Unitary matrices

A unitary matrix is a complex matrix $U$ satisfying the condition

$U^{\dagger }U=UU^{\dagger }=I_{n}\,$

where $I$ is the identity matrix and $U^{\dagger }$ is the conjugate transpose (also called the Hermitian adjoint) of Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U} . Note this condition says that a matrix Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U} is unitary if and only if it has an inverse which is equal to its conjugate transpose Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U^\dagger \,}

Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "https://wikimedia.org/api/rest_v1/":): {\displaystyle U^{-1} = U^\dagger.}

A unitary matrix in which all entries are real is called an orthogonal matrix.

References

• Unitary matrix entry in Wikipedia