Avoid SyntaxWarning in Python 3.2

Author: mhucka

src/openfermion/circuits/gates/four_qubit_gates.py

@@ -15,6 +15,7 @@
 
 import numpy as np
 import sympy
+import warnings
 
 import cirq
 from cirq._compat import proper_repr
@@ -120,8 +121,10 @@ def _circuit_diagram_info_(self, args: cirq.CircuitDiagramInfoArgs) -> cirq.Circ
         if args.use_unicode_characters:
             wire_symbols = ('⇅', '⇅', '⇵', '⇵')
         else:
-            # pylint: disable=anomalous-backslash-in-string
-            wire_symbols = (r'/\ \/', r'/\ \/', '\/ /\\', '\/ /\\')
+            up_down = r'/\ \/'
+            # Split up this string to avoid SyntaxError in Python 3.12.
+            down_up = r'\/ /' + '\\'
+            wire_symbols = (up_down, up_down, down_up, down_up)
         return cirq.CircuitDiagramInfo(
             wire_symbols=wire_symbols, exponent=self._diagram_exponent(args)
         )