Fix operation list mutation master (#475)

* stop mutating input to apply

* changelog

* Auto update version

* Trigger CI.

* Fix dtype in TestAdjointJacobianQNode.

* Fix dtype in jax tests.

* Change jax config if float64.

* Reformat.

---------

Co-authored-by: albi3ro <chrissie.c.l@gmail.com>
Co-authored-by: Dev version update bot <github-actions[bot]@users.noreply.github.com>

.github/CHANGELOG.md

@@ -16,11 +16,14 @@
 
 ### Bug fixes
 
+* `apply` no longer mutates the inputted list of operations.
+  [(#475)](https://github.com/PennyLaneAI/pennylane-lightning/pull/475)
+
 ### Contributors
 
 This release contains contributions from (in alphabetical order):
 
-Vincent Michaud-Rioux
+Amintor Dusko, Christina Lee, Vincent Michaud-Rioux, Lee J. O'Riordan
 
 ---
 

pennylane_lightning/_version.py

@@ -16,4 +16,4 @@
    Version number (major.minor.patch[-label])
 """
 
-__version__ = "0.32.0-dev4"
+__version__ = "0.32.0-dev5"

pennylane_lightning/lightning_qubit.py

@@ -419,10 +419,10 @@ def apply(self, operations, rotations=None, **kwargs):
         if operations:  # make sure operations[0] exists
             if isinstance(operations[0], QubitStateVector):
                 self._apply_state_vector(operations[0].parameters[0].copy(), operations[0].wires)
-                del operations[0]
+                operations = operations[1:]
             elif isinstance(operations[0], BasisState):
                 self._apply_basis_state(operations[0].parameters[0], operations[0].wires)
-                del operations[0]
+                operations = operations[1:]
 
         for operation in operations:
             if isinstance(operation, (QubitStateVector, BasisState)):

tests/test_adjoint_jacobian.py

@@ -789,6 +789,10 @@ def test_interface_jax(self, dev):
         jax interface"""
 
         jax = pytest.importorskip("jax")
+        if dev.R_DTYPE == np.float64:
+            from jax.config import config
+
+            config.update("jax_enable_x64", True)
 
         def f(params1, params2):
             qml.RX(0.4, wires=[0])

tests/test_apply.py

@@ -203,7 +203,10 @@ def test_apply_operation_state_preparation(
         par = np.array(par)
         dev = qubit_device(wires=2)
         dev.reset()
-        dev.apply([operation(par, wires=[0, 1])])
+        ops = [operation(par, wires=[0, 1])]
+
+        dev.apply(ops)
+        assert len(ops) == 1  # input not mutated
 
         assert np.allclose(dev.state, np.array(expected_output), atol=tol, rtol=0)