Quantum Memory Refresh Using LDPC Syndrome Correction
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Solution Overview
Problem
Quantum memory systems face high rates of fidelity loss due to decoherence and errors in quantum-gate devices, which existing error correction methods are unable to effectively address, particularly in maintaining reliable storage of entangled qubit states.
Innovation Solution
A memory system comprising a qubit array that uses a quantum stabilizer code and a quantum-state-refresh module with a low-density parity-check (LDPC) error-correction code for detecting and correcting errors by performing redundant measurements and applying message-passing decoding algorithms to maintain high fidelity of entangled qubit states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If quantum memory stores entangled qubit states for long-term storage, then storage duration is improved, but fidelity is lost due to decoherence and quantum-gate errors
Solution Approach 1:
The patent applies preliminary action by performing syndrome measurements and error corrections at regular intervals during quantum state storage. The quantum-state-refresh module continuously monitors the quantum state using stabilizer measurements and applies corrective operations before decoherence can significantly degrade the fidelity, thus enabling long-term storage while maintaining reliability
Solution Approach 2:
The patent implements feedback through the quantum error correction cycle: syndrome measurements detect errors, classical decoding algorithms identify correction operations, and quantum gates apply corrections to the quantum state. This closed-loop feedback system continuously counteracts decoherence and gate errors, allowing extended storage duration while preserving fidelity
2Measurement precision
If redundant syndrome measurements are performed using block error-correction codes, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the quantum error correction process into separate modules: syndrome measurement circuits that perform redundant measurements, classical decoding systems that process measurement outcomes, and quantum correction circuits that apply corrections. This modular segmentation allows precise error detection through redundant measurements while managing device complexity through functional decomposition
Solution Approach 2:
The patent uses an intermediary classical computing system to process syndrome measurements and determine correction operations. The classical decoder receives redundant syndrome measurements, applies error correction algorithms, and outputs correction instructions to quantum circuits. This intermediary approach improves measurement precision through classical post-processing while avoiding direct quantum-classical complexity entanglement
Data Source
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AI summary
A memory system comprising a qubit array configured to store therein and read one or more entangled qubit states encoded using a quantum stabilizer code. The quantum-memory system further comprises a quantum-state -refresh module configured to change an entangled qubit state in the qubit array when an error is detected therein. The quantum-state -refresh module is configured to detect an error by performing a redundant measurement of a set of syndrome values corresponding to the quantum stabilizer code, with the redundant measurement being based on a block error-correction code. In one embodiment, the block error-correction code is a low-density generator-matrix code or a low-density parity-check code constructed using an EXIT-function optimization method.