chemistry/h2_qpe.ipynb

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    "## _*H2 ground state energy computation using Quantum Phase Estimation*_\n",
    "\n",
    "This notebook demonstrates using QISKit ACQUA Chemistry to compute ground state energy of the Hydrogen (H2) molecule using QPE (Quantum Phase Estimation) algorithm. It is compared to the same energy as computed by the ExactEigensolver\n",
    "\n",
    "This notebook populates a dictionary, that is a progammatic representation of an input file, in order to drive the qiskit_acqua_chemistry stack. Such a dictionary can be manipulated programmatically. An sibling notebook `h2_iqpe` is also provided, which showcases how the ground state energies over a range of inter-atomic distances can be computed and then plotted as well.\n",
    "\n",
    "This notebook has been written to use the PYSCF chemistry driver. See the PYSCF chemistry driver readme if you need to install the external PySCF library that this driver requires."
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   "source": [
    "import numpy as np\n",
    "import pylab\n",
    "from qiskit_acqua_chemistry import ACQUAChemistry\n",
    "import time\n",
    "\n",
    "distance = 0.735\n",
    "molecule = 'H .0 .0 0; H .0 .0 {}'.format(distance)\n",
    "\n",
    "# Input dictionary to configure QISKit ACQUA Chemistry for the chemistry problem.\n",
    "acqua_chemistry_qpe_dict = {\n",
    "    'driver': {'name': 'PYSCF'},\n",
    "    'PYSCF': {\n",
    "        'atom': molecule, \n",
    "        'basis': 'sto3g'\n",
    "    },\n",
    "    'operator': {'name': 'hamiltonian', 'transformation': 'full', 'qubit_mapping': 'parity'},\n",
    "    'algorithm': {\n",
    "        'name': 'QPE',\n",
    "        'num_ancillae': 9,\n",
    "        'num_time_slices': 50,\n",
    "        'expansion_mode': 'suzuki',\n",
    "        'expansion_order': 2,\n",
    "    },\n",
    "    'initial_state': {'name': 'HartreeFock'},\n",
    "    'backend': {\n",
    "        'name': 'local_qasm_simulator',\n",
    "        'shots': 100,\n",
    "    }\n",
    "}\n",
    "\n",
    "acqua_chemistry_ees_dict = {\n",
    "    'driver': {'name': 'PYSCF'},\n",
    "    'PYSCF': {'atom': molecule, 'basis': 'sto3g'},\n",
    "    'operator': {'name': 'hamiltonian', 'transformation': 'full', 'qubit_mapping': 'parity'},\n",
    "    'algorithm': {\n",
    "        'name': 'ExactEigensolver',\n",
    "    },\n",
    "}"
   ]
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   "source": [
    "With the two algorithms configured, we can then run them and check the results, as follows."
   ]
  },
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   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "--- computation completed in 34.4662721157074 seconds ---\n"
     ]
    }
   ],
   "source": [
    "start_time = time.time()\n",
    "result_qpe = ACQUAChemistry().run(acqua_chemistry_qpe_dict)\n",
    "result_ees = ACQUAChemistry().run(acqua_chemistry_ees_dict)\n",
    "print(\"--- computation completed in %s seconds ---\" % (time.time() - start_time))"
   ]
  },
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   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
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    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The groundtruth total ground state energy is           -1.137306035753399.\n",
      "The total ground state energy as computed by QPE is    -1.1371678808769072.\n",
      "In comparison, the Hartree-Fock ground state energy is -1.1169989967540044.\n"
     ]
    }
   ],
   "source": [
    "print('The groundtruth total ground state energy is           {}.'.format(\n",
    "    result_ees['energy']\n",
    "))\n",
    "print('The total ground state energy as computed by QPE is    {}.'.format(\n",
    "    result_qpe['energy']\n",
    "))\n",
    "print('In comparison, the Hartree-Fock ground state energy is {}.'.format(\n",
    "    result_ees['hf_energy']\n",
    "))\n"
   ]
  }
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