StatePreparation
class qiskit.circuit.library.StatePreparation(params, num_qubits=None, inverse=False, label=None, normalize=False)
Bases: Gate
Complex amplitude state preparation.
Class that implements the (complex amplitude) state preparation of some flexible collection of qubit registers.
Parameters

params (str(opens in a new tab) list(opens in a new tab) int(opens in a new tab) Statevector) –
 Statevector: Statevector to initialize to.
 list: vector of complex amplitudes to initialize to.
 string: 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 $0\rangle$.  int: 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(opens in a new tab)  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 $0\rangle$.

inverse (bool(opens in a new tab)) – if True, the inverse state is constructed.

label (str(opens in a new tab)  None) – An optional label for the gate

normalize (bool(opens in a new tab)) – Whether to normalize an input array to a unit vector.
Raises
QiskitError – num_qubits
parameter used when params
is not an integer
When a Statevector argument is passed the state is prepared using a recursive initialization algorithm, including optimizations, from [1], as well as some additional optimizations including removing zero rotations and double cnots.
References: [1] Shende, Bullock, Markov. Synthesis of Quantum Logic Circuits (2004) [https://arxiv.org/abs/quantph/0406176v5(opens in a new tab)]
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 behavioural 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 parametrised gate with a particular set of parameters for the purposes of distinguishing it in a Target
from the full parametrised 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
The parameters of this Instruction
. Ideally these will be gate angles.
unit
Get the time unit of duration.
Methods
broadcast_arguments
broadcast_arguments(qargs, cargs)
Validation and handling of the arguments and its relationship.
For example, cx([q[0],q[1]], q[2])
means cx(q[0], q[2]); cx(q[1], q[2])
. This method yields the arguments in the right grouping. In the given example:
in: [[q[0],q[1]], q[2]],[]
outs: [q[0], q[2]], []
[q[1], q[2]], []
The general broadcasting rules are:
If len(qargs) == 1:
[q[0], q[1]] > [q[0]],[q[1]]
If len(qargs) == 2:
[[q[0], q[1]], [r[0], r[1]]] > [q[0], r[0]], [q[1], r[1]] [[q[0]], [r[0], r[1]]] > [q[0], r[0]], [q[0], r[1]] [[q[0], q[1]], [r[0]]] > [q[0], r[0]], [q[1], r[0]]
If len(qargs) >= 3:
[q[0], q[1]], [r[0], r[1]], ...] > [q[0], r[0], ...], [q[1], r[1], ...]
Parameters
 qargs – List of quantum bit arguments.
 cargs – List of classical bit arguments.
Returns
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.
inverse
validate_parameter
validate_parameter(parameter)
StatePreparation instruction parameter can be str, int, float, and complex.