Deprecate backend defaults (#2186)

* Deprecate backend defaults

* Add release note

* update deprecation msg

Author: kt474

qiskit_ibm_runtime/fake_provider/fake_backend.py

@@ -168,14 +168,22 @@ def properties(self, refresh: bool = False) -> BackendProperties:
         return BackendProperties.from_dict(self._props_dict)
 
     def defaults(self, refresh: bool = False) -> PulseDefaults:
-        """Return the pulse defaults for the backend
+        """(DEPRECATED)Return the pulse defaults for the backend
 
         Args:
             refresh: If ``True``, re-retrieve the backend defaults from the local file.
 
         Returns:
             The backend pulse defaults or ``None`` if the backend does not support pulse.
         """
+
+        issue_deprecation_msg(
+            "The defaults method and the PulseDefaults class have been deprecated",
+            "0.38.0",
+            "IBM backends no longer support pulse gates and are no longer used to "
+            "construct the backend target. ",
+        )
+
         if refresh or self._defs_dict is None:
             self._set_defs_dict_from_json()
         if self._defs_dict:

qiskit_ibm_runtime/ibm_backend.py

@@ -425,7 +425,7 @@ def status(self) -> BackendStatus:
             ) from ex
 
     def defaults(self, refresh: bool = False) -> Optional[PulseDefaults]:
-        """Return the pulse defaults for the backend.
+        """(DEPRECATED) Return the pulse defaults for the backend.
 
         The schema for default pulse configuration can be found in
         `Qiskit/ibm-quantum-schemas/default_pulse_configuration
@@ -438,6 +438,14 @@ def defaults(self, refresh: bool = False) -> Optional[PulseDefaults]:
         Returns:
             The backend pulse defaults or ``None`` if the backend does not support pulse.
         """
+
+        issue_deprecation_msg(
+            "The defaults method and the PulseDefaults class have been deprecated",
+            "0.38.0",
+            "IBM backends no longer support pulse gates and are no longer used to "
+            "construct the backend target. ",
+        )
+
         if refresh or self._defaults is None:
             api_defaults = self._api_client.backend_pulse_defaults(self.name)
             if api_defaults:

qiskit_ibm_runtime/models/pulse_defaults.py

@@ -158,9 +158,9 @@ def from_dict(cls: Type[CommandT], data: Dict[str, Any]) -> CommandT:
 
 
 class PulseDefaults:
-    """Description of default settings for Pulse systems. These are instructions or settings that
-    may be good starting points for the Pulse user. The user may modify these defaults for custom
-    scheduling.
+    """(DEPRECATED) Description of default settings for Pulse systems.
+    These are instructions or settings that may be good starting points for the Pulse user.
+    The user may modify these defaults for custom scheduling.
     """
 
     _data: Dict[Any, Any] = {}

release-notes/unreleased/2186.deprecation.rst

@@ -0,0 +1,2 @@
+Since pulse gates are no longer supported, the :class:`IBMBackend` and :class:`FakeBackendV2` ``defaults()`` 
+method has been deprecated. Backend defaults are also no longer used to construct the backend target.