Fix the matrix representation of CUGate in Rust (#13121) (#13124)

Co-authored-by: Matthew Treinish <[email protected]> (cherry picked from commit 8929e12) Co-authored-by: Julien Gacon <[email protected]>
Qiskit · Sep 10, 2024 · 9a393f1 · 9a393f1
1 parent 7f60c17
commit 9a393f1
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Showing 3 changed files with 13 additions and 4 deletions.
diff --git a/crates/circuit/src/gate_matrix.rs b/crates/circuit/src/gate_matrix.rs
@@ -387,12 +387,12 @@ pub fn cu_gate(theta: f64, phi: f64, lam: f64, gamma: f64) -> GateArray2Q {
             C_ZERO,
             c64(0., gamma).exp() * cos_theta,
             C_ZERO,
-            c64(0., gamma + phi).exp() * (-1.) * sin_theta,
+            c64(0., gamma + lam).exp() * (-1.) * sin_theta,
         ],
         [C_ZERO, C_ZERO, C_ONE, C_ZERO],
         [
             C_ZERO,
-            c64(0., gamma + lam).exp() * sin_theta,
+            c64(0., gamma + phi).exp() * sin_theta,
             C_ZERO,
             c64(0., gamma + phi + lam).exp() * cos_theta,
         ],

diff --git a/releasenotes/notes/fix-cu-rust-6464b6893ecca1b3.yaml b/releasenotes/notes/fix-cu-rust-6464b6893ecca1b3.yaml
@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    Fixed the definition of the :class:`.CUGate` matrix in Rust-space. 
+    While this was not noticable while handling the :class:`.CUGate` purely on 
+    Python side, this had knock-on effects when transpiler passes were using the 
+    Rust representation, such as could happen in :class:`.Consolidate2qBlocks`.
+    Fixed `#13118 <https://github.com/Qiskit/qiskit/issues/13118>`__.
+
diff --git a/test/python/circuit/test_rust_equivalence.py b/test/python/circuit/test_rust_equivalence.py
@@ -66,7 +66,7 @@ def test_definitions(self):
                 continue
 
             with self.subTest(name=name):
-                params = [pi] * standard_gate._num_params()
+                params = [0.1 * (i + 1) for i in range(standard_gate._num_params())]
                 py_def = gate_class.base_class(*params).definition
                 rs_def = standard_gate._get_definition(params)
                 if py_def is None:
@@ -141,7 +141,7 @@ def test_matrix(self):
                 continue
 
             with self.subTest(name=name):
-                params = [0.1] * standard_gate._num_params()
+                params = [0.1 * (i + 1) for i in range(standard_gate._num_params())]
                 py_def = gate_class.base_class(*params).to_matrix()
                 rs_def = standard_gate._to_matrix(params)
                 np.testing.assert_allclose(rs_def, py_def)