StatePreparation

class qiskit.circuit.library.StatePreparation(params, num_qubits=None, inverse=False, label=None, normalize=False)[source]

Bases: Gate

Complex amplitude state preparation.

Class that implements the (complex amplitude) state preparation of some flexible collection of qubit registers.

Parameters:

  • params (str | list | int | 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 | 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) – if True, the inverse state is constructed.

  • label (str | None) – An optional label for the gate

  • normalize (bool) – 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/quant-ph/0406176v5]

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 standard-library 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 instruction params.

unit

Get the time unit of duration.

Methods

broadcast_arguments(qargs, cargs)[source]

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()[source]

Return inverted StatePreparation

validate_parameter(parameter)[source]

StatePreparation instruction parameter can be str, int, float, and complex.