static ZZ interactions occur between adjacent qubits
Solution Approach 1:
A multimode coupler circuit is introduced as an intermediary between the first and second superconducting qubits. This coupler includes a first mode and a second mode that can be selectively excited. The coupler mediates the interaction between qubits, allowing controlled entanglement gate operations when both modes are excited, while suppressing unwanted static ZZ interactions when operating in single-mode configurations. This intermediary structure enables dynamic control of qubit coupling strength and topology.
2Reliability
If qubits are decoupled to suppress crosstalk during single-qubit operations, then quantum gate fidelity is maintained, but interaction between qubits is also suppressed
Solution Approach 1:
The multimode coupler circuit provides dynamic control over qubit interaction strength and topology. By adjusting the excitation state of the coupler modes, the system can transition between decoupled states (for high-fidelity single-qubit operations) and coupled states (for entanglement gate operations). The coupler's ability to switch between different coupling configurations enables adaptive control that maintains fidelity while enabling productive two-qubit operations when needed.
3Device complexity
If a simple single-mode coupler is used between qubits, then device complexity is reduced, but the ability to suppress both static ZZ interactions and exchange interactions is limited
Solution Approach 1:
The coupler circuit is segmented into multiple independent modes (first mode and second mode) that can be selectively excited and controlled. This segmentation allows different interaction types to be suppressed independently: one mode can be used to suppress static ZZ interactions while another mode handles exchange interactions. Each mode acts as an independent control channel, providing fine-grained suppression capability without requiring a monolithic complex structure.
4Reliability
If multimode coupler is used to suppress unwanted interactions, then quantum gate fidelity is improved, but device complexity increases
Solution Approach 1:
The multimode coupler circuit serves multiple functions within a single integrated structure: it enables entanglement gate operations, suppresses static ZZ interactions, suppresses exchange interactions, and provides dynamic control over coupling strength. By consolidating these multiple functions into one coupler device rather than requiring separate circuits for each function, the patent achieves high quantum gate fidelity while limiting the increase in overall device complexity.
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 approach allows for independent control of single-qubit gate operations and high-fidelity entanglement gate operations by minimizing crosstalk, enabling scalable quantum computing architectures with improved operational fidelity.
Implementation Method 1
The multimode coupler circuit is configured to operate in one of a first state and a second state, in response to a flux tuning control signal applied to the multimode coupler circuit
Implementation Method 2
A superconducting quantum computing system is implemented using circuit quantum electrodynamics (QED) devices, which utilize the quantum dynamics of electromagnetic fields in superconducting circuits
Data Source
AI summary
A device comprises first and second superconducting quantum bits, and a multimode coupler circuit coupled between the first and second superconducting quantum bits. The multimode coupler circuit comprises a first mode and a second mode, and is configured to operate in one of a first state and a second state, in response to a flux tuning control signal. In the first state, the first superconducting quantum bit is exchange coupled to the first mode, and the second superconducting quantum bit is exchange coupled to the second mode, to suppress interaction between the first and second superconducting quantum bits. In the second state, the first and second superconducting quantum bits are exchange coupled to both the first and second modes, to enable an interaction between the first and second superconducting quantum bits and perform an entanglement gate operation.