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      "source": [
        "# Analyzing the output of a run\n",
        "\n",
        "The aim of this notebook is to analyze in more detail the output of the submission of a job.\n",
        "\n",
        "We will be focussing on the following simple circuit:"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
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      "source": [
        "from qat.lang.AQASM import Program, H, CNOT, Y\n",
        "\n",
        "prog = Program()\n",
        "reg = prog.qalloc(2)  # quantum register\n",
        "creg = prog.calloc(3)  # classical register\n",
        "prog.apply(H, reg[0])  \n",
        "prog.apply(CNOT, reg)\n",
        "prog.measure(reg[1], creg[1])\n",
        "prog.cc_apply(creg[1], Y, reg[0])\n",
        "prog.measure(reg[0], creg[0])\n",
        "prog.logic(creg[2], ~ creg[1])\n",
        "prog.reset(reg[1])\n",
        "circ = prog.to_circ()"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Let us examine the evolution of the quantum state step-by-step:\n",
        "- we start in state $|00\\rangle$ (bit order: q0 q1). The classical bits are in state \"000\" (bit order: b0 b1 b2).\n",
        "- after the H and CNOT gates, we are in state $(|00\\rangle + |11 \\rangle)/\\sqrt{2}$, the classical register is unchanged\n",
        "- the first measure on qubit #1 projects the state to $|00\\rangle$ or $|11\\rangle$. The classical register is thus either in state \"000\" or \"010\"\n",
        "- the classically controlled gate $Y$ is applied only if the second cbit has value 1, in which case we get the state $-i|01\\rangle$. Otherwise, we keep the state $|00\\rangle$.\n",
        "- the second measure gives 0 in both possible cases ($-i|01\\rangle$ and $|00\\rangle$)\n",
        "- the logic gate will give rise to the classical register state \"010\" or \"001\"\n",
        "- the reset turns the classical register to \"010\" if the state was $-i|01\\rangle$ (and yields final state $|-i|00\\rangle$), or \"001\" if the state was $|00\\rangle$ (and keeps the quantum state unchanged, $|00\\rangle$.\n",
        "\n",
        "In summary, we expect two possible intermediate measurement results:\n",
        "- 0, 0, 0 (first two measures and reset), yielding final classical register \"001\" and quantum state $|00\\rangle$\n",
        "- 1, 0, 1 (first two measures and reset), yielding final classical register \"010\" and quantum state $-i|00\\rangle$\n",
        "\n",
        "We can now check that this is indeed what happens when executing this circuit on the QLM:"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {},
      "outputs": [],
      "source": [
        "from qat.qpus import PyLinalg\n",
        "qpu = PyLinalg()\n",
        "\n",
        "# we execute the circuit 3 times\n",
        "for _ in range(3):\n",
        "    res = qpu.submit(circ.to_job(nbshots=1, aggregate_data=False))\n",
        "    print(\"====================\")\n",
        "    print(\"  ---- 3 intermediate measurements (including reset)---------------\")\n",
        "    #print(res)\n",
        "    for meas_res in res.raw_data[0].intermediate_measurements:\n",
        "        print(\"   measure = %s (position = %s)\"%(meas_res.cbits, meas_res.gate_pos))\n",
        "    print(\"  ---- final state of the quantum and classical register ------\")\n",
        "    print(\"   quantum register = %s (bit order q0 q1)\"% res.raw_data[0].state)\n",
        " "
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "We can see that ``res.raw_data`` is a list containing a objects (of the type ``Sample``) containing several pieces of information:\n",
        "\n",
        "- its field ``intermediate_measurements`` contains a list of measurement results (type ``MeasurementResult``), which in particular contain the value of the measured bit(s) (field ``cbits``) and the index of the measurement/reset gate in the circuit (field ``gate_pos``)\n",
        "\n",
        "- its field ``state`` contains the final quantum state *after a measurement, in the computational basis, of all the qubits at the end of the circuit* (one can also decide to measure only a subset of qubits at the end of the circuit, by specifying the parameter ``qubits`` in the call to ``to_job``)"
      ]
    }
  ],
  "metadata": {
    "authors": [
      "Simon Martiel"
    ],
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