VectorStateFn¶
- class qiskit.opflow.state_fns.VectorStateFn(*args, **kwargs)[source]¶
Bases:
StateFnDeprecated: A class for state functions and measurements which are defined in vector representation, and stored using Terra’s
Statevectorclass.Deprecated since version 0.24.0: The class
qiskit.opflow.state_fns.vector_state_fn.VectorStateFnis deprecated as of qiskit-terra 0.24.0. It will be removed no earlier than 3 months after the release date. For code migration guidelines, visit https://qisk.it/opflow_migration.- Parameters:
primitive – The
Statevector, NumPy array, or list, which defines the behavior of the underlying function.coeff – A coefficient multiplying the state function.
is_measurement – Whether the StateFn is a measurement operator
Attributes
- INDENTATION = ' '¶
- coeff¶
A coefficient by which the state function is multiplied.
- instance_id¶
Return the unique instance id.
- is_measurement¶
Whether the StateFn object is a measurement Operator.
- num_qubits¶
- parameters¶
- primitive: Statevector¶
The primitive which defines the behavior of the underlying State function.
- settings¶
Return settings.
Methods
- add(other)[source]¶
Return Operator addition of self and other, overloaded by
+.- Parameters:
other (OperatorBase) – An
OperatorBasewith the same number of qubits as self, and in the same ‘Operator’, ‘State function’, or ‘Measurement’ category as self (i.e. the same type of underlying function).- Returns:
An
OperatorBaseequivalent to the sum of self and other.- Return type:
- adjoint()[source]¶
Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by
~. For StateFns, this also turns the StateFn into a measurement.- Returns:
An
OperatorBaseequivalent to the adjoint of self.- Return type:
- eval(front=None)[source]¶
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).If
frontis None, the matrix-representation of the operator is returned.- Parameters:
front (str | Dict[str, complex] | ndarray | OperatorBase | Statevector | None) – The bitstring, dict of bitstrings (with values being coefficients), or StateFn to evaluated by the Operator’s underlying function, or None.
- Returns:
The output of the Operator’s evaluation function. If self is a
StateFn, the result is a float or complex. If self is an Operator (PrimitiveOp, ComposedOp, SummedOp, EvolvedOp,etc.), the result is a StateFn. Iffrontis None, the matrix-representation of the operator is returned, which is aMatrixOpfor the operators and aVectorStateFnfor state-functions. If either self or front contain properListOps(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.- Return type:
- permute(permutation)[source]¶
Permute the qubits of the state function.
- primitive_strings()[source]¶
Return a set of strings describing the primitives contained in the Operator. For example,
{'QuantumCircuit', 'Pauli'}. For hierarchical Operators, such asListOps, this can help illuminate the primitives represented in the various recursive levels, and therefore which conversions can be applied.
- sample(shots=1024, massive=False, reverse_endianness=False)[source]¶
Sample the state function as a normalized probability distribution. Returns dict of bitstrings in order of probability, with values being probability.
- Parameters:
shots (int) – The number of samples to take to approximate the State function.
massive (bool) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits.
reverse_endianness (bool) – Whether to reverse the endianness of the bitstrings in the return dict to match Terra’s big-endianness.
- Returns:
A dict containing pairs sampled strings from the State function and sampling frequency divided by shots.
- Return type:
- tensor(other)[source]¶
Return tensor product between self and other, overloaded by
^. Note: You must be conscious of Qiskit’s big-endian bit printing convention. Meaning, Plus.tensor(Zero) produces a |+⟩ on qubit 0 and a |0⟩ on qubit 1, or |+⟩⨂|0⟩, but would produce a QuantumCircuit like|0⟩– |+⟩–
Because Terra prints circuits and results with qubit 0 at the end of the string or circuit.
- Parameters:
other (OperatorBase) – The
OperatorBaseto tensor product with self.- Returns:
An
OperatorBaseequivalent to the tensor product of self and other.- Return type:
- to_density_matrix(massive=False)[source]¶
Return matrix representing product of StateFn evaluated on pairs of basis states. Overridden by child classes.
- Parameters:
massive (bool) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits.
- Returns:
The NumPy array representing the density matrix of the State function.
- Raises:
ValueError – If massive is set to False, and exponentially large computation is needed.
- Return type:
- to_dict_fn()[source]¶
Creates the equivalent state function of type DictStateFn.
- Returns:
A new DictStateFn equivalent to
self.- Return type:
- to_matrix(massive=False)[source]¶
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=Trueif such a large vector is desired.- Returns:
The NumPy
ndarrayequivalent to this Operator.- Return type: