qiskit.opflow.state_fns.StateFn¶

class
StateFn
(primitive=None, coeff=1.0, is_measurement=False)[Quellcode]¶ A class for representing state functions and measurements.
State functions are defined to be complex functions over a single binary string (as compared to an operator, which is defined as a function over two binary strings, or a function taking a binary function to another binary function). This function may be called by the eval() method.
Measurements are defined to be functionals over StateFns, taking them to real values. Generally, this real value is interpreted to represent the probability of some classical state (binary string) being observed from a probabilistic or quantum system represented by a StateFn. This leads to the equivalent definition, which is that a measurement m is a function over binary strings producing StateFns, such that the probability of measuring a given binary string b from a system with StateFn f is equal to the inner product between f and m(b).
NOTE: State functions here are not restricted to wave functions, as there is no requirement of normalization.
 Parameter
primitive (
Union
[str
,dict
,Result
,list
,ndarray
,Statevector
,QuantumCircuit
,Instruction
,OperatorBase
,None
]) – The primitive which defines the behavior of the underlying State function.coeff (
Union
[complex
,ParameterExpression
]) – A coefficient by which the state function is multiplied.is_measurement (
bool
) – Whether the StateFn is a measurement operator

__init__
(primitive=None, coeff=1.0, is_measurement=False)[Quellcode]¶  Parameter
primitive (
Union
[str
,dict
,Result
,list
,ndarray
,Statevector
,QuantumCircuit
,Instruction
,OperatorBase
,None
]) – The primitive which defines the behavior of the underlying State function.coeff (
Union
[complex
,ParameterExpression
]) – A coefficient by which the state function is multiplied.is_measurement (
bool
) – Whether the StateFn is a measurement operator
Methods
__init__
([primitive, coeff, is_measurement]) type primitive
Union
[str
,dict
,Result
,list
,ndarray
,Statevector
,QuantumCircuit
,Instruction
,OperatorBase
,None
]
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.
copy
()Return a deep copy of the Operator.
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
^
.Returns a
CircuitOp
equivalent to this Operator.to_density_matrix
([massive])Return matrix representing product of StateFn evaluated on pairs of basis states.
to_matrix
([massive])Return NumPy representation of the Operator.
to_matrix_op
([massive])Return a
VectorStateFn
for thisStateFn
.Return SciPy sparse matrix representation of the 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
A coefficient by which the state function is multiplied.
Return the unique instance id.
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.
Return settings.

add
(other)[Quellcode]¶ Return Operator addition of self and other, overloaded by
+
. Parameter
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). Rückgabetyp
OperatorBase
 Rückgabe
An
OperatorBase
equivalent to the sum of self and other.

adjoint
()[Quellcode]¶ Return a new Operator equal to the Operator’s adjoint (conjugate transpose), overloaded by
~
. For StateFns, this also turns the StateFn into a measurement. Rückgabetyp
OperatorBase
 Rückgabe
An
OperatorBase
equivalent to the adjoint of self.

assign_parameters
(param_dict)[Quellcode]¶ 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. Parameter
param_dict (
dict
) – The dictionary ofParameters
to replace, and values or lists of values by which to replace them. Rückgabetyp
OperatorBase
 Rückgabe
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).
 Rückgabetyp
OperatorBase

property
coeff
¶ A coefficient by which the state function is multiplied.
 Rückgabetyp
Union
[complex
,ParameterExpression
]

compose
(other, permutation=None, front=False)[Quellcode]¶ 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.
 Parameter
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)
.
 Rückgabetyp
OperatorBase
 Rückgabe
An Operator equivalent to the function composition of self and other.
 Verursacht
ValueError – If self is not a measurement, it cannot be composed from the right.

copy
()¶ Return a deep copy of the Operator.
 Rückgabetyp
OperatorBase

equals
(other)[Quellcode]¶ 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. Parameter
other (
OperatorBase
) – TheOperatorBase
to compare to self. Rückgabetyp
bool
 Rückgabe
A bool equal to the equality of self and other.

eval
(front=None)[Quellcode]¶ 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. Parameter
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. Rückgabetyp
Union
[OperatorBase
,complex
] Rückgabe
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
instance_id
¶ Return the unique instance id.
 Rückgabetyp
int

property
is_measurement
¶ Whether the StateFn object is a measurement Operator.
 Rückgabetyp
bool

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

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

. Rückgabetyp
OperatorBase
 Rückgabe
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. Rückgabetyp
int
 Rückgabe
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)[Quellcode]¶ Permute the qubits of the state function.
 Parameter
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]. Rückgabetyp
OperatorBase
 Rückgabe
A new StateFn containing the permuted primitive.

power
(exponent)[Quellcode]¶ Compose with Self Multiple Times, undefined for StateFns.
 Parameter
exponent (
int
) – The number of times to compose self with self. Verursacht
ValueError – This function is not defined for StateFns.
 Rückgabetyp
OperatorBase

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

primitive_strings
()[Quellcode]¶ 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. Rückgabetyp
Set
[str
] Rückgabe
A set of strings describing the primitives contained within the Operator.

reduce
()[Quellcode]¶ 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.
 Rückgabetyp
OperatorBase
 Rückgabe
The reduced
OperatorBase
.

sample
(shots=1024, massive=False, reverse_endianness=False)[Quellcode]¶ Sample the state function as a normalized probability distribution. Returns dict of bitstrings in order of probability, with values being probability.
 Parameter
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.
 Rückgabetyp
Dict
[str
,float
] Rückgabe
A dict containing pairs sampled strings from the State function and sampling frequency divided by shots.

property
settings
¶ Return settings.
 Rückgabetyp
Dict

tensor
(other)[Quellcode]¶ 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.
 Parameter
other (
OperatorBase
) – TheOperatorBase
to tensor product with self. Rückgabetyp
OperatorBase
 Rückgabe
An
OperatorBase
equivalent to the tensor product of self and other.

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

to_circuit_op
()[Quellcode]¶ Returns a
CircuitOp
equivalent to this Operator. Rückgabetyp
OperatorBase

to_density_matrix
(massive=False)[Quellcode]¶ Return matrix representing product of StateFn evaluated on pairs of basis states. Overridden by child classes.
 Parameter
massive (
bool
) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits. Rückgabetyp
ndarray
 Rückgabe
The NumPy array representing the density matrix of the State function.
 Verursacht
ValueError – If massive is set to False, and exponentially large computation is needed.

to_matrix
(massive=False)[Quellcode]¶ 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. Rückgabetyp
ndarray
 Rückgabe
The NumPy
ndarray
equivalent to this Operator.

to_matrix_op
(massive=False)[Quellcode]¶ Return a
VectorStateFn
for thisStateFn
. Parameter
massive (
bool
) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits. Rückgabetyp
OperatorBase
 Rückgabe
A VectorStateFn equivalent to self.

to_spmatrix
()¶ Return SciPy sparse matrix representation of the Operator. Represents the evaluation of the Operator’s underlying function on every combination of basis binary strings.
 Rückgabetyp
spmatrix
 Rückgabe
The SciPy
spmatrix
equivalent to this Operator.

traverse
(convert_fn, coeff=None)[Quellcode]¶ 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. Parameter
convert_fn (
Callable
) – The function to apply to the internal OperatorBase.coeff (
Union
[complex
,ParameterExpression
,None
]) – A coefficient to multiply by after applying convert_fn. If it is None, self.coeff is used instead.
 Rückgabetyp
OperatorBase
 Rückgabe
The converted StateFn.