Quantum Error Correction (QEC)

How QEC detects and corrects faults without collapsing quantum information.

QEC uses auxiliary (ancilla) measurements to find faults and apply fixes, preserving the protected quantum state throughout the process.

The protected information remains in a superposition such as (|psirangle = alpha|0rangle + beta|1rangle); QEC extracts only error syndromes, not the amplitudes (alpha) and (beta).

1

Encode

Encode one logical qubit into many physical qubits. The logical state is

distributed non-locally so no single physical qubit holds the full information.

2

Syndrome Measurement

Measure auxiliary qubits (ancilla qubits) to detect the error location without

measuring and collapsing the protected quantum information.

3

Decode

Use a classical decoder to interpret the syndrome measurements and determine the

error location.

4

Correct

Correct the error without destroying quantum information, restoring the logical

state.