Remove duplicated weyl_coordinates python function (Qiskit#13193)

This commit removes the weyl_coordinates() function from the private
qiskit.synthesis.two_qubit.weyl module. This function's internal use was
ported to rust as part of Qiskit#11019 but it left the python implementation
intact while we ensured the rust implementation was reliable longer
term. Since then we've ported the majority of the two qubit synthesis to
rust now and the only usage of this python implementation was the unit
tests. This commit removes the python implementation and the entire
internal weyl module as nothing uses it anymore. A python interface is
added to the rust function and the tests are updated to call that
instead.

Fixes: Qiskit#8459

Author: mtreinish

crates/accelerate/src/two_qubit_decompose.rs

@@ -216,6 +216,22 @@ fn py_decompose_two_qubit_product_gate(
     ))
 }
 
+/// Computes the Weyl coordinates for a given two-qubit unitary matrix.
+///
+/// Args:
+///     U (np.ndarray): Input two-qubit unitary.
+///
+/// Returns:
+///     np.ndarray: Array of the 3 Weyl coordinates.
+#[pyfunction]
+fn weyl_coordinates(py: Python, unitary: PyReadonlyArray2<Complex64>) -> PyObject {
+    let array = unitary.as_array();
+    __weyl_coordinates(array.into_faer_complex())
+        .to_vec()
+        .into_pyarray_bound(py)
+        .into()
+}
+
 fn __weyl_coordinates(unitary: MatRef<c64>) -> [f64; 3] {
     let uscaled = scale(C1 / unitary.determinant().powf(0.25)) * unitary;
     let uup = transform_from_magic_basis(uscaled);
@@ -2353,6 +2369,7 @@ pub fn two_qubit_decompose(m: &Bound<PyModule>) -> PyResult<()> {
     m.add_wrapped(wrap_pyfunction!(local_equivalence))?;
     m.add_wrapped(wrap_pyfunction!(py_trace_to_fid))?;
     m.add_wrapped(wrap_pyfunction!(py_ud))?;
+    m.add_wrapped(wrap_pyfunction!(weyl_coordinates))?;
     m.add_class::<TwoQubitGateSequence>()?;
     m.add_class::<TwoQubitWeylDecomposition>()?;
     m.add_class::<Specialization>()?;

qiskit/synthesis/two_qubit/weyl.py

@@ -17,8 +17,8 @@
 import numpy as np
 from numpy.testing import assert_allclose
 
+from qiskit._accelerate.two_qubit_decompose import weyl_coordinates
 from qiskit.quantum_info.random import random_unitary
-from qiskit.synthesis.two_qubit.weyl import weyl_coordinates
 from qiskit.synthesis.two_qubit.local_invariance import (
     two_qubit_local_invariants,
     local_equivalence,
@@ -32,7 +32,7 @@ class TestWeyl(QiskitTestCase):
     def test_weyl_coordinates_simple(self):
         """Check Weyl coordinates against known cases."""
         # Identity [0,0,0]
-        U = np.identity(4)
+        U = np.identity(4, dtype=complex)
         weyl = weyl_coordinates(U)
         assert_allclose(weyl, [0, 0, 0])
 

test/python/synthesis/test_weyl.py

@@ -20,10 +20,10 @@
 import ddt
 import numpy as np
 
+from qiskit._accelerate.two_qubit_decompose import weyl_coordinates
 from qiskit.circuit import QuantumCircuit
 from qiskit.circuit.library import RZGate, UnitaryGate
 import qiskit.quantum_info.operators
-from qiskit.synthesis.two_qubit.weyl import weyl_coordinates
 from qiskit.synthesis.two_qubit.xx_decompose.circuits import (
     decompose_xxyy_into_xxyy_xx,
     xx_circuit_step,