A key issue in developing quantum computers is the implementation of quantum error correction. If physical noise corrupts one or more qubits, error correction codes make it possible to detect and correct those errors, so long as the amount of corrupted data is under a given threshold.

The quantum threshold theorem states that if a quantum computer's physical error rate is low enough, the logical error rate can be reduced to arbitrarily low levels, achieving highly fault-tolerant general computing. Fowler, et al. proposed a scheme that could handle an error rate approaching 1%; the challenge will be designing schemes capable of handling higher error rates.