Fix failure of qvm_stabilizer_example.ipynb with numpy-2.4.0 (#7813)

- Avoid conversion of a one-element numpy array to float which
  throws TypeError in numpy-2.4.0 (was a DeprecationWarning before).

- Also run notebook tests with `PIP_CONFIG_FILE=/dev/null` environment.
  Notebook tests run in a temporary virtual environment to simulate
  generic colab experience.  Here we make them more isolated from
  local pip settings.

---------

Co-authored-by: Michael Hucka <mhucka@google.com>

Author: pavoljuhas

dev_tools/notebooks/isolated_notebook_test.py

@@ -154,9 +154,10 @@ def _rewrite_and_run_notebook(notebook_path, cloned_env):
         check=False,
         cwd=notebook_env,
         capture_output=True,
-        # important to get rid of PYTHONPATH specifically, which contains
-        # the Cirq repo path due to check/pytest
-        env={},
+        # Important to get rid of PYTHONPATH specifically, which contains
+        # the Cirq repo path due to check/pytest.  Also isolate the execution
+        # from pip settings in local configuration files or environment.
+        env={'PIP_CONFIG_FILE': '/dev/null'},
     )
 
     if result.returncode != 0:

dev_tools/notebooks/notebook_test.py

@@ -73,7 +73,10 @@ def require_packages_not_changed() -> Iterator[None]:
 
 @pytest.fixture
 def env_with_temporary_pip_target() -> Iterator[dict[str, str]]:
-    """Setup system environment that tells pip to install packages to a temporary directory."""
+    """Set up system environment that tells pip to install packages to a temporary directory.
+
+    Also isolate the run from local pip settings in configuration files or environment.
+    """
     with tempfile.TemporaryDirectory(suffix='-notebook-site-packages') as tmpdirname:
         # Note: We need to append tmpdirname to the PYTHONPATH, because PYTHONPATH may
         # already point to the development sources of Cirq (as happens with check/pytest).
@@ -84,7 +87,12 @@ def env_with_temporary_pip_target() -> Iterator[dict[str, str]]:
             if 'PYTHONPATH' in os.environ
             else tmpdirname
         )
-        env = {**os.environ, 'PYTHONPATH': pythonpath, 'PIP_TARGET': tmpdirname}
+        env = {
+            **os.environ,
+            'PYTHONPATH': pythonpath,
+            'PIP_TARGET': tmpdirname,
+            'PIP_CONFIG_FILE': '/dev/null',
+        }
         yield env
 
 

docs/simulate/qvm_stabilizer_example.ipynb

@@ -110,6 +110,7 @@
     "    import qsimcirq\n",
     "\n",
     "# Other modules used in this colab\n",
+    "import numpy as np\n",
     "import matplotlib.pyplot as plt\n",
     "import time\n",
     "import random"
@@ -402,11 +403,9 @@
    },
    "outputs": [],
    "source": [
-    "meas_map = {qubit_map[measure_qubit]: sum(results.measurements['meas']) / repetitions}\n",
+    "meas_map = {qubit_map[measure_qubit]: np.mean(results.measurements['meas'])}\n",
     "\n",
-    "data_map = {\n",
-    "    qubit_map[dq]: sum(results.measurements[str(dq)[-1]]) / repetitions for dq in data_qubits\n",
-    "}\n",
+    "data_map = {qubit_map[dq]: np.mean(results.measurements[str(dq)[-1]]) for dq in data_qubits}\n",
     "\n",
     "heatmap = cirq.Heatmap({**meas_map, **data_map})\n",
     "heatmap.plot();"
@@ -555,11 +554,11 @@
     "# Set to view results from each repetition.\n",
     "repetition = 0  # @param {type:\"number\"}\n",
     "meas_map = {\n",
-    "    qubit_map[q]: results.measurements[str(q)][repetition] for q in grid_meas_qubits.values()\n",
+    "    qubit_map[q]: results.measurements[str(q)][repetition].item() for q in grid_meas_qubits.values()\n",
     "}\n",
     "\n",
     "data_map = {\n",
-    "    qubit_map[q]: results.measurements[str(q)][repetition] for q in grid_data_qubits.values()\n",
+    "    qubit_map[q]: results.measurements[str(q)][repetition].item() for q in grid_data_qubits.values()\n",
     "}\n",
     "\n",
     "heatmap = cirq.Heatmap({**meas_map, **data_map})\n",
@@ -623,11 +622,11 @@
     "# Set to view results from each repetition.\n",
     "repetition = 0  # @param {type:\"number\"}\n",
     "meas_map = {\n",
-    "    qubit_map[q]: results.measurements[str(q)][repetition] for q in grid_meas_qubits.values()\n",
+    "    qubit_map[q]: results.measurements[str(q)][repetition].item() for q in grid_meas_qubits.values()\n",
     "}\n",
     "\n",
     "data_map = {\n",
-    "    qubit_map[q]: results.measurements[str(q)][repetition] for q in grid_data_qubits.values()\n",
+    "    qubit_map[q]: results.measurements[str(q)][repetition].item() for q in grid_data_qubits.values()\n",
     "}\n",
     "\n",
     "heatmap = cirq.Heatmap({**meas_map, **data_map})\n",