Logical qubit
= Logical qubit
{title2=$\alpha|0_L\rangle+\beta|1_L\rangle$}
A <logical qubit> is a two-dimensional encoded quantum subsystem with chosen orthonormal logical basis states $|0_L\rangle,|1_L\rangle$. An encoding <linear isometry> sends $\alpha|0\rangle+\beta|1\rangle$ to $\alpha|0_L\rangle+\beta|1_L\rangle$. In a <concatenated quantum error-correcting code>, one level's <logical qubit> supplies one <qubit> of the next outer code.