OperatorBase
class qiskit.opflow.OperatorBase
Bases: StarAlgebraMixin, TensorMixin, ABC(opens in a new tab)
Deprecated: A base class for all Operators: PrimitiveOps, StateFns, ListOps, etc. Operators are defined as functions which take one complex binary function to another. These complex binary functions are represented by StateFns, which are themselves a special class of Operators taking only the Zero StateFn to the complex binary function they represent.
Operators can be used to construct complicated functions and computation, and serve as the building blocks for algorithms.
The class qiskit.opflow.operator_base.OperatorBase is deprecated as of qiskit-terra 0.24.0. It will be removed in the Qiskit 1.0 release. For code migration guidelines, visit https://qisk.it/opflow_migration(opens in a new tab).
Attributes
INDENTATION
Default value: ' '
instance_id
Return the unique instance id.
num_qubits
The number of qubits over which the Operator is defined. If op.num_qubits == 5, then op.eval('1' * 5) will be valid, but op.eval('11') will not.
Returns
The number of qubits accepted by the Operator’s underlying function.
parameters
Return a set of Parameter objects contained in the Operator.
settings
Return settings of this object in a dictionary.
You can, for example, use this settings dictionary to serialize the object in JSON format, if the JSON encoder you use supports all types in the dictionary.
Returns
Object settings in a dictionary.
Methods
add
abstract add(other)
Return Operator addition of self and other, overloaded by +.
Parameters
other (OperatorBase) – An OperatorBase with the same number of qubits as self, and in the same ‘Operator’, ‘State function’, or ‘Measurement’ category as self (i.e. the same type of underlying function).
Returns
An OperatorBase equivalent to the sum of self and other.
Return type
adjoint
abstract adjoint()
Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by ~. For StateFns, this also turns the StateFn into a measurement.
Returns
An OperatorBase equivalent to the adjoint of self.
Return type
assign_parameters
abstract assign_parameters(param_dict)
Binds scalar values to any Terra Parameters in the coefficients or primitives of the Operator, or substitutes one Parameter for another. This method differs from Terra’s assign_parameters in that it also supports lists of values to assign for a give Parameter, in which case self will be copied for each parameterization in the binding list(s), and all the copies will be returned in an OpList. If lists of parameterizations are used, every Parameter in the param_dict must have the same length list of parameterizations.
Parameters
param_dict (Dict(opens in a new tab)[ParameterExpression, complex(opens in a new tab) |ParameterExpression |List(opens in a new tab)[complex(opens in a new tab) |ParameterExpression]]) – The dictionary of Parameters to replace, and values or lists of values by which to replace them.
Returns
The OperatorBase with the Parameters in self replaced by the values or Parameters in param_dict. If param_dict contains parameterization lists, this OperatorBase is an OpList.
Return type
bind_parameters
bind_parameters(param_dict)
Same as assign_parameters, but maintained for consistency with QuantumCircuit in Terra (which has both assign_parameters and bind_parameters).
Return type
compose
abstract compose(other, permutation=None, front=False)
Return Operator Composition between self and other (linear algebra-style: A@B(x) = A(B(x))), overloaded by @.
Note: You must be conscious of Quantum Circuit vs. Linear Algebra ordering conventions. Meaning, X.compose(Y) produces an X∘Y on qubit 0, but would produce a QuantumCircuit which looks like
-[Y]-[X]-
Because Terra prints circuits with the initial state at the left side of the circuit.
Parameters
- other (OperatorBase) – The
OperatorBasewith which to compose self. - permutation (List(opens in a new tab)[int(opens in a new tab)] | None) –
List[int]which defines permutation on other operator. - front (bool(opens in a new tab)) – If front==True, return
other.compose(self).
Returns
An OperatorBase equivalent to the function composition of self and other.
Return type
copy
equals
abstract equals(other)
Evaluate Equality between Operators, overloaded by ==. Only returns True if self and other are of the same representation (e.g. a DictStateFn and CircuitStateFn will never be equal, even if their vector representations are equal), their underlying primitives are equal (this means for ListOps, OperatorStateFns, or EvolvedOps the equality is evaluated recursively downwards), and their coefficients are equal.
Parameters
other (OperatorBase) – The OperatorBase to compare to self.
Returns
A bool equal to the equality of self and other.
Return type
eval
abstract eval(front=None)
Evaluate the Operator’s underlying function, either on a binary string or another Operator. A square binary Operator can be defined as a function taking a binary function to another binary function. This method returns the value of that function for a given StateFn or binary string. For example, op.eval('0110').eval('1110') can be seen as querying the Operator’s matrix representation by row 6 and column 14, and will return the complex value at those “indices.” Similarly for a StateFn, op.eval('1011') will return the complex value at row 11 of the vector representation of the StateFn, as all StateFns are defined to be evaluated from Zero implicitly (i.e. it is as if .eval('0000') is already called implicitly to always “indexing” from column 0).
If front is None, the matrix-representation of the operator is returned.
Parameters
front (str(opens in a new tab) |Dict(opens in a new tab)[str(opens in a new tab), complex(opens in a new tab)] | ndarray(opens in a new tab) |OperatorBase |Statevector | None) – The bitstring, dict of bitstrings (with values being coefficients), or StateFn to evaluated by the Operator’s underlying function, or None.
Returns
The output of the Operator’s evaluation function. If self is a StateFn, the result is a float or complex. If self is an Operator (PrimitiveOp, ComposedOp, SummedOp, EvolvedOp, etc.), the result is a StateFn. If front is None, the matrix-representation of the operator is returned, which is a MatrixOp for the operators and a VectorStateFn for state-functions. If either self or front contain proper ListOps (not ListOp subclasses), the result is an n-dimensional list of complex or StateFn results, resulting from the recursive evaluation by each OperatorBase in the ListOps.
Return type
is_hermitian
is_hermitian()
Return True if the operator is hermitian.
Returns: Boolean value
Return type
mul
abstract mul(scalar)
Returns the scalar multiplication of the Operator, overloaded by *, including support for Terra’s Parameters, which can be bound to values later (via bind_parameters).
Parameters
scalar (complex(opens in a new tab) |ParameterExpression) – The real or complex scalar by which to multiply the Operator, or the ParameterExpression to serve as a placeholder for a scalar factor.
Returns
An OperatorBase equivalent to product of self and scalar.
Return type
neg
neg()
Return the Operator’s negation, effectively just multiplying by -1.0, overloaded by -.
Returns
An OperatorBase equivalent to the negation of self.
Return type
permute
abstract permute(permutation)
Permutes the qubits of the operator.
Parameters
permutation (List(opens in a new tab)[int(opens in a new tab)]) – A list defining where each qubit should be permuted. The qubit at index j should be permuted to position permutation[j].
Returns
A new OperatorBase containing the permuted operator.
Raises
OpflowError – if indices do not define a new index for each qubit.
Return type
primitive_strings
abstract primitive_strings()
Return a set of strings describing the primitives contained in the Operator. For example, {'QuantumCircuit', 'Pauli'}. For hierarchical Operators, such as ListOps, this can help illuminate the primitives represented in the various recursive levels, and therefore which conversions can be applied.
Returns
A set of strings describing the primitives contained within the Operator.
Return type
reduce
abstract reduce()
Try collapsing the Operator structure, usually after some type of conversion, e.g. trying to add Operators in a SummedOp or delete needless IGates in a CircuitOp. If no reduction is available, just returns self.
Returns
The reduced OperatorBase.
tensor
abstract tensor(other)
Return tensor product between self and other, overloaded by ^. Note: You must be conscious of Qiskit’s big-endian bit printing convention. Meaning, X.tensor(Y) produces an X on qubit 0 and an Y on qubit 1, or X⨂Y, but would produce a QuantumCircuit which looks like
-[Y]- -[X]-
Because Terra prints circuits and results with qubit 0 at the end of the string or circuit.
Parameters
other (OperatorBase) – The OperatorBase to tensor product with self.
Returns
An OperatorBase equivalent to the tensor product of self and other.
Return type
tensorpower
abstract tensorpower(other)
Return tensor product with self multiple times, overloaded by ^.
Parameters
other (int(opens in a new tab)) – The int number of times to tensor product self with itself via tensorpower.
Returns
An OperatorBase equivalent to the tensorpower of self by other.
Return type
to_circuit_op
to_matrix
abstract to_matrix(massive=False)
Return NumPy representation of the Operator. Represents the evaluation of the Operator’s underlying function on every combination of basis binary strings. Warn if more than 16 qubits to force having to set massive=True if such a large vector is desired.
Returns
The NumPy ndarray equivalent to this Operator.
Return type
to_matrix_op
abstract to_matrix_op(massive=False)
Returns a MatrixOp equivalent to this Operator.
Return type
to_spmatrix
to_spmatrix()
Return SciPy sparse matrix representation of the Operator. Represents the evaluation of the Operator’s underlying function on every combination of basis binary strings.
Returns
The SciPy spmatrix equivalent to this Operator.
Return type
spmatrix