Add qubits to Delay target entry

If any instructions available in a target are ideal, with no qubits or
properties set, the target class assumes the backend is ideal (like in
the case of an ideal simulator where are all instructions are globally
defined and have no error or duration). To avoid this we need to define
the Delay instruction on all qubits explicitly. This commit makes this
change to ensure the target for backends still shows the qubits and
properties for the other operations. However, in adding an instruction
with no properties defined a bug in the plot gate error map function was
uncovered where it errored because it assumes all instructions have
properties defined, this was fixed at the same time.

qiskit/test/mock/utils/backend_converter.py

@@ -44,7 +44,6 @@ def convert_to_target(conf_dict: dict, props_dict: dict = None, defs_dict: dict
     if props_dict:
         qubit_props = qubit_props_from_props(props_dict)
     target = Target(qubit_properties=qubit_props)
-    target.add_instruction(Delay(Parameter("t")))
     # Parse from properties if it exsits
     if props_dict is not None:
         # Parse instructions
@@ -125,6 +124,9 @@ def convert_to_target(conf_dict: dict, props_dict: dict = None, defs_dict: dict
                             target[inst][(qubit,)].calibration = sched
                     else:
                         target[inst][qarg].calibration = sched
+    target.add_instruction(
+        Delay(Parameter("t")), {(bit,): None for bit in range(target.num_qubits)}
+    )
     return target
 
 

qiskit/visualization/gate_map.py

@@ -958,6 +958,8 @@ def plot_error_map(backend, figsize=(12, 9), show_title=True, qubit_coordinates=
             if prop_dict is None or None in prop_dict:
                 continue
             for qargs, inst_props in prop_dict.items():
+                if inst_props is None:
+                    continue
                 if gate == "measure":
                     if inst_props.error is not None:
                         read_err[qargs[0]] = inst_props.error