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A complex Hadamard matrix is any complex matrix satisfying two conditions: *unimodularity (the modulus of each entry is unity): *orthogonality: , where denotes the Hermitian transpose of ''H'' and is the identity matrix. The concept is a generalization of the Hadamard matrix. Note that any complex Hadamard matrix can be made into a unitary matrix by multiplying it by . Complex Hadamard matrices arise in the study of operator algebras and the theory of quantum computation. Real Hadamard matrices and Butson-type Hadamard matrices form particular cases of complex Hadamard matrices. Complex Hadamard matrices exist for any natural ''N'' (compare the real case, in which existence is not known for every ''N''). For instance the Fourier matrices : belong to this class. ==Equivalency== Two complex Hadamard matrices are called equivalent, written , if there exist diagonal unitary matrices and permutation matrices such that : Any complex Hadamard matrix is equivalent to a dephased Hadamard matrix, in which all elements in the first row and first column are equal to unity. For and all complex Hadamard matrices are equivalent to the Fourier matrix . For there exists a continuous, one-parameter family of inequivalent complex Hadamard matrices, : For the following families of complex Hadamard matrices are known: * a single two-parameter family which includes , * a single one-parameter family , * a one-parameter orbit , including the circulant Hadamard matrix , * a two-parameter orbit including the previous two examples , * a one-parameter orbit of symmetric matrices, * a two-parameter orbit including the previous example , * a three-parameter orbit including all the previous examples , * a further construction with four degrees of freedom, , yielding other examples than , * a single point - one of the Butson-type Hadamard matrices, . It is not known, however, if this list is complete, but it is conjectured that is an exhaustive (but not necessarily irredundant) list of all complex Hadamard matrices of order 6. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Complex Hadamard matrix」の詳細全文を読む スポンサード リンク
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