qiskit.aqua.operators.state_fns.OperatorStateFn

class OperatorStateFn(primitive=None, coeff=1.0, is_measurement=False)

A class for state functions and measurements which are defined by a density Operator, stored using an OperatorBase.

Parâmetros

• primitive (Optional[OperatorBase]) – The OperatorBase which defines the behavior of the underlying State function.

• coeff (Union[int, float, complex, ParameterExpression]) – A coefficient by which to multiply the state function

• is_measurement (bool) – Whether the StateFn is a measurement operator

__init__(primitive=None, coeff=1.0, is_measurement=False)

Parâmetros

• primitive (Optional[OperatorBase]) – The OperatorBase which defines the behavior of the underlying State function.

• coeff (Union[int, float, complex, ParameterExpression]) – A coefficient by which to multiply the state function

• is_measurement (bool) – Whether the StateFn is a measurement operator

Methods

__init__([primitive, coeff, is_measurement])	type primitive Optional[OperatorBase]
add(other)	Return Operator addition of self and other, overloaded by +.
adjoint()	Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by ~.
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.
bind_parameters(param_dict)	Same as assign_parameters, but maintained for consistency with QuantumCircuit in Terra (which has both assign_parameters and bind_parameters).
compose(other[, permutation, front])	Composition (Linear algebra-style: A@B(x) = A(B(x))) is not well defined for states in the binary function model, but is well defined for measurements.
equals(other)	Evaluate Equality between Operators, overloaded by ==.
eval([front])	Evaluate the Operator’s underlying function, either on a binary string or another Operator.
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).
neg()	Return the Operator’s negation, effectively just multiplying by -1.0, overloaded by -.
permute(permutation)	Permute the qubits of the state function.
power(exponent)	Compose with Self Multiple Times, undefined for StateFns.
primitive_strings()	Return a set of strings describing the primitives contained in the Operator.
reduce()	Try collapsing the Operator structure, usually after some type of conversion, e.g.
sample([shots, massive, reverse_endianness])	Sample the state function as a normalized probability distribution.
tensor(other)	Return tensor product between self and other, overloaded by ^.
tensorpower(other)	Return tensor product with self multiple times, overloaded by ^.
to_circuit_op()	Return StateFnCircuit corresponding to this StateFn.
to_density_matrix([massive])	Return numpy matrix of density operator, warn if more than 16 qubits to force the user to set massive=True if they want such a large matrix.
to_legacy_op([massive])	Attempt to return the Legacy Operator representation of the Operator.
to_matrix([massive])	Note: this does not return a density matrix, it returns a classical matrix containing the quantum or classical vector representing the evaluation of the state function on each binary basis state.
to_matrix_op([massive])	Return a MatrixOp for this operator.
traverse(convert_fn[, coeff])	Apply the convert_fn to the internal primitive if the primitive is an Operator (as in the case of OperatorStateFn).

Attributes

INDENTATION
coeff	A coefficient by which the state function is multiplied.
is_measurement	Whether the StateFn object is a measurement Operator.
num_qubits	The number of qubits over which the Operator is defined.
parameters	Return a set of Parameter objects contained in the Operator.
primitive	The primitive which defines the behavior of the underlying State function.

add(other)

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

Parâmetros

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).

Tipo de retorno

OperatorBase

Retorna

An OperatorBase equivalent to the sum of self and other.

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.

Tipo de retorno

OperatorBase

Retorna

An OperatorBase equivalent to the adjoint of self.

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. This method differs from Terra’s assign_parameters in that it also supports lists of values to assign for a give Parameter, in which case self will be copied for each parameterization in the binding list(s), and all the copies will be returned in an OpList. If lists of parameterizations are used, every Parameter in the param_dict must have the same length list of parameterizations.

Parâmetros

param_dict (dict) – The dictionary of Parameters to replace, and values or lists of values by which to replace them.

Tipo de retorno

OperatorBase

Retorna

The OperatorBase with the Parameters in self replaced by the values or Parameters in param_dict. If param_dict contains parameterization lists, this OperatorBase is an OpList.

bind_parameters(param_dict)

Same as assign_parameters, but maintained for consistency with QuantumCircuit in Terra (which has both assign_parameters and bind_parameters).

Tipo de retorno

OperatorBase

property coeff

A coefficient by which the state function is multiplied.

Tipo de retorno

Union[int, float, complex, ParameterExpression]

compose(other, permutation=None, front=False)

Composition (Linear algebra-style: A@B(x) = A(B(x))) is not well defined for states in the binary function model, but is well defined for measurements.

Parâmetros

• other (OperatorBase) – The Operator to compose with self.

• permutation (Optional[List[int]]) – List[int] which defines permutation on other operator.

• front (bool) – If front==True, return other.compose(self).

Tipo de retorno

OperatorBase

Retorna

An Operator equivalent to the function composition of self and other.

Levanta

ValueError – If self is not a measurement, it cannot be composed from the right.

equals(other)

Evaluate Equality between Operators, overloaded by ==. Only returns True if self and other are of the same representation (e.g. a DictStateFn and CircuitStateFn will never be equal, even if their vector representations are equal), their underlying primitives are equal (this means for ListOps, OperatorStateFns, or EvolvedOps the equality is evaluated recursively downwards), and their coefficients are equal.

Parâmetros

other (OperatorBase) – The OperatorBase to compare to self.

Tipo de retorno

bool

Retorna

A bool equal to the equality of self and other.

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.

Parâmetros

front (Union[str, dict, ndarray, OperatorBase, None]) – The bitstring, dict of bitstrings (with values being coefficients), or StateFn to evaluated by the Operator’s underlying function, or None.

Tipo de retorno

Union[OperatorBase, float, complex]

Retorna

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.

property is_measurement

Whether the StateFn object is a measurement Operator.

Tipo de retorno

bool

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).

Parâmetros

scalar (Union[int, float, complex, ParameterExpression]) – The real or complex scalar by which to multiply the Operator, or the ParameterExpression to serve as a placeholder for a scalar factor.

Tipo de retorno

OperatorBase

Retorna

An OperatorBase equivalent to product of self and scalar.

neg()

Return the Operator’s negation, effectively just multiplying by -1.0, overloaded by -.

Tipo de retorno

OperatorBase

Retorna

An OperatorBase equivalent to the negation of self.

property num_qubits

The number of qubits over which the Operator is defined. If op.num_qubits == 5, then op.eval('1' * 5) will be valid, but op.eval('11') will not.

Tipo de retorno

int

Retorna

The number of qubits accepted by the Operator’s underlying function.

property parameters

Return a set of Parameter objects contained in the Operator.

permute(permutation)

Permute the qubits of the state function.

Parâmetros

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].

Tipo de retorno

OperatorStateFn

Retorna

A new StateFn containing the permuted primitive.

power(exponent)

Compose with Self Multiple Times, undefined for StateFns.

Parâmetros

exponent (int) – The number of times to compose self with self.

Levanta

ValueError – This function is not defined for StateFns.

Tipo de retorno

OperatorBase

property primitive

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

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.

Tipo de retorno

Set[str]

Retorna

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

reduce()

Try collapsing the Operator structure, usually after some type of conversion, e.g. trying to add Operators in a SummedOp or delete needless IGates in a CircuitOp. If no reduction is available, just returns self.

Tipo de retorno

OperatorBase

Retorna

The reduced OperatorBase.

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.

Parâmetros

• 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.

Tipo de retorno

dict

Retorna

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

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.

Parâmetros

other (OperatorBase) – The OperatorBase to tensor product with self.

Tipo de retorno

OperatorBase

Retorna

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

tensorpower(other)

Return tensor product with self multiple times, overloaded by ^.

Parâmetros

other (int) – The int number of times to tensor product self with itself via tensorpower.

Tipo de retorno

Union[OperatorBase, int]

Retorna

An OperatorBase equivalent to the tensorpower of self by other.

to_circuit_op()

Return StateFnCircuit corresponding to this StateFn. Ignore for now because this is undefined. TODO maybe call to_pauli_op and diagonalize here, but that could be very inefficient, e.g. splitting one Stabilizer measurement into hundreds of 1 qubit Paulis.

Tipo de retorno

OperatorBase

to_density_matrix(massive=False)

Return numpy matrix of density operator, warn if more than 16 qubits to force the user to set massive=True if they want such a large matrix. Generally big methods like this should require the use of a converter, but in this case a convenience method for quick hacking and access to classical tools is appropriate.

Tipo de retorno

ndarray

to_legacy_op(massive=False)

Attempt to return the Legacy Operator representation of the Operator. If self is a SummedOp of PauliOps, will attempt to convert to WeightedPauliOperator, and otherwise will simply convert to MatrixOp and then to MatrixOperator. The Legacy Operators cannot represent StateFns or proper ListOps (meaning not one of the ListOp subclasses), so an error will be thrown if this method is called on such an Operator. Also, Legacy Operators cannot represent unbound Parameter coeffs, so an error will be thrown if any are present in self.

Warn if more than 16 qubits to force having to set massive=True if such a large vector is desired.

Tipo de retorno

LegacyBaseOperator

Retorna

The LegacyBaseOperator representing this Operator.

Levanta

TypeError – self is an Operator which cannot be represented by a LegacyBaseOperator, such as StateFn, proper (non-subclass) ListOp, or an Operator with an unbound coeff Parameter.

to_matrix(massive=False)

Note: this does not return a density matrix, it returns a classical matrix containing the quantum or classical vector representing the evaluation of the state function on each binary basis state. Do not assume this is is a normalized quantum or classical probability vector. If we allowed this to return a density matrix, then we would need to change the definition of composition to be ~Op @ StateFn @ Op for those cases, whereas by this methodology we can ensure that composition always means Op @ StateFn.

Return numpy vector of state vector, warn if more than 16 qubits to force the user to set massive=True if they want such a large vector.

Parâmetros

massive (bool) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits.

Retorna

Vector of state vector

Tipo de retorno

np.ndarray

Levanta

ValueError – Invalid parameters.

to_matrix_op(massive=False)

Return a MatrixOp for this operator.

Tipo de retorno

OperatorBase

traverse(convert_fn, coeff=None)

Apply the convert_fn to the internal primitive if the primitive is an Operator (as in the case of OperatorStateFn). Otherwise do nothing. Used by converters.

Parâmetros

• convert_fn (Callable) – The function to apply to the internal OperatorBase.

• coeff (Union[int, float, complex, ParameterExpression, None]) – A coefficient to multiply by after applying convert_fn. If it is None, self.coeff is used instead.

Tipo de retorno

OperatorBase

Retorna

The converted StateFn.