Merge branch 'main' into cphase-rzz-equivalence

.github/ISSUE_TEMPLATE/config.yml

@@ -2,4 +2,4 @@ blank_issues_enabled: true
 contact_links:
   - name: Non-API docs issues
     url: https://github.com/Qiskit/documentation/issues/new/choose
-    about: Open an issue about documentation in the Start, Build, Transpile, Verify, Run, or Migration guides sections of docs.quantum.ibm.com (non-API documentation)
+    about: Open an issue about documentation in the guides and additional resources sections of docs.quantum.ibm.com (non-API documentation)

crates/accelerate/Cargo.toml

@@ -54,5 +54,5 @@ version = "0.2.0"
 features = ["ndarray"]
 
 [dependencies.pulp]
-version = "0.18.21"
+version = "0.18.22"
 features = ["macro"]

crates/accelerate/src/synthesis/linear_phase/cz_depth_lnn.rs

@@ -0,0 +1,171 @@
+// 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};
+
+use crate::synthesis::permutation::{_append_cx_stage1, _append_cx_stage2};
+
+// A sequence of Lnn gates
+// Represents the return type for Lnn Synthesis algorithms
+pub(crate) 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: usize) -> Vec<usize> {
+    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: usize) -> Vec<usize> {
+    (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: usize) -> Vec<usize> {
+    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: usize) -> Vec<usize> {
+    (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: usize) -> HashMap<(usize, usize), (usize, usize)> {
+    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], pat2[(2 * layer) + i]),
+            )
+        }),
+    ))
+}
+
+/// 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
+    let gate_id = pat_val % 4;
+    if gate_id != 0 {
+        let gate = match gate_id {
+            1 => StandardGate::SdgGate,
+            2 => StandardGate::ZGate,
+            3 => StandardGate::SGate,
+            _ => unreachable!(), // unreachable as we have modulo 4
+        };
+        gates.push((gate, 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_inner(matrix: ArrayView2<bool>) -> (usize, LnnGatesVec) {
+    let num_qubits = matrix.raw_dim()[0];
+    let pats = _create_patterns(num_qubits);
+
+    // 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<(usize, usize)> = 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, j - 1));
+                patlist.push((i, j));
+                patlist.push((i + 1, j - 1));
+                patlist.push((i + 1, j));
+            }
+        }
+    }
+
+    for i in 0..((num_qubits + 1) / 2) {
+        for j in 0..num_qubits {
+            let pat_val = pats[&(i, j)];
+            if patlist.contains(&pat_val) {
+                // patcnt should be 0 or 1, which checks if a Sdg gate should be added
+                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, j)];
+            if patlist.contains(&pat_val) && pat_val.0 != pat_val.1 {
+                // patcnt should be 0 or 1, which checks if a Sdg gate should be added
+                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_phase/mod.rs

@@ -0,0 +1,46 @@
+// 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 numpy::PyReadonlyArray2;
+use pyo3::{
+    prelude::*,
+    pyfunction,
+    types::{PyModule, PyModuleMethods},
+    wrap_pyfunction, Bound, PyResult,
+};
+use qiskit_circuit::{circuit_data::CircuitData, operations::Param};
+
+pub(crate) mod cz_depth_lnn;
+
+/// Synthesis of a CZ circuit for linear nearest neighbor (LNN) connectivity,
+/// based on Maslov and Roetteler.
+///
+///  Note that this method *reverts* the order of qubits in the circuit,
+///  and returns a circuit containing :class:`.CXGate`\s and phase gates
+/// (:class:`.SGate`, :class:`.SdgGate` or :class:`.ZGate`).
+///
+/// References:
+///     1. Dmitri Maslov, Martin Roetteler,
+///        *Shorter stabilizer circuits via Bruhat decomposition and quantum circuit transformations*,
+///        `arXiv:1705.09176 <https://arxiv.org/abs/1705.09176>`_.
+#[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) = cz_depth_lnn::synth_cz_depth_line_mr_inner(view);
+    CircuitData::from_standard_gates(py, num_qubits as u32, lnn_gates, Param::Float(0.0))
+}
+
+pub fn linear_phase(m: &Bound<PyModule>) -> PyResult<()> {
+    m.add_wrapped(wrap_pyfunction!(synth_cz_depth_line_mr))?;
+    Ok(())
+}

crates/accelerate/src/synthesis/mod.rs

@@ -12,6 +12,7 @@
 
 mod clifford;
 pub mod linear;
+pub mod linear_phase;
 mod permutation;
 
 use pyo3::prelude::*;
@@ -21,6 +22,10 @@ pub fn synthesis(m: &Bound<PyModule>) -> PyResult<()> {
     linear::linear(&linear_mod)?;
     m.add_submodule(&linear_mod)?;
 
+    let linear_phase_mod = PyModule::new_bound(m.py(), "linear_phase")?;
+    linear_phase::linear_phase(&linear_phase_mod)?;
+    m.add_submodule(&linear_phase_mod)?;
+
     let permutation_mod = PyModule::new_bound(m.py(), "permutation")?;
     permutation::permutation(&permutation_mod)?;
     m.add_submodule(&permutation_mod)?;

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

@@ -20,6 +20,8 @@ use qiskit_circuit::circuit_data::CircuitData;
 use qiskit_circuit::operations::{Param, StandardGate};
 use qiskit_circuit::Qubit;
 
+use super::linear_phase::cz_depth_lnn::LnnGatesVec;
+
 mod utils;
 
 /// Checks whether an array of size N is a permutation of 0, 1, ..., N - 1.
@@ -114,11 +116,82 @@ pub fn _synth_permutation_depth_lnn_kms(
     )
 }
 
+/// A single layer of CX gates.
+pub(crate) 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.
+pub(crate) 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)],
+        ))
+    }
+}
+
+/// Append reverse permutation to a QuantumCircuit for linear nearest-neighbor architectures
+/// using Kutin, Moulton, Smithline method.
+fn _append_reverse_permutation_lnn_kms(gates: &mut LnnGatesVec, num_qubits: usize) {
+    (0..(num_qubits + 1) / 2).for_each(|_| {
+        _append_cx_stage1(gates, num_qubits);
+        _append_cx_stage2(gates, num_qubits);
+    });
+
+    if num_qubits % 2 == 0 {
+        _append_cx_stage1(gates, num_qubits);
+    }
+}
+
+/// Synthesize reverse permutation for linear nearest-neighbor architectures using
+/// Kutin, Moulton, Smithline method.
+///
+/// Synthesis algorithm for reverse permutation from [1], section 5.
+/// This algorithm synthesizes the reverse permutation on :math:`n` qubits over
+/// a linear nearest-neighbor architecture using CX gates with depth :math:`2 * n + 2`.
+///
+/// References:
+///     1. Kutin, S., Moulton, D. P., Smithline, L.,
+///        *Computation at a distance*, Chicago J. Theor. Comput. Sci., vol. 2007, (2007),
+///        `arXiv:quant-ph/0701194 <https://arxiv.org/abs/quant-ph/0701194>`_
+#[pyfunction]
+#[pyo3(signature = (num_qubits))]
+fn synth_permutation_reverse_lnn_kms(py: Python, num_qubits: usize) -> PyResult<CircuitData> {
+    let mut gates = LnnGatesVec::new();
+    _append_reverse_permutation_lnn_kms(&mut gates, num_qubits);
+    CircuitData::from_standard_gates(py, num_qubits as u32, gates, Param::Float(0.0))
+}
+
 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)?)?;
+    m.add_function(wrap_pyfunction!(synth_permutation_reverse_lnn_kms, m)?)?;
     Ok(())
 }