PERFECT QUANTUM ERROR-CORRECTING CODE

We present a quantum error correction code which protects a qubit of i nformation against general one qubit errors. To accomplish this, we en code the original state by distributing quantum information over five qubits, the minimal number required for this task. We describe a circu it which takes the initial state with four extra qubits in the state \ 10> to the encoded state. It can also be converted into a decoder by r unning it backward. The original state of the encoded qubit can then b e restored by a simple unitary transformation.