Port synth_cz_depth_line_mr to Rust

crates/accelerate/src/synthesis/linear/lnn.rs

@@ -0,0 +1,217 @@
+// This code is part of Qiskit.
+//
+// (C) Copyright IBM 2024
+//
+// 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.
+
+use std::iter::once;
+
+use hashbrown::HashMap;
+use itertools::Itertools;
+use ndarray::{Array1, ArrayView2};
+
+use qiskit_circuit::{
+    operations::{Param, StandardGate},
+    Qubit,
+};
+use smallvec::{smallvec, SmallVec};
+
+// A sequence of Lnn gates
+// Represents the return type for Lnn Synthesis algorithms
+type LnnGatesVec = Vec<(StandardGate, SmallVec<[Param; 3]>, SmallVec<[Qubit; 2]>)>;
+
+// A pattern denoted by Pj in [1] for odd number of qubits:
+// [n-2, n-4, n-4, ..., 3, 3, 1, 1, 0, 0, 2, 2, ..., n-3, n-3]
+fn _odd_pattern1(n: isize) -> Vec<isize> {
+    once(n - 2)
+        .chain((0..((n - 3) / 2)).flat_map(|i| [(n - 2 * i - 4); 2]))
+        .chain((0..((n - 1) / 2)).flat_map(|i| [2 * i; 2]))
+        .collect()
+}
+
+// A pattern denoted by Pk in [1] for odd number of qubits:
+// [2, 2, 4, 4, ..., n-1, n-1, n-2, n-2, n-4, n-4, ..., 5, 5, 3, 3, 1]
+fn _odd_pattern2(n: isize) -> Vec<isize> {
+    (0..((n - 1) / 2))
+        .flat_map(|i| [(2 * i + 2); 2])
+        .chain((0..((n - 3) / 2)).flat_map(|i| [n - 2 * i - 2; 2]))
+        .chain(once(1))
+        .collect()
+}
+
+// A pattern denoted by Pj in [1] for even number of qubits:
+// [n-1, n-3, n-3, n-5, n-5, ..., 1, 1, 0, 0, 2, 2, ..., n-4, n-4, n-2]
+fn _even_pattern1(n: isize) -> Vec<isize> {
+    once(n - 1)
+        .chain((0..((n - 2) / 2)).flat_map(|i| [n - 2 * i - 3; 2]))
+        .chain((0..((n - 2) / 2)).flat_map(|i| [2 * i; 2]))
+        .chain(once(n - 2))
+        .collect()
+}
+
+// A pattern denoted by Pk in [1] for even number of qubits:
+// [2, 2, 4, 4, ..., n-2, n-2, n-1, n-1, ..., 3, 3, 1, 1]
+fn _even_pattern2(n: isize) -> Vec<isize> {
+    (0..((n - 2) / 2))
+        .flat_map(|i| [2 * (i + 1); 2])
+        .chain((0..(n / 2)).flat_map(|i| [(n - 2 * i - 1); 2]))
+        .collect()
+}
+
+// Creating the patterns for the phase layers.
+fn _create_patterns(n: isize) -> HashMap<(isize, isize), (isize, isize)> {
+    let (pat1, pat2) = if n % 2 == 0 {
+        (_even_pattern1(n), _even_pattern2(n))
+    } else {
+        (_odd_pattern1(n), _odd_pattern2(n))
+    };
+
+    let ind = if n % 2 == 0 {
+        (2 * n - 4) / 2
+    } else {
+        (2 * n - 4) / 2 - 1
+    };
+
+    HashMap::from_iter((0..n).map(|i| ((0, i), (i, i))).chain(
+        (0..(n / 2)).cartesian_product(0..n).map(|(layer, i)| {
+            (
+                (layer + 1, i),
+                (
+                    pat1[(ind - (2 * layer) + i) as usize],
+                    pat2[((2 * layer) + i) as usize],
+                ),
+            )
+        }),
+    ))
+}
+
+// A single layer of CX gates.
+fn _append_cx_stage1(gates: &mut LnnGatesVec, n: usize) {
+    for i in 0..(n / 2) {
+        gates.push((
+            StandardGate::CXGate,
+            smallvec![],
+            smallvec![Qubit((2 * i) as u32), Qubit((2 * i + 1) as u32)],
+        ))
+    }
+
+    for i in 0..((n + 1) / 2 - 1) {
+        gates.push((
+            StandardGate::CXGate,
+            smallvec![],
+            smallvec![Qubit((2 * i + 2) as u32), Qubit((2 * i + 1) as u32)],
+        ))
+    }
+}
+
+// A single layer of CX gates.
+fn _append_cx_stage2(gates: &mut LnnGatesVec, n: usize) {
+    for i in 0..(n / 2) {
+        gates.push((
+            StandardGate::CXGate,
+            smallvec![],
+            smallvec![Qubit((2 * i + 1) as u32), Qubit((2 * i) as u32)],
+        ))
+    }
+
+    for i in 0..((n + 1) / 2 - 1) {
+        gates.push((
+            StandardGate::CXGate,
+            smallvec![],
+            smallvec![Qubit((2 * i + 1) as u32), Qubit((2 * i + 2) as u32)],
+        ))
+    }
+}
+
+// Appends correct phase gate during CZ synthesis
+fn _append_phase_gate(pat_val: usize, gates: &mut LnnGatesVec, qubit: usize) {
+    // Add phase gates: s, sdg or z
+    if pat_val % 4 == 1 {
+        gates.push((
+            StandardGate::SdgGate,
+            smallvec![],
+            smallvec![Qubit(qubit as u32)],
+        ))
+    } else if pat_val % 4 == 2 {
+        gates.push((
+            StandardGate::ZGate,
+            smallvec![],
+            smallvec![Qubit(qubit as u32)],
+        ))
+    } else if pat_val % 4 == 3 {
+        gates.push((
+            StandardGate::SGate,
+            smallvec![],
+            smallvec![Qubit(qubit as u32)],
+        ))
+    }
+}
+
+// Synthesis of a CZ circuit for linear nearest neighbor (LNN) connectivity,
+// based on Maslov and Roetteler.
+pub(super) fn synth_cz_depth_line_mr(matrix: ArrayView2<bool>) -> (usize, LnnGatesVec) {
+    let num_qubits = matrix.raw_dim()[0];
+    let pats = _create_patterns(num_qubits as isize);
+
+    // s_gates[i] = 0, 1, 2 or 3 for a gate id, sdg, z or s on qubit i respectively
+    let mut s_gates = Array1::<usize>::zeros(num_qubits);
+
+    let mut patlist: Vec<(isize, isize)> = Vec::new();
+
+    let mut gates = LnnGatesVec::new();
+
+    for i in 0..num_qubits {
+        for j in (i + 1)..num_qubits {
+            if matrix[[i, j]] {
+                // CZ(i,j) gate
+                s_gates[[i]] += 2; // qc.z[i]
+                s_gates[[j]] += 2; // qc.z[j]
+                patlist.push((i as isize, j as isize - 1));
+                patlist.push((i as isize, j as isize));
+                patlist.push((i as isize + 1, j as isize - 1));
+                patlist.push((i as isize + 1, j as isize));
+            }
+        }
+    }
+
+    for i in 0..((num_qubits + 1) / 2) {
+        for j in 0..num_qubits {
+            let pat_val = pats[&(i as isize, j as isize)];
+            if patlist.contains(&pat_val) {
+                let patcnt = patlist.iter().filter(|val| **val == pat_val).count();
+                s_gates[[j]] += patcnt; // qc.sdg[j]
+            }
+
+            _append_phase_gate(s_gates[[j]], &mut gates, j)
+        }
+
+        _append_cx_stage1(&mut gates, num_qubits);
+        _append_cx_stage2(&mut gates, num_qubits);
+        s_gates = Array1::<usize>::zeros(num_qubits);
+    }
+
+    if num_qubits % 2 == 0 {
+        let i = num_qubits / 2;
+
+        for j in 0..num_qubits {
+            let pat_val = pats[&(i as isize, j as isize)];
+            if patlist.contains(&pat_val) && pat_val.0 != pat_val.1 {
+                let patcnt = patlist.iter().filter(|val| **val == pat_val).count();
+
+                s_gates[[j]] += patcnt; // qc.sdg[j]
+            }
+
+            _append_phase_gate(s_gates[[j]], &mut gates, j)
+        }
+
+        _append_cx_stage1(&mut gates, num_qubits);
+    }
+
+    (num_qubits, gates)
+}

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

@@ -13,7 +13,9 @@
 use crate::QiskitError;
 use numpy::{IntoPyArray, PyArray2, PyReadonlyArray2, PyReadwriteArray2};
 use pyo3::prelude::*;
+use qiskit_circuit::{circuit_data::CircuitData, operations::Param};
 
+mod lnn;
 mod pmh;
 pub mod utils;
 
@@ -175,6 +177,14 @@ fn check_invertible_binary_matrix(py: Python, mat: PyReadonlyArray2<bool>) -> Py
     Ok(out.to_object(py))
 }
 
+#[pyfunction]
+#[pyo3(signature = (mat))]
+fn synth_cz_depth_line_mr(py: Python, mat: PyReadonlyArray2<bool>) -> PyResult<CircuitData> {
+    let view = mat.as_array();
+    let (num_qubits, lnn_gates) = lnn::synth_cz_depth_line_mr(view);
+    CircuitData::from_standard_gates(py, num_qubits as u32, lnn_gates, Param::Float(0.0))
+}
+
 pub fn linear(m: &Bound<PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(gauss_elimination_with_perm))?;
     m.add_wrapped(wrap_pyfunction!(gauss_elimination))?;
@@ -187,5 +197,6 @@ pub fn linear(m: &Bound<PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(random_invertible_binary_matrix))?;
     m.add_wrapped(wrap_pyfunction!(check_invertible_binary_matrix))?;
     m.add_wrapped(wrap_pyfunction!(pmh::synth_cnot_count_full_pmh))?;
+    m.add_wrapped(wrap_pyfunction!(synth_cz_depth_line_mr))?;
     Ok(())
 }