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DictStateFn

DictStateFn(primitive=None, coeff=1.0, is_measurement=False, from_operator=False)

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Bases: qiskit.opflow.state_fns.state_fn.StateFn

A class for state functions and measurements which are defined by a lookup table, stored in a dict.

Parameters

  • primitive (Union[str, dict, Result, None]) – The dict, single bitstring (if defining a basis sate), or Qiskit Result, which defines the behavior of the underlying function.
  • coeff (Union[complex, ParameterExpression]) – A coefficient by which to multiply the state function.
  • is_measurement (bool) – Whether the StateFn is a measurement operator.
  • from_operator (bool) – if True the StateFn is derived from OperatorStateFn. (Default: False)

Raises

TypeError – invalid parameters.


Methods Defined Here

add

DictStateFn.add(other)

Return Operator addition of self and other, overloaded by +.

Parameters

other (OperatorBase) – An OperatorBase with 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).

Return type

OperatorBase

Returns

An OperatorBase equivalent to the sum of self and other.

adjoint

DictStateFn.adjoint()

Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by ~. For StateFns, this also turns the StateFn into a measurement.

Return type

DictStateFn

Returns

An OperatorBase equivalent to the adjoint of self.

eval

DictStateFn.eval(front=None)

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 front is None, the matrix-representation of the operator is returned.

Parameters

front (Union[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.

Return type

Union[OperatorBase, complex]

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. If front is None, the matrix-representation of the operator is returned, which is a MatrixOp for the operators and a VectorStateFn for state-functions. 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.

permute

DictStateFn.permute(permutation)

Permute the qubits of the state function.

Parameters

permutation (List[int]) – A list defining where each qubit should be permuted. The qubit at index j of the circuit should be permuted to position permutation[j].

Return type

DictStateFn

Returns

A new StateFn containing the permuted primitive.

primitive_strings

DictStateFn.primitive_strings()

Return a set of strings describing the primitives contained in the Operator. For example, {'QuantumCircuit', 'Pauli'}. For hierarchical Operators, such as ListOps, this can help illuminate the primitives represented in the various recursive levels, and therefore which conversions can be applied.

Return type

Set[str]

Returns

A set of strings describing the primitives contained within the Operator.

sample

DictStateFn.sample(shots=1024, massive=False, reverse_endianness=False)

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.

Return type

Dict[str, float]

Returns

A dict containing pairs sampled strings from the State function and sampling frequency divided by shots.

tensor

DictStateFn.tensor(other)

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 OperatorBase to tensor product with self.

Return type

OperatorBase

Returns

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

to_circuit_op

DictStateFn.to_circuit_op()

Convert this state function to a CircuitStateFn.

Return type

OperatorBase

to_density_matrix

DictStateFn.to_density_matrix(massive=False)

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.

Return type

ndarray

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.

to_matrix

DictStateFn.to_matrix(massive=False)

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.

to_spmatrix

DictStateFn.to_spmatrix()

Same as to_matrix, but returns csr sparse matrix.

Return type

spmatrix

Returns

CSR sparse matrix representation of the State function.

Raises

ValueError – invalid parameters.

to_spmatrix_op

DictStateFn.to_spmatrix_op()

Convert this state function to a SparseVectorStateFn.

Return type

OperatorBase


Attributes

INDENTATION

= '  '

coeff

A coefficient by which the state function is multiplied.

Return type

Union[complex, ParameterExpression]

instance_id

Return the unique instance id.

Return type

int

is_measurement

Whether the StateFn object is a measurement Operator.

Return type

bool

num_qubits

Return type

int

parameters

primitive

Dict[str, complex]

The primitive which defines the behavior of the underlying State function.

settings

Return settings.

Return type

Dict

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