Glossary / Quantum computing
Quantum error correction
Spreading the information of fragile qubits across many of them, so that errors can be detected and fixed.
Looking at a quantum state destroys it, so the ordinary trick of copying data and taking a majority vote does not work. For a while quantum error correction was thought impossible. In 1995 Peter Shor showed how to spread one qubit's information over nine, and to learn only where and what kind of error had occurred without reading the information itself[1].
The standard design since then adds helper qubits that measure the type of error; the measurement results are used to infer where the error happened and undo it. That inference is called decoding, and whether it keeps pace with the errors is a key question for practical machines.
Related terms
- Logical qubitA single, robust qubit made by bundling many physical qubits together and running error correction on them.
- DecodingThe calculation that takes the measurements from error correction and works out which qubits suffered which errors.
- Fault-tolerant quantum computingRunning quantum computations so that, even though components fail at some rate, layered error correction lets arbitrarily long calculations finish correctly.