Fix #7510: remove outdated notebook about XEB (#7519)

Per @eliottrosenberg's report in issue #7510, the notebook at
[quantumai.google/cirq/noise/qcvv/xeb_calibration_example](https://quantumai.google/cirq/noise/qcvv/xeb_calibration_example)
is out of date and should be deleted.

---------

Co-authored-by: Pavol Juhas <[email protected]>

Author: mhucka

dev_tools/notebooks/isolated_notebook_test.py

@@ -63,7 +63,6 @@
     # tutorials that use QCS and arent skipped due to one or more cleared output cells
     'docs/tutorials/google/identifying_hardware_changes.ipynb',
     'docs/tutorials/google/echoes.ipynb',
-    'docs/noise/qcvv/xeb_calibration_example.ipynb',
     # temporary: need to fix QVM metrics and device spec
     'docs/tutorials/google/spin_echoes.ipynb',
     'docs/tutorials/google/visualizing_calibration_metrics.ipynb',

dev_tools/notebooks/notebook_test.py

@@ -44,7 +44,6 @@
     # tutorials that use QCS and arent skipped due to one or more cleared output cells
     'docs/tutorials/google/identifying_hardware_changes.ipynb',
     'docs/tutorials/google/echoes.ipynb',
-    'docs/noise/qcvv/xeb_calibration_example.ipynb',
     # temporary: need to fix QVM metrics and device spec
     'docs/tutorials/google/spin_echoes.ipynb',
     'docs/tutorials/google/visualizing_calibration_metrics.ipynb',

docs/_book.yaml

@@ -173,8 +173,6 @@ upper_tabs:
         path: /cirq/noise/qcvv/coherent_vs_incoherent_xeb
       - title: "Parallel XEB"
         path: /cirq/noise/qcvv/parallel_xeb
-      - title: "XEB calibration: Example and Benchmark"
-        path: /cirq/noise/qcvv/xeb_calibration_example
     ####  VISUALIZING NOISE  ####
       - heading: "Visualizing noise"
       - title: "Heatmaps"

docs/google/best_practices.ipynb

@@ -517,7 +517,7 @@
     "\n",
     "For more on calibration and detailed instructions on how to perform these procedures, see the following tutorials:\n",
     "\n",
-    "* [XEB calibration example](../noise/qcvv/xeb_calibration_example.ipynb)\n",
+    "* [XEB calibration theory](../noise/qcvv/xeb_theory.ipynb)\n",
     "* [Floquet calibration](https://www.youtube.com/watch?v=hYDWOz1r2Ys&t=243s)"
    ]
   }

docs/noise/qcvv/xeb_calibration_example.ipynb

@@ -322,7 +322,7 @@
     "id": "9sY5bMW9f-Oo"
    },
    "source": [
-    "Note: The parallel XEB errors are scaled in pxeb_results. This is because the collected fidelities are the estimated depolarization fidelities, not the Pauli error metrics available from the calibration data. See the [XEB Theory](../../noise/qcvv/xeb_theory.ipynb#fidelities) tutorial for an explanation why, and [Calibration Metrics](../../google/calibration.md) for more information on the difference between these values."
+    "Note: The parallel XEB errors are scaled in pxeb_results. This is because the collected fidelities are the estimated depolarization fidelities, not the Pauli error metrics available from the calibration data. See the [XEB Theory](../../noise/qcvv/xeb_theory.ipynb#fidelities) tutorial for an explanation of why."
    ]
   },
   {
@@ -525,7 +525,7 @@
     "\n",
     "*    You need to map your actual circuit's logical qubits to your selected hardware qubits. This is in general a difficult problem, and the best solution can depend on the specific structure of the circuit to be run. Take a look at the [Qubit Picking with Loschmidt Echoes](./echoes.ipynb) tutorial, which estimates the error rates of gates for your specific circuit. Also, consider [Best Practices#qubit picking](../../google/best_practices.ipynb#qubit_picking) for additional advice on this.\n",
     "*    The [Optimization, Alignment, and Spin Echoes](./spin_echoes.ipynb) tutorial provides resources on how you can improve the reliability of your circuit by: optimizing away redundant or low-impact gates, aligning gates into moments with others of the same type, and preventing decay on idle qubits with by adding spin echoes.\n",
-    "*    Other than for qubit picking, you should also use calibration for error compensation. The [Coherent vs incoherent noise with XEB](../../noise/qcvv/coherent_vs_incoherent_xeb.ipynb), [XEB Calibration Example](../../noise/qcvv/xeb_calibration_example.ipynb), [Parallel XEB](../../noise/qcvv/parallel_xeb.ipynb) and [Isolated XEB](../../noise/qcvv/isolated_xeb.ipynb) tutorials demonstrate how to run a classical optimizer on collected two-qubit gate characterization data, identity the true unitary matrix implemented by each gate, and add [Virtual Pauli Z gates](../../hardware/devices.ipynb) to compensate for the identified error, improving the reliability of your circuit.\n",
+    "*    Other than for qubit picking, you should also use calibration for error compensation. The [Coherent vs incoherent noise with XEB](../../noise/qcvv/coherent_vs_incoherent_xeb.ipynb), [Parallel XEB](../../noise/qcvv/parallel_xeb.ipynb) and [Isolated XEB](../../noise/qcvv/isolated_xeb.ipynb) tutorials demonstrate how to run a classical optimizer on collected two-qubit gate characterization data, identity the true unitary matrix implemented by each gate, and add [Virtual Pauli Z gates](../../hardware/devices.ipynb) to compensate for the identified error, improving the reliability of your circuit.\n",
     "*    You are also free to use the characterization data to improve the performance of large batches of experiment circuits. In this case you'd want to prepare your characterization ahead of running all your circuits, and use the data to compensate each circuit, right before running them."
    ]
   }