Parameter
class qiskit.circuit.Parameter(name, *, uuid=None)
Bases: ParameterExpression
Parameter Class for variable parameters.
A parameter is a variable value that is not required to be fixed at circuit definition.
Examples
Construct a variable-rotation X gate using circuit parameters.
from qiskit.circuit import QuantumCircuit, Parameter
# create the parameter
phi = Parameter('phi')
qc = QuantumCircuit(1)
# parameterize the rotation
qc.rx(phi, 0)
qc.draw('mpl')
# bind the parameters after circuit to create a bound circuit
bc = qc.assign_parameters({phi: 3.14})
bc.measure_all()
bc.draw('mpl')
Create a new named Parameter.
Parameters
- name (str) – name of the
Parameter, used for visual representation. This can be any unicode string, e.g. “ϕ”. - uuid (UUID | None) – For advanced usage only. Override the UUID of this parameter, in order to make it compare equal to some other parameter object. By default, two parameters with the same name do not compare equal to help catch shadowing bugs when two circuits containing the same named parameters are spurious combined. Setting the
uuidfield when creating two parameters to the same thing (along with the same name) allows them to be equal. This is useful during serialization and deserialization.
Attributes
name
Returns the name of the Parameter.
parameters
Returns a set of the unbound Parameters in the expression.
Methods
abs
abs()
Absolute of a ParameterExpression
arccos
arccos()
Arccos of a ParameterExpression
arcsin
arcsin()
Arcsin of a ParameterExpression
arctan
arctan()
Arctan of a ParameterExpression
assign
assign(parameter, value)
Assign one parameter to a value, which can either be numeric or another parameter expression.
Parameters
- parameter (Parameter) – A parameter in this expression whose value will be updated.
- value – The new value to bind to.
Returns
A new expression parameterized by any parameters which were not bound by assignment.
bind
bind(parameter_values, allow_unknown_parameters=False)
Binds the provided set of parameters to their corresponding values.
Parameters
- parameter_values (dict) – Mapping of Parameter instances to the numeric value to which they will be bound.
- allow_unknown_parameters (bool) – If
False, raises an error ifparameter_valuescontains Parameters in the keys outside those present in the expression. IfTrue, any such parameters are simply ignored.
Raises
-
- If parameter_values contains Parameters outside those in self. - If a non-numeric value is passed in parameter_values.
-
- If binding the provided values requires division by zero.
Returns
A new expression parameterized by any parameters which were not bound by parameter_values.
Return type
conjugate
cos
cos()
Cosine of a ParameterExpression
exp
exp()
Exponential of a ParameterExpression
gradient
gradient(param)
Get the derivative of a parameter expression w.r.t. a specified parameter expression.
Parameters
param (Parameter) – Parameter w.r.t. which we want to take the derivative
Returns
ParameterExpression representing the gradient of param_expr w.r.t. param or complex or float number
Return type
is_real
is_real()
Return whether the expression is real
log
log()
Logarithm of a ParameterExpression
sign
sign()
Sign of a ParameterExpression
sin
sin()
Sine of a ParameterExpression
subs
subs(parameter_map, allow_unknown_parameters=False)
Substitute self with the corresponding parameter in parameter_map.
sympify
sympify()
Return symbolic expression as a raw Sympy or Symengine object.
Symengine is used preferentially; if both are available, the result will always be a symengine object. Symengine is a separate library but has integration with Sympy.
This is for interoperability only. Qiskit will not accept or work with raw Sympy or Symegine expressions in its parameters, because they do not contain the tracking information used in circuit-parameter binding and assignment.
tan
tan()
Tangent of a ParameterExpression