# This code is part of Qiskit.
#
# (C) Copyright IBM 2020.
#
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
#
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
"""
Implementation of the abstract class UCPauliRotGate for uniformly controlled
(also called multiplexed) single-qubit rotations around the X-axes
(i.e., uniformly controlled R_x rotations).
These gates can have several control qubits and a single target qubit.
If the k control qubits are in the state ket(i) (in the computational bases),
a single-qubit rotation R_x(a_i) is applied to the target qubit.
"""
import math
from typing import List, Sequence
from qiskit.circuit.quantumcircuit import QuantumCircuit, QubitSpecifier
from qiskit.circuit.quantumregister import QuantumRegister
from qiskit.exceptions import QiskitError
from qiskit.extensions.quantum_initializer.uc_pauli_rot import UCPauliRotGate
[documentos]class UCRXGate(UCPauliRotGate):
"""
Uniformly controlled rotations (also called multiplexed rotations).
The decomposition is based on
'Synthesis of Quantum Logic Circuits' by V. Shende et al.
(https://arxiv.org/pdf/quant-ph/0406176.pdf)
"""
def __init__(self, angle_list):
super().__init__(angle_list, "X")
def ucrx(
self, angle_list: List[float], q_controls: Sequence[QubitSpecifier], q_target: QubitSpecifier
):
r"""Attach a uniformly controlled (also called multiplexed) Rx rotation gate to a circuit.
The decomposition is base on https://arxiv.org/pdf/quant-ph/0406176.pdf by Shende et al.
Args:
angle_list (List[float]): list of (real) rotation angles :math:`[a_0,...,a_{2^k-1}]`
q_controls (Sequence[QubitSpecifier]): list of k control qubits
(or empty list if no controls). The control qubits are ordered according to their
significance in increasing order: For example if ``q_controls=[q[0],q[1]]``
(with ``q = QuantumRegister(2)``), the rotation ``Rx(a_0)`` is performed if ``q[0]``
and ``q[1]`` are in the state zero, the rotation ``Rx(a_1)`` is performed if ``q[0]``
is in the state one and ``q[1]`` is in the state zero, and so on
q_target (QubitSpecifier): target qubit, where we act on with
the single-qubit rotation gates
Returns:
QuantumCircuit: the uniformly controlled rotation gate is attached to the circuit.
Raises:
QiskitError: if the list number of control qubits does not correspond to the provided
number of single-qubit unitaries; if an input is of the wrong type
"""
if isinstance(q_controls, QuantumRegister):
q_controls = q_controls[:]
if isinstance(q_target, QuantumRegister):
q_target = q_target[:]
if len(q_target) == 1:
q_target = q_target[0]
else:
raise QiskitError(
"The target qubit is a QuantumRegister containing more than one qubit."
)
# Check if q_controls has type "list"
if not isinstance(angle_list, list):
raise QiskitError("The angles must be provided as a list.")
num_contr = math.log2(len(angle_list))
if num_contr < 0 or not num_contr.is_integer():
raise QiskitError(
"The number of controlled rotation gates is not a non-negative power of 2."
)
# Check if number of control qubits does correspond to the number of rotations
if num_contr != len(q_controls):
raise QiskitError(
"Number of controlled rotations does not correspond to the number of control-qubits."
)
return self.append(UCRXGate(angle_list), [q_target] + q_controls, [])
QuantumCircuit.ucrx = ucrx