= Quantum error detection
{title2=$PEP=c_EP$}
A code with <orthogonal projector> $P$ detects an error $E$ when its compression to the code is scalar. A <projective measurement> of $P$ then either flags departure from the code or, on a successful code-space outcome, leaves the logical state unchanged up to normalization. This includes harmless scalar errors, even though they need not produce a nonzero <error syndrome>. Detectability extends by linearity to the span of a set of errors. Every <Pauli operator> of weight less than the <quantum code distance> is detectable.
Back to article page
