qiskit.aqua.operators.state_fns.OperatorStateFn¶

class
OperatorStateFn
(primitive=None, coeff=1.0, is_measurement=False)[source]¶ A class for state functions and measurements which are defined by a density Operator, stored using an
OperatorBase
. Paramètres
primitive (
Optional
[OperatorBase
]) – TheOperatorBase
which defines the behavior of the underlying State function.coeff (
Union
[int
,float
,complex
,ParameterExpression
]) – A coefficient by which to multiply the state functionis_measurement (
bool
) – Whether the StateFn is a measurement operator

__init__
(primitive=None, coeff=1.0, is_measurement=False)[source]¶  Paramètres
primitive (
Optional
[OperatorBase
]) – TheOperatorBase
which defines the behavior of the underlying State function.coeff (
Union
[int
,float
,complex
,ParameterExpression
]) – A coefficient by which to multiply the state functionis_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 oneParameter
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 algebrastyle: 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’sParameters
, which can be bound to values later (viabind_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.
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
^
.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
ENABLE_DEPRECATION
INDENTATION
A coefficient by which the state function is multiplied.
Whether the StateFn object is a measurement Operator.
The number of qubits over which the Operator is defined.
Return a set of Parameter objects contained in the Operator.
The primitive which defines the behavior of the underlying State function.

add
(other)[source]¶ Return Operator addition of self and other, overloaded by
+
. Paramètres
other (
OperatorBase
) – AnOperatorBase
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). Type renvoyé
OperatorBase
 Renvoie
An
OperatorBase
equivalent to the sum of self and other.

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. Type renvoyé
OperatorBase
 Renvoie
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 oneParameter
for another. This method differs from Terra’sassign_parameters
in that it also supports lists of values to assign for a giveParameter
, in which case self will be copied for each parameterization in the binding list(s), and all the copies will be returned in anOpList
. If lists of parameterizations are used, everyParameter
in the param_dict must have the same length list of parameterizations. Paramètres
param_dict (
dict
) – The dictionary ofParameters
to replace, and values or lists of values by which to replace them. Type renvoyé
OperatorBase
 Renvoie
The
OperatorBase
with theParameters
in self replaced by the values orParameters
in param_dict. If param_dict contains parameterization lists, thisOperatorBase
is anOpList
.

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

property
coeff
¶ A coefficient by which the state function is multiplied.
 Type renvoyé
Union
[int
,float
,complex
,ParameterExpression
]

compose
(other, permutation=None, front=False)¶ Composition (Linear algebrastyle: A@B(x) = A(B(x))) is not well defined for states in the binary function model, but is well defined for measurements.
 Paramètres
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, returnother.compose(self)
.
 Type renvoyé
OperatorBase
 Renvoie
An Operator equivalent to the function composition of self and other.
 Lève
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. Paramètres
other (
OperatorBase
) – TheOperatorBase
to compare to self. Type renvoyé
bool
 Renvoie
A bool equal to the equality of self and other.

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
front
is None, the matrixrepresentation of the operator is returned. Paramètres
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. Type renvoyé
Union
[OperatorBase
,float
,complex
] Renvoie
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. Iffront
is None, the matrixrepresentation of the operator is returned, which is aMatrixOp
for the operators and aVectorStateFn
for statefunctions. If either self or front contain properListOps
(not ListOp subclasses), the result is an ndimensional 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.
 Type renvoyé
bool

mul
(scalar)¶ Returns the scalar multiplication of the Operator, overloaded by
*
, including support for Terra’sParameters
, which can be bound to values later (viabind_parameters
). Paramètres
scalar (
Union
[int
,float
,complex
,ParameterExpression
]) – The real or complex scalar by which to multiply the Operator, or theParameterExpression
to serve as a placeholder for a scalar factor. Type renvoyé
OperatorBase
 Renvoie
An
OperatorBase
equivalent to product of self and scalar.

neg
()¶ Return the Operator’s negation, effectively just multiplying by 1.0, overloaded by

. Type renvoyé
OperatorBase
 Renvoie
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
, thenop.eval('1' * 5)
will be valid, butop.eval('11')
will not. Type renvoyé
int
 Renvoie
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)[source]¶ Permute the qubits of the state function.
 Paramètres
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]. Type renvoyé
OperatorStateFn
 Renvoie
A new StateFn containing the permuted primitive.

power
(exponent)¶ Compose with Self Multiple Times, undefined for StateFns.
 Paramètres
exponent (
int
) – The number of times to compose self with self. Lève
ValueError – This function is not defined for StateFns.
 Type renvoyé
OperatorBase

property
primitive
¶ The primitive which defines the behavior of the underlying 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. Type renvoyé
Set
[str
] Renvoie
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.
 Type renvoyé
OperatorBase
 Renvoie
The reduced
OperatorBase
.

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.
 Paramètres
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 bigendianness.
 Type renvoyé
dict
 Renvoie
A dict containing pairs sampled strings from the State function and sampling frequency divided by shots.

tensor
(other)[source]¶ Return tensor product between self and other, overloaded by
^
. Note: You must be conscious of Qiskit’s bigendian 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 like0⟩– +⟩–
Because Terra prints circuits and results with qubit 0 at the end of the string or circuit.
 Paramètres
other (
OperatorBase
) – TheOperatorBase
to tensor product with self. Type renvoyé
OperatorBase
 Renvoie
An
OperatorBase
equivalent to the tensor product of self and other.

tensorpower
(other)¶ Return tensor product with self multiple times, overloaded by
^
. Paramètres
other (
int
) – The int number of times to tensor product self with itself viatensorpower
. Type renvoyé
Union
[OperatorBase
,int
] Renvoie
An
OperatorBase
equivalent to the tensorpower of self by other.

to_circuit_op
()[source]¶ 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. Type renvoyé
OperatorBase

to_density_matrix
(massive=False)[source]¶ 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.
 Type renvoyé
ndarray

to_legacy_op
(massive=False)¶ Attempt to return the Legacy Operator representation of the Operator. If self is a
SummedOp
ofPauliOps
, will attempt to convert toWeightedPauliOperator
, and otherwise will simply convert toMatrixOp
and then toMatrixOperator
. The Legacy Operators cannot representStateFns
or properListOps
(meaning not one of theListOp
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. Type renvoyé
LegacyBaseOperator
 Renvoie
The
LegacyBaseOperator
representing this Operator. Lève
TypeError – self is an Operator which cannot be represented by a
LegacyBaseOperator
, such asStateFn
, proper (nonsubclass)ListOp
, or an Operator with an unbound coeff Parameter.

to_matrix
(massive=False)[source]¶ 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.
 Paramètres
massive (
bool
) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits. Renvoie
Vector of state vector
 Type renvoyé
np.ndarray
 Lève
ValueError – Invalid parameters.

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. Paramètres
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.
 Type renvoyé
OperatorBase
 Renvoie
The converted StateFn.