qml.I

I

The Identity operator

The expectation of this observable

\[E[I] = \text{Tr}(I \rho)\]

See also

The equivalent long-form alias Identity

Parameters

• wires (Iterable[Any] or Any) – Wire label(s) that the identity acts on.

• id (str) – custom label given to an operator instance, can be useful for some applications where the instance has to be identified.

Corresponds to the trace of the quantum state, which in exact simulators should always be equal to 1.

Attributes

arithmetic_depth	Arithmetic depth of the operator.
basis	The basis of an operation, or for controlled gates, of the target operation.
batch_size	Batch size of the operator if it is used with broadcasted parameters.
control_wires	Control wires of the operator.
ev_order	Order in (x, p) that a CV observable is a polynomial of.
grad_method	Gradient computation method.
grad_recipe	Gradient recipe for the parameter-shift method.
has_adjoint
has_decomposition
has_diagonalizing_gates
has_generator
has_matrix
has_sparse_matrix
hash	Integer hash that uniquely represents the operator.
hyperparameters	Dictionary of non-trainable variables that this operation depends on.
id	Custom string to label a specific operator instance.
is_hermitian	All observables must be hermitian
name	String for the name of the operator.
ndim_params	Number of dimensions per trainable parameter of the operator.
num_params
num_wires	Number of wires that the operator acts on.
parameter_frequencies	Returns the frequencies for each operator parameter with respect to an expectation value of the form \(\langle \psi | U(\mathbf{p})^\dagger \hat{O} U(\mathbf{p})|\psi\rangle\).
parameters	Trainable parameters that the operator depends on.
pauli_rep	A PauliSentence representation of the Operator, or None if it doesn't have one.
supports_heisenberg
wires	Wires that the operator acts on.

Methods

adjoint()	Create an operation that is the adjoint of this one.
compare(other)	Compares with another Hamiltonian, Tensor, or Observable, to determine if they are equivalent.
compute_decomposition(wires[, n_wires])	Representation of the operator as a product of other operators (static method).
compute_diagonalizing_gates(wires[, n_wires])	Sequence of gates that diagonalize the operator in the computational basis (static method).
compute_eigvals([n_wires])	Eigenvalues of the operator in the computational basis (static method).
compute_matrix([n_wires])	Representation of the operator as a canonical matrix in the computational basis (static method).
compute_sparse_matrix([n_wires])	Representation of the operator as a sparse matrix in the computational basis (static method).
decomposition()	Representation of the operator as a product of other operators.
diagonalizing_gates()	Sequence of gates that diagonalize the operator in the computational basis.
eigvals()	Eigenvalues of the operator in the computational basis.
generator()	Generator of an operator that is in single-parameter-form.
heisenberg_expand(U, wire_order)	Expand the given local Heisenberg-picture array into a full-system one.
heisenberg_obs(wire_order)	Representation of the observable in the position/momentum operator basis.
identity_op(*params)	Alias for matrix representation of the identity operator.
label([decimals, base_label, cache])	A customizable string representation of the operator.
map_wires(wire_map)	Returns a copy of the current operator with its wires changed according to the given wire map.
matrix([wire_order])	Representation of the operator as a matrix in the computational basis.
pow(z)	A list of new operators equal to this one raised to the given power.
queue([context])	Append the operator to the Operator queue.
simplify()	Reduce the depth of nested operators to the minimum.
single_qubit_rot_angles()	The parameters required to implement a single-qubit gate as an equivalent Rot gate, up to a global phase.
sparse_matrix([wire_order])	Representation of the operator as a sparse matrix in the computational basis.
terms()	Representation of the operator as a linear combination of other operators.

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