Superconducting Quantum Processor Spin-Bath Polarization Mitigation
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Solution Overview
Problem
Spin-bath polarization in superconducting quantum processors affects the performance of quantum annealing by introducing flux biases and reducing solution diversity, leading to undesirable correlations between successive samples.
Innovation Solution
Implement passive and active mitigation strategies, such as reducing qubit state storage time, using non-galvanic coupling, modifying annealing schedules, and actively flipping qubit states to depolarize the spin-bath, to minimize spin-bath polarization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If qubit state information is stored longer in the quantum processor body, then read-out accuracy may be improved, but spin-bath polarization increases causing flux biases and reducing solution diversity
Solution Approach 1:
The patent extracts the qubit state information from the quantum processor body by copying it to a shift register stage, thereby removing the source of spin-bath polarization while preserving the state for later read-out. This extraction eliminates the harmful interaction between stored states and the spin bath.
Solution Approach 2:
The patent introduces a shift register stage as an intermediary component between the quantum processor body and the read-out system. This intermediary holds the copied qubit states without causing spin-bath polarization, acting as a buffer that mediates between storage needs and polarization avoidance.
2Productivity
If quantum annealing cycles are performed in rapid succession, then productivity is improved, but spin-bath polarization accumulates causing undesirable correlations between successive samples
Solution Approach 1:
The patent extracts qubit state information to a shift register before completing the annealing cycle, allowing the quantum processor to be reset and reused immediately. This extraction enables rapid successive annealing cycles while preventing spin-bath polarization accumulation by removing states from the processor body.
Solution Approach 2:
The patent implements a periodic copying operation where qubit states are extracted to the shift register at regular intervals during annealing cycles. This periodic action resets the quantum processor body, enabling high-rate cycling while maintaining sample independence by preventing polarization buildup.
3Ease of manufacture
If galvanic coupling is used between qubits and QFPs, then ease of manufacture is improved, but spin-bath polarization is introduced through direct electrical connection
Solution Approach 1:
The patent introduces a shift register stage as an intermediary between the qubits and QFPs, eliminating the need for direct galvanic coupling. This intermediary transfers state information without requiring direct electrical connections, thereby avoiding spin-bath polarization while maintaining ease of manufacture through standard superconducting circuit techniques.
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
These methods effectively reduce spin-bath polarization, improving the accuracy and reliability of quantum annealing by minimizing flux biases and enhancing solution diversity.
Implementation Method 1
quantum annealing may use quantum effects, such as quantum tunneling, as a source of delocalization
Implementation Method 2
copying the state of the QFP into the next shift register stage to eliminate or at least reduce a contribution to spin-bath polarization caused by galvanic coupling of each qubit and the respective QFP
Data Source
AI summary
Passive and actives approaches to mitigating the effects of spin-bath polarization are described and illustrated. Such may, for example, include at least partially depolarizing the spin-bath polarization, for instance by: performing an annealing cycle by the quantum processor to generate a final state of a qubit of the quantum processor; flipping the final state of the qubit of the quantum processor to an opposite state; and latching the qubit in the opposite state for a predetermined duration.