Fix unintended mutation of original matrix in swap_rows_columns_list

Bug:
- When swapping rows and columns of a numpy array within the  function, the original matrix in memory was inadvertently modified due to mutable behavior of numpy arrays.

Fix:
- Created a copy of the input matrix inside the function before making any modifications. This ensures that only the copied matrix is altered, while the original matrix remains unchanged.

Makefile

@@ -1,5 +1,5 @@
 # Variables
-PYTHON_VERSION = python3.11
+PYTHON_VERSION = python3.10
 PIP = .venv/bin/pip
 PYTEST = .venv/bin/pytest
 PRE_COMMIT = .venv/bin/pre-commit

pyproject.toml

@@ -11,7 +11,7 @@ requires-python = ">=3.9"
 dependencies = [
     "scipy",
     "qutip",
-    "numpy",
+    "numpy==1.23.5",
     "qiskit",
     "qiskit-aer",
     "weylchamber",

src/mirror_gates/fast_unitary.py

@@ -161,6 +161,12 @@ def _compute_unitary(self, block, qubit_map) -> UnitaryGate:
                     # The qubit order is reversed
                     def swap_rows_columns_list(unitary):
                         """Handle swapping qarg ordering."""
+                        # make a copy to avoid mutable object errors
+                        unitary = unitary.copy()
+
+                        # # XXX no idea why this error occurs, but temp fix
+                        # unitary.setflags(write=True)
+
                         unitary[:, [1, 2]] = unitary[:, [2, 1]]
                         unitary[[1, 2], :] = unitary[[2, 1], :]
                         return unitary