Quantum Error Correction

Understand

Quantum error correction is a set of methods to protect quantum information--that is, quantum states--from unwanted environmental interactions (decoherence) and other forms of noise.

• The information is stored in a quantum error-correcting code, which is a subspace in a larger Hilbert space.
• This code is designed so that the most common errors move the state into an error space orthogonal to the original code space while preserving the information in the state.
• It is possible to determine whether an error has occurred by a suitable measurement and to apply a unitary correction that returns the state to the code space, without measuring (and hence disturbing) the protected state itself.