[q4h555qh5]

QECC takes "logical qubits on a larger space" to "corrected qubits on a smaller space". So while there is entropy production on the entire space (2nd law thermo), it is still possible to have entropy reduction locally.

Eg: 0) "1 important qubit in some specific pure state" (entropy=0) + "4 ancillary qubits in some known but unimportant state"(entropy=0) are made using a 1to5 QECC into:

1) 1 logical qubit(made of 5-qubits) in a pure state (entropy=0)

2) Presence of noise: 5-qubits now in mixed-state (entropy=a>0)

3) Error correction on 5-qubits turning them into:

4) "1 important qubit in some specific pure state"(entropy=0) + "4 ancillary qubits in some now-random states" (entropy>=a>0)