Quantum error correction (QEC) is a set of techniques used to protect quantum information from errors caused by decoherence, noise, and imperfect operations. Unlike classical bits, qubits can exist in superpositions and are highly sensitive to environmental disturbances, making error correction crucial for building reliable quantum computers.
Key Features:
- Redundancy with Entanglement: QEC encodes a single logical qubit into multiple physical qubits using entangled states, allowing detection and correction of errors without directly measuring the quantum information.
- Corrects Common Errors: Typical QEC codes handle bit-flip, phase-flip, and more general quantum errors.
- Examples: Shor code, Steane code, and surface codes are well-known QEC schemes.
- Threshold Theorem: If error rates are below a certain threshold, arbitrarily long and complex quantum computations become feasible with error correction.
Quantum error correction is not just desirable but necessary for scaling up quantum computers into practical, fault-tolerant systems.