Kappa eta fix

docs/source/changelog.rst

@@ -19,6 +19,8 @@ Bug Fixes
 +++++++++
 
 - Fix `convert_complex_to_dm` to properly return arrays with real dtype.
+- Fix `Cell.kappa` and `Cell.eta` to properly introspect `q` when first edge on the graph
+  happens to not be dipole-allowed.
 
 Deprecations
 ++++++++++++

src/rydiqule/cell.py

@@ -390,7 +390,14 @@ def kappa(self) -> float:
                     " = <value> prior to running calculations"
             warnings.warn(msg)
 
-        q = self.couplings.edges[ground_manifold[0], excited_manifold[0]]["q"]
+        # extract q from coupling group, this ensures we find a dipole allowed edge with q defined
+        manifold_subgraph = self._coupling_subgraph(self.probe_tuple)
+        for (_, _, d) in manifold_subgraph.edges(data=True):
+            if 'q' in d:
+                q = d['q']
+                break
+        else:
+            raise RydiquleError(f"No 'q' defined for coupling {self.probe_tuple}")
 
         omega_rad = self.atom.get_transition_frequency(probe_g_nlj, probe_e_nlj)*2*np.pi
         dipole_moment = self.atom.get_dipole_matrix_element(probe_g_nlj, probe_e_nlj, q=q)*a0*e
@@ -481,7 +488,14 @@ def eta(self) -> float:
                     " = <value> prior to running calculations"
             warnings.warn(msg)
 
-        q = self.couplings.edges[ground_manifold[0], excited_manifold[0]]["q"]
+        # extract q from coupling group, this ensures we find a dipole allowed edge with q defined
+        manifold_subgraph = self._coupling_subgraph(self.probe_tuple)
+        for (_, _, d) in manifold_subgraph.edges(data=True):
+            if 'q' in d:
+                q = d['q']
+                break
+        else:
+            raise RydiquleError(f"No 'q' defined for coupling {self.probe_tuple}")
 
         omega_rad = self.atom.get_transition_frequency(probe_g_nlj, probe_e_nlj)*2.0*np.pi
         dipole_moment = self.atom.get_dipole_matrix_element(probe_g_nlj, probe_e_nlj, q=q)*a0*e

src/rydiqule/sensor.py

@@ -3066,6 +3066,29 @@ def states_with_spec(self, statespec: StateSpec) -> List[State]:
 
         """
         return match_states(statespec, self.states)
+
+
+    def _coupling_subgraph(self, coupling: StateSpecs) -> nx.Graph:
+        """
+        Returns a subgraph view of the couplings graph corresponding to `coupling`.
+
+        Parameters
+        ----------
+        coupling: StateSpecs
+            Coupling specification
+
+        Returns
+        -------
+        networkx.Graph
+            View of the corresponding subgraph
+        """
+
+        states1 = self.states_with_spec(coupling[0])
+        states2 = self.states_with_spec(coupling[1])
+
+        subgraph = self.couplings.subgraph(states1 + states2)
+
+        return subgraph
 
 
     def get_couplings(self) -> Dict[States, CouplingDict]: