Deprecate channel strategy (#1931)

* Deprecate channel strategy

* add release note

* formatting

* formatting

* Updating wording

Author: kt474

qiskit_ibm_runtime/qiskit_runtime_service.py

@@ -116,7 +116,7 @@ def __init__(
                 ``username_ntlm``, ``password_ntlm`` (username and password to enable NTLM user
                 authentication)
             verify: Whether to verify the server's TLS certificate.
-            channel_strategy: Error mitigation strategy.
+            channel_strategy: (DEPRECATED) Error mitigation strategy.
             private_endpoint: Connect to private API URL.
             url_resolver: Function used to resolve the runtime url.
 
@@ -128,6 +128,20 @@ def __init__(
         """
         super().__init__()
 
+        if channel_strategy:
+            warnings.warn(
+                (
+                    "As of qiskit-ibm-runtime version 0.30.0, the channel_strategy parameter is "
+                    "deprecated. Q-CTRL Performance Management strategy currently offered "
+                    "on the Qiskit Runtime Service will be removed on 18 October, 2024. "
+                    "To continue using Q-CTRL in your workflow, use one of the following options: "
+                    "Qiskit Functions Catalog: https://quantum.ibm.com/functions, or "
+                    "Fire Opal: https://q-ctrl.com/fire-opal"
+                ),
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
         self._account = self._discover_account(
             token=token,
             url=url,
@@ -698,12 +712,26 @@ def save_account(
                 authentication)
             verify: Verify the server's TLS certificate.
             overwrite: ``True`` if the existing account is to be overwritten.
-            channel_strategy: Error mitigation strategy.
+            channel_strategy: (DEPRECATED) Error mitigation strategy.
             set_as_default: If ``True``, the account is saved in filename,
                 as the default account.
             private_endpoint: Connect to private API URL.
         """
 
+        if channel_strategy:
+            warnings.warn(
+                (
+                    "As of qiskit-ibm-runtime version 0.30.0, the channel_strategy parameter is "
+                    "deprecated. Q-CTRL Performance Management strategy currently offered "
+                    "on the Qiskit Runtime Service will be removed on 18 October, 2024."
+                    "To continue using Q-CTRL in your workflow, use one of the following options: "
+                    "Qiskit Functions Catalog: https://quantum.ibm.com/functions, or "
+                    "Fire Opal: https://q-ctrl.com/fire-opal"
+                ),
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
         AccountManager.save(
             token=token,
             url=url,

release-notes/unreleased/1931.deprecation.rst

@@ -0,0 +1,12 @@
+The ``channel_strategy`` parameter has been deprecated.
+The Q-CTRL Performance Management strategy will be removed on October 18th, 2024. 
+To continue using Q-CTRL in your workflow, please explore the following options:
+
+- If your organization has an existing IBM Quantum Premium Plan instance: migrate to 
+the Q-CTRL Performance Management Function, found in the 
+`Qiskit Functions Catalog <https://quantum.ibm.com/functions>`__.
+
+- To continue using Qiskit Runtime with IBM Cloud: migrate to Q-CTRL Fire Opal, 
+the same performance management product accessible directly through Q-CTRL. 
+You can `connect your IBM Cloud API key and Qiskit Runtime CRN <https://docs.q-ctrl.com/fire-opal/discover/hardware-providers/how-to-authenticate-with-ibm-credentials>`__
+to Fire Opal.