TensoredOp
class TensoredOp(oplist, coeff=1.0, abelian=False)
Bases: qiskit.opflow.list_ops.list_op.ListOp
A class for lazily representing tensor products of Operators. Often Operators cannot be efficiently tensored to one another, but may be manipulated further so that they can be later. This class holds logic to indicate that the Operators in oplist are meant to be tensored together, and therefore if they reach a point in which they can be, such as after conversion to QuantumCircuits, they can be reduced by tensor product.
Parameters
- oplist (
List[OperatorBase]) – The Operators being tensored. - coeff (
Union[complex,ParameterExpression]) – A coefficient multiplying the operator - abelian (
bool) – Indicates whether the Operators inoplistare known to mutually commute.
Methods Defined Here
eval
TensoredOp.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).
ListOp’s eval recursively evaluates each Operator in oplist, and combines the results using the recombination function combo_fn.
Parameters
front (Union[str, dict, ndarray, OperatorBase, Statevector, None]) – The bitstring, dict of bitstrings (with values being coefficients), or StateFn to evaluated by the Operator’s underlying function.
Return type
Union[OperatorBase, complex]
Returns
The output of the oplist Operators’ evaluation function, combined with the combo_fn. 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.
Raises
- NotImplementedError – Raised if called for a subclass which is not distributive.
- TypeError – Operators with mixed hierarchies, such as a ListOp containing both PrimitiveOps and ListOps, are not supported.
- NotImplementedError – Attempting to call ListOp’s eval from a non-distributive subclass.
reduce
TensoredOp.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.
Return type
Returns
The reduced OperatorBase.
tensor
TensoredOp.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.
Return type
Returns
An OperatorBase equivalent to the tensor product of self and other.
to_circuit
TensoredOp.to_circuit()
Returns the quantum circuit, representing the tensored operator.
Return type
Returns
The circuit representation of the tensored operator.
Raises
OpflowError – for operators where a single underlying circuit can not be produced.
to_matrix
TensoredOp.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.
Return type
ndarray
Returns
The NumPy ndarray equivalent to this Operator.
Attributes
INDENTATION
Default value: ' '
abelian
Whether the Operators in oplist are known to commute with one another.
Return type
bool
Returns
A bool indicating whether the oplist is Abelian.
coeff
The scalar coefficient multiplying the Operator.
Return type
Union[complex, ParameterExpression]
Returns
The coefficient.
coeffs
Return a list of the coefficients of the operators listed. Raises exception for nested Listops.
Return type
List[Union[complex, ParameterExpression]]
combo_fn
The function defining how to combine oplist (or Numbers, or NumPy arrays) to produce the Operator’s underlying function. For example, SummedOp’s combination function is to add all of the Operators in oplist.
Return type
Callable
Returns
The combination function.
distributive
Return type
bool
grad_combo_fn
The gradient of combo_fn.
Return type
Optional[Callable]
instance_id
Return the unique instance id.
Return type
int
num_qubits
Return type
int
oplist
The list of OperatorBases defining the underlying function of this Operator.
Return type
List[OperatorBase]
Returns
The Operators defining the ListOp
parameters
settings
Return settings.
Return type
Dict