Port synth_permutation_depth_lnn_kms to Rust (Qiskit#12746)

* added functionality for porting

* updated functionality

* formatting

* lint changes

* resolved error

* updated docstring

* formatting

* formatting

crates/accelerate/src/synthesis/permutation/mod.rs

@@ -82,11 +82,44 @@ fn _synth_permutation_acg(py: Python, pattern: PyArrayLike1<i64>) -> PyResult<Ci
     )
 }
 
+/// Synthesize a permutation circuit for a linear nearest-neighbor
+/// architecture using the Kutin, Moulton, Smithline method.
+#[pyfunction]
+#[pyo3(signature = (pattern))]
+pub fn _synth_permutation_depth_lnn_kms(
+    py: Python,
+    pattern: PyArrayLike1<i64>,
+) -> PyResult<CircuitData> {
+    let mut inverted = utils::invert(&pattern.as_array());
+    let mut view = inverted.view_mut();
+    let num_qubits = view.len();
+    let mut swap_layers: Vec<(usize, usize)> = Vec::new();
+
+    for i in 0..num_qubits {
+        let swap_layer: Vec<(usize, usize)> = utils::create_swap_layer(&mut view, i % 2);
+        swap_layers.extend(swap_layer);
+    }
+
+    CircuitData::from_standard_gates(
+        py,
+        num_qubits as u32,
+        swap_layers.iter().map(|(i, j)| {
+            (
+                StandardGate::SwapGate,
+                smallvec![],
+                smallvec![Qubit(*i as u32), Qubit(*j as u32)],
+            )
+        }),
+        Param::Float(0.0),
+    )
+}
+
 #[pymodule]
 pub fn permutation(m: &Bound<PyModule>) -> PyResult<()> {
     m.add_function(wrap_pyfunction!(_validate_permutation, m)?)?;
     m.add_function(wrap_pyfunction!(_inverse_pattern, m)?)?;
     m.add_function(wrap_pyfunction!(_synth_permutation_basic, m)?)?;
     m.add_function(wrap_pyfunction!(_synth_permutation_acg, m)?)?;
+    m.add_function(wrap_pyfunction!(_synth_permutation_depth_lnn_kms, m)?)?;
     Ok(())
 }

crates/accelerate/src/synthesis/permutation/utils.rs

@@ -10,6 +10,7 @@
 // copyright notice, and modified files need to carry a notice indicating
 // that they have been altered from the originals.
 
+use ndarray::ArrayViewMut1;
 use ndarray::{Array1, ArrayView1};
 use pyo3::exceptions::PyValueError;
 use pyo3::prelude::*;
@@ -144,3 +145,22 @@ pub fn decompose_cycles(cycles: &Vec<Vec<usize>>) -> Vec<(usize, usize)> {
 
     swaps
 }
+
+/// Implements a single swap layer, consisting of conditional swaps between each
+/// neighboring couple. The starting_point is the first qubit to use (either 0 or 1
+/// for even or odd layers respectively). Mutates the permutation pattern ``pattern``.
+pub fn create_swap_layer(
+    pattern: &mut ArrayViewMut1<usize>,
+    starting_point: usize,
+) -> Vec<(usize, usize)> {
+    let num_qubits = pattern.len();
+    let mut gates = Vec::new();
+
+    for j in (starting_point..num_qubits - 1).step_by(2) {
+        if pattern[j] > pattern[j + 1] {
+            gates.push((j, j + 1));
+            pattern.swap(j, j + 1);
+        }
+    }
+    gates
+}

qiskit/synthesis/permutation/permutation_lnn.py

@@ -15,7 +15,7 @@
 from __future__ import annotations
 import numpy as np
 from qiskit.circuit.quantumcircuit import QuantumCircuit
-from .permutation_utils import _inverse_pattern
+from qiskit._accelerate.synthesis.permutation import _synth_permutation_depth_lnn_kms
 
 
 def synth_permutation_depth_lnn_kms(pattern: list[int] | np.ndarray[int]) -> QuantumCircuit:
@@ -49,26 +49,4 @@ def synth_permutation_depth_lnn_kms(pattern: list[int] | np.ndarray[int]) -> Qua
     # In the permutation synthesis code below the notation is opposite:
     # [2, 4, 3, 0, 1] means that 0 maps to 2, 1 to 3, 2 to 3, 3 to 0, and 4 to 1.
     # This is why we invert the pattern.
-    cur_pattern = _inverse_pattern(pattern)
-
-    num_qubits = len(cur_pattern)
-    qc = QuantumCircuit(num_qubits)
-
-    # add conditional odd-even swap layers
-    for i in range(num_qubits):
-        _create_swap_layer(qc, cur_pattern, i % 2)
-
-    return qc
-
-
-def _create_swap_layer(qc, pattern, starting_point):
-    """Implements a single swap layer, consisting of conditional swaps between each
-    neighboring couple. The starting_point is the first qubit to use (either 0 or 1
-    for even or odd layers respectively). Mutates both the quantum circuit ``qc``
-    and the permutation pattern ``pattern``.
-    """
-    num_qubits = len(pattern)
-    for j in range(starting_point, num_qubits - 1, 2):
-        if pattern[j] > pattern[j + 1]:
-            qc.swap(j, j + 1)
-            pattern[j], pattern[j + 1] = pattern[j + 1], pattern[j]
+    return QuantumCircuit._from_circuit_data(_synth_permutation_depth_lnn_kms(pattern))

releasenotes/notes/synth_permutation_depth_lnn_kms-c444f3a363f3a903.yaml

@@ -0,0 +1,4 @@
+---
+features_synthesis:
+  - |
+    Port :func:`.synth_permutation_depth_lnn_kms`, used to synthesize permutations for linear connectivity, to Rust.