Replica Coding for Quantum Error Correction

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Solution Overview

Problem

Adiabatic quantum computation and quantum annealing face challenges in error correction due to decoherence and noise, which can cause the actual parameters in the problem Hamiltonian to diverge from intended values, leading to incorrect solutions.

Innovation Solution

Implementing a replica coding scheme in quantum processors, where multiple identical instances of the problem are encoded, and coupling between replicas is used to correct errors and reduce the influence of decoherence and noise, effectively stabilizing the solution by smearing out noise influences across replicas.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple replica instances are implemented to correct errors, then reliability is improved, but device complexity increases

Engineering Contradiction:
Improveerror correction capabilityVSAvoidnumber of qubits and coupling devices
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The patent implements replica coding by creating multiple identical copies (replicas) of the quantum system encoding the same problem instance. Each replica consists of identical qubits and coupling devices configured to represent the same optimization problem. By comparing results across multiple replicas, the system can identify and correct errors caused by decoherence and noise, thereby improving reliability without requiring fundamentally new system architectures.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The patent combines multiple replica instances into a single computational framework where results from all replicas are aggregated and compared. The coupling devices connect corresponding qubits across replicas, enabling joint evolution and error correction. This merging approach allows the system to leverage collective information from multiple replicas to identify the correct solution, improving reliability while managing complexity through systematic integration.

Inventive Principle:
Principle #5Merging (Combining)

2Measurement precision

If replica coding is implemented to reduce noise influence, then measurement precision is improved, but manufacturing precision requirements increase

Engineering Contradiction:
Improvesolution accuracyVSAvoidparameter consistency across replicas
Core Design Contradiction:
Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent employs homogeneous replica structures where each replica is constructed with identical qubits, coupling devices, and Hamiltonian parameters. This homogeneity ensures that all replicas experience the same noise and decoherence effects, allowing systematic error cancellation through comparison. The consistent manufacturing across replicas reduces the influence of random noise while making the system more robust to parameter variations.

Inventive Principle:
Principle #33Homogeneity

Solution Approach 2:

The system uses feedback by comparing measurement results across multiple replicas to identify and correct errors. When replicas produce consistent results, confidence in the solution increases; when discrepancies arise, the system can identify potential errors and adjust accordingly. This feedback mechanism improves measurement precision by leveraging collective information from all replicas to validate and refine the final solution.

Inventive Principle:
Principle #23Feedback

3Productivity

If evolution speed is increased to improve productivity, then loss of information increases due to decoherence

Engineering Contradiction:
Improvecomputation speedVSAvoiddecoherence effects
Core Design Contradiction:
ProductivityVSLoss of information

Solution Approach 1:

By implementing multiple replicas of the quantum system, the patent enables parallel evolution of identical problem instances. Each replica evolves independently through the same Hamiltonian schedule, allowing faster evolution speeds while maintaining solution integrity through replica comparison. The copying approach distributes the computational workload across multiple identical systems, improving productivity without sacrificing accuracy.

Inventive Principle:
Principle #26Copying

Solution Approach 2:

The system uses real-time feedback from multiple replicas to monitor and correct decoherence effects during evolution. By continuously comparing the states of corresponding qubits across replicas, the system can identify deviations caused by rapid evolution and apply corrective measures. This feedback mechanism enables faster evolution speeds while minimizing information loss through active error management.

Inventive Principle:
Principle #23Feedback

Data Source

PatentEP2954416B1Systems and methods for error correction in quantum computation
Publication Date: 2021.05.12 D WAVE SYSTEMS INC
  • EP2954416B1 patent drawingFigure 1
  • EP2954416B1 patent drawingFigure 2
  • EP2954416B1 patent drawingFigure 3

AI summary

The effects of decoherence and/or noise in adiabatic quantum computation and quantum annealing are reduced by implementing replica coding schemes. Multiple instances of the same problem are mapped to respective subsets of the qubits and coupling devices of a quantum processor. The multiple instances are evolved simultaneously in the presence of coupling between the qubits of different instances. Quantum processor architectures that are adapted to facilitate replica coding are also described.