Initialize
class qiskit.circuit.library.Initialize(params, num_qubits=None, normalize=False)
Bases: Instruction
Complex amplitude initialization.
Class that initializes some flexible collection of qubit registers, implemented by calling the StatePreparation
class. Note that Initialize
is an Instruction
and not a Gate
since it contains a reset instruction, which is not unitary.
The initial state is prepared based on the Isometry
synthesis described in [1].
References
 Iten et al., Quantum circuits for isometries (2016). Phys. Rev. A 93, 032318.
Parameters

params (Statevector  Sequence[complex]  str 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()
. 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  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) – 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
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
from the full parametrized gate.
This is often exactly equivalent to type(obj)
, except in the case of singleton instances of standardlibrary instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:
>>> 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.
condition_bits
Get Clbits in condition.
decompositions
Get the decompositions of the instruction from the SessionEquivalenceLibrary.
definition
Return definition in terms of other basic gates.
duration
Get the duration.
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.
Methods
broadcast_arguments
broadcast_arguments(qargs, cargs)
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 – If the input is not valid. For example, the number of arguments does not match the gate expectation.
gates_to_uncompute
gates_to_uncompute()
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