-
Notifications
You must be signed in to change notification settings - Fork 2.3k
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
QFT circuit synthesis for linear nearest neighbor connectivity (#11236)
* add basic code to synthesize QFT circuit for linear architecture * replace cp and swap by 3 cx gates and p gates * add do_swaps option * add approximation_degree option * update test: equal instead of equiv * add docstrings * add release notes * fix approximation_degree code. updates following review * updates following review * minor updates follwing review
- Loading branch information
1 parent
cc6fa8f
commit 523ea74
Showing
5 changed files
with
163 additions
and
0 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,15 @@ | ||
# This code is part of Qiskit. | ||
# | ||
# (C) Copyright IBM 2023. | ||
# | ||
# 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. | ||
|
||
"""Module containing stabilizer QFT circuit synthesis.""" | ||
|
||
from .qft_decompose_lnn import synth_qft_line |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,74 @@ | ||
# This code is part of Qiskit. | ||
# | ||
# (C) Copyright IBM 2023. | ||
# | ||
# 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. | ||
""" | ||
Circuit synthesis for a QFT circuit. | ||
""" | ||
|
||
import numpy as np | ||
from qiskit.circuit import QuantumCircuit | ||
from qiskit.synthesis.linear_phase.cz_depth_lnn import _append_cx_stage1, _append_cx_stage2 | ||
|
||
|
||
def synth_qft_line( | ||
num_qubits: int, do_swaps: bool = True, approximation_degree: int = 0 | ||
) -> QuantumCircuit: | ||
"""Synthesis of a QFT circuit for a linear nearest neighbor connectivity. | ||
Based on Fig 2.b in Fowler et al. [1]. | ||
Note that this method *reverts* the order of qubits in the circuit, | ||
compared to the original :class:`.QFT` code. | ||
Hence, the default value of the ``do_swaps`` parameter is ``True`` | ||
since it produces a circuit with fewer CX gates. | ||
Args: | ||
num_qubits: The number of qubits on which the QFT acts. | ||
approximation_degree: The degree of approximation (0 for no approximation). | ||
do_swaps: Whether to include the final swaps in the QFT. | ||
Return: | ||
A circuit implementation of the QFT circuit. | ||
Reference: | ||
1. A. G. Fowler, S. J. Devitt, and L. C. L. Hollenberg, | ||
*Implementation of Shor's algorithm on a linear nearest neighbour qubit array*, | ||
Quantum Info. Comput. 4, 4 (July 2004), 237–251. | ||
`arXiv:quant-ph/0402196 [quant-ph] <https://arxiv.org/abs/quant-ph/0402196>`_ | ||
""" | ||
|
||
qc = QuantumCircuit(num_qubits) | ||
|
||
for i in range(num_qubits): | ||
qc.h(num_qubits - 1) | ||
|
||
for j in range(i, num_qubits - 1): | ||
if j - i + 2 < num_qubits - approximation_degree + 1: | ||
qc.p(np.pi / 2 ** (j - i + 2), num_qubits - j + i - 1) | ||
qc.cx(num_qubits - j + i - 1, num_qubits - j + i - 2) | ||
qc.p(-np.pi / 2 ** (j - i + 2), num_qubits - j + i - 2) | ||
qc.cx(num_qubits - j + i - 2, num_qubits - j + i - 1) | ||
qc.cx(num_qubits - j + i - 1, num_qubits - j + i - 2) | ||
qc.p(np.pi / 2 ** (j - i + 2), num_qubits - j + i - 1) | ||
else: | ||
qc.cx(num_qubits - j + i - 1, num_qubits - j + i - 2) | ||
qc.cx(num_qubits - j + i - 2, num_qubits - j + i - 1) | ||
qc.cx(num_qubits - j + i - 1, num_qubits - j + i - 2) | ||
|
||
if not do_swaps: | ||
# Add a reversal network for LNN connectivity in depth 2*n+2, | ||
# based on Kutin at al., https://arxiv.org/abs/quant-ph/0701194, Section 5. | ||
for _ in range((num_qubits + 1) // 2): | ||
qc = _append_cx_stage1(qc, num_qubits) | ||
qc = _append_cx_stage2(qc, num_qubits) | ||
if (num_qubits % 2) == 0: | ||
qc = _append_cx_stage1(qc, num_qubits) | ||
|
||
return qc |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,6 @@ | ||
--- | ||
features: | ||
- | | ||
Add a new synthesis method :func:`.synth_qft_line` of a QFT circuit | ||
for linear nearest neighbor connectivity, which significantly reduces | ||
the number of SWAPs for large numbers of qubits compared to SABRE. |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,62 @@ | ||
# This code is part of Qiskit. | ||
# | ||
# (C) Copyright IBM 2023. | ||
# | ||
# 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. | ||
|
||
"""Tests for QFT synthesis methods.""" | ||
|
||
|
||
import unittest | ||
from test import combine | ||
from ddt import ddt | ||
|
||
from qiskit.test import QiskitTestCase | ||
from qiskit.circuit.library import QFT | ||
from qiskit.synthesis.qft import synth_qft_line | ||
from qiskit.quantum_info import Operator | ||
|
||
from qiskit.synthesis.linear.linear_circuits_utils import check_lnn_connectivity | ||
|
||
|
||
@ddt | ||
class TestQFTLNN(QiskitTestCase): | ||
"""Tests for QFT synthesis functions.""" | ||
|
||
@combine(num_qubits=[2, 3, 4, 5, 6, 7, 8], do_swaps=[True, False]) | ||
def test_qft_lnn(self, num_qubits, do_swaps): | ||
"""Assert that the original and synthesized QFT circuits are the same.""" | ||
qft_circ = QFT(num_qubits, do_swaps=do_swaps) | ||
qft_lnn = synth_qft_line(num_qubits, do_swaps=do_swaps) | ||
|
||
with self.subTest(msg="original and synthesized QFT circuits are not the same"): | ||
self.assertEqual(Operator(qft_circ), Operator(qft_lnn)) | ||
|
||
# Check that the output circuit has LNN connectivity | ||
with self.subTest(msg="synthesized QFT circuit do not have LNN connectivity"): | ||
self.assertTrue(check_lnn_connectivity(qft_lnn)) | ||
|
||
@combine(num_qubits=[5, 6, 7, 8], do_swaps=[True, False], approximation_degree=[2, 3]) | ||
def test_qft_lnn_approximated(self, num_qubits, do_swaps, approximation_degree): | ||
"""Assert that the original and synthesized QFT circuits are the same with approximation.""" | ||
qft_circ = QFT(num_qubits, do_swaps=do_swaps, approximation_degree=approximation_degree) | ||
qft_lnn = synth_qft_line( | ||
num_qubits, do_swaps=do_swaps, approximation_degree=approximation_degree | ||
) | ||
|
||
with self.subTest(msg="original and synthesized QFT circuits are not the same"): | ||
self.assertEqual(Operator(qft_circ), Operator(qft_lnn)) | ||
|
||
# Check that the output circuit has LNN connectivity | ||
with self.subTest(msg="synthesized QFT circuit do not have LNN connectivity"): | ||
self.assertTrue(check_lnn_connectivity(qft_lnn)) | ||
|
||
|
||
if __name__ == "__main__": | ||
unittest.main() |