Skip to main contentIBM Quantum Documentation
You are viewing the API reference for an old version of Qiskit. Switch to latest version

TensoredOp

TensoredOp(oplist, coeff=1.0, abelian=False)GitHub(opens in a new tab)

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 in oplist are known to mutually commute.

Methods Defined Here

eval

TensoredOp.eval(front=None)GitHub(opens in a new tab)

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()GitHub(opens in a new tab)

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

OperatorBase

Returns

The reduced OperatorBase.

tensor

TensoredOp.tensor(other)GitHub(opens in a new tab)

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

OperatorBase

Returns

An OperatorBase equivalent to the tensor product of self and other.

to_circuit

TensoredOp.to_circuit()GitHub(opens in a new tab)

Returns the quantum circuit, representing the tensored operator.

Return type

QuantumCircuit

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)GitHub(opens in a new tab)

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

= '  '

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

Was this page helpful?