Converters (qiskit.opflow.converters
)¶
Converters are objects which manipulate Operators, usually traversing an Operator to
change certain subOperators into a desired representation. Often the converted Operator is
isomorphic or approximate to the original Operator in some way, but not always. For example,
a converter may accept CircuitOp
and return a
SummedOp
of
PauliOp
’s representing the
circuit unitary. Converters may not have polynomial space or time scaling in their operations.
On the contrary, many converters, such as a
MatrixExpectation
or
MatrixEvolution
,
which convert PauliOp
’s to
MatrixOp
’s internally, will require time or space
exponential in the number of qubits unless a clever trick is known
(such as the use of sparse matrices).
Note
Not all converters are in this module, as expectations
and evolutions
are also converters.
Converter Base Class¶
The converter base class simply enforces the presence of a convert()
method.
Converters take an Operator and return a new Operator, generally isomorphic in some way with the first, but with certain desired properties. 
Converters¶
In addition to the base class, directory holds a few miscellaneous converters which are used frequently around the Operator flow.
The CircuitSampler traverses an Operator and converts any CircuitStateFns into approximations of the state function by a DictStateFn or VectorStateFn using a quantum backend. 

The AbelianGrouper converts SummedOps into a sum of Abelian sums. 

Converts 

Converter for changing Paulis into other bases. 

Two qubit reduction converter which eliminates the central and last qubit in a list of Pauli that has diagonal operators (Z,I) at those positions. 