Definition:Unitary Matrix

Definition

Let $\mathbf U$ be an invertible square matrix over the complex numbers $\C$.

Then $\mathbf U$ is unitary if and only if:

$\mathbf U^{-1} = \mathbf U^\dagger$

where:

$\mathbf U^{-1}$ is the inverse of $\mathbf U$

$\mathbf U^\dagger$ is the Hermitian conjugate of $\mathbf U$.

Also see

• Definition:Unitary Group
• Definition:Unitary Operator
• Definition:Hermitian Matrix
• Definition:Orthogonal Matrix

• Results about unitary matrices can be found here.