219 lines
11 KiB
Plaintext
219 lines
11 KiB
Plaintext
---
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title: ParameterExpression
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description: API reference for qiskit.circuit.ParameterExpression
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.circuit.ParameterExpression
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---
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# qiskit.circuit.ParameterExpression
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<Class id="qiskit.circuit.ParameterExpression" isDedicatedPage={true} github="https://github.com/qiskit/qiskit/tree/stable/0.17/qiskit/circuit/parameterexpression.py" signature="ParameterExpression(symbol_map, expr)" modifiers="class">
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ParameterExpression class to enable creating expressions of Parameters.
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Create a new [`ParameterExpression`](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression").
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Not intended to be called directly, but to be instantiated via operations on other [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") or [`ParameterExpression`](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") objects.
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**Parameters**
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* **symbol\_map** (*Dict\[*[*Parameter*](qiskit.circuit.Parameter "qiskit.circuit.Parameter")*, \[*[*ParameterExpression*](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression")*, float, or int]]*) – Mapping of [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") instances to the `sympy.Symbol` serving as their placeholder in expr.
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* **expr** (*sympy.Expr*) – Expression of `sympy.Symbol` s.
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### \_\_init\_\_
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<Function id="qiskit.circuit.ParameterExpression.__init__" signature="__init__(symbol_map, expr)">
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Create a new [`ParameterExpression`](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression").
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Not intended to be called directly, but to be instantiated via operations on other [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") or [`ParameterExpression`](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression") objects.
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**Parameters**
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* **symbol\_map** (*Dict\[*[*Parameter*](qiskit.circuit.Parameter "qiskit.circuit.Parameter")*, \[*[*ParameterExpression*](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression")*, float, or int]]*) – Mapping of [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") instances to the `sympy.Symbol` serving as their placeholder in expr.
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* **expr** (*sympy.Expr*) – Expression of `sympy.Symbol` s.
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</Function>
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## Methods
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| | |
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| --------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- |
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| [`__init__`](#qiskit.circuit.ParameterExpression.__init__ "qiskit.circuit.ParameterExpression.__init__")(symbol\_map, expr) | Create a new [`ParameterExpression`](#qiskit.circuit.ParameterExpression "qiskit.circuit.ParameterExpression"). |
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| [`arccos`](#qiskit.circuit.ParameterExpression.arccos "qiskit.circuit.ParameterExpression.arccos")() | Arccos of a ParameterExpression |
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| [`arcsin`](#qiskit.circuit.ParameterExpression.arcsin "qiskit.circuit.ParameterExpression.arcsin")() | Arcsin of a ParameterExpression |
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| [`arctan`](#qiskit.circuit.ParameterExpression.arctan "qiskit.circuit.ParameterExpression.arctan")() | Arctan of a ParameterExpression |
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| [`assign`](#qiskit.circuit.ParameterExpression.assign "qiskit.circuit.ParameterExpression.assign")(parameter, value) | Assign one parameter to a value, which can either be numeric or another parameter expression. |
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| [`bind`](#qiskit.circuit.ParameterExpression.bind "qiskit.circuit.ParameterExpression.bind")(parameter\_values) | Binds the provided set of parameters to their corresponding values. |
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| [`conjugate`](#qiskit.circuit.ParameterExpression.conjugate "qiskit.circuit.ParameterExpression.conjugate")() | Return the conjugate. |
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| [`cos`](#qiskit.circuit.ParameterExpression.cos "qiskit.circuit.ParameterExpression.cos")() | Cosine of a ParameterExpression |
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| [`exp`](#qiskit.circuit.ParameterExpression.exp "qiskit.circuit.ParameterExpression.exp")() | Exponential of a ParameterExpression |
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| [`gradient`](#qiskit.circuit.ParameterExpression.gradient "qiskit.circuit.ParameterExpression.gradient")(param) | Get the derivative of a parameter expression w\.r.t. |
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| [`log`](#qiskit.circuit.ParameterExpression.log "qiskit.circuit.ParameterExpression.log")() | Logarithm of a ParameterExpression |
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| [`sin`](#qiskit.circuit.ParameterExpression.sin "qiskit.circuit.ParameterExpression.sin")() | Sine of a ParameterExpression |
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| [`subs`](#qiskit.circuit.ParameterExpression.subs "qiskit.circuit.ParameterExpression.subs")(parameter\_map) | Returns a new Expression with replacement Parameters. |
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| [`tan`](#qiskit.circuit.ParameterExpression.tan "qiskit.circuit.ParameterExpression.tan")() | Tangent of a ParameterExpression |
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## Attributes
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| -------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------- |
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| [`parameters`](#qiskit.circuit.ParameterExpression.parameters "qiskit.circuit.ParameterExpression.parameters") | Returns a set of the unbound Parameters in the expression. |
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### arccos
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<Function id="qiskit.circuit.ParameterExpression.arccos" signature="arccos()">
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Arccos of a ParameterExpression
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</Function>
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### arcsin
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<Function id="qiskit.circuit.ParameterExpression.arcsin" signature="arcsin()">
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Arcsin of a ParameterExpression
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</Function>
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### arctan
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<Function id="qiskit.circuit.ParameterExpression.arctan" signature="arctan()">
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Arctan of a ParameterExpression
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</Function>
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### assign
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<Function id="qiskit.circuit.ParameterExpression.assign" signature="assign(parameter, value)">
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Assign one parameter to a value, which can either be numeric or another parameter expression.
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**Parameters**
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* **parameter** ([*Parameter*](qiskit.circuit.Parameter "qiskit.circuit.Parameter")) – A parameter in this expression whose value will be updated.
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* **value** (`Union`\[`ParameterExpression`, `float`, `int`]) – The new value to bind to.
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**Return type**
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`ParameterExpression`
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**Returns**
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A new expression parameterized by any parameters which were not bound by assignment.
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</Function>
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### bind
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<Function id="qiskit.circuit.ParameterExpression.bind" signature="bind(parameter_values)">
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Binds the provided set of parameters to their corresponding values.
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**Parameters**
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**parameter\_values** (`Dict`) – Mapping of Parameter instances to the numeric value to which they will be bound.
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**Raises**
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* **CircuitError** –
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* If parameter\_values contains Parameters outside those in self. - If a non-numeric value is passed in parameter\_values.
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* **ZeroDivisionError** –
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* If binding the provided values requires division by zero.
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**Return type**
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`ParameterExpression`
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**Returns**
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A new expression parameterized by any parameters which were not bound by parameter\_values.
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</Function>
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### conjugate
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<Function id="qiskit.circuit.ParameterExpression.conjugate" signature="conjugate()">
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Return the conjugate.
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**Return type**
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`ParameterExpression`
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</Function>
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### cos
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<Function id="qiskit.circuit.ParameterExpression.cos" signature="cos()">
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Cosine of a ParameterExpression
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</Function>
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### exp
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<Function id="qiskit.circuit.ParameterExpression.exp" signature="exp()">
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Exponential of a ParameterExpression
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</Function>
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### gradient
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<Function id="qiskit.circuit.ParameterExpression.gradient" signature="gradient(param)">
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Get the derivative of a parameter expression w\.r.t. a specified parameter expression.
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**Parameters**
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**param** ([*Parameter*](qiskit.circuit.Parameter "qiskit.circuit.Parameter")) – Parameter w\.r.t. which we want to take the derivative
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**Return type**
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`Union`\[`ParameterExpression`, `float`]
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**Returns**
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ParameterExpression representing the gradient of param\_expr w\.r.t. param
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</Function>
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### log
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<Function id="qiskit.circuit.ParameterExpression.log" signature="log()">
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Logarithm of a ParameterExpression
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</Function>
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### parameters
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<Attribute id="qiskit.circuit.ParameterExpression.parameters">
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Returns a set of the unbound Parameters in the expression.
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**Return type**
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`Set`
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</Attribute>
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### sin
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<Function id="qiskit.circuit.ParameterExpression.sin" signature="sin()">
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Sine of a ParameterExpression
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</Function>
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### subs
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<Function id="qiskit.circuit.ParameterExpression.subs" signature="subs(parameter_map)">
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Returns a new Expression with replacement Parameters.
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**Parameters**
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**parameter\_map** (`Dict`) – Mapping from Parameters in self to the ParameterExpression instances with which they should be replaced.
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**Raises**
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**CircuitError** –
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* If parameter\_map contains Parameters outside those in self. - If the replacement Parameters in parameter\_map would result in a name conflict in the generated expression.
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**Return type**
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`ParameterExpression`
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**Returns**
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A new expression with the specified parameters replaced.
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</Function>
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### tan
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<Function id="qiskit.circuit.ParameterExpression.tan" signature="tan()">
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Tangent of a ParameterExpression
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</Function>
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</Class>
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