put commuting observables in the same PUB

docs/guides/primitive-input-output.ipynb

@@ -62,6 +62,9 @@
     "For the Estimator primitive, the format of the PUB should contain at most four values:\n",
     "- A single `QuantumCircuit`, which may contain one or more [`Parameter`](/docs/api/qiskit/qiskit.circuit.Parameter) objects\n",
     "- A list of one or more observables, which specify the expectation values to estimate, arranged into an array (for example, a single observable represented as a 0-d array, a list of observables as a 1-d array, and so on). The data can be in any one of the `ObservablesArrayLike` format such as `Pauli`, `SparsePauliOp`, `PauliList`, or `str`.\n",
+    "   <Admonition type=\"note\">\n",
+    "   If you have two commuting observables in different PUBs but with the same circuit, they will not be estimated using the same measurement. Each PUB represents a different basis for measurement, and therefore, separate measurements are required for each PUB. To ensure that commuting observables are estimated using the same measurement, they must be grouped within the same PUB.\n",
+    "   </Admonition>\n",
     "- A collection of parameter values to bind the circuit against. This can be specified as a single array-like object where the last index is over circuit `Parameter` objects, or omitted (or equivalently, set to `None`) if the circuit has no `Parameter` objects.\n",
     "- (Optionally) a target precision for expectation values to estimate\n",
     "\n",