fix metadata/params

Author: ciaranra

python/quantum-pecos/src/pecos/circuits/quantum_circuit.py

@@ -262,14 +262,6 @@ def _add_gate_to_tick(
             symbol = symbol.symbol if hasattr(symbol, "symbol") else str(symbol)
         symbol_upper = symbol.upper()
 
-        # Convert locations to list, filtering out None values (placeholders for logical gates)
-        loc_list = [loc for loc in locations if loc is not None]
-        if not loc_list:
-            # No qubit operands -- store symbol as tick-level metadata
-            # (e.g., global barriers or marker gates)
-            tick_handle.meta("_symbol", symbol)
-            return
-
         # Serialize params for storage (handle tuples -> lists)
         def make_serializable(obj: object) -> object:
             if isinstance(obj, tuple):
@@ -282,6 +274,16 @@ def make_serializable(obj: object) -> object:
 
         params_json = json.dumps({k: make_serializable(v) for k, v in params.items()}) if params else ""
 
+        # Convert locations to list, filtering out None values (placeholders for logical gates)
+        loc_list = [loc for loc in locations if loc is not None]
+        if not loc_list:
+            # No qubit operands -- store symbol and params as tick-level metadata
+            # (e.g., global barriers or marker gates)
+            tick_handle.meta("_symbol", symbol)
+            if params_json:
+                tick_handle.meta("_params", params_json)
+            return
+
         # Helper to store original symbol and params in metadata (idempotent - skips if qubit already used)
         def add_with_symbol(
             method: Callable[..., object],
@@ -757,7 +759,15 @@ def _iter_tick(
         if not grouped:
             tick_symbol = tick_obj.get_attr("_symbol")
             if tick_symbol is not None:
-                yield tick_symbol, set(), {}
+                tick_params: JSONDict = {}
+                tick_params_json = tick_obj.get_attr("_params")
+                if tick_params_json is not None:
+                    try:
+                        tick_params = json.loads(tick_params_json)
+                        tick_params = self._fix_json_meta(tick_params)
+                    except json.JSONDecodeError:
+                        pass
+                yield tick_symbol, set(), tick_params
                 return
 
         # Yield grouped results
@@ -898,7 +908,7 @@ def __setitem__(self, tick: int, item: tuple[GateDict, JSONDict]) -> None:
         # Get qubits to discard first
         tick_obj = self._inner.get_tick(actual_tick)
         if tick_obj is not None:
-            qubits_to_discard = list(tick_obj.active_qubits())
+            qubits_to_discard = [int(q) for q in tick_obj.active_qubits()]
             if qubits_to_discard:
                 self._inner.discard(qubits_to_discard, actual_tick)
 
@@ -926,7 +936,7 @@ def __delitem__(self, tick: int) -> None:
         actual_tick = tick if tick >= 0 else len(self) + tick
         tick_obj = self._inner.get_tick(actual_tick)
         if tick_obj is not None:
-            qubits_to_discard = list(tick_obj.active_qubits())
+            qubits_to_discard = [int(q) for q in tick_obj.active_qubits()]
             if qubits_to_discard:
                 self._inner.discard(qubits_to_discard, actual_tick)