Update max_execution_time docstrings

qiskit_ibm_runtime/options/options.py

@@ -61,12 +61,16 @@ class Options:
             <https://qiskit.org/documentation/partners/qiskit_ibm_runtime>`_.
             for more information about the error mitigation methods used at each level.
 
-        max_execution_time: Maximum execution time in seconds. If
-            a job exceeds this time limit, it is forcibly cancelled. If ``None``, the
-            maximum execution time of the primitive is used.
-            This value must be in between 300 seconds and the
-            `system imposed maximum
-            <https://qiskit.org/documentation/partners/qiskit_ibm_runtime/faqs/max_execution_time.html>`_.
+        max_execution_time: Maximum execution time in seconds, which is based
+            on quantum time (not wall clock time). Quantum time is the time that
+            the QPU complex (including control software, control electronics, QPU, and so on)
+            is engaged in processing the job. If a job exceeds this time limit, it is forcibly cancelled.
+            Simulator jobs continue to use wall clock time because they do not have quantum time.
+
+            Refer to the
+            `Max execution time documentation
+            <https://docs.quantum-computing.ibm.com/run/max-execution-time#maximum-execution-time>`_.
+            for more information.
 
         transpilation: Transpilation options. See :class:`TranspilationOptions` for all
             available options.

qiskit_ibm_runtime/runtime_options.py

@@ -58,8 +58,12 @@ def __init__(
                 access to the target backend is randomly selected.
             job_tags: Tags to be assigned to the job. The tags can subsequently be used
                 as a filter in the :meth:`jobs()` function call.
-            max_execution_time: Maximum execution time in seconds. If
-                a job exceeds this time limit, it is forcibly cancelled.
+            max_execution_time: Maximum execution time in seconds, which is based
+                on quantum time (not wall clock time). Quantum time is the time that
+                the QPU complex (including control software, control electronics, QPU, and so on)
+                is engaged in processing the job. If a job exceeds this time limit, it is forcibly
+                cancelled. Simulator jobs continue to use wall clock time because they do not have
+                quantum time.
             session_time: Length of session in seconds.
         """
         self.backend = backend

releasenotes/notes/max-execution-time-definition-196cb6297693c0f2.yaml

@@ -0,0 +1,8 @@
+---
+fixes:
+  - |
+    The `max_execution_time` option is now based on quantum time instead of wall clock time. 
+    Quantum time is the time that the QPU complex 
+    (including control software, control electronics, QPU, and so on) 
+    is engaged in processing the job. If a job exceeds this time limit, it is forcibly cancelled.
+    Simulator jobs continue to use wall clock time because they do not have quantum time.