ListOp

class ListOp(oplist, combo_fn=<function ListOp.<lambda>>, coeff=1.0, abelian=False)

A Class for manipulating List Operators, and parent class to SummedOp, ComposedOp, and TensoredOp.

List Operators are classes for storing and manipulating lists of Operators, State functions, or Measurements, and include some rule or combo_fn defining how the Operator functions of the list constituents should be combined to form to cumulative Operator function of the ListOp. For example, a SummedOp has an addition-based combo_fn, so once the Operators in its list are evaluated against some bitstring to produce a list of results, we know to add up those results to produce the final result of the SummedOp’s evaluation. In theory, this combo_fn can be any function over classical complex values, but for convenience we’ve chosen for them to be defined over NumPy arrays and values. This way, large numbers of evaluations, such as after calling to_matrix on the list constituents, can be efficiently combined. While the combination function is defined over classical values, it should be understood as the operation by which each Operators’ underlying function is combined to form the underlying Operator function of the ListOp. In this way, the ListOps are the basis for constructing large and sophisticated Operators, State Functions, and Measurements in Aqua.

The base ListOp class is particularly interesting, as its combo_fn is “the identity list Operation”. Meaning, if we understand the combo_fn as a function from a list of complex values to some output, one such function is returning the list as-is. This is powerful for constructing compact hierarchical Operators which return many measurements in multiple dimensional lists.

Parameters

• oplist (List[OperatorBase]) – The list of OperatorBases defining this Operator’s underlying function.

• combo_fn (callable) – The recombination function to combine classical results of the oplist Operators’ eval functions (e.g. sum).

• coeff (Union[int, float, complex, ParameterExpression]) – A coefficient multiplying the operator

• abelian (bool) – Indicates whether the Operators in oplist are known to mutually commute.

• the (Note that the default "recombination function" lambda above is essentially) –

• values (identity - it accepts the list of) –

• list. (and returns them in a) –

Attributes

ListOp.abelian	Whether the Operators in oplist are known to commute with one another.
ListOp.coeff	The scalar coefficient multiplying the Operator.
ListOp.combo_fn	The function defining how to combine oplist (or Numbers, or NumPy arrays) to produce the Operator’s underlying function.
ListOp.distributive	Indicates whether the ListOp or subclass is distributive under composition.
ListOp.num_qubits	The number of qubits over which the Operator is defined.
ListOp.oplist	The list of OperatorBases defining the underlying function of this Operator.

Methods

ListOp.__getitem__(offset)	Allows array-indexing style access to the Operators in oplist.
ListOp.__len__()	Length of oplist.
ListOp.__mul__(other)	Overload * for Operator scalar multiplication.
ListOp.add(other)	Return Operator addition of self and other, overloaded by +.
ListOp.adjoint()	Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by ~.
ListOp.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.
ListOp.bind_parameters(param_dict)	Same as assign_parameters, but maintained for consistency with QuantumCircuit in Terra (which has both assign_parameters and bind_parameters).
ListOp.compose(other)	Return Operator Composition between self and other (linear algebra-style: A@B(x) = A(B(x))), overloaded by @.
ListOp.equals(other)	Evaluate Equality between Operators, overloaded by ==.
ListOp.eval([front])	Evaluate the Operator’s underlying function, either on a binary string or another Operator.
ListOp.exp_i()	Return an OperatorBase equivalent to an exponentiation of self * -i, e^(-i*op).
ListOp.log_i([massive])	Return a MatrixOp equivalent to log(H)/-i for this operator H.
ListOp.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).
ListOp.neg()	Return the Operator’s negation, effectively just multiplying by -1.0, overloaded by -.
ListOp.power(exponent)	Return Operator composed with self multiple times, overloaded by **.
ListOp.primitive_strings()	Return a set of strings describing the primitives contained in the Operator.
ListOp.reduce()	Try collapsing the Operator structure, usually after some type of conversion, e.g.
ListOp.tensor(other)	Return tensor product between self and other, overloaded by ^.
ListOp.tensorpower(other)	Return tensor product with self multiple times, overloaded by ^.
ListOp.to_circuit_op()	Returns an equivalent Operator composed of only QuantumCircuit-based primitives, such as CircuitOp and CircuitStateFn.
ListOp.to_legacy_op([massive])	Attempt to return the Legacy Operator representation of the Operator.
ListOp.to_matrix([massive])	Return NumPy representation of the Operator.
ListOp.to_matrix_op([massive])	Returns an equivalent Operator composed of only NumPy-based primitives, such as MatrixOp and VectorStateFn.
ListOp.to_pauli_op([massive])	Returns an equivalent Operator composed of only Pauli-based primitives, such as PauliOp.
ListOp.to_spmatrix()	Returns SciPy sparse matrix representation of the Operator.
ListOp.traverse(convert_fn[, coeff])	Apply the convert_fn to each node in the oplist.
ListOp.__mul__(other)	Overload * for Operator scalar multiplication.