  We propose a quantum error correction without error detection. A quantum
state $\rho_0$ combined with an ancilla state $\sigma$ is encoded unitarily and
an error operator is applied on the encoded state. The recovery operation then
produces a tensor product state $\rho_0 \otimes \sigma'$. The decoding
operation is combined with the recovery operation and the state $\rho_0$ is
directly reproduced without referring to the code word. A higher rank
projection operator required for a conventional operator quantum error
correction is not necessary to implement. Encoding and the recovery operations
are implemented with unitary operators only, which makes quantum error
correction much easier than any other proposals.
