ListOp¶

class
ListOp
(oplist, combo_fn=None, coeff=1.0, abelian=False, grad_combo_fn=None)[source]¶ Bases:
qiskit.opflow.operator_base.OperatorBase
A Class for manipulating List Operators, and parent class to
SummedOp
,ComposedOp
, andTensoredOp
.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 theListOp
. For example, aSummedOp
has an additionbasedcombo_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 theSummedOp
's evaluation. In theory, thiscombo_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 callingto_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 theListOp
. In this way, theListOps
are the basis for constructing large and sophisticated Operators, State Functions, and Measurements.The base
ListOp
class is particularly interesting, as itscombo_fn
is "the identity list Operation". Meaning, if we understand thecombo_fn
as a function from a list of complex values to some output, one such function is returning the list asis. This is powerful for constructing compact hierarchical Operators which return many measurements in multiple dimensional lists. Parameters
oplist (
Sequence
[OperatorBase
])  The list ofOperatorBases
defining this Operator's underlying function.combo_fn (
Optional
[Callable
])  The recombination function to combine classical results of theoplist
Operators' eval functions (e.g. sum). Default is lambda x: x.coeff (
Union
[complex
,ParameterExpression
])  A coefficient multiplying the operatorabelian (
bool
)  Indicates whether the Operators inoplist
are known to mutually commute.grad_combo_fn (
Optional
[Callable
])  The gradient of recombination function. If None, the gradient will be computed automatically.that the default "recombination function" lambda above is essentially the (Note) 
 it accepts the list of values (identity) 
returns them in a list. (and) 
Methods Defined Here
Return Operator addition of self and other, overloaded by
+
.Return a new Operator equal to the Operator's adjoint (conjugate transpose), overloaded by
~
.Binds scalar values to any Terra
Parameters
in the coefficients or primitives of the Operator, or substitutes oneParameter
for another.Return Operator Composition between self and other (linear algebrastyle: A@B(x) = A(B(x))), overloaded by
@
.ListOp default combo function i.e. lambda x: x.
Evaluate Equality between Operators, overloaded by
==
.Evaluate the Operator's underlying function, either on a binary string or another Operator.
Return an
OperatorBase
equivalent to an exponentiation of self * i, e^(i*op).Return a
MatrixOp
equivalent to log(H)/i for this operator H.Returns the scalar multiplication of the Operator, overloaded by
*
, including support for Terra'sParameters
, which can be bound to values later (viabind_parameters
).Permute the qubits of the operator.
Return Operator composed with self multiple times, overloaded by
**
.Return a set of strings describing the primitives contained in the Operator.
Try collapsing the Operator structure, usually after some type of conversion, e.g.
Return tensor product between self and other, overloaded by
^
.Return tensor product with self multiple times, overloaded by
^
.Returns an equivalent Operator composed of only QuantumCircuitbased primitives, such as
CircuitOp
andCircuitStateFn
.Return NumPy representation of the Operator.
Returns an equivalent Operator composed of only NumPybased primitives, such as
MatrixOp
andVectorStateFn
.Returns an equivalent Operator composed of only Paulibased primitives, such as
PauliOp
.Returns SciPy sparse matrix representation of the Operator.
Apply the convert_fn to each node in the oplist.
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.

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 inoplist
. Return type
Callable
 Returns
The combination function.

distributive
¶ Indicates whether the ListOp or subclass is distributive under composition. ListOp and SummedOp are, meaning that (opv @ op) = (opv[0] @ op + opv[1] @ op) (using plus for SummedOp, list for ListOp, etc.), while ComposedOp and TensoredOp do not behave this way.
 Return type
bool
 Returns
A bool indicating whether the ListOp is distributive under composition.

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