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1. ### en.wikipedia.org › wiki › Unitary_operatorUnitary operator - Wikipedia

A unitary operator is a bounded linear operator U : H → H on a Hilbert space H that satisfies U*U = UU* = I, where U* is the adjoint of U, and I : H → H is the identity operator. The weaker condition U*U = I defines an isometry. The other condition, UU* = I, defines a coisometry.

2. ### encyclopediaofmath.org › wiki › Unitary_operatorUnitary operator - Encyclopedia of Mathematics

Jun 6, 2020 · The most important unitary operators are those mapping a Hilbert space onto itself. Such an operator is unitary if and only if $( x, y) = ( Ux, Uy)$ for all $x, y \in X$. Other characterizations of a unitary operator $U: H \rightarrow ^ {\textrm { onto } } H$ are: 1) $U ^ {*} U = UU ^ {*} = I$, i.e. $U ^ {-} 1 = U ^ {*}$; and 2) the ...

3. ### www.pa.uky.edu › ~kwng › spring2009Hermitian and unitary operator - University of Kentucky

be real and hence an operator corresponds to a physical observable must be Hermitian. For example, momentum operator and Hamiltonian are Hermitian. An operator is Unitary if its inverse equal to its adjoints: U-1 = U+ or UU+ = U+U = I In quantum mechanics, unitary operator is used for change of basis. Hermitian and unitary operator

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4. ### math.stackexchange.com › questions › 3704040linear algebra - unitary operator explanation - Mathematics ...

Jun 3, 2020 · the unitary operator definition is T v, T w = v, w for every v, w in V. can you please explain the intuition and what the formal definition actually means? why unitary operator preserves the orthonormal basis? Can we infer from having unitary operator that we have eigenvectors?

5. ### phys.libretexts.org › Bookshelves › Quantum_Mechanics1.3: Hermitian and Unitary Operators - Physics LibreTexts

1.3: Hermitian and Unitary Operators. Last updated. Dec 8, 2021. 1.2: Operators in Hilbert Space. 1.4: Projection Operators and Tensor Products. Pieter Kok. University of Sheffield. Next, we will consider two special types of operators, namely Hermitian and unitary operators.

6. ### en.wikipedia.org › wiki › Unitary_matrixUnitary matrix - Wikipedia

Ucan be written as U= eiH, where eindicates the matrix exponential, iis the imaginary unit, and His a Hermitian matrix. For any nonnegative integern, the set of all n × nunitary matrices with matrix multiplication forms a group, called the unitary groupU(n). Any square matrix with unit Euclidean norm is the average of two unitary matrices.