Quantum codes from Hadamard matrices
W.-F. Ke, Kun-Sian Lai, R. B. Zhang · Linear and Multilinear Algebra · 2010
From each q × q unitary matrix Φ, we construct a family of quantum codes , t ≥ 1, for q-state systems which encode (2t + 1)2 q-states into one q-state. We show that such codes are capable of correcting the errors of weight up to t if and only if Φ is a complex Hadamard matrix.