171 lines
7.7 KiB
Plaintext
171 lines
7.7 KiB
Plaintext
---
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title: Initialize (latest version)
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description: API reference for qiskit.circuit.library.Initialize in the latest version of qiskit
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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.library.Initialize
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---
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# Initialize
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<Class id="qiskit.circuit.library.Initialize" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/data_preparation/initializer.py#L33-L107" signature="qiskit.circuit.library.Initialize(params, num_qubits=None, normalize=False)" modifiers="class">
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Bases: [`Instruction`](qiskit.circuit.Instruction "qiskit.circuit.instruction.Instruction")
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Complex amplitude initialization.
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Class that initializes some flexible collection of qubit registers, implemented by calling the [`StatePreparation`](qiskit.circuit.library.StatePreparation "qiskit.circuit.library.StatePreparation") class. Note that `Initialize` is an [`Instruction`](qiskit.circuit.Instruction "qiskit.circuit.Instruction") and not a [`Gate`](qiskit.circuit.Gate "qiskit.circuit.Gate") since it contains a reset instruction, which is not unitary.
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The initial state is prepared based on the [`Isometry`](qiskit.circuit.library.Isometry "qiskit.circuit.library.Isometry") synthesis described in \[1].
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**References**
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1. Iten et al., Quantum circuits for isometries (2016). [Phys. Rev. A 93, 032318](https://journals.aps.org/pra/abstract/10.1103/PhysRevA.93.032318).
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**Parameters**
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* **params** ([*Statevector*](qiskit.quantum_info.Statevector "qiskit.quantum_info.Statevector") *| Sequence\[*[*complex*](https://docs.python.org/3/library/functions.html#complex "(in Python v3.13)")*] |* [*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)") *|*[*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)")) –
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The state to initialize to, can be either of the following.
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* Statevector or vector of complex amplitudes to initialize to.
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* Labels of basis states of the Pauli eigenstates Z, X, Y. See [`Statevector.from_label()`](qiskit.quantum_info.Statevector#from_label "qiskit.quantum_info.Statevector.from_label"). Notice the order of the labels is reversed with respect to the qubit index to be applied to. Example label ‘01’ initializes the qubit zero to $|1\rangle$ and the qubit one to $|0\rangle$.
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* An integer that is used as a bitmap indicating which qubits to initialize to $|1\rangle$. Example: setting params to 5 would initialize qubit 0 and qubit 2 to $|1\rangle$ and qubit 1 to $|0\rangle$.
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* **num\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int "(in Python v3.13)") *| None*) – This parameter is only used if params is an int. Indicates the total number of qubits in the initialize call. Example: initialize covers 5 qubits and params is 3. This allows qubits 0 and 1 to be initialized to $|1\rangle$ and the remaining 3 qubits to be initialized to $|0\rangle$.
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* **normalize** ([*bool*](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")) – Whether to normalize an input array to a unit vector.
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## Attributes
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### base\_class
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<Attribute id="qiskit.circuit.library.Initialize.base_class">
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Get the base class of this instruction. This is guaranteed to be in the inheritance tree of `self`.
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The “base class” of an instruction is the lowest class in its inheritance tree that the object should be considered entirely compatible with for \_all\_ circuit applications. This typically means that the subclass is defined purely to offer some sort of programmer convenience over the base class, and the base class is the “true” class for a behavioral perspective. In particular, you should *not* override [`base_class`](#qiskit.circuit.library.Initialize.base_class "qiskit.circuit.library.Initialize.base_class") if you are defining a custom version of an instruction that will be implemented differently by hardware, such as an alternative measurement strategy, or a version of a parametrized gate with a particular set of parameters for the purposes of distinguishing it in a [`Target`](qiskit.transpiler.Target "qiskit.transpiler.Target") from the full parametrized gate.
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This is often exactly equivalent to `type(obj)`, except in the case of singleton instances of standard-library instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:
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```python
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>>> isinstance(XGate(), XGate)
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True
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>>> type(XGate()) is XGate
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False
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>>> XGate().base_class is XGate
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True
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```
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In general, you should not rely on the precise class of an instruction; within a given circuit, it is expected that `Instruction.name` should be a more suitable discriminator in most situations.
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</Attribute>
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### condition
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<Attribute id="qiskit.circuit.library.Initialize.condition">
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The classical condition on the instruction.
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</Attribute>
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### condition\_bits
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<Attribute id="qiskit.circuit.library.Initialize.condition_bits">
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Get Clbits in condition.
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</Attribute>
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### decompositions
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<Attribute id="qiskit.circuit.library.Initialize.decompositions">
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Get the decompositions of the instruction from the SessionEquivalenceLibrary.
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</Attribute>
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### definition
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<Attribute id="qiskit.circuit.library.Initialize.definition">
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Return definition in terms of other basic gates.
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</Attribute>
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### duration
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<Attribute id="qiskit.circuit.library.Initialize.duration">
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Get the duration.
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</Attribute>
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### label
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<Attribute id="qiskit.circuit.library.Initialize.label">
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Return instruction label
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</Attribute>
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### mutable
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<Attribute id="qiskit.circuit.library.Initialize.mutable">
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Is this instance is a mutable unique instance or not.
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If this attribute is `False` the gate instance is a shared singleton and is not mutable.
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</Attribute>
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### name
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<Attribute id="qiskit.circuit.library.Initialize.name">
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Return the name.
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</Attribute>
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### num\_clbits
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<Attribute id="qiskit.circuit.library.Initialize.num_clbits">
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Return the number of clbits.
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</Attribute>
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### num\_qubits
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<Attribute id="qiskit.circuit.library.Initialize.num_qubits">
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Return the number of qubits.
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</Attribute>
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### params
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<Attribute id="qiskit.circuit.library.Initialize.params">
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Return initialize params.
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</Attribute>
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### unit
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<Attribute id="qiskit.circuit.library.Initialize.unit">
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Get the time unit of duration.
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</Attribute>
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## Methods
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### broadcast\_arguments
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<Function id="qiskit.circuit.library.Initialize.broadcast_arguments" github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/data_preparation/initializer.py#L106-L107" signature="broadcast_arguments(qargs, cargs)">
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Validation of the arguments.
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**Parameters**
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* **qargs** (*List*) – List of quantum bit arguments.
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* **cargs** (*List*) – List of classical bit arguments.
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**Yields**
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*Tuple(List, List)* – A tuple with single arguments.
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**Raises**
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[**CircuitError**](circuit#qiskit.circuit.CircuitError "qiskit.circuit.CircuitError") – If the input is not valid. For example, the number of arguments does not match the gate expectation.
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</Function>
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### gates\_to\_uncompute
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<Function id="qiskit.circuit.library.Initialize.gates_to_uncompute" github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/data_preparation/initializer.py#L86-L94" signature="gates_to_uncompute()">
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Call to create a circuit with gates that take the desired vector to zero.
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**Returns**
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circuit to take `self.params` vector to $|{00\ldots0}\rangle$
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**Return type**
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[QuantumCircuit](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")
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</Function>
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</Class>
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