Quantum error correction (QEC) is a set of techniques used to protect quantum information from errors due to decoherence and other sources of noise. Quantum error correction is one approach to fault-tolerant quantum computing that can reduce the effects of noise on stored quantum information, faulty quantum gates, faulty quantum state preparation, and faulty measurements. Effective quantum error correction allows quantum computers to execute algorithms of higher complexity or greater circuit depth.
Many proposals exist for the implementation of quantum error correction. A popular approach is to compute with sets of entangled physical qubits, called 鈥渓ogical qubits鈥, that enable the detection and correction of errors without breaking quantum physics鈥 鈥渘o-cloning theorem鈥 while circumventing the 鈥measurement 辫谤辞产濒别尘鈥.
Copying quantum information is not possible due to the no-cloning theorem. To get around this you can spread the (logical) information of one logical qubit onto a highly entangled state of several (physical) qubits. .