Save circuit as qasm string or file and reload later

Save circuit as qasm string or file and reload later.ipynb

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       "<pre style=\"word-wrap: normal;white-space: pre;background: #fff0;line-height: 1.1;font-family: &quot;Courier New&quot;,Courier,monospace\">        ┌────┐┌────────┐┌───────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(p) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└───────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ───────────────────────────────░──╫─┤M├──────\n",
       "                                       ░  ║ └╥┘┌─┐   \n",
       "   q_2: ───────────────────────────────░──╫──╫─┤M├───\n",
       "                                       ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ───────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                       ░  ║  ║  ║ └╥┘\n",
       "meas_0: ══════════════════════════════════╩══╬══╬══╬═\n",
       "                                             ║  ║  ║ \n",
       "meas_1: ═════════════════════════════════════╩══╬══╬═\n",
       "                                                ║  ║ \n",
       "meas_2: ════════════════════════════════════════╩══╬═\n",
       "                                                   ║ \n",
       "meas_3: ═══════════════════════════════════════════╩═\n",
       "                                                     </pre>"
      ],
      "text/plain": [
       "        ┌────┐┌────────┐┌───────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(p) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└───────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ───────────────────────────────░──╫─┤M├──────\n",
       "                                       ░  ║ └╥┘┌─┐   \n",
       "   q_2: ───────────────────────────────░──╫──╫─┤M├───\n",
       "                                       ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ───────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                       ░  ║  ║  ║ └╥┘\n",
       "meas_0: ══════════════════════════════════╩══╬══╬══╬═\n",
       "                                             ║  ║  ║ \n",
       "meas_1: ═════════════════════════════════════╩══╬══╬═\n",
       "                                                ║  ║ \n",
       "meas_2: ════════════════════════════════════════╩══╬═\n",
       "                                                   ║ \n",
       "meas_3: ═══════════════════════════════════════════╩═\n",
       "                                                     "
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# create a circuit\n",
    "from qiskit import QuantumCircuit\n",
    "from qiskit.circuit import Parameter\n",
    "import numpy as np\n",
    "\n",
    "p = Parameter('p')\n",
    "qc = QuantumCircuit(4)\n",
    "qc.sx(0)\n",
    "qc.rz(3*np.pi, 0)\n",
    "qc.rz(p,0)\n",
    "qc.x(0)\n",
    "qc.measure_all()\n",
    "qc.draw('text')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "3080415b-f9ef-406b-a44f-db2d27642058",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Traceback \u001b[1;36m(most recent call last)\u001b[0m:\n",
      "  Input \u001b[0;32mIn [2]\u001b[0m in \u001b[0;35m<cell line: 2>\u001b[0m\n",
      "    qc.qasm()\n",
      "\u001b[1;36m  File \u001b[1;32m/opt/conda/lib/python3.8/site-packages/qiskit/circuit/quantumcircuit.py:1673\u001b[1;36m in \u001b[1;35mqasm\u001b[1;36m\u001b[0m\n",
      "\u001b[1;33m    raise QasmError(\"Cannot represent circuits with unbound parameters in OpenQASM 2.\")\u001b[0m\n",
      "\u001b[1;31mQasmError\u001b[0m\u001b[1;31m:\u001b[0m Cannot represent circuits with unbound parameters in OpenQASM 2.\n",
      "\n",
      "Use %tb to get the full traceback.\n"
     ]
    },
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       "<a href=\"https://stackoverflow.com/search?q=QasmError: Cannot represent circuits with unbound parameters in OpenQASM 2.\" target='_blank'><button class='button iqx-button'>Search for solution online</button></a>\n"
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   "source": [
    "# OpenQASM 2 does not support unbound parameters\n",
    "qc.qasm()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "5f375d01-bfbf-4578-94ca-09d992ff409f",
   "metadata": {},
   "outputs": [
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     "data": {
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       "<pre style=\"word-wrap: normal;white-space: pre;background: #fff0;line-height: 1.1;font-family: &quot;Courier New&quot;,Courier,monospace\">        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        </pre>"
      ],
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       "        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        "
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# assign parameter values\n",
    "qc.assign_parameters({p: 3.14}, inplace=True)\n",
    "qc.draw('text')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "1c0c057e-2c8f-44c8-b621-c199303b3891",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "OPENQASM 2.0;\n",
      "include \"qelib1.inc\";\n",
      "qreg q[4];\n",
      "creg meas[4];\n",
      "sx q[0];\n",
      "rz(3*pi) q[0];\n",
      "rz(3.14) q[0];\n",
      "x q[0];\n",
      "barrier q[0],q[1],q[2],q[3];\n",
      "measure q[0] -> meas[0];\n",
      "measure q[1] -> meas[1];\n",
      "measure q[2] -> meas[2];\n",
      "measure q[3] -> meas[3];\n",
      "\n"
     ]
    }
   ],
   "source": [
    "# export qasm string to a variable\n",
    "qasm_string = qc.qasm()\n",
    "print(qasm_string)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "f7b3283e-c7cf-4027-b692-d1f5de854d69",
   "metadata": {},
   "outputs": [
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       "<pre style=\"word-wrap: normal;white-space: pre;background: #fff0;line-height: 1.1;font-family: &quot;Courier New&quot;,Courier,monospace\">        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        </pre>"
      ],
      "text/plain": [
       "        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        "
      ]
     },
     "execution_count": 5,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# load a quantum circuit from qasm string\n",
    "qc_from_string = QuantumCircuit.from_qasm_str(qasm_string)\n",
    "qc_from_string.draw('text')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "b458a058-a0d6-4dca-a37e-b42318ef2703",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# verify that the loaded circuit is the same as the original circuit\n",
    "qc == qc_from_string"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "0487d1fe-0b5b-4b5c-aafc-f60dd4e2ef0d",
   "metadata": {},
   "outputs": [],
   "source": [
    "# store qasm string into a file\n",
    "with open('qasm_file', 'w') as output_file:\n",
    "    output_file.write(qasm_string)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "3aff4122-52c5-4dea-86b8-94c900fbccea",
   "metadata": {},
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     "data": {
      "text/html": [
       "<pre style=\"word-wrap: normal;white-space: pre;background: #fff0;line-height: 1.1;font-family: &quot;Courier New&quot;,Courier,monospace\">        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        </pre>"
      ],
      "text/plain": [
       "        ┌────┐┌────────┐┌──────────┐┌───┐ ░ ┌─┐         \n",
       "   q_0: ┤ √X ├┤ Rz(3π) ├┤ Rz(3.14) ├┤ X ├─░─┤M├─────────\n",
       "        └────┘└────────┘└──────────┘└───┘ ░ └╥┘┌─┐      \n",
       "   q_1: ──────────────────────────────────░──╫─┤M├──────\n",
       "                                          ░  ║ └╥┘┌─┐   \n",
       "   q_2: ──────────────────────────────────░──╫──╫─┤M├───\n",
       "                                          ░  ║  ║ └╥┘┌─┐\n",
       "   q_3: ──────────────────────────────────░──╫──╫──╫─┤M├\n",
       "                                          ░  ║  ║  ║ └╥┘\n",
       "meas_0: ═════════════════════════════════════╩══╬══╬══╬═\n",
       "                                                ║  ║  ║ \n",
       "meas_1: ════════════════════════════════════════╩══╬══╬═\n",
       "                                                   ║  ║ \n",
       "meas_2: ═══════════════════════════════════════════╩══╬═\n",
       "                                                      ║ \n",
       "meas_3: ══════════════════════════════════════════════╩═\n",
       "                                                        "
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# load a quantum circuit from qasm file\n",
    "qc_from_file = QuantumCircuit.from_qasm_file('qasm_file')\n",
    "qc_from_file.draw('text')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 9,
   "id": "f4a09905-c95d-480e-a181-a1e8b9318148",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "True"
      ]
     },
     "execution_count": 9,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "# verify that the loaded circuit is the same as the original circuit\n",
    "qc == qc_from_file"
   ]
  }
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