Implement suggestion from @nkanazawa1989

docs/guides/fractional-gates.ipynb

@@ -31,7 +31,13 @@
     "backend = service.backend('ibm_torino', use_fractional_gates=True)\n",
     "```\n",
     "\n",
-    "This code example demonstrates how to use fractional gates in the context of a workflow that simulates the dynamics of an Ising chain using fractional gates. The circuit duration is then compared against a backend that does not use fractional gates."
+    "This code example demonstrates how to use fractional gates in the context of a workflow that simulates the dynamics of an Ising chain using fractional gates. The circuit duration is then compared against a backend that does not use fractional gates.\n",
+    "\n",
+    "<Admonition title=\"Note about reported error rates\" type=\"note\">\n",
+    "  The error value reported in the `Target` of a backend with fractional gates enabled is just a copy of the non-fractional gate's counterpart (which may not be the same). This is because the reporting of error rates on the fractional gates is not yet supported.\n",
+    "\n",
+    "  However, since the gate time of fractional vs non-fractional gates are the same, it is a reasonable assumption that their error rates are comparable -- especially when the dominant source of error in a circuit is due to relaxation.\n",
+    "</Admonition>"
    ]
   },
   {