qiskit.aqua.operators.state_fns.VectorStateFn
class VectorStateFn(primitive=None, coeff=1.0, is_measurement=False)
A class for state functions and measurements which are defined in vector representation, and stored using Terra’s Statevector
class.
Parameters
- primitive (
Union
[list
,ndarray
,Statevector
,None
]) – TheStatevector
, NumPy array, or list, which defines the behavior of the underlying function. - coeff (
Union
[int
,float
,complex
,ParameterExpression
]) – A coefficient multiplying the state function. - is_measurement (
bool
) – Whether the StateFn is a measurement operator
__init__
__init__(primitive=None, coeff=1.0, is_measurement=False)
Parameters
- primitive (
Union
[list
,ndarray
,Statevector
,None
]) – TheStatevector
, NumPy array, or list, which defines the behavior of the underlying function. - coeff (
Union
[int
,float
,complex
,ParameterExpression
]) – A coefficient multiplying the state function. - is_measurement (
bool
) – Whether the StateFn is a measurement operator
Methods
__init__ ([primitive, coeff, is_measurement]) | type primitiveUnion [list , ndarray , Statevector , 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 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 matrix representing product of StateFn evaluated on pairs of basis states. |
to_dict_fn () | Creates the equivalent state function of type DictStateFn. |
to_legacy_op ([massive]) | Attempt to return the Legacy Operator representation of the Operator. |
to_matrix ([massive]) | Return NumPy representation of the Operator. |
to_matrix_op ([massive]) | Return a VectorStateFn for this StateFn . |
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
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
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
OperatorBase
Returns
An OperatorBase
equivalent to the adjoint of self.
assign_parameters
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.
Parameters
param_dict (dict
) – The dictionary of Parameters
to replace, and values or lists of values by which to replace them.
Return type
OperatorBase
Returns
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
bind_parameters(param_dict)
Same as assign_parameters, but maintained for consistency with QuantumCircuit in Terra (which has both assign_parameters and bind_parameters).
Return type
OperatorBase
coeff
A coefficient by which the state function is multiplied.
Return type
Union
[int
, float
, complex
, ParameterExpression
]
compose
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.
Parameters
- 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)
.
Return type
OperatorBase
Returns
An Operator equivalent to the function composition of self and other.
Raises
ValueError – If self is not a measurement, it cannot be composed from the right.
equals
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.
Parameters
other (OperatorBase
) – The OperatorBase
to compare to self.
Return type
bool
Returns
A bool equal to the equality of self and other.
eval
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
, 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
, float
, 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.
is_measurement
Whether the StateFn object is a measurement Operator.
Return type
bool
mul
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
).
Parameters
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.
Return type
OperatorBase
Returns
An OperatorBase
equivalent to product of self and scalar.
neg
neg()
Return the Operator’s negation, effectively just multiplying by -1.0, overloaded by -
.
Return type
OperatorBase
Returns
An OperatorBase
equivalent to the negation of self.
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.
Return type
int
Returns
The number of qubits accepted by the Operator’s underlying function.
parameters
Return a set of Parameter objects contained in the Operator.
permute
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
VectorStateFn
Returns
A new StateFn containing the permuted primitive.
power
power(exponent)
Compose with Self Multiple Times, undefined for StateFns.
Parameters
exponent (int
) – The number of times to compose self with self.
Raises
ValueError – This function is not defined for StateFns.
Return type
OperatorBase
primitive
The primitive which defines the behavior of the underlying State function.
primitive_strings
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.
reduce
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.
Return type
OperatorBase
Returns
The reduced OperatorBase
.
sample
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
Returns
A dict containing pairs sampled strings from the State function and sampling frequency divided by shots.
tensor
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.
tensorpower
tensorpower(other)
Return tensor product with self multiple times, overloaded by ^
.
Parameters
other (int
) – The int number of times to tensor product self with itself via tensorpower
.
Return type
Union
[OperatorBase
, int
]
Returns
An OperatorBase
equivalent to the tensorpower of self by other.
to_circuit_op
to_circuit_op()
Return StateFnCircuit
corresponding to this StateFn.
Return type
OperatorBase
to_density_matrix
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_dict_fn
to_dict_fn()
Creates the equivalent state function of type DictStateFn.
Return type
StateFn
Returns
A new DictStateFn equivalent to self
.
to_legacy_op
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.
Return type
LegacyBaseOperator
Returns
The LegacyBaseOperator
representing this Operator.
Raises
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
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_matrix_op
to_matrix_op(massive=False)
Return a VectorStateFn
for this StateFn
.
Parameters
massive (bool
) – Whether to allow large conversions, e.g. creating a matrix representing over 16 qubits.
Return type
OperatorBase
Returns
A VectorStateFn equivalent to self.
traverse
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.
Parameters
- 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.
Return type
OperatorBase
Returns
The converted StateFn.