Quantum Error Correction Codes

# Quantum Error Correction Codes

## Core Concepts

Quantum error correction (QEC) is crucial for building fault-tolerant quantum computers. Unlike classical bits, qubits are fragile and susceptible to decoherence and gate errors.  QEC aims to protect quantum information from these errors without collapsing the quantum state (due to the no-cloning theorem).  This is achieved by encoding a logical qubit into a larger number of physical qubits, creating redundancy.

**Key Challenges:**
*   **No-Cloning Theorem:**  Directly copying a qubit to create redundancy is impossible.
*   **Measurement Problem:** Measuring a qubit collapses its superposition, destroying the quantum information.
*   **Continuous Errors:** Quantum errors aren't just bit flips; they include phase flips and arbitrary rotations.

## Types of Quantum Errors