Quantum Decoder Selection Using Spacetime Cost Metrics
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Solution Overview
Problem
The selection of a decoder for a fault-tolerant quantum computing device is challenging due to varying qubit noise rates, gate speeds, and measurement speeds, as existing metrics like asymptotic complexity do not provide sufficient information for optimal decoder choice.
Innovation Solution
A computing system is used to select a decoder by considering quantum circuit parameters, decoder parameters, and spacetime costs, including code distance, physical noise rate, and stopping time, to optimize decoder performance for a quantum computing device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a decoder is selected based on asymptotic complexity alone, then the theoretical computational efficiency is improved, but the actual performance does not account for varying qubit noise rates, gate speeds, and measurement speeds
Solution Approach 1:
The patent changes the selection parameters from purely theoretical asymptotic complexity to practical metrics including spacetime cost, physical noise rate, gate speeds, and measurement speeds. This allows the decoder selection to adapt to specific hardware characteristics while maintaining computational efficiency.
Solution Approach 2:
The patent introduces a dynamic decoder selection process where the optimal decoder is chosen based on real-time or scenario-specific hardware parameters such as noise rates and gate speeds, rather than a static selection based solely on asymptotic complexity.
2Measurement precision
If multiple decoder parameters including spacetime cost are computed and analyzed, then the accuracy of decoder selection is improved, but the computational overhead and system complexity increases
Solution Approach 1:
The patent performs preliminary computation of decoder parameters such as spacetime cost, stopping time, and range before the actual decoder selection. This allows the system to pre-evaluate multiple decoders and store their characteristics, reducing the complexity during the actual selection process.
Solution Approach 2:
The patent introduces an intermediary selection process that uses computed parameters like spacetime cost as intermediate metrics to bridge the gap between theoretical decoder performance and actual hardware-specific optimization, simplifying the final selection decision.
3Productivity
If the spacetime cost metric is used to evaluate decoders, then the balance between accuracy and resource usage is improved, but the computation time for evaluating all candidate decoders increases
Solution Approach 1:
The patent computes spacetime cost and other parameters for a selected subset or representative sample of candidate decoders rather than exhaustively evaluating all possible decoders. This partial evaluation approach maintains resource efficiency while reducing the time overhead of the selection process.
Data Source
AI summary
A computing system is provided, including one or more processing devices. The one or more processing devices are configured to receive quantum circuit parameters including a code parameter of an error correction code and a number of T gates included in a quantum circuit. The one or more processing devices are further configured to receive respective decoder parameters of each of a plurality of candidate decoders. The decoder parameters include a physical noise rate of a plurality of physical qubits at which the quantum circuit is configured to be executed and a stopping time of the candidate decoder. The one or more processing devices are further configured to compute respective spacetime costs of the candidate decoders based on the quantum circuit parameters and the decoder parameters. The one or more processing devices are further configured to output a selection of a lowest-spacetime-cost decoder for implementation at a quantum computing device.