Fix UnitaryGate.repeat() method

qiskit/circuit/gate.py

@@ -97,7 +97,10 @@ def __pow__(self, exponent: float) -> "Gate":
         return self.power(exponent)
 
     def _return_repeat(self, exponent: float) -> "Gate":
-        return Gate(name=f"{self.name}*{exponent}", num_qubits=self.num_qubits, params=self.params)
+        gate = Gate(name=f"{self.name}*{exponent}", num_qubits=self.num_qubits, params=[])
+        gate.validate_parameter = self.validate_parameter
+        gate.params = self.params
+        return gate
 
     def control(
         self,

releasenotes/notes/fix_11990-8551c7250207fc76.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+  - |
+    Fixes an error when calling the method :meth:`.UnitaryGate.repeat`. 
+    Refer to `#11990 <https://github.com/Qiskit/qiskit/issues/11990>` for more
+    details.

test/python/circuit/library/test_permutation.py

@@ -104,6 +104,12 @@ def test_inverse(self):
         expected_inverse_perm = PermutationGate([3, 0, 5, 1, 4, 2])
         self.assertTrue(np.array_equal(inverse_perm.pattern, expected_inverse_perm.pattern))
 
+    def test_repeat(self):
+        """Test the ``repeat`` method."""
+        pattern = [2, 4, 1, 3, 0]
+        perm = PermutationGate(pattern)
+        self.assertTrue(np.allclose(Operator(perm.repeat(2)), Operator(perm) @ Operator(perm)))
+
 
 class TestPermutationGatesOnCircuit(QiskitTestCase):
     """Tests for quantum circuits containing permutations."""

test/python/circuit/test_isometry.py

@@ -133,6 +133,21 @@ def test_isometry_inverse(self, iso):
         result = Operator(qc)
         np.testing.assert_array_almost_equal(result.data, np.identity(result.dim[0]))
 
+    @data(
+        np.eye(2, 2),
+        random_unitary(2, seed=297102).data,
+        np.eye(4, 4),
+        random_unitary(4, seed=123642).data,
+        random_unitary(8, seed=568288).data,
+    )
+    def test_isometry_repeat(self, iso):
+        """Tests for the repeat of isometries from n to n qubits"""
+        iso_gate = Isometry(iso, 0, 0)
+
+        op = Operator(iso_gate)
+        op_double = Operator(iso_gate.repeat(2))
+        np.testing.assert_array_almost_equal(op @ op, op_double)
+
 
 if __name__ == "__main__":
     unittest.main()

test/python/circuit/test_uc.py

@@ -100,6 +100,13 @@ def test_inverse_ucg(self):
 
         self.assertTrue(np.allclose(unitary_desired, unitary))
 
+    def test_repeat(self):
+        """test repeat operation"""
+        gates = [random_unitary(2, seed=seed).data for seed in [124435, 876345, 687462, 928365]]
+
+        uc = UCGate(gates, up_to_diagonal=False)
+        self.assertTrue(np.allclose(Operator(uc.repeat(2)), Operator(uc) @ Operator(uc)))
+
 
 def _get_ucg_matrix(squs):
     return block_diag(*squs)

test/python/circuit/test_unitary.py

@@ -67,6 +67,11 @@ def test_adjoint(self):
         uni = UnitaryGate([[0, 1j], [-1j, 0]])
         self.assertTrue(numpy.array_equal(uni.adjoint().to_matrix(), uni.to_matrix()))
 
+    def test_repeat(self):
+        """test repeat operation"""
+        uni = UnitaryGate([[1, 0], [0, 1j]])
+        self.assertTrue(numpy.array_equal(Operator(uni.repeat(2)), Operator(uni) @ Operator(uni)))
+
 
 class TestUnitaryCircuit(QiskitTestCase):
     """Matrix gate circuit tests."""