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   "cell_type": "markdown",
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   "source": [
    "# Scale SQD chemistry workflows with Dice solver\n",
    "\n",
    "For information on how to install and use ``qiskit-addon-dice-solver``, [visit the docs](https://qiskit.github.io/qiskit-addon-dice-solver/).\n",
    "\n",
    "For more details on the SQD code used in this example, check out [tutorial 1](https://qiskit.github.io/qiskit-addon-sqd/tutorials/01_chemistry_hamiltonian.html)."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "baf7d074-4443-4695-875e-65f7fb8cef25",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "converged SCF energy = -108.835236570774\n",
      "CASCI E = -109.046671778080  E(CI) = -32.8155692383187  S^2 = 0.0000000\n"
     ]
    }
   ],
   "source": [
    "import numpy as np\n",
    "import pyscf\n",
    "import pyscf.cc\n",
    "import pyscf.mcscf\n",
    "from qiskit_addon_dice_solver import solve_sci_batch\n",
    "from qiskit_addon_sqd.counts import generate_bit_array_uniform\n",
    "from qiskit_addon_sqd.fermion import diagonalize_fermionic_hamiltonian\n",
    "\n",
    "# Specify molecule properties\n",
    "num_orbitals = 16\n",
    "num_elec_a = num_elec_b = 5\n",
    "spin_sq = 0\n",
    "\n",
    "# Build N2 molecule\n",
    "mol = pyscf.gto.Mole()\n",
    "mol.build(\n",
    "    atom=[[\"N\", (0, 0, 0)], [\"N\", (1.0, 0, 0)]],\n",
    "    basis=\"6-31g\",\n",
    "    symmetry=\"Dooh\",\n",
    ")\n",
    "\n",
    "# Define active space\n",
    "n_frozen = 2\n",
    "active_space = range(n_frozen, mol.nao_nr())\n",
    "\n",
    "# Get molecular integrals\n",
    "scf = pyscf.scf.RHF(mol).run()\n",
    "num_orbitals = len(active_space)\n",
    "n_electrons = int(sum(scf.mo_occ[active_space]))\n",
    "num_elec_a = (n_electrons + mol.spin) // 2\n",
    "num_elec_b = (n_electrons - mol.spin) // 2\n",
    "cas = pyscf.mcscf.CASCI(scf, num_orbitals, (num_elec_a, num_elec_b))\n",
    "mo = cas.sort_mo(active_space, base=0)\n",
    "hcore, nuclear_repulsion_energy = cas.get_h1cas(mo)\n",
    "eri = pyscf.ao2mo.restore(1, cas.get_h2cas(mo), num_orbitals)\n",
    "\n",
    "# Compute exact energy\n",
    "exact_energy = cas.run().e_tot\n",
    "\n",
    "# Create a seed to control randomness throughout this workflow\n",
    "rng = np.random.default_rng(24)\n",
    "\n",
    "\n",
    "# Generate random samples\n",
    "bit_array = generate_bit_array_uniform(10_000, num_orbitals * 2, rand_seed=rng)\n",
    "\n",
    "# Run SQD\n",
    "result = diagonalize_fermionic_hamiltonian(\n",
    "    hcore,\n",
    "    eri,\n",
    "    bit_array,\n",
    "    samples_per_batch=300,\n",
    "    norb=num_orbitals,\n",
    "    nelec=(num_elec_a, num_elec_b),\n",
    "    num_batches=5,\n",
    "    max_iterations=5,\n",
    "    sci_solver=solve_sci_batch,\n",
    "    symmetrize_spin=True,\n",
    "    seed=rng,\n",
    ")"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "99709a88-f9ec-4dbc-a561-e682f90aa4c5",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Exact energy: -109.04667177808028\n",
      "Estimated energy: -109.03402667558743\n"
     ]
    }
   ],
   "source": [
    "print(f\"Exact energy: {exact_energy}\")\n",
    "print(f\"Estimated energy: {result.energy + nuclear_repulsion_energy}\")"
   ]
  }
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