--- title: Initialize (v1.3) description: API reference for qiskit.circuit.library.Initialize in qiskit v1.3 source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/1.3/qiskit.circuit.library.Initialize --- # Initialize *class* `qiskit.circuit.library.Initialize(params, num_qubits=None, normalize=False)` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/data_preparation/initializer.py#L33-L107) Bases: [`Instruction`](/docs/api/qiskit/1.3/qiskit.circuit.Instruction "qiskit.circuit.instruction.Instruction") Complex amplitude initialization. Class that initializes some flexible collection of qubit registers, implemented by calling the [`StatePreparation`](/docs/api/qiskit/1.3/qiskit.circuit.library.StatePreparation "qiskit.circuit.library.StatePreparation") class. Note that `Initialize` is an [`Instruction`](/docs/api/qiskit/1.3/qiskit.circuit.Instruction "qiskit.circuit.Instruction") and not a [`Gate`](/docs/api/qiskit/1.3/qiskit.circuit.Gate "qiskit.circuit.Gate") since it contains a reset instruction, which is not unitary. The initial state is prepared based on the [`Isometry`](/docs/api/qiskit/1.3/qiskit.circuit.library.Isometry "qiskit.circuit.library.Isometry") synthesis described in \[1]. **References** 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). **Parameters** - **params** ([*Statevector*](/docs/api/qiskit/1.3/qiskit.quantum_info.Statevector "qiskit.quantum_info.Statevector") *| Sequence\[*[*complex*](https://docs.python.org/3/library/functions.html#complex)*] |* [*str*](https://docs.python.org/3/library/stdtypes.html#str) *|*[*int*](https://docs.python.org/3/library/functions.html#int)) – The state to initialize to, can be either of the following. - Statevector or vector of complex amplitudes to initialize to. - Labels of basis states of the Pauli eigenstates Z, X, Y. See [`Statevector.from_label()`](/docs/api/qiskit/1.3/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 $|0\rangle$. - 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 $|0\rangle$. - **num\_qubits** ([*int*](https://docs.python.org/3/library/functions.html#int) *| 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 $|0\rangle$. - **normalize** ([*bool*](https://docs.python.org/3/library/functions.html#bool)) – Whether to normalize an input array to a unit vector. ## Attributes ### base\_class Get the base class of this instruction. This is guaranteed to be in the inheritance tree of `self`. 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`](/docs/api/qiskit/1.3/qiskit.transpiler.Target "qiskit.transpiler.Target") from the full parametrized gate. 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: ```python >>> isinstance(XGate(), XGate) True >>> type(XGate()) is XGate False >>> XGate().base_class is XGate True ``` 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. ### condition The classical condition on the instruction. > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.instruction.Instruction.condition` is deprecated as of qiskit 1.3.0. It will be removed in 2.0.0. ### condition\_bits Get Clbits in condition. > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.instruction.Instruction.condition_bits` is deprecated as of qiskit 1.3.0. It will be removed in 2.0.0. ### decompositions Get the decompositions of the instruction from the SessionEquivalenceLibrary. ### definition Return definition in terms of other basic gates. ### duration Get the duration. > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.instruction.Instruction.duration` is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0. ### label Return instruction label ### mutable Is this instance is a mutable unique instance or not. If this attribute is `False` the gate instance is a shared singleton and is not mutable. ### name Return the name. ### num\_clbits Return the number of clbits. ### num\_qubits Return the number of qubits. ### params Return initialize params. ### unit Get the time unit of duration. > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.instruction.Instruction.unit` is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0. ## Methods ### broadcast\_arguments `broadcast_arguments(qargs, cargs)` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/data_preparation/initializer.py#L106-L107) Validation of the arguments. **Parameters** - **qargs** (*List*) – List of quantum bit arguments. - **cargs** (*List*) – List of classical bit arguments. **Yields** *Tuple(List, List)* – A tuple with single arguments. **Raises** [**CircuitError**](/docs/api/qiskit/1.3/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. ### gates\_to\_uncompute `gates_to_uncompute()` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/data_preparation/initializer.py#L86-L94) Call to create a circuit with gates that take the desired vector to zero. **Returns** circuit to take `self.params` vector to $|{00\ldots0}\rangle$ **Return type** [QuantumCircuit](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")