Josephson Ring Modulator Tunable Coupler for Qubit Crosstalk
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Solution Overview
Problem
Current techniques for coupling two qubits in quantum computing face challenges such as residual crosstalk, unintentional coherent rotations, and reduced gate fidelity due to stringent frequency requirements and always-on qubit-qubit interactions.
Innovation Solution
A quantum coupler device utilizing a Josephson ring modulator (JRM) in a balanced bridge topology with tunable coupling, where qubits remain decoupled until a bias is applied, allowing for controlled and tunable coupling via RF or DC bias signals to facilitate parametric conversion or ZZ interactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If qubits are coupled using conventional techniques, then qubit-qubit interaction is achieved, but residual crosstalk and unintentional coherent rotations occur
Solution Approach 1:
The patent introduces a coupler as an intermediary element between qubits, which mediates their interaction. The coupler includes a first resonator coupled to a first qubit and a second resonator coupled to a second qubit, with coupling between the resonators being controllable. This intermediary structure isolates the qubits from direct harmful interactions while enabling controlled coupling, thereby reducing residual crosstalk and unintentional coherent rotations.
Solution Approach 2:
The patent implements dynamic control of the coupling between resonators through a controllable coupling mechanism that can adjust the coupling strength. This dynamic adjustment allows the system to optimize coupling conditions for desired interactions while minimizing unwanted crosstalk, improving gate fidelity by adapting the coupling characteristics in real-time based on operational requirements.
2Ease of operation
If qubits are always coupled, then interaction is available, but unintentional coherent rotations and reduced gate fidelity occur
Solution Approach 1:
The patent employs periodic modulation of the coupling between resonators through the controllable coupling mechanism. By applying periodic control signals, the coupling can be activated only during intended interaction periods and deactivated otherwise, preventing unintentional coherent rotations while maintaining ease of operation when coupling is needed.
Solution Approach 2:
The dynamic coupling control allows the system to transition between coupled and decoupled states as needed. The controllable coupling mechanism enables the system to provide qubit interaction availability on-demand while preventing unwanted interactions, thereby resolving the contradiction between ease of operation and gate fidelity.
3Manufacturing precision
If frequency requirements are made stringent to improve coupling, then coupling precision is achieved, but device complexity and operational constraints increase
Solution Approach 1:
The patent utilizes parameter changes in the controllable coupling mechanism to adjust coupling strength independently of fixed frequency constraints. By modifying coupling parameters dynamically rather than relying on stringent frequency matching, the system achieves precise coupling control while reducing device complexity and operational constraints associated with frequency management.
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
Enables zero quiescent coupling with high coupling rates (>1 GHz) while minimizing residual crosstalk, improving gate fidelity and flexibility in qubit interactions.
Implementation Method 1
Josephson ring modulator (JRM) that is operatively coupled to first and second qubits
Implementation Method 2
coupled to the JRM via capacitive devices in a balanced bridge topology
Data Source
AI summary
Techniques facilitating a quantum gate between qubits using a tunable coupler are provided. In one example, a quantum coupler device can comprise a Josephson ring modulator (JRM) that is operatively coupled to first and second qubits in a balanced bridge topology via respective first and second capacitive devices. The JRM provides tunable coupling between the first and second qubits.