Convert start.md to start.ipynb. (quantumlib#5176)

Converts `start.md` -> `start.ipyb`. This lets us run the code block and make the notebook runnable in colab by our users.

Author: MichaelBroughton

docs/start.ipynb

@@ -0,0 +1,144 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "gXXhctqjgXO7"
+   },
+   "source": [
+    "##### Copyright 2022 The Cirq Developers"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "cellView": "form",
+    "id": "z2RJVa8qgXou"
+   },
+   "outputs": [],
+   "source": [
+    "#@title Licensed under the Apache License, Version 2.0 (the \"License\");\n",
+    "# you may not use this file except in compliance with the License.\n",
+    "# You may obtain a copy of the License at\n",
+    "#\n",
+    "# https://www.apache.org/licenses/LICENSE-2.0\n",
+    "#\n",
+    "# Unless required by applicable law or agreed to in writing, software\n",
+    "# distributed under the License is distributed on an \"AS IS\" BASIS,\n",
+    "# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n",
+    "# See the License for the specific language governing permissions and\n",
+    "# limitations under the License."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "EQvWLKKRgZR9"
+   },
+   "source": [
+    "# Hello Qubit"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "EvZ_JecKga2p"
+   },
+   "source": [
+    "<table class=\"tfo-notebook-buttons\" align=\"left\">\n",
+    "  <td>\n",
+    "    <a target=\"_blank\" href=\"https://quantumai.google/cirq/start\"><img src=\"https://quantumai.google/site-assets/images/buttons/quantumai_logo_1x.png\" />View on QuantumAI</a>\n",
+    "  </td>\n",
+    "  <td>\n",
+    "    <a target=\"_blank\" href=\"https://colab.research.google.com/github/quantumlib/Cirq/blob/master/docs/start.ipynb\"><img src=\"https://quantumai.google/site-assets/images/buttons/colab_logo_1x.png\" />Run in Google Colab</a>\n",
+    "  </td>\n",
+    "  <td>\n",
+    "    <a target=\"_blank\" href=\"https://github.com/quantumlib/Cirq/blob/master/docs/start.ipynb\"><img src=\"https://quantumai.google/site-assets/images/buttons/github_logo_1x.png\" />View source on GitHub</a>\n",
+    "  </td>\n",
+    "  <td>\n",
+    "    <a href=\"https://storage.googleapis.com/tensorflow_docs/Cirq/docs/start.ipynb\"><img src=\"https://quantumai.google/site-assets/images/buttons/download_icon_1x.png\" />Download notebook</a>\n",
+    "  </td>\n",
+    "</table>"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "id": "bd9529db1c0b"
+   },
+   "outputs": [],
+   "source": [
+    "try:\n",
+    "    import cirq\n",
+    "except ImportError:\n",
+    "    print(\"installing cirq...\")\n",
+    "    !pip install --quiet cirq\n",
+    "    import cirq\n",
+    "    print(\"installed cirq.\")"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "id": "n4GQUN8MS7vt"
+   },
+   "outputs": [],
+   "source": [
+    "# Pick a qubit.\n",
+    "qubit = cirq.GridQubit(0, 0)\n",
+    "\n",
+    "# Create a circuit\n",
+    "circuit = cirq.Circuit(\n",
+    "    cirq.X(qubit)**0.5,  # Square root of NOT.\n",
+    "    cirq.measure(qubit, key='m')  # Measurement.\n",
+    ")\n",
+    "print(\"Circuit:\")\n",
+    "print(circuit)\n",
+    "\n",
+    "# Simulate the circuit several times.\n",
+    "simulator = cirq.Simulator()\n",
+    "result = simulator.run(circuit, repetitions=20)\n",
+    "print(\"Results:\")\n",
+    "print(result)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {
+    "id": "shNBShuQTFuu"
+   },
+   "source": [
+    "# Congratulations\n",
+    "You've just run your first Cirq program. If you would like to learn more about Quantum Computing, check out our [education page](/education). You can find more in depth tutorials [here](tutorials). The Full API reference for Cirq can be found [here]((/reference/python/cirq). If you are looking for vendor specific information that can be found on our vendor sub-pages:\n",
+    "\n",
+    "\n",
+    "  [Google Quantum Computing Service](tutorials/google/start.ipynb)\n",
+    "  \n",
+    "  [Alpine Quantum Technologies](tutorials/aqt/getting_started.ipynb)\n",
+    "  \n",
+    "  [Pasqal](tutorials/pasqal/getting_started.ipynb)\n",
+    "  \n",
+    "  [IonQ](tutorials/ionq/getting_started.ipynb)\n",
+    "  \n",
+    "  [Azure](tutorials/azure-quantum/getting_started_honeywell.ipynb)\n",
+    "  \n",
+    "  [Rigetti](tutorials/rigetti/getting_started.ipynb)"
+   ]
+  }
+ ],
+ "metadata": {
+  "colab": {
+   "name": "start.ipynb",
+   "toc_visible": true
+  },
+  "kernelspec": {
+   "display_name": "Python 3",
+   "name": "python3"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 0
+}