Fix cat state function array type without doing casting (#556)

* Fixed cat state function array type (#554)

* Fixed cat state function array type (#554)

* Update ops.py

* Update states.py

* multiply by 1.0

* Apply suggestions from code review

Co-authored-by: antalszava <antalszava@gmail.com>

Co-authored-by: tguillaume <tguillaume506@gmail.com>
Co-authored-by: antalszava <antalszava@gmail.com>

strawberryfields/ops.py

@@ -867,8 +867,9 @@ def _apply(self, reg, backend, **kwargs):
         N = temp / pf.sqrt(2 * (1 + pf.cos(phi) * temp ** 4))
 
         # coherent states
-        c1 = (alpha ** l) / np.sqrt(ssp.factorial(l))
-        c2 = ((-alpha) ** l) / np.sqrt(ssp.factorial(l))
+        # Need to cast  alpha to float before exponentiation to avoid overflow
+        c1 = ((1.0 * alpha) ** l) / np.sqrt(ssp.factorial(l))
+        c2 = ((-1.0 * alpha) ** l) / np.sqrt(ssp.factorial(l))
         # add them up with a relative phase
         ket = (c1 + pf.exp(1j * phi) * c2) * N
 

strawberryfields/utils/states.py

@@ -305,8 +305,9 @@ def cat_state(a, p=0, fock_dim=5):
 
     # coherent states
     k = np.arange(fock_dim)
-    c1 = (a ** k) / np.sqrt(fac(k))
-    c2 = ((-a) ** k) / np.sqrt(fac(k))
+    # Need to cast a to float before exponentiation to avoid overflow
+    c1 = ((1.0 * a) ** k) / np.sqrt(fac(k))
+    c2 = ((-1.0 * a) ** k) / np.sqrt(fac(k))
 
     # add them up with a relative phase
     ket = (c1 + np.exp(1j * phi) * c2) * N