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  {
   "cell_type": "markdown",
   "metadata": {
    "slideshow": {
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   "source": [
    "# Example 2: Toffoli Gate\n",
    "In the empty cells below, build the circuit shown on the Example 2 slide. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
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   "source": [
    "from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit\n",
    "from qiskit import Aer, execute\n",
    "from qiskit.tools.visualization import plot_histogram"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "outputs": [],
   "source": [
    "# Create quantum registers and classical registers\n",
    "# Create a circuit (qc) including those registers\n",
    "\n",
    "qin = QuantumRegister(2, 'in')\n",
    "qout = QuantumRegister(1, 'out')\n",
    "c = ClassicalRegister(1, 'c')\n",
    "qc = QuantumCircuit(qin,qout,c)\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "outputs": [],
   "source": [
    "# Add gates to the circuit\n",
    "# The Toffoli gate is called ccx (controlled-controlled-X) in Qiskit\n",
    "# Add a measurement to the output bit\n",
    "\n",
    "qc.h(qin[0])\n",
    "qc.h(qin[1])\n",
    "qc.ccx(qin[0], qin[1], qout[0])\n",
    "qc.measure(qout,c)\n",
    "\n"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "outputs": [],
   "source": [
    "qc.draw(output='mpl')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "slide"
    }
   },
   "outputs": [],
   "source": [
    "# Simulate and show results\n",
    "backend = Aer.get_backend('qasm_simulator')\n",
    "job = execute(qc, backend, shots=512)  # shots default = 1024\n",
    "result = job.result()\n",
    "print(result.get_counts())\n",
    "plot_histogram(result.get_counts())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {
    "slideshow": {
     "slide_type": "skip"
    }
   },
   "outputs": [],
   "source": []
  }
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