アダマール行列
where formula_5 denotes the Hermitian transpose of formula_2 and formula_7 is the identity matrix. The concept is a generalization of the Hadamard matrix. Note that any complex Hadamard matrix formula_2 can be made into a unitary matrix by multiplying it by formula_9; conversely, any unitary matrix whose entries all have modulus formula_9 becomes a complex Hadamard upon multiplication by formula_11.